Co-expression of B7-1 with Interleukin-12 Enhances Vaccine-induced Antitumour Immunity in Experimental Myeloma

There has been little improvement in the treatment of multiple myeloma over the past 25 years. Disease inevitably reoccurs in patients who receive chemotherapy of melphalan and prednisone or combinations of alkylating agents. Autologous hematopoietic stem cell transplantation can increase remission rates and prolong diseasefree and overall survival. However, all transplanted myeloma patients ultimately relapse. The ineffectiveness of conventional induction and maintenance therapies in multiple myeloma has motivated the search for alternative treatment strategies. Immunotherapy involving cancer vaccines is one such alternative where the intent is to induce a host antitumour immune response. In this study, we employed a syngeneic murine model of multiple myeloma developed in our laboratory to examine the consequence of combined expression of interleukin-12 (IL-12) and the B7-1 costimulatory molecule on myeloma immuno genicity. We show that the IL-12/B7-1 immunogene combination was efficacious in evoking systemic protective immunity against unmodified parental myeloma cells. These findings suggest that autologous myeloma cells engineered to co-express IL-12 and B7-1 may hold promise as cancer vaccines for consolidation therapy in multiple myeloma.