Characterization of two independent, exposure-time dependent paclitaxel-resistant human ovarian carcinoma cell lines

Transcriptome Remodeling in Gradual Development of Inverse Resistance between Paclitaxel and Cisplatin in Ovarian Cancer Cells

Resistance to anti-cancer drugs is the main challenge in oncology. In pre-clinical studies, established cancer cell lines are primary tools in deciphering molecular mechanisms of this phenomenon. In this study, we proposed a new, transcriptome-focused approach, utilizing a model of isogenic cancer cell lines with gradually changing resistance. We analyzed trends in gene expression in the aim to find out a scaffold of resistance development process. The ovarian cancer cell line A2780 was treated with stepwise increased concentrations of paclitaxel (PTX) to generate a series of drug resistant sublines. To monitor transcriptome changes we submitted them to mRNA-sequencing, followed by the identification of differentially expressed genes (DEGs), principal component analysis (PCA), and hierarchical clustering. Functional interactions of proteins, encoded by DEGs, were analyzed by building protein-protein interaction (PPI) networks. We obtained human ovarian cancer cell lines with gradually developed resistance to PTX and collateral sensitivity to cisplatin (CDDP) (inverse resistance). In their transcriptomes, we identified two groups of DEGs: (1) With fluctuations in expression in the course of resistance acquiring; and (2) with a consistently changed expression at each stage of resistance development, constituting a scaffold of the process. In the scaffold PPI network, the cell cycle regulator-polo-like kinase 2 (PLK2); proteins belonging to the tumor necrosis factor (TNF) ligand and receptor family, as well as to the ephrin receptor family were found, and moreover, proteins linked to osteo- and chondrogenesis and the nervous system development. Our cellular model of drug resistance allowed for keeping track of trends in gene expression and studying this phenomenon as a process of evolution, reflected by global transcriptome remodeling. This approach enabled us to explore novel candidate genes and surmise that abrogation of the osteomimic phenotype in ovarian cancer cells might occur during the development of inverse resistance between PTX and CDDP.

A feasibility study on maintenance of docetaxel after paclitaxel-carboplatin chemotherapy in patients with advanced ovarian cancer

Objective

To test the concept of taxane sequencing, this feasibility trial evaluated maintenance of docetaxel after paclitaxel and carboplatin combination chemotherapy in patients with stage IC-IV ovarian cancer.

Methods

All patients received debulking surgery followed by paclitaxel and carboplatin chemotherapy. Attainment of clinically defined complete or partial response was confirmed by image scanning. Maintenance of docetaxel started at an initial dose of 70 mg/m² every 4 weeks for 6 cycles and was extended to 10 cycles unless disease progression and/or recurrence during the protocol therapy or unacceptable toxicities were seen.

Results

Stage subsets in 20 eligible patients were as follows: IIIB, 2 patients (10%); IIIC, 13 patients (65%); IV, 5 patients (25%). Neutropenia was common (40% with grade 3 or 4) and was most frequent during first or second cycle although the disabling peripheral neuropathy was not observed. Twelve patients completed protocol therapy (6≤cycles), while 8 patients failed to complete 6-cycle chemotherapy, because of progressive disease (5 patients) or grade 4 toxicities (3 patients). Median PFS was 20 months and 3-year PFS rate was 12%. Median overall survival was 39 months and 3-year OS rate was 69%.

Conclusion

Six cycles of single-agent docetaxel maintenance chemotherapy is feasible and generally tolerable to women with advanced ovarian cancer who attained a clinically defined response to initial paclitaxel and carboplatin based chemotherapy.

Polo Like Kinase 2 Tumour Suppressor and cancer biomarker: new perspectives on drug sensitivity/resistance in ovarian cancer

The polo-like kinase PLK2 has recently been identified as a potential theranostic marker in the management of chemotherapy sensitive cancers. The methylation status of the PLK2 CpG island varies with sensitivity to paclitaxel and platinum in ovarian cancer cell lines. Importantly, extrapolation of these in vitro data to the clinical setting confirms that the methylation status of the PLK2 CpG island predicts outcomes in patients treated with carboplatin and paclitaxel chemotherapy. A second cell cycle regulator, p57Kip2, is also subject to epigenetic silencing in carboplatin resistance in vitro and in vivo, emphasising that cell cycle regulators are important determinants of sensitivity to chemotherapeutic agents and providing insights into the phenomenon of collateral drug sensitivity in oncology. Understanding the mechanistic basis and identification of robust biomarkers to predict collateral sensitivity may inform optimal use of chemotherapy in patients receiving multiple lines of treatment.