STXBP4 (syntaxin binding protein 4) is a vesicular trafficking regulator that inhibits SLC2A4 translocation to the plasma membrane by binding STX4A and preventing STX4A-VAMP2 interaction; insulin stimulation disrupts this inhibition, increasing SLC2A4 surface localization 1. Beyond glucose homeostasis, STXBP4 functions as a critical oncogenic regulator in squamous cell carcinomas. STXBP4 suppresses APC/C-mediated proteolysis of the ΔNp63 isoform, a master regulator of basal epidermal identity 2. In lung squamous cell carcinoma, STXBP4 overexpression correlates with ΔNp63 accumulation and drives tumor growth through PDGF receptor signaling; elevated STXBP4 associates with advanced disease stage, pleural involvement, and worse overall survival 3. Germline variants in STXBP4 (rs2628315) at the 17q22 locus associate with breast cancer risk, with preferential G-allele expression linked to increased susceptibility 1. Additionally, STXBP4 upregulation appears in SARS-CoV-2-infected lung tissue within alveolar-bronchiolization lesions, suggesting involvement in aberrant tissue regeneration 4. These findings position STXBP4 as a dual-function protein balancing metabolic regulation with oncogenic potential.