Development of animmunotherapy against breast cancer based on cellular senescence induced by Stat3 blockade.

DE MARTINO M; MERCOGLIANO MF; TKACH M; VENTURUTTI, L; ELIZALDE PV; SCHILLACI R

Congreso; 6th International PacRim Breast and Prostate Cancer Meeting; 2015

Signal transducer and activator of transcription 3 (Stat3) is constitutively active in breast cancer (BC) and contributes to malignant transformation. Stat3 inhibition induces the expression of chemokines and proinflammatory cytokines. On the other hand, oncogene inactivation induces cellular senescence and a senescence-associated secretome (SAS) in diverse tumor types. In this work our objectives were to depict the senescence phenotype induced by Stat3 blockade and to apply the supernatants (SN) produced by Stat3-blocked cells as a source of immunogens to induce an antitumor immune response. With that purpose we studied diverse tumor types including ErbB2-positive and triple negative BC models, colon cancer and melanoma.Stat3 blockade was associated, in all cell types, with expression of senescence markers such as upregulation of acidic β-galactosidase staining, p16INK4a or p21cip1 and downregulation of Rb expression. Simultaneous transfection with siRNAs targeting Stat3 and p16ink4a or p21cipreverted the senescent phenotype. We performed a preclinical model, using the murine ErbB-2-positive C4HD cells, based on the administration of SN of Stat3-C4HD cells. We immunized animals with irradiated C4HD cells together with a depot containing SN of C4HD cells transfected in vitro either with siRNAs targeting Stat3 (senescent) and Stat3 and p16ink4a (non-senescent), or a control siRNA. After 3 immunizations, animals were challenged with C4HD tumor. We observed that immunization with SN of cells transfected with Stat3 siRNA or Stat3 and p16ink4a siRNA decreased tumor growth vs. control group. We detected a greater cytotoxic activity of NK cells and an increase in the number of memory CD4+ T cells in these two groups vs. control.These results suggest that Stat3 blockade drives a senescence program in diverse tumor types. The secretome of Stat3-blocked BC cells is an effective adjuvant independently of the SAS. Defining the composition of these supernatants opens up new avenues for immunotherapy in cancer patients.