Aspirin mediates histone methylation that inhibits inflammation-related stemness gene expression to diminish cancer stemness via COX-independent manner

BACKGROUND: The widely recognized anti-cancer potential of aspirin has created a broad interest to explore the clinical benefits of aspirin in cancer therapy. However, the current understanding of the molecular mechanisms involved in the anti-cancer potential of aspirin remains limited. METHODS: Cancer stemness assays which contained ALDH, side population, chemo-resistance, sphere formation, and tumorigenesis were performed to validate aspirin function in vitro and in vivo. Histone modification assay was performed to check the effect of aspirin on histone methylation as well as the activity of HDAC and KDM6A/B. Inhibitor in vivo assay was performed to evaluate therapeutic effects of various inhibitor combination manners. RESULTS: In regards to in vitro studies, aspirin diminishes cancer cell stemness properties which include reducing the ALDH+ subpopulation, side population, chemo-resistance, and sphere formation in three cancer types. In regards to in vivo studies, aspirin decreases tumor growth and metastasis and prolongs survival. In addition, our results showed that aspirin inhibits inflammation-related stemness gene expression (especially ICAM3) identified by a high-throughput siRNA platform. In regards to the underlying molecular mechanism of action, aspirin reduces histone demethylase (KDM6A/B) expression that mediates histone methylation and suppresses gene expression via a COX-independent manner. In regards to therapeutic strategies, aspirin combined HDM inhibitors, ICAM3 downstream signaling Src/PI3K inhibitors, or ICAM3 inhibitor Lifitigrast prevents cancer progression in vivo. CONCLUSIONS: The aforementioned findings suggest a molecular model that explains how aspirin diminishes cancer cell stemness properties. These findings may provide novel targets for therapeutic strategies involving aspirin in the prevention of cancer progression.