title: Inhibition of cdk2 kinase activity by methylselenocysteine in synchronized mouse mammary epithelial tumor cells.
abstract: Methylselenocysteine (MSC), an organic selenium compound has significant anticarcinogenic activity against mammary tumorigenesis. Previous experiments have demonstrated that MSC and inorganic selenite inhibit mammary cell (TM6 cell line) growth through different pathways. The present investigation demonstrated that MSC arrested cells in S phase during the TM6 cell cycle, which was followed by cells entering apoptosis at 48 h. Methylselenocysteine specifically affected the cdk2 kinase activity of the TM6 cells (54% reduction) at 16 h after release from growth arrest. The cdk4 kinase activity did not change during the cell cycle, confirming that cells had passed the G1 checkpoint and had entered S phase. The amount of cyclin E associated with cdk2 was increased by MSC by the 12 h time point, thereby facilitating entry of cells into S phase. Afterwards, cyclin E and cyclin A associated with cdk2 did not change for the remainder of the cell cycle. The data demonstrate that inhibition of mammary cell growth by MSC is mediated by alterations in progression of cells through S phase. The decrease in cdk2 kinase activity is coincident with prolonged arrest in S phase. One consequence of prolonged arrest may be apoptosis.
authors.affiliation: Cell Biology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: R
authors.initials: R
authors.lastname: Sinha
authors.forename: D
authors.initials: D
authors.lastname: Medina
mesh_terms: D000818:Animals; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000187:drug effects*; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D003545:Cysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D004848:Epithelium / Q000187:drug effects / Q000201:enzymology; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000201:enzymology*; D051379:Mice; D016566:Organoselenium Compounds / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D017279:Selenocysteine / Q000031:analogs & derivatives; D014407:Tumor Cells, Cultured
chemical_list: D016213:Cyclins; D016566:Organoselenium Compounds; D011518:Proto-Oncogene Proteins; D017279:Selenocysteine; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; C495902:Cdk4 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D003545:Cysteine; C002979:selenomethylselenocysteine