The effect of rexinoid (LGD1069 and LG100268) on the growth of breast cells. Free

A86

Rexinoids are important in controlling apoptosis and are known to suppress both ER-positive and ER-negative mammary tumor development with reduced toxicity compared to RAR-selective retinoids. Rexinoids are also active in animals in tamoxifen-resistant breast cancer and in ATRA-resistant breast cancer cells. Hence, rexinoids seems to be more efficient and promising chemopreventive and therapeutic drugs compare to RAR-selective ligands. Our goal of the study of the present study is to know whether LGD1069 and LG100268 (rexinoids-from Ligand Pharmaceuticals Inc.) suppress the growth of breast cancer cells, and how these drugs act to inhibit breast cancer development. For that purpose, we tested 5 different breast cell lines; 1 human mammary epithelial cell line (HMEC), 2 different ER-positive cell lines (MCF-7 and T47D) and 2 different ER-negative breast cancer cell lines (MDA-MB-231 and MDA-MB-435). By MTS assay, We found that both LGD1069 and LG100268 inhibited significantly normal HMEC cell growth at 10 uM. We also found that LGD1069 strongly suppressed the growth of T47D (ER-positive) by dose-dependent manner. LGD1069 also induced a mild inhibition of MDA-MB-231 (ER-negative) at 10 uM. MCF-7 and MDA-MB-435 did not have growth suppression by LGD1069 at 10 uM. LG100268 did affect little the cell growth in all 4 breast cancer cell lines suggesting its weak activity compare to LGD1069. We will further enlarge our investigation using three-dimensional (3D) epithelial culture systems, ressembling their in vivo architecture to see whether the growth suppressive activity of rexinoids would be differently displayed between monolayer and 3D system. On the other hand, to investigate the mechanism by which LGD1069 suppresses breast tumorigenesis, we have studied the genes modulated by LGD1069 and LG100268. We treated first MDA-MB-231 with LGD1069 and LG100268 at 10 uM for 12 hrs, extracted RNA and then submitted to Affymetrix Microarray. In MDA-MB-231, we identified 333 genes up-regulated and 319 genes down-regulated by LGD1069 with changes in fold induction greater than 2 fold. We also identified 116 genes up-regulated and 431 genes down-regulated by LG100268 with changes in fold induction greater than 2 fold. According to the data, we found several interesting genes induced by LGD1069 and LG100268 in MDA-MB-231 such as several hypothetical proteins, CDC14 cell division cycle 14 homolog A (S. cerevisiae), recombination activating gene 2, tumor protein D52, MDM2, ITGA4, ADh1B, NF2 and cathepsin S (for LGD1069), several hypothetical proteins, zinc finger protein 423, cyclin-dependent kinase inhibitor 1C (p57, Kip2), eukaryotic tranlation initiation factor 5A, transcription factor 4, MDM2, FGF2, GNRH1, and annexin A9 (for LG100268). We will study their functions. We are also performing gene profiling for HMEC and T47D to identify the genes regulated by LGD 1069 and LG100268. This work is supported by U.S. DOD Grant (W81XWH-04-1-0505).