Hepatocellular carcinoma (HCC) is the third most common cause of cancer related death worldwide. One third of patients with cirrhosis will develop HCC, thus comprising a well-characterized population at high-risk for the development of this deadly, yet potentially preventable cancer. Vitamin D (VD) has been implicated in the prevention of multiple cancers- some with inactivation of TGF-beta signaling. Recently, inactivation of TGF-beta signaling has been associated with HCC. The identification of subgroups of patients responsive to treatment is vital for preventing this disease effectively. In an effort to understand the role of Vit D in HCC and to identify clear responders, we analyzed the role of Vit D in the context of TGF-beta inactivation.

Methods: The effect of calcitriol on cell proliferation was measured in HCC cell lines as well as in Hep-G2 cells that were knocked down to the adaptor protein β2-spectrin (Spnb2). To evaluate in vivo effects of VD on animals predisposed to developing liver cancer, Spnb2+/ mice were fed with special diets containing 1000 IU VD/kg/D or 10,000 IU VD/kg/D. After 6 weeks, the animals were euthanized and hepatocyte proliferation and the content of fat in the liver were analyzed through Ki67 staining and oil red staining, respectively. The expression of cyclin D1 was evaluated by Western blotting (WB). Lastly, liver samples from patients with HCC who had received VD supplementation in the diet were also evaluated by immunohistochemistry.

Results: We observed a dramatic response to treatment with calcitriol as indicated by a significant increase in the expression of CYP24A1. Additionally, treatment with VD and calcitriol suppressed the growth of HCC cell lines. Absence of Spnb2 caused more prominent suppression of the growth of Hep-G2. From our animal studies we found that steatosis and hepatocyte proliferation were higher in Spnb2+/ mice fed with a low dose of VD, and that the high dose VD significantly reduced both parameters. The increased proliferation in Spnb2+/ mice fed with a low dose of VD was associated with higher levels of cyclin D1 expression, which was restored the level almost to that seen in the wild type mice with the higher dose of VD. Lastly, VD supplementation to patients with HCC was associated with higher expression of β2-spectrin (p<.0001) and TGFBRII (p=.013) compared with that of patients who did not receive the supplement.

Conclusions: VD suppresses the proliferation of several HCC cell lines, and in agreement with this, high doses of VD in the diet suppress hepatocyte proliferation and steatosis in the HCC prone Spnb2+/ mice. Our data also indicate that VD administration appears to restore the expression of key cell cycle proteins even in the setting of TGF-β signaling disruption. Taken together, these preliminary results suggest that VD treatment strategies could potentially be pivotal in preventing obesity-induced HCC.

Citation Format: Lior H. Katz, Vivek Shukla, Sara Peleg, Kirti shetty, Jian Chen, Steven Curley, Powel H. Brown, Lopa Mishra. Vitamin D as a chemoprophylactic agent for liver cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3692. doi:10.1158/1538-7445.AM2013-3692