Induction of CD4+ T and NK cell-mediated antitumoral response by immunization with breast cancer cells transfected with a dominant negative vector of Stat3

MERCEDES TKACH; LORENA M. CORIA; CINTHIA ROSEMBLIT; MARTÍN A. RIVAS; WENDY BEGUELIN; CECILIA PROIETTI; CELESTE M. DIAZ FLAQUÉ; EDUARDO H. CHARREAU; PATRICIA V. ELIZALDE; JULIANA CASSATARO; ROXANA SCHILLACI

Buenos Aires

Congreso; First French-Argentine Inmunology Congress; 2010

The evidence that disruption of Stat3 signaling in cancer cells can overcome tumor immune evasion, leads us to design an immunotherapy based on the administration of irradiated breast cancer cells that express a dominant negative (DN) form of Stat3. We have already shown that this immunization provides protection against the murine progestin-dependent C4HD tumor in a prophylactic protocol. Now, our focus is disclosing the lymphocyte subsets involved in the antitumoral response. To achieve this, immunized BALB/c mice were in vivo depleted of CD4+, CD8+, or NK cells with monoclonal antibodies before tumor challenge. Depletion of CD4+T or NK cells completely abrogated resistance to tumor challenge induced by immunization with DNStat3-transfected C4HD cells (**p<0,01 and *p<0,01 respectively). However, depletion of CD8+ T cells did not affect C4HD tumor rejection. We demonstrated that splenocytes from mice injected with DNStat3-C4HD cells were effective in lysing C4HD in vitro. To determine whether NK cells were responsible for that cytotoxic effect, we isolated them from spleens of immunized mice and performed a 51Cr release assay. NK cells from mice immunized with DNStat3-transfected C4HD cells showed an increased cytotoxicity against YAC-1 cell line, and C4HD cells compared to mice immunized with empty vector-transfected C4HD cells (27,5+2,5% vs 5,2+1,9% and 15,7+2,4 vs 5,3+2,7, respectively, 5:1 effector-to-target ratio, p<0,05). In additon, IFN-g production was enhanced in splenocytes from mice immunized with DNStat3-C4HD cells vs control group (249.2+5,1 vs 143.2+16,5 pg/ml p<0,05).As we have already demonstrated that immunization with DNStat3-transfected cells in nude mice, did not protect against C4HD tumor development, these results support the concept that breast cancer growth can be inhibited through induction of a CD4+ and NKcell-dependent protective immune response in vivo with tumor immunogens derived from DNStat3-transfected breast cancer cells.