Accumulation of mononuclear cells in tumors with growth slowing and elevation in host splenic histidine decarboxylase activity following repeated tumor injections with bradykinin.

Repeated intratumor injections of SV-40 virus-induced and transplaned syngenic fibrosarcomsa in hamsters with bradykinin (BK) has produced markded slowing of tumor growth in comparison with control saline injections. Growth slowing was greatest when the injections were daily, with a decrease in growth slowing as injections became less frequent. The growth slowing also was dose dependent (greater with 250 mug BK injections than with 50 mug BK injections). BK-injected tumors, on histological study, were found to have marked infiltration with mononuclear cells. This was not encountered in noninjected or saline-injected tumors. Significant mononuclear cell infiltration of noninjected tumors was found in two tumor animals which had had one tumor injectecd with BK. Splenic histidine decarboxylase (HDC) activity was higher in BK tumor-injected animals than in saline tumor-injected animals. Splenic HDC activity was higher when studed nearer the period of daily intratumor injections. The findings of this study suggest a potential role of inportance for inter-related vasoactive substances which act as mediators of inflammation in the study and therapy of neoplasia.