By using the micro array analy sis and other methods, i. e. qPCR, specific inhibitors, flow cytometric and western blotting analyses, few key genes with profound consequence in tumorigenesis have been found to be induced by HER2. These genes include EPZ-5676 purchase COX 2, HDAC6 and breast cancer stem cell marker, CD44 CD24. COX 2 over expression has been found in about 40% of cases of invasive breast carcinoma and at a higher fre quency in preinvasive ductal carcinoma in situ. By qPCR analysis, the level of COX 2 transcripts was significantly elevated in R2N1d cells compared with R2d cells. The expression of COX 2 in R2N1d can be significantly decreased by treatment with HER2 inhibitor, AG825, or MAPK/ERK inhibitor, U0126, using flow cytometric or western blotting analysis.

Since COX 2 could promote tumor progression by inducing various effects such as invasion, angiogenesis and suppression of apoptosis as mentioned before, a major function of HER2 in tumorigenesis could be mediated through the up regulation of COX 2. Inhibitors,Modulators,Libraries Since high frequency of R2N1d cells expressed CD44 which was found to mediate invasion, there could be a synergistic effect of CD44 and COX 2 on inducing the ability of invasion of these cells. Unlike the parental cell lines developed Inhibitors,Modulators,Libraries in hormone/ growth factor enriched medium, the R2d and R2N1d cells developed in hormone/growth factor deprived medium contain CD44 CD24 cells. The frequency of these cells was much higher in R2N1d cells than in R2d cells. The results indicate that HER2 may sustain tumor growth and promote distant metastasis by increasing the frequency of CD44 CD24 cancer stem Inhibitors,Modulators,Libraries cells.

It is Inhibitors,Modulators,Libraries noted from our previous study that R2d cells were non tumorigenic. However, after the exposure to estrogen, these cells increased the expression of CD44 CD24 and became tumori genic. A previous study reported that Herceptin treat ment could decrease ALDH positive cells in a HER2 expressing breast carcinoma cell line. The side population of breast carcinoma, MCF 7, cell line was tumorigenic and expressed high level of Notch 1 and beta catenin besides ABCG2, suggesting that side popu lation has some intrinsic properties of stem cells. Recently, HER2 expression was found to increase the frequencies of side population in both luminal and basal subtypes of breast cancers. Inhibitors,Modulators,Libraries These observations and the results of our study using different breast cancer stem www.selleckchem.com/products/PF-2341066.html cell markers provide independent evidence that HER2 has the ability to maintain high frequency of tumor stem cells. The expression of histone deacetylase, HDAC6, was found to be higher in R2N1d cells than R2d cells by microarray study, although both cell lines show high expression by flow cytometric analysis. This gene can be down regulated by treatment with HER2 and PI3K inhibitors.