HER2-Specific Synthetic Antigen Receptor (SAR) T Cell Therapy Synergizes with Radiotherapy to Provide Improved Anti-Tumor Efficacy in Non-Small Cell Lung Cancer (NSCLC)

Induction radiotherapy (7 d before T cell infusion) synergistically improved tumor control and survival. Radiotherapy transiently upregulated HER2 expression (4 to 24 h), though administering HER2-SAR T cells within this window did not enhance antitumor efficacy. Radiation did not enhance T cell-mediated cytotoxicity in vitro.

However, in tumors, radiotherapy increased intratumoral proliferation and accumulation of HER2-SAR T cells and enhanced the extrinsic apoptotic pathway, including induction of Fas transcript and protein levels and cleaved caspase-3 (CC3). RNA-seq of irradiated tumors revealed lasting transcriptional reprogramming with increased immune activation and decreased proliferation and oncogenic signaling. Induction radiotherapy enhances HER2-SAR T cell infiltration and provides synergistic tumor suppression, likely through additional activation of immune-mediated apoptosis.

These findings support further assessment of HER2-SAR T cell therapy in HER2-expressing NSCLC.