Microlipophagy-mediated lipid remodeling contributes to radioresistant phenotypes in small cell lung cancer.

BACKGROUND

Small-cell lung cancer (SCLC) is a highly aggressive malignancy characterized by frequent recurrence, in which radiotherapy remains a cornerstone treatment. However, the development of radioresistance severely limits its efficacy. Emerging evidence suggests that autophagy, particularly microlipophagy, contributes to cellular stress adaptation and therapeutic resistance, but its role in SCLC radioresistance remains unclear.

METHODS

To investigate the role of autophagy in cellular responses to irradiation, we established a radioresistant small-cell lung cancer (SCLC) cell model. We analyzed cell morphology, autophagosome formation, and post-irradiation survival in this model. We evaluated microlipophagy-associated changes using Oil Red O staining, lipid droplet-lysosome colocalization analysis, and triglyceride quantification. We used chloroquine (CQ) and bafilomycin A1 (BafA1) to inhibit autophagy and assess its effect on radiosensitivity. Transcriptome analysis was used to identify differentially expressed autophagy-related genes and analyze their functional enrichment.

RESULTS

Resistant cells exhibited morphological alterations, including the formation of small-scale megaphagosomes, increased autophagosome number, elevated LC3B expression, and higher survival post-irradiation. In contrast, parental cells showed minimal autophagosome formation and negligible co-localization of LC3B with lysosomes. Microlipophagic activity was enhanced in resistant cells, accompanied by accumulation of lipid droplets (LDs), elevated triglycerides, and increased colocalization of lysosomes and liposomes. Treatment with CQ inhibited autophagy, reduced LDs accumulation, and restored radiosensitivity. Transcriptomic analysis revealed multiple autophagy-related genes differentially expressed in resistant cells, enriched in cellular stress pathways.

CONCLUSIONS

Microlipophagy-mediated LDs accumulation promotes SCLC radiotherapy resistance via regulation of autophagy. Autophagy inhibition significantly enhances radiosensitivity, providing insights into underlying mechanisms and potential therapeutic strategies.