Abstract: Existence of cancer stem cells (CSCs) is still hypothetical and their practical marker is not available yet in lung cancer. To verify the possible existence of CSCs and to find their markers in lung cancer, we compared the p16/Rb and telomerase status in 83 lung cancer tissues and 15 lung cancer cell lines, since inactivation of p16/Rb pathway is considered to be a prerequisite for normal somatic cells to become immortal cancer cells. We found that 7 of 14 adenocarcinoma, but not squamous cell carcinoma, tissues with high telomerase activity and 3 adenocarcinoma cell lines likely had intact p16/Rb. Such cell lines showed higher colony formation capacity in soft agar compared with inactivated ones with similar growth rate. Moreover, cisplatin-resistant cell line PC9/CDDP with intact p16/Rb, but not PC14/CDDP with its inactivation, increased the colony formation capacity compared with the parent cells. Since CSCs are considered to be resistant to conventional anticancer drugs, they could have been concentrated as long as CSCs existed. We propose that half of immortal lung adenocarcinomas are derived from innately telomerase-positive stem cells, which might be the origin of CSCs, and that high telomerase activity with intact p16/Rb could be a marker of stem cell origin.
Abstract: Vascular endothelial growth factor (Vegf) was previously shown to be expressed specifically in the condylar cartilage of temporomandibular joint-osteoarthritis (TMJ-OA) model rats. Here we demonstrate for the first time that hypoxia-inducible factor-1alpha (Hif-1alpha) is activated in mature chondrocytes of temporomandibular joint-osteoarthritis (TMJ-OA) model rat by mechanical overload, and that activated Hif-1 in chondrocytes can induce osteoclastogenesis via repression of osteoprotegerin (Opg) expression. In rat TMJs, degeneration of the condylar cartilage became prominent in proportion to the duration of overloading. Hif-1alpha expression was observed specifically in mature and hypertrophic chondrocytes, and Hif-1alpha-positivity, level of Vegf expression, and tartrate-resistant acid phosphatase (TRAP)-positive cell numbers all increased in the same manner. When ATDC5 cells induced differentiation by insulin were cultured under hypoxia, Hif-1alpha induction was observed in mature stage, but not in immature stage. Inductions of Hif-1-target genes showed a similar expression pattern. In addition, expression of Opg decreased in hypoxia, and Hif-1alpha played a role, in part, in its regulation.
Abstract: BACKGROUND: Epithelial membrane protein 3 (EMP3), was recently reported to be a tumor suppressor gene for several solid tumors, and is drawing attention as a novel prognostic marker, since its expression level or hypermethylation of the promoter region is associated with clinical prognosis in neuroblastoma and esophageal cancer. However, some controversial data were also observed in gliomas and breast cancers, and there seems to be more than deletion/hypermethylation to its silencing mechanisms. OBJECTIVE: To clarify the discrepancies in the biological behavior of EMP3 among the different organ-derived malignancies or histologies and validate the potential of EMP3 as a tumor suppressor for solid tumors. METHODS: Literature dealing with EMP3 in the PubMed database was reviewed. RESULTS/CONCLUSIONS: EMP3 is a novel tumor suppressor gene in some kinds of malignancies, but not all, at the step of cellular immortalization rather than carcinogenesis. It may become a potent prognostic marker and a therapeutic target in such tumors.
Abstract: EMP3, epithelial membrane protein 3, was recently reported to be a tumor suppressor gene in neuroblastomas and gliomas. We found that EMP3 was commonly repressed in esophageal squamous cell carcinoma (ESCC) cell lines by oligonucleotide microarrays. Its overexpression in ESCC cell lines caused growth inhibition with morphological changes and TERT repression. In addition to promoter hypermethylation, TSA caused repression of EMP3, indicating the involvement of histone deacetylase-regulated repressors. The post-recurrent survival after radical surgery was poorer in ESCC patients with lower EMP3 expression. We propose that EMP3 may be a tumor suppressor gene at the late step of ESCC carcinogenesis.
Abstract: Prior laboratory prediction of individual drug response is of key importance in esophageal squamous cell carcinoma (ESCC), because of the extremely narrow therapeutic index of chemotherapy. However, very few critical markers have been validated to date for ESCC. We previously demonstrated that simultaneous performance of two different types of comprehensive gene expression analysis might provide a way to identify potent marker genes for drug sensitivity from the expression-sensitivity correlation analysis alone, but the screening method appeared not to be always effective. Therefore, we attempted to identify novel potent marker genes using a new statistical analysis of oligonucleotide microarray expression data, based on a two-dimensional mixed normal model, and selected 3 and 7 novel candidates for 5-fluorouracil (5-FU) and cis-platinum (CDDP), respectively. Interferon induced transmembrane protein 1 (IFITM1) gene alone, being suggested as a key gene of Wnt pathway, was commonly selected in both screening methods. The transfection analyses and siRNA-mediated knock-down experiments revealed that expression of IFITM1 closely related to cellular sensitivity to CDDP. Considering the fact that drug sensitivity is determined by multiple genes, we established the best linear model using quantified expression data of a set of all the selected marker genes including IFITM1, which converted the quantified expression data of ESCC cell lines into an IC50 value of each drug. In the same way, using the representative genes selected in vitro, we developed highly predictive formulae for disease-free survival (DFS) of the CDDP/5-FU combination after curative operation in esophageal cancer patients (R=0.917). A two-dimensional mixed normal model can be a powerful tool to identify novel drug-response determinants, and the IFITM1 gene selected by the statistical method a novel critical biomarker of CDDP response in ESCC.
Abstract: Tumor hypoxia has been reported to cause a functional loss in DNA mismatch repair (MMR) system as a result of downregulation of MMR genes, although the precise molecular mechanisms remain unclear. In this study, we focused on the downregulation of a key MMR gene, MLH1, and demonstrated that hypoxia-inducible transcription repressors, differentiated embryo chondrocytes (DEC1 and 2), participated in its transcriptional regulation via their bindings to E-box-like motif(s) in MLH1 promoter region. In all cancer cell lines examined, hypoxia increased expression of DEC1 and 2, known as hypoxia-inducible genes, but decreased MLH1 expression in an exposure time-dependent manner at both the mRNA and protein levels. Co-transfection reporter assay revealed that DEC1 and, to greater extent, DEC2 as well as hypoxia-repressed MLH1 promoter activity. We further found that the action was remarkably inhibited by trichostatin A, and identified a possible DEC-response element in the MLH1 promoter. In vitro electrophoretic gel mobility shift and chromatin immunoprecipitation assays demonstrated that DEC1 or 2 directly bounds to the suggested element, and transient transfection assay revealed that overexpression of DEC2 repressed endogenous MLH1 expression in the cells. Hypoxia-induced DEC may impair MMR function through repression of MLH1 expression, possibly via the histone deacethylase-mediated mechanism in cancer cells.
Abstract: Regulation mechanism of lung fibroblast proliferation remains unknown. To elucidate the key molecules in it, the authors here established mortal and immortal nontransformed lung fibroblast cell line/strains with elongated life span by telomerase reverse transcriptase gene transfection. Comparing the expression profiles of them, 51 genes were explored to be the candidates responsible for regulation of cellular proliferation of lung fibroblasts. This set of fibrobrast strains of same origin with different proliferative capacities may become useful model cells for research on lung fibroblast growth regulation and the candidate genes explored in this study may provide biomarkers or therapeutic targets of pulmonary fibrosis.
Abstract: BACKGROUND: The conversion of CPT-11 to its active form, SN-38, by carboxylesterases (CESs) is a critical event in CPT-11-induced cytotoxicity. Among the CESs, CES1 and CES2 probably play a major role in the metabolism, but the functional significance and molecular basis of CES1 on CPT-11 response remain unclear. METHODS AND RESULTS: We investigated CES1A1 (AB119997) and CES1A2 (AB187225), whose coding sequences were recently registered in GenBank, for CPT-11-induced cytotoxicity, anticipating novel biomarkers of CPT-11 response. Their coding sequences showed high homology, with only four amino acid differences in the N-terminal region, but our sequencing study of the 5' regions revealed that CES1A1 and CES1A2 had distinctive consensus sequences for transcription factors in the regions, implying differences in transcriptional regulation of the genes. We also identified three isoforms of CES1A1 gene--CES1A1a, CES1A1b and CES1A1c--and developed a detection method for CES1A1 and CES1A2 types of mRNA expression. Interestingly, CES1A2 type of mRNA was found to be expressed from both CES1A1b and CES1A1c isoforms and CES1A2, the promoter activity of the former was higher than that of the original CES1A2 gene. Finally, CES1A2 type of mRNA expression correlated with CPT-11 sensitivities of cancer cells. CONCLUSION: We demonstrated novel sequence structures and a functional role of CES1A genes in CPT-11 responses. We believe that our novel findings will be of key importance in developing a really useful prediction method for CPT-11 chemosensitivity.
Abstract: In this study, we demonstrate an important role of activation of the hypoxia-inducible factor-1 (HIF-1) pathway in endometrial carcinogenesis and tumor phenotype development of endometrial carcinoma, and suggest a unique role of the HIF-1-target gene, differentiated embryo chondrocyte 2 (DEC2), in carcinogenesis. Hypoxia caused an increase in HIF-1alpha protein expression in 4 endometrial carcinoma cell lines. The expressions of its 5 target genes - DEC1, DEC2, carbonic anhydrase-9 (CA9), vascular endothelial growth factor (VEGF), and solute carrier family 2, member 1 (SLC2A1) - also reactively increased in most of the cell lines, except for DEC2 in the SNG-M cells. The expression levels of DEC2, CA9, and SLC2A1 were significantly higher in the 4 atypical hyperplasia tissues and 82 endometrial carcinomas compared with those in the 21 normal endometria. Clinicopathological analyses of carcinoma patients revealed a significant correlation of the VEGF and SLC2A1 expression with the status of lymph-vascular involvement and lymph node metastasis. The expression levels of CA9 and VEGF were significantly higher in the tumors of post- as opposed to pre-menopausal patients. The SLC2A1 expression was also related to the FIGO stage, but the DEC2 expression was inversely related to the FIGO grade. The activation of the HIF-1 pathway could be related to endometrial carcinogenesis, and the component, DEC2, could have different expression-regulatory mechanisms and unique roles in carcinogenesis.
Abstract: The prognosis of lung cancer remains poor, and biological heterogeneity is largely responsible, especially in adenocarcinoma. We previously found that only one third of non-small cell lung cancer (NSCLC) but most small cell lung cancer (SCLC) tissues have strong telomerase activity, representing the difference in the history of multiple clonal selections. To reveal the genes differentially involved in telomerase activation mechanisms, we analyzed the relationship between common genetic aberrations and telomerase activity in 83 lung cancer tissues. We found that half (7 of 14) of lung adenocarcinomas with high telomerase activity showed neither TP53 nor RB1 deletion, while all squamous cell carcinomas and SCLCs with high telomerase activity showed loss of heterozygosity of at least one, if not both, of these suppressor oncogenes, indicating that these genetic aberrations are not required in activation of telomerase in a unique subset of adenocarcinoma. Furthermore, whereas the aberrations in TP53, RB1 and 1p34-pter were mutually related in 42 adenocarcinoma tissues, EGFR aberrations showed no relationship to either of them. These findings indicate that EGFR activating aberrations occur independently of other common genetic aberrations or telomerase activation mechanisms in lung adenocarcinoma, and that the distinct subset of lung adenocarcinoma with high telomerase activity without any common genetic aberrations may possibly have arisen from a telomerase-positive or telomerase-competent normal cell.
Abstract: Paclitaxel (PTX) is an anticancer drug that is effective against a wide range of solid tumors. The effect of PTX on two human lung cancer cell lines, PC14PE6 and NCI-H441 cells, was examined in an orthotopically transplanted animal model with an in vivo imaging devise. Although PTX effectively suppressed tumor growth and improved survival rate in NCI-H441, it did not influence these in PC14PE6. In vitro experiments confirmed that PC14PE6 cells are resistant to PTX under normoxic conditions and that both cell lines were resistant to PTX under hypoxic conditions. It was found that the expression level of endogenous hypoxia inducible factor (HIF)-1alpha in PC14PE6 is much higher than that in NCI-H441 cells under normoxic conditions. Furthermore, sensitivity to PTX in these cell lines was reversed when HIF-1alpha expression was decreased by siRNA specific to HIF-1alpha in PC14PE6 and increased by overexpression of the exogenous HIF-1alpha gene in NCI-H441. These results suggest that HIF-1 influences the PTX sensitivity of these cells. The authors further examined beta-tubulin, a target molecule of PTX, with western blotting and immunohistochemical analysis in these cells. The expression level of beta-tubulin was comparable in these cells under both normoxic and hypoxic conditions while the distribution of beta-tubulin and cell morphology were changed according to HIF-1alpha expression levels, suggesting that HIF-1 influences the conformation and dynamics of microtubules. These data support the potential development of HIF-1 targeted approaches in combination with PTX, where drug resistance tends to contribute to treatment failure.
Abstract: Esophageal cancer is a highly lethal disease and the optimal therapy remains unclear. Since adjuvant chemotherapy gives a better chance of survival, we attempted to develop a chemosensitivity prediction model to improve individual responses to therapy. Comprehensive gene expression analyses (cDNA and oligonucleotide microarrays) and MTT assay of 8 drugs in 20 KYSE squamous cell carcinoma cell lines were performed to distinguish candidate marker genes whose expression levels reproducibly correlated with cellular drug sensitivities. After confirmation with real-time RT-PCR, we performed multiple regression analyses to develop drug-sensitivity prediction formulae using the quantified expression data of selected marker genes. Using the same sets of genes, we also constructed prediction models for individual clinical responses to 5-FU-based chemotherapy using 18 cases. We selected 5 better marker genes, known as drug sensitivity determinants, identified 9 novel predictive genes for 4 of 8 anticancer drugs [5-FU, CDDP, DOX, and CPT-11 (SN-38)], and developed highly predictive formulae of in vitro sensitivities to the 4 drugs and clinical responses to 5-FU-based adjuvant chemotherapies in terms of overall and disease-free survivals. Our selected genes are likely to be effective drug-sensitivity markers and formulae using the 9 novel genes would provide advantages in prediction.
Abstract: We attempted to identify potent marker genes using a new statistical analysis and developed a prediction system for individual response to platinum/paclitaxel combination chemotherapy in ovarian cancer patients based on the hypothesis that expression analysis of a set of the key drug sensitivity genes for platinum and paclitaxel could allow us to predict therapeutic response to the combination. From 10 human ovarian cancer cell lines, genes correlative in the expression levels with cytotoxicities of cisplatin (CDDP) and paclitaxel were chosen. We first selected five reliable prediction markers for the two drugs from 22 genes already known as sensitivity determinants and then identified another 8 novel genes through a two-dimensional mixed normal model using oligomicroarray expression data. Using expression data of genes quantified by real-time reverse transcription-PCR, we fixed the best linear model, which converted the quantified expression data into an IC(50) of each drug. Multiple regression analysis of the selected genes yielded three prediction formulae for in vitro activity of CDDP and paclitaxel. In the same way, using the same genes selected in vitro, we then attempted to develop prediction formulae for progression-free survival to the platinum/paclitaxel combination. We therefore constructed possible formulae using different sets of 13 selected marker genes (5 known and 8 novel genes): Utility confirmation analyses using another nine test samples seemed to show that the formulae using a set of 8 novel marker genes alone could accurately predict progression-free survival (r = 0.683; P = 0.042).
Abstract: Dihydropyrimidine dehydrogenase is the most extensively investigated predictive marker for individual response to 5-fluorouracil. Clinical responses to the anticancer agent, along with various reports, have clearly shown that dihydropyrimidine dehydrogenase activity is closely correlated to its mRNA levels, but the regulatory mechanisms of its expression have remained unclear. We attempted to clarify the mechanisms and found that activator protein (AP-1) is probably one of the key factors in the transcriptional regulation of DPYD in cancer cells, and that phorbol 12-myristate 13-acetate (PMA) plus ionomycin treatment enhances transcription of DPYD via AP-1 activation. In this study, we characterized our previously subcloned 5' region of human DPYD, an approximately 3.0-kb fragment (accession no. AB162145). Luciferase reporter assay showed that the clone showed strong promoter activities in 293T and HSC42 cells, and comparative analysis using 5' deletion mutants suggested the existence of several positive and negative regulatory regions, including putative binding sites for AP-1, SP-1, and nuclear factor-kappaB. PMA/ionomycin treatment increased the mRNA level of DPYD in HSC42 cells, and electrophoretic gel mobility shift assay showed that the complex on the putative AP-1 binding site was drastically induced by PMA/ionomycin treatment. The complexes formed were competed out by preincubation with the cold-consensus AP-1 binding site, and the DNA binding complex formed on the site contained c-Jun and c-Fos, which are components of AP-1 transcription factor. We further identified the functional AP-1 binding site (nucleotide positions from -290 to -280), whose nucleotide mutations abolished PMA/ionomycin-induced DPYD promoter activation.
Abstract: It is widely accepted that activation of telomerase and maintenance of telomeres play central roles in cellular immortalization for most cancer cells. However, they seem to be insufficient for normal human cells. To elucidate critically responsible genes for telomerase mediated cellular immortalization in non-cancerous cells, we explored the genes that are differentially expressed throughout the immortalization process of normal human cells using cDNA microarrays with novel normalization procedures. We found that the number of genes, differentially expressed during cellular immortalization after ectopic expression of telomerase, dramatically increased in a later phase, especially in fibroblasts. We identified 18 and 20 genes/ESTs dysregulated throughout the cellular immortalization processes in fibroblasts and endothelial cells, respectively, but none of them overlapped. Only BGN and COL5A2 were commonly downregulated, except for at early phase in fibroblasts, and a few genes showed controversial expression changes, with regard to previous reports in cancer cells. These findings indicate that normal somatic cells would require cell-type specific events in addition to telomerase activation, and a rare population that eventually experience such events would acquire immortality. The key molecules that distinguish the immortalization mechanisms in cancerous and non-cancerous cells may become crucial targets for anticancer therapy and regenerative therapy.
Abstract: We screened for mutations in the von Hippel-Lindau (VHL) tumor suppressor gene and examined the relationship of these mutations with expression of hypoxia-inducible factor (HIF)-1alpha protein in human colorectal carcinomas. DNAs were extracted from 130 paraffin-embedded tumor specimens and subjected to polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis followed by direct sequencing. We identified 13 mutations in the coding sequence of VHL, 12 of which were unique events. Three mutations were located in exon 2 and the others in exon 3. These mutations were detected in 10 of 88 (11.4%) tumors tested. Furthermore, seven of the 13 (53.8%) VHL mutants immunohistochemically showed high HIF-1alpha expression. The mean percentage of cells with strong cytoplasmic HIF-1alpha expression was 67.5% in tumors with VHL mutations, and this level was significantly higher than that in tumors without mutations (50.8%, P < 0.05). These findings suggest that mutations in VHL may play a role in colorectal carcinoma via activation of the HIF-related transcriptional cascade.
Abstract: We developed concise, accurate prediction models of the in vitro activity for 8 anticancer drugs (5-FU, CDDP, MMC, DOX, CPT-11, SN-38, TXL and TXT), along with individual clinical responses to 5-FU using expression data of 12 genes. We first performed cDNA microarray analysis and MTT assay of 19 human cancer cell lines to sort out genes which were correlative in expression levels with cytotoxicities of the 8 drugs; we selected 13 genes with proven functional significance to drug sensitivity from a huge number of potent prediction marker genes. The correlation significance of each was confirmed using expression data quantified by real-time RT-PCR, and finally 12 genes (ABCB1, ABCG2, CYP2C8, CYP3A4, DPYD, GSTP1, MGMT, NQO1, POR, TOP2A, TUBB and TYMS) were selected as more reliable predictors of drug response. Using multiple regression analysis, we fixed 8 prediction formulae which embraced the variable expressions of the 12 genes and arranged them in order, to predict the efficacy of the drugs by referring to the value of Akaike's information criterion for each sample. These formulae appeared to accurately predict the in vitro efficacy of the drugs. For the first clinical application model, we fixed prediction formulae for individual clinical response to 5-FU in the same way using 41 clinical samples obtained from 30 gastric cancer patients and found to be of predictive value in terms of survival, time to treatment failure and tumor growth. None of the 12 selected genes alone could predict such clinical responses.
Abstract: Several lines of evidence suggest that gene expression is regulated not only by the interaction between transcription factors and DNA but also by the higher-order architecture of the cell nucleus. PML bodies are one of the most prominent nuclear substructures which have been implicated in transcription regulation during apoptosis and stress responses. Bach2 is a member of the BTB-basic region leucine zipper factor family and represses transcription activity directed by the 12-O-tetradecanoylphorbol-13-acetate response element, the Maf recognition element, and the antioxidant-responsive element. Bach2 forms nuclear foci associated with PML bodies upon oxidative stress. Here, we demonstrate that transcription activity associated with PML bodies is selectively repressed by the recruitment of Bach2 around PML bodies. Fluorescence recovery after photobleaching experiments revealed that Bach2 showed rapid turnover in the nuclear foci. The Bach2 N-terminal region including the BTB domain is essential for the focus formation. Sumoylation of Bach2 is required for the recruitment of the protein around PML bodies. These observations represent the first example of modulation of transcription activity associated with PML bodies by a sequence-specific transcription factor upon oxidative stress.
Abstract: PURPOSE: Dihydropyrimidine dehydrogenase (DPD), the initial rate-limiting enzyme in the degradation of 5-fluorouracil (5-FU), is known to be a principal factor in clinical responses to the anticancer agent 5-FU, and various reports have clearly demonstrated that DPD activity is closely correlated to mRNA levels. However, the regulatory mechanisms of DPD gene (DPYD) expression remain unclear. In this study, the regulatory mechanisms have been intensively studied. EXPERIMENTAL DESIGN AND RESULTS: A subcloned 3.0-kb fragment of the 5' region of DPYD contains a total of 60 CpG sites, suggesting that methylation status may affect the repression of DPYD. The clone showed various promoter activities that were largely correlated with mRNA levels in most cell lines, except HSC3 and HepG2. Bisulfite sequencing analysis revealed that various CpG sites around the transcription start site were abnormally methylated in cells with low DPYD expression: Reversal of hypermethylation by 5-azacytidine treatment significantly increased DPYD expression in HSC3 and HepG2 cells that showed strong promoter activity. In HepG2, in vitro methylation of the DPYD promoter directly decreased promoter activity, and 5-azacytidine treatment restored higher DPYD expression in a dose- and time-dependent manner, along with decreased sensitivity to 5-FU. CONCLUSIONS: We found that DPD activity was controlled, at least in part, at the transcription level of DPYD and that aberrant methylation of the DPYD promoter region acted as one of the repressors of DPYD expression and affected sensitivity to 5-FU in cancer cells. Our new results could lead to a more precise understanding of the molecular basis of 5-FU response.
Abstract: Colorectal carcinoma is one of the most common malignancies in the world, and its incidence has increased in recent years. We have reported that expression of hypoxia-inducible factor (HIF)-1alpha correlates with expression of vascular endothelial growth factor (VEGF), tumor stage, lymphatic invasion, venous invasion, and liver metastasis. It has also been reported that a single nucleotide polymorphism (SNP) in exon 12 of HIF-1alpha gene is present in renal cell carcinoma and head and neck squamous cell carcinoma patients. We investigated the C1772T polymorphism in colorectal cancer patients and healthy control subjects to clarify the mechanism of HIF-1alpha activation in colorectal carcinoma. The exon 12 genotype was not associated with sex or age. The distribution of HIF-1alpha genotypes in controls was 89 C/C (89%), 11 C/T (11%), and 0 T/T (0%). The distribution of HIF-1alpha genotypes in colorectal cancer patients was 100 C/C (100%), 0 C/T (0%), and 0 T/T (0%). The difference in genotype distribution between patients and control subjects was significant (p<0.0005). These results suggest that the C1772T polymorphism in HIF-1alpha is not involved in progression or metastasis of colorectal carcinoma.
Abstract: It is widely accepted that telomerase, which compensates for telomere shortening, is finally activated in almost all kinds of human malignant neoplasms, and ectopic expression of telomerase may endow some kinds of human somatic cells with indefinite proliferation capacity, i.e., immortality. To clarify the intrinsic responses required in acquiring immortality, we investigated the chronological changes in the expression levels of the cell cycle and apoptosis-related genes by real-time RT-PCR in human normal fibroblasts and endothelial cells after hTERT transfection. We found that fibroblast MJ90 required intrinsic responses including reversible upregulation of cell-cycle promoting genes and down-regulation of apoptosis-inducing genes in early phase after transfection, whereas the endothelial cell HUE142-2 did not. In addition, the microarray analysis of the fibroblast strains revealed that the dysregulated genes during cellular immortalization were different from those reported in fibroblasts probably having acquired telomere maintenance mechanism concomitant with hTERT induction. These findings indicate that cell-type specific differential gene expression after telomerase activation may be important to acquire telomere-maintenance capacity and immortality in some non-cancerous human cells. Investigation of these molecules may elucidate the differences in the capacity of acquiring immortality in cancer and normal somatic cells in future.
Abstract: Under normoxic conditions the hypoxia-inducible factor-1alpha (HIF-1alpha) protein is targeted for degradation by the von Hippel-Lindau (pVHL) tumor suppressor protein acting as an E3 ubiquitin ligase. Binding of pVHL to HIF-1alpha is dependent on hydroxylation of specific proline residues by O(2)-dependent prolyl 4-hydroxylases. Upon exposure to hypoxia the hydroxylase activity is inhibited, resulting in stabilization of HIF-1alpha protein levels and activation of transcription of target genes. One of the two critical proline residues, Pro(563) in mouse HIF-1alpha, is located within a bifunctional domain, the N-terminal transactivation domain (N-TAD), which mediates both pVHL-dependent degradation at normoxia and transcriptional activation at hypoxia. Here we have identified two N-TAD residues, Tyr(564) and Ile(565), which, in addition to Pro(563), were critical for pVHL-mediated degradation at normoxia. We have also identified D568A/D569A/D570A, F571A, and L573A as mutations of the N-TAD that abrogated binding to pVHL both in vitro and in vivo, and constitutively stabilized N-TAD against degradation. Moreover, the mutations Y564G, L556A/L558A, and F571A/L573A drastically reduced the transactivation function of either the isolated N-TAD or full-length HIF-1alpha in hypoxic cells. Interestingly, the P563A mutant exhibited a constitutively active and potent transactivation function that was enhanced by functional interaction with the transcriptional coactivator protein CREB-binding protein. In conclusion, we have identified by mutation analysis several residues that are critical for either one or both of the interdigitated and conditionally regulated degradation and transactivation functions of the N-TAD of HIF-1alpha.
Abstract: Hypoxia-inducible factor-1 (HIF-1) is a pivotal factor that regulates cellular responses to hypoxia and is presumably linked to regulation of angiogenesis and tumor growth. We assessed the difference in transcription activity of two HIF-1alpha polymorphic variants (P582S and A588T), along with molecular epidemiological study among head and neck squamous cell carcinoma (HNSCC) patients. Both HIF-1alpha variants revealed significantly higher transcription activity than wild-type (WT) did, under normoxic and hypoxic conditions (P < 0.02). Furthermore, tumors from HNSCC patients with heterozygous alleles having P582S or A588T had significantly increased numbers of microvessels compared with those with homozygous WT (P = 0.02). In addition, all patients with tumors of T1 (below 2 cm diameter) were WT, while 14 of 47 patients with tumors of > or =T2 were heterozygous. The elevated transactivation capacity of variant forms of HIF-1alpha implies a role of HIF-1alpha polymorphisms in generating individually different tumor progression.
Abstract: Gene delivery using cationic liposomes results in relatively low transfection, especially under in vivo conditions. This system, however, can overcome some of the problems associated with viral delivery systems. The present study was carried out in order to improve the transfection efficiency of cationic liposomes by preparing magnetic cationic liposomes (MCL). Small MCL approximately 40 nm in diameter and incorporating one or two magnetite particles were prepared with phosphatidylethanolamine and 3beta-[N-(N', N'-dimethylaminoethane)-carbamoyl] cholesterol. The efficiency of MCL in gene delivery was evaluated by using plasmid DNA containing a luciferase reporter gene and human osteosarcoma Saos-2 cells. Without a magnetic field, maximum luciferase activity was observed when DNA was mixed with MCL at a 1:5 ratio and incubated with cells for 6 h. Under a magnetic field, maximum luciferase activity was achieved by 30-min magnetic induction. This improvement in transfection efficiency by magnetic induction was approximately 3.5-fold. The feasibility of this active transgenic system was further shown by measuring apoptosis rates after transfection of the p53 gene to Saos-2 cells. Apoptosis rates increased to 18.9% from 2.4% by magnetic induction. In conclusion, a gene delivery system including MCL and magnetic induction was found to achieve rapid and enhanced gene delivery in vitro. Such a gene delivery system may be applicable under in vivo conditions, and is expected to offer numerous clinical advantages.
Abstract: The overexpression of estrogen receptor alpha (ERalpha) is frequently observed in the early stage of breast cancer. We previously reported that the specific promoter of the ERalpha gene is responsible for this enhanced transcription of the gene, and identified the cis-acting elements which play an important role in its transcription. Furthermore, methylation of the ERalpha gene promoters also contribute to the regulation of gene transcription. Elucidation of these mechanisms of ERalpha gene expression may provide useful information for the early detection and chemoprevention of breast cancer. On the other hand, the expression of ERbeta has been reported in breast cancer. We have also assessed the significance and function of ERbeta and its variant types in breast cancer, and suggest that ERbeta and ERbetacx specifically suppress the function of ERalpha through different mechanisms. ERbeta isoforms may be important functional modulators of the estrogen-signaling pathway in breast cancer cells, and might affect the clinical outcome of patients. Moreover, to address the role of these ERs on the estrogen-dependent growth of breast cancer cells and to develop a diagnostic tool, we have analyzed the gene expression profiles of estrogen-responsive genes using cDNA microarray. Based on these results, the expression of several candidate genes in breast cancer tissues were analyzed by real-time RT-PCR and by immunohistochemical techniques, in order to discover new predictive factors for the endocrine therapy of patients with breast cancer. These studies could provide new clues for the elucidation of the estrogen-dependent mechanisms of cancer and the clinical benefits for patients.
Abstract: Bcl-2 in cancer cells was shown to be a potent indicator of 5-FU efficacy, but the protein in normal tissue cells appeared not to be a marker of 5-FU toxicity probably due to the functional alteration of Bcl-2 associated with cell senescence. Transfection analysis of Bcl-2-S and Bcl-2-AS into A549 lung cancer cells revealed that Bcl-2 suppressed cell death induced by 5-FU, and the gene expression level of Bcl-2 was closely correlated with the IC50 for 5-FU in 21 fresh human gastric tumor specimens. Such correlation could not be observed in a neonatal human foreskin fibroblast strain, MJ90 (HCA2), and 21 human normal tissues adjacent to tumors. Transfection analysis of Bcl-2-S and Bcl-2-AS into MJ90 cells showed that Bcl-2 correlated with the resistance to 5-FU in the transfectants at PDL60 as in A549 cells, but increased Bcl-2 in the PDL72 senescent transfectant did not cause an increase of the resistance to 5-FU. Cell aging was observed in MJ90 cells and Bcl-2 in the cells was found to decrease with the cell senescence. The senescent cells, however, were more resistant to 5-FU than the younger PDL60 cells having proliferation activity.
Abstract: beta-tubulin (beta-TUB), Bcl-XL, and additionally glutathione S-transferase pi (GSTpi) were found to participate in sensitivity to docetaxel (TXT) in 7 human gastrointestinal cancer cell lines. The gene expression level of beta-TUB, Bcl-XL, and GSTpi was closely correlated with the IC50 for TXT. beta-TUB amount related to TXT resistance, and GST activity was correlated with IC50 for TXT in the 30-min treatment setting. Bcl-XL transfection increased TXT resistance of COLO201 cells, whereas GST inhibition by ethacrynic acid enhanced TXT cytotoxicity. Continuous TXT treatment increased beta-TUB and GSTpi expression, but the increased GSTpi mRNA was observed in TXT-resistant HCC-48 cells alone.
Abstract: Adaptation to hypoxia is a crucial process both physiologically (i.e. in chondrocytes) and pathologically (i.e. in tumor cells). Previous studies have shown that DEC1, a basic helix-loop-helix transcription factor, is induced by hypoxia in glioma cells (Ivanova, A. V., Ivanov, S. V., Danilkovitch-Miagkova, A., and Lerman, M. I. (2001) J. Biol. Chem. 276, 15306-15315). In the present study, we found that hypoxia or CoCl(2) enhanced the mRNA expression of DEC2, as well as DEC1, within 24 h in chondrogenic ATDC5, 293T, and HeLa cells. In luciferase assays, the regions between -524 and -401 in the DEC1 promoter, and between -863 and -258 in the DEC2 promoter, were responsible for the hypoxia- or hypoxia-inducible factor-1alpha (HIF-1alpha)-induced transcription. In these regions, we identified functional hypoxia response elements (HREs) that bound to HIF-1alpha and HIF-1beta. In addition to an HIF-1 binding site consensus sequence, the DEC1 HRE had cAMP response element-like and CACAG sequences, which were also involved in the transcription activation in response to HIF-1alpha. Although the DEC2 HRE did not have a cAMP response element-like or CACAG sequence, it showed a higher affinity for HIF-1 than did the DEC1 HRE. Because DEC1 and DEC2 are directly inducible by HIF-1, these transcription factors may be crucial for the adaptation to hypoxia.
Abstract: The precise mechanisms of resistance to camptothecin (CPT)-derived DNA topoisomerase (topo I) inhibitors and the determinants remain unclear. We found that a DNA repair protein, O(6)-methylguanine-DNA methyltransferase (MGMT), participated in resistance to irinotecan hydrochloride (CPT-11), its active metabolite SN-38, and a novel CPT derivative, DX-8951f. In 17 human cancer cell lines, MGMT gene expression level closely correlated with sensitivity to the CPT derivatives, and inhibition of MGMT activity by nontoxic 5 microM O(6)-benzylguanine augmented the drug activity in relation to the MGMT expression levels in 8 cell lines examined. Transfection of pCR / MGMT-sense into U-251MG and pCR / MGMT-antisense into T98G and HEC-46 cells revealed that increased MGMT expression decreased the sensitivity to CPT-11, SN-38, and DX-8951f, whereas repressed MGMT expression sensitized cells to the drugs. Western analysis revealed that treatment of MGMT-expressing T98G cells with the drugs caused a decrease of both MGMT and topo I in a dose-dependent manner. Although, in the transfectants, MGMT expression did not so closely correlate with the sensitivity to drugs as to nimustine hydrochloride (ACNU), MGMT is probably an important resistance determinant to CPT derivatives, and may play some role in the topo I-mediated DNA damage and / or the repair process.
Abstract: O6-methylguanine-DNA methyltransferase (MGMT), gamma-glutamylcysteine synthetase (gamma-GCS), and glutathione (GSH) are found to participate in resistance to TAS-103, a topoisomerase I/II inhibitor. In 13 human cancer cell lines, MGMT expression correlated with IC50 for TAS-103, whereas gamma-GCS expression inversely correlated with the IC50 value, suggesting MGMT may work to decrease TAS-103 activity but gamma-GCS may increase it. A reduced gamma-GCS and GSH, and an increased MGMT were associated with the development of resistance in A549 and DLD cells, and gamma-GCS inhibition by buthionine sulphoximine increased the TAS-103 resistance, whereas MGMT inhibition by both O6-benzyl-guanine and MGMT-antisense transfection sensitized cells to TAS-103.
Abstract: The abnormalities of the fragile histidine triad (FHIT) gene in tissue samples of oral squamous cell carcinomas (SCCs) along with several leukoplakias and an erythroplakia were examined to determine whether the FHIT gene is actually a frequent target in vivo for alteration during oral carcinogenesis. Abnormal transcripts of the FHIT gene were found in eight of 15 oral SCCs. Although these abnormal transcripts varied widely, deletion patterns incorporating a deletion of exon 5 were the most common. Loss of heterozygosity (LOH) analysis demonstrated that the abnormal FHIT transcripts found in cancer cells were attributable to abnormalities of the FHIT gene. Abnormal FHIT transcripts were also observed in two of seven premalignant lesions. Interestingly, in the case of one patient with a premalignant lesion showing an abnormal FHIT transcript, subsequent oral SCC developed during a 3-year follow-up period. On the other hand, in the two patients from whom both leukoplakia and SCC samples were taken simultaneously, abnormal FHIT transcripts were found only in the SCCs. Although the functional role of FHIT remains to be clarified, these results suggest that the FHIT alteration is actually involved in carcinogenesis of the oral epithelium.
Abstract: In normoxic cells the hypoxia-inducible factor-1 alpha (HIF-1 alpha) is rapidly degraded by the ubiquitin-proteasome pathway, and activation of HIF-1 alpha to a functional form requires protein stabilization. Here we show that the product of the von Hippel-Lindau (VHL) tumor suppressor gene mediated ubiquitylation and proteasomal degradation of HIF-1 alpha under normoxic conditions via interaction with the core of the oxygen-dependent degradation domain of HIF-1 alpha. The region of VHL mediating interaction with HIF-1 alpha overlapped with a putative macromolecular binding site observed within the crystal structure of VHL. This motif of VHL also represents a mutational hotspot in tumors, and one of these mutations impaired interaction with HIF-1 alpha and subsequent degradation. Interestingly, the VHL binding site within HIF-1 alpha overlapped with one of the minimal transactivation domains. Protection of HIF-1 alpha against degradation by VHL was a multistep mechanism, including hypoxia-induced nuclear translocation of HIF-1 alpha and an intranuclear hypoxia-dependent signal. VHL was not released from HIF-1 alpha during this process. Finally, stabilization of HIF-1 alpha protein levels per se did not totally bypass the need of the hypoxic signal for generating the transactivation response.
Abstract: We have previously shown that the distal promoter (promoter B) of the estrogen receptor alpha (ER alpha) gene is responsible for the enhanced expression of the ER alpha gene seen in human breast cancer and that a novel trans-acting factor, estrogen receptor promoter B associated factor 1 (ERBF-1), is required for transcription from promoter B in breast cancer cells. In development of breast cancer, loss of ER alpha gene expression is one of the most important steps in acquiring hormone resistance, though the mechanisms are poorly understood. Recent studies have reported that methylation of the ER alpha gene promoter A and exon 1 was inversely associated with ER alpha gene expression in human breast cancer and cell lines. The methylation status of the promoter B region, which is responsible for overexpression of ER alpha protein in cancer tissue, has not been investigated. In this report, we found that the methylation status of promoter B, as well as that of promoter A, was inversely associated with ER alpha gene expression in human breast cancer and cell lines. Specific methylation of ER alpha gene promoters in vitro directly decreased transcription of the ER alpha gene in a reporter assay. Demethylating treatment induced transcription of ER alpha mRNA from promoter B in ZR-75-1 cells, which showed no transcription from promoter B, despite weak ERBF-1 expression, but not in ER alpha-negative MDA-MB-231 and BT-20 cells, which lack ERBF-1. ZR-75-1 cells showed promoter activity equal to that of MCF-7 cells in a reporter assay. Our results indicate that methylation of promoter B of the ER alpha gene is important for loss of ER alpha gene expression in human breast cancer, and methylation of the promoters can directly modulate ER alpha gene expression. However, loss of critical transcriptional factors such as ERBF-1 may also be involved in some ER alpha-negative cases.
Abstract: Occurrence of abnormal transcripts of the FHIT (fragile histidine triad) gene has been reported in various types of cancer. On the other hand, aberrant transcripts are sometimes found in non-neoplastic tissues, so the relationship between the presence of abnormal transcripts of the FHIT gene and cancer pathogenesis is controversial. We investigated alterations in the FHIT locus, detected by nested reverse transcription-polymerase chain reaction and/or allelic status, in 88 primary lung cancers and normal lung tissues, and 22 normal lung tissues with metastatic lung cancer as a control. The frequencies of abnormal transcripts were 59% in lung cancer, 35% in paired normal lung, and 64% in normal control lung; the difference in frequencies between lung cancer and paired normal lung was significant, while that between lung cancer and normal control lung was not. Sequence analysis revealed that there were no cancer-specific abnormal transcripts entirely missing two or more exons, nor were the abnormal transcripts of lung cancer identical with those of paired normal lung in the same individual. Furthermore, we found no correlation between loss of heterozygosity in the FHIT locus and occurrence of abnormal FHIT transcripts. These results suggest that the presence of abnormal FHIT transcripts, in terms of their frequency and variety, is not cancer-specific in lung carcinogenesis, and the abnormality may be mainly due to abnormal splicing and processing of the transcripts. To estimate the precise function of the FHIT gene, further study of the FHIT protein in lung carcinogenesis is needed.
Abstract: The genetic polymorphisms of CYP1A1 and GSTM1 genes among 100 Japanese patients with oral squamous cell carcinomas (SCC) were investigated to evaluate the role of genetic susceptibility in carcinogenesis of the oral cavity. The presence of the rare homozygote of CYP1A1, m2/m2, was significantly more frequent in the patient group (15.0%) than the control group (8.0%) (Odds ratio (ORs) = 3.6 95% Confidential Interval (CI): 1.4-9.5). The heterozygotic variant, m1/m2, was also frequently seen in oral SCC patients. This meant that the m2 allele was observed in more than half of the patients. The null genotype of GSTM1 was found in 43.0% of the patient group. This was not significantly different from the controls (40.0%). When the life time cigarette consumption dose of the patients was considered with respect to genotypes of CYP1A1, the mean smoking index (SI) of oral SCC patients with m2/m2 was found to be less than half of the mean SI among the patients with m1/m1 genotype (P < 0.02). The ORs of the m2/m2 genotype was found to be significantly high in a comparison of various subsites of the oral cavity, except for the floor of the mouth. Our results indicate that the rare homozygote of CYP1A1, m2/m2, is associated with increased risk of oral SCC, in particular, at low cigarette dose levels. The results also suggested that the involvement of such susceptibility in oral carcinogenesis might be different between the subsites of the oral cavity.
Abstract: We have previously reported that transcription from a distal promoter (promoter B) of the estrogen receptor alpha (ERalpha) gene is responsible for the increased expression of ERalpha in human breast carcinomas. This paper first characterized the promoter B region in terms of transient transfection experiments with luciferase using MCF-7 cells. Gradual deletions from the 5'-end of promoter B resulted in a decrease in promoter activity corresponding to the deleted lengths; a deletion of 39 bp in a non-coding exon 1a, drastically diminished the activity, indicating existence of an important cis -element. Furthermore, electrophoretic mobility shift assay and subsequent mutational analysis indicated that this element containing nucleotide sequence CTGGAAAG forms a specific DNA-protein complex. This element was capable of transactivating a heterogeneous SV40 promoter in MCF-7 cells, confirming that the element is a transcriptional enhancer; the trans -acting factor binding to the element was named ERBF-1 (estrogen receptor promoter B associated factor-1). The ERBF-1 was exclusively expressed in those cells expressing ERalpha mRNA transcribed from promoter B. Our findings indicate that ERBF-1 plays an important role in the expression of the ERalpha gene transcribed from promoter B, which is selectively utilized in breast cancer.
Abstract: The antitumor effect of cis-diammine-1, 1-cyclobutane dicarboxylate platinum(II) (CBDCA, Carboplatin) and radiation on Ehrlich ascites tumors was evaluated in CD-1 mice. A single dose of CBDCA was combined with a single dose of radiation. The antitumor effect was evaluated by tumor volume. Inhibition of tumor growth by the combination of CBDCA and radiation was greater than by CBDCA and radiation alone. The most effective condition was the simultaneous combination of CBDCA with radiation. Further, we examined the radiation influence on the concentration of platinum in tumor tissue. We found that when CBDCA was administered after irradiation, the concentration of platinum in tumor tissue decreased proportionally with time.
Abstract: Deletions in the short arm of chromosome 3 have been found in various human cancers, including breast cancer. Recently, the FHIT (fragile histidine triad) gene was identified at 3p14.2 as a candidate tumor suppressor gene. We examined the abnormal transcripts of the FHIT gene in 61 Japanese primary breast cancer specimens and found that 23 (38%) of them exhibited abnormalities, about half of which were categorized into two types of aberrant transcripts. Sequence analysis of these aberrant transcripts revealed the absence of exons 5-7 (type I) and exons 5-8 (type II). Clinicopathological and epidemiological analysis of patients showed that the abnormal FHIT transcripts were not associated with age, tumor-node-metastasis classification, tumor size, estrogen receptor and progesterone receptor status, local metastasis, family history of breast cancer, or lifestyle factors of patients, including cigarette smoking and alcohol consumption. On the other hand, we found that the abnormal transcripts of type I and type II were associated with the incidence of bilateral breast cancer and that decreased frequency of childbirth was also associated with FHIT abnormalities.
