Abstract 892: Vitamin D deficiency regulates TLR7 to promote hepatocellular cancer in TGF-β/Smad3 heterozygous mice

Hepatocellular carcinoma (HCC) is the fifth most common tumor and the third leading cause of cancer-related deaths. Loss of TGF-β signaling has been associated with development of HCC. Cancer preventive effects of Vitamin D (VD) have been implicated in multiple cancers, however a clear role for Vitamin D in specific high risk populations remains undefined for HCC. Therefore, we examined for a potential chemopreventive role of VD in HCC in the context of TGF-β inactivation. Methods: (1) We screened for somatic mutation of the TGF-β pathway and VD related genes in 202 HCCs from The Cancer Genome Atlas (TCGA). (2) Wild type, Sptbn1+/- and Smad3+/- mice were fed with low VD (200 IU VD/kg) or high VD diet (10,000 IU VD/kg) for 9 weeks. Liver tissues were subjected to microarray analyses and further evaluation by quantitative PCR. (3) Wild type, Sptbn1+/- and Smad3+/- mice were injected Diethylnitrosamine (DEN) and at 8 month, 26 mice receiving low VD (200 IU VD/kg) and 26 mice receiving high VD (10,000 IU VD/kg) chow. HCC development was assessed at 4 months after VD treatment. (4) Reverse Phase Protein Array (RPPA) was performed to analyze expression profiles of 164 proteins of mouse liver tumors. (5) Liver samples from patients with HCV cirrhosis receiving VD supplements were examined to evaluate expression of TGF-β, Wnt and VD pathway molecules by immunohistochemistry. Results: (1) We observed a high rate of somatic mutation in TGF-β and VD pathway related genes in the TCGA genomic analysis. (2) None of the VD treated mice developed HCC but high VD treatment increased TLR7 mRNA expression about 3-fold in liver from Smad3+/- mice compared with livers from WT mice. (3) Smad3+/- mice with low VD showed 3-fold larger HCC formation, compared to the high VD group (Smad3+/-) that did not develop significant tumors. However, correction of VD in the Chow after 10 months did not reverse HCC formation. (4) RPPA data revealed that the tumor suppressor protein PDCD4 was reduced in Smad3+/- mice with low VD treatment. However, oncoproteins such as β-catenin, Stat5A and Bcl2-XL were induced in the same sample. (5) Expression of β2SP and TβRII were higher in HCV cirrhosis patients receiving VD supplementation compared to non-treated group. Conclusions: Loss of TGF-β signaling pathway developed HCC and VD deficiency promotes tumor growth in the context of Smad3 disruption potentially through regulation of TLR7 expression. However, after 10 months restoring VD does not have any significant effect on altering tumors. Therefore VD could be a potential candidate for prevention in early identified HCC high risk individuals who has inactivation of TGF-β/Smad3 signaling. Citation Format: Ji-hyun Shin, Lior H. Katz, Nina M. Munoz, Andrea Cortes, Vivek Shukla, Sang-Bae Kim, Franklin Herlong, Keigo Machida, Hidekazu Tsukamoto, Kirti Shetty, Aiwu R. He, Lynt B. Johnson, Asif Rashid, Jian Chen, Ju-Seog Lee, Lopa Mishra. Vitamin D deficiency regulates TLR7 to promote hepatocellular cancer in TGF-β/Smad3 heterozygous mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 892. doi:10.1158/1538-7445.AM2015-892