3 KLF6 regulates cellular pathways that inhibit tumor cell proliferation, migration, angiogenesis, and invasion,2, 4-7 while enhancing apoptosis8 and differentiation.9 Reduction of KLF6 messenger RNA (mRNA) expression in HCCs due to chronic hepatitis B virus (HBV)10 and hepatitis C virus (HCV)2, 10 is frequent, and correlates with advancing stage; moreover, extremely low KLF6 mRNA levels are

linked to reduced survival.2 GS-1101 mw KLF6 activity in human cancer can be attenuated by loss of heterozygosity,5, 11-14 somatic mutation,11, 12 and promoter methylation.15 Additionally, alternative splicing of KLF6 into an antagonistic splice form, SV1, is increased in HCC10, 16 and other cancers.9, 17-19 Specifically, ratios of SV1/KLF6 in tumors from HBV10 and HCV2, 10, 16 -related HCCs are increased compared to surrounding

tissues. SV1, the major KLF6 splice variant, lacks the DNA binding domain, is pro-proliferative, and facilitates tumor invasion by antagonizing the transactivation of p21 and E-cadherin by KLF6.5, 6 SV1 also displays proapoptotic caspase activity and accelerates degradation of the antiapoptotic protein NOXA.20, 21 Moreover, silencing of SV1 in ovarian cancer models decreases invasiveness and angiogenesis, with reduced VEGF protein.9 Mechanisms driving splicing of KLF6 and accounting for its antagonism of full-length KLF6 are largely unknown. Activation of the Ras oncogene stimulates KLF6 splicing, which promotes proliferation.15, 22 The specific ratio of SV1/KLF6 appears to regulate proliferative and tumorigenic activity, learn more but it is unclear whether the effect is due solely to increased SV1, decreased KLF6, or both. Accordingly, in this study we have first established the clinical relevance of an increasing ratio of SV1/KLF6 as a predictor for HCV-associated

HCC behavior, and then modeled the key features of KLF6 dysregulation in human HCC using mouse models, including loss of KLF6 expression through hepatocyte-specific deletion, increased SV1 through hepatocyte-specific transgene expression, and a combination of the two defects. medchemexpress These findings confirm KLF6 dysregulation in human HCC and provide novel insights into this tumor suppressor gene’s regulation and impact on hepatocarcinogenesis. ALT, alanine transaminase; AST, aspartate transaminase; DEN, diethylnitrosamine; HCC, hepatocellular carcinoma; HCV, hepatitis C virus; LOH, loss of heterozygosity. We analyzed SV1- and KLF6 mRNA levels in 149 HCV-infected human liver samples covering the entire hepatocarcinogenic spectrum: normal liver (n = 9), cirrhosis (n = 9), dysplastic nodules (n = 27), very early HCC (n = 16), early (n = 17), advanced HCC (n = 51), and very advanced HCC (n = 20) as described.