Field cancerization in the colon:a role for aberrant DNA methylation?

Colorectal cancer is the third most common cancer worldwide and arises secondary to the progressive accumulation of genetic and epigenetic alterations in normal colon cells,which results in a polyp-to-cancer progression sequence.It is known that individuals with a personal history of colon adenomas or cancer are at increased risk for metachronous colon neoplasms.One explanation for this increased risk could be field cancerization,which is a phenomenon in which the histologically normal tissue in an organ is primed to undergo transformation.Epigenetic alterations appear to be promising markers for field cancerization.In this review,we discuss field cancerization in the colon and the data supporting the use of methylated DNA as a biomarker for this phenomenon.

食管腺癌的化学预防

食管腺癌(EAC)是癌症相关死亡的一个主要原因,尤其是在西方人群中,而在亚洲人群中EAC病例也急剧增长。几乎所有的EAC都是由Barrett食管(BE)这一癌前病变进展而来,BE是EAC最重要的危险因素。然而,BE进展为EAC的比例是非常低的,并且BE患者通常是无症状的。因此,任何EAC预防策略都必须是低危害的,这样才能具有临床价值。由于目前的EAC筛查方法和BE监测方法都存在技术上的风险,而且医疗负担沉重,因此,药物及饮食等化学预防就显得十分必要。目前已有多种可能的化学预防方案被尝试应用。研究最多的是质子泵抑制剂(PPI),其对于BE患者有一定的EAC化学预防效果。最近的一项随机试验显示,高剂量PPI比低剂量PPI更加有效。一些质量尚可的观察性及随机对照试验也证实了阿斯匹林及其他非甾体抗炎药的预防效果,但其对人体的较大危害使其无法在临床常规应用。其他方案(如他汀类药物、二甲双胍、雌激素)并没有获得足够的证据支持其用于EAC化学预防。尽管在EAC化学预防方面已取得了较大的进展,但仍然需要探索更加安全有效的化学预防方案。