Valentinos Kounnis

Abstract: BIK (bcl2-interacting killer) is the founding member of the BH3-only bcl-2 family of pro-apoptotic proteins, which is suppressed in various cancers. In multiple myeloma (MM), BIK has been shown to be epigenetically silenced in vitro, but there is a lack of clinical data. We investigated the CpG methylation status of the BIK promoter in a well-characterized clinical series of patients with MM and investigated its clinical relevance. Forty patients with MM (21 male, 19 female; mean age 66) were studied. According to the International Staging System (ISS) they were classified as 16 patients with stage I, 12 patients with stage II and 12 patients with stage III disease. Methylation in the BIK CpG island was assessed by methylation-specific polymerase chain reaction (MSP) assay. Logistic regression analysis was used to investigate associations between gene methylation and age, ISS stage, performance status, extramedullary disease, bone disease, anemia (hemoglobin ≤10 mg/dL), serum albumin, β2-microglobulin level and relapsed/refractory disease. Methylation in the BIK CpG island was detected in 16 patients (40%), with a trend favoring male gender (odds ratio [OR] = 3.08, p = 0.09) and development of bone disease and extramedullary disease (OR = 1.6, p = 0.35 and OR = 3, p = 0.14, respectively). Patients with MM with methylated BIK CpG island had a statistically significant risk for disease evolution to relapsed/refractory disease (OR = 5.4, p = 0.03). This study provides clinical evidence that methylation-induced transcriptional silencing of the BIK pro-apoptotic gene may occur in MM, which might serve as a predictor of the development of relapsed/refractory MM. These findings warrant validation in larger cohorts of patients and suggest therapeutic utility for agents that enhance BIK expression.

Abstract: BACKGROUND: Organic anion-transporting polypeptides (OATPs) are influx transporters that mediate intracellular uptake of selective endogenous and xenobiotic compounds. Identification of new molecular targets and discovery of novel targeted therapies is top priority for pancreatic cancer, which lacks any effective therapy. MATERIALS AND METHODS: We studied expression of OATP 1A2, 1B1, and 1B3 in pancreatic cancer tissue and in cell lines. Formalin-fixed paraffin-embedded biopsy material of 12 human pancreatic cancers was immunohistochemically assessed for protein expression of the three studied influx transporters. Immunohistochemistry was evaluated by experienced pathologists and quantified by use of an automated image analysis system. BxPC-3 and MIA PaCa-2 pancreatic cancer cell lines were used to quantify transcripts of OATP 1B1 and 1B3. RESULTS: OATP 1A2, 1B1, and 1B3 proteins were found ubiquitously expressed in all studied cases. Quantification performed by HistoQuest system revealed that mean intensity was 53 for 1A2, 45 for 1B1, and 167 for OATP 1B1/1B3 on a range scale 0-250 units. At mRNA level, 1B1 and 1B3 were overexpressed in both studied cancer cell lines but not in normal pancreatic tissue. CONCLUSION: OATPs 1A2, 1B1, and 1B3 are highly expressed in pancreatic adenocarcinoma. We suggest that expression of these transporters in pancreatic cancer justify research efforts towards discovery of novel therapeutics targeting OATPs.

Abstract: Cyanobacterial cyclopeptides, including microcystins and nodularins, are considered a health hazard to humans due to the possible toxic effects of high consumption. From a pharmacological standpoint, microcystins are stable hydrophilic cyclic heptapeptides with a potential to cause cellular damage following uptake via organic anion-transporting polypeptides (OATP). Their intracellular biological effects involve inhibition of catalytic subunits of protein phosphatase 1 (PP1) and PP2, glutathione depletion and generation of reactive oxygen species (ROS). Interestingly, certain OATPs are prominently expressed in cancers as compared to normal tissues, qualifying MC as potential candidates for cancer drug development. In the era of targeted cancer therapy, cyanotoxins comprise a rich source of natural cytotoxic compounds with a potential to target cancers expressing specific uptake transporters. Moreover, their structure offers opportunities for combinatorial engineering to enhance the therapeutic index and resolve organ-specific toxicity issues. In this article, we revisit cyanobacterial cyclopeptides as potential novel targets for anticancer drugs by summarizing existing biomedical evidence, presenting structure-activity data and discussing developmental perspectives.

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