Heat shock induces differentiation of human embryonal carcinoma cells into trophectoderm lineages

NCR-G3 cells were established from a testicular embryonal carcinoma and are highly multipotential, differentiating into trophectoderm cells upon exposure to retinoic acid. Differentiated NCR-G3 cells begin to produce human chorionic gonadotropin (hCG), a trophectoderm-specific hormone. We have previously isolated the up-regulated genes at the early stage of differentiation. One of them was found to be a heat shock protein gene. The heat shock protein gene (HSP90) is induced at the early stage of differentiation and decreases to the basal level or under the basal level at the later stage. We speculate that heat shock per se induces the differentiation of human EC cells. With exposure to heat, NCR-G3 cells began to express a series of differentiation markers such as cytokeratin and hCG. Heat, which is classically known to induce heat shock proteins, is able to differentiate an embryonal cell line into trophectoderm lineages, implying a new recognized function of a heat-like event in early differentiation.