EGR1 expression: a calcium and ERK1/2 mediated PPARγ-independent event involved in the antiproliferative effect of 15-deoxy-Δ12,14-prostaglandin J2 and thiazolidinediones in breast cancer cells.

Our aim was to get new information about the Peroxisome Proliferator Activated Receptor gamma (PPARγ)-independent pathway involved in the antiproliferative action of PPARγ ligands in breast cancer cells. We investigated the effects of Troglitazone (TGZ), Ciglitazone (CGZ), Rosiglitazone (RGZ) and, 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ(2)) on the hormone-dependent breast cancer cell line MCF7. The early transcription factor EGR1 (Early Growth Response gene 1) mRNA and protein levels peaked after 3h of incubation with 25μM TGZ, CGZ or 15d-PGJ(2) and then gradually decreased.

Thapsigargin induces expression of activating transcription factor 3 in human keratinocytes involving Ca2+ ions and c-Jun N-terminal protein kinase.

Thapsigargin is a specific inhibitor of the sarco/endoplasmic reticulum Ca(2+) ATPase of the endoplasmic reticulum. Here, we show that stimulation of human HaCaT keratinocytes with nanomolar concentrations of thapsigargin triggers expression of activating transcription factor (ATF) 3, a basic-region leucin zipper transcription factor. ATF3 expression was also up-regulated in thapsigargin-stimulated glioma cells, hepatoma cells, retinal pigment epithelial cells, and airway epithelial cells.