Document Detail

Cytometry of cyclin proteins.
MedLine Citation:
PMID:  8875049     Owner:  NLM     Status:  MEDLINE    
Cyclins are key components of the cell cycle progression machinery. They activate their partner cyclin-dependent kinases (CDKs) and possibly target them to respective substrate proteins within the cell. CDK-mediated phosphorylation of specific sets of proteins drives the cell through particular phases or checkpoints of the cell cycle. During unperturbed growth of normal cells, the timing of expression of several cyclins is discontinuous, occurring at discrete and well-defined periods of the cell cycle. Immunocytochemical detection of cyclins in relation to cell cycle position (DNA content) by multiparameter flow cytometry has provided a new approach to cell cycle studies. This approach, like no other method, can be used to detect the unscheduled expression of cyclins, namely, the presentation of G1 cyclins by cells in G2/M and of G2/M cyclins by G1 cells, without the need for cell synchronization. Such unscheduled expression of cyclins B1 and A was seen when cell cycle progression was halted, e.g., after synchronization at the G1/S boundary by inhibitors of DNA replication. The unscheduled expression of cyclins B1 or E, but not of A, was also observed in some tumor cell lines even when their growth was unperturbed. Likewise, whereas the expression of cyclins D1 or D3 in nontumor cells was restricted to an early section of G1, the presentation of these proteins in many tumor cell lines also was seen during S and G2/M. This suggests that the partner kinase CDK4 (which upon activation by D-type cyclins phosphorylates pRB committing the cell to enter S) is perpetually active throughout the cell cycle in these tumor lines. Expression of cyclin D also may serve to discriminate G0 vs. G1 cells and, as an activation marker, to identify the mitogenically stimulated cells entering the cell cycle. Differences in cyclin expression make it possible to discriminate between cells having the same DNA content but residing at different phases such as in G2 vs. M or G2/M of a lower DNA ploidy vs. G1 cells of a higher ploidy. The expression of cyclins D, E, A and B1 provides new cell cycle landmarks that can be used to subdivide the cell cycle into several distinct subcompartments. The point of cell cycle arrest by many antitumor agents can be estimated with better accuracy in relation to these compartments compared to the traditional subdivision into four cell cycle phases. The latter applications, however, pertain only to normal cells or to tumor cells whose phenotype is characterized by scheduled expression of cyclins. As sensitive and specific indicators of the cell's proliferative potential, the cyclins, in particular D-type cyclins, are expected to be key prognostic markers in neoplasia.
Z Darzynkiewicz; J Gong; G Juan; B Ardelt; F Traganos
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.; Review    
Journal Detail:
Title:  Cytometry     Volume:  25     ISSN:  0196-4763     ISO Abbreviation:  Cytometry     Publication Date:  1996 Sep 
Date Detail:
Created Date:  1997-02-18     Completed Date:  1997-02-18     Revised Date:  2012-06-25    
Medline Journal Info:
Nlm Unique ID:  8102328     Medline TA:  Cytometry     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1-13     Citation Subset:  IM    
Cancer Research Institute, New York Medical College, Valhalla, USA.
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MeSH Terms
Antineoplastic Agents / pharmacology
Cell Cycle* / drug effects
Cyclin-Dependent Kinase 4
Cyclin-Dependent Kinases / physiology
Cyclins / analysis*,  classification,  physiology
DNA, Neoplasm / analysis
Flow Cytometry*
Gene Expression Regulation
Neoplasm Proteins / analysis,  physiology
Proto-Oncogene Proteins*
Sensitivity and Specificity
Tumor Cells, Cultured
Tumor Markers, Biological / analysis
Grant Support
Reg. No./Substance:
0/Antineoplastic Agents; 0/Cyclins; 0/DNA, Neoplasm; 0/Neoplasm Proteins; 0/Proto-Oncogene Proteins; 0/Tumor Markers, Biological; EC protein, human; EC Kinase 4; EC Kinases

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