Expression of coxsackie-adenovirus receptor is related to estrogen sensitivity in breast cancer

This study analyzes the relationship between coxsackie-adenovirus receptor (CAR) expression (transmembrane and soluble isoforms) and hormone sensitivity in 95 breast cancers. Furthermore, prognostic significance of the expression of the various CAR isoforms was investigated. In addition, inducibility of CAR expression by estradiol and tamoxifen was assessed in various breast cancer cell lines. Expression of transmembrane CAR (hCAR) highly correlated with estrogen receptivity, but was independent of the expression of progesterone receptor (PR). Furthermore, hCAR expression was significantly higher in tumors with low-grade malignancy. However, no relationship between hCAR expression and tumor size, lymph node status, or survival was revealed. In the hormone receptor-positive breast cancer cell line T47-D expression of hCAR and its soluble isoforms was increased by treatment with estradiol and tamoxifen. In contrast, no induction of either CAR isoform was achieved in receptor-negative cell lines. Furthermore, enhancement of hCAR expression was significantly greater when cells were treated with the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) than when treated with estradiol or tamoxifen. Moreover, sensitivity to TSA induction of hCAR was considerably greater in receptor-positive than in receptor-negative cell lines. No additive effect on CAR expression was found when TSA was combined with either estradiol or tamoxifen. In conclusion, the so far undescribed association between estrogen receptivity and the expression of hCAR in breast cancer seems to not only reflect a phenotype of low malignancy, but expression of hCAR may also be directly influenced by ER-specific ligands.