Clinical and biological significance of KISS1 expression in prostate cancer.

For men in the United States, prostate cancer (PCa) is the most frequent malignancy and the second leading cause of cancer mortality. The metastatic spread of PCa is responsible for most deaths related to PCa. Although KISS1 functions as a metastasis suppressor in various cancers, its expression levels and functions in PCa development and progression remain undetermined. The goals of this study were to correlate the expression levels of KISS1 in PCas with clinicopathologic characteristics and to assess the biological relevance of KISS1 to the viability and motility of PCa cells. Strong KISS1 staining was detected in benign prostate tissues, but the staining was weaker in primary and metastatic PCas (both P < 0.001, t-test). Furthermore, the low expression levels of KISS1 in PCas correlated with clinical stage (P < 0.01) and with KISS1R expression (P < 0.001). Overexpression of full-length KISS1 in low KISS1-expressing PC-3M cells, but not KFMΔSS, which lacks the secretion signal sequence, induced re-sensitization of cells to anoikis, although it had no effect on either cell proliferation or apoptosis. Overexpression of KISS1 also suppressed steps in the metastatic cascade, including motility and invasiveness. Moreover, cells overexpressing KISS1 were found to enhance chemosensitivity to paclitaxel. Collectively, our data suggest that KISS1 functions as a metastasis suppressor in PCas and may serve as a useful biomarker as well as a therapeutic target for aggressive PCas.

Kaiso, a transcriptional repressor, promotes cell migration and invasion of prostate cancer cells through regulation of miR-31 expression.

Kaiso, a member of the BTB/POZ zinc finger protein family, functions as a transcriptional repressor by binding to sequence-specific Kaiso binding sites or to methyl-CpG dinucleotides. Previously, we demonstrated that Kaiso overexpression and nuclear localization correlated with the progression of prostate cancer (PCa). Therefore, our objective was to explore the molecular mechanisms underlying Kaiso-mediated PCa progression. Comparative analysis of miRNA arrays revealed that 13 miRNAs were significantly altered (> 1.5 fold, p < 0.05) in sh-Kaiso PC-3 compared to sh-Scr control cells. Real-time PCR validated that three miRNAs (9, 31, 636) were increased in sh-Kaiso cells similar to cells treated with 5-aza-2'-deoxycytidine. miR-31 expression negatively correlated with Kaiso expression and with methylation of the miR-31 promoter in a panel of PCa cell lines. ChIP assays revealed that Kaiso binds directly to the miR-31 promoter in a methylation-dependent manner. Over-expression of miR-31 decreased cell proliferation, migration and invasiveness of PC-3 cells, whereas cells transfected with anti-miR-31 restored proliferation, migration and invasiveness of sh-Kaiso PC-3 cells. In PCa patients, Kaiso high/miR-31 low expression correlated with worse overall survival relative to each marker individually. In conclusion, these results demonstrate that Kaiso promotes cell migration and invasiveness through regulation of miR-31 expression.