A topical nanodiamond-ZnO activates IL24 and TNFSF15-associated cell death pathways in cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinoma (cSCC) is an ongoing clinical challenge due to its recurrence risk and the lack of well-tolerated agents for long-term or post-treatment use. Conventional chemotherapies, such as cisplatin or 5-fluorouracil, trigger apoptosis through genotoxic stress, but often cause damage to surrounding healthy tissue, limiting their suitability for daily application. To address this gap, we evaluated a topical formulation containing nanodiamond zinc-oxide (ND-ZnO) in the A431 epidermoid carcinoma cell model. ND-ZnO treatment was associated with a significant reduction in cancer cell viability and induction of extranuclear apoptotic features. Transcriptomic profiling identified enrichment of three transcriptional programs consistent with distinct cell death signaling axes: (1) interleukin-24 signaling associated with increased BAX and DR5 expression, (2) TNFSF15-mediated death receptor activation, and (3) a zinc-driven stress axis marked by elevated MT1G. Enrichment analysis highlighted pathways related to cytokine signaling, metal ion response, and programmed cell death. Compared to paclitaxel, ND-ZnO-treated cells showed fewer late apoptotic and necrotic events, a pattern consistent with a more regulated, low-necrosis death program. These findings provide transcriptomic evidence for a previously uncharacterized signaling profile associated with ND-ZnO treatment in cSCC cells, and propose ND-ZnO as a candidate for supportive care in cSCC management.