Document Type : Original Article
IMMUNOLOGY DEPARTMENT, FACULTY OF MEDICINE, TEHRAN UNIVERSITY OF MEDICAL SCIENCES, TEHRAN, IRAN
Objective: In this study the effects of met-enkephalin on tumor infiltrating lymphocytes for cancer treatment in fibrosarcoma bearing mice was evaluated.
Materials and Methods: Initially, to obtain the most effective dose and treating time for the inductionof CD25, splenocytes were cultured with several doses of met-enkephalin. Flowcytometry was used to evaluate CD25 expression. The best dose and treating time were used to stimulate tumor infiltrating lymphocytes (TILs). To obtain pure CD4+ and CD8+ cells, TILs were taken from tumors by enzymatic tissue disaggregation and purified by magnet bead cell separation. After TILs stimulation they were re-injected into three groups of other fibrosarcoma bearing mice. The first group received only CD4+ TILs, the second group received only CD8+ TILs, and the third group received both CD4+ and CD8+ TILs. A fourth group that served as the control group received only phosphate buffered saline (PBS). The effect of this treatment on tumor volume, mice survival, effector cells, regulatory T cells and serum level Bcl-2were evaluated. To analyze data in both the experimental and control groups one way ANOVA was used followed by the Tukey test. P value <0.05 was considered significant.
Results: Treatment with met-enkephalin at a dose of 10-10 M for 6 hours was most effective in CD25 induction on the splenocytes of Balb/C mice. There were a significant decrease in tumors growth in both the CD8+ and CD4+ activated TILs injected groups (p<0.044 and p<0.017, respectively). The result of the CD4+ plus CD8+ activated TILs injected group was not significantly different from control group (p<0.661). There was an improvement in survival amongst the mice in all treated groups (p<0.001 for all three groups). FoxP3 levels in all groups were significantly low (p<0.001, p<0.002 and p<0.001 for the CD4+, CD8+ and CD4+ plus CD8+ activated TILs injected groups, respectively). CD25 and Bcl-2 expressions were higher in the treated groups, but only the CD4+ activated TILs injected group was significant (p<0.002 for CD25, p<0.001 for Bcl-2).
Conclusion: Met-Enk could be a potential new factor for activating lymphocytes in vitro.