title: Pharmacological inhibition of Polo-like kinase 1 (PLK1) by BI-2536 decreases the viability and survival of hamartin and tuberin deficient cells via induction of apoptosis and attenuation of autophagy.
abstract: The mechanistic target of rapamycin complex 1 (mTORC1) increases translation, cell size and angiogenesis, and inhibits autophagy. mTORC1 is negatively regulated by hamartin and tuberin, the protein products of the tumor suppressors TSC1 and TSC2 that are mutated in Tuberous Sclerosis Complex (TSC) and sporadic Lymphangioleiomyomatosis (LAM). Hamartin interacts with the centrosomal and mitotic kinase polo-like kinase 1 (PLK1). Hamartin and tuberin deficient cells have abnormalities in centrosome duplication, mitotic progression, and cytokinesis, suggesting that the hamartin/tuberin heterodimer and mTORC1 signaling are involved in centrosome biology and mitosis. Here we report that PLK1 protein levels are increased in hamartin and tuberin deficient cells and LAM patient-derived specimens, and that this increase is rapamycin-sensitive. Pharmacological inhibition of PLK1 by the small-molecule inhibitor BI-2536 significantly decreased the viability and clonogenic survival of hamartin and tuberin deficient cells, which was associated with increased apoptosis. BI-2536 increased p62, LC3B-I and GFP-LC3 punctae, and inhibited HBSS-induced degradation of p62, suggesting that PLK1 inhibition attenuates autophagy. Finally, PLK1 inhibition repressed the expression and protein levels of key autophagy genes and proteins and the protein levels of Bcl(-)2 family members, suggesting that PLK1 regulates both autophagic and apoptotic responses. Taken together, our data point toward a previously unrecognized role of PLK1 on the survival of cells with mTORC1 hyperactivation, and the potential use of PLK1 inhibitors as novel therapeutics for tumors with dysregulated mTORC1 signaling, including TSC and LAM.
authors.affiliation: a Department of Biochemistry and Molecular Biology ; Drexel University College of Medicine ; Philadelphia , PA USA.
authors.forename: Matthildi
authors.initials: M
authors.lastname: Valianou
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Cox
authors.forename: Benjamin
authors.initials: B
authors.lastname: Pichette
authors.forename: Shannon
authors.initials: S
authors.lastname: Hartley
authors.forename: Unmesha Roy
authors.initials: UR
authors.lastname: Paladhi
authors.forename: Aristotelis
authors.initials: A
authors.lastname: Astrinidis
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001343:Autophagy / Q000187:drug effects* / Q000235:genetics; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002999:Clone Cells; D005786:Gene Expression Regulation / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011621:Pteridines / Q000494:pharmacology*; D020123:Sirolimus / Q000494:pharmacology; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000172:deficiency* / Q000378:metabolism; D000097869:Polo-Like Kinase 1
chemical_list: D018797:Cell Cycle Proteins; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011621:Pteridines; D020123:Sirolimus; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; D000097869:Polo-Like Kinase 1; C518477:BI 2536; C000624650:TSC1 protein, human; C000624653:TSC2 protein, human; C000624651:Tsc1 protein, mouse; C000624654:Tsc2 protein, mouse
keywords: BI-2536; LAM, Lymphangioleiomyomatosis; MEF, mouse embryonic fibroblasts, mTORC1, mechanistic target of rapamycin complex 1; PLK1, polo-like kinase 1; TSC, Tuberous Sclerosis Complex; apoptosis; autophagy; lymphangioleiomyomatosis; mechanistic target of rapamycin; polo-like kinase 1; tuberous sclerosis complex