| [Background and purpose]According to the journal which was the highest impact factor in the world now, CACancer J Clin, the statistics in2014showed that colorectal cancer(CRC), which theincidence was ranked3rdand2ndrespectively in male and female, and the death rateaccounted for8%in the total cancer deaths, and was ranked4threspectively in cancer.CRC in China ranked slightly lower than the Western countries and its incidence wasranked5thand6threspectively in male and female. Colorectal serrated lesions asprecancerous lesions of the CRC, including a variety of subtype. Hyperplastic polyps(hyperplastic polyp, HP), which the most common ratio was above75%, according tohistological mucus different it divided into microvesicular hyperplastic polyp(MVHP),Goblet-cell rich hyperplastic polyp(GCHP), and mucin-poor type, MPHP). Sessileserrated adenoma/polyp(SSA/P) was at15%~25%, based on the special-shapedsegments with/without cell dysplasia. Traditional serrated adenoma(TSA) was about1%.Colorectal serrated pathway depended on a large number of abnormal genes, in whichthe most common was methylation.This study analysed the serrated lesions by MethyLight to detect the CDX2andMGMT gene promoter region CpG Island methylations, and by immunohistochemistryto detect the CDX2and MGMT protein expressions on the one hand, on the other handexplored promoter region CpG Island methylation of CDX2and MGMT gene andage-related factors in serrated lesions. [Method]A total of4810cases of colorectal polyps from The Military General Hospital of BeijingPLA during a five-year period(2007-2013) were retrospectively reviewed. The serratedlesions were classified based on WHO(2010) standards. Taqman probe qPCR(MethyLight) was used to detect CDX2gene and MGMT gene CpG islands methylationstatus in the experimental group of225cases of serrated lesions (including96cases ofhyperplastic polyp,61cases of sessile serrated adenoma/polyp and68cases oftraditional serrated adenoma) and the control group of54cases of tubular adenoma,69cases of colorectal cancer and42cases of normal colorectal mucosa tissues, andverified by sequencing method amplified sequences. While CDX2and MGMT proteinexpression were detected by applying immunohistochemical method with in theexperimental group of116cases of serrated lesions (including52cases of hyperplasticpolyp,41cases of sessile serrated adenoma/polyp,23cases of traditional serratedadenoma) and the control group,20cases of tubular adenoma,24cases of colorectalcancer and24cases of normal colorectal mucosa. Combined with related clinical andendoscopic data, analysed the serrated lesion promoter region CpG Island methylationof CDX2and MGMT gene and age-related factors.[Results]1.The promoter methylation rate of the CDX2gene was significant gradually higher inthe normal colorectal mucosa tissues(22/42,53.38%)、 tubular adenoma(34/54,62.96%)、hyperplastic polyp(70/96,72.97%)、sessile serrated adenoma/polyp(46/61,75.41%)、traditional serrated adenoma(55/68,80.88%) and colorectal cancer(69/69,100%), and the methylation rate reached53.38%. The CDX2gene promoter methylationrates in serrated pathway was slightly higher than traditional APC pathway. CDX2genepromoter methylation rate had statistically significant differences among the controlgroup the normal colorectal mucosa tissues and the experimental group hyperplasticpolyp (P=0.019)、sessile serrated adenoma/polyp (P=0.015) and traditional serratedadenoma (P=0.002), among the control group colorectal cancer and hyperplastic polyp(P=0.000)、sessile serrated adenoma/polyp (P=0.000) and traditional serrated adenoma (P=0.000), and between the control group tubular adenoma and traditional serratedadenoma (P=0.027). The expression rate of the CDX2protein was significant lower inthe normal colorectal mucosa tissues(24/24,100%)、 hyperplastic polyp(51/52,98.07%)、 sessile serrated adenoma/polyp(36/41,87.80%)、 traditional serratedadenoma(19/23,82.61%)、tubular adenoma(15/20,75.00%) and colorectal cancer(17/24,70.83%). CDX2protein positive rate had statistically significant differences betweenthe control group colorectal cancer and the experimental group hyperplastic polyp(P=0.001), between the control group tubular adenoma and the experimental grouphyperplastic polyp (P=0.005), and between the experimental group hyperplastic polypand traditional serrated adenoma (P=0.038). There was a positive correlation of CDX2gene promoter methylation rate and CDX2protein in the experimental grouphyperplastic polyp(P=0.652, γ=-0.064(a very weak correlation))、 sessile serratedadenoma/polyp (P=0.238, γ=-0.182(a very weak correlation))and traditional serratedadenoma(P=0.519, γ=-0.142(a very weak correlation)), while there was a negativecorrelation in them. Frequency methylation of CDX2gene promoter and different agesegments had a positive correlation in the experimental group hyperplasticpolyp(P=0.002, γ=0.312(a weak correlation))、sessile serrated adenoma/polyp (P=0.000,γ=0.473(a moderate correlation))and traditional serrated adenoma(P=0.001, γ=0.392(aweak correlation)), the control group tubular adenoma(P=0.001, γ=0.440(a moderatecorrelation)).2.The promoter methylation rate of the MGMT gene was significant higher in thenormal colorectal mucosa tissues(0/42,0)、hyperplastic polyp(25/96,26.04%)、tubularadenoma(25/54,46.30%)、sessile serrated adenoma/polyp(37/61,60.66%)、traditionalserrated adenoma (52/68,76.47%)and, but the promoter methylation rate of the MGMTgene was slightly lower in colorectal cancer(47/69,68.12%). MGMT gene promotermethylation rate had statistically significant differences among the control group thenormal colorectal mucosa tissues and the experimental group sessile serratedadenoma/polyp (P=0.000) and traditional serrated adenoma (P=0.000), between thecontrol group colorectal cancer and hyperplastic polyp (P=0.000), between the controlgroup tubular adenoma and traditional serrated adenoma (P=0.012) and traditionalserrated adenoma (P=0.001). The expression rate of the MGMT protein was significant lower in the normal colorectal mucosa tissues(24/24,100%)、hyperplastic polyp(51/52,98.07%)、tubular adenoma(16/20,80.00%)、sessile serrated adenoma/polyp(32/41,78.05%) and traditional serrated adenoma(16/23,69.57%) colorectal cancer(17/24,70.83%), wihle slightly higher in colorectal cancer((17/24,70.83%). MGMT proteinpositive rate had significant differences among the control group the normal colorectalmucosa tissues and the experimental group hyperplastic polyp(P=0.001), sessile serratedadenoma/polyp (P=0.000) and traditional serrated adenoma (P=0.000), between thecontrol group colorectal cancer and the experimental group hyperplastic polyp(P=0.001), between the control group tubular adenoma and the experimental grouphyperplastic polyp (P=0.029), among the experimental group hyperplastic polyp andtraditional serrated adenoma (P=0.006), hyperplastic polyp and sessile serratedadenoma/polyp (P=0.001). MGMT gene promoter methylation rate and MGMT proteinhad negative correlation among the experimental group hyperplastic polyp(P=0.117,γ=-0.220(a weak correlation))、sessile serrated adenoma/polyp (P=0.020, γ=-0.361(aweak correlation))and traditional serrated adenoma(P=0.037, γ=-0.437(a moderatecorrelation)). Frequency methylation of MGMT gene promoter and different agesegments had a positive correlation among the experimental group hyperplasticpolyp(P=0.931, γ=0.009(a very weak correlation))、sessile serrated adenoma/polyp(P=0.503, γ=0.087(a very weak correlation))and traditional serrated adenoma(P=0.263,γ=0.138(a very weak correlation)), the control group tubular adenoma(P=0.763,γ=0.042(a very weak correlation)).[Conclusion]1Methylation of CDX2gene promoter upstream areas are high as well as expression ofCDX2protein, but there are no correlation between them. Very few partial methylationmay induce the protein expression, while most of the methylation may graduallyincrease as aging.2The methylation rate of MGMT gene promoter was gradually increased in HP,SSAand TSA, but the protein positive rate of MGMT was gradually decreased in HP, SSA/Pand TSA. MGMT gene methylation may induce the protein expression in the main reason for the downregulation, and it plays an important role in serrated cancerationpathway of hyperplastic polyps-serrated adenoma-carcinoma... |
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