Characterization of androgen receptor and nuclear receptor co-regulator expression in human breast cancer cell lines exhibiting differential regulation of kallikreins 2 and 3.

Abstract

Accumulating evidence indicates that androgens and the androgen receptor modulate the development and progression of breast adenocarcinoma; however, the precise role and actions remain poorly defined. We examined previously the steroid hormone regulation of 2 known androgen-regulated kallikreins, KLK3 (encoding PSA) and KLK2 (encoding human kallikrein 2 or hK2) in BT-474, T-47D, ZR75-1, MCF-7, MFM-223 and BT-20 human breast cancer cells and found that they were differentially regulated, with the cells showing variable responses to androgen. To determine if this variable response was reflected by differences in androgen receptor, we characterized the expression of androgen receptor in these cells by Western blot analysis and saturation binding analysis. In addition, we sequenced androgen receptor cDNA from each of these cell lines to check whether any androgen receptor mutations were present. The expression of 11 nuclear receptor co-regulatory factors (SRC-1, AIB1, ARA24, ARA54, ARA55, ARA70, ARA160, FHL2, PDEF, NCoR1, SMRT) was compared in these cell lines by semi-quantitative RT-PCR to determine if the pattern of receptor co-activators or -repressors expressed in these cells might explain the differential regulation of KLK2 and KLK3. The levels of androgen receptor varied among the cell lines, but did not correlate with hK2 and PSA secretion determined previously. No mutations within the coding regions of the receptor were detected. With the exception of receptor expressed by MCF-7 cells, the polymorphic CAG repeat length was in the normal range. Every breast cancer cell line exhibited a distinct expression pattern of the nuclear receptor co-regulators examined raising the possibility that the relative levels of these co-activators/-repressors might differentially modulate androgen receptor transcriptional activity within the promoter/enhancer region of KLK2 and KLK3 of these cells.