Unknown,Transcriptomics,Genomics,Proteomics

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Differences in gene expression in A2780C20 vs. A2780

ABSTRACT: Differences in gene expression in A2780C20 vs. A2780 and A2780 treated with temsirolimus at 24-hr and 48-hr. The A2780 are human ovarian carcinoma cellls were purchased to the European Collection of Cell Cultures (ECACC). The A2780CP20 are cisplatin resisatnt cells derived of the A2780 cells. A2780CP20 cells were generated by Dr. Robert Ozols (J. Natl. Cancer Inst. 84, 264-267 (1992) by treatment of A2780 cells with incresing concentrations of cisplatin. The goal of this study is to determine whether the cisplatin and temsirolimus resistance are co-regulated. The objectives of this study are to identify additional genes differentially expressed in cisplatin sensitive and cisplatin resistant ovarain cancer cells and the changes in gene expreession upon temsirolimus treatment of A2780 cells. RNA was isolated from A2780, A2780CP20, A2780 plus temsirolimus 24-hr, and A2780 plus temsirolimus 48-hr. Labelled samples were hybridized to Affymetrix GeneChip Gene 1.0 ST Human Arrays.

ORGANISM(S): Homo sapiens

SUBMITTER: Pablo Vivas-Mejia

PROVIDER: E-GEOD-51683 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Drug resistance poses a major challenge to ovarian cancer treatment. Understanding mechanisms of drug resistance is important for finding new therapeutic targets. In the present work, a cisplatin-resistant ovarian cancer cell line A2780-DR was established with a resistance index of 6.64. The cellular accumulation of cisplatin was significantly reduced in A2780-DR cells as compared to A2780 cells consistent with the general character of drug resistance. Quantitative proteomic analysis identified 340 differentially expressed proteins between A2780 and A2780-DR cells, which involve in diverse cellular processes, including metabolic process, cellular component biogenesis, cellular processes and stress responses. Expression levels of Ras-related proteins Rab 5C and Rab 11B in A2780-DR cells were lower than those in A2780 cells as confirmed by real-time quantitative PCR and western blotting. The short hairpin (sh)RNA-mediated knockdown of Rab 5C in A2780 cells resulted in markedly increased resistance to cisplatin whereas overexpression of Rab 5C in A2780-DR cells increases sensitivity to cisplatin, demonstrating that Rab 5C-dependent endocytosis plays an important role in cisplatin resistance. Our results also showed that expressions of glycolytic enzymes PKM, GPI, Aldolase, LDH, and PGK were down-regulated in drug resistant cells, indicating drug resistance in ovarian cancer is directly associated with a decrease in glycolysis. Furthermore, it was found that glutathione reductase were up-regulated in A2780-DR, while vimentin, HSP90, and Annexin A1 and A2 were down-regulated. Taken together, our results suggest that drug resistance in ovarian cancer cell line A2780 is caused by multifactorial traits, including the down-regulation of Rab 5C-dependent endocytosis of cisplatin, glycolytic enzymes and vimentin, and up-regulation of antioxidant proteins, suggesting Rab 5C is a potential target for treatment of drug-resistant ovarian cancer. This constitutes a further step towards a comprehensive understanding of drug resistance in ovarian cancer.

Project description:Time-course and concentration-effect experiments with multiple time points and drug concentrations provide far more valuable information than experiments with just two design-points (treated vs. control), as commonly performed in most microarray studies. Analysis of the data from such complex experiments, however, remains a challenge. Here we present a semi-automated method for fitting time profiles and concentration-effect patterns, simultaneously, to gene expression data. The submodels for time-course included exponential increase and decrease models with parameters such as initial expression level, maximum effect, and rate-constant (or half-time). The submodel for concentration-effect was a 4-parameter Hill model. The method was applied to an Affymetrix HG-U95Av2 dataset consisting of 51 arrays. The specific study focused on the effects of two platinum drugs, cisplatin and oxaliplatin, on A2780 human ovarian carcinoma cells. Replicates were available at most time points and concentrations. Eighteen genes were selected; time-course and concentration-effect were modeled simultaneously. Comparisons of model parameters helped distinguish genes with different expression patterns between the two drug treatments. This overall paradigm can help in understanding the molecular mechanisms of the agents, and the timing of their actions. Experiment Overall Design: For the time-course experiments, samples were exposed to IC90 concentrations of oxaliplatin (32 Î¼M) or cisplatin (25 Î¼M) for 2 hours, and then allowed to grow in drug free medium. Cells were harvested and processed at the following times: before treatment, immediately after treatment (0 h), and at 2 h, 6 h, 16 h and 24 h after treatment. Control experiments were done following a similar design, but with exposure to drug-free medium. For the concentration-effect experiments, samples were treated with specific growth-inhibitory concentrations of cisplatin or oxaliplatin for 2 hours. The previously-estimated IC10, IC25, IC50, IC75 and IC90 concentrations (for 2 hr drug exposure; 72 hr total growth) for cisplatin and oxaliplatin growth inhibition of A2780 were 2.6, 4.0, 6.4, 12 and 25 Î¼M and 2.8, 4.8, 8.5, 17 and 32 Î¼M respectively. Cells were harvested and processed at 16 h after completion of treatment

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Differences in gene expression in A2780C20 vs. A2780

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