[Effect of CD(40) on the in vitro biological behavior of malignant B lymphocytes].

ABSTRACT

OBJECTIVE: To explore the effect of recombinant human soluble CD(40) ligand (rhsCD(40)L) and CD(40)L cDNA transfected cell (CD(40)L-TC) on the behavior of malignant B lymphocytes, and investigate the possibility of using rhsCD(40)L as a new bio-factor in tumor immunotherapy. METHOD: rhsCD(40)L and CD(40)L-TC were obtained by gene recombinant techniques. Multiple myeloma cell lines, XG2, XG7, U266 and 8226, B-lymphoma cell lines, Raji and Daudi were selected to detect responses to rhsCD(40)L and CD(40)L-TC stimulation. Cell growth curve, cell cycle, early apoptosis as well as membrane surface molecules on these cell lines were analyzed. RESULTS: (1) The expression levels of CD(40) molecule on malignant B lymphocytes showed heterogeneity. High level of CD(40) on XG2, moderate on 8266, Raji, and Daudi, and no expression on U266 and XG7 were detected. The rhsCD(40)L stimulation gave rise to a typical homo-type cell aggregation of XG2 and Daudi. Meanwhile, at least 10 to 20 of CD(40)(+) XG2 or CD(40)(+) Daudi cells were found adherent to one pre-treat ed CD(40)L-TC. (2) Co-incubation with rhsCD(40)L (5 micro g/ml), or CD(40)L-TC (tumor cell CD(40) = 51) resulted in a significant inhibition of in vitro cell growth of XG2, Raji and Daudi, with G(1)-phase arrest for XG2 and G(2)-phase for Raji and Daudi. These two kinds of CD(40) stimulators induced XG2, Raji and Daudi cells to apoptosis in vitro. The apoptotic rate for XG2 was 23.3% (rhsCD(40)L) and 18.8% (CD(40)L-TC), for Daudi 14.2% and 15.9%, and for Raji 11.6% and 8.9% respectively. (3) Phenotype analysis showed that CD(95) expression levels were significantly up-regulated on XG2, Raji and Daudi after stimulation with rhsCD(40)L or CD(40)L-TC, and CD(80) and CD(18) expression levels on Raji were respectively enhanced and decreased. CONCLUSION: The abilities to directly inhibit XG2, Daudi and Raji cell proliferation, to induce themapoptosis, as well as to up-regulate immune co-stimulator molecule CD(80) expression on Raji cells would make rhsCD(40)L a potential bio-factor for tumor immuno-therapy.