Sorafenib is a multi-
kinase inhibitor and one of the few systemic treatment options for patients with advanced
hepatocellular carcinomas (HCCs). Resistance to
sorafenib develops frequently and could be mediated by the
nicotinamide adenine dinucleotide (
NAD)-dependent deacetylase
sirtuin (
SIRT)1. We aimed to test whether
sorafenib efficacy is influenced by cellular
NAD levels and
NAD-dependent
SIRT1 function. We analyzed
sorafenib effects on apoptosis induction,
NAD salvage, mitochondrial function, and related signaling pathways in HCC cell lines (HepG2, Hep3B, und HUH7) overexpressing
SIRT1 or supplemented with the
NAD metabolite
nicotinamide mononucleotide (NMN) compared to controls. Treatment of HCC cell lines with
sorafenib dose-dependently induced apoptosis and a significant decrease in cellular
NAD concentrations. The
SIRT1 protein was downregulated in HUH7 cells but not in Hep3B cells. After
sorafenib treatment, mitochondrial respiration in permeabilized cells was lower,
citrate synthase activity was attenuated, and cellular
adenosine triphosphate (
ATP) levels were decreased. Concomitant to increased phosphorylation of
adenosine monophosphate (
AMP)-activated protein kinase (AMPK),
sorafenib treatment led to decreased activity of the mechanistic target of
rapamycin (mTOR), indicative of energy deprivation. Transient overexpression of
SIRT1, as well as
NAD repletion by NMN, decreased
sorafenib-induced apoptosis. We can, therefore, conclude that
sorafenib influences the
NAD/
SIRT1/AMPK axis. Overexpression of
SIRT1 could be an underlying mechanism of resistance to
sorafenib treatment in HCC.