Dissecting the Radioresponse Heterogeneity of Lung Adenocarcinoma Cells From the Perspective of Transcriptional and Regulatory Landscape.

Radioresistance severely compromises radiotherapy efficacy for lung adenocarcinoma (LUAD), yet the intrinsic heterogeneity of cellular radioresponses among isogenic tumor cells remains poorly characterized. Here, we integrated single-cell RNA sequencing (scRNA-seq) and single-cell assay for transposase-accessible chromatin with high-throughput sequencing (scATAC-seq) to dissect the transcriptional and regulatory landscape underlying heterogeneous radioresponses in single-cell-derived LUAD cells following 6 Gy γ-ray irradiation. We found that isogenic LUAD cells harbored intrinsic molecular determinants for divergent radiosensitivity and displayed heterogeneous radioresponsiveness upon irradiation. A radiation-associated transcriptional cell state, coupled with DNA damage repair, apoptosis, and cell cycle regulation, emerged at 6 h post-irradiation. Inhibition of lysine demethylase 4B (KDM4B) enhanced LUAD radiosensitivity by intensifying DNA damage, whereas reduced expression of cyclin B1 (CCNB1) and DNA topoisomerase IIα (TOP2A) potentially contributed to radiation-triggered G2/M arrest. Notably, the radiation-associated regulatory cell state emerged earlier than radiation-induced transcriptional cell state. RNA polymerase II subunit A (POLR2A) functioned as a core regulator in high-responsive LUAD cells. Based on these findings, we proposed a hypothesis for the radiosensitization of LUAD cells. Collectively, this study provides multilayer mechanistic insights into LUAD radioresponse heterogeneity and yields actionable molecular candidates for developing improved radiosensitization strategies to advance precise radiotherapy for LUAD.