Obesity promotes PhIP-induced small intestinal carcinogenesis in hCYP1A-db/db mice: involvement of mutations and DNA hypermethylation of Apc.
Obesity promotes PhIP-induced small intestinal carcinogenesis in hCYP1A-db/db mice: involvement of mutations and DNA hypermethylation of Apc.
复制标题
肥胖促进 hCYP1A-db/db 小鼠 PhIP 诱导的小肠癌发生：Apc 突变和 DNA 高甲基化的参与。
DOI：
10.1093/carcin/bgw054
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发表时间：
2016
期刊：
影响因子：
4.7
通讯作者：
Yang,ChungS
中科院分区：
文献类型：
--
作者：
Wang,Hong;Liu,Anna;Kuo,Yingyi;Chi,Eric;Yang,Xu;Zhang,Lanjing;Yang,ChungS
肥胖与癌症风险增加有关。为了研究肥胖对饮食致癌物诱导的胃肠道肿瘤的促进作用，我们使用2-氨基-1-甲基-6-苯基咪唑[4，5-B]吡啶（PhIP）诱导CYP 1A人源化（hCYP 1A）小鼠的肠道肿瘤发生，其中小鼠CYP 1a 1/1a 2被替换为人CYP 1A 1/1A 2。通过与Leprdb/+小鼠交配以建立遗传诱导的肥胖hCYP 1A-Leprdb/db小鼠或通过给hCYP 1A小鼠喂食高脂肪饮食，在hCYP 1A小鼠中引入肥胖。PhIP诱导肥胖hCYP 1A小鼠在28-40周龄时形成小肠肿瘤，但在瘦hCYP 1A小鼠中没有。在瘦或肥胖小鼠的结肠和其他胃肠道器官中未发现肿瘤。免疫组化结果显示，NF-κB p65、pSTAT 3和COX 2在小肠肿瘤组织中呈强阳性表达，细胞核β-catenin（Ctnnb 1）表达水平升高，而在正常小肠组织中无表达。通过对ApcandCtnnb 1基因进行测序，我们发现大多数PhIP诱导的肥胖小鼠小肠肿瘤仅携带Apc的单个杂合突变。通过亚硫酸氢盐测序发现Apc基因转录起始位点的一个CpG簇发生了DNA超甲基化，这很可能是导致野生型Apcallele失活的原因。我们的研究结果表明，PhIP诱导的hCYP 1A-db/db小鼠小肠癌的发生是由肥胖促进的，并涉及DNA超甲基化引起的Apc突变和失活。这一实验结果与近几十年来肥胖与人类小肠癌发病率增加的关联一致。
Obesity is associated with an increased risk of cancer. To study the promotion of dietary carcinogen-induced gastrointestinal cancer by obesity, we employed 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) to induce intestinal tumorigenesis in CYP1A-humanized (hCYP1A) mice, in which mouseCyp1a1/1a2was replaced with humanCYP1A1/1A2. Obesity was introduced in hCYP1A mice by breeding with Leprdb/+mice to establish the genetically induced obese hCYP1A-Leprdb/dbmice or by feeding hCYP1A mice a high-fat diet. PhIP induced the formation of small intestinal tumors at the ages of weeks 28–40 in obese hCYP1A mice, but not in lean hCYP1A mice. No tumors were found in colon and other gastrointestinal organs in the lean or obese mice. Using immunohistochemistry (IHC), we found strong positive staining of NF-κB p65, pSTAT3 and COX2 as well as elevated levels of nuclear β-catenin (Ctnnb1) in small intestinal tumors, but not in normal tissues. By sequencingApcandCtnnb1genes, we found that most PhIP-induced small intestinal tumors in obese mice carried only a single heterozygous mutation inApc. By bisulfite-sequencing of CpG islands ofApc, we found DNA hypermethylation in a CpG cluster located in its transcription initiation site, which most likely caused the inactivation of the wild-typeApcallele. Our findings demonstrate that PhIP-induced small intestinal carcinogenesis in hCYP1A-db/db mice is promoted by obesity and involvesApcmutation and inactivation by DNA hypermethylation. This experimental result is consistent with the association of obesity and the increased incidence of small intestinal cancer in humans in recent decades.