High bad and bcl-xL gene expression and combined bad, bcl-xL, bax and bcl-2 mRNA levels:: Molecular predictors for survival of stage 2 soft tissue sarcoma patients

The role of the bcl-2 gene family members in promoting or antagonizing apoptosis in malignant tumors, including soft tissue sarcomas (STS), is well known. However, the impact of mRNA expression of bcl-2 family genes on prognosis has not been thoroughly investigated in STS. Samples from 82 STS patients were analyzed for mRNA expression of bad, bax, bcl-x(L) and bcl-2 by a high-throughput quantitative RTPCR approach, using validated assays based on TaqMan(R) technology. The mRNA data, related to glyceraldehyde-3-phosphate dehydrogenase expression measured in the same sample, were analysed for their correlation to tumor stage and overall survival of patients. In a Kaplan-Meier analysis none of the mRNA levels investigated differed significantly with regard to their impact on survival (log-rank test). However, after including the tumor stage in the statistical analysis, a borderline significance was observed for bad mRNA expression (p=0.068) indicating a stage-specific impact of mRNA expression on prognosis. Considering STS patients of tumor stage 2, multivariate Cox analysis revealed that bad mRNA values greater than or equal to10 (p=0.0039; RR=9.08), bcl-x(L) greater than or equal to1.5 (p=0.067; RR = 4.59), bax greater than or equal to0.005 (p=0.1; RR=2.84) and bcl-2 <3 (p=0.42; RR=1.7) were associated with a poor prognosis. Combined high bad/bcl-x(L) mRNA expression levels revealed a 20 fold increase in the relative risk of tumor-related death (p=0.016) when comparing the poor and good prognosis groups. There was a 14.5 fold and 6.5-fold increase in the risk for the combinations of high bax/bcl-x(L) mRNA (p=0.018) and bax/bcl-2 mRNA expression (p=0.017), respectively. In conclusion, high bad mRNA levels and combined values of bad/bcl-x(L), bax/bcl-x(L) and bax/bcl-2 appear to be independent prognostic factors at least for stage 2 STS patients. In the combinations of mRNA levels there was more than an additive effect pointing to different pathways of prognostic relevance.