ZIA BC 010830 (ZIA) | |||
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Title | Mechanisms of non-classical multidrug resistance in cancer | ||
Institution | NCI, Bethesda, MD | ||
Principal Investigator | Gottesman, Michael | NCI Program Director | N/A |
Cancer Activity | N/A | Division | CCR |
Funded Amount | $999,694 | Project Dates | 10/01/2006 - 00/00/0000 |
Fiscal Year | 2014 | Project Type | Intramural |
Research Topics w/ Percent Relevance | Cancer Types w/ Percent Relevance | ||
Bioengineering (15.0%) Cancer (100.0%) Chemotherapy (30.0%) Childhood Cancers (5.0%) Digestive Diseases (20.0%) Taxol (30.0%) |
Breast (30.0%) Cervical Cancer (10.0%) Colon/Rectum (10.0%) Kidney Cancer (5.0%) Kidney Disease (5.0%) Liver Cancer (10.0%) Ovarian Cancer (15.0%) Prostate (10.0%) Urinary System (5.0%) |
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Research Type | |||
Systemic Therapies - Discovery and Development Development and Characterization of Model Systems |
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Abstract | |||
Three major approaches have been taken to define non-classical multidrug resistance in cancer. In the first, we isolated KB cells (a subclone of HeLa) resistant to increasing levels of cisplatin (CP-r) and demonstrated multidrug resistance to arsenite and cadmium, to methotrexate, and to nucleoside analogs. This cross-resistance pattern is due to reduced uptake of each of these agents because their receptors have been relocalized from the cell surface into the cytoplasm of the cell. This relocalization of surface transporters appears to be due to altered recycling of these transporters due to alterations in the cytoskeleton that affect endocytic recycling compartments in cisplatin-resistant cells. Overexpression of the negative transcription regulator GCF2 occurs in cisplatin-resistant lines, which reduces expression of rhoA, causing disruption of the cytoskeleton as a proximate cause of this recycling defect. One additional consequence of reduced cell surface transporters is a reduction in glucose uptake and altered mitochondrial metabolism mediated by SIRT1. These changes are best understood as regulatory alterations due to epigenetic changes such as DNA methylation, histone modifications, and miRNA perturbations. The protein metallotheinein, heat shock proteins, ribosomal proteins, a selenoprotein, and the trans-membrane protein TMEM205 have been shown to play a role in cisplatin resistance. Expression of TMEM205, a membrane protein expressed in normal secretory cells, in combination with the small GTPase Rab8, confers cisplatin resistance. We have demonstrated changes in specific microRNAs (miRNAs), such as miRNA-181, consistently seen in cisplatin-resistant KB cells, and their contribution to drug resistance has been demonstrated by expression of miRNA mimics and inhibitors. In addition, a high throughput analysis of miRNAs that reverse the cisplatin resistance of KB-CP-r cells has identified WEE1 and CHK1 as essential elements of resistance to cisplatin. miRNA155 and miR-15 family members are miRNAs whose expression affects cisplatin resistance through WEE1 and CHK1. We recently completed an RNAi screen in cells exposed to cisplatin, in order to identify genes associated with cisplatin sensitivity. If cells exposed to sub-toxic cisplatin undergo cell death when a particular gene is deleted, one can hypothesize that inhibition of this gene target might prove to be a useful adjuvant for platinum chemotherapy. The strongest sensitizing effects were observed when DNA damage repair genes were silenced, and several of these are now being investigated for their role in cisplatin tolerance. In this screening context, we found a need to identify a solvent appropriate for dissolving cisplatin for screening. We recently published a report showing that DMSO affected (inactivated) the biological activity of all clinical and experimental platinum complexes tested. Furthermore, a review of the cisplatin literature revealed that about a third of all research papers have used cisplatin dissolved in DMSO, calling into question the data and conclusions of those papers. This has important implications for the reliability of a significant portion of the literature and points the way for appropriate use of platinum drugs in research. A second approach is to evaluate the unique features of melanoma cells that contribute to multidrug-resistance. One obvious feature of melanoma cells is the melanosome, a lysosome-derived organelle in which pigment formation takes place. We have shown that cisplatin is sequestered in this organelle, independent of extent of melanin formation, and extruded with melanosomes into the medium, reducing nuclear accumulation of this anti-cancer drug. Studies are underway to determine whether ABCB5, a transporter homologous to ABCB1, expressed at high levels in pigmented cells such as melanocytes and melanomas, contributes to the melanosomal sequestration seen in melanomas. Full-length ABCB5 has been expressed in KB cell" |