Interleukin-7 mediates selective expansion of tumor-redirected cytotoxic T lymphocytes without enhancement of regulatory T-cell inhibition

The Center for Cell and Gene Therapy has a research collaboration with Celgene and bluebird bio. All authors reviewed the manuscript and approved the final version of the manuscript. Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Adoptive transfer of virus-specific CTLs expressing a CAR represents a promising therapy for patients with cancer. However, the in vivo expansion of these cells remains suboptimal so that new strategies are required to selectively expand them without favoring the concomitant proliferation and function of Tregs that are often abundant in cancer patients. Our study provides preclinical data, indicating that the manipulation of the IL-7 cytokine-cytokine receptor axis in CAR-engrafted EBV-CTLs can be used to selectively expand the CTLs whilst avoiding the inhibitory effects of Tregs, which would otherwise be enhanced by use of the more broadly acting T-cell growth factor IL-2. Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. ABSTRACT Purpose: The antitumor activity of chimeric antigen receptor (CAR)-redirected cytotoxic T lymphocytes (CTLs) should be enhanced if it were possible to increase their proliferation and function after adoptive transfer without concomitantly increasing the proliferation and function of regulatory T cells (Tregs). Here we explored whether the lack of IL-7Rα in Tregs can be exploited by the targeted manipulation of the interleukin-7 (IL-7) cytokine-cytokine receptor axis in CAR-engrafted Epstein Barr Virus-specific CTLs (EBV-CTLs) to selectively augment their growth and anti-tumor activity even in the presence of Tregs. Experimental Design: We generated a bicistronic retroviral vector encoding a GD2-specific CAR and the IL-7Rα subunit, expressed the genes in EBV-CTLs and assessed their capacity to control tumor growth in the presence of Tregs in vitro and in vivo when exposed to either interleukin-2 (IL-2) or IL-7 in a neuroblastoma xenograft. Results: We found that IL-7, in sharp contrast to IL-2, supports the proliferation and antitumor activity of IL-7Rα.CAR-GD2 + EBV-CTLs both in vitro and in vivo even in the presence of fully functional Tregs. Conclusions: IL-7 selectively favors the survival, proliferation, and effector function of IL-7Rα-transgenic/CAR-redirected EBV-CTLs in the presence of Tregs both in vitro and in vivo. Thus, IL-7 can have a significant impact in sustaining expansion and persistence of adoptively CAR-redirected CTLs. Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited.