MicroRNAs and the expression of the progesterone receptor in breast cancer.

Abstract

e11529 Background: The progesterone receptor (PgR) is a prognostic factor in ER positive breast cancers treated by hormonal therapy and loss of PgR expression might be involved in resistance to hormonal treatment. The regulation of PgR has not been extensively studied. MicroRNAs regulate gene expression either at the mRNA or the protein translation level. Our hypothesis is that microRNA's are involved in the regulation of expression of PgR. Methods: RNA was extracted from ER positive, PgR positive and negative breast tumors and from adjacent benign tissue. The expression of PgR and microRNAs was assessed by RT-PCR. Later, a luciferase reporter assay was performed using the 3' UTR of the PgR gene (WT construct) and a site directed mutated construct in the microRNA binding sites. MicroRNAs were co-transfected with these constructs into MCF-7 cells and the levels luciferase activity was analyzed. Results: The PgR gene contains potential conserved binding sites for MicroRNAs 23a, 181a, 135a and 26b. Of these,...