Leiden University Medical Center, Leiden University Medical Center, Leiden, The Netherlands.
Gut. 2011 Nov;60(11):1544-53. doi: 10.1136/gut.2011.237495. Epub 2011 May 6.
Promoter hypermethylation is an important and potentially reversible mechanism of tumour suppressor gene silencing in cancer. Compounds that demethylate tumour suppressor genes and induce differentiation of cancer cells, but do not have toxic side effects, would represent an exciting option in cancer therapy. Statins are cholesterol-lowering drugs with an excellent safety profile and associated with a reduced incidence of various cancers including colorectal cancer (CRC). The authors have previously shown that statins act by activating tumour suppressive bone morphogenetic protein (BMP) signalling in CRC, increasing expression of BMP2. BMP2 is silenced by hypermethylation in gastric cancer.
To investigate whether BMP2 is methylated in CRC, whether statins can reverse this, and what implications this has for the use of statins in CRC.
Methylation-specific PCR, bisulphite sequencing, immunoblotting, reverse transcription PCR, quantitative PCR, fluorescence-activated cell sorting analysis, an in vitro DNA methyltransferase (DNMT) assay, and cell viability studies were performed on CRC cells. The effect of statins was confirmed in a xenograft mouse model. Results BMP2 is silenced by promoter hypermethylation in cell lines with the hypermethylator phenotype and in primary tumours. Treatment with lovastatin downregulates DNMT activity, leading to BMP2 promoter demethylation and to upregulation of expression of BMP2 as well as other genes methylated in CRC. Statins alter gene expression, indicating a shift from a stem-like state to a more differentiated state, thereby sensitising cells to the effects of 5-fluorouracil. In a xenograft mouse model, simvastatin treatment induces BMP2 expression, leading to differentiation and reduced proliferation of CRC cells.
Statins act as DNMT inhibitors, demethylating the BMP2 promoter, activating BMP signalling, inducing differentiation of CRC cells, and reducing 'stemness'. This study indicates that statins may be able to be used as differentiating agents in combined or adjuvant therapy in CRC with the CpG island methylator phenotype.
启动子甲基化是肿瘤抑癌基因沉默的一种重要的、潜在可逆转的机制。能够去甲基化肿瘤抑癌基因并诱导癌细胞分化，而没有毒性副作用的化合物将是癌症治疗中的一个令人兴奋的选择。他汀类药物是降低胆固醇的药物，具有极好的安全性，与各种癌症（包括结直肠癌）的发病率降低相关。作者先前已经表明，他汀类药物通过激活结直肠癌中肿瘤抑制性骨形态发生蛋白（BMP）信号传导，增加 BMP2 的表达而起作用。BMP2 在胃癌中因甲基化而沉默。
研究 BMP2 是否在结直肠癌中发生甲基化，他汀类药物是否可以逆转这种情况，以及这对结直肠癌中他汀类药物的应用有何影响。
对结直肠癌细胞进行甲基化特异性 PCR、亚硫酸氢盐测序、免疫印迹、逆转录 PCR、定量 PCR、荧光激活细胞分选分析、体外 DNA 甲基转移酶（DNMT）测定和细胞活力研究。在异种移植小鼠模型中验证了他汀类药物的作用。结果：BMP2 在具有高甲基化表型的细胞系和原发性肿瘤中因启动子甲基化而沉默。洛伐他汀治疗下调 DNMT 活性，导致 BMP2 启动子去甲基化，并上调 BMP2 以及结直肠癌中其他甲基化基因的表达。他汀类药物改变基因表达，表明从干细胞样状态向更分化状态转变，从而使细胞对 5-氟尿嘧啶的作用敏感。在异种移植小鼠模型中，辛伐他汀治疗诱导 BMP2 表达，导致结直肠癌细胞分化和增殖减少。
他汀类药物作为 DNMT 抑制剂，可使 BMP2 启动子去甲基化，激活 BMP 信号转导，诱导结直肠癌细胞分化，并降低“干性”。这项研究表明，在具有 CpG 岛甲基化表型的结直肠癌中，他汀类药物可能能够作为联合或辅助治疗中的分化剂使用。
