title: cAMP-dependent cytosolic mislocalization of p27(kip)-cyclin D1 during quinol-thioether-induced tuberous sclerosis renal cell carcinoma.
abstract: The loss of tuberin, the tuberous sclerosis-2 (Tsc-2) gene product, is associated with cytoplasmic mislocalization of p27 in uterine leiomyomas derived from Eker rats (Tsc-2(EK/+)) and in human metastatic renal cell carcinoma tissue. Signaling associated with cytoplasmic mislocalization of p27 in renal cancer is relatively unknown. Renal tumors derived from 2,3,5-tris-(glutathion-S-yl)hydroquinone (TGHQ)-treated Tsc-2(EK/+) rats, and null for tuberin, display elevated nuclear and cytosolic p27, with parallel increases in cytosolic cyclin D1 levels. Similar changes are observed in TGHQ-transformed renal epithelial cells derived from Tsc-2(EK/+) rats (QTRRE cells), which, in addition to the cytoplasmic mislocalization of p27 and cyclin D1, exhibit high ERK, B-Raf, and Raf-1 kinase activity. Renal tumor xenografts, derived from subcutaneous injection of QTRRE cells into nude mice, also display increases in cytosolic mislocalization of p27 and cyclin D1. Dibutyryl cAMP and/or phosphodiesterase inhibitors (PIs; pentoxifylline or theophylline) increase Rap1B activation, B-Raf kinase activity, and cytosolic p27/cyclin D1 protein levels in QTRRE cells. Inhibition of Raf kinases with either sorafenib or B-Raf small interfering RNA (siRNA) caused a mitogen-activated protein kinase-mediated downregulation of p27. Moreover, decreases in cyclin D1 were also associated with p27 siRNA knockdown in QTRRE cells. Finally, theophylline-mediated increases in p27 and cyclin D1 were attenuated by sorafenib, which modulated Raf/MEK/ERK signaling. Collectively, these data suggest that the cAMP/Rap1B/B-Raf pathway modulates the expression of p27 and the cytoplasmic mislocalization of p27-cyclin D1 in tuberous sclerosis gene-regulated-renal cancer. Therefore, the loss of tuberin and engagement of the cAMP pathway may independently direct p27-cyclin D1 cytosolic stabilization during renal tumor formation.
authors.affiliation: Department of Pharmacology and Toxicology, Southwest Environmental Health Sciences Center, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Cohen
authors.forename: Kimberly Y
authors.initials: KY
authors.lastname: Tham
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Mastrandrea
authors.forename: Alfred C
authors.initials: AC
authors.lastname: Gallegos
authors.forename: Terrence J
authors.initials: TJ
authors.lastname: Monks
authors.forename: Serrine S
authors.initials: SS
authors.lastname: Lau
mesh_terms: D000818:Animals; D001557:Benzenesulfonates / Q000378:metabolism; D003994:Bucladesine / Q000494:pharmacology*; D002292:Carcinoma, Renal Cell / Q000139:chemically induced*; D002460:Cell Line; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D005978:Glutathione / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D007680:Kidney Neoplasms / Q000139:chemically induced*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D009536:Niacinamide / Q000031:analogs & derivatives; D010431:Pentoxifylline / Q000378:metabolism; D010671:Phenylurea Compounds; D010726:Phosphodiesterase Inhibitors / Q000378:metabolism; D048493:Proto-Oncogene Proteins B-raf / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D011725:Pyridines / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D000077157:Sorafenib; D013806:Theophylline / Q000378:metabolism; D014402:Tuberous Sclerosis / Q000378:metabolism*; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D001557:Benzenesulfonates; C530106:Ccnd1 protein, rat; C493962:Cdkn1b protein, rat; D006873:Hydroquinones; D010671:Phenylurea Compounds; D010726:Phosphodiesterase Inhibitors; D011725:Pyridines; D034741:RNA, Small Interfering; C000624653:TSC2 protein, human; C000624654:Tsc2 protein, mouse; C000624655:Tsc2 protein, rat; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; C078765:2,3,5-(triglutathion-S-yl)hydroquinone; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D009536:Niacinamide; D003994:Bucladesine; D000077157:Sorafenib; D013806:Theophylline; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D005978:Glutathione; D010431:Pentoxifylline