Active STAT5 in CD8 T cells imprints a T-Bet-dependent Tc-1 program with repressed IL-6/ TGFb1 signaling leading to enhanced anti-tumor responses. Mus musculus

CD8 T cells (TCs) expressing active STAT5 (STAT5CA) transcription factors were found to be superior to un-manipulated counterparts in their long-term persistence, capacity to infiltrate a tumor, thrive in its microenvironment and induce its regression. STAT5CA induced sustained expression of genes controlling tissue homing, cytolytic granule composition, Tc-1-associated effector molecules (GranzymeB+/IFNg+/TNFa+/CCL3+ but IL-2-) and potential for secondary responses. Sustained expression of both T-Bet and Eomes transcription factors was correlated with STAT5 binding to their corresponding genes by ChIPSeq analyses. Additionally, STAT5CA-expressing CD8 TCs demonstrated reduced IL-6R/TGFbRII expression and dampened IL-6 and TGFb1 signaling. Altogether, concerted STAT5/T-Bet/Eomes regulation controls homing, recall responses and resistance to Tc-17 polarization in CD8 TCs. Overall design: TCRP1A CD8 T lymphocytes were activated by their cognate P1A Ag. After 24h, an active form of Stat5 (STAT5CA) was introduced in activated cells. Culture was continued for another 48h to induce their differentiation in effector T cells. These activated T cells were injected in congeneic hosts and recovered 70 days later from hosts' spleen and lymph nodes: TCRP1A eTC-STAT5CA.