IGF2 differentially methylated region hypomethylation in relation to pathological and molecular features of serrated lesions.
IGF2 differentially methylated region hypomethylation in relation to pathological and molecular features of serrated lesions.
复制标题
DOI：
10.3748/wjg.v20.i29.10050
复制
发表时间：
2014-08
影响因子：
4.3
通讯作者：
T. Naito;K. Nosho;Miki Ito;H. Igarashi;K. Mitsuhashi;S. Yoshii;Hironori Aoki;M. Nomura;Y. Sukawa-Y.
中科院分区：
文献类型：
--
作者：
T. Naito;K. Nosho;Miki Ito;H. Igarashi;K. Mitsuhashi;S. Yoshii;Hironori Aoki;M. Nomura;Y. Sukawa-Y.
目的探讨胰岛素样生长因子2 （IGF2）差异甲基化区（DMR）0低甲基化与结直肠锯齿状病变的临床病理和分子特征的关系。方法为了准确分析各类型锯齿状病变的组织学类型与分子特征之间的相关性，我们连续收集了1386例福尔马林固定石蜡包埋组织标本，包括所有组织学类型[增生性息肉（HPs, n = 121）、无柄锯齿状腺瘤（SSAs, n = 132）、传统锯齿状腺瘤（TSAs, n = 111）、非锯齿状腺瘤（n = 195）和结直肠癌（crc, n = 827）]。我们在HPs （n = 115）、SSAs （n = 120）、SSAs伴细胞学发育不良（n = 10）、TSAs （n = 91）、TSAs伴高度发育不良（HGD） （n = 15）、非锯齿状腺瘤（n = 80）、非锯齿状腺瘤伴HGD （n = 105）和crc （n = 794）中评估了IGF2 DMR0和长交错核苷酸元件-1 （LINE-1）的甲基化水平。为了准确定量IGF2 DMR0和LINE-1的相对甲基化水平（比例为0%-100%），我们使用亚硫酸氢盐焦磷酸测序法。分析肿瘤标本的微卫星不稳定性、KRAS（密码子12和13）、BRAF （V600E）和PIK3CA（外显子9和20）突变；MLH1和MGMT甲基化；免疫组化检测IGF2的表达。结果351例锯齿状腺瘤和185例非锯齿状腺瘤（伴或不伴HGD）中IGF2 DMR0甲基化水平分布如下：均值61.7，中位数62.5，标准差18.0，范围5.0 ~ 99.0，四分位数间距49.5 ~ 74.4。将IGF2 DMR0甲基化水平分成四分位数（Q1≥74.5,Q2 62.6-74.4, Q3 49.6-62.5, Q4≤49.5）进一步分析。就组织学类型而言，SSAs的IGF2 DMR0甲基化水平（平均±SD， 73.1±12.3）显著高于HPs（61.9±20.5）、TSAs（61.6±19.6）和非锯齿状腺瘤（59.0±15.8）（P < 0.0001）。IGF2 DMR0甲基化水平与IGF2表达水平呈负相关（r = -0.21, P = 0.0051）。与hp、tsa和非锯齿状腺瘤相比，SSAs中IGF2 DMR0低甲基化的检测频率较低（P < 0.0001）。多因素logistic回归分析也显示IGF2 DMR0低甲基化与SSAs呈负相关（P < 0.0001）。HGD组中IGF2 DMR0和LINE-1甲基化水平（分别为50.2±18.7和55.7±5.4）显著低于TSAs组（分别为61.6±19.6和58.8±4.7）（IGF2 DMR0, P = 0.038; LINE-1, P = 0.024）。结论IGF2 DMR0低甲基化可能是SSA通路中一种罕见的表观遗传改变。IGF2 DMR0和LINE-1的低甲基化可能在TSA通路进展中发挥作用。
AIM To investigate insulin-like growth factor 2 (IGF2) differentially methylated region (DMR)0 hypomethylation in relation to clinicopathological and molecular features in colorectal serrated lesions. METHODS To accurately analyze the association between the histological types and molecular features of each type of serrated lesion, we consecutively collected 1386 formalin-fixed paraffin-embedded tissue specimens that comprised all histological types [hyperplastic polyps (HPs, n = 121), sessile serrated adenomas (SSAs, n = 132), traditional serrated adenomas (TSAs, n = 111), non-serrated adenomas (n = 195), and colorectal cancers (CRCs, n = 827)]. We evaluated the methylation levels of IGF2 DMR0 and long interspersed nucleotide element-1 (LINE-1) in HPs (n = 115), SSAs (n = 120), SSAs with cytological dysplasia (n = 10), TSAs (n = 91), TSAs with high-grade dysplasia (HGD) (n = 15), non-serrated adenomas (n = 80), non-serrated adenomas with HGD (n = 105), and CRCs (n = 794). For the accurate quantification of the relative methylation levels (scale 0%-100%) of IGF2 DMR0 and LINE-1, we used bisulfite pyrosequencing method. Tumor specimens were analyzed for microsatellite instability, KRAS (codons 12 and 13), BRAF (V600E), and PIK3CA (exons 9 and 20) mutations; MLH1 and MGMT methylation; and IGF2 expression by immunohistochemistry. RESULTS The distribution of the IGF2 DMR0 methylation level in 351 serrated lesions and 185 non-serrated adenomas (with or without HGD) was as follows: mean 61.7, median 62.5, SD 18.0, range 5.0-99.0, interquartile range 49.5-74.4. The IGF2 DMR0 methylation level was divided into quartiles (Q1 ≥ 74.5, Q2 62.6-74.4, Q3 49.6-62.5, Q4 ≤ 49.5) for further analysis. With regard to the histological type, the IGF2 DMR0 methylation levels of SSAs (mean ± SD, 73.1 ± 12.3) were significantly higher than those of HPs (61.9 ± 20.5), TSAs (61.6 ± 19.6), and non-serrated adenomas (59.0 ± 15.8) (P < 0.0001). The IGF2 DMR0 methylation level was inversely correlated with the IGF2 expression level (r = -0.21, P = 0.0051). IGF2 DMR0 hypomethylation was less frequently detected in SSAs compared with HPs, TSAs, and non-serrated adenomas (P < 0.0001). Multivariate logistic regression analysis also showed that IGF2 DMR0 hypomethylation was inversely associated with SSAs (P < 0.0001). The methylation levels of IGF2 DMR0 and LINE-1 in TSAs with HGD (50.2 ± 18.7 and 55.7 ± 5.4, respectively) were significantly lower than those in TSAs (61.6 ± 19.6 and 58.8 ± 4.7, respectively) (IGF2 DMR0, P = 0.038; LINE-1, P = 0.024). CONCLUSION IGF2 DMR0 hypomethylation may be an infrequent epigenetic alteration in the SSA pathway. Hypomethylation of IGF2 DMR0 and LINE-1 may play a role in TSA pathway progression.