INTRODUCTION: The selection of an effective adjuvant is an important step in the development of a cancer vaccine. We compared the adjuvant properties of monophosphoryl lipid A (MPLA), Flt3 ligand, and BCG when given in conjunction with a tumor vaccine. The impact of vaccine/adjuvant on tumor growth in a subcutaneous location was determined.
METHODS: This study involved C26 murine colon adenocarcionma cell line, which is syngeneic with C3H/He mice. A vaccine consisting of 105 UV-irradiated whole tumor cells plus an adjuvant was given to all test group mice 3 times prior to inoculation of the mice with live tumor cells. There were a total of 4 groups (n=5 mice/group): 1) control (tumor cell injection only), 2) vaccine plus MPLA, 3) vaccine plus Flt3 ligand, and 4) vaccine plus BCG. Two weeks later, the animals were sacrificed and their tumor size measured.
RESULTS: The MPLA/vaccine group mice had significantly smaller tumors (0.595± 0.153cm3) than those of the control group (0.973± 0.153cm3, p<0.05). Surprisingly, neither Flt3/vaccine (0.833± 0.186cm3) or BCG plus vaccine (0.905± 0.420cm3) had an impact on tumor growth when compared to the control group results in this model.
CONCLUSION: MPLA appears to be an effective adjuvant in this model. Tumor growth in a subcutaneous location was significantly diminished in animals that received this combination prior to live tumor cell inoculation. For unclear reasons, the other adjuvants tested were not effective.