sq-23377 and Hyperplasia

To study the oncogenic activity of cyclin E in an in vivo system we generated transgenic mice expressing high levels of cyclin E in T-lymphocytes by using a construct containing the CD2 locus control region. These animals were neither predisposed to develop any tumors spontaneously nor showed an increased incidence when crossbred with Emu L-myc transgenic mice but developed hyperplasia in peripheral lymphoid organs at later age with an incidence of 27%. When treated with the DNA methylating carcinogen N-methylnitrosourea (MNU) that provokes the development of T-cell lymphomas, CD2-cyclin E transgenic animals came down with T-cell neoplasia showing a significant higher incidence (54%) than normal non transgenic controls (31%). In one of eight tumors that arose in normal MNU treated mice we could find an expected activating point mutation in the Ki-ras gene (12.5%). In contrast, the same mutation occurred in five of 16 tumors from CD2-cyclin E transgenic mice (31.2%). Whereas cyclin E overexpression alone did not lead to an increased CDK2 activity we observed in all tumors that emerged from either MNU treated normal mice or treated CD2-cyclin E transgenics a downregulation of p27KIP1 and a higher histone H1 kinase activity in CDK2 immunoprecipitates compared to normal tissue. These findings demonstrate that high level expression of cyclin E can predispose T-cells for hyperplasia and malignant transformation. However, the results also suggest that this activity of cyclin E is manifest only when other cooperating oncogenes in particular ras genes are present and activated. This would be consistent with our previous finding that cyclin E and Ha-Ras cooperate in focus formation assays in rat embryo fibroblasts.

Topics: Animals; Cell Transformation, Neoplastic; Cyclin E; Embryo, Mammalian; Fibroblasts; Genes, myc; Genes, ras; Hyperplasia; Ionomycin; Locus Control Region; Lymphoid Tissue; Lymphoma, T-Cell; Methylnitrosourea; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Mice, Transgenic; Point Mutation; Protamine Kinase; Rats; T-Lymphocytes; Tetradecanoylphorbol Acetate; Thymus Gland

The effects of CV-11974, a potent nonpeptide antagonist of the angiotensin II (AII) type-1 receptor (AT1), on cytosolic free calcium concentration ([Ca2+]i), hyperplasia, and hypertrophy of cultured vascular smooth muscle cells (VSMC) from rat aorta were studied. [Ca2+]i was measured by fura 2, and hyperplasia and hypertrophy were determined by incorporation of [3H]thymidine and [3H]leucine, respectively. CV-11974 had no effect on [Ca2+]i itself, but suppressed 10(-7) M AII-induced increase in [Ca2+]i dose dependently at concentrations from 10(-10) M and completely at 10(-7) M. CV-11974 suppressed both Ca2+ release from intracellular Ca2+ stores and Ca2+ influx from the extracellular space. However, CV-11974 had no effect on the increases in [Ca2+]i induced by prostaglandin F2 alpha (PGF2 alpha), a potent vasoconstrictor, or ionomycin, a Ca2+ ionophore. These results indicate that the suppressive effects of CV-11974 act on the binding of AII and its specific receptors. AII 10(-7) M increased the synthesis of DNA and protein to 1.5 and 1.7 times the control values, respectively. CV-11974 had no effect on synthesis of DNA or protein, but suppressed the AII-stimulated synthesis of DNA and protein dose dependently at concentrations > or = 10(-8) and 10(-10) M, respectively and completely at 10(-6) M. These results indicate that AII increases [Ca2+]i and synthesis of DNA and protein in VSMC through activation of AT1. CV-11974 showed no partial agonistic effects on AII. Thus, CV-11974 may act not only as an antihypertensive agent, but also as an inhibitor of vascular injury stimulated by AII.

Topics: Angiotensin II; Angiotensin Receptor Antagonists; Animals; Aorta, Thoracic; Benzimidazoles; Biphenyl Compounds; Calcium; Cells, Cultured; Cytosol; Dinoprost; DNA; Fura-2; Hyperplasia; Hypertrophy; Ionomycin; Muscle Proteins; Muscle, Smooth, Vascular; Rats; Rats, Wistar; Tetrazoles