[Biological effects of soluble CD40 ligand on lung cancer cell line A549 and its mechanism].

BACKGROUND & OBJECTIVE: Although the roles of CD40 in B cells have been intensively studied, little is known on the function of CD40 in lung cancer cell lines. This study was to investigate biological effects of soluble CD40 ligand (sCD44L) on lung cancer cell line A549 (CD40 positive), and its possible mechanism. METHODS: A549 cells were co-incubated with sCD40L, cell proliferation was detected by MTT assay and 3H-TdR incorporation method. Immunofluorescence technique and flow cytometry (FCM) were used to evaluate changes in cell phenotypes and cell cycle. Cell apoptosis, and expression changes of Bcl-2 and Bax were observed by FCM, reverse transcriptase-polymerase chain reaction (RT-PCR), and Western blot. RESULTS: Compared with control cells, proliferation of A549 cells co-incubated with sCD40L was inhibited (P< 0.05). Positive rates of cell surface molecules, CD49e, CD54, TNFRI, and CD95L, in A549 cells co-incubated with sCD40L for 72 h were (61.2+/-4.8)%, (31.2+/-6.1)%,(42.7+/-5.9)%, and (38.2+/-3.4)%, respectively, while those in control cells were (34.7+/-2.1)%, (7.1+/-1.6)%, (15.2+/-4.1)%, and (10.1+/-2.3)%, respectively (P< 0.05). However, positive rate of TNFRII in A549 cells co-incubated with sCD40L[(8.7+/-0.8)%] was lower than that in control cells [(58.1+/-3.6)%] (P< 0.05). G1 phase of A549 cells treated with sCD40L for 72 h was (76.0+/-9.1)%, more than that of control cells [(56.7+/-6.9)%], while S phase of sCD40L-treated A549 cells [(10.3+/-5.7)%] was less than that of control cells [(32.7+/-5.5)%]. No significant apoptosis of A549 cells was observed after co-incubated with sCD40L for 72 h, but Bax expression was up-regulated. CONCLUSION: sCD40L may inhibit cell proliferation, cause changes in phenotype and cell cycle of A549 cells, and alter expression of apoptosis-associated gene, such as Bax.