Aging-like Spontaneous Epigenetic Silencing Facilitates Wnt Activation, Stemness, and BrafV600E-Induced Tumorigenesis

Tao Y, Kang B, Petkovich DA, Bhandari YR, In J, Stein-O’Brien G, Kong X, Xie W, Zachos N, Maegawa S, Vaidya H, Brown S, Chiu Yen RW, Shao X, Thakor J, Lu Z, Cai Y, Zhang Y, Mallona I, Peinado MA, Zahnow CA, Ahuja N, Fertig E, Issa JP, Baylin SB, Easwaran H.

Cancer Cell. 2019 Feb 11;35(2):315-328.e6. doi: 10.1016/j.ccell.2019.01.005.

Summary

We addressed the precursor role of aging-like spontaneous promoter DNA hypermethylation in initiating tumorigenesis. Using mouse colon-derived organoids, we show that promoter hypermethylation spontaneously arises in cells mimicking the human aging-like phenotype. The silenced genes activate the Wnt pathway, causing a stem-like state and differentiation defects. These changes render aged organoids profoundly more sensitive than young ones to transformation by BrafV600E, producing the typical human proximal BRAFV600E-driven colon adenocarcinomas characterized by extensive, abnormal gene-promoter CpG-island methylation, or the methylator phenotype (CIMP). Conversely, CRISPR-mediated simultaneous inactivation of a panel of the silenced genes markedly sensitizes to BrafV600E-induced transformation. Our studies tightly link aging-like epigenetic abnormalities to intestinal cell fate changes and predisposition to oncogene-driven colon tumorigenesis.

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