Selective suppression of inducible PFKFB3 isoforms as a strategy to inhibit tumor angiogenesis while preserving endothelial viability

Tumor angiogenesis is sustained by metabolic reprogramming within endothelial cells, enabling vessel sprouting in the hypoxic tumor microenvironment. The glycolytic regulator 6-phosphofructo-2-kinase/ fructose-2,6-biphosphatase 3 (PFKFB3) is a central driver of this pathological angiogenic response. While complete inhibition of PFKFB3 suppresses angiogenesis, it also disrupts endothelial viability, limiting therapeutic utility. In contrast, partial inhibition consistently reduces abnormal vessel sprouting while preserving baseline endothelial function, revealing a therapeutic window that remains mechanistically unexplained. Here, we advance a unifying framework in which tumor angiogenesis depends on inducible, context-specific PFKFB3 isoforms that are distinct from those supporting endothelial homeostasis. We synthesize evidence that tumor-derived metabolic signals, including lactate and vascular endothelial growth factor (VEGF), activate endothelial glycolysis through PFKFB3, and argue that this activation occurs within a hypoxia-driven, RNA-regulated program that likely reshapes PFKFB3 isoform expression. Isoforms with distinct regulatory domains, stability, and subcellular localization have been identified in other systems, providing a mechanistic basis for functional specialization. We propose that the apparent selectivity of partial PFKFB3 inhibition arises from preferential suppression of inducible, angiogenesis-associated isoforms rather than uniform attenuation of glycolytic flux. This interpretation resolves the long-standing paradox between anti-angiogenic efficacy and endothelial toxicity and challenges the prevailing dose-centric model of PFKFB3 targeting. Although direct isoform-specific evidence in endothelial cells remains limited, the convergence of metabolic, transcriptional, and splicing regulation strongly supports this model. Reframing PFKFB3 as an isoform-regulated metabolic program shifts the therapeutic paradigm from global enzymatic inhibition to isoform-selective modulation. This strategy offers a path toward more precise, mechanism-based anti-angiogenic therapies that suppress tumor vascularization while preserving essential endothelial function.