Chemoimmunotherapy of murine mammary adenocarcinomas

Breast cancer is the most common form of noncutaneous malignancy in the United States. Since a plateau seems to have been reached in the efficacy of conventional therapy for this, as well as for other solid tumors, our laboratory has been studying the therapeutic potential of chemoimmunotherapy against the disease. Here we report on attempts to treat autochthonous mammary adenocarcinomas in C3H mice with tumor-infiltrating lymphocytes (TILs), interleukin-2 (IL-2) and cyclophosphamide (Cy) alone or in combination. Treatment with unfractionated TILs, IL-2 or Cy reduced tumor growth by 60-70%, when used alone. It was necessary to administer TILs and IL-2 by means of intratumor injection for them to be effective. IL-2 coupled with Cy given intraperitoneally (i.p.) reduced tumor growth by 85%. Adherent TILs (A-TILs) given together with Cy reduced tumor growth to the same extent. It can be concluded from this work that the growth of MMTV-induced mammary tumors in C3H mice can be significantly inhibited by chemoimmunotherapy. The two most effective protocols were combining Cy with either A-TILs or IL-2. No adverse side-effects were observed in animals that received IL-2 via intratumor injection.