論文 - 橋口　明典

Function of 90 kDa heat shock protein in cellular differentiation of human embryonal carcinoma cells

Yamada T, Hashiguchi A, Fukudshim S, Kakita Y, Umezawa A, Maruyama T, Hata J

In Vitro Cellular and Developmental Biology. Animal （SOC IN VITRO BIOLOGY）  36 （ 2 ） 139-146 - 146 2000年02月

研究論文（学術雑誌）, 共著,  ISSN  1071-2690

　概要を見る

Heat shock proteins (HSPs) have been recognized as molecules that maintain cellular homeostasis during changes in the environment. Here we report that HSP90 functions not only in stress responses but also in certain aspects of cellular differentiation. We found that HSP90 showed remarkably high expression in undifferentiated human embryonal carcinoma (EC) cells, which Here subsequently dramatically down-regulated during in vitro cellular differentiation, following retinoic acid (RA) treatment, at the protein level. Surprisingly, heat shock treatment also triggered the clown-regulation of HSP90 within 48 h at the protein level. Furthermore, the heat treatment induced cellular differentiation into neural cells. This down-regulation of HSP90 by heat treatment was shifted to an up-regulation pattern after cellular differentiation in response to RA treatment. In order to clarify the functions of HSP90 in cellular differentiation, we conducted various experiments, including overexpression of HSP90 via gene transfer. We showed that the RA-induced differentiation of EC cells into a neural cell lineage was inhibited by overexpression of the HSP90 alpha or -beta isoform via the gene transfer method. On the other hand, the overexpression of HSP90 beta alone impaired cellular differentiation into trophoectoderm. These results show that down-regulation of HSP90 is a physiologically critical event in the differentiation of human EC cells and that specific HSP90 isoforms may be involved in differentiation into specific cell lineages.

Apoptosis of human embryonal carcinoma cells with in vitro differentiation

Yamada T, Suzuki N, Hiraoka N, Matsuoka K, Fukushima S, Hashiguchi A, Hata J

Cell Struct Funct （JAPAN SOC CELL BIOLOGY）  21 （ 1 ） 53-61 - 61 1996年

研究論文（学術雑誌）, 共著,  ISSN  0386-7196

　概要を見る

An in vitro model of apoptosis and differentiation in human embryonal carcinoma (EC) cells was developed to study the mode of cell death and mechanisms of cell death in early development. Death of these cells was induced by treatment with retinoic acid (RA) under the same conditions as those for induction of differentiation. The manner of this cell death was apoptosis, not necrosis, with the morphological criterion for apoptosis. Serum deprivation likewise caused apoptosis in both undifferentiated and differentiated EC cells. In differentiated EC cells, DNA fragmentation was observed in a smear pattern lacking the ladder pattern typically associated with apoptosis. However, in differentiated EC cells, DNA fragmentation occurred in various sizes.
The expression of a carbohydrate antigen, Le(Y), a reported marker of apoptotic cancer cells, was increased by the treatment with RA. However, two-color analysis by flow cytometry with nick end labelling method revealed that Le(Y) expression was closely correlated with cellular differentiation but not apoptosis after RA treatment in the human EC cell system. Collection of Le(Y) positive cells by the magnetic bead method demonstrated that this expression was not due to apoptosis but rather to differentiation. On the other hand, Le(Y) expression associated with apoptosis was induced by serum deprivation in both undifferentiated and differentiated EC cells. These results show that a subpopulation of undifferentiated EC cells takes the apoptotic pathway by induction of differentiation.
The results also suggest that the population of cells taking an apoptotic pathway differs from a population of cells taking a differentiation pathway. This in vitro system for apoptosis in human EC cells will be useful for studies concerning apoptosis or programmed cell death in human developmental biology.