Differential subcellular localization of LC3 in response to chemotherapeutics in lung adenocarcinoma cells

Introduction : Autophagy is a process used by eukaryotic cells to recycle intracellular components or digest damaged organelles and proteins. It involves the formation of autophagosomes, which fuse with lysosomes for degradation. MAP1LC3 (LC3) is the most relevant early autophagy marker in cytoplasm. However, a significant portion of LC3 is found in the nucleus, prompting questions about its additional functions. We aimed to evaluate the subcellular distribution of LC3 after exposure to chemotherapeutics used to treat non-small cell lung cancer. Methods : The A549 human lung adenocarcinoma cell line was exposed to Cisplatin, Carboplatin, Etoposide, Paclitaxel, and Gemcitabine. Afterward, immunofluorescence assessed the subcellular localization and distribution pattern of LC3 in individual cells. We also explored the modulation of key molecular players controlling the LC3 intracellular traffic through system biology and gene expression analysis. Ultimately, we assessed cellular senescence and its relationship with nuclear LC3. Results : Control cells exhibited similar levels of nuclear and cytoplasmic LC3, while cells that resisted drugs changed LC3 subcellular distribution with different patterns. Cisplatin-resistant cells strongly accumulated LC3 in the nucleus as heterochromatin-associated foci. Etoposide induced a similar phenotype beyond high levels of LC3 in the cytoplasm, while Gemcitabine and Paclitaxel exhibited cytoplasmic diffuse LC3 with no nuclear staining. Network analysis showed that Cisplatin may regulate SIRT1, a key factor controlling LC3 nucleocytoplasmic shuttling, which was confirmed by gene expression analysis. Finally, we observed an increased area for nuclei with more LC3 foci in Cisplatin-resistant cells, with a subsequent increase in cells with a senescent phenotype in this context. Conclusions: Lung cancer cells that survived Cisplatin showed increased nuclear LC3 foci. Understanding LC3 subcellular distribution patterns may reveal new mechanisms linked to sensitivity and resistance to cancer therapy.