Effect of modified tumor antigen on experimentally induced sarcomas

OBJECTIVE: To explore the possibility of controlling established tumors by active immunization through specific and nonspecific methods.

METHODS: By subcutaneous methylcholanthrene, a fibrosarcoma was produced in adult Swiss male mice. The fibrosarcoma was transplanted into the isogenic strain. The cleared tumor cells were injected subcutaneous into the hind leg of the 1st sarcoma group. The 2nd group received intraperitoneally sensitized spleen cells. One section of the irradiated 3rd tumor group received intraperitoneally sensitized spleen cells and subsequently a mild dose of modified tumor antigen. The 2nd section of the 3rd group was irradiated in between the administration of modified tumor antigen. In both the groups, liver of normal and transplanted tumor bearing mice was processed and intraperitoneally injected into the isogenic tumor bearing mice. Histopathology and tumor size by calipers was assessed.

RESULTS: The first group showed enhancement of tumor growth in all its 3 fractions injected at different intervals. In the 2nd group, the average survival period was prolonged. In the first section of the 3rd group a decrease in tumor size and protracted survival was noted. In the transplanted tumor bearing mice, complete suppression of tumor growth was observed. In the 2nd fraction of the 3rd group, long survival period with regression of tumor was observed. In the 4th group, attenuated tumor and one mouse was observed to become tumor free after 60 days.

CONCLUSION: Active immunosuppression by sensitized spleen cells and vaccines from transplanted sarcomas enabled regression of tumor size and longevity in tumor bearing mice. The modified tumor antigens, processed isogenic liver cells attenuated to zero level in tumor size in isogenic transplanted tumor bearing mice. The results show vaccines from allogenic and syngeneic sources bear the potential to regress tumor and enhance survival period.