Regulation of cell cycle checkpoint kinase WEE1 by miR-195 in malignant melanoma

Abstract

WEE1 kinase has been described as a major gate keeper at the G2 cell cycle checkpoint and to be involved in tumour progression in different malignant tumours. Here we analysed the expression levels of WEE1 in a series of melanoma patient samples and melanoma cell lines using immunoblotting, quantitative real-time PCR and immunohistochemistry. WEE1 expression was significantly downregulated in patient samples of metastatic origin as compared with primary melanomas and in melanoma cell lines of high aggressiveness as compared with cell lines of low aggressiveness. Moreover, there was an inverse correlation between the expression of WEE1 and WEE1-targeting microRNA miR-195. Further analyses showed that transfection of melanoma cell lines with miR-195 indeed reduced WEE1 mRNA and protein expression in these cells. Reporter gene analysis confirmed direct targeting of the WEE1 3' untranslated region (3'UTR) by miR-195. Overexpression of miR-195 in SK-Mel-28 melanoma cells was accompanied by WEE1 reduction and significantly reduced stress-induced G2-M cell cycle arrest, which could be restored by stable overexpression of WEE1. Moreover, miR-195 overexpression and WEE1 knockdown, respectively, increased melanoma cell proliferation. miR-195 overexpression also enhanced migration and invasiveness of melanoma cells. Taken together, the present study shows that WEE1 expression in malignant melanoma is directly regulated by miR-195. miR-195-mediated downregulation of WEE1 in metastatic lesions may help to overcome cell cycle arrest under stress conditions in the local tissue microenvironment to allow unrestricted growth of tumour cells.

microRNA-195 functions as a tumor suppressor by inhibiting CBX4 in hepatocellular carcinoma

“…miR-195 has been shown to block the G 1 /S transition of the cell cycle by regulating the expression of CCNd1/3, CdK4/6 and E2F3 (12,16) and to suppress tumor development by targeting BCL-2 and BCL-w (13,34). miR-195 directly regulates WEE1 expression in malignant melanoma (35), but as yet, the exact regulatory mechanisms of miR-195 in HCC development have not been explored.…”

Downregulation of miR-195 promotes prostate cancer progression by targeting HMGA1

“…For example, it is upregulated in metastatic melanoma (10) and some cases of lung cancer (16), and hepatocellular carcinoma (17). By contrast, it is preferentially downregulated in breast cancer (18), gastric cancer (17,19), colorectal cancer (20)(21)(22), and bladder cancer (23,24).…”

“…The sequence of mature miR-195 is conserved across mammalian species (8). miR-195 has been reported to be deregulated in certain types of cancer, including upregulation in chronic and acute lymphocytic leukemia (9) and metastatic melanoma (10) but is downregulated in adrenocortical, hepatocellular carcinoma and squamous cell carcinoma (11)(12)(13). However, the exact role of miR-195 in PCa remains elusive.…”

Specific c-Jun target genes in malignant melanoma

“…The enrichment of DNA fragments displayed as peaks in the promoter/enhancer regions of specific target genes (ENCODE) were localized to the promoter/enhancer regions of FosB, NFATC2, WEE1, PVR, MAP1LC3B and LGALS3 [17][18][19][20][21][22] ( Fig. 2, Table 2).…”