Chemical transformation of mouse liver cells results in altered cyclin D-CDK protein complexes

• Published in: Carcinogenesis (New York) 1998-06, Vol.19 (6), p.1093-1102
• Main Authors: GONZALES, A. J, GOLDSWORTHY, T. L, FOX, T. R
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Carcinogenesis, carcinogens and anticarcinogens; Carcinogens - toxicity; Carrier Proteins - metabolism; Cell Cycle Proteins; Cell Line; Cell Transformation, Neoplastic - drug effects; Chemical agents; Cyclin D1 - metabolism; Cyclin-Dependent Kinase Inhibitor p15; Cyclin-Dependent Kinase Inhibitor p16; Cyclin-Dependent Kinase Inhibitor p21; Cyclin-Dependent Kinases - metabolism; Cyclins - metabolism; Liver - drug effects; Liver - enzymology; Liver - pathology; Medical sciences; Mice; Mice, Inbred BALB C; Proliferating Cell Nuclear Antigen - metabolism; S Phase; Tumor Suppressor Proteins; Tumors
• ISSN: 0143-3334; 1460-2180; 1460-2180
• DOI: 10.1093/carcin/19.6.1093

Dysregulated cell proliferation is one phenotypic change associated with neoplasia. Key protein complexes involved in regulating cell division are composed of cyclins, cyclin-dependent kinases (CDK) and CDK inhibitors (CDI). Many virally transformed cells in culture exhibit disrupted cyclin-CDK-CDI complexes, suggesting that such changes may play a mechanistic role in viral transformation. To determine whether similar alterations may be involved in chemical carcinogenesis we characterized cyclin D1-CDK-CDI protein complexes in a non-tumorigenic mouse liver cell line and investigated whether complexes were altered after transformation with the genotoxic carcinogens N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or 3-methylcholanthrene (MC). In non-tumorigenic mouse liver cells cyclin D1 associated with CDK6, CDK4 or CDK2 to form binary (cyclin D1-CDK), tertiary (cyclin D1-CDK-p27KIP1) or quaternary (cyclin D1-CDK-p21WAF1-PCNA) complexes. After chemical transformation of mouse liver cells with either MC or MNNG, select cyclin D1-CDK-CDI protein complexes were altered. In MC-transformed cells formation of various binary, tertiary and quaternary cyclin D1-CDK-(CDI) protein complexes was reduced, resulting in decreased CDK4 kinase activity. Interestingly, CDK6 kinase activity was dramatically elevated due to high levels of cyclin D3 in association with CDK6. In MNNG-transformed cells select cyclin D1-CDK6-CDI and cyclin D1-CDK2-CDI protein complexes were altered but CDK6 and CDK4 kinase activity remained unaffected. Distinct changes in cyclin D1-CDK-CDI complexes found between the two chemically transformed mouse liver cell lines suggest that each cell line harbored unique mutations or alterations that differentially contributed to stabilization of cyclin D1-CDK-CDI holoenzymes. p53 gene mutations were not detected in the MC- or MNNG-transformed mouse liver cell lines and thus were not involved in disrupting cyclin D1-CDK-CDI protein complexes. In summary, this study presents evidence that D-type CDK protein complexes can be altered physically and functionally after chemical transformation with genotoxic carcinogens, suggesting that components of the cell cycle machinery can be targeted during chemical carcinogenesis.