Abstract 929: Repression of CD44 is a key molecular action of a novel Gemini vitamin D BXL0124 to inhibit breast cancer cell invasion induced by HGF/Met signaling

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL CD44, a transmembrane glycoprotein, is highly expressed in breast tumors, and the overexpression of CD44 has been associated with poor clinical outcome. CD44 has been known to play a key role in invasive growth of cancer by interacting with extracellular matrix, matrix metalloproteinases (MMPs) and other membrane receptors. In addition, CD44 has been shown to be required for the activation of hepatocyte growth factor (HGF)/Met signaling pathway which is associated with invasive phenotype of human breast cancer. Our previous study demonstrated that a novel Gemini vitamin D BXL0124 repressed the expression of CD44 in MCF10DCIS.com human breast cancer cells and inhibited MCF10DCIS xenograft tumor growth in vivo. In the present study, we investigated the effect of CD44 repression by BXL0124 on HGF/Met mediated invasion in MCF10DCIS cells. The effects of HGF and BXL0124 on the invasive phenotype of MCF10DCIS cells were investigated with invasion assays. To identify key molecules in HGF-induced cancer cell invasion, invasive markers and downstream of HGF/Met signaling pathway were evaluated. The treatment of HGF increased CD44 protein expression and invasive growth of MCF10DCIS cells, which was inhibited by BXL0124 treatment. Stat3 DNA-binding and nuclear translocalization experiments demonstrated that the activation of Stat3, one of the key downstream molecules of HGF/Met signaling pathway, was also significantly decreased by BXL0124 treatment. To further study a specific role of CD44 on breast cancer cell invasion, the effects of CD44 repression were investigated by using MCF10DCIS CD44-knockdown cells in vitro and in vivo. The induction of cancer cell invasion by HGF was blocked when CD44 was knockdown in MCF10DCIS cells. In addition, invasion markers, MMP-9 and uPA, were significantly down-regulated in MCF10DCIS CD44 knockdown cells. For the in vivo study, MCF10DCIS control or CD44-knockdown cells were injected into mammary fat pads in immunodeficient mice. Five weeks later, mammary tumors were collected for evaluating the expression level of invasion markers. The xenograft tumor volume and weight with MCF10DCIS CD44-knockdown cells were significantly smaller by 41% (p<0.01) and 36% (p<0.05), respectively, than those from MCF10DCIS control tumors (n=5). The MCF10DCIS CD44-knockdown tumors also showed markedly decreased protein expression levels of pStat3 and MMP-9. The mRNA expression levels of MMP-9 and uPA were significantly down-regulated in the MCF10DCIS CD44-knockdown tumors. The present study demonstrated the critical role of CD44 in HGF-induced breast cancer cell invasion, suggesting that the repression of CD44 might be a key molecular action of BXL0124 to inhibit breast cancer invasion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 929. doi:1538-7445.AM2012-929