Microarray analysis revealed dysregulation of multiple genes associated with chemoresistance to As ₂O ₃ and increased tumor aggressiveness in a newly established arsenic-resistant ovarian cancer cell line, OVCAR-3/AsR

The potential of arsenic trioxide (As ₂O ₃) for use as a novel therapy for ovarian cancer treatment has been increasingly recognized. In this study, we developed an arsenic-resistant OVCAR-3 subline (OVCAR-3/AsR) and aimed to identify the molecular mechanisms and signaling pathways contributing to the development of acquired arsenic chemoresistance in ovarian cancer. OVCAR-3/AsR cells were obtained following continual exposure of parental OVCAR-3 cells to low dose As ₂O ₃ for 12 months. Cytotoxicity of OVCAR-3/AsR cells to As ₂O ₃, paclitaxel and cisplatin was investigated. Cell apoptosis and cell cycle distribution following As ₂O ₃ treatment of OVCAR-3/AsR cells was also analyzed using flow cytometry. Subsequently, cDNA microarray analysis was performed from the RNA samples of OVCAR-3 and OVCAR-3/AsR cells in duplicate experiments. Microarray data were analyzed using Genespring® and Pathway Studio® Softwares. OVCAR-3/AsR cells showed 9-fold greater resistance to As ₂O ₃ and lack of collateral resistance to cisplatin and paclitaxel. Compared with parental OVCAR-3 cells, OVCAR-3/AsR had significantly lower apoptotic rates following As ₂O ₃ treatment. These cells were also arrested at both the S phase and G ₂/M phase of the cell cycle after exposure to high concentrations of As ₂O ₃. Gene expression profiling revealed significant differences in expression levels of 397 genes between OVCAR-3/AsR and OVCAR-3 cells. The differentially regulated transcripts genes have functional ontologies related to continued cancer cell growth, cell survival, tumor metastasis and tumor aggressiveness. Additionally, numerous gene targets of the nuclear factor erythroid 2-related factor 2 (NRF2) transcription factor showed elevated expression in OVCAR-3/AsR cells. Subsequent pathway analysis further revealed a gene network involving interleukin 1-alpha (IL1A) in mediating the arsenic-resistant phenotype. These results showed that changes in multiple genes and an increased in tumor aggressiveness occurred during the development of acquired chemoresistance to As ₂O ₃ in ovarian cancer cells. The functional relevance of these genetic changes should be validated in future studies.