CSPG4-Specific CAR.CIK Lymphocytes as a Novel Therapy for the Treatment of Multiple Soft-Tissue Sarcoma Histotypes.

Abstract

No effective therapy is available for unresectable soft-tissue sarcomas (STS). This unmet clinical need prompted us to test whether chondroitin sulfate proteoglycan 4 (CSPG4)-specific chimeric antigen receptor (CAR)-redirected cytokine-induced killer lymphocytes (CAR.CIK) are effective in eliminating tumor cells derived from multiple STS histotypes <i>in vitro</i> and in immunodeficient mice. The experimental platform included patient-derived CAR.CIK and cell lines established from multiple STS histotypes. CAR.CIK were transduced with a retroviral vector encoding second-generation CSPG4-specific CAR (CSPG4-CAR) with 4-1BB costimulation. The functional activity of CSPG4-CAR.CIK was explored <i>in vitro</i>, in two- and three-dimensional STS cultures, and in three <i>in vivo</i> STS xenograft models. CSPG4-CAR.CIK were efficiently generated from patients with STS. CSPG4 was highly expressed in multiple STS histotypes by <i>in silico</i> analysis and on all 16 STS cell lines tested by flow cytometry. CSPG4-CAR.CIK displayed superior <i>in vitro</i> cytolytic activity against multiple STS histotypes as compared with paired unmodified control CIK. CSPG4-CAR.CIK also showed strong antitumor activity against STS spheroids; this effect was associated with tumor recruitment, infiltration, and matrix penetration. CSPG4-CAR.CIK significantly delayed or reversed tumor growth <i>in vivo</i> in three STS xenograft models (leiomyosarcoma, undifferentiated pleomorphic sarcoma, and fibrosarcoma). Tumor growth inhibition persisted for up to 2 weeks following the last administration of CSPG4-CAR.CIK. This study has shown that CSPG4-CAR.CIK effectively targets multiple STS histotypes <i>in vitro</i> and in immunodeficient mice. These results provide a strong rationale to translate the novel strategy we have developed into a clinical setting.