Clinical impact of serum survivin positivity and tissue expression of EBV-encoded RNA in diffuse large B-cell lymphoma patients treated with rituximab–CHOP
EBV-associated gastric carcinoma is a distinct subset of gastric carcinoma infected with EBV, which shows latency I type expression of EBV latent genes (EBNA1, EBER, BARF0, and LMP2A). To clarify the role of EBV in this type of gastric carcinoma, the cell biological characteristics (growth, apoptosis, and migration) were evaluated in gastric carcinoma cell lines (MKN-1, TMK1, MKN-74 and MKN-7) with and without infection of recombinant EBV harboring the neomycin resistance gene. The infection reiterated the latency I type infection, and the only difference observed in EBV-infected gastric carcinoma cell lines was the resistance to serum deprivation-induced apoptosis. Comparative analyses of transcripts of apoptosis-associated genes in MKN-1 and EBV-MKN-1 and subsequent quantitative reverse transcription-PCR analysis showed up-regulation of the cellular survivin gene in EBV-infected gastric carcinoma cell lines. Small interfering RNA-mediated knockdown of survivin increased apoptosis in EBV-MKN-1 to the level of the original MKN-1 cells. Transfection of EBV-latent genes into MKN-1 showed that LMP2A, but not EBNA1, EBER, or BARF0, up-regulated survivin gene expression. LMP2A-mediated survivin up-regulation in gastric carcinoma cells was inhibited with a nuclear factor-kappaB (NF-kappaB) inhibitor, Bay 11-7082. In parallel with these findings in vitro, survivin expression was frequent in carcinoma tissues of gastric carcinoma by immunohistochemistry, and significantly more in EBV-associated gastric carcinoma (12 of 13) than in EBV-negative gastric carcinoma in the advanced stage (P = 0.0307). Thus, EBV uses its latent protein, LMP2A, to activate the NF-kappaB-survivin pathway to rescue EBV-infected epithelial cells from serum deprivation, and up-regulation of survivin may play a role in the progression of this specific type of gastric carcinoma infected with EBV.