Senescence and immunotherapy in breast cancer mediated by STAT3 blockade

DE MARTINO, MARA; MERCOGLIANO, MARÍA FLORENCIA; TKACH, MERCEDES; VENTURUTTI, LEANDRO; PROIETTI, CECILIA JAZMÍN; ELIZALDE, PATRICIA V.; SCHILLACI, ROXANA

Mar del Plata

Congreso; LX Reunión Científica Anual de la Sociedad Argentina de Investigación Clínica (SAIC); 2016

Sociedad Argentina de Investigación Clínica (SAIC)

Stat3 is constitutively active in 60% of breast cancer (BC) where it promotes tumor progression and immune evasion. We described in murine BC models that Stat3 inhibition leads to a senescence program and that immunization of mice with Stat3-blocked BC cells induces an antitumoral immune response that involves CD4+ Th cells and NK cells. Here, we studied the mechanism of senescence induced by Stat3 inactivation and the use of the supernatant (SN) from Stat3-blocked cells to formulate an effective immunotherapy (IT). Knockdown of Stat3 with siRNA induced senescence in triple negative (4T1, MDA-MB-231 and MDA-MB-468 cells) and ErbB2 positive (C4HD, JIMT-1 and KPL-4 cells) BC models, determined by SA-β-gal staining. Also, we observed an increase in trimethylation of histone H3 at lysine 9 and in cell cycle inhibitors expression (p16INK4a (p16) or p21CIP1). Simultaneous transfection with siRNAs targeting Stat3 and p16 or p21CIP1 reverted the senescent phenotype. Interestingly, Stat3 inhibition in vivo induced senescence and an increased p16 expression in 4T1 tumor. Then, we embedded the SN of C4HD or 4T1 cells transfected with Control siRNA (SN-Control), Stat3 siRNA (SN-Stat3) or the combination of Stat3 and p16 siRNAs (SN-Stat3+p16) in a slow delivery depot as an adjuvant of a cellular IT. Prophylactic IT before C4HD tumor challenge with SN-Stat3 and SN-Stat3+p16 decreased tumor growth (72%, p