Sorafenib-Induced Apoptosis in Hepatocellular Carcinoma Is Reversed by SIRT1.

Antje Garten,Melanie Penke,Wieland Kiess,Gareth G Lavery,Katarina Kluckova,Theresa Grohmann

doi:10.3390/ijms20164048

Abstract

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.

Highlights

The multikinase inhibitor sorafenib is one of the few systemic treatment options for advanced hepatocellular carcinoma (HCC) and exerts its anti-proliferative and angiogenesis action by blockage of the Rapidly Accelerated Fibrosarcoma (RAF) and vascular endothelial growth factor (VEGF) signaling and promises better survival for patients with advanced hepatocellular carcinoma [1]
We could show that inhibition of nicotinamide phosphoribosyltransferase (NAMPT) activity via its specific inhibitor FK866 induces energy stress leading to apoptosis in HCC cell lines which was associated with adenosine monophosphate (AMP)-activated protein kinase (AMPK)-mediated inhibition of the mechanistic target of rapamycin signaling [9]
Based on our data and given the fact that Sirtuin 1 (SIRT1) could play a role in drug resistance related to its ability to deacetylate tumor suppressors, such as p53 [10], the current study aimed to find out whether sorafenib influences the NAMPT/SIRT1/AMPK signaling pathway and energy metabolism

Summary

Introduction

The multikinase inhibitor sorafenib is one of the few systemic treatment options for advanced hepatocellular carcinoma (HCC) and exerts its anti-proliferative and angiogenesis action by blockage of the Rapidly Accelerated Fibrosarcoma (RAF) and vascular endothelial growth factor (VEGF) signaling and promises better survival for patients with advanced hepatocellular carcinoma [1]. We could show that inhibition of NAMPT activity via its specific inhibitor FK866 induces energy stress leading to apoptosis in HCC cell lines which was associated with adenosine monophosphate (AMP)-activated protein kinase (AMPK)-mediated inhibition of the mechanistic target of rapamycin (mTOR) signaling [9]. We could show that sorafenib treatment of HCC cells led to mitochondrial dysfunction and decreased NAD and adenosine triphosphate (ATP) levels. This was associated with the activation of AMPK and subsequent inhibition of mTOR signaling. Whereas SIRT1 inhibition did not sensitize hepatocarcinoma cell lines to sorafenib, SIRT1 overexpression led to decreased apoptosis after sorafenib treatment via increasing deacetylation of p53 and could, be a potential mechanism for HCC cells to acquire sorafenib resistance

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