Cross-validation of genes potentially associated with overall survival and drug resistance in ovarian cancer.

Ovarian cancer is the leading cause of death among malignancies of the female reproductive system. The 5-year survival rates of ovarian cancer (OC) patients are very poor as a result of recurrent disease and emergence of drug resistance; thus, studies to find predictive markers and factors for drug resistance are ongoing. In the present study, based on the microarrays from The Cancer Genome Atlas (TCGA), and the Gene Expression Omnibus (GEO) profiles covering 1648 OC patients, 11 out of 136 genes that were found to be significantly dysregulated in OC were associated with overall survival (OS) in 489 OC patients of the TCGA cohort. Of these genes, CRISP3, LYVE1, OVGP1 and BCHE were identified as independent prognostic factors, with decreased expression of the first three genes predicting shorter OS, and decreased BCHE predicting longer OS. OVGP1, BCHE and further two genes, CKAP2 and CLDN10, were consistently and remarkably associated with OS when the number of patients increased from 489 to 1583, with increased CKAP2 and decreased CLDN10 predicted shorter OS; combining the four genes provided better predictions. Associations among the four genes with OS in subgroups of OC were further verified. Downregulation of OVGP1 was significantly associated with shorter OS in all subgroups of OC patients, including subgroups of 752 patients treated with chemotherapy regimens containing taxol, 763 with both platin and taxol, 1364 with platin, 371 patients with grade 1-2 disease, 968 with grade 3 disease, 1148 with stage III-IV disease, and 439 with TP53 mutations. In addition, CKAP2 expression was significantly associated with shorter OS in 515 OC patients who had low CA125 levels. Furthermore, comprehensive analyses that including RT-qPCR, bioinformatics analysis and clinical data revealed an association of CKAP2, BCHE, CLDN10 and OVGP1 with drug resistance in OC. The genes identified in the present study might be prognostic factors as well as potential therapeutic targets in the treatment of OC.