视网膜母细胞瘤组织中DNA甲基转移酶1、DNA甲基转移酶3a、3b的表达

Expression of DNA methyltransferases 1, 3a, and 3b in retinoblastoma

目的观察视网膜母细胞瘤（RB）组织中DNA甲基转移酶（DNMT）1、DNMT3a和DNMT3b的表达。方法62例RB肿瘤组织标本及6例正常视网膜组织标本纳入研究。其中，低分化组织标本17例，高分化组织标本45例；侵袭性肿瘤16例，非侵袭性肿瘤46例。采用免疫组织化学染色方法检测RB肿瘤组织标本中DNMT1、DNMT3a、DNMT3b的表达。以细胞核棕色染色为阳性表达，蓝色为阴性表达。以DNMT1、DNMT3a及DNMT3b阳性细胞分别≥65％、60％及40％为DNMT1、DNMT3a、DNMT3b高表达，≥1％但〈65％、60％及40％为低表达。同时分析DNMT1、DNMT3a、DNMT3b表达和MIB-1标记指数之间的相关性。结果光学显微镜观察发现，正常视网膜组织中DNMT1、DNMT3a和DNMT3b均为阴性表达。肿瘤视网膜组织中均可见DNMT1、DNMT3a和DNMT3b表达，其阳性表达率分别为100％、98％、92％。高低分化组织标本比较，DNMT1、DNMT3a高表达率（χ2=12．57、10．54）及阳性细胞计数（U=179、198）间差异均有统计学意义（P〈O．05）；DNMT3b高表达率（χ2=1．5）和阳性细胞计数（U=307）间差异均无统计学意义（P〉0．05）。侵袭性及非侵袭性肿瘤组织标本比较，DNMTl高表达率χ2=4．72）及阳性细胞计数（U=236）间差异均有统计学意义（P〈0．05）；DNMT3a、DNMT3b高表达率（χ2=3．53、0．84）及阳性细胞计数（U=338、257）间差异均无统计学意义（P〉0．05）。相关性分析结果显示，MIB-1标记指数与RB肿瘤组织中DNMT1、DNMT3a及DNMT3b表达呈正相关（R2=0．554、0．376、0．219，P〈O．05）。结论RB肿瘤视网膜组织中DNMT1、DNMT3a和DNMT3b均呈高表达。

Objective To observe the expressions of DNA methyltransferases （DNMTs） 1, 3a and 3b in retinoblastoma （RB）. Methods Sixty-two RB samples and six normal retinas were studied, including 17 poorly differentiated and 45 well differentiated samples;16 invasive and 46 non-invasive samples. The expressions of DNMT1, 3a, and 3b, and Ki-67 were detected using immunohistochemical analysis. Brown staining of nuclei was considered to represent the positive stain for DNMT1, 3a and 3b, and ki-67, blue staining as negative. The level of high expression of nuclear staining was, positive cells in DNMT1≥65%, in DNMT3a≥60% and in DNMT3b≥40%. The correlations of DNMT1, 3a and 3b expression in RB samples, and MIB-1 labeling index were analyzed. Results Viewed under the light microscope, negative expressions of DNMT1, 3a and 3b were demonstrated in normal retinas, however, positive expression was observed in RB samples, with 100% in DNMT1, 98% in DNMT3a and 92% in DNMT3b. Comparing well differentiated RB samples with poorly differentiated samples, significant differences were found in high expression ofDNMT1 （χ2=12.57, P〈0.05） and DNMT3a （ χ2=10.54, P〈0.05）; also in the positive cells of DNMT1 （U= 179, P〈0.05） and DNMT3a （U=198, P〈0.05）. No significant difference was found comparing high expression （χ2 = 1.5, P〈 0.05） and positive cells （U= 307, P〉 0.05） of DNMT3b. When comparing invasive tumor tissues with non-invasive tumors, significant differences were shown between high expression （χ2=4.72, P〈0.05） and positive cells comparing DNMT1 （U=236, P〈0.05）. No significant difference was shown in high expression χ2=3.53, 0.84;P〉0.05） in DNMT3a andDNMT3b, or in comparison with positive cells （U=338, 2573 P〉0.05）. The expression of DNMTs was positively correlated with the MIB-1 labeling index in RB tissues （R2 =0. 554, 0. 376, 0. 2193 P〈0.05）.