AbstractAccumulating evidence demonstrates that cancer stemness is essential for both tumor development and progression, regulated by multi-layer factors at genetic, epigenetic and micro-environmental levels. However, how to target stemness-driven plasticity and eliminate metastasis remains one of the biggest challenges in the clinic. We aim to identify novel molecular mechanisms underlying stemness of triple negative breast cancer (TNBC) which frequently metastasizes to the visceral organs but lacks targeted therapies. Following our previous discovery of miR-206 as an epigenetic suppressor of tumorigenesis and metastasis, we now report that the integrin receptor CD49b-encodingITGA2is an oncogenic target of miR-206 in TNBC.ITGA2knockdown abolished cancer stemness (mammosphere formation, pluripotency marker expression, and FAK phosphorylation), inhibited cell cycling, compromised migration and invasion, and thereby decreasing lung metastasis of TNBC. RNA sequencing analyses of breast cancer cells revealed thatITGA2knockdown inhibits gene expression essential for both classical integrin-regulated pathways (cell cycle, wounding response, protein kinase, etc) and newly identified pathways such as lipid metabolism. Notably,ACLY-encoded ATP citrate lyase is one of the top targets in CD49b-regulated lipid metabolism andCCND1-encoded Cyclin D1 represents regulation of cell cycle and many other pathways. ACLY, known to catalyze the formation of cytosolic acetyl-CoA for fatty acid biosynthesis, is indispensable for cancer stemness. Overexpression ofCCND1rescues the phenotype ofITGA2knockdown-induced cell cycle arrest. High expression levels of theITGA2/ACLY/CCND1axis are correlated with an unfavorable relapse-free survival of patients with high grade breast cancer, in both basal-like and other subtypes. This study identifiesITGA2as a potential therapeutic target of TNBC stemness and metastasis.
CDK4 regulates cancer stemness and is a novel therapeutic target for triple-negative breast cancer
