Haplo-Insufficiency of TSGs on Chromosome 2 for Paclitaxel-Resistant Phenotype of OCCA Cells

The frequency of ovarian clear cell adenocarcinoma (OCCA), one unique type epithelial ovarian cancer (EOC), generally is higher in Taiwan and Japan than other countries. Unlike other types of EOC, OCCA is more associated with endometriosis and has high percentage diagnosed at an early stage with tumor confined to the ovary. Paclitaxel is a very active agent in the treatment of advanced ovarian cancer but not for OCCA which is more resistant to platinum-/taxan-based chemotherapy and has poor prognosis with aggressive behavior. The anticancer effect of paclitaxel is mainly due to its irreversible microtubule inhibitor activity and is hampered upon progress of chemo-resistance in tumor cell. Many theories involved in drug resistance have been proposed for chemo-resistance of EOC, including the presence of cancer stem cells, enrichment/selection of natively resistant cells, alterations in the tumor microenvironment, and altered pathways for drug influx/efflux, detoxification, and DNA repair, leading to signaling cell survival. However, none of these can fully explain the higher chemo-resistance behavior of OCCA. To investigate the genetic determinant of the paclitaxel-resistance in OCCA, we have applied CGH microarray to analyze the integrity of genomes of the established paclitaxel-resistant OCCA cell lines (ES2-TR120 and ES2-TR300) derived from parental OCCA cell line, the ES-2 cells. Genome instability with larger regions of amplification or deletion is found on several chromosomes in the genomes of ES2-TR120 and ES2-TR300 cells, compared to the genome of the parental ES2 cells. To explore the genetic determinant of the paclitaxel-resistance in OCCA, we propose a three-year research project to investigate the biological significance of paclitaxel-resistance related genome instability in OCCA, especially the aberrant gene dosages of candidate TSGs detected on chromosome 2 that shows the greatest instability genome-wide. We plan to identify possible processes or pathways affected by this genomic instability and their relationship to paclitaxel-resistance of OCCA. The Central Hypothesis of this project is that haplo-insufficiency of multiple genes on chromosome 2 together cooperate may affect the paclitaxel sensitivity of OCCA. We aim to focus on haplo-insufficiency of 6 TSGs genes to reveal the causal-effect of gene dosages abnormality to the paclitaxel-resistance phenotype of the ES2-TR cells. The novelty of this study is to clarify whether haplo-insufficiency of genes on chromosome 2 may trigger cell transformation to the senescence state, attenuate cell death, and result in the promotion of chromosomal instability, which enables OCCA tumor cells to efficiently bypass the killing of chemo-drug pressures. And specific aims in this project are: Specific Aim 1 (1st year and 2nd year): The impact of single or combined haplo-insufficiency at the candidate TGSs, RHOB, SPTBN1, and RND3 on paclitaxel-resistance of OCCA in terms of cell morphology, adhesion and migration ability and drug-sensitivity will be elucidated in the first year study. Specific Aim 2 (2st year): To elucidate the impact of single or combined haplo-insufficiency at the candidate TGSs, CASP8, BOK, ATG16L1 and CAPN13 and its biological correlation to in paclitaxel-resistance of OCCA in terms of drug-induced cell death. Specific Aim 3 (2st year and 3th year): To elucidate the haplo-insufficiency and its senescence-related function of C2orf40 (Ecrg4) in paclitaxel-resistance of OCCA.