A number of studies have been shown that retiniodscan inhibit malignant cell growth including certain breastcarcinoma cells. its inhibitory effort is observed only inER-positive but not in ER-negative breast cancer cells.We examined retinoic acid receptors (RARs) andretinoids X receptors(RXRs) levels in 6 breast carcinomacell lines and 18 breast cancer biopsy specimens. Wefound that RAR-α mRNA level was significantly higher inER Positive cell lines and samples. RAR-γ mRNA wasexpressed at relatively high levels in majority of tumorsamples independent of the ER-status while RAR-βmRNA was expressed at low levels. We also found highRXR-α mRNA levels in all of the tumor samplesexamined while RXR-γ mRNA could not be detected.Our study suggests a possibility that retinoids inhibittumor cell growth through RAR-α and RAR-α levels mayserve as a potential marker to determine responsivenessof patients to retinoids therapy.
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