Introduction. Triple negative breast cancer (TNBC) is very aggressive, has a higher metastatic rate than other breast cancer subtypes, and lacks traditional targetable factors. AMPK-activated protein kinase (AMPK) is an important energy regulator within the cell that also impacts cancer progression. AMPK's catalytic subunit is composed of α1 and α2 isoforms, but little is known about their individual roles in TNBC. The purpose of this study was to establish the specific function of each isoform in TNBC with respect to expression, cell proliferation, cell cycle progression, and metabolism.
Methods. (i) Immunohistochemistry, immunofluorescence, and immunoblotting were used to determine the expression and localization of AMPKα1 and AMPKα2 in TNBC PDX samples or cell lines. (ii) To study the role of each isoform individually, TNBC cells were transfected with siRNA to NTC, AMPKα1, or AMPKα2 (50 nM) and were either harvested for immunoblotting or subseeded for cell cycle analysis, proliferation assays, or Seahorse analysis.
Results. (i) AMPKα1 expression was localized in the cytoplasm of all 9 TNBC PDX cell lines, whereas AMPKα2 was expressed predominantly in the nucleus in 6 of the 9 of TNBC samples. IF analysis of MDA-MB-231 cells confirmed expression findings in the PDX cell lines with AMPKα1 expression noted in the cytoplasm and AMPKα2 expression in both the cytoplasm and nucleus. (ii) siRNA knockdown of AMPKα1 or AMPKα2 induced G1 cell cycle arrest and decreased proliferation of MDA-MB-231 cells. Moreover, knockdown of AMPKα1 decreased levels of cyclin D1 in MDA-MB-231, MDA-MB-468, and BT-20 cells. siRNA knockdown of AMPKα1, but not AMPKα2, led to decreased basal and compensatory glycolysis in MDA-MB-231 cells.
Conclusions. Our findings indicate that both AMPKα1 and AMPKα2 can impact cell cycle progression and proliferation in TNBC; both isoforms promote progression through the cell cycle, thus supporting the proliferative capacity of TNBC. Importantly, AMPKα1 may also affect TNBC proliferation by increasing energy availability through glycolysis.
Citation Format: Jeremy Johnson, Piotr Richahou, B. Mark Evers. AMPK alpha1 and AMPK alpha 2 control TNBC proliferation through cell cycle regulation [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 93.