<i>ITGA2</i> Promotes Breast Cancer Stemness and Metastasis Through Enhanced <i>ACLY</i> and <i>CCND1</i> Expression

Abstract

Background: Cancer metastasis is largely incurable and accounts for 90% of breast cancer deaths, especially for the aggressive basal-like or triple negative breast cancer (TNBC). Accumulating evidence demonstrates that integrins are essential for normal development and malignancies; however, the molecular functions and clinical relevance for each integrin subunit in cancer metastasis have yet to be fully elucidated. Methods: Combining patient database analyses and functional studies, we examined the association of integrin family members with clinical outcomes as well as their connection with previously identified microRNA regulators of metastasis, such as miR-206 that inhibits stemness and metastasis of TNBC. Findings: Here we report that the integrin receptor CD49b-encoding ITGA2, a direct target of miR-206, promotes breast cancer stemness and metastasis through maintaining ACLY and CCND1 levels. ITGA2 knockdown suppressed self-renewal related mammosphere formation and pluripotency marker expression, inhibited cell cycling, compromised migration and invasion, and therefore decreased lung metastasis of breast cancer. RNA sequencing analyses revealed that ITGA2 knockdown inhibits genes related to cell cycle regulation and lipid metabolism such as CCND1 and ACLY. ACLY-encoded ATP citrate lyase is essential to maintain cellular acetyl-CoA levels and mammosphere formation of breast cancer cells. Overexpression of CCND1 rescues the phenotype of ITGA2 knockdown-induced cell cycle arrest. Interpretation: We identified that the miR-206/ITGA2/ACLY/CCND1 axis is associated with relapse-free survival of the patients with high grade breast cancer, especially basal-like breast cancer, possibly serving as potential biomarkers and therapeutic targets of breast cancer stemness and metastasis. Funding Statement: This manuscript has been partially supported by NIH/NCI grants R00CA160638 (H.L. & V.A.) and R01CA213843 (R.A.K), American Cancer Society grant ACS127951-RSG-15-025-01-CSM (H.L.); the Susan G. Komen Foundation CCR15332826 (H.L.) and CCR18548501 (X.L); the Department of Defense W81XWH-16-1-0021 (H.L.); the Lynn Sage Cancer Research Foundation (X.L. and H. L.); Northwestern University's Endocrinology Training Grant T32DK007169-39 (A.H.). Declaration of Interests: There is no conflict of interest for the authors of this manuscript. Ethics Approval Statement: All animal procedures complied with the NIH Guidelines for the Care and Use of Laboratory Animals and were approved by the respective Institutional Animal Care and Use Committees.