Taira Aurora, Aavikko Mervi, Katainen Riku, Kaasinen Eevi, Välimäki Niko, Ravantti Janne, Ristimäki Ari, Seppälä Toni T, Renkonen-Sinisalo Laura, Lepistö Anna, Tahkola Kyösti, Mattila Anne, Koskensalo Selja, Mecklin Jukka-Pekka, Böhm Jan, Bramsen Jesper Bertram, Andersen Claus Lindbjerg, Palin Kimmo, Rajamäki Kristiina, Aaltonen Lauri A
Medicum/Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, 00014, Finland.
Applied Tumor Genomics Research Program, Research Programs Unit, University of Helsinki, Helsinki, 00014, Finland.
Oncogene. 2025 Mar 18. doi: 10.1038/s41388-025-03326-y.
Oncogenic codon V600E mutations of the BRAF gene affect 10-15% of colorectal cancers, resulting in activation of the MAPK/ERK signaling pathway and increased cell proliferation and survival. BRAF-mutated colorectal tumors are often microsatellite unstable and characterized by high DNA methylation levels. However, the mechanistic link between BRAF mutations and hypermethylation remains controversial. Understanding this link, particularly in microsatellite stable tumors is of great interest as these often show poor survival. We characterized the metabolomic, epigenetic and transcriptomic patterns of altogether 39 microsatellite stable BRAF-mutated colorectal cancers. Metabolomic analysis of tumor tissue showed low levels of vitamin C and its metabolites in BRAF-mutated tumors. Gene expression analysis indicated dysregulation of vitamin C antioxidant activity in these lesions. As vitamin C is an important cofactor for the activity of TET DNA demethylase enzymes, low vitamin C levels could directly contribute to the high methylation levels in these tumors by decreasing enzymatic TET activity. Vitamin C transporter gene SLC23A1 expression, as well as vitamin C metabolite levels, were inversely correlated with DNA methylation levels. This work proposes a new mechanistic link between BRAF mutations and hypermethylation, inspiring further work on the role of vitamin C in the genesis of BRAF-mutated colorectal cancer.
BRAF基因的致癌密码子V600E突变影响10%-15%的结直肠癌,导致MAPK/ERK信号通路激活,细胞增殖和存活增加。BRAF突变的结直肠肿瘤通常微卫星不稳定,其特征是DNA甲基化水平高。然而,BRAF突变与高甲基化之间的机制联系仍存在争议。了解这种联系,特别是在微卫星稳定的肿瘤中,具有极大的研究价值,因为这些肿瘤往往预后较差。我们对总共39例微卫星稳定的BRAF突变型结直肠癌的代谢组学、表观遗传学和转录组学模式进行了表征。肿瘤组织的代谢组学分析显示,BRAF突变型肿瘤中维生素C及其代谢物水平较低。基因表达分析表明,这些病变中维生素C抗氧化活性失调。由于维生素C是TET DNA脱甲基酶活性的重要辅助因子,低维生素C水平可能通过降低TET酶活性直接导致这些肿瘤中的高甲基化水平。维生素C转运蛋白基因SLC23A1的表达以及维生素C代谢物水平与DNA甲基化水平呈负相关。这项研究提出了BRAF突变与高甲基化之间一种新的机制联系,为进一步研究维生素C在BRAF突变型结直肠癌发生中的作用提供了思路。
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