Lymphocyte migration to tumors after hyperthermia and immunotherapy

We have previously shown that the combination of immunotherapy with interleukin 2 (IL-2) and local hyperthermia (LHT) abrogates the growth of murine subcutaneous tumors significantly more than either modality alone. This study was undertaken to investigate whether the beneficial effect of combined modality therapy could be attributed to increased trafficking of effector cells to the tumor. After inducing MCA-105 sarcomas in the hindlimbs of C57BL/6 mice, animals were given no therapy, LHT, IL-2, or IL-2 + LHT followed by an iv injection of 51Cr-labeled syngeneic splenocytes or LAK cells. Select organs and the tumor-bearing extremity were counted in a gamma counter. IL-2 or LHT alone did not affect lymphocyte migration, while IL-2 + LHT significantly decreased trafficking (P less than 0.001) to the tumor. LAK cells showed increased migration to the tumor site compared to splenocytes in all treatment groups (P less than 0.02). IL-2 caused increased migration of LAK cells but not splenocytes to the lung; this was not affected by LHT. LAK cell trafficking to the spleen was decreased by IL-2 and IL-2 + LHT, while splenocyte migration was decreased in the LHT and combined treatment groups. LHT and IL-2 had no effect on trafficking of either effector cell type to liver or kidney. These results show that the beneficial effect of combined modality therapy may not be due to increased trafficking of lymphocytes to the tumor area. In addition, LAK cells traffic more to subcutaneous tumors than splenocytes, and this cannot be explained by the differential trafficking to other organs. The results of this study will be important in the planning of future experiments with combined adoptive immunotherapy and hyperthermia.