It is possible that, in addition to inducing an expansion of a relatively undifferentiated and rare subpopulation of cells in the mammary gland, OCT4 induces global epigenetic reprogramming in an epithelial target cell type of the breast. It is well docu mented that OCT4 is an essential reprogramming factor and is sufficient to reprogram neural stem cells toward an induced pluripotent selleck chem Trichostatin A state. In epithelial and other tissues, it is generally accepted that stem pro genitor cells reprogram at a higher frequency than more Inhibitors,Modulators,Libraries differentiated somatic cells, and this also suggests that the target cells mediating the OCT4 phenotype are not fully differentiated. However, to study whether OCT4 induces genome wide epigenetic remodeling, global changes in DNA and histone methylation need to be evaluated in OTBCs.

To confirm the epithelial origin of OTBCs, we evalu ated their differentiation potential by placing the OTBCs in differentiation conditions and performing Inhibitors,Modulators,Libraries a detection of specific CKs, which are a hallmark of epithelial cells. In 3D culture conditions, OTBCs formed TDLUs, which were morphologically very similar to those reported for breast stem and cancer stem cells. When OTBCs were placed in 2D cultures, small populations of cells stained positive for myoepithelial markers or luminal CKs or both. These experiments demonstrated that OTBCs had an epithelial origin, and the cell target of OCT4 was possibly a primi tive stem progenitor cell. In self renewal conditions, OTBCs exhibited antigenic signatures characteristic of prospective stem cells of the breast, such as low levels of CD133, high CD49f, and an absence of EpCAM expression.

Given the current understanding of prospec tive signatures in the mammary gland hierarchy, these antigenic signatures are consistent with a putative breast stem early Inhibitors,Modulators,Libraries progenitor Inhibitors,Modulators,Libraries cell identity. The finding that all OTBCs analyzed were EpCAM suggested that OTBCs do not originate from prospective luminal restricted progenitor cells, which are presumably EpCAM. However, it is also possible that OTBCs origi nate from myoepithelial CD10 restricted progenitors. In addition to being enriched in prospective stem cell signatures, OTBCs were enriched in the tumorigenic, cancer stem cell CD44 CD24 signature. Consistently, we found that as few as 50 cells derived from our OTBC lines was sufficient to generate tumors with metastatic colonization abilities in nude mice.

Histopathological analysis of the tumors in nude mice confirmed the epithelial origin of OTBCs. All OTBCs analyzed generated poorly differentiated carcinomas of the breast and Inhibitors,Modulators,Libraries revealed an epithelial morphology with a relatively high nuclear to cytoplasmic ratio and brisk mitotic activity. new product These tumors were negative for ER, PR, and HER2 and were positive for both OCT4 and the mesenchymal marker VIM.