Abstract 2812: CSPG4-specific CAR.CIK lymphocyte-based immunotherapy to eliminate HLA class I-defective melanoma tumors

Abstract Purpose of this study is to explore the preclinical efficacy of Chondroitin Sulfate Proteoglycan 4 (CSPG4)-specific CAR-engineered Cytokine-Induced Killer lymphocytes (CIK) to eradicate melanoma cells with defective HLA class I (HLA-I). The latter abnormality plays a major role in clinical resistance to Checkpoint Inhibitors (CI). CSPG4 was selected as the target because of its high expression on melanoma and its restricted distribution in normal tissues. Our approach is based on CAR.CIK redirected against CSPG4. CIK, ex vivo expanded T-NK lymphocytes endowed with intrinsic HLA-independent antitumor activity, were used as effectors. Experimental procedure. CAR.CIK were generated by retroviral transduction of patient derived PBMC with a vector encoding a 2nd generation CSPG4-CAR with 4-1BB co-stimulation. Surface HLA-I expression was evaluated by flow cytometry on melanoma cell lines (Mel), derived by surgical biopsies. These cells also served as targets for CSPG4 CAR.CIK. The activity of CSPG4 CAR.CIK was analyzed in vitro and in immunodeficient mice grafted with a patient-derived HLA-defective melanoma. Mice were treated intravenously with 3x106 CAR.CIK (5 cells infusions in total). Results. CAR.CIK were efficiently generated from 4 melanoma patients. Mean expression of CSPG4-CAR was 48±8%, the rate of ex vivo expansion (84 fold) and phenotypic characteristics (CD3+CD8+=71±13%, CD3+ CD56+=22.5±13%, NKG2D+= 68±32.3%) were comparable with unmodified controls. Membrane HLA-I molecules were detected in 23/24 Mel samples, with a variable membrane density per cell (median 21232, range 787-49871). Sample Mel17 did not express HLA-I because of a start lost mutation (p.Met1Ile) in β2microglobulin. CSPG4 was intensely expressed by all Mel (78±5%), with no correlation to HLA-I levels. CSPG4 CAR.CIK efficiently killed 10 Mel samples in vitro, including Mel17 (HLA-I negative) and 2 Mel with the lowest HLA-I density (Mel71, Mel72). Mean Mel-specific killing by CSPG4 CAR.CIK was significantly higher compared with unmodified CIK especially at low effector/target (E/T) ratios (85% vs 40% at E/T=1:1; 46% vs 9% at E/T=1:8, p<0.0001). In vivo, CSPG4 CAR.CIK caused a significant inhibition of the HLA-negative Mel17 tumor growth (p<0.0001) as compared to controls. Antitumor activity was confirmed by the reduction of tumor weight and metabolic activity (by fluorescent glucose uptake) measured on the residual explanted tumors. Antitumor response persisted up to 2 weeks after end of the treatment. Conclusions. We reported the activity of CSPG4 CAR.CIK against melanoma, including those with low or defective HLA-I expression. CIK may provide a valid platform for CAR-based strategies against melanoma and solid tumors in general. Our data provide the rationale to implement clinical studies exploring the proposed strategy in melanoma patients not responding or relapsing after immunotherapy with CI. Citation Format: Giulia Cattaneo, Lidia Giraudo, Loretta Gammaitoni, Ilenia Iaia, Fabrizio Carnevale-Schianca, Alberto Pisacane, Enrico Berrino, Caterina Marchiò, Luca Paruzzo, Andrea Michela Biolato, Chiara Donini, Marco Basiricò, Elisa Landoni, Soldano Ferrone, Valeria Leuci, Massimo Aglietta, Gianpietro Dotti, Dario Sangiolo. CSPG4-specific CAR.CIK lymphocyte-based immunotherapy to eliminate HLA class I-defective melanoma tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2812.