Abstract:

Objective To investigate the effect of excretory/secretory proteins from Trichinella spiralis on apoptosis of NCI-H446 small-cell lung cancer cells. Methods Trichinella spiralis muscle stage larvae （5×106/ml）were cultured in culture media for 24 h， the excretory/secretory proteins were collected from the supernatant of culture media. NCI-H446 small-cell lung cancer cells（No. A05） were randomly divided into three groups： experiment group（A）， standard control group （apoptosis group， B）， and control group （C）. NCI-H446 cells in groups A and B were cultured with 0.3 mg/ml T. spiralis excretory/secretory proteins， and 6.4 μg/ml cisplatin for 24 h， respectively. NCI-H446 cells of group C were cultured for 24 h without any treatment. The expression of Bcl-2， Fas and Fasl mRNA was detected by RT-PCR. C-myc protein expression level was examined by Western blotting and immunofluorescence assay. Results The level of Bcl-2 mRNA was lowest in group A（0.575±0.047） , Bcl-2 mRNA level in group C （0.975±0.069） was higher than that of group B （0.850±0.073）（P<0.05）. Fas mRNA level was highest in group A（0.975±0.115）， followed by group B（0.817±0.121） and group C（0.769±0.061）（P<0.05）. The level of Fasl mRNA in groups A， B， and C was 0.669±0.051， 0.787±0.124， and 0.875±0.125， respectively（P<0.05）. Fas/Fasl mRNA ratio in groups A， B， and C was 1.475，1.038，and 0.878. Western blotting showed that the expression of C-myc protein in group C（1.172±0.026） was highest， followed by group B （1.074±0.069） and A（0.566±0.054）（P<0.05）. Immunofluorescence test indicated that the C-myc protein was found in the cytoplasm and the nucleus 24 h after treated with 0.3 mg/ml T. spiralis excretory/secretory proteins and 6.4 μg/ml cisplatin. Conclusion Trichinella spiralis excretory/secretory proteins may inhibit apoptosis of NCI-H446 small-cell lung cancer cells by reducing the apoptosis protein C-myc and Bcl-2 mRNA levels， and causing the increase of Fas/Fasl mRNA ratio.

Key words: Trichinella spiralis, Excretory/secretory protein, Apoptotic gene, Small-cell lung cancer cell, NCI-H446, lApoptotic protein