中国人卵巢上皮性肿瘤nm23H1基因遗传不稳定性的研究

STUDY ON GENETIC INSTABILITY OF NM23H1 GENE IN CHINESE WITH THE EPITHELIAL OVARIAN TUMOR

采用石蜡包埋组织抽提DNA,PCR-单链构象多态性(PCR-SSCP),常规银染、Envision免疫组织化学染色和Leica-Qwin计算机图像分析等方法,研究人类17号染色体D17S396位点微卫星不稳定(microsatellite instablility,MSI)和杂合性缺失(loss of heterozygosity,LOH),对卵巢上皮性肿瘤nm23H1蛋白表达的影响,阐明nm23H1基因遗传不稳定性与卵巢肿瘤进展的关系,为揭示nm23H1基因作用机制和肿瘤转移机制提供实验依据。本实验中,卵巢上皮性癌D17S396位点遗传不稳定发生率为40%,明显高于交界性肿瘤的9.52%,而在良性肿瘤和正常卵巢组织中,未见该位点遗传不稳定的发生。其中,LOH的发生率,随肿瘤恶性程度的增高而增加(P<0.05)。在卵巢上皮性癌中,淋巴转移组的LOH发生率高于无淋巴转移组(P<0.01)。FIGO Ⅲ+Ⅳ期的LOH发生率高于Ⅰ+Ⅱ期(P<0.05)。MSI发生率与卵巢上皮癌组织类型、分化程度、淋巴转移及FIGO分期均无关。nm23H1 蛋白阳性率在卵巢上皮性癌和交界性肿瘤组织中分别为56.00%和57.14%,高于良性肿瘤的13.64%和正常卵巢组织的8.33%(P<0.01)。卵巢上皮性癌中,淋巴转移组nm23H1蛋白阳性率低于无淋巴转移组;FIGO Ⅲ+Ⅳ期nm23H1蛋白阳性率低于Ⅰ+Ⅱ期(P<0.05)。此外,计算机图像定量分析显示,在各临床病理参数影响下,nm23H1蛋白的表达强度没有差异。在卵巢上皮性癌中,LOH阳性组中nm23H1蛋白阳性率为0.00%,显著低于LOH阴性组的73.68%(P<0.01)。实验结果提示, nm23H1基因的遗传不稳定性可能是卵巢上皮性癌发生、发展的一个重要机制。LOH的发生可作为卵巢组织恶变的判断指标。nm23H1基因的MSI和LOH,通过相互独立的途径调控卵巢上皮癌的发生和转移,后者可抑制卵巢上皮癌局部nm23H1蛋白的表达,并赋予卵巢上皮癌高淋巴结转移、低预后的特性。提高卵巢上皮癌局部nm23H1蛋白的表达,可减缓肿瘤的淋巴转移并提高预后率。

The aim of this study was to examine microsatellite instability (MSI) and loss of heterozygosity (LOH) of locus D17S396 on chromosome 17 and their influence on the expression of nm23H1 in the epithelial ovarian tumors, which may provide experimental basis for the mecha- nism of nm23H1 gene and tumor metastasis. Techniques such as DNA extraction from formalin- fixed paraffin-embedded tissues, polymerase chain reaction-single strand conformation polymor- phism (PCR-SSCP), ordinary silver stain were used to study MSI and LOH of locus D17S396. En- vision immunohistochemistry and Leica-Qwin computer imaging techniques were used to assess the expression of nm23H1 gene. In our experiments, the frequency of heredity instability of malignant ovarian tumors was 40%, which is higher than that of borderline ovarian tumors, while there were no heredity instability occurred in benign ovarian tumors and normal ovarian tissue. Among 25 epithelial ovarian carcinomas, the frequency of LOH in lymph node metastasis cases (66.67%) was significantly higher than those without metastasis (10.53%). Moreover, the frequency of LOH was higher in FIGO stage Ⅲ and Ⅳ than in stage Ⅰ and Ⅱ. However, the frequency of MSI showed no correlation with any clinicopathologic characteristics. The positive frequency of nm23H1 protein in the ovarian epithelial carcinoma and borderline tumors were 56.00% and 57.14%, respectively. They were both higher than those of the benign tumors and normal ovarian tissue. In the epithe- lial ovarian carcinomas, the positive frequency of nm23H1 protein in lymph node metastasis case was significantly lower than those without metastasis. FIGO stage Ⅲ and Ⅳ also exhibited lower positive frequency of nm23H1 protein compared with stage Ⅰ and Ⅱ. Furthermore, there was no difference in nm23H1 protein expression intensity analyzed by computer imaging. In the epithelial ovarian carcinomas, the positive frequency of nm23H1 protein in LOH positive group was 0.00%, which is lower than that of LOH negative group (P<0.01). The results indicated that the heredity instability of nm23H1 gene might be implicated in pathogenesis and progression of epithelial ovari- an tumor. The occurrence of LOH might be the molecule marker of the deteriorism of ovarian tissue. Both MSI and LOH of nm23H1 gene controlled development of the epithelial ovarian tumor independently in different paths. LOH could inhibit the expression of nm23H1 in local tissue of the epithelial ovarian carcinoma, which endowed it with high aggressive and poor prognosis. In- creasing the amount of nm23H1 protein expression could effectively restrain metastasis of the ovarian epithelial carcinoma and improve prognosis of patients.