Crosstalk between integrin signaling and NAD⁺ biosynthetic pathways promotes glycolysis, proliferation, survival, and tumor growth in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with limited therapeutic options. Here, we investigated how integrin-dependent signaling pathways regulate tumor metabolism and therapeutic vulnerability in TNBC. Pharmacological inhibition of the integrin/FAK axis and/or BRD4 induced cell cycle arrest, autophagy, and senescence in highly proliferative cells, consistent with a metabolic stress phenotype. Metabolomic analyses using [U-¹³C]-glucose revealed a marked suppression of glycolytic carbon flux, accompanied by an approximately 30-47% reduction in intracellular NAD⁺ levels and coordinated alterations in NADH and tricarboxylic acid (TCA) cycle intermediate α-ketoglutarate. Mechanistically, we identified nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in NAD⁺ biosynthesis, as a central metabolic node integrating signaling/function of the two axes. NAMPT expression/activity was sustained transcriptionally or post-translationally, including sirtuin-associated deacetylation and neddylation-dependent proteasomal turnover. In BRCA1/2-deficient TNBC, integrin-FAK and NAMPT/NAD+ pathways converged on Wnt/β-catenin signaling to regulate DNA repair, and response to PARP1/2 inhibitors. Co-inhibiting FAK and NAMPT synergistically suppressed tumor growth by approximately 80%. Elevated stromal NAMPT expression was associated with a trend toward favorable clinical outcomes. Collectively, these findings uncover a previously unrecognized crosstalk between integrin/FAK and NAMPT/NAD⁺ pathways in TNBC and identify a synthetic lethal-like therapeutic vulnerability that warrants further evaluation in clinically relevant models.