Overexpres sion of DKK1 in a breast cancer cell line resulted in an inhibition of self renewal ability. Thus, downregulation of the NOS target different DKK1 in OTBCs is consistent with gain of self renewal ability and mesenchymal character istics via the upregulation of EMT TFs. In hESCs, OCT4 represses TFs involved in pattern specification, such as homeobox containing proteins. In contrast, homeobox containing TFs were highly enriched in our OTBC upregulated gene signature. The homeobox TF SIX1 was found upregulated in the OTBCs relative to parental lines. Overexpression of SIX1 in the mouse mammary gland promoted an expan sion of stem progenitor cells and subsequent tumor development. In a parallel study, Micalizzi and col leagues reported that overexpression of SIX1 also facilitated breast cancer metastasis by induction of EMT.

Inhibitors,Modulators,Libraries In conclusion, our data support a mechanism by which differential regulation of downstream targets of OCT4 led to activation of oncogenes Inhibitors,Modulators,Libraries and downregula tion of tumor suppressors. Since OTBCs sustained aber rant self renewal, it is possible that these cells gained TIC features by selective amplification of spheroids. A compromised tumor suppressor repertoire could result in subsequent selection of clones possessing tumorigenic ability. The molecular events leading to upregulation Inhibitors,Modulators,Libraries of TF genes and downregulation of multiple tumor sup pressor genes are unknown at present, however, genetic and epigenetic events might be involved. In hESCs, acti vation of TF networks is associated with promoter de methylation and gene reactivation.

Loss of tumor sup pressor functions in OTBCs could also Inhibitors,Modulators,Libraries involve genetic and epigenetic silencing mechanisms. Downstream epi genetic regulators of OCT4, such as DNMT3a b, could be involved in this concerted silencing of tumor sup pressor genes. Alternatively, OCT4 and other self renewal TFs could be associated with large silencing complexes involving HDACs, such as NODE and NuRD, which Inhibitors,Modulators,Libraries have been well described in hESCs. Consistent with the idea of epigenetic modulation trig gered by OCT4, we found that methyltransferase inhibitors and HDACis were able to partially reactivate tumor suppressor genes in OTBCs. In summary, our data describe the generation of novel claudin low cell lines that could be used by breast cancer investigators to analyze genetic and epigenetic determinants of tumor initiation.

Conclusions In this article, we have www.selleckchem.com/products/Nilotinib.html shown that overexpression of OCT4 cDNA into normal primary breast epithelial pre parations generated clonal populations of cells with aberrant self renewal that developed tumor initiation ability. When injected in nude mice, these cells devel oped poorly differentiated, mesenchymal enriched, and triple negative breast carcinomas. OCT4 transduced breast colonies exhibited genome wide signatures that are over represented in the claudin low intrinsic subtype of breast cancer.