Journal Article

Disorders in cell circuitry during multistage carcinogenesis: the role of homeostasis

I.Bernard Weinstein

in Carcinogenesis

Volume 21, issue 5, pages 857-864
Published in print May 2000 | ISSN: 0143-3334
Published online May 2000 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/21.5.857
Disorders in cell circuitry during multistage carcinogenesis: the role of homeostasis

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The multistage process of carcinogenesis involves the progressive acquisition of mutations, and epigenetic abnormalities in the expression, of multiple genes that have highly diverse functions. An important group of these genes are involved in cell cycle control. Thus, cyclin D1 is frequently overexpressed in a varety of human cancers. Cylin D1 plays a critical role in carcinogenesis because (i) overexpression enhances cell transformation and tumorigenesis, and enhances the amplification of other genes, and (ii) an antisense cyclin D1 cDNA reverts the malignant phenotype of carcinoma cells. Therefore, cyclin D1 may be a useful biomarker in molecular epidemiology studies, and inhibitors of its function may be useful in both cancer chemoprevention and therapy. We discovered a paradoxical increase in the cell cycle inhibitors protein p27Kip1 in a subset of human cancers, and obtained evidence for homeostatic feedback loops between cyclins D1 or E and p27Kip1. Furthermore, derivatives of HT29 colon cancer cells with increased levels of p27Kip1 showed increased sensitivity to induction of differentiation. This may explain why decreased p27Kip1 in a subset of human cancers is associated with a high grade (poorly differentiated) histology and poor prognosis. Agents that increase cellular levels of p27Kip1 may, therefore, also be useful in cancer therapy. Using an antisense Rb oligonucleotide we obtained evidence that the paradoxical increase in pRb often seen in human colon cancers protects these cells from growth inhibition and apopotosis. On the basis of these, and other findings, we hypothesize that homeostatic feedback mechanisms play a critical role in multistage carcinogenesis. Furthermore, because of their bizarre circuitry, cancer cells suffer from `gene addiction' and `gene hypersensitivity' disorders that might be exploited in both cancer prevention and chemotherapy.

Keywords: CDI, CDK inhibitor protein; CDK, cyclin-dependent kinase.

Journal Article.  7080 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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