Abstract Ultraviolet (UV) radiation-induced skin damage plays a pivotal role in the pathogenesis of melanoma, a highly aggressive and fatal form of skin cancer. Shikonin, naturally occurring nathoquinone , is well-known for its inhibitory effects on phosphoinositide 3-kinase (PI3K) and mitogen-activated protein (MAP) kinase signaling pathways. It has previously been demonstrated to exert effects against various non-melanoma skin cancers. In this study, we investigated the effects of Shikonin treatment on UVB-irradiated B16F10 melanoma cells, revealing a dose-dependent reduction in cell viability and an enhancement of apoptosis. Invitro findings indicate that the pro-apoptotic effects of shikonin in UVB-exposed B16F10 cells are mediated by several mechanisms, including the generation of reactive oxygen species (ROS), modulation of the antioxidant defense response, and mitochondrial membrane potential (ΔΨM) depolarization. Further supporting the apoptotic role of Shikonin, we observed DNA fragmentation, caspase activation, poly(ADP-ribose) polymerase (PARP) cleavage, and an increase in sub-G2 cell populations. Shikonin treatment also significantly attenuated MEK-ERK signaling, influenced the PI3K/Akt pathway, and potentially inhibited UVB-induced nuclear translocation of NF-κB. Additionally, co-treatment with UVB and Shikonin led to a decrease in the Bcl-2/Bax ratio and upregulated the expression of pro-apoptotic proteins Bax and caspases. Collectively, these data suggest that Shikonin may act as a potential therapeutic agent for melanoma when combined with UVB exposure, providing a novel avenue for future treatment strategies. Citation Format: Aalim Maqsood Bhat, Sheikh Tasduq Abdullah. Shikonin, a strong inhibitor of Phosphoinositide 3-Kinase (PI3K) and Mitogen-Activated Protein (MAP) Kinase pathways, induces cell death in UV-B irradiated B16F10 melanoma cells. [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Targeted Therapies in Combination with Radiotherapy; 2025 Jan 26-29; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(2_Suppl):Abstract nr A013.
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