Gu Li-jun, Chen Jie, Liu Tong-hua, Cui Quan-cai, Lu Zhao-hui, Li Li, Gao Jie
Department of Pathology, PUMC Hospital, CAMS, PUMC, Beijing 100730, China.
Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 2002 Apr;24(2):165-9.
To demonstrate the alterations of DPC4/SMAD4/MADH4 gene in paraffin-embedded tissues of pancreatic carcinomas.
Forty-six cases of resected specimens containing carcinomatous tissue and normal pancreatic tissue were analysed for possible DPC4 gene mutations by polymerase chain reaction (PCR)and single-strand conformation polymorphism (SSCP). The DNA sequencing technique was applied to determine the patterns of gene mutation in the PCR-SSCP positive cases. Fifty-six cases of pancreatic carcinoma along with the specimens corresponding normal pancreatic tissues were studied by in situ hybridization (ISH) and immunohistochemistry (IHC) techniques for gene expression in mRNA and protein level.
The homozygous deletion rate of exon 1, 2, 3, 4, 8, 11 of DPC4 gene in pancreatic carcinoma was 28.26%, while the mutation rate of DPC4 gene was 21.74%. In these tumors, there were 3 cases of nonsense mutation, 5 cases of missense mutation, 1 case of deletion and missense mutation, 1 case of insertion mutation. Positive rates of SMAD4 in carcinomatous tissues detected by the ISH and IHC were 53.57% and 58.93% respectively, whereas they were 91.07% and 89.29% in the matched normal tissue respectively. There were significant difference between cancer and normal tissue (P < 0.05). Thrity-two cases were positive of DPC4/SMAD4 with all methods mentioned above, the coincident rate was 87.50% (28/32). The coincidence between gene detection and ISH of SMAD4 was 87.50%, and it was 96.88% between gene detection and IHC of SMAD4. Of all 56 cases, the coincidence of the positive rates of SMAD4 detected by ISH and IHC was 91.07%. No significant difference among the positive rates of DPC4/SMAD4 as detected by the three different techniques (P > 0.05).
The main mechanisms of inactivation of DPC4 gene in pancreatic carcinoma are homozygous deletion and mutation. The product of DPC4 expression is significantly decreased in cancer group compared with the normal tissues. As a tumor suppressor gene, DPC4 alteration is an important molecular event in pancreatic carcinoma, and probably plays a crucial role in cancer development and progression.
探讨胰腺癌石蜡包埋组织中DPC4/SMAD4/MADH4基因的改变情况。
采用聚合酶链反应（PCR）和单链构象多态性（SSCP）技术，对46例包含癌组织和正常胰腺组织的切除标本进行DPC4基因突变分析。对PCR-SSCP阳性病例应用DNA测序技术确定基因突变类型。采用原位杂交（ISH）和免疫组织化学（IHC）技术，对56例胰腺癌及其相应正常胰腺组织标本进行基因在mRNA和蛋白质水平表达的研究。
胰腺癌中DPC4基因第1、2、3、4、8、11外显子的纯合缺失率为28.26%，DPC4基因突变率为21.74%。这些肿瘤中，有3例无义突变、5例错义突变、1例缺失与错义突变、1例插入突变。ISH和IHC检测癌组织中SMAD4的阳性率分别为53.57%和58.93%，而配对正常组织中分别为91.07%和89.29%。癌组织与正常组织之间差异有统计学意义（P<0.05）。上述所有方法检测DPC4/SMAD4阳性32例，符合率为87.50%（28/32）。基因检测与SMAD4的ISH符合率为87.50%，基因检测与SMAD4的IHC符合率为96.88%。56例中，ISH和IHC检测SMAD4阳性率的符合率为91.07%。三种不同技术检测DPC4/SMAD4阳性率差异无统计学意义（P>0.05）。
胰腺癌中DPC4基因失活的主要机制是纯合缺失和突变。与正常组织相比，癌组织中DPC4表达产物明显减少。作为一种肿瘤抑制基因，DPC4改变是胰腺癌中的一个重要分子事件，可能在肿瘤发生发展中起关键作用。
