Loss of p27Kip1 from cyclin e/cyclin-dependent kinase (CDK) 2 but not from cyclin D1/CDK4 complexes in cells transformed by polyamine biosynthetic enzymes

• Published in: Cancer research (Chicago, Ill.) Vol. 60; no. 18; pp. 5244 - 5253
• Main Authors: RAVANKO, Kirsi, JÄRVINEN, Kristiina, PAASINEN-SOHNS, Aino, HÖLTTÄ, Erkki
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 15-09-2000
• Subjects: 3T3 Cells - cytology; 3T3 Cells - enzymology; 3T3 Cells - metabolism; Adenosylmethionine Decarboxylase - biosynthesis; Adenosylmethionine Decarboxylase - genetics; Adenosylmethionine Decarboxylase - metabolism; Animals; Biological and medical sciences; Blotting, Northern; CDC2-CDC28 Kinases; Cell Cycle - physiology; Cell Cycle Proteins; Cell Division - physiology; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Cell Transformation, Neoplastic - genetics; Cell Transformation, Neoplastic - metabolism; Cyclin D1 - metabolism; Cyclin E - metabolism; Cyclin-Dependent Kinase 2; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase Inhibitor p27; Cyclin-Dependent Kinases - metabolism; DNA, Complementary - genetics; DNA, Complementary - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Profiling; Humans; Mice; Mice, Nude; Microtubule-Associated Proteins - biosynthesis; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - metabolism; Molecular and cellular biology; Ornithine Decarboxylase - biosynthesis; Ornithine Decarboxylase - genetics; Ornithine Decarboxylase - metabolism; Phosphorylation; Plasmids - genetics; Protein-Serine-Threonine Kinases - metabolism; Proto-Oncogene Proteins; Rats; Retinoblastoma Protein - metabolism; Transfection; Tumor Suppressor Proteins; Cell proliferation; Lyases; Biosynthesis; Cyclin D1; Cell transformation; Adenosylmethionine decarboxylase; Transfection; Enzymatic activity; Carboxy-lyases; Malignant transformation; Cell cycle; Established cell line; Mechanism of action; Tumor cell; Human; Polyamine; Enzyme; Transferases; Enzyme inhibitor; Retinoblastoma protein; Ornithine decarboxylase; Gene expression; In vitro; Carbon-carbon lyases; Protein kinase; Fibroblast
• ISSN: 0008-5472; 1538-7445

Cancer cells are known to display up-regulation of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC), the key enzymes in the biosynthesis of polyamines that are essential for cellular proliferation. We have shown previously that overexpression of ODC or AdoMetDC alone can induce tumorigenic transformation of rodent fibroblasts. Because the subversion of normal cell cycle control is thought to be a crucial event in cancer development, we examined ODC- and AdoMetDC-transformed fibroblasts for alterations in the cell cycle components. The level of cyclin D1 and cyclin D1-dependent kinase and total cyclin-dependent kinase (CDK) 4 activities were elevated in the ODC transformants and particularly in the AdoMetDC transformants. Cyclin E content was not elevated, but a moderate increase in cyclin E-dependent kinase activity was seen in both cells. Total CDK2 activity was increased only in the ODC-transformed cells. The amount of the p27Kip1 CDK inhibitor was greatly decreased in both transformants. Nevertheless, p27Kip1 was present in the active cyclin D1/CDK4 complexes in the cells but absent from the cyclin E/CDK2 complexes. Restoration of p27Kip1 expression in the ODC- and AdoMetDC-transformed cells by transfection resulted in growth inhibition, but not in morphological reversion. An elevation in the level of hyperphosphorylated retinoblastoma protein was observed mainly in the ODC-transformed cells. These results suggest that the expression of ODC or AdoMetDC may affect cell cycle regulation in many ways. However, the largest common effect, which is therefore potentially relevant to some aspects of transformation, appears to be the constitutive down-regulation of p27Kip1 and its loss from the cyclin/CDK2 complexes.