Induction of diferential cytotoxicity and ROS‑driven severe genomic DNA damage and intrinsic mitochondrial apoptosis by erbium oxide nanoparticles in p53‑compromised human NSCLC cells

Abstract

Non-small cell lung cancer (NSCLC) remains a leading cause of cancer-related mortality worldwide, with current therapeutic strategies limited by systemic toxicity, drug resistance, and poor tumor selectivity. These limitations highlight the urgent need for safer, targeted therapeutic strategies. In this context, erbium oxide nanoparticles (Er2O3NPs) have attracted attention in biomedical research due to their unique physicochemical characteristics, yet their potential as anticancer agents against NSCLC remains fully unexplored. This study was consequently conducted to assess the anticancer efficacy and underlying mechanisms of Er2O3NPs in human A549 NSCLC cells, alongside with evaluating their safety in normal WI-38 lung fibroblasts. Cytotoxicity was determined using the MTT assay, and genomic DNA integrity was assessed via the alkaline Comet assay. Oxidative stress and mitochondrial function were evaluated through 2′,7′-dichlorodihydrofluorescein diacetate (2,7-DCFH-DA) and Rhodamine-123 staining, respectively. Apoptotic induction was analyzed using DAPI nuclear staining and chromatin diffusion assays, while qRT-PCR quantified the expression of apoptosis- and mitochondria-related genes. Er2O3NPs exhibited concentration-dependent cytotoxicity in A549 cells (IC50 = 93.46 µg/ml) and lower toxicity in WI-38 fibroblasts (IC50 = 147.5 µg/ml), yielding a selectivity index of 1.58. Mechanistically, treating A549 cells at the IC50 concentration for 72 h induced severe genomic DNA damage, excessive ROS generation, and pronounced mitochondrial membrane depolarization. DAPI staining revealed characteristic apoptotic nuclear changes, including chromatin condensation and fragmentation, while the chromatin diffusion assay demonstrated extensive DNA dispersion indicative of advanced apoptotic DNA degradation. Moreover, qRT-PCR analysis showed significant downregulation of p53, Bcl-2, and ND3 gene expression. Given the inherent mutant p53 status of A549 cells, this transcriptional downregulation indicates that Er2O3NPs bypass canonical wild-type p53 transcriptional activation, triggering instead an ROS-driven intrinsic mitochondrial apoptotic signaling pathway. In conclusion, Er2O3NPs induce preferential cytotoxicity in NSCLC cells through ROS-mediated severe genomic DNA damage and intrinsic mitochondrial dysfunction within a p53-compromised genetic background. These findings suggest that Er2O3NPs hold potential as a nanotherapeutic candidate for NSCLC. However, further in vivo studies, targeted delivery systems, and direct protein-level evaluations are warranted to fully clarify these mechanisms and advance their clinical applicability.