Induction of 72-kD Heat Shock Protein and Cytoskeleton Damage by Cytotoxic Prostaglandin Δ12-PGJ2 in Transformed Human Epidermal Cells in Culture

Cyclopentenone prostaglandins (PG) such as Δ12-PGJ2 and PGA are potent inhibitors of growth in a variety of cultured cells, including human epidermal cells. To clarify the mechanism of PG cytotoxicity in human epidermal cells, we examined the effects of Δ12-PGJ2 on the induction of a heat shock protein (HSP), and on the organization of cytoskeletons in the HSC-I — transformed human epidermal cell line. Immunoblot analysis using a monoclonal antibody specific for the 72-kD heat shock protein (HSP72) revealed that a 12-h incubation with 5 μg/ml of Δ12-PGJ2 induced HSP72 formation in HSC-I cells. HSP72 was also induced by heat shock treatment at 43°C for 90min. The quantity of HSP72 produced was markedly decreased by co-treatment with 1 μg/ml of cycloheximide in Δ12-PGJ2 – treated cells, and similarly reduced in HSC-I cells following heat treatment. Immunofluorescence using a monoclonal antibody to HSP72 demonstrated that HSP72 was localized mainly in the cytoplasm of HSC-I cells. Following treatment with 5 μg/ml of Δ12-PGJ2, however, HSP72 was found in the nucleolus as well as in the cytoplasm. The accumulation of HSP in the nucleolus was similarly prominent in HSC-I cells after treatment at 43°C for 90mm. Addition of Δ12-PGJ2 to confluent HSC-1 cells resulted in the disappearance of actin filaments and the disarrangement of keratin filaments, as visualized with fluorescent-labeled phallacidine or immunofluorescence. These results suggest that the cytotoxicity of cyclopentenone PG is related to the induction of HSP72, and to cytoskeleton damage in transformed human epidermal cells in culture