Inhibition of DDR1 potentiates carbon ion radiotherapy by promoting ferroptosis and immunogenic death in head and neck squamous cell carcinoma.

Background: Carbon ion radiotherapy (CIR) has emerged as a promising therapeutic modality for photon-resistant malignancies due to its unique physical depth-dose distribution and enhanced radiobiological effectiveness. Nevertheless, treatment resistance persists in certain recurrent or refractory head and neck squamous cell carcinoma (HNSCC) cases, underscoring the need for novel combinatorial strategies. Here, we demonstrated the sensitizing effect of targeting discoidin domain receptor 1 (DDR1) in HNSCC for CIR.

Methods: MOC1 and and Cal27 cell lines along with tumor-bearing C57BL/6 mice were used for in vitro and in vivo studies. DDR1 was knocked down via lentivirus. Cell viability and proliferation were assessed by CCK-8 and colony formation assays. Immunogenicity and tumor-infiltrating lymphocytes were measured via flow cytometry and immunofluorescence. Tumor suppression mechanisms were investigated using RNA sequencing and bioinformatics. Ferroptosis markers (lipid peroxidation, iron, ROS) were detected using MDA, BODIPY 581/591 C11, FerroOrange, and DCFH-DA probes. Upstream ferroptosis mechanisms were analyzed by Western blot, co-immunoprecipitation, key molecule modulator administration, and SCD1 overexpression.

Results: We demonstrated that targeting DDR1 potentiated CIR by triggering ferroptosis-mediated immunogenic cell death, which in turn enhanced antitumor immunity. Mechanistically, DDR1 sustained tumor cell survival by forming 14-3-3-mediated assembly of a DDR1/14-3-3/Akt ternary complex, thereby activating the Akt/mTORC1/SREBP1/SCD1 axis to promote monounsaturated fatty acid (MUFA) biosynthesis and suppress ferroptosis. Silencing DDR1 disrupted this complex, alleviating MUFA-mediated ferroptosis inhibition and subsequently increasing tumor immunogenicity. This immunogenic shift facilitated CD8 + T cell infiltration and cytotoxicity, amplifying CIR-induced tumor suppression. Furthermore, pharmacological inhibition of DDR1 using the small-molecule inhibitor 7rh recapitulated these effects, demonstrating potent anti-proliferative and ferroptosis-inducing capabilities, enhancing CIR sensitivity to better control tumor progression.

Conclusions: Our findings positioned DDR1 targeting as a therapeutic strategy to potentiate CIR through immunogenic ferroptosis induction in HNSCC.