The
estrogen receptor alpha (ER alpha) is implicated in the development of
breast cancer. The
immunophilins,
cyclophilin 40 (
CyP40) and
FKBP52, are associated with ER alpha and other
steroid receptors in mutually exclusive heterocomplexes and may differentially modulate receptor activity. Since previous studies have not assessed the levels of these
immunophilins in
breast cancer, we examined 10
breast cancer cell lines for
mRNA and
protein expression of
CyP40 and
FKBP52 and for amplification of the
CyP40 gene. In addition, 26
breast carcinomas, including seven with matched normal breast tissue, were examined for
mRNA expression of both
immunophilins.
CyP40 and
FKBP52 were ubiquitously expressed in
breast cancer cell lines, but there were significant differences in their pattern of expression.
FKBP52 protein levels were generally an order of magnitude greater than those for
CyP40.
FKBP52 mRNA expression correlated strongly with
protein expression and was significantly higher in ER alpha-positive compared with ER alpha-negative cell lines. However,
CyP40 mRNA expression did not correlate with
protein expression, nor did expression of this
immunophilin correlate with ER alpha status. Relatively high expression of
CyP40 in one cell line (BT-20) could be attributed to amplification of the
CyP40 gene. Both
immunophilins were also ubiquitously expressed in
breast carcinomas, and we demonstrate for the first time that both
CyP40 and
FKBP52 mRNA are overexpressed in
breast tumors compared to matched normal breast controls. The overexpression of
CyP40 and
FKBP52, coupled with relative differences in their expression in
tumors, may have important functional implications for ER alpha and other
steroid receptors in
breast cancer.