Sparking malignancy: nicotine as a driver of stemness and metastasis in triple‐negative breast cancer ^†

Triple-negative breast cancer (TNBC) lacks expression of estrogen receptor (ER), progesterone receptor (PR), and HER2, and remains one of the most aggressive and therapeutically challenging breast cancer subtypes, marked by early relapse, metastasis, and limited targeted treatment options. In a recent study published in The Journal of Pathology, Kuo et al provide compelling evidence that nicotine exposure, whether from tobacco smoke or e-cigarette vapor, drives TNBC progression by promoting stem-like and metastatic phenotypes. Integrating clinical datasets, patient tissues, cell lines, and in vivo models, the authors demonstrate that nicotine enhances tumor aggressiveness via coordinated upregulation of CHRNA9 and IGF1R. Silencing either receptor attenuates nicotine-induced stemness, invasion, and metastasis, revealing a therapeutically actionable axis. High expression of CHRNA9 and IGF1R correlates with poor clinical outcomes and may define a nicotine-exposed TNBC subgroup that could benefit from IGF1R-targeted therapy or repurposed nicotinic receptor antagonists. These findings underscore the role of environmental exposures in shaping tumor biology and offer a mechanistic basis for the poorer prognosis observed in smokers with breast cancer. © 2025 The Pathological Society of Great Britain and Ireland.