EGFR‐targeted CAR‐T cells are potent and specific in suppressing triple‐negative breast cancer both in vitro and in vivo

OBJECTIVES: Triple‐negative breast cancer (TNBC) is well known for its strong invasiveness, rapid recurrence and poor prognosis. Immunotherapy, including chimeric antigen receptor‐modified T (CAR‐T) cells, has emerged as a promising tool to treat TNBC. The identification of a specific target tumor antigen and the design of an effective CAR are among the many challenges of CAR‐T therapy. METHODS: We reported that epidermal growth factor receptor (EGFR) is highly expressed in TNBC and consequently designed an optimal third generation of CAR targeting EGFR. The efficacy of primary T lymphocytes infected with EGFR CAR lentivirus (EGFR CAR‐T) against TNBC was evaluated both in vitro and in vivo. The signalling pathways activated in tumor and EGFR CAR‐T cells were revealed by RNA sequencing analysis. RESULTS: Third‐generation EGFR CAR‐T cells exerted potent and specific suppression of TNBC cell growth in vitro, whereas limited cytotoxicity was observed towards normal breast epithelial cells or oestrogen receptor‐positive breast cancer cells. This capability was further demonstrated in vivo in a xenograft mouse model, with minimal off‐tumor cytotoxicity. Mechanistically, in vitro stimulation with TNBC cells induced the expansion of naïve‐associated EGFR CAR‐T cells and enhanced their persistence. Furthermore, EGFR CAR‐T cells activated the interferon γ, granzyme–perforin–PARP and Fas–FADD–caspase signalling pathways in TNBC cells. CONCLUSION: We demonstrate that EGFR is a relevant immunotherapeutic target in TNBC, and EGFR CAR‐T exhibits potent and specific antitumor activity against TNBC, suggesting the potential of this third‐generation EGFR CAR‐T as an immunotherapy tool to treat TNBC in the clinic.