Retinoid receptors in human breast carcinoma: possible modulators of in situ estrogen metabolism

Retinoid receptors (retinoic acid (RARs) and retinoid X (RXRs) receptors) w ere immunolocalized in 32 human invasive ductal breast carcinomas. These fi ndings were correlated with clinicopathological parameters to study their b iological significance in breast carcinoma. Retinoid receptor immunoreactiv ity, except for RXR gamma, was detected in the nuclei of carcinoma cells. P ercentage of positive cases were RAR alpha 81%, RAR beta; 6%, RAR gamma; 28 %, RXR alpha; 81%, and RXR beta; 59%. A significant correlation was detecte d between RAR alpha labeling index (LI), and RXR alpha LI (r = 0.667, p < 0 .001). Results from immunoblotting performed in three cases were consistent with those of immunohistochemistry. There was a significant correlation be tween RAR alpha LI and 17 beta -hydroxysteroid dehydrogenase (17 beta -HSD) type 1 immunoreactivity (p < 0.05). A significant correlation was also det ected between RAR alpha (r = 0.413, p = 0.019) or RXR alpha (r = 0.429, p = 0.014) LI, and estrogen receptor (ER) LI. In T-47D breast cancer cells, wh ich express RAR alpha, RXR alpha and ER, 17 beta -HSD reductive activity in creased 1.76-fold (p < 0.001), five days following treatment with 10 nM ret inoic acid. These data suggest that retinoid receptors modulate various eff ects of retinoids, including estrogen metabolism in human breast carcinomas .