Regulation of estrogen sulfotransferase (SULT1E1) expression by proliferation state in MCF10A human breast epithelial cells: Potential role of microRNAs

Abstract

The MCF10A cell line represents a model of the normal human breast epithelial cell. Estrogen sulfotransferase (SULT1E1), a major estrogen‐inactivating enzyme, is up‐regulated in confluent relative to preconfluent MCF10A cells. The mechanism responsible for SULT1E1 up‐regulation in confluent MCF10A cells was investigated. Transient or stable tranfection of reporter constructs containing up to 7 kb of the SULT1E1 5′‐flanking region failed to recapitulate confluency‐induced SULT1E1 up‐regulation. The half‐life of SULT1E1 mRNA in preconfluent MCF10A cells was estimated to be ~4h based on analysis of SULT1E1 mRNA levels in MCF10A cells that were replated after reaching confluency. Microarray analysis revealed that 85 microRNAs were significantly up‐regulated and 24 microRNAs were down‐regulated in confluent relative to preconfluent MCF10A cells. Computational analysis of the SULT1E1 3′‐untranslated region identified 4 putative candidate binding sites for confluency‐regulated microRNAs. The confluency‐related decrease in two of these microRNAs (miR‐221 and miR‐100*) corresponded with the confluency‐induced increase in SULT1E1 mRNA observed in MCF10A cells. These results support a role for the post‐transcriptional up‐regulation of SULT1E1 mRNA expression in confluent relative to preconfluent MCF10A cells. Supported by NIH grant (ARRA) ES016373 (MRM) and EHS Center grant ES06636.