Interferon‐alpha‐induced hepatitis C virus clearance restores p53 tumor suppressor more than direct‐acting antivirals

Abstract

The mechanism why hepatitis C virus (HCV) clearance by direct‐acting antivirals (DAAs) does not eliminate the risk of hepatocellular carcinoma (HCC) among patients with advanced cirrhosis is unclear. Many viral and bacterial infections degrade p53 in favor of cell survival to adapt an endoplasmic reticulum (ER)‐stress response. In this study, we examined whether HCV clearance by interferon‐alpha or DAAs normalizes the ER stress and restores the expression of p53 tumor suppressor in cell culture. We found that HCV infection induces chronic ER stress and unfolded protein response in untransformed primary human hepatocytes. The unfolded protein response induces chaperone‐mediated autophagy (CMA) in infected primary human hepatocytes and Huh‐7.5 cells that results in degradation of p53 and induced expression of mouse double minute 2 (Mdm2). Inhibition of p53/Mdm2 interactions by small molecule (nutlin‐3) or silencing Mdm2 did not rescue the p53 degradation, indicating that HCV infection induces degradation of p53 independent of the Mdm2 pathway. Interestingly, we found that HCV infection degrades p53 in a lysosome‐dependent mechanism because lysosome‐associated membrane protein 2A silencing restored p53 degradation. Our results show that HCV clearance induced by interferon‐alpha‐based antiviral therapies normalizes the ER‐stress response and restores p53, whereas HCV clearance by DAAs does neither. We show that decreased expression of p53 in HCV‐infected cirrhotic liver is associated with expression of chaperones associated with ER stress and the CMA response. Conclusion: HCV‐induced ER stress and CMA promote p53 degradation in advanced liver cirrhosis. HCV clearance by DAAs does not restore p53, which provides a potential explanation for why a viral cure by DAAs does not eliminate the HCC risk among patients with advanced liver disease. We propose that resolving the ER‐stress response is an alternative approach to reducing HCC risk among patients with cirrhosis after viral cure. (Hepatology Communications 2017;1:256‐269)

<p>Hepatocellular Carcinoma Mechanisms Associated with Chronic HCV Infection and the Impact of Direct-Acting Antiviral Treatment</p>

“…We showed that CMA activation by stress degrades p14ARF, another alternative open reading frame protein (ARF), a tumor suppressor that activates p53. 136 The subsequent publication showed that excessive ER stress induces MDM2-mediated Rb degradation. 137 All these results are consistent with human studies that show more than 70% of HCC cases having alterations in the p53-Rb pathway that leads to mitosis, cell cycle progression, and genomic instability.…”

“…194 We showed that HCV-induced cellular ER stress could activate MDM2 that degrades Rb tumor suppressor independent of p53. 136 A recent report shows that MDM2 can associate with the PRC2 and enhances stemness through chromatin modification independent of p53. 195 This evidence suggests there are many oncogenic pathways that HCV replication probably induces epigenetic cell programing that induces CSCs leading to HCC.…”

“…In addition, our laboratory illustrated that virus-associated ER stress and tumor suppressor loss (p53 and Rb, miR-122 levels) were restored more by IFN-induced HCV clearance than DAAs in cell culture models. 136,137,206 Based on these data, we propose that understanding the impact of viral cure on the resolution of direct hepatic parenchymal injuries and indirect immune restoration may explain as to why specific individuals remain at risk of HCC occurrence and recurrence.…”

Regulation of Autophagy in Cells Infected With Oncogenic Human Viruses and Its Impact on Cancer Development

“…Among Nrf2 target genes, Hsc70 and LAMP2 are upregulated in their transcription, consequently activating CMA (Aydin et al, 2018). The activation of CMA leads to lysosomal degradation of both pro-autophagic protein BECLIN 1, thus impairing autophagy, and the tumor suppressor p53 (Aydin et al, 2017(Aydin et al, , 2018. Accordingly, it has been shown that HCV replication is able to suppress p53 functions and that p53 protein levels are low in HCV-infected explanted livers (Aydin et al, 2017).…”

“…The activation of CMA leads to lysosomal degradation of both pro-autophagic protein BECLIN 1, thus impairing autophagy, and the tumor suppressor p53 (Aydin et al, 2017(Aydin et al, , 2018. Accordingly, it has been shown that HCV replication is able to suppress p53 functions and that p53 protein levels are low in HCV-infected explanted livers (Aydin et al, 2017). Previous studies have reported that CMA compensate impaired autophagy in the cirrhotic liver to promote hepatocellular carcinoma (Chava et al, 2017).…”