PCTAIRE1 regulates p27 stability, apoptosis and tumor growth in malignant melanoma

PCTAIRE1 is a cyclin-dependent kinase family protein that has been implicated in spermatogenesis. Although we recently revealed the function of PCTAIRE1 in tumorigenesis of epithelial carcinoma cells, its tumorigenic function in melanoma remains unclear. Interrogation of the Oncomine database revealed that malignant melanoma showed up-regulation of PCTAIRE1 mRNA compared to normal skin and benign melanocytic nevus tissues. In the melanoma cell lines A2058 and SK-MEL-28, PCTAIRE1 gene knockdown using siRNA or shRNA diminished melanoma cell proliferation as assessed by cellular ATP levels, cell counting and clonogenic assays. Moreover, FACS analyses of annexin V-PI staining and DNA content showed that PCTAIRE1 knockdown caused apoptosis in A2058 cells. In contrast, PCTAIRE1 does not appear to be involved in the proliferation of immortalized human keratinocyte HaCaT cells. Depletion of PCTAIRE1 by siRNA/shRNA led to p27 accumulation in melanoma cells but not HaCaT cells. In tumor xenografts of melanoma A2058 cells, conditional knockdown of PCTAIRE1 restored p27 protein expression and suppressed tumor growth. Our findings reveal a crucial role for PCTAIRE1 in regulating p27 protein levels and tumor growth in melanoma cells, suggesting that PCTAIRE1 could provide a target for melanoma treatment.