RESUMO
<p><b>OBJECTIVE</b>To explore the effect of ricin temperature response gel on breast cancer and its regulatory effect on immune function in rats.</p><p><b>METHODS</b>Ricin was purified by chromatography and identified by immunoblotting. The rat subcutaneously transplanted breast cancer model was established. Forty model rats with a tumor diameter of about 3.0 cm were subjected to the study. They were randomized into four groups equally: the model group and three treated groups (blank gel, ricin, ricin-gel) were administered with blank gel, ricin, and ricin temperature response gel via percutaneous intratumor injection, respectively. The tumor was isolated 10 days later for the estimation of tumor inhibition rate (TIR) by weighing, pathologic examination, and detection of tumor apoptosis-associated genes bcl-2 and bax with semiquantitative RT-PCR. Also, peripheral blood was obtained to test T-lymphocyte subsets, the killing function of lymphocytes, and the contents of tumor necrosis factor-α (TNF-α) and interleukin-2 (IL-2). The outcomes were compared between groups.</p><p><b>RESULTS</b>The TIR in the ricin-gel group was 61.8%, with the pathologic examination showing extensive tumor tissue necrosis. Compared with the model group, after ricin temperature response gel treatment, bcl-2 expression was down-regulated, bax expression was up-regulated, CD4+ lymphocytes and CD4+/CD8+ ratio in peripheral blood were increased, the killing function of lymphocytes was enhanced, and the contents of TNF-α and IL-2 were elevated (P < 0.05 or P < 0.01).</p><p><b>CONCLUSION</b>Intratumor injection of ricin temperature-responsive gel showed significant antitumor effect on breast cancer and could enhance the immune function in the tumor-bearing rat.</p>