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Although the baculovirus-mediated foreign protein expression system has been extensively documented, system investigation of the optimal infection conditions remains elusive. In this study, a recombinant baculovirus vBmBacJS13-egfp was applied for systematic infection of Bombyx mori nucleopolyhedrovirus (BmNPV). We revealed that incubation time and multiplicity of infection (MOI) were the crucial factors affecting the efficiency of virus infection and protein expression. Given the appropriate MOI, BmNPV infection efficiency was increased with elongation of incubation time; the optimal incubation time for BmNPV entry into host cells was about 4 h. Alternatively, an increasing MOI could shorten the incubation time of virus invasion to achieve similar infection efficiency and heterogenous proteins expression levels. This study laid a foundation for the study of the functional genome of BmNPV and provided important parameters for significant improvement on the expression level of heterogenous proteins using the BmNPV-cell expression system.

This study investigated the anticancer effect and mechanism of salinomycin, a selective inhibitor of cancer stem cell, on human ovarian cancer cell line OV2008 in vitro and in vivo. The growth inhibitory effect of salinomycin on ovarian cancer cell line OV2008 was determined by measuring cell viability using the resazurin reduction assay. Apoptotic nuclear morphology was visualized by 4,6-diamino-2-phenylindole staining technique. The percentages of apoptotic cells and cell cycle parameters were detected by flow cytometry. The activity of p38 mitogen-activated protein kinase (p38 MAPK) was analyzed by Bio-Plex phosphoprotein assay. In vivo activity of salinomycin was assayed through tumor growth. Salinomycin caused concentration- (0.01-200 μM) and time-dependent (24-72 h) growth inhibitory effects in OV2008. Cell nuclear morphology observations showed that salinomycin-treated OV2008 cells displayed typical apoptotic characteristics. Salinomycin significantly increased the percentages of apoptotic cells in OV2008, showing a concentration- and time-dependent manner. There was no cell cycle arrest in the G1/G0, S, and G2/M phases between salinomycin-treated cells and control cells. Salinomycin also enhanced the phosphorylation of p38 MAPK. Moreover, salinomycin significantly inhibited the growth of the ovarian xenograft tumors. Salinomycin exhibited significant growth inhibition and induction of apoptosis in the human ovarian cancer cell line OV2008. The data suggested that salinomycin-induced apoptosis in OV2008 might be associated with activating p38 MAPK and merits further investigations.