Chattopadhyay, A.; O'Connor, E. C.; Tingler, A. M.; Helke, K. L.; Engevik, M. A.; Ferreira, L. M. R.

Colorectal cancer (CRC) is the leading cause of cancer mortality in young adults, with chemoresistance and metastatic progression severely limiting treatment options. MUC4, a membrane-bound mucin normally confined to the apical surface of epithelial cells, becomes aberrantly overexpressed across the tumor cell membrane in CRC and other cancer types, promoting cancer survival, immune evasion, and metastasis. Therefore, MUC4 is a promising candidate for the development of targeted therapies. We detected MUC4 cell surface expression in a panel of human CRC cell lines. We engineered MUC4-specific chimeric antigen receptor (CAR) T cells and evaluated their activity against methotrexate-resistant MUC4-expressing human CRC cell lines HT29-MTX and T84. MUC4 CAR-T cells efficiently eliminated HT29-MTX and T84 cells in vitro and delayed HT29-MTX subcutaneous tumor growth in vivo. Importantly, MUC4 CAR-T cell treatment significantly reduced tumor burden and improved survival in a highly aggressive and lethal CRC model, intraperitoneal HT29-MTX CRC metastatic dissemination in NSG mice. Mouse necropsies revealed no off-target in vivo toxicities associated with MUC4 CAR-T cell therapy. Altogether, our findings establish MUC4 as an important and clinically relevant CAR-T cell target and demonstrate therapeutic efficacy of MUC4 CAR-T cell therapy for invasive CRC, a setting where chemotherapy typically fails. MUC4-targeted CAR-T cell therapy has the potential to fill a critical treatment gap for patients with chemoresistant and invasive CRC and may extend to other MUC4-expressing solid tumors.