ABSTRACT
Objective: To explore the effect of the Epstein-Barr virus (EBV) BZLF1 gene on the biological behavior of EBV-negative gas-tric cancer cells and the underlying molecular mechanism. Methods: Lentiviral overexpressing BZLF1 was used to infect AGS and HGC27 gastric cancer cell lines. And the cell proliferation, apoptosis and migration invasive ability, and expression changes of cell sig-naling pathway were detected by CCK8 assay, apoptosis detection, migration and invasion assay, as well as western blot. HGC27 cells overexpressing BZLF1 were injected into the dorsal of NOD/SCID mice to construct xenografts, and the effect of BZLF1 on tumor growth was observed. Results: The expression of BZLF1 protein was significantly up-regulated in AGS-BZLF1 and HGC27-BZLF1 infected by over-expressing BZLF1 lentivirus. The cell proliferation in vitro and the tumorigenic ability in mice were significantly increased (P<0.05). Apoptosis was inhibited by BZLF1 protein, and the apoptotic rate of AGS-BZLF1 and HGC27-BZLF1 was (2.40±0.14)% and (3.90± 0.14)%, which was significantly lower than (5.75±0.35)% and (9.70 ± 0.42)% of AGS and HGC cells (P<0.05); however, there was no sig-nificant change in cell migration and invasion ability. In-depth molecular mechanism studies found that PI3K/AKT signaling pathway was significantly activated with enhanced pAKT and pS6 expression. After blocking the PI3K/AKT signaling pathway with BEZ235 inhibi-tor, the growth of HGC27-BZLF1 and AGS-BZLF1 cells was inhibited. Conclusions: EBV BZLF1 may promote the growth of gastric cancer cells by activating the PI3K/AKT signaling pathway and targeting PI3K/AKT pathway inhibitors, and serve as a promising treatment op-tion for EBV-associated gastric carcinoma.
ABSTRACT
In 2014, The Cancer Genome Atlas firstly classified gastric cancer into four types according to genotype. Epstein-Barr virus (EBV) positive gastric cancer or EBV-associated gastric cancer (EBVaGC) is attracting attention because it is a possibly suitable group for immunotherapy. Among the mutations observed in tumors, such as gastric cancer, p53 mutations are the most frequent. In particular, it occurs more frequently in EBVaGC than in EBV-negative gastric cancer (EBVnGC). Meanwhile, EBV infection is considered as an early event of tumorigenesis. The interactions between wild-type p53 proteins and BZLF1 (Z) proteins are essential in maintaining the latent state of EBV infection and promoting early replication. In the latter stages of replication, wild-type p53 proteins are degraded through the ubiquitination of some viral molecules. These findings may indicate the importance of wild-type p53 genes in EBVaGC formation. Inflammatory responses induced by EBV infection, tumor with a large number of lymphocyte infiltration, genome high mutation, and PD-L1 amplification make it possible to become the appropriate group of immunotherapy, which also illustrate that the important role of immune microenvironment during tumor progression. In EBVnGC, extremely high levels of p53 mutation were observed because of several associated factors, and the p53 protein encoded by the mutant p53 gene lost its antitumor function after tumorigenesis. In this review, the possible mechanisms of rare p53 mutation in EBVaGC are summarized.