Suppression of Bcl-2 by Antisense Oligonucleotides and Compensation by Non-Targeted Genes Could Enhance Tumor Proliferation by Increased Chromosomal Instability and Formation of Fusion Proteins

Antisense oligonucleotides (oligos) have targeted regulatory proteins in both in vivo and in vitro prostate cancer models featuring both the LNCaP and PC-3 cell lines. In efforts to identify compensatory changes in the expression of non-targeted genes this study evaluated monoand bispecific oligos capable of targeting and equally suppressing the expression of bcl-2 (an apoptosis inhibitor). Effects upon non-targeted genes could potentially lead to development of more phenotypically aggressive and metastatic tumors, as suggested by previous studies which have shown that oligo treated LNCaP cells compensate for diminished bcl-2 by suppressing caspase-3 (an apoptosis promoter) while enhancing the expression of AKT-1 (another apoptosis inhibitor). In addition, we found enhanced expression of the androgen receptor (AR), its p300 and IL-6 co-activators, polymerase transcription mediator MED-12, and growth regulating signal transducer STAT-3. This suggests that therapeutic approaches to restore apoptosis through suppression of bcl-2 lead to altered protein expression of non-targeted genes not only involving apoptosis, but also androgen sensitivity and transcription. In addition, proteins associated with cell division as indicated by increased expression of the KI-67 proliferation antigen and mitosis regulating cyclin D1 are increased. The net result is an altered pattern of gene expression often associated with more aggressive and proliferative tumors. To further evaluate adaptive compensatory mechanisms related to tumor resistance, aggression and proliferation we now evaluate the level of gene expression associated with producing fusion proteins and transcription factors which lead to the increased chromosomal instability associated with aggressive tumors. We now evaluate TMPRSS22, ERG and FLI-1 for changes in their expression. Fusion proteins formed from TMPSS22 and ERG are found in 40-80% of human prostate tumors, and ERG over expression is thought to disrupt AR signaling contributing to the development of androgen independent tumors. FLI-1 is a transcription factor associated with ETS expression and with the gene fusions increasingly found to be associated with development and progression of prostate cancer.