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In vivo epigenetic reprogramming of primary human colon cancer cells enhances metastases
Grigori Singovski, Carolina Bernal, Monika Kuciak, Irene Siegl-Cachedenier, Arwen Conod, and Ariel Ruiz i Altaba*
Department of Genetic Medicine and Development, University of Geneva Medical School, CH-1211 Geneva, Switzerland *Correspondence to:Ariel Ruiz i Altaba, E-mail: Ariel.RuizAltaba@unige.ch
J Mol Cell Biol, Volume 8, Issue 2, April 2016, 157-173,  https://doi.org/10.1093/jmcb/mjv034
Keyword: metastases, epigenetic reprogramming, NANOG, GLI, cancer stem cells

How metastases develop is not well understood and no genetic mutations have been reported as specific metastatic drivers. Here we have addressed the idea that epigenetic reprogramming by GLI-regulated pluripotent stemness factors promotes metastases. Using primary human colon cancer cells engrafted in mice, we find that transient expression of OCT4, SOX2, KLF4 +/− cMYC establishes an enhanced pro-metastatic state in the primary tumor that is stable through sequential engraftments and is transmitted through clonogenic cancer stem cells. Metastatic reprogramming alters NANOG methylation and stably boosts NANOG and NANOGP8 expression. Metastases and reprogrammed EMT-like phenotypes require endogenous NANOG, but enhanced NANOG is not sufficient to induce these phenotypes. Finally, reprogrammed tumors enhance GLI2, and we show that GLI2high and AXIN2low, which are markers of the metastatic transition of colon cancers, are prognostic of poor disease outcome in patients. We propose that metastases arise through epigenetic reprogramming of cancer stem cells within primary tumors.