Immunization with breast cancer cells treated with antisense oligodeoxynucleotides (AS[S]ODN) to type I insulin-like growth factor receptor (IGF-IR) induced an antitumoral effect that is mediated by a CD8+-response involving Fas-FasL cytotoxic pathway

MARIANA SALATINO; ROXANA SCHILACCI; GUILLERMO GIAMBARTOLOMEI; CECILIA PROIETTI; JULIANA CASSATARO; ROMINA CARNEVALE; EDUARDO CHARREAU; PATRICIA ELIZALDE

Anaheim, CA, USA

Congreso; 96th Annual Meeting of the American Association for Cancer Research; 2005

American Association for Cancer Research

GF-IR plays a key role in cancer development and progression. We have already demonstrated that either direct intratumor or systemic administration of AS[S]ODN to IGF-IR mRNA resulted in significant inhibition of C4HD tumor growth in BALB-c mice (Oncogene 2004, 23: 5161). C4HD tumor belongs to a progestin-dependent mammary tumor model, requires medroxiprogesterone acetate (MPA) administration to proliferate and is non immunogenic. Previous reports suggested that the antitumor effect resulting from blockage of IGF-IR expression was also achieved through activation of a host’s immune response. The aim of this work was therefore to explore whether in vivo administration of C4HD tumor cells treated with IGF-IR AS[S]ODN and irradiated, could provide protection against C4HD wild-type tumor challenge. C4HD cells were treated in vitro with 2ìM IGF-IR AS[S]ODN + 10 nM MPA and then inactivated by irradiation. Mice were injected subcutaneously with 2x106 AS[S]ODNs-treated C4HD cells at 6, 4 and 2 weeks prior to challenge with C4HD tumor. Control groups included mice injected with PBS, with 2x106 C4HD cells treated either with MPA 10 nM or with 2ìM IGF-IR sense oligodeoxynucleotide (S[S]ODN) + MPA, and thereafter irradiated. Simultaneously to tumor challenge, mice were inoculated with the MPA depot. Our results showed that mice immunized with IGF-IR AS[S]ODN-treated C4HD cells, experienced significant inhibition of tumor growth with respect to control groups. The protective effect was C4HD-specific, since no protection was observed when immunized mice were challenged with the syngeneic mammary tumor lines 60HI or LM3. Immunization of nude mice did not prevent C4HD tumor formation, suggesting that T lymphocytes were involved in the antitumor effect. In addition, tumor-specific antibodies were not found in serum collected from BALB-c mice immunized with AS[S]ODN-treated cells, indicating absence of humoral response. Delayed-type hypersensitivity, citotoxicity and splenocytes proliferation assays demonstrated that a cellular CD8+-dependent immune response was responsible for the antitumor effect induced by immunization with AS[S]ODN-treated cells. Immunization also induced splenocytes to produce antigen-dependent IFN-ã and to kill tumor cells by a mechanism involving activation of Fas death pathway. Induction of immunogenic phenotype in C4HD cells after treatment with AS[S]ODN, occurred along with induction of the expression of peptide-chaperone protein Hsp70 and of the costimulatory molecule CD86. In conclusion, our results have for the first time demonstrated that breast cancer growth can be inhibited through induction of a protective immune response in vivo with tumor immunogens derived from IGF-IR AS[S]ODN-treated breast tumor cells.