RESUMEN
There are approximately 250 million people chronically infected with hepatitis B virus (HBV) worldwide. Although HBV is often integrated into the host genome and promotes hepatocarcinogenesis, vulnerability of HBV integration in liver cancer cells has not been clarified. The aim of our study is to identify vulnerability factors for HBV-associated hepatocarcinoma. Loss-of-function screening was undertaken in HepG2 and HBV-integrated HepG2.2.15 cells expressing SpCas9 using a pooled genome-wide clustered regularly interspaced short palindromic repeats (CRISPR) library. Genes whose guide RNA (gRNA) abundance significantly decreased in HepG2.2.15 cells but not in HepG2 cells were extracted using the MAGeCK algorithm. We identified four genes (BCL2L1, VPS37A, INSIG2, and CFLAR) that showed significant reductions of gRNA abundance and thus potentially involved in the vulnerability of HBV-integrated cancer cells. Among them, siRNA-mediated mRNA inhibition or CRISPR-mediated genetic deletion of INSIG2 significantly impaired cell proliferation in HepG2.2.15 cells but not in HepG2 cells. Its inhibitory effect was alleviated by cotransfection of siRNAs targeting HBV. INSIG2 inhibition suppressed the pathways related to cell cycle and DNA replication, downregulated cyclin-dependent kinase 2 (CDK2) levels, and delayed the G1 -to-S transition in HepG2.2.15 cells. CDK2 inhibitor suppressed cell cycle progression in HepG2.2.15 cells and INSIG2 inhibition did not suppress cell proliferation in the presence of CDK2 inhibitor. In conclusion, INSIG2 inhibition induced cell cycle arrest in HBV-integrated hepatoma cells in a CDK2-dependent manner, and thus INSIG2 might be a vulnerability factor for HBV-associated liver cancer.
Asunto(s)
Carcinoma Hepatocelular , Hepatitis B , Neoplasias Hepáticas , Humanos , Virus de la Hepatitis B/genética , Virus de la Hepatitis B/metabolismo , Carcinoma Hepatocelular/genética , ARN Guía de Sistemas CRISPR-Cas , Neoplasias Hepáticas/genética , Línea Celular , Células Hep G2 , ARN Interferente Pequeño/metabolismo , Replicación Viral/genética , Hepatitis B/genética , ADN Viral/genética , Proteínas de la Membrana/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismoRESUMEN
AIM: Patients with chronic hepatitis B (CHB) remain at risk for hepatocellular carcinoma (HCC) even with nucleos(t)ide analog therapy. We evaluated risk factors for HCC development, including serum hepatitis B virus (HBV) RNA, hepatitis B core-related antigen level, and growth differentiation factor 15 (GDF15) level, a predictor of HCC development in patients with chronic hepatitis C. METHODS: We collected clinical data and stored serum from CHB patients without a history of HCC who were receiving nucleos(t)ide analog treatment for more than 1 year and whose HBV DNA level was less than 3.0 log IU/mL. We measured the serum levels of HBV RNA and GDF15. RESULTS: Among 242 CHB patients, 57 had detectable HBV RNA, and GDF15 was quantified in all patients. The median GDF15 level was 0.86 ng/mL. Cox proportional hazards analysis revealed that male sex and higher GDF15, FIB-4 index, alpha-fetoprotein and gamma-glutamyl transpeptidase were independent risk factors for HCC. The presence of HBV RNA above the lower limit of quantification was not a risk factor. When we set cutoff values based on the Youden index, the cumulative incidence of HCC was significantly higher in the male, AFP ≥3.0 ng/mL, gamma-glutamyl transpeptidase ≥22 U/L, FIB-4 index ≥1.93, and GDF-15 ≥1.17 ng/mL groups. In patients with no or more than three of these five risk factors, the 10-year HCC cumulative incidence rates were 0% and 41.0%, respectively. CONCLUSIONS: High serum GDF15 is an independent risk factor for the occurrence of HCC in CHB patients treated with nucleos(t)ide analogs.