Regulation of Protein Degradation in Neoplastic Cells
Changes in the overall rate of cell protein degradation (PD) were included by Hershko and co-workers in 19711 among the elements of the “pleiotypic response”, which was categorized as “positive” if associated with growth stimulation or “negative” if accompanying growth suppression. Protein turnover modulations were thus regarded as instrumental in effecting growth-phase transitions. In 1977 Warburton and Poole2 analyzed the relationship between cell growth and PD rates in tissue cultures exposed to serum deprivation or other manipulations. Moreover, in 1977 Gunn et al.3 reported that basal PD rates in various transformed cells were lower than in their normal counterparts, hypothesizing that a reduction in intracellular proteolysis could play a role in neoplastic growth. Since then, many methodological advances have been developed to analyze PD in tissues or cells, particularly in tissue cultures. Nevertheless, studies on the relationship between cell protein turnover rates and growth or neoplastic transformation have generally relied on experimental models not adequately defined in terms of growth properties and kinetics, not to mention the rather crude tools often used to elicit growth-phase transitions.
KeywordsAscitic Fluid Protein Turnover Amino Acid Concentration Stationary Tumor Autophagic Vacuole
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