Co-regulated gene expression by oestrogen receptor α and liver receptor homolog-1 is a feature of the oestrogen response in breast cancer cells.

Oestrogen receptor α (ERα) is a nuclear receptor that is the driving transcription factor expressed in the majority of breast cancers. Recent studies have demonstrated that the liver receptor homolog-1 (LRH-1), another nuclear receptor, regulates breast cancer cell proliferation and promotes motility and invasion. To determine the mechanisms of LRH-1 action in breast cancer, we performed gene expression microarray analysis following RNA interference for LRH-1. Interestingly, gene ontology (GO) category enrichment analysis of LRH-1-regulated genes identified oestrogen-responsive genes as the most highly enriched GO categories. Remarkably, chromatin immunoprecipitation coupled to massively parallel sequencing (ChIP-seq) to identify genomic targets of LRH-1 showed LRH-1 binding at many ERα binding sites. Analysis of select binding sites confirmed regulation of ERα-regulated genes by LRH-1 through binding to oestrogen response elements, as exemplified by the TFF1/pS2 gene. Finally, LRH-1 overexpression stimulated ERα recruitment, while LRH-1 knockdown reduced ERα recruitment to ERα binding sites. Taken together, our findings establish a key role for LRH-1 in the regulation of ERα target genes in breast cancer cells and identify a mechanism in which co-operative binding of LRH-1 and ERα at oestrogen response elements controls the expression of oestrogen-responsive genes.

Ca 2+ -dependent autophagy is enhanced by the pharmacological agent PK11195.

The 1-(2-Chlorophenyl-N-methylpropyl)-3-isoquinolinecarboxamide, PK11195, is a proven enhancer of apoptotic cell death in a variety of cellular models. Recently, we have shown that by targeting the oncogene Bcl-2, PK11195 increases the [Ca ( 2+) ] in the Endoplasmic Reticulum ([Ca ( 2+) ]er) as well as IP3 induced mitochondrial ([Ca ( 2+) ]m) and cytosolic ([Ca ( 2+) ]c) Ca ( 2+) transients in HeLa cervix carcinoma cells. Here, in the same cells, we have investigated PK11195 contribution to models of pharmacologically induced macroautophagy. To do so, we have monitored the pattern of LC3 (the mammalian orthologue of yeast Atg8) distribution and post transcriptional modifications after challenging with Ca ( 2+) -dependent (ATP, Vitamin D3) and independent (Rapamycin and H 2O 2) stimuli for autophagy execution. We found that PK11195 plays a pro-autophagy role if associated with ATP and Vitamin D3 to be ineffective if co-incubated with Rapamycin and H 2O 2. Notably, Bcl-2 deletion abolished PK11195 effects thus suggesting a selective way of action against the oncogene. By these means, PK11195 is proposed as facilitator of Ca ( 2+) mediated autophagy and tool to ascertain the Bcl-2 contribution to the onset and unfolding of this essential catabolic process for cellular homeostasis.