Abstract 4677: Combating radioresistance in lung cancer: S6K1 signaling as a therapeutic target through metabolic modulation

Abstract Background: Locally advanced non-small cell lung cancer (NSCLC) is treated with a combination of chemotherapy, immunotherapy, and radiation but is unfortunately still associated with poor cancer survival. Improving radiation efficacy is essential to enhance tumor control and reduce resistance, ultimately improving outcomes for patients. Metabolic reprogramming could play a key role in this by targeting cancer cell metabolism to increase sensitivity to radiation and reduce tumor growth. S6K1 has emerged as a metabolic regulator that promotes chemo and radio-resistance in several cancers. However, the associated mechanisms to this phenomenon are unclear. We sought to determine if pharmacological or metabolic inhibition of S6K1 modulates radioresistance in lung cancer. Methods/Results: The intrinsic radiosensitivity of cells lines originating from NSCLC was determined by clonogenic and proliferation assays. Four cancer cell lines of varying intrinsic radiation sensitivity were chosen as a model to investigate the role of S6K1. The A549 cells were the most resistant followed by H661, H226 and the most sensitive as H23. The phospho-activation of S6K1 and its downstream target S6 increased in more resistant cells, associating S6K1 activation with radioresistance. TCGA analysis showed that S6K1 is overexpressed in lung cancer patients compared to healthy controls (p<0.001). Inhibition of S6K1 by pharmacologic means using a highly specific inhibitor (PF-4708671), or by genetic deletion of S6K1 by Crispr-Cas9, in combination with radiation, significantly decreased the colony formation compared with controls. Using in vivo murine models, S6K1-/- tumors had notably decreased tumor progression than the S6K1+/+ tumors (p<0.001). To determine the role of metabolic reprogramming on S6K1 activation and its effects on radioresistance, in vitro models of caloric restriction were tested and demonstrated a decreased S6K1 activation, and radiosensitivity trough reduction of transcriptional activation of STAT3, a target involved in radio-resistance. In NSCLC murine models, caloric restriction significatively decreased the tumor burden in mice. Conclusion: Our findings demonstrate that targeting S6K1, through pharmacological inhibition or metabolic interventions like caloric restriction, significantly enhances the therapeutic efficacy of radiotherapy in NSCLC. Studies are underway to elucidate the detailed mechanisms linking S6K1 activity and caloric restriction to radiosensitivity, with the potential to inform novel therapeutic strategies for improving outcomes in lung cancer patients. Citation Format: Ali Jose Calderon-Aparicio, Nicole L. Simone. Combating radioresistance in lung cancer: S6K1 signaling as a therapeutic target through metabolic modulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4677.