Augmented antitumor activity of Tumor Treating Fields (TTFields) with anti-VEGFR and docetaxel treatment in a lung cancer mouse model

Introduction: Angiogenesis drives disease progression and poor outcomes in non-small cell lung cancer (NSCLC). Ramucirumab, an antibody targeting the vascular endothelial growth factor receptor (VEGFR), is approved as a second-line therapy in combination with docetaxel for metastatic NSCLC. By normalizing tumor vasculature, angiogenesis inhibitors enhance drug delivery and facilitate immune cell infiltration Tumor Treating Fields (TTFields) are electric fields that disrupt cellular processes critical for cancer cell survival. TTFields therapy is approved for metastatic NSCLC concomitant with immune checkpoint inhibitors or docetaxel following progression on/after platinum-based therapy. Here, we investigated the therapeutic impact of TTFields applied together with docetaxel and anti-VEGFR treatment in an orthotopic mouse model of NSCLC. Methods: C57Bl/6 mice were orthotopically implanted with LL/2 lung carcinoma cells and allowed seven days for tumor establishment. Mice were then exposed continuously to TTFields (150 kHz) or sham (heat) treatment for eight days. The murine anti-VEGFR antibody DC101 (10 mg/kg) or vehicle was administered intraperitoneally on days 1, 4, and 7 of treatment. Docetaxel (3 mg/kg) or vehicle was administered intraperitoneally on days 2 and 6. The study included six treatment groups: control, docetaxel alone, docetaxel + DC101, TTFields alone, TTFields + docetaxel, and TTFields + docetaxel + DC101. At treatment completion, tumors were excised, weighed, and analyzed by immunohistochemistry using anti-CD31 for vessel staining, alongside additional functional markers. Results: Treatment with TTFields together with docetaxel and DC101 led to a marked reduction in tumor volume compared with all other treatment groups. Tumor weights and MRI analysis consistently showed the strongest inhibition of tumor growth under this regimen. Histological analysis revealed elevated cell death in tumors from the TTFields + docetaxel + DC101 group, as indicated by TUNEL staining. CD31 and alphaSMA co-staining indicated that TTFields, when applied together with anti-VEGFR therapy, promoted vascular normalization characterized by pericyte coverage and a more organized vasculature. This remodeling of the tumor microenvironment was accompanied by enhanced infiltration of CD8⁺ cytotoxic T cells, pointing to improved immune accessibility to the tumor core. Conclusions: Collectively, these findings suggest that TTFields amplify the therapeutic activity of antiangiogenic and chemotherapeutic agents by stabilizing tumor vasculature, facilitating immune cell penetration, and potentiating treatment-induced cell death.