Synergistic Anticancer Effects of Resveratrol and Carboplatin in Y79 Retinoblastoma Cells: Mechanistic Insights into Apoptosis, G2/M Arrest, and ROS-Dependent Mitochondrial Dysfunction

This study aimed to investigate the effects of resveratrol (RES) and carboplatin (CPT), alone and in combination, on cell viability, apoptosis, cell cycle progression, mitochondrial function, and oxidative stress in Y79 retinoblastoma (RB) cells. Particular emphasis was placed on evaluating the synergistic potential of the combination and elucidating the interconnected molecular mechanisms underlying its anticancer effects. Y79 cells were treated with RES, CPT, and their combinations. Cell viability and synergy were assessed using the MTT assay and combination index (CI) analysis. Apoptosis (annexin V/PI), cell cycle distribution (propidium iodide (PI) staining), intracellular ROS production (DCFH-DA), and mitochondrial membrane potential (JC-1) were evaluated by flow cytometry. ROS dependency was further examined using N-acetylcysteine (NAC) pretreatment. Expression levels of apoptosis- and cell cycle-related genes (BAX, BCL-2, CASP3, CASP9, CCNB1, and CDK1) were analyzed by RT-qPCR. Cytoskeletal alterations were assessed by immunocytochemistry. In addition, the antitumor effects of the combination were validated in a three-dimensional (3D) tumor spheroid model. RES and CPT reduced cell viability in a dose- and time-dependent manner and demonstrated synergistic effects (CI < 1) at selected concentrations. Combination treatment significantly increased apoptosis, induced G2/M phase arrest, enhanced ROS accumulation, and promoted mitochondrial depolarization compared with single-agent treatments. NAC pretreatment attenuated ROS generation and partially restored cell viability, supporting a contributory role of oxidative stress in combination-induced cytotoxicity. At the transcriptional level, the RES + CPT combination significantly increased the BAX/BCL-2 ratio and upregulated CASP3 and CASP9 expression, while downregulating CCNB1 and CDK1, consistent with mitochondrial apoptotic activation and G2/M arrest. Immunocytochemical analysis revealed pronounced cytoskeletal disruption and apoptotic morphology in the combination group. Importantly, in the 3D spheroid model, co-treatment markedly reduced spheroid size and viability and enhanced cell death compared with monotherapies. The combination of RES and CPT exerts a synergistic anticancer effect in Y79 RB cells through coordinated mechanisms involving ROS accumulation, mitochondrial dysfunction, caspase activation, and G2/M phase arrest. The attenuation of cytotoxicity by NAC and the validation of efficacy in a 3D tumor spheroid model strengthen the mechanistic relevance of these findings. These results support further preclinical investigation of this combination strategy in in vivo models and normal retinal cell systems.