Project description:Goal of the experiment: To examine differential gene expression in three ovarian cancer cell lines in the absence and presence of mifepristone. Brief description of the experiment: Hypothesis: The gene expression profile associated with a cytostatic response to Mifepristone will be similar between ovarian cancer cells regardless of their p53 status or sensitivity to Cisplatin. Aim: Evaluate the modifications in gene expression profile in ovarian cancer cells in response to a cytostatic concentration of Mifepristone against those in logarithmic phase of growth (Vehicle). Compare the gene expression profile of cells with different genetic backgrounds as well as between those with identical genetic backgrounds but different sensitivities to Cisplatin. Cell Types: SKOV-3 as null p53 and semi-resistant to Cisplatin, OV2008 cells as wild type p53 and hyper-sensitive to Cisplatin , OV2008/C13 cells as wild type p53 and resistant to Cisplatin. Conditions: Cells from three different passages were cultured in T25 flasks. The starting number of cells was 250,000 or 500,000, however cells were left to grow for 48 hr or 24 hr respectively before to start the treatment with Mifepristone 8.6 µg/ml (20 µM) or DMSO (vehicle) for 24 hr.
Project description:<p>BRCA1 mutations are a hallmark of hereditary ovarian cancer, strongly linked to deficiencies in homologous recombination (HR) DNA repair and impaired DNA replication fork protection. However, its roles in cancer progression beyond maintaining genomic integrity remain poorly understood. Through metabolomics approaches, we found BRCA1-deficiency strikingly increased choline metabolism. Loss of BRCA1 promotes choline uptake through upregulating choline transporter-like protein 4 (CTL4). BRCA1 directly binds and recruits EZH2-mediated H3K27Me3 deposition to CTL4 promoter. CTL4 was therefore overexpressed in ovarian cancer tissues with BRCA1 mutations. Furthermore, BRCA1-deficiency significantly promotes ovarian cancer invasion, while inhibition of CTL4 reverses the high metastatic potential of BRCA1-deficient ovarian cancer cells, suggesting the functionality and specificity of CTL4 as a therapeutic target. Additionally, we discovered that phosphocholine, the choline metabolite increased by CTL4 overexpression, interacted with and stabilized the epithelial-to-mesenchymal transition inducer FAM3C in BRCA1-deficient ovarian cancer cells. Importantly, we identified a potent CTL4 inhibitor, DT-13, which significantly reduces choline metabolism and effectively suppresses metastasis in BRCA1-deficient ovarian cancers. Therefore, our study uncovers a mechanism underlying metastasis in BRCA1-deficient cancers and identifies CTL4 as a therapeutic target for metastatic ovarian cancer patients with BRCA1 mutations.</p>
Project description:PARP inhibitor olaparib induces the formation of polyploid giant cancer cells (PGCCs) in ovarian and breast cancer cell lines, human high-grade serous ovarian cancer (HGSC)–derived organoids, and HGSC patient-derived xenografts (PDXs). Time-lapse tracking of ovarian cancer cells revealed that PGCCs primarily developed from endoreplication of cancer cells after exposure to sublethal concentrations of olaparib. PGCCs exhibited features of senescent cells but, after olaparib withdrawal, could escape senescence via restitutional multipolar endomitosis and other modes of cell division to generate mitotically competent resistant daughter cells. The contraceptive drug mifepristone blocked PGCC formation and daughter cell production. Mifepristone/olaparib combination therapy substantially reduced tumor growth in PDX models without previous olaparib exposure, while mifepristone alone decreased tumor growth in PDX models with acquired olaparib resistance. Thus, targeting PGCCs may represent a promising approach to potentiate the therapeutic response to PARPi and overcome PARPi-induced resistance.
