Priming of Colorectal Tumor-Associated Fibroblasts with Zoledronic Acid Conjugated to the Anti-Epidermal Growth Factor Receptor Antibody Cetuximab Elicits Anti-Tumor Vδ2 T Lymphocytes

SIMPLE SUMMARY: Different cells present in the tumor microenvironment can deeply influence both cancer spreading and the success of therapy in solid tumors, including colorectal carcinoma (CRC). In particular, tumor-associated fibroblasts (TAF) exert potent immunosuppressive effects leading to the impairment of anti-tumor surveillance and interfering with the function of therapeutic antibodies. Herein, we show that CRC-derived TAF can be turned by zoledronic acid (ZA), in soluble form or as antibody-drug conjugate (ADC), into efficient stimulators of anti-tumor lymphocytes. The ADC, made of the anti-EGFR cetuximab (Cet), used in CRC therapy, and ZA (Cet-ZA) can induce the proliferation of lymphocytes that become able to kill both tumor cells and TAF. The double result is a direct anti-cancer effect and the neutralization of the inhibitory activity exerted by its stroma. The major advantage of the Cet-ZA ADC formulation is the precise delivery of ZA to EGFR(+) cells, targeting TAF (potentially immunosuppressive), besides CRC cells. ABSTRACT: Tumor-associated fibroblasts (TAF) exert immunosuppressive effects in colorectal carcinoma (CRC), impairing the recognition of tumor cells by effector lymphocytes, including Vδ2 T cells. Herein, we show that CRC-derived TAF can be turned by zoledronic acid (ZA), in soluble form or as antibody-drug conjugate (ADC), into efficient stimulators of Vδ2 T cells. CRC-TAF, obtained from patients, express the epidermal growth factor receptor (EGFR) and the butyrophilin family members BTN3A1/BTN2A1. These butyrophilins mediate the presentation of the phosphoantigens, accumulated in the cells due to ZA effect, to Vδ2 T cells. CRC-TAF exposed to soluble ZA acquired the ability to trigger the proliferation of Vδ2 T cells, in part represented by effector memory cells lacking CD45RA and CD27. In turn, expanded Vδ2 T cells exerted relevant cytotoxic activity towards CRC cells and CRC-TAF when primed with soluble ZA. Of note, also the ADC made of the anti-EGFR cetuximab (Cet) and ZA (Cet-ZA), that we recently described, induced the proliferation of anti-tumor Vδ2 T lymphocytes and their activation against CRC-TAF. These findings indicate that ZA can educate TAF to stimulate effector memory Vδ2 T cells; the Cet-ZA ADC formulation can lead to the precise delivery of ZA to EGFR(+) cells, with a double targeting of TAF and tumor cells.