Down-regulation of miRNA-106b inhibits growth of melanoma cells by promoting G1-phase cell cycle arrest and reactivation of p21/WAF1/Cip1 protein
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Ram Prasad1 and Santosh K. Katiyar1,2,3,4
1 Department of Dermatology, University of Alabama at Birmingham, Birmingham, AL, USA
2 Environmental Health Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
3 Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, USA
4 Birmingham Veterans Affairs Medical Center, Birmingham, AL, USA
Santosh K. Katiyar, email:
Keywords: Melanoma, MicroRNA-106b, cell cycle, tumor xenograft growth, grape seed proanthocyanidins
Received: August 12, 2014 Accepted: September 24, 2014 Published: September 25, 2014
MiR-106b is overexpressed in various types of cancers and is associated with the regulation of the carcinogenic processes. Using RT-PCR, we have identified overexpression of miRNA-106b in various melanoma cell lines (A375, Hs294t, SK-Mel28, SK-Mel 119, Mel 1241, Mel 1011 and Mel 928) as compared to its expression in normal human epidermal melanocytes (NHEM). The overexpression of miR-106b in melanoma cells (A375, Hs294t) was associated with greater cell proliferation capacity than NHEM. Treatment of A375 and Hs294t cells with anti-miR-106b resulted in inhibition of cell proliferation as well as G1-phase arrest. We determined the effects of grape seed proanthocyanidins (GSPs) on the expression of miRNA-106b and its underlying molecular targets. Treatment of A375 and Hs294t cells with GSPs resulted in suppression of the levels of miRNA-106b, cytotoxicity, G1-phase arrest and reactivation of p21/WAF1/Cip1. Dietary GSPs significantly inhibited growth of A375 melanoma cell tumor xenografts in nude mice, which was associated with reduction in the levels of miRNA-106b, tumor cell proliferation and increases in the levels of p21/WAF1/Cip1 protein. These studies suggest that miRNA-106b plays a crucial role in melanoma growth and that GSPs act as an inhibitor of miR-106b thereby blocking melanoma growth in vitro and in vivo models.
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