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 | $872,302 | Project Dates | 01/01/2006 - 00/00/0000 |
Fiscal Year | 2015 | 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. The protein metallotheinein, heat shock proteins, ribosomal proteins, a selenoprotein, and the trans-membrane protein TMEM205 have also 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. Our interest in the checkpoint kinases and their role in resistance led us to the protein phosphatase 2A (PP2A) inhibitor LB100, currently in Phase I clinical trials for breast cancer. As PP2A controls the phosphorylation status of a number of DNA-damage response (DDR) genes, we hypothesized that LB100 would sensitize ovarian cancer cells to cisplatin. We demonstrated that inhibition of PP2A by LB100 sensitized cells (OVCAR8 and SKOV3) to cisplatin, and that LB100 induces hyperphosphorylation of Chk1 and other genes in the DNA-damage response pathway, preventing cisplatin-induced G2 arrest and forcing cells into mitosis, resulting in apoptosis. We showed that mice injected intraperitoneally with SKOV3-luciferase cells were sensitized to cisplatin (3 mg/kg) when treated with LB100 compared with control. 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 (including a phosphoprotein phosphatase) 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 showed that DMSO 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 whic |