Expression of integrin α-6 is associated with multi drug resistance and prognosis in ovarian cancer.

Ovarian cancer is a serious threat to women's health. Multidrug resistance is a major cause of post-treatment relapse, metastasis, and even mortality. This characteristic severely restricts the survival of patients with ovarian cancer. Integrin α-6 (ITGA6) is a member of the adhesion molecule family that conducts signals through interactions between the extracellular domain and the matrix, serving important roles in cell adhesion-mediated drug resistance, which is considered to have a critical function in ovarian cancer drug resistance. The association between ITGA6 and ovarian cancer multidrug resistance has been investigated only rarely, to the best of our knowledge. Using RT-qPCR and immunohistochemistry, it was identified that ITGA6 is a central drug resistance gene, and that its expression was upregulated in cisplatin-resistant SKOV3 (SKOV3/DDP2), cisplatin-resistant A2780 (A2780/DDP) cells, and in 54 cases of drug-resistant tissues, as compared with in the controls. Furthermore, bioinformatics and text mining performed by Coremine Medical (http://www.coremine.com/medical/#search) confirmed that ITGA6 was significantly associated with ovarian cancer and drug resistance. Additionally, the high expression of ITGA6 is associated with a poor outcome. The present study provides the basis for further understanding the role of ITGA6 in the regulation of drug resistance in ovarian cancer, and demonstrates that it could be a potential marker for the prognosis of ovarian cancer.

Microarray-based identification of genes associated with prognosis and drug resistance in ovarian cancer.

The outcome for patients with ovarian cancer (OC) is poor because of drug resistance. Therefore, identification of factors that affect drug resistance and prognosis in OC is needed. In the present study, we identified 131 genes significantly dysregulated in 90 platinum-resistant OC tissues compared with 197 sensitive tissues, of which 30 were significantly associated with disease-free survival (DFS; n = 16), overall survival (OS; n = 6), or both (n = 8) in 489 OC patients of the The Cancer Genome Atlas cohort. Of these 30 genes, 17 were significantly upregulated and 13 were downregulated in the 90 resistant tissues, and with one exception, all of the up-/downregulated genes in resistant tissues were predictors of shorter DFS or/and OS. LAX1, MECOM, and PDIA4 were independent risk factors for DFS, and KLF1, SLC7A11, and PDIA4 for OS; combining these genes provided more accurate predictions for DFS and OS than any of the genes used individually. We further verified downregulation of PDIA4 protein in 51 specimens of patients with OC (24 drug resistant's and 27 sensitive's), which confirmed that downregulated PDIA4 predicted DFS and OS. PDIA4 also consistently predicted OS in a larger sample of 1656 patients with OC. These 30 genes, particularly the PDIA4, could be therapeutic targets or biomarkers for managing OC.

Low expression of KCNN3 may affect drug resistance in ovarian cancer.

Drug resistance is a principal contributor to the poor prognosis of ovarian cancer (OC). Therefore, identifying factors that affect drug resistance in OC is critical. In the present study, 51 OC specimens from lab collections were immunohistochemically tested, public data for 489 samples from The Cancer Genome Atlas cohort and 1,656 samples from the Kaplan­Meier Plotter were downloaded, and data were retrieved from Oncomine. It was identified that the mRNA and protein expression of the potassium calcium­activated channel subfamily N member 3 (KCNN3) was markedly lower in OC tissues compared with normal tissues, and in drug­resistant OC tissues compared with sensitive OC tissues. Low KCNN3 expression consistently predicted shorter disease­free and overall survival (OS). Specifically, low KCNN3 expression predicted shorter OS in 395 patients with low expression levels of mucin­16. There was additional evidence that KCNN3 expression is mediated by microRNA­892b. Furthermore, text mining and analyses of protein and gene interactions indicated that KCNN3 affects drug resistance. To the best of the authors' knowledge, this is the first report to associate KCNN3 with poor prognosis and drug resistance in OC. The present findings indicated that KCNN3 is a potential prognostic marker and therapeutic target for OC.

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.

STROBE-compliant integrin through focal adhesion involve in cancer stem cell and multidrug resistance of ovarian cancer.

Cancer stem cells (CSCs) are considered to be the root of carcinoma relapse and drug resistance in ovarian cancer. Hunting for the potential CSC genes and explain their functions would be a feasible strategy to meet the challenge of the drug resistance in ovarian cancer. In this study, we performed bioinformatic approaches such as biochip data extraction and pathway enrichment analyses to elucidate the mechanism of the CSC genes in regulation of drug resistance. Potential key genes, integrins, were identified to be related to CSC in addition to their associations with drug resistance and prognosis in ovarian cancer. A total of 36 ovarian CSC genes involved in regulation of drug resistance were summarized, and potential drug resistance-related CSC genes were identified based on 3 independent microarrays retrieved from the Gene Expression Omnibus (GEO) Profiles. Pathway enrichment of CSC genes associated with drug resistance in ovarian cancer indicated that focal adhesion signaling might play important roles in CSC genes-mediated drug resistance. Integrins are members of the adhesion molecules family, and integrin subunit alpha 1, integrin subunit alpha 5, and integrin subunit alpha 6 (ITGA6) were identified as central CSC genes and their expression in side population cells, cisplatin-resistant SKOV3 (SKOV3/DDP2) cells, and cisplatin-resistant A2780 (A2780/DDP) cells were dysregulated as measured by real-time quantitative polymerase chain reaction. The high expression of ITGA6 in 287 ovarian cancer patients of TCGA cohort was significantly associated with poorer progression-free survival. This study provide the basis for further understanding of CSC genes in regulation of drug resistance in ovarian cancer, and integrins could be a potential biomarker for prognosis of ovarian cancer.