Abstract 1984: Crosstalk between sirtuins and TGF-β signaling suppresses liver cancer

Background: Cancer stem cells that escape suppression by key pathways such as TGF-β represent one of the mechanisms for poor prognosis in hepatocellular cancer (HCC). Our mouse models with disruption of TGF-β signaling (β2SP+/-/Smad3+/-) develop HCC and phenocopy an epigenetically human cancer stem cell disorder, providing clues towards the role of TGF-β in the switch in stem cell transformation to HCC. An examination of HCC genomics revealed a surprising and strong correlation between TGF-β and Sirtuins (SIRTs) expression. SIRTs are also implicated in cancer stem cell and HCC suppression. Here we hypothesized that the TGF-β pathway harnesses Sirtuin members to maintain stem cell homeostasis, which may mediate the progression of HCC. Methods: Overall Survival (OS) analysis was carried out by using early-stage HCC (TCGA, Firehose Legacy, stage N1, n=186) from cBioportal. ChIP assay was performed in HepG2 cells using anti-Smad3 and normal rabbit IgG. Biotinylated SIRT6 promoter with/without SMAD binding sites was used as probes to pull down the DNA-interacting proteins in HepG2 cells treated with/without TGF-β for 2h. Results: Analysis of TCGA HCC dataset (cBioportal, stage N1, n=186) indicated reduced OS for HCC patients with decreased SIRT6 together with loss of SPTBN1 in the early stage (Median survival months: 40.37 vs 83.18, p=0.0417). • Chip-qPCR and the DNA-protein pulldown assay revealed that Smad3 positively upregulates the SIRT6 mRNA expression (Smad3 vs IgG, SBE1: 3.27±0.53 vs 0.99±0.01, p