ABSTRACT
<p><b>OBJECTIVE</b>To investigate the reversing effect of Bcl-XL small interfering RNA (siRNA) on the acquired resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in human colon cancer.</p><p><b>METHODS</b>Human colon cancer cells DLD1-TRAIL/R, with acquired resistance to TRAIL, were firstly transfected with Bcl-XL siRNA for 24 h followed by the treatment of TRAIL protein. The survival rate of DLD1-TRAIL/R cells was assessed by FACS analysis and cell number counting, respectively, and activation of its apoptotic signaling was evaluated by Western blot.</p><p><b>RESULTS</b>Bcl-XL siRNA effectively downregulated the expression of Bcl-XL protein and reversed the acquired resistance to TRAIL in DLD1-TRAIL/R cells. After combination treatment of Bcl-XL siRNA and TRAIL protein, the apoptotic rate of DLD1-TRAIL/R cells was more than 50% and survival rate was less than 40%, whereas there was no effect on the survival of DLD1-TRAIL/R cells after treatment with control treatment or TRAIL protein treatment alone (P < 0.05). Western blot analysis demonstrated that caspase-8, caspase-9, Bid, caspase-3, and poly (ADP-ribose) polymerase (PARP) were obviously activated after combination treatment with Bcl-XL siRNA and TRAIL protein, and the release of cytochrome C was also significantly increased.</p><p><b>CONCLUSION</b>Bcl-XL siRNA can effectively reverse the acquired resistance to TRAIL in human colon cancer cells, suggesting that it might be a new strategy for overcoming the resistance in cancer therapy.</p>
Subject(s)
Humans , Apoptosis , BH3 Interacting Domain Death Agonist Protein , Metabolism , Caspase 3 , Metabolism , Caspase 8 , Metabolism , Caspase 9 , Metabolism , Caspases , Metabolism , Cell Line, Tumor , Cell Survival , Colonic Neoplasms , Metabolism , Pathology , Cytochromes c , Metabolism , Drug Resistance, Neoplasm , Poly(ADP-ribose) Polymerases , Metabolism , RNA, Small Interfering , TNF-Related Apoptosis-Inducing Ligand , Genetics , Metabolism , Transfection , bcl-X Protein , Genetics , MetabolismABSTRACT
Objective: To observe the expression of Bcl-2, Bcl-xL and Bax in colorectal cancer tissues and their corresponding adjacent tissues (>5 cm from the tumor tissue), and to study their roles in the development and progression of colorectal cancer. Methods: The mRNA levels of Bcl-2, Bcl-xL, Bax were detected by RT-PCR and their protein levels were detected by MaxVision one step method in 40 colorectal cancer tissues and their corresponding adjacent tissues. Results: The mRNA and protein levels of Bcl-2 were very low in both cancer tissues and adjacent tissues(P>0.05). Both cancer tissues and adjacent tissues had higher Bcl-xL mRNA and protein levels, with those of the cancer tissues obviously higher than those of the adjacent tissues (P<0.05). The levels of Bax MRNA and protein were higher than those of Bcl-2 and Bcl-xL in both tissues, but with no significant difference between the 2 tissues. The ratio of Bcl-2/Bax and Bcl-xL/Bax in 2 tissues had no significant difference, either. The expression of Bcl-2 protein was negatively correlated with Dukes and TNM stages of the colorectal cancer (P<0.05), and was not correlated with other factors such as sex, age, tumor size, tumor location and morphological types. Levels of mRNA and protein of Bcl-xL and Bax were not correlated with pathological factors. Conclusion: Bcl-xL expression is obviously higher than that of Bcl-2 in colorectal tissues and also higher than that of Bcl-xL in adjacent tissues, suggesting that Bcl-xL may enhance the development and progression of colorectal cancer. Bcl-2 may be a prognostic indicator for colorectal cancer because it is negatively correlated with tumor stages.