Abstract: Objective To investigate the effects of LASS2/TMSG1 gene overexpression on proliferation and apoptosis of human lung cancer A549 cells and explore the possible mechanism. Methods We examined LASS2/TMSG1 expression level in a previously constructed A549 cell line overexpressing LASS2/TMSG1 using Western blotting. The proliferation and apoptosis of the cells were detected using colony-forming assay, CCK-8 assay, Hoechst/PI double staining and flow cytometry. Fourteen nude mice were randomized into 2 groups (n=7) to receive subcutaneous injection of A549 cells with or without LASS2/TMSG1 overexpression on the back of the neck, and the cell proliferation in vivo was observed. The expression levels of p38 MAPK protein and p-p38 MAPK protein in the xenografts were detected with Western blotting. ELISA was used to detect the levels of ceramide and p38 MAPK protein in cultured A549 cell supernatants and the xenografts in nude mice. Results Compared with the negative control cells, A549 cells with LASS2/TMSG1 overexpression had significantly lowered proliferation ability in vitro with increased early apoptosis rate (P<0.05), and showed obvious growth inhibition after inoculation in nude mice (P<0.05). Western blotting showed that in both cultured A549 cells and the xenografts in nude mice, LASS2/TMSG1 gene overexpression significantly increased the expression levels of p38 MAPK protein and p-p38 MAPK protein (P<0.05); the results of ELISA also revealed significantly increased levels of ceramide and p38 MAPK protein in the cell supernatant andxenografts as well (P<0.05). Conclusion Overexpression of LASS2/TMSG1 gene can significantly inhibit the proliferation and promote early apoptosis of human lung cancer A549 cells both in vitro and in vivo possibly by upregulating the expressions of ceramide and p38 MAPK protein to activate a signal transduction cascade.

Key words: LASS2/TMSG1; lung cancer; proliferation; apoptosis; ceramide; p38 MAPK