Abstract 1619: Preventive effects of vitamin D in liver cancer

Hepatocellular carcinoma (HCC) is the third most common cause of cancer related mortality worldwide. In view of its limited therapeutic options, strategies for HCC prevention are urgently needed. Vitamin D (VD) and calcitriol have anti-proliferative and other anti neoplastic activities. Low levels of VD are associated with increased risk for cancer, and calcitriol can be active agent in cancer treatment. Therefore, VD might be a strong candidate for HCC prevention. We show that vitamin D can prevent the development of HCC in cell lines, reduce proliferation in animal models and modify cell cycle protein levels in human livers. Methods: 1) Hep3B HCC cells were treated with either calcitriol, or two synthetic VD analogs - EB1089 and QW-1624F. Growth was measured using an MTS assay. 2) Livers were harvested from 12 months-old wild-type (WT) mice fed standard Purina chow, and age-matched β2spectrin (≥2SP) +/− mice after 6 weeks of feeding with a semi-purified AIN-93 diet containing 1000 IU VD/kg or 10,000 IU VD/kg. Hepatocyte proliferation (Ki67 staining) and fat content (Oil red staining) were assessed as well as cell cycle proteins (by Western blot). 3) Human liver tissue from healthy and cirrhotic livers as well as from HCC patients were stained for TGF ≤ Receptor II (TBRII) and for β2SP with and without treatment with VD. Results: 1) HCC cell lines - Doses of 10-1000nM of calcitriol or vitamin D analogs suppress the growth of HCC cells. 2) Serum levels of VD in WT and β2SP +/− mice on regular diet were 25.6+/− 2.9 ng/mL and 21.7+/− 8 ng/mL, respectively (p=NS). High dose vitamin D in the diet increased significantly serum levels of vitamin D in β2SP +/− mice to 49.6+/− 12.7 (p=0.0036). Proliferation and steatosis were higher in hepatocytes from β2SP +/− mice fed low dose VD as compared to the wild-type mice fed standard diet. However, high dose VD reduced hepatocyte proliferation and steatosis in β2SP +/− mice. Levels of cyclin D1 were increased in the β2SP +/− mice fed with regular diet as compared to the wild type mice. However, high-dose VD restored the levels of cyclin D1 almost to that of the WT (p=0.069). 3) Normal human hepatocytes have active TGF-β signaling as demonstrated by high levels of β2SP and TBRII staining, while cirrhotic liver cells and HCC cells have reduced β2SP and TBRII staining. VD treatment partially restores TGF-β signaling with similar β2SP and TBRII staining to that in normal hepatocytes. A potential mechanism through KLF-4 modulation may contribute to it. A disappearance of an MRI detected nodule was observed in one of the patients treated with Vitamin D with restoration of TGF-β markers. Conclusions: 1) Calcitriol and its analogs suppress proliferation of HCC cell lines. 2+3) High doses of VD in the diet suppress hepatocyte proliferation and hepatic steatosis in susceptible mice. Possible mechanism can be the effect of VD on cell cycle proteins through the TGF-β pathway as seen in humans. These findings emphasize the use of vitamin D as a novel preventive treatment for HCC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1619. doi:1538-7445.AM2012-1619