The brief incubation of human epidermoid carcinoma (KB) cells, and of primary cultures of quail myoblasts and hamster fibroblasts, at an elevated temperature causes the pattern of gene expression to shift from the production of a broad spectrum of different proteins to the enhanced synthesis of a small number of heat-shock proteins. Comparison of the heat-shock polypeptides synthesized by each of these vertebrate cells demonstrates the similarity of some, as well as the uniqueness of other, heat-inducible gene products synthesized by cells from different vertebrates. A major polypeptide, commonly synthesized in response to heat by each of these vertebrate cells, has an apparent molecular weight of 64 000 and an isoelectric point of 5.8. Triton X-100 completely extracts this polypeptide from quail myoblasts and hamster fibroblasts, and partially extracts it from KB cells. This particular response to heat shock, by cells from different vertebrates, suggests that it may involve the expression of a gene(s) with an analogous and potentially crucial cellular function. This specific heat-shock polypeptide, as well as others, is not detectably synthesized in quail cells prior to heat shock or 6–8 h after recovery from heat shock which suggests that in this cell type it may be a product of a normally quiescent gene(s) and that its expression is subject to thermal regulation.
Efficacy of Liposomal Monensin on the Enhancement of the Antitumour Activity of Liposomal Ricin in Human Epidermoid Carcinoma (KB) Cells