[Mechanisms of in vitro anti-tumor effects of a Newcastle disease virus].

OBJECTIVE

To obtain Newcastle disease virus (NDV) strains with high in vitro anti-tumor effect for construction of recombinant NDV for clinical therapy.

METHODS

We used MTr [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphemyltetra-zolium Bromide] assay to examine the anti-tumor effect on A549 and SMMC7721 cells infected by nearly 50 NDV strains. Several assays were used to analyze the apoptosis induced by NDV infection. These assays included: (1) Morphological analysis; (2) Hoechst? fluorescence dye testing; (3) Flow cytometric analysis, and (4) Western blot.

RESULTS

We obtained an NDV FMW strain that inhibited cell growth up to 60% at 48 h postinfection with an MOI (multiplex of infection) of 20. NDV-FMW could elicit apoptosis of infected tumor cells in a dose- and time-dependent manner. We observed the infected A549 and SMMC7721 cells with condensed and fragmented chromatin at 48 h postinfection. Apoptosis peak and hypodiploid cells were revealed by proidum iodide (PI) staining and cell cycle was blocked and arrested in G0/G1 phase in tested cells. Furthermore, annexin-V/PI staining showed that the apoptotic rates in SMMC7721 cells were 2.1%, 18.5%, 23.8% and 30.4% after treated with 0, 0.2, 2 and 20 MOI NDV-FMW for 48 h respectively. To elucidate the apoptosis pathways induced by NDV-FMW, we detected the expression of active caspase-3 and cleavages of poly(ADP-ribose) polymerase(PARP). We demonstrated that caspase-3 in A549 cells was activated early at 16 h postinfection and PARP was cleaved subsequently.

CONCLUSION

NDV-FMW had strong in vitro anti-tumor effect on A549 and SMMC7721 cells. Apoptosis of tumor cells induced by NDV-FMW via caspase-3 activation and NDV-FMW could be a potential cancer virotherapy agent.