Abstract 2109: All trans-retinoic acid (ATRA) induces redifferentiation of early transformed breast epithelial cells

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Retinoids have been used as potential chemotherapeutic or chemopreventive agents because of their differentiative, anti-proliferative, pro-apoptotic, and anti-oxidant properties. The effects of retinoids are mediated by retinoic acid receptors (RARβ;,RARα,RARγ) and the retinoid X receptors (RXR) that bind the DNA as heterodimers. The objective of this project was to study the potential of retinoic acid to revert the neoplastic process using an in vitro model of breast cancer progression. This model was previously developed by treating the human normal breast epithelial MCF-10F cells with high dose of estradiol and consists of four cell lines which show a progressive neoplastic transformation: (a) the spontaneously immortalized cell line MCF-10F, which does not show any characteristic of invasiveness or tumor formation and therefore is considered to be a normal-like breast epithelial cell line; (b) the transformed trMCF cells; (c) the invasive bsMCF cells and; (d) the caMCF tumor cells. The bsMCF cells induced tumors when they were injected in the mammary fat pad of SCID mice. We previously showed that RARβ was unmethylated in MCF-10F and trMCF cells, but became hypermethylated in bsMCF and caMCF. We studied the effect of retinoic acid at the different stages in this model by cultivating the cells in 3D-cultures (collagen matrix). In collagen, the MCF-10F cells form tubules resembling the normal mammary gland. After treatment with estradiol, cells formed tubules and spherical masses which are indicative of transformation. Cells that only formed spherical masses in collagen were isolated (trMCF clone 11) and treated with different concentrations of ATRA (10-5M to 10-8M). We found that trMCF clone 11 cells showed a reduction of solid masses and increased number of tubules in collagen after being treated with 10-6M ATRA. A total of 43% of the structures were tubules in trMCF clone 11 cells treated with 10-6M ATRA. Gene expression studies showed that 207 genes up-regulated in transformed trMCF clone 11 cells were down-regulated after ATRA treatment to levels comparable to those found in the normal breast epithelial cells MCF-10F. Furthermore, 236 genes that were down-regulated in trMCF clone 11 were up-regulated after ATRA treatment to similar levels shown in normal epithelial cells. These 443 genes defined a signature of the ATRA re-programming effect. Our results showed that 10-6M ATRA was able to re-differentiate transformed cells at early stages of the neoplastic process to a normal stage and antagonistically regulate breast cancer associated genes. The invasive and tumorigenic cells did not show any changes in morphology after treatment with ATRA alone or in combination with 5-aza-dC. These results suggest that ATRA could be used as chemopreventive agent to inhibit the progression of premalignant lesions of the breast. This work was supported by The Pennsylvania Breast Cancer Coalition and Friends for an Earlier Breast Cancer Test. Citation Format: Maria F. Arisi, Rebecca A. Starker, Sankar Addya, Yong Huang, Sandra V. Fernandez. All trans-retinoic acid (ATRA) induces redifferentiation of early transformed breast epithelial cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2109. doi:10.1158/1538-7445.AM2014-2109