Modification of cytokine-induced killer cells with folate receptor alpha (FRα)-specific chimeric antigen receptors enhances their antitumor immunity toward FRα-positive ovarian cancers

Folate receptor alpha (FR alpha) is aberrantly expressed in ovarian cancers but largely absent in normal tissues, and therefore represents an attractive target for immunotherapy. In recent years, modification of T cells with chimeric antigen receptor (CAR) targeting FRa has been reported to improve antitumor immunity of T cells. However, there are limited data regarding CAR-modified cytokine-induced killer (CAR-CIK) cells. In the present study, we modified CIK cells with FR alpha-specific CARs and investigated their antitumor immunity against ovarian cancers. We found that both non-transduced and mock CAR-transduced CIK cells showed only low antitumor activity against either FR alpha-positive (FR alpha*) or FR alpha-negative (FR alpha-) targets. However, all three generations of CAR -modified CIK cells showed enhanced antitumor activity against FRa* targets, but not FRa- targets. First -generation zeta-CAR-CIK cells increased production of IFN gamma, enhanced short-term cytotoxicity against FRa* ovarian cancer cells, and showed modest and shortterm suppression of established tumors; while second -generation 28 zeta-and third -generation 28BK zeta CAR-CIK cells showed significant proliferation, enhanced secretion of IL-2, eliminated the FRa* ovarian cancer cells in long-term co-culture, and showed dramatic and long-term inhibition of tumor growth and prolonged survival of xenograft-bearing mice. It is noteworthy that the 28BB zeta-CAR was more potent in the modification of CIK cells than 28 zeta-CAR both in vitro and in vivo. Moreover, CAR-OK cells showed more efficient anticancer activity compared with CAR-T cells in vitro, but less efficient than CAR-T cells in vivo. According to these results, we conclude that modification of CIK cells with FRa-specific CARs enhances their antitumor immunity to FRa* ovarian cancers. The third -generation 28BB-zeta CAR containing 4-1BB co-stimulation was more efficient in modification of CIK cells than either first -generation zeta -CAR or second -generation CD28 zeta CAR. (C) 2017 Elsevier Ltd. All rights reserved.