Subtype-specific roles of STIM1 in non-keratinising nasopharyngeal cancer: The miR-200a-3p–PTEN/ATP2A2 axis in undifferentiated and the miR-185-5p/miR-34a-3p/miR-375–AKT1/RYR2 axis in differentiated subtypes

Non-keratinising nasopharyngeal cancer (NK-NPC), highly prevalent in Southeast Asia, remains a major clinical challenge due to late-stage diagnosis and limited targeted therapies. The undifferentiated subtype, strongly linked to Epstein–barr virus (EBV) infection, exhibits aggressive behaviour, whereas the differentiated subtype is largely influenced by environmental and genetic factors. Although calcium signalling has been increasingly implicated in tumour progression, the subtype-specific regulation of stromal interaction molecule 1 (STIM1) remains poorly understood. This study aimed to elucidate the regulatory mechanisms and functional impact of STIM1 in undifferentiated and differentiated NK-NPC subtypes. A comprehensive transcriptomic, functional, and in silico characterisation of STIM1 silencing was performed using DsiRNA in two NK-NPC models. Functional assays assessed cell proliferation, migration, stemness, and the regulation of calcium and reactive oxygen species. In silico analyses, including differential expression profiling, pathway enrichment, and integrated miRNA–mRNA network analysis, were conducted to identify molecular pathways and subtype-specific regulatory interactions associated with STIM1. STIM1 suppression modulated key genes involved in calcium signalling and oncogenic pathways, including PI3K/AKT pathway, cell cycle control, and apoptosis. This silencing induced compensatory upregulation of calcium channel genes (Calcium release-activated calcium modulator 1 (ORAI1), ryanodine receptor 2 (RYR2), sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (ATP2A2)), sustained Phosphatase and tensin homolog (PTEN) activation, and enhanced pro-apoptotic gene expression (BAX, CDH1). Functionally, STIM1 knockdown reduced stemness in both nasopharyngeal cancer (NPC) subtypes. In undifferentiated cells, STIM1 knockdown led to decreased proliferation and migration. In contrast, differentiated cells showed increased proliferation and migration despite reduced stemness, likely due to activation of compensatory pathways. miRNA profiling identified miR-200a-3p, miR-185-5p, miR-375, miR-34a-3p, and let-7b-5p as regulators of STIM1-associated signalling. Distinct regulatory axes were defined: the miR-200a-3p–PTEN/ATP2A2 pathway in undifferentiated NPC and the miR-185-5p/miR-34a-3p/miR-375–AKT1/RYR2 axis in the differentiated subtype. This integrative experimental computational investigation provides novel mechanistic insights into STIM1-centred regulation, revealing distinct molecular networks across NPC subtypes and uncovering unique regulatory relationships that enhance understanding of STIM1’s biological significance in NPC pathogenesis. GRAPHICAL ABSTRACT STIM1 drives subtype-specific regulation in NK-NPC via the miR-200a-3p-PTEN/ATP2A2 (undifferentiated) and miR-185-5p/miR-34a-3p/miR-375-AKT1/RYR2 (differentiated) axes.