Abstract: BACKGROUND & AIMS: Autophagy is a metabolic process that degrades and recycles intracellular organelles and proteins with many connections to human disease and physiology. We studied the role of autophagy during hepatic stellate cell (HSC) activation, a key event in liver fibrogenesis. METHODS: Analysis of the autophagic flux during in vitro activation of primary mouse HSCs was performed using a DsRed-GFP-LC3B encoding plasmid. The effect of autophagy inhibition by bafilomycin A1 on the in vitro activation process of human and mouse HSCs was examined by measuring proliferation, presence of activation markers by RT-qPCR, immunofluorescence, and Western blotting. Analysis of lipid droplet and microtubule-associated protein light chain 3 beta (LC3B) colocalization in the presence of PDGF-BB was investigated by immunocytochemistry. RESULTS: A significant increased autophagic flux was observed during culture induced mouse HSC activation. Treatment of mouse HSCs and human HSCs with autophagy inhibitor bafilomycin A1 results in a significant decreased proliferation and expression of activation markers. In addition, lipid droplets and LC3B colocalization was increased after PDGF-BB treatment in quiescent HSCs. CONCLUSIONS: During HSC activation, autophagic flux is increased. The demonstration of partly inhibition of in vitro HSC activation after treatment with an autophagy inhibitor unveils a potential new therapeutic strategy for liver fibrosis.
Abstract: The role of progenitor cells in liver repair and fibrosis has been extensively described but their purification remains challenging, hampering their characterization and use in regenerative medicine. To address this issue, we developed an easy and reproducible liver progenitor cell (LPC) isolation strategy based on aldehyde dehydrogenase (ALDH) activity, a common feature shared by many progenitor cells. We demonstrate that a subset of non-parenchymal mouse liver cells displays high levels of ALDH activity, enabling the isolation of these cells by fluorescence activated cell sorting. Immunocytochemistry and qPCR analyses on freshly isolated ALDH(+) cells reveal an enrichment in cells expressing liver stem-cell markers such as EpCAM, CK19, CD133 and Sox9. In culture, the ALDH(+) population can give rise to functional hepatocyte-like cells as illustrated by albumin and urea secretion and cytochrome P450 activity. ALDH1A1 expression can be detected in canals of Hering and bile duct epithelial cells and is increased upon liver injury. Finally, we could show that the isolation and differentiation towards hepatocyte-like cells of LPCs with high ALDH activity is also successfully applicable to human liver samples. (HEPATOLOGY 2011.) CONCLUSIONS: High ALDH activity is a feature of LPCs that can be taken advantage of to isolate these cells from untreated mouse as well as from human liver tissues. This novel protocol is practically relevant, as it provides an easy and non-toxic method to isolate liver stem cells from normal tissue for potential therapeutic purposes.
Abstract: Many chronic liver diseases can lead to hepatic dysfunction with organ failure. At present, orthotopic liver transplantation represents the benchmark therapy of terminal liver disease. However this practice is limited by shortage of donor grafts, the need for lifelong immunosuppression and very demanding state-of-the-art surgery. For this reason, new therapies have been developed to restore liver function, primarily in the form of hepatocyte transplantation and artificial liver support devices. While already offered in very specialized centers, both of these modalities still remain experimental. Recently, liver progenitor cells have shown great promise for cell therapy, and consequently they have attracted a lot of attention as an alternative or supportive tool for liver transplantation. These liver progenitor cells are quiescent in the healthy liver and become activated in certain liver diseases in which the regenerative capacity of mature hepatocytes and/or cholangiocytes is impaired. Although reports describing liver progenitor cells are numerous, they have not led to a consensus on the identity of the liver progenitor cell. In this review, we will discuss some of the characteristics of these cells and the different ways that have been used to obtain these from rodents. We will also highlight the challenges that researchers are facing in their quest to identify and use liver progenitor cells.
Abstract: Unfortunately, the anticancer drugs that are used nowadays in the clinic have only limited success. To provide a significant clinical advancement, new concepts have to be introduced to aid the design of new tools for therapy. Cancer is not only restricted to neoplastic cells, but rather it involves an ensemble of protagonists. In addition, the evolution of cancer is extremely complex, since multiple cellular activities are involved. Some key steps in the evolution to a metastatic tumor have been shown to be no useful targets. Targeting the stroma cells, however, could bring a new efficiency in anticancer treatment. Targeting the disorganized tissue architecture at the primary site and the restoration of the cell death program in cancer cells appears to create new possibilities in drug design. Also the cytoskeleton, which represents a dynamic set due to its plasticity and multiplicity, seems to be a promising target in anticancer therapy. Moreover, the evolving knowledge of the role of metastasis suppressor genes in regulating cancer cell growth at the secondary site suggests that they could serve as new targets for therapeutic intervention. This review intends to highlight the unraveling of new therapeutic pathways, and to unveil new powerful research tools for combating metastasis.
Abstract: To define better the function of Nerve Growth Factor (NGF) in breast cancer progression, we investigated whether this polypeptide was able to induce breast cancer cell invasion. NGF inhibited aggregation of tumour cells through modulation of the E-cadherin/catenin complex function. In addition, NGF induced the breast cancer cells to invade into Matrigel. We focused our attention on how NGF prevents aggregation, in order to discover the signalling pathway that leads tumour cells to acquire the invasive phenotype. Moreover, studies on the identification of signalling pathways that are responsive for NGF-induced invasion will be basically described.
Abstract: Nerve growth factor (NGF) has long been known for its effects on neuronal cell survival and differentiation. This prototypical neurotrophic factor stimulates neurons through two distinct classes of membrane receptors: the TrkA tyrosine kinase receptor, and the tumor necrosis factor receptor family member p75NTR, also known as the common neurotrophin receptor. Somewhat surprisingly, there is a growing body of evidence indicating that NGF is also a major stimulator of breast cancer cell growth. Both the survival and proliferation of breast cancer cells are strongly stimulated by NGF, mediated by TrkA and p75NTR respectively, utilising signaling pathways similar to those described for neurons. In addition, although NGF is produced by breast cancer cells, it is not in normal breast epithelial cells, giving rise to an autocrine stimulation of tumor growth. Therefore, NGF receptors and signaling are thus looking increasingly promising as potential drug targets for breast cancer.
Abstract: We show here that nerve growth factor (NGF), the canonical neurotrophic factor, is synthesized and released by breast cancer cells. High levels of NGF transcript and protein were detected in breast cancer cells by reverse transcription-PCR, Western blotting, ELISA assay and immunohistochemistry. Conversely, NGF production could not be detected in normal breast epithelial cells at either the transcriptional or protein level. Confocal analysis indicated the presence of NGF within classical secretion vesicles. Breast cancer cell-produced NGF was biologically active, as demonstrated by its ability to induce the neuronal differentiation of embryonic neural precursor cells. Importantly, the constitutive growth of breast cancer cells was strongly inhibited by either NGF-neutralizing antibodies or K-252a, a pharmacological inhibitor of NGF receptor TrkA, indicating the existence of an NGF autocrine loop. Together, our data demonstrate the physiological relevance of NGF in breast cancer and its potential interest as a marker and therapeutic target.
Abstract: The common neurotrophin receptor p75(NTR) has been shown to initiate intracellular signaling that leads either to cell survival or to apoptosis depending on the cell type examined; however, the mechanism by which p75(NTR) initiates its intracellular transduction remains unclear. We show here that the tumor necrosis factor receptor-associated death domain protein (TRADD) interacts with p75(NTR) upon nerve growth factor (NGF) stimulation. TRADD could be immunodetected after p75(NTR) immunoprecipitation from MCF-7 breast cancer cells stimulated by nerve growth factor. In addition, confocal microscopy indicated that NGF stimulation induced the plasma membrane localization of TRADD. Using a dominant negative form of TRADD, we also show that interactions between p75(NTR) and TRADD are dependent on the death domain of TRADD, thus demonstrating its requirement for binding. Furthermore, the p75(NTR)-mediated activation of NF-kappaB was inhibited by transfection with a dominant negative TRADD, resulting in an inhibition of NGF antiapoptotic activity. These results thus demonstrate that TRADD is involved in the p75(NTR)-mediated antiapoptotic activity of NGF in breast cancer cells.
Abstract: The near completion of human genome sequencing and the introduction of mass spectrometry combined with advanced bioinformatics for protein identification have led to the emergence of proteomics as a powerful tool for characterizing new markers and therapeutic targets. Breast cancer proteomics has already identified proteins of potential clinical interest, such as the molecular chaperone 14-3-3 sigma and the heat shock protein HSP90, and technological innovations such as large scale and high throughput analysis are now driving the field. Methods in functional proteomics have also been developed to study the intracellular signaling pathways that underlie the development of breast cancer cells. As illustrated by fibroblast growth factor-2 and the H19 noncoding oncogenic mRNA, proteomics is a pertinent approach to identify signaling proteins and to decipher the complex signaling circuitry involved in tumor growth and metastasis. Together with genomics, proteomics is now providing a way to define molecular processes involved in breast carcinogenesis and to identify new therapeutic targets. The next challenge will be the introduction of proteomics as a tool for the clinic, for the establishment of diagnosis, prognosis, and the monitoring of treatment; however, this ambitious goal still requires further technological progress in the field.
