Mechanism And Clinical Significance Of Anti-apoptotic Gene BCL2 Expression In Diffuse Large B-Cell Lymphoma

Objective: To investigate the expression and molecular mechanism of BCL2 in the different subdivion of diffuse large B-cell lymphoma.Methods: An immunophenotypical subdivision of 214 cases of diffuse large B-cell lymphoma, NOS(DLBCL) into germinal center-like (GCB)and non- germinal center-like(Non-GCB) was performed on tissue arrays using a combination of antibodies to CD10, BCL6 and MUM1;Meanwhile, expression of BCL2,NF-κB /p65 and Ki-67 protein were evaluated in these two subdivisions;Using a dual-probe fluorescence in-situ hybridization(FISH) assay, we detected t(14;18) BCL2 gene translocation and amplification in these cases. In addition, follow-up data of 49 cases who had been treated with CHOP regimens was compared with the states of expression of BCL2,NF-κB /p65 and Ki-67 as well as t(14;18) BCL2 gene translocation and amplification sundergone ,to evaluate the prognostic significance of these factors in the DLBCL NOS.Results:⑴we detected BCL2 expression in 49.5% of DLBCL and in 59.5% of Non-GCB subdivion which was significant statistical difference compared to 27.3% of GCB subdivion (P=0.000);36.5% of DLBCL showed activated NF-κB expression, GCB subdivion had 25.8%, and Non-GCB subdivion had 41.2%, which showed statistical difference(P<0.05);58.9% showed high expression of Ki-67 (126/214),GCB subdivion had 35 cases(53.0%),Non-GCB subdivion had 91 cases(61.5%),there was no significant statistical difference in two subdivions of DLBCL (P=0.246).⑵The expression of BCL2 protein was not correlated with the sex ,site, Ann Arbor stage, IPI, LDH and sites of extranodal involvement, with the exception of age, which was higher in group age≥50(P=0.002);The expression of NF-κB was not correlated with sex ,age and sites of extranodal involvement, the expression of NF-κB was higher in nodal group(P=0.002), stageⅢ-Ⅳgroup(P=0.005),intermediate high risk-high risk group(P=0.022),elevated LDH group(P=0.018);The expression of Ki-67 was not correlated with any of the clinical characteristics(P>0.05).⑶In 214 DLBCL,8 cases (3.7%)have t(14;18) BCL2 gene translocation,6 cases (9.1%)were GCB subdivion, the t(14;18) BCL2 gene translocation was higher in GCB subdivion(P=0.018);BCL2 gene amplification was found in 113 cases(52.8%),27 cases were GCB subdivion(27/66,40.9%),86 cases were Non-GCB subdivion(86/148,58.1%), BCL2 gene amplification was higher in Non-GCB subdivion(P=0.02)。⑷In Non-GCB subdivision, the expression of BCL2 was correlated with that of NF-κB expression(r=0.216,P=0.008),and BCL2 gene amplification(r=0.219,P=0.007),respectively, but there was no significant correlation with t(14;18) BCL2 gene translocation;in GCB subdivision, BCL2 expression showed no correlation with NF-κB expression,t(14;18) BCL2 gene translocation and BCL2 gene amplification。⑸the survival times of BCL2-positive patients shorter than that of BCL2-negative patients, the M±S.E. were 31.42±3.77 months and 40.15±4.21 months ,respectively; patients having BCL2 expression, compared with those without BCL2 expression, would face significant higher risk of death (HR=1.9).Conclusions: The expression of anti-apoptotic gene BCL2 differed significantly between GCB and Non-GCB subdivisions of DLBCL in Guangxi, China. Independent of immunosubdivision, BCL2-positive patients had more short survival times, would face significant higher risk of death, these results suggested that BCL2 could be a prognostic marker. BCL2 gene amplification and NF-κB activation, instead of t(14,18) BCL2 translocation, were closely related to the over-expression of BCL2 in Non-GCB ,while this correlation was absent in GCB. Our data supported that there was distinctive pathogenetic mechanism in two immunophenotypical subdivisions of DLBCL, compare to neoplastic cell proliferation, anti-apoptosis induced by BCL2 contribute more to aggressive biological features and resistant to conventional chemotherapy, which result to worse prognosis.