The methylation of cytosine residues that precede adenine/thymine or other cytosine nucleotides instead of guanine in DNA is known as non-CpG methylation. It is a pronounced epigenetic modification with a central role in gene regulation similar to CpG methylation. Due to technological limitations, the locus-specific role of non-CpG methylation was scarcely understood. At present, high-throughput analyses and improved enrichment methods can elucidate the role of genome-wide non-CpG methylation distributions. Although the functional basis of non-CpG methylation in regulating gene expression control is known, its role in cancer development is yet to be ascertained. This review sheds light on the possible mechanism of non-CpG methylation in embryos and developed tissues with a special focus on cancer development and progression. In particular, the maintenance and alteration of non-CpG methylation levels and the crucial factors that determine this level of non-CpG methylation and its functional role in cancer are discussed.

中文翻译：

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非 CpG 甲基化——癌症的关键表观遗传修饰

在腺嘌呤/胸腺嘧啶或其他胞嘧啶核苷酸而不是 DNA 中的鸟嘌呤之前的胞嘧啶残基的甲基化称为非 CpG 甲基化。它是一种显着的表观遗传修饰，在基因调控中起核心作用，类似于 CpG 甲基化。由于技术限制，几乎不了解非 CpG 甲基化的位点特异性作用。目前，高通量分析和改进的富集方法可以阐明全基因组非 CpG 甲基化分布的作用。尽管非 CpG 甲基化在调节基因表达控制中的功能基础是已知的，但其在癌症发展中的作用尚待确定。这篇综述阐明了胚胎和发育组织中非 CpG 甲基化的可能机制，特别关注癌症的发展和进展。特别是，