Efficacy and epigenetic interactions of novel DNA hypomethylating agent guadecitabine (SGI-110) in preclinical models of hepatocellular carcinoma

ABSTRACT

Hepatocellular carcinoma (HCC) is a deadly malignancy characterized at the epigenetic level by global DNA hypomethylation and focal hypermethylation on the promoter of tumor suppressor genes. In most cases it develops on a background of liver steatohepatitis, fibrosis, and cirrhosis. Guadecitabine (SGI-110) is a second-generation hypomethylating agent, which inhibits DNA methyltransferases. Guadecitabine is formulated as a dinucleotide of decitabine and deoxyguanosine that is resistant to cytidine deaminase (CDA) degradation and results in prolonged in vivo exposure to decitabine following small volume subcutaneous administration of guadecitabine. Here we found that guadecitabine is an effective demethylating agent and is able to prevent HCC progression in pre-clinical models. In a xenograft HCC HepG2 model, guadecitabine impeded tumor growth and inhibited angiogenesis, while it could not prevent liver fibrosis and inflammation in a mouse model of steatohepatitis. Demethylating efficacy of guadecitabine on LINE-1 elements was found to be the highest 8 d post-infusion in blood samples of mice. Analysis of a panel of human HCC vs. normal tissue revealed a signature of hypermethylated tumor suppressor genes (CDKN1A, CDKN2A, DLEC1, E2F1, GSTP1, OPCML, E2F1, RASSF1, RUNX3, and SOCS1) as detected by methylation-specific PCR. A pronounced demethylating effect of guadecitabine was obtained also in the promoters of a subset of tumor suppressors genes (CDKN2A, DLEC1, and RUNX3) in HepG2 and Huh-7 HCC cells. Finally, we analyzed the role of macroH2A1, a variant of histone H2A, an oncogene upregulated in human cirrhosis/HCC that synergizes with DNA methylation in suppressing tumor suppressor genes, and it prevents the inhibition of cell growth triggered by decitabine in HCC cells. Guadecitabine, in contrast to decitabine, blocked growth in HCC cells overexpressing macroH2A1 histones and with high CDA levels, despite being unable to fully demethylate CDKN2A, RUNX3, and DLEC1 promoters altered by macroH2A1. Collectively, our findings in human and mice models reveal novel epigenetic anti-HCC effects of guadecitabine, which might be effective specifically in advanced states of the disease.

KEYWORDS:

• Decitabine
• DNA methylation
• guadecitabine
• hepatocellular carcinoma (HCC)
• histone macroH2A1
• steatohepatitis

Disclosure of potential conflicts of interest

S. Jueliger, J. Lyons M. Azab and P. Taverna are employees of Astex Pharmaceuticals, Inc. The other authors disclose no potential conflicts of interest.

Funding

PV and MV are supported by Italian Ministry of Health, Bando GR-2010-2311017. MV is supported by a My First Associazione Italiana Ricerca sul Cancro (AIRC) Grant-AIRC Grant No.13419, by UCL and by grants No.LQ1605 from the National Program of Sustainability II (MEYS CR) and FNUSA-ICRC No. CZ.1.05/1.1.00/02.0123 (OP VaVpI). PP is supported by EU-FP7 Grant No. 621364 (TUTIC-Green). This study was funded in part by Astex Pharmaceuticals. We are grateful to SMC Laboratories for assistance with the NASH mouse model, and to Dr. Concetta Panebianco for technical help.

Author contributions

SJ and MV conceived and designed the study. SJ, SC, IP, PP, MS, OLR, MP and FR acquired data. SJ, PT, IP, PP, MS, VP, FV, FC, MA, JL and MV interpreted data. SJ and MV wrote the manuscript. SJ and MV supervised the study. All authors read and approved the manuscript.