Fasted glucose levels of SirT1-null mice were higher than those of normal littermates but insulin concentrations were not different

April 25, 2017

n also contributes to solid tumor angiogenesis, metastasis, and resistance to chemotherapy and radiotherapy. While this model has been validated in a growing list of haematopoietic and solid tumors, the molecular signaling pathways orchestrating the biology of cancer stem cells remain to be elucidated. The c-Myc oncoprotein has been extensively studied for its instrumental role in proliferation and growth of normal and neoplastic cells. Deregulated c-Myc is found in diverse human tumors and is often associated with advanced malignancy and poor prognosis. As c-Myc has been recently DCC 2036 web recognized as an important regulator of stem cell biology, it may serve as a link connecting malignancy and ��stemness”. In either normal or transformed cells, c-Myc alone activates an embryonic stem cell-like transcriptional module, which strongly correlates with tumor metastasis and mortality. Ectopic c-Myc expression in transformed human keratinocytes dramatically increases the cancer stem cell fraction and enhances tumorigenicity. Introduction of c-Myc with other transcription factors generates induced pluripotent stem cells from differentiated cells. Excluding c-Myc from this combination without eliminating endogenous c-Myc expression, drastically reduces the efficiency of iPS cell production. While all of these data suggest a role for c-Myc in maintaining stem cells, other Myc Regulates Cancer Stem Cell functions of c-Myc in regulating stem cell biology have also been described. Conditional knockout of c-Myc in mouse bone 20171952 marrow does not prevent proliferation or self-renewal of haematopoietic stem cells. It rather results in accumulation of haematopoietic stem cells in bone marrow, suggesting that c-Myc specifically controls the interaction between haematopoietic stem cells and their niches. Additionally, over-expression of c-Myc-estrogen receptor fusion protein in human epidermal stem cells drives differentiation rather than proliferation. Because of the recognized functions of c-Myc in both normal stem cell biology and neural malignancy, we investigated the role of c-Myc in human glioma cancer stem cells. Gliomas are the most common primary intrinsic tumor type of the 10980276 central nervous system. High grade gliomas are among the most lethal human malignancies. In glioma, c-Myc expression correlates with the grade of malignancy. Expression of c-Myc driven by the glial fibrillary acidic protein -promoter in developing mouse astroglia induces tumors that resemble human glioblastoma multiforme. In this mouse model, the tumor mass contains fast dividing subpopulation that express c-Myc and relatively quiescent tumor cells that lack c-Myc expression. We have now determined that the glioma cancer stem cells expressed higher levels of c-Myc relative to matched non-stem tumor cells and the activity of c-Myc is required for proliferation, growth, and survival of glioma cancer stem cells. Loss of c-Myc abolished xenograft formation by glioma cancer stem cells, underscoring a key role of c-Myc in glioma cancer stem cell maintenance. Results Glioma cancer stem cells express high levels of c-Myc To investigate the biological functions of c-Myc in regulation of glioma cancer stem cells, we first determined expression of c-Myc in these cells. Short term cultures enriched or depleted for cancer stem cells were derived from human brain tumor specimens using CD133 selection and characterized as we have previously demonstrated. Quantitative real-time PCR revealed that CD133+ g