Gemcitabine directly inhibits myeloid derived suppressor cells in BALB/c mice bearing 4T1 mammary carcinoma and augments expansion of T cells from tumor-bearing mice.

Myeloid derived suppressor cells (MDSCs) accumulate in 4T1 mammary carcinoma bearing mice and present a barrier to the success of adoptive immunotherapy (AIT) by suppressing T cell immunity. In this study, we investigated the inhibition of MDSCs by gemcitabine (GEM), a chemotherapy agent that may have favorable immunologic effects. BALB/c mice were inoculated with 4T1 mammary carcinoma cells and treated with GEM either once a week starting 5 days after tumor inoculation (EARLY GEM) or as a single dose at days 20-25 (LATE GEM).

Incubation of antigen-sensitized T lymphocytes activated with bryostatin 1 + ionomycin in IL-7 + IL-15 increases yield of cells capable of inducing regression of melanoma metastases compared to culture in IL-2.

Regression of established tumors can be induced by adoptive immunotherapy (AIT) with tumor draining lymph node (DLN) lymphocytes activated with bryostatin and ionomycin (B/I). We hypothesized that B/I-activated T cells cultured in IL-7 + IL-15 might proliferate and survive in culture better than cells cultured in IL-2, and that these cells would have equal or greater anti-tumor activity in vivo. Tumor antigen-sensitized DLN lymphocytes from either wild-type or T cell receptor transgenic mice were harvested, activated with B/I, and expanded in culture with either IL-2, IL-7 + IL-15 or a regimen of alternating cytokines.