Retinoic acid receptors a, b and g, and cellular retinol binding protein-I expression in breast fibrocystic disease and cancer

Retinoids seem to act as agents of chemoprevention and differentiation in breast diseases. Their action is mediated by nuclear receptors, retinoic acid receptors (RARa, RARb, RARg) and retinoid X receptors (RXRa, RXRb, RXRg) and modulated by cellular retinol binding proteins (CRBP). There are few published data on CRBP expression. In this study, we evaluated the expression of RARa, b and g and CRBP type I (CRBP-I) gene expression in fibrocystic disease (FD) and in breast cancer (BC), studying 14 FD and 20 BC surgical samples by reverse transcription (RT)-PCR. We also evaluated mRNA concentrations in cancer samples by a semiquantitative PCR method, co-amplifying RARa, RARb and CRBP-I genes with an unrelated gene, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), as internal control. All benign and malignant breast tissues expressed RARa, b and g, and CRBP-I mRNAs. A greater concentration of RARb mRNA was detected in cancer tissues with lower oestrogen and progesterone receptor concentrations, whereas RARa was detected in variable concentrations that were not related to those of steroid receptors. The CRBP-I concentration was similar in all samples studied. We demonstrated that all three RARs and CRBP-I transcripts are expressed in FD, and that RARb, RARg and CRBP-I mRNAs also are present in BC tissues. This indicates that both malignant and benign breast tissues may be target for retinoids, justifying the use of natural and synthetic vitamin A derivatives in the chemoprevention of breast disease. European Journal of Endocrinology 137 410–414