EXPRESSION OF THE RETINOIC ACID RECEPTORS (RARs) AND RETINOID X RECEPTOR (RXRs) GENES IN BREAST CANCER

A number of studies have been shown that retiniods can inhibit malignant cell growth including certain breast carcinoma ceils. Its inhibitory effort is observed only in ER-positive but not in ER-negative breast cancer cells. We examined retinoic acid receptors (RARs) and retinoids X receptors (RXRs) levels in 6 breast carcinoma cell lines and 18 breast cancer biopsy specimens. We found that RAR-α mRNA level was significantly higher in ER positive cell lines and samples. RAR-β mRNA was expressed at relatively high levels in majority of tumor samples independent of the ER-status while RAR-β mRNA was expressed at low levels. We also found high RXR-α mRNA levels in all of the tumor samples examined while RXR-γ mRNA could not be detected. Our study suggests a possibility that retinoids inhibit tumor cell growth through RAR-α and RAR-α levels may serve as a potential marker to determine responsiveness of patients to retinoids therapy.