Background
We explored whether the disialoganglioside GD2 (GD2) is expressed in small cell lung cancer (SCLC) and non-SCLC (NSCLC) and can be targeted by GD2-specific chimeric antigen receptor (CAR) T cells.
Conclusions
GD2 is a promising target for CAR-T cell therapy in lung cancer. Tazemetostat treatment could be used to upregulate GD2 expression in tumor cells, enhancing their susceptibility to CAR-T cell targeting.
Methods
GD2 expression was evaluated in tumor cell lines and tumor biopsies by flow cytometry and immunohistochemistry. We used a GD2.CAR that coexpress the IL-15 to promote T-cell proliferation and persistence, and the inducible caspase 9 gene safety switch to ablate GD2.CAR-T cells in case of unforeseen toxicity. The antitumor activity of GD2.CAR-T cells was evaluated using in vitro cocultures and in xenograft models of orthotopic and metastatic tumors. The modulation of the GD2 expression in tumor cell lines in response to an epigenetic drug was also evaluated.
Results
GD2 was expressed on the cell surface of four of fifteen SCLC and NSCLC cell lines (26.7%) tested by flow cytometry, and in 39% of SCLC, 72% of lung adenocarcinoma and 56% of squamous cell carcinoma analyzed by immunohistochemistry. GD2 expression by flow cytometry was also found on the cell surface of tumor cells freshly isolated from tumor biopsies. GD2.CAR-T cells exhibited antigen-dependent cytotoxicity in vitro and in vivo in xenograft models of GD2-expressing lung tumors. Finally, to explore the applicability of this approach to antigen low expressing tumors, we showed that pretreatment of GD2low/neg lung cancer cell lines with the Enhancer of zeste homolog 2 inhibitor tazemetostat upregulated GD2 expression at sufficient levels to trigger GD2.CAR-T cell cytotoxic activity. Conclusions: GD2 is a promising target for CAR-T cell therapy in lung cancer. Tazemetostat treatment could be used to upregulate GD2 expression in tumor cells, enhancing their susceptibility to CAR-T cell targeting.