Oncolytic Virus Senecavirus A Inhibits Hepatocellular Carcinoma Proliferation and Growth by Inducing Cell Cycle Arrest and Apoptosis.

Background and Aims: Hepatocellular carcinoma (HCC) is a highly aggressive tumor with limited treatment options and high mortality. Senecavirus A (SVA) has shown potential in selectively targeting tumors while sparing healthy tissues. This study aimed to investigate the effects of SVA on HCC cells in vitro and in vivo and to elucidate its mechanisms of action. Methods: The cell counting kit-8 assay and colony formation assay were conducted to examine cell proliferation. Flow cytometry and nuclear staining were employed to analyze cell cycle distribution and apoptosis occurrence. A subcutaneous tumor xenograft HCC mouse model was created in vivo using HepG2 cells, and Ki67 expression in the tumor tissues was assessed. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay and hematoxylin and eosin staining were employed to evaluate HCC apoptosis and the toxicity of SVA on mouse organs. Results: In vitro, SVA effectively suppressed the growth of tumor cells by inducing apoptosis and cell cycle arrest. However, it did not have a notable effect on normal hepatocytes (MIHA cells). In an in vivo setting, SVA effectively suppressed the growth of HCC in a mouse model. SVA treatment resulted in a significant decrease in Ki67 expression and an increase in apoptosis of tumor cells. No notable histopathological alterations were observed in the organs of mice during SVA administration. Conclusions: SVA inhibits the growth of HCC cells by inducing cell cycle arrest and apoptosis. It does not cause any noticeable toxicity to vital organs.

Autophagy-related protein 5 (ATG5) interacts with bone marrow stromal cell antigen 2 (BST2) to stimulate HBV replication through antagonizing the antiviral activity of BST2.

Hepatitis B virus (HBV) infection is a major global health burden with 820 000 deaths per year. In our previous study, we found that the knockdown of autophagy-related protein 5 (ATG5) significantly upregulated the interferon-stimulated genes (ISGs) expression to exert the anti-HCV effect. However, the regulation of ATG5 on HBV replication and its underlying mechanism remains unclear. In this study, we screened the altered expression of type I interferon (IFN-I) pathway genes using RT² Profiler™ PCR array following ATG5 knock-down and we found the bone marrow stromal cell antigen 2 (BST2) expression was significantly increased. We then verified the upregulation of BST2 by ATG5 knockdown using RT-qPCR and found that the knockdown of ATG5 activated the Janus kinase/signal transducer and activator of transcription (JAK-STAT) signaling pathway. ATG5 knockdown or BST2 overexpression decreased Hepatitis B core Antigen (HBcAg) protein, HBV DNA levels in cells and supernatants of HepAD38 and HBV-infected NTCP-HepG2. Knockdown of BST2 abrogated the anti-HBV effect of ATG5 knockdown. Furthermore, we found that ATG5 interacted with BST2, and further formed a ternary complex together with HBV-X (HBx). In conclusion, our finding indicates that ATG5 promotes HBV replication through decreasing BST2 expression and interacting with it directly to antagonize its antiviral function.

UMP-CMP kinase 2 inhibits ZIKV replication through activation of type I IFN signaling pathway.

Cytidine/uridine monophosphate kinase 2 (UMP-CMP kinase 2, CMPK2) has been reported as an antiviral interferon-stimulated gene (ISG). We previously observed that the expression of CMPK2 was significantly upregulated after Zika Virus (ZIKV) infection in A549 cells. However, the association and the underlying mechanisms between CMPK2 induction and ZIKV replication remain to be determined. We investigated the induction of CMPK2 during ZIKV infection and the effect of CMPK2 on ZIKV replication in A549, U251, Vero, IFNAR-deficient U5A and its parental 2fTGH cells, Huh7 and its RIG-I-deficient derivatives Huh7.5.1 cells. The activation status of Jak-STAT signaling pathway was determined by detecting the phosphorylation level of STAT1, the activity of interferon stimulated response element (ISRE) and the expression of several interferon stimulated genes (ISGs). We found that ZIKV infection induced CMPK2 expression through an IFNAR and RIG-I dependent manner. Overexpression of CMPK2 inhibited while CMPK2 knockdown promoted ZIKV replication in A549 and U251 cells. Mechanically, we found that CMPK2 overexpression increased IFNß expression and activated Jak/STAT signaling pathway as shown by the increased level of p-STAT1, enhanced activity of ISRE, and the upregulated expression of downstream ISGs. These findings suggest that ZIKV infection induced CMPK2 expression, which inhibited ZIKV replication and serves as a positive feedback regulator for IFN-Jak/STAT pathway.