ADRB2 signaling promotes HCC progression and sorafenib resistance by inhibiting autophagic degradation of HIF1α

Abstract

Background & aims: Considerable evidence suggests that adrenergic signaling played an essential role in tumor progression. However, its role in hepatocellular carcinoma (HCC) and the underlying mechanisms remain unknown.

Methods: The effect of adrenaline in hepatocarcinogenesis was observed in a classical diethylnitrosamine-induced HCC mouse model. Effects of ADRB2 signaling inhibition in HCC cell lines were analyzed in proliferation, apoptosis, colony formation assays. Autophagy regulation by ADRB2 was assessed in immunoblotting, immunofluorescence and immunoprecipitation assays. In vivo tumorigenic properties and anticancer effects of sorafenib were examined in nude mice. Expression levels of ADRB2 and hypoxia-inducible factor-1α (HIF1α) in 150 human HCC samples were evaluated by immunohistochemistry.

Results: We uncovered that adrenaline promoted DEN-induced hepatocarcinogenesis, which was reversed by the ADRB2 antagonist ICI118,551. ADRB2 signaling also played an essential role in sustaining HCC cell proliferation and survival. Notably, ADRB2 signaling negatively regulated autophagy by disrupting Beclin1/VPS34/Atg14 complex in an Akt-dependent manner, leading to HIF1α stabilization, reprogramming of HCC cells glucose metabolism, and the acquisition of resistance to sorafenib. Conversely, inhibition of ADRB2 signaling by ICI118,551, or knockdown ADRB2 expression, led to enhanced autophagy, HIF1α destabilization, tumor growth suppression, and improved anti-tumor activity of sorafenib. Consistently, ADRB2 expression correlated positively with HIF1α in HCC specimens and was associated with HCC outcomes.

Conclusions: Our results uncover an important role of ADRB2 signaling in regulating HCC progression. Given the efficacy of ADRB2 modulation on HCC inhibition and sorafenib resistance, adrenoceptor antagonist appears to be a putative novel treatment for HCC and chemoresistance.

Lay summary: ADRB2 signaling played an essential role in sustaining hepatocellular carcinoma cell proliferation and survival. ADRB2 signaling negatively regulated autophagy, leading to hypoxia-inducible factor-1α stabilization, reprogramming of hepatocellular carcinoma cells glucose metabolism, and the acquisition of resistance to sorafenib. Adrenoceptor antagonist appears to be a putative novel treatment for hepatocellular carcinoma and chemoresistance.

Keywords: Autophagy; Beta-2 adrenergic receptor; Liver cancer; Sorafenib resistance.