This result suggests that COUP TFI select ively triggers a remodeling of the chromatin of both the CXCL12 and CXCR4 promoters toward a more ARQ197 Tivantinib condensed structure or an open structure, which are well correlated to the transcriptional activities ob served for these two genes. COUP TFI overexpression alters CXCL12/CXCR4 estrogenic regulation Our earlier studies have shown that COUP TFI modulates ER transcriptional activity and is able to selectively mod ify the estrogenic regulation of estrogen sensitive genes. Because the expression of CXCL12 and CXCR4 are regulated by estrogenic signals in breast cancer cells, we investigated the impact of COUP TFI on the es trogenic regulation of the CXCL12 and CXCR4 genes by treating the MCF 7 clones with 10?8 M E2, 10?6 M ICI, or both for 48 h.

As expected, treatment of the control MCF 7 cells with E2 for 48 h resulted in the enhanced expression of CXCL12 and CXCR4 in comparison to the untreated and ICI treated cells. The up regulation of CXCL12 expression by E2 was also observed in the COUP cells treated with E2. However, the relative level of CXCL12 expression was per sistently and significantly 30% lower in the COUP cells com pared with the control cells. CXCR4 expression was constitutively enhanced in the COUP clones, and nei ther E2 nor ICI, alone or in combination, had an effect on this increased CXCR4 expression. This result suggests that the constitutive effect of COUP TFI overex pression on CXCR4 mRNA is independent of ER signaling. COUP TFI overexpression modulates the EGFR and MAPK signaling pathways The growth factor control of cell fate is a pivotal step in cancer progression.

indeed, the high expression of epi dermal growth factor receptor in cancers has been associated with metastatic tumors and poor clinical outcomes. Additionally, EGFR signaling was recently linked to CXCR4 signaling. Therefore, we evaluated the effect of COUP TFI on the expression of EGF and EGFR in MCF 7 clones and found that COUP TFI overexpression increased both EGF and EGFR expression by 1. 8 to 2 times, respectively, in com parison to the MCF 7 control cells. Moreover, our earlier studies have shown that COUP TFI was able to interplay with the MAPK pathway, enhancing ERK activity. We confirmed this observation by analyzing ERK protein phosphorylation after the EGF stimulation of COUP cells in comparison to the control cells.

To further investigate whether the up regulation of EGF signaling by COUP TFI could be linked to the changes in CXCL12 and CXCR4 gene expression, Anacetrapib treatments with EGF and select ive inhibitors for EGFR and MEK sig naling were performed. Interestingly, EGF treatment significantly decreased CXCL12 expression in both the control and COUP clones, whereas the inhib ition of EGFR signaling by AG1478 and U0126 led to a slight but significant elevation in CXCL12 expression in both cells.