Targeting TAG-72 in cutaneous T cell lymphoma

Purpose: Current monoclonal antibody-based treatment approaches for cutaneous T cell lymphoma (CTCL) rely heavily on the ability to identify a tumor specific target that is essentially absent on normal cells. Herein, we propose tumor associated glycoprotein-72 (TAG-72) as one such target. TAG-72 is a mucin-associated, truncated O-glycan that has been identified as a chimeric antigen receptor (CAR)-T cell target in solid tumor indications. To date, TAG-72 targeting has not been considered in the setting of hematological malignancies. Experimental design: CD3⁺ cells from patients with CTCL were analyzed for TAG-72 expression by flow cytometry. Immunohistochemistry was used to assess TAG-72 expression in CTCL patient skin lesions and a TAG-72 ELISA was employed to assess soluble TAG-72 (CA 72-4) in patient plasma. TAG-72 CAR transduction was performed on healthy donor (HD) and CTCL T cells and characterized by flow cytometry. In vitro CAR-T cell function was assessed by flow cytometry and xCELLigence® using patient peripheral blood mononuclear cells and proof-of-concept ovarian cancer cell lines. In vivo CAR-T cell function was assessed in a proof-of-concept, TAG-72⁺ ovarian cancer xenograft mouse model. Results: TAG-72 expression was significantly higher on total CD3⁺ T cells and CD4⁺ subsets in CTCL donors across disease stages, compared to that of HDs. TAG-72 was also present in CTCL patient skin lesions, whereas CA 72-4 was detected at low levels in both CTCL patient and HD plasma with no differences between the two groups. In vitro cytotoxicity assays showed that anti-TAG-72 CAR-T cells significantly, and specifically reduced CD3⁺TAG-72⁺ expressing CTCL cells, compared to culture with unedited T cells (no CAR). CTCL CAR-T cells had comparable function to HD CAR-T cells in vitro and CAR-T cells derived from CTCL patients eradicated cancer cells in vivo. Conclusion: This study shows the first evidence of TAG-72 as a possible target for the treatment of CTCL.