Optimization Studies on Prokaryotic Cell Expression of the Human Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL).

The aim of the study was to optimize the in vitro induction and expression of the human tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and also study the processes of its denaturation, renaturation, and purification. The pGEX-6P-1/TRAIL114-281 plasmid was induced by isopropyl-ß-D-1-thiogalactopyranoside (IPTG) in Escherichia coli BL21 (DE3), and the expressed target protein was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The protein expressed in the form of inclusion body was first denaturalized and then renaturalized by dilution and dialysis technique. GST-rTRAIL114-281 fusion protein was purified by Glutathione-Superflow Resin affinity chromatography and confirmed by Western blot. The molecular weight of GST-rTRAIL expressed in E. coli BL21 (DE3) was approximately 40 kDa. GST-rTRAIL was mainly expressed in the form of inclusion bodies. An optimum expression was induced by IPTG at a concentration of 0.2 mM for 8 h at 37 °C. Glutathione-Superflow Resin affinity chromatography yielded the purified GST-rTRAIL protein which was confirmed by Western blot using anti-GST mouse monoclonal antibody. The optimum prokaryotic cell expression of the human GST-rTRAIL was obtained by 0.2 mM IPTG induction for 8 h at 37 °C. The denatured inclusion body protein can be refolded by dilution and dialysis and purified by Glutathione-Superflow Resin affinity chromatography.

Silencing the expression of Cbl-b enhances the immune activation of T lymphocytes against RM-1 prostate cancer cells in vitro.

BACKGROUND: The ubiquitin ligase Cbl-b potently modulates T lymphocyte immune responses and is critical in modulating tumor-induced immunosuppression. The influence of Cbl-b in modulating T lymphocyte activity against prostate cancer remains ill defined. We have determined the effects of silencing Cbl-b expression in T lymphocytes and their subsequent cytotoxic activity against prostate cancer cells. METHODS: T lymphocytes were isolated from the spleens of C57BL/6 mice. Lipofectamine-directed transfection of T lymphocytes with specific small interfering RNA (siRNA) silenced Cbl-b expression, which was confirmed by Western immunoblotting. The siRNA species were chosen that promoted the greatest transfection efficiency and dampened Cbl-b expression in T lymphocytes. The expression of CD69, CD25, and CD71 by the transfected T lymphocytes was determined by flow cytometry. T lymphocyte proliferation was assessed by CCK-8 assay. Enzyme-linked immunosorbent assay (ELISA) was used to measure the secretion of interleukin (IL)-2, interferon (IFN)-γ, and tumor necrosis factor (TNF)-ß. The objective was to compare the cytotoxic activity of transfected T lymphocytes and nontransfected (i.e., negative control) T lymphocytes against the murine prostate cancer cell line target RM-1 in vitro. RESULTS: We selected a specific siRNA that decreased T lymphocyte Cbl-b expression to 15%. The siRNA-transfected T lymphocytes showed higher proliferation; higher CD69, CD25, and CD71 expression (p < 0.001); and higher IL-2, IFN-γ, and TNF-ß secretion (p < 0.05), compared to the nontransfected cells. Transfected T lymphocytes were also more potent at killing RM-1 prostate cancer cells, compared to the negative control in vitro. CONCLUSION: Silencing Cbl-b significantly enhanced T lymphocyte function and T lymphocyte cytotoxicity activity against a model prostate cancer cell line in vitro. This study suggests a potentially novel immunotherapeutic strategy against prostate cancer.