Adenosine monophosphate-activated protein kinase (AMPK) is a critical metabolic sensor and redox modulator. Despite evidence linking AMPK tumor suppressor functions, the role of AMPK in chromosome instability and tumorigenesis is obscure.
Murine embryo fibroblasts (MEF) were isolated from AMPK alpha1 knock out (AMPKα1-KO), AMPKα2-KO, and wild type (WT) C57BL/6J mouse embryos, and immortalized by employing standard 3T3 protocol to investigate the mechanisms of chromosomal instability and fibroblast-mediated angiogenesis. Chromatin proteins and aneuploidy were monitored in cultured MEFs by Western blot and metaphase spread. Athymic nude mice were employed to test tumorigenesis of fibroblasts in vivo.
Deletion of AMPKα1, but not AMPKα2, exhibited a significant reduction in centromere-specific binding proteins C (CENP-C) and elevation of Polo-like kinase 4 (PLK4), a trigger of centriole biogenesis. Both CENP-C and PLK4 may be associated with the increased aneuploid (34%-66%) and micronucleus. Allograft model data demonstrated that knock out of AMPKα1 enhanced the cellular proliferation of immortalized MEFs, vascularization, and tumor development in athymic nude mice in vivo. Mechanistically, it was shown that the protein level of noncanonical nuclear factor kappa B2 (NF-κB2)/p52 was elevated in AMPKα1-KO MEFs and was responsible for induction of erythropoietin (Epo) expression. Lastly, the most conclusive evidence for AMPKα1-dependent inhibition of fibroblast-mediated angiogenesis as well as tumor progression was that the allograft growth of the inoculated AMPKα1-KO MEFs was attenuated by treatment with Epo neutralization antibody.
Taken together, these data indicate that AMPKα1 activation opposes tumor development and its loss fosters tumor progression in part by controlling chromosome stability and angiogenesis that support tumor growth.
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Georgia State University
National Institutes of Health, American Heart Association
All authors have declared no conflicts of interest.