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Application of the principles of enzyme kinetics to clonal growth rate assays: An approach for delineating interactions among growth promoting agents
Author(s) -
Lechner John F.,
Kaighn M. Edward
Publication year - 1979
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041000314
Subject(s) - epidermal growth factor , cell culture , kinetics , cell growth , biology , cell division , enzyme , growth inhibition , fetal bovine serum , growth rate , growth factor , microbiology and biotechnology , cell , biochemistry , chemistry , endocrinology , genetics , receptor , mathematics , physics , geometry , quantum mechanics
The interaction of mitogenic factors on a single cell type and the comparative activity of a given factor in diverse cell types have been studied byapplying the principles of Michaelis‐Menten kinetics to clonal growth data. Such comparisons are facilitated by derivation of two parameters; K m mitogen , the mitogen concentration that gives half‐maximal clonal growth and a theoretical maximal growth rate, R MAX T . Both parameters are analogous to the K m and V MAX as applied to enzymatic reactions. Use of these parameters permits meaningful comparisons between cells with different growth rates. Using kinetic analysis of dose‐response data, we found that normal human epithelial cells require 200 times more fetal bovine serum protein (FBSP) than a malignant line to multiply at their respective half‐maximal rates. Further, the K m FBSPof normal cells was reduced to that of the malignant line by the inclusion of growth factors (EGF or FGF, and hydrocortisone) in the medium. On the other hand, even though greater levels of serum were required when growth factors and hydrocortisone were not present, their inclusion did not alter R MAX T . Interactions between mitogenic factors were shown to be unidirectional. Although EGF reduced the K m FBSP , FBSP did not change the K m EGF . The same type of analysis revealed that hydrocortisone, which potentiated the mitogenic activity of EGF did not change the K m EGF . Kinetic analysis of cell growth should prove useful in studies on the relation between growth and tumor promotion as well as in the evaluation of growth‐inhibiting chemotherapeutic agents.