Abstract 4551: Retinoic acid in the reversion of the neoplastic transformation

Abstract

Abstract Retinoids, usually formed from dietary vitamin A, play a key role during embryonic development, cellular proliferation and differentiation, and are potent inhibitors of cell growth. Retinoids have been recognized as promising anticancer compounds. The effects of retinoids are mediated by retinoic acid receptors (RARβ, RARα, RARγ) and the retinoid X receptors (RXR) that binds the DNA as heterodimers. The objective of this project is to study the potential of retinoic acid to revert the neoplastic process using an in vitro model of breast cancer progression developed in our laboratory. The MCF-10F progression model consists of four derived cell lines: (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 cell line and; (d) the tumor cell lines, caMCFs, which shown all characteristics of a fully malignant breast cancer cell types. The bsMCF cells induced tumors when they were injected in the mammary fat pad of SCID mice; these tumors were poorly differentiated adenocarcinomas that were estrogen receptor (ER), progesterone receptor (PR) and ERBB2 negatives [1]. Using this model, DNA-methylation studies were performed and we have found that RARβ (retinoic acid receptor β) was unmethylated in MCF-10F and trMCF cells becoming hypermethylated at the invasive (bsMCF) and tumorigenic (caMCF) stages. We studied the effect of retinoic acid at the different stages of the in vitro model of breast cancer progression using 3D-cultures (collagen matrix). Cultivation of normal breast epithelial cells within collagen enables the cells to polarize and to spontaneously differentiate tubular structures. In collagen, the MCF-10F cells form tubules resembling the normal mammary gland. The transformed cells trMCF form tubules and spherical masses; spherical masses are an indication of cell transformation. One solid mass was isolated and the cells expanded, giving origin to trMCF clone 11, which only form solid masses in collagen. The trMCF clone 11 cells were treated with different concentrations of retinoic acid during 15 days and, after the treatments the cells were plated in collagen. The trMCF clone 11 treated with 10-6M and 10-7M retinoic acid shown a reduction of solid masses and increased of tubules in collagen. Although bsMCF and caMCF were treated with 5-aza-dC to reactivate the expression of RARβ in combination with retinoic acid, a change in the phenotype of these cells in collagen was not observed. Our results indicated that retinoic acid was able to re-differentiate transformed cells at early stages of the neoplastic process. (This work was supported by The Pennsylvania Breast Cancer Coalition). REFERENCES. [1] S.V. Fernandez et al. DNA methylation changes in a human cell model of breast cancer progression, Mutat Res 688 (2010) 28-35. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4551. doi:10.1158/1538-7445.AM2011-4551