Immunotherapy based on adoptive transfer of tumor antigen-specific CD8+ T cell (TC) is generally limited by poor in vivo expansion and tumor infiltration. In this study we report that activated STAT5 transcription factors (STAT5CA) confer high efficiency on CD8+ effector T cells (eTC) for host colonization after adoptive transfer. Engineered expression of STAT5CA in antigen-experienced TC with poor replicative potential was also sufficient to convert them into long-lived antigen-responsive eTC. In transplanted mastocytoma- or melanoma bearing hosts, STAT5CA greatly enhanced the ability of eTC to accumulate in tumors, become activated by tumor antigens and to express the cytolytic factor granzyme B. Taken together, these properties contributed to an increase in tumor regression by STAT5CA-transduced, as compared to untransduced TC including when the latter control cells were combined with infusion of IL-2/anti-IL-2 complexes. In tumors arising in the autochthonous TiRP transgenic model of melanoma associated with systemic chronic inflammation, endogenous CD8+ TC were non-functional. In this setting, adoptive transfer of STAT5CA-transduced TC produced superior anti-tumor effects compared to non-transduced TC. Our findings imply that STAT5CA expression can render TC resistant to the immunosuppressive environment of melanoma tumors, enhancing their ability to home to tumors and to maintain high granzyme B expression, as well as their capacity to stimulate granzyme B expression in endogenous TC.

PMID: 22065720 [PubMed - as supplied by publisher] Source: National Library of Medicine.