原发性胃癌p53基因突变

目的 p53基因是当前抑癌基因研究中的热点之一。迄今,有关 p53基因异常与胃癌临床病理学参数如大体类型、临床分期、组织分化程度,浸润深度及淋巴结转移之间的关系尚无定论。Tumura 报告p53基因改变主要发生于异倍体瘤,国内尚无报道。本实验目的主要是分析中国人原发性胃癌 p53基因突变与这些病理参数,包括 DNA 倍体之间的关系。方法用聚合酶链式反应—单构象多态分析(PCR—SSCP)技术对20例原发性胃癌 p53基因外显子5—8突变进行检测。结果 8例(40%)发生了突变,其中2例发生在外显子7,4例发生在外显子8。0至Ⅲ期均有突变存在。66.7%(6/9)的异倍体瘤检测到了p53突变,而二倍体瘤中只有18.2%(2/11)发生了 p53突变。结论 p53基因突变与胃癌临床病理参数如大体类型、分期、组织分化程度、浸润深度及淋巴结转移之间无明显关系,而与胃癌 DNA 倍体改变有关。     

肝细胞癌肿瘤抑制基因p53过度表达及点突变的研究

目的检测重庆地区肝细胞癌 p53突变发生率,并进一步探讨 p53突变与肝细胞癌临床病理及相关危险因素的关系.方法应用一种敏感的 ARF 免疫组化和 PCR、银染 PCR-SSCP 方法检测本地区38例肝细胞癌(HCC)组织中肿瘤抑制基因p53的过度表达及点突变.结果 16例有P53蛋白过度表达(41.2%),7例有 p53基因249位密码子点突变(18.4%),2例249位密码子外第7外显子点突变.9例 p53基因有突变的肝癌中8例 P53蛋白阳性,两者符合率为88.9%.p53基因蛋白过度表达和点突变与 HCC 分化和转移有关.本组 HCC p53基因突变率与该地区黄曲霉素(AFB1)含量及乙型肝炎病毒(HBV)感染分布一致.结论该结果提示 p53基因突变与 AFB1和 HBV 等环境因素的协同作用有关,其中 AFB1主要与 p53基因249位密码子特异型突变有关,而 HBV 可能在散发型突变中发挥重要作用.     

Correlation between mutations in p53 gene and protein expression in human lymphomas

A discordance between p53 protein overexpression and the presence of mutations in the gene has been observed in many types of tumors, including human lymphomas. To probe this finding, we have studied a large series of 94 lymphomas of different pathologic types and histologic differentiation. Analyzing exons 5–9, we have found mutations in the p53 gene in 7 of 94 cases distributed in different subtypes: 4/12 (33%) high-grade B-cell non-Hodgkin's lymphomas (B-NHLs), in 1 of 5 (20%) high-grade mucosa-associated lymphomas (MALT), in 1 of 22 (4.5%) anaplastic large cell lymphoma (ALCL), and in 1 of 24 (4%) T-cell NHLs. Immunostaining with anti-p53 antibody DO-7 was possible in 87 lymphomas, and overexpression of p53 protein was observed in 16 cases (18%). A discrepancy between the results of SSCP and immunostaining was detected in 18 tumor samples. Two cases with mutations in the gene showed no altered protein expression and 16 cases overexpressed p53 protein had no point mutations. In these cases, the possibility that mutations occur outside the exons studied has been tested and the entire coding sequence analyzed. Only one case showed a mutation in exon 10, and we found two cases carrying a polymorphism in exon 4 and in intron 10. We conclude that mutations in p53 occur mainly in high-grade B-cell NHLs. Although not limited to a specific subtype of lymphoma, they may be rare in Hodgkin's disease and in low-grade lymphomas. The discrepancies between overexpression and presence of mutations suggest (1) the existence of another mechanism to stabilize the p53 protein, and (2) that the immunohistochemistry cannot be used to predict mutations in the gene. Am. J. Hematol. 55:1-8, 1997. © 1997 Wiley-Liss, Inc.     

p53 gene mutations in multiple myeloma are associated with advanced forms of malignancy

The frequency and type of p53 gene mutations was investigated in a series of 52 cases of multiple myeloma (MM) representative of the different clinical phases and forms of the disease (indolent, 12 cases; chronic, 24 cases; acute/leukemic, 16 cases). DNAs were analyzed for p53 gene mutations in exons 5 to 9 by polymerase chain reaction (PCR), single-strand conformation polymorphism (SSCP), and direct sequencing of PCR-amplified fragments. Point mutations were detected in 7 of 52 patients (13%) (5 at exon 8; 1 at exon 6; 1 at exon 7), and were specifically associated with the more advanced and clinically aggressive acute/leukemic forms of MM (7 of 16 [43%].) Three of the mutated cases had been evaluated at clinical presentation in earlier phases of the disease (indolent or chronic) and were found to be negative for p53 mutation. Moreover, three patients with p53 mutation had not received chemotherapy at the time of investigation. These results support the notion that the development of MM is a multistep process and suggest that alterations in the p53 gene may represent an important late event in MM tumor progression.     

Prevalence and clinical significance of combined K-ras mutation and p53 aberration in pancreatic adenocarcinoma

Summary Conclusion This study could not attribute survival differences to the coincident acquisition of two common genetic alterations, K-ras mutation and p53 overexpression in pancreatic adenocarcinoma patients. Additionally, our data indicate the converse to be true: Those patients lacking both K-ras mutation and aberrant p53 expression showed the shortest survival when compared with cases showing either alteration or both. This study also showed the negative effect of K-ras mutation and p53 expression on pancreas cancer patient's survival after treatment with either radiation therapy or chemotherapy. Background Mutations of the oncogene K-ras at codon 12 are reported to be the most common genetic alteration in pancreatic carcinoma, whereas either overexpression or mutation of the tumor suppressor p53 gene is considered the most common genetic alteration in neoplasia of all types. p53 overexpression has been attributed to survival differences in pancreatic carcinoma, but such association is still controversial. No studies have fully documented the combined incidence of K-ras and p53 alterations in pancreatic adenocarcinoma, or their combined effect on patient survival in a large case series. The influence of radiation or chemotherapy in groups showing both, either, or neither mutation is also undocumented. Methods Paraffin-embedded tissue sections from 76 cases of pancreatic adenocarcinoma were cut for DNA extraction for K-ras analysis and immunohistochemical staining for aberrant p53 expression. K-ras mutation was determined by single-strand conformation polymorphism (SSCP) and slot-blot allele-specific oligonucleotide (ASO) hybridization of PCR-amplified DNA product. p53 expression was scored on the basis of percent nuclear staining with the MAb DO7. Results Sixty-four of 76 cases (84%) showed K-ras mutation, p53 expression, or both. K-ras was mutated in 55 of 76 cases (72%). p53 was expressed in 33 of 76 cases (43%). Twenty-four of 76 cases (31%) showed both K-ras mutation and p53 expression. The presence of both alterations was not related to significant differences in tumor grade, stage, or survival compared to either alteration alone. A sizable subset (16% of cases) lacked either alteration, and surprisingly, this group showed the shortest median survival compared to those with K-ras mutation, p53 expression, or both (p=0.024). Patients whose tumors were K-ras-negative showed the greatest difference in median survival with radiation therapy (median survival 30.8 mo vs 7.8 mo with no radiation,p=0.005).     

p53 and Follow-up of Colorectal Adenocarcinomas

Circulating p53 antibodies (ELISA method), p53genetic alterations (SSCP), and protein overexpression(immunohistochemistry) were studied in 41 patients withcolorectal adenocarcinomas and 10 control patients. Carcinoembryonic antigen (CEA) and carbohydrateantigen 19.9 (CA 19-9) were evaluated in parallel. Tenpatients with p53 antibodies and p53 overexpression wereselected. Tumor DNA extracts from these 10 patients were analyzed by SSCP. Of all 41patients, 10 (24%) showed significant levels of p53antibodies, and p53 accumulation was detected in 20(48%) patients. In six patients, p53 antibodieconcentrations decreased rapidly after surgery; in twopatients, these levels returned to normal values. Of the10 selected tumors, eight revealed TP53 gene mutations.Only two patients with high values of both CEA and CA 19-9 developed p53 antibodies. Inconclusion, beside classical tumor markers, circulatingp53 antibodies may be considered as additional markersfor the management of patients with colorectaladenocarcinomas.     

Mutations of p53 in thyroid carcinoma with an insular component.

Thyroid carcinoma with an insular component (TCIC) is considered noteworthy in view of its peculiar histopathological features and clinicopathological behavior. The purpose of the present study was to clarify the rate of mutation in the p53 gene in TCIC as compared with rates in papillary and follicular carcinomas of the thyroid. Formalin-fixed and paraffin-embedded blocks of tissue from 46 cases of TCIC were analyzed. DNA was extracted from tissues and exons 5 through 8 of the p53 gene were amplified by the polymerase chain reaction. Mutations were detected by analysis of single-strand conformation polymorphism. Of the 46 cases of TCIC, 6 had a mutation in exon 5, 2 in exon 7, and 5 in exon 8, while 1 case had mutations in all exons examined. The mutation rate of the p53 gene in TCIC was 38%. Immunostaining revealed overexpression of p53 in nuclei that were mainly in areas of the insular component rather than in surrounding areas of well-differentiated carcinoma. The frequency of positive immunostaining in TCIC was 53%. Considering that TCIC is intermediate between papillary plus follicular carcinoma and anaplastic carcinoma in terms of survival and the rate of mutation of the p53 gene, we can speculate that mutation in the p53 gene might be associated with the insular component and might play an important role in the clinicopathological behavior of thyroid carcinoma.     

Analysis of microsatellite instability,K-ras gene mutation and p53 protein overexpression in intrahepatic cholangiocarcinoma

BACKGROUND/AIMS: Genetic alterations are considered to play an important role in both the carcinogenesis and biological behavior of human malignancies. However, the clinical implications of intrahepatic cholangiocarcinoma are poorly understood. We investigated the microsatellite instability, K-ras gene mutations and p53 protein overexpression and their correlation with clinicopathological features to elucidate the clinical implications of genetic alterations in intrahepatic cholangiocarcinoma. METHODOLOGY: In twenty-three cases of surgically treated intrahepatic cholangiocarcinoma, microsatellite instability was examined by a PCR-SSCP analysis and K-ras gene mutation by a PCR-RFLP analysis, p53 protein overexpression by immunohistochemistry. We evaluated the correlation between genetic alterations and clinicopathological features. RESULTS: Microsatellite instability was observed in one case (4.7%), K-ras gene mutation in 9 (39.1%) and positive staining for p53 protein in 5 (21.7%). The incidence of K-ras gene mutations in hilar type intrahepatic cholangiocarcinoma (6 of 8, 75.0%) was significantly higher than that in peripheral type intrahepatic cholangiocarcinoma (3 of 15, 20.0%) (P < 0.05). Furthermore, the incidence of K-ras gene mutations in patients with lymph node metastasis (58.3%) tended to be higher than that in patients without lymph node metastasis (18.2%). The patients with K-ras gene mutations showed a statistically significant worse survival rate than those without such mutations (P < 0.05). No statistically significant correlations were observed between the p53 overexpression and clinicopathological features. CONCLUSIONS: These data suggest that K-ras gene mutations may be involved in the carcinogenesis of intrahepatic cholangiocarcinoma, especially in hilar type intrahepatic cholangiocarcinoma, and thus may be correlated with aggressive biological behavior.     

肝细胞癌抑癌基因p53突变

目的分析重庆地区肝细胞癌ｐ５３基因突变谱．方法住院肝细胞癌患者２０例，皆经病理证实，长期在重庆地区居住，其中早期小肝癌４例，中期６例，晚期１０例．采用ＰＣＲ－ＳＳＣＰ，ＰＣＲ直接测序技术分析ｐ５３基因５，６，７和８外显子突变．结果ｐ５３基因总的突变率为４０％．其中外显子５和６各占１０％，外显子７占２０％，未发现外显子８的突变；测序证实外显子７为第２４９位密码子Ｇ→Ｔ的颠换突变．突变病例多为晚期肿瘤．结论重庆地区肝细胞癌存在明显的ｐ５３基因突变，反映了该地区肝癌与黄曲霉毒素和ＨＢＶ或ＨＣＶ病毒有关     

Clinical implication of screening p53 gene mutations in head and neck squamous cell carcinomas

The role of the tumour-suppressor gene p53 in the tumorigenesis of head and neck cancer has been well established, but the clinical significance of p53 alteration is still unclear. A group of 50 patients with head and neck squamous cell carcinoma (HNSCC) were investigated for p53 alterations. DNA was extracted from fresh tumour samples and polymerase chain reaction/single-strand conformation polymorphism analysis was used to detect p53 gene mutations in the region from exon 5 to exon 9. In addition, p53 protein overexpression was assessed by immunohistochemistry using the monoclonal antibody DO-7 on paraffin-embedded tissue sections. p53 gene mutations were found in 45% and p53 protein expression was detected in 61.2% of tumour samples. While p53 protein expression was not correlated with any clinical factors, p53 gene mutations indicated local regional recurrences of HNSCC. The risk of locoregional recurrence was significantly greater in patients with a p53 gene mutation than in patients with the wild-type p53 gene (P = 0.001). Multivariate analysis confirmed p53 gene mutation to be an independently predictive factor for the tumour recurrence (P = 0.0064). When we analysed p53 gene mutation in 12 patients with primary and recurrent tumours, we found that 4 patients (33.3%) had a different p53 gene mutation in the recurrent tumour from that in the original primary tumour. The results indicate that p53 gene mutations and not protein overexpression are valuable predictors for tumour recurrences and for differential diagnosis of a second primary HNSCC. Received: 20 January 1998 / Accepted: 20 March 1998     

痰标本检测p53基因突变及其在肺癌早期临床诊断中的意义

目的　评价痰标本检测p53基因点突变方法及其作为肺癌早期临床诊断监测指标的真实性和可靠性。方法　用聚合酶链反应（PCR）-单链多肽性（SSCP）-银染法检测54例原发性肺癌患者和114例良性肺疾病患者痰标本中p53基因第5～8外显子的点突变,同时进行痰涂片细胞学检查。结果　p53突变在肺癌组检出率为55.56%(30/54),非肺癌组检出率为1.75%(2/114),P<0.001。痰标本检测p53基因突变作为肺癌临床诊断监测指标的灵敏性为55.56%,特异性为98.25%,阳性似然比为31.75。肺癌组p53阳性检出率（55.56%）与痰涂片瘤细胞阳性检出率（35.19%）比较,差异有显著性（P＜0.05）,关联性有极显著意义（P＜0.01）。肺癌组p53检出率与性别、吸烟指数、病理分型、疾病分期均无明显关系,但与年龄有密切关系,高龄患者（≥60岁）检出率高（P=0.02）。结论　PCR-SSCP-银染法检测痰标本p53突变可以在可疑肺癌患者（如吸烟并慢性肺疾患者）中作为一项随访监测指标,并将有助于肺癌的早期临床诊断。     

p53基因在食管癌组织中的高表达

本文利用免疫组化LSAB法检测了p53基因在35例食管癌组织中的表达情况。35例食管癌标本中，60％（21／35）的标本癌组织都存在有p53基因的高表达，其中18例标本同时存在有癌旁粘膜上皮p53基因在10例癌旁粘膜上皮中也存在高表达。p53的高表达主要位于核内，部分也有胞浆表达。p53基因的高表达与癌组织的分化程度有关，分化越差，阳性率越高（P＜0．0025）。p53基因的表达存在异质性，并与肿瘤细胞的浸润转移及细胞周期的不同有关。我们的结果表明，p53基因的高表达在食管癌的发生中是一个常见的基因改变，它在食管癌的发生发展中起着重要的作用。     

Novel small deletions of the p53 gene in late-stage B-cell chronic lymphocytic leukaemia

Summary . A group of 20 CLL patients selected for advanced clinical stage p53 mutations were analysed by single-strand conformational polymorphism (SSCP) following PCR amplification of exons 5–9. In two patients abnormal SSCP of either exon 5 or exon 8 was found and PCR products were analysed by direct sequencing. A hemizygous or homozygous 12bp deletion at codon 135 and 3bp heterozygous deletion at codon 264 were detected; also, in the latter sample a heterozygous mutation at codon 282 (Arg to Gln) was found. To our knowledge, this is the first report of p53 deletions in B-CLL. The two patients were elderly, and both had a rapidly progressive disease in the absence of unfavourable cytogenic abnormalities. These findings support a role for p53 alterations in the clinical course of some B-CLL patients.     

A study on p53 gene alterations in esophageal squamous cell carcinoma and their correlation to common dietary risk factors among population of the Kashmir valley

AIM: To systematically examine the extent of correlation of risk factors, such as age, consumed dietary habit and familial predisposition with somatic Tp53 molecular lesion causal to elevate carcinogenesis severity of esophageal squamous cell carcinoma (ESCC) among the Kashmiri population of Northern India. METHODS: All cases (n=51) and controls (n = 150) were permanent residents of the Kashmir valley. Genetic alterations were determined in exons 5-8 of Tp53 tumor suppressor gene among 45 ESCC cases histologically confirmed by PCR-SSCP analysis. Data for individual cancer cases (n = 45) and inpatient controls (n = 150) with non-cancer disease included information on family history of cancer, thirty prevailing common dietary risk factors along with patient's age group. Correlation of genetic lesion in p53 exons to animistic data from these parameters was generated by Chi-square test to all 45 histologically confirmed ESCC cases along with healthy controls. RESULTS: Thirty-five of 45 (77.8%) histologically characterized tumor samples had analogous somatic mutation as opposed to 1 of 45 normal sample obtained from adjacent region from the same patient showed germline mutation. The SSCP analysis demonstrated that most common p53 gene alterations were found in exon 6 (77.7%), that did not correlate with the age of the individual and clinicopathological parameters but showed significant concordance (P<0.05) with familial history of cancer (CD=58), suggesting germline predisposition at an unknown locus, and dietary habit of consuming locally grown Brassica vegetable "Hakh" (CD=19.5), red chillies (CD=20.2), hot salty soda tea (CD = 2.37) and local baked bread (CD=1.1). CONCLUSION: Our study suggests that somatic chromosomal mutations, especially in exon 6 of Tp53 gene, among esophageal cancer patients of an ethnically homogenous population of Kashmir valley are closely related to continued exposure to various common dietary risk factors, especially hot salty tea, meat, baked bread and "Hakh", that are rich in nitrosoamines and familial cancer history.     

Colorectal carcinoma prognosis can be predicted by alterations in gene <Emphasis Type="Italic">p53</Emphasis> exons 5 and 8

Background and aims Gene p53 alteration is a genetic event described in the progression from adenoma to colorectal carcinoma. Most of the p53 mutations occur in exons 5 to 8 in highly preserved regions and in the three main structural domains of the p53 protein. It is possible that mutations affecting different structural regions may present different effects on the p53 protein function and, due to this, they may have different prognostic meaning. Materials and methods The study population consisted of 353 patients diagnosed with sporadic colorectal cancer. Mutations in 5–8 exons of p53 gene were detected by means of single strand conformation polymorphism (SSCP). All samples that showed different migration bands in SSCP were confirmed by sequencing. Results A total of 69 patients (19.7%) showed alterations of the gene p53. It was observed that mutation in codon 175 in exon 5 was related to tumors located in the colon (p = 0.01) and the mutation in the codon 288 in exon 8 was related to rectal tumors (p = 0.02). In the study of overall survival, mutation in codon 175 of exon 5 conferred a better prognosis and alterations of exon 8 were related to a worse prognosis in different population subgroups: in men, in patients younger than 71 years old, in the tumors located in the proximal colon, the ones moderately differentiated, and those that are mucinous. Conclusion According to this study, mutations in different exons of p53 are related to different phenotypes in colorectal cancer. These phenotypes could mean differences in the clinical evolution of the patients. This study was supported by grant no. PI030514 from the Fondo de Investigaciones Sanitarias, Spain.     

Co-mutation of p53, K-ras genes and accumulation of p53 protein and its correlation to clinicopathological features in rectal cancer

AIM: To determine bhe accuracy of p53 gene mutations predicted by overexpression of p53 protein immunohistochemically,and to investigate the co-mutation of p53 and K-ras genes in rectal cancer and its effect on promoting malignant biologic behaviors of tumors.METHODS: Ninety-seven specimens of rectal cancer were surgically resected in our hospital from August 1996 to October 1997. The hot mutation areas of p53 gene (in exons 5-8) and K-rasgene (in codon 5/12 and 13) were detected with polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP), and overexpression of p53 protein was detected with immunohistochemistry (IHC) in the 97 specimens of rectal cancer. Correlation between gene mutations and tumor clinicopathologic factors was studied, and survival analysis was penfomed as well.RESULTS: There were 36 cases of p53 gene mutations in 61 p53 protein positive cases, and 21 cases of p53 gene non-mutation in 36 p53 protein negative cases respectively.The coincidence rate of p53 gene mutation by IHC method with PCR-SSCP method was 58.8% (57/97). The mutation rate of p53 gene was 52.6% (51/97), while K-ras gene mutation was observed in codons 12 and 13 in 61 cases with a mutation rate of 62.9% (61/97). Single gene mutation of p53 or K-raswas found in 32 cases. Both p53 and K-ras gene mutation were found in 48 cases. Statistical analysis showed that p53 and K-ras gene mutations were not related to the dinicopathologic factors, including tumor size, gross tumor type, histological dassification, differentiation, invasion to intestinal veins, lymphatics and nerves, invasive depth to.wall, lymph node metastasis, and Dukes‘ stages (P&gt;0.05).The survival in patients with no gene mutation, single gene mutation and both gene mutations were similar (P&gt;0.05).CONCLUSION: IHC has a certain false positive and false negative rate in detecting p53 gene mutations. Malignant biological behaviours of rectal cancer are not enhanced by p53 and K-rasgene mutations. Co-mutation of p53 and K-ras gene has neither synergic carcinogenesis-promoting effect,nor prognostic effect on rectal cancer.     

Prognostic significance of p53 and bcl-2 abnormalities in operable nonsmall cell lung cancer.

The association of p53 abnormalities and bcl-2 protein expression with clinical data and prognosis in 102 patients with resected nonsmall cell lung cancer (NSCLC) was investigated. Deoxyribonucleic acid analysis of exons 5-8 of the p53 gene showed mutations (p53-M) in 47% of resected NSCLC, serum p53 antibodies (p53-Abs) were detected in 25%, p53 protein overexpression (p53-PE) in 54%, and bcl-2 protein overexpression (bcl-2-PE) in 48%. A statistically significant association was found between p53-PE, serum p53-Abs and the presence of a p53 gene alteration. No significant associations were found between results of the p53-M, p53-Abs, bcl-2-PE tests and clinicopathological parameters. In the case of the p53-PE test there were significantly fewer positive results for adenocarcinoma than for squamous cell carcinoma and large cell carcinoma. Survival analysis showed that both p53 abnormalities and negative staining for bcl-2, when analysed separately, were associated with poor overall survival. In a multivariate analysis, only the positive result of the p53-M test remained an independent, statistically significant, unfavourable prognostic factor for survival. When the p53 mutation test was removed from the model, positive results of the p53-PE test and the p53-Abs test became statistically significant, unfavourable prognostic factors. To conclude, among p53 and bcl-2 abnormalities, only p53 gene mutations seem to have a strong and independent effect on prognosis. When deoxyribonucleic acid sequence information is not available, p53 protein expression and the presence of p53 antibodies in serum may be used to obtain important prognostic information.     

Analysis of p53 mutations in a large series of lymphoid hematologic malignancies of childhood

p53 mutations are found in a wide variety of cancers, including hematologic malignancies. These alterations apparently contribute to development of the malignant phenotype. We analyzed a large series of lymphoid (330 cases) and a smaller series of myeloid (29 cases) malignancies of childhood for p53 mutations by single-strand conformational polymorphism (SSCP) following polymerase chain reaction. Samples with abnormal SSCP were reamplified and analyzed by direct sequencing method. p53 mutations were detected within the known mutational hotspots (exons 5 to 8) in 8 of 330 lymphoid malignancies, and in none of 29 myeloid malignancies, showing that the frequency of p53 mutations in childhood lymphoid malignancies was very low (8 of 330 cases [2%]). Four of these patients had very aggressive, fatal acute lymphocytic leukemia (ALL). None of 13 infants and none of 48 patients with T-lineage leukemia had detectable p53 mutations in their ALL cells. Exceptionally, p53 mutations were comparatively frequent in a small sample of B-cell non-Hodgkin's lymphomas (2 of 8 cases). Mutations were detected in samples from two patients with ALL at relapse; these were not detected in samples at initial diagnosis from the same patients, suggesting that p53 mutations may be associated with progression to a more malignant phenotype. Seven of eight alterations of p53 were missense mutations, and seven of eight samples may be heterozygous for the mutant p53, indicating that p53 protein may act in a dominant negative fashion.     

Analysis of K-ras codon 12 mutations and p53 overexpression in colorectal nodule-aggregating tumors

BACKGROUND AND AIMS: Morphologically, colorectal nodule-aggregating tumors are quite different from polypoid-type colorectal tumors that develop via the adenoma-carcinoma sequence. Although polypoid-type colorectal tumors are well known to have a high incidence of K-ras gene mutation and p53 overexpression, colorectal nodule-aggregating tumors have not been examined in terms of genetic changes and clinicopathological features. In the present study, therefore, we analysed the clinicopathological features, genetic changes in K-ras codon 12, and p53 overexpression in colorectal nodule-aggregating tumors. METHODS: A total of 18 colorectal nodule-aggregating tumors were surgically resected and then analysed clinicopathologically. Immunohistochemistry and polymerase chain reaction-single stranded conformational polymorphism were performed to analyse p53 abnormalities in the tumors. K-ras codon 12 mutations were screened out by the polymerase chain reaction-restriction fragment length polymorphism method and analysed by fluorescence direct sequencing. RESULTS: p53 overexpression was observed in six lesions (33%). p53-overexpressing cells were observed in parts of carcinoma or adenoma showing high-grade atypia. Four of the 10 (40%) samples had a p53 gene mutation. Nine of the 18 (50%) samples had a K-ras codon 12 point mutation. In eight cases (89%), the mutations of the K-ras codon 12 were of the same type: GGT (glycine) to GTT (valine). CONCLUSIONS: The colorectal nodule-aggregating tumor has distinctive characteristics showing a morphological phenotype of the superficial-type tumors and genotype of the polypoid tumors in terms of K-ras gene mutation and p53 overexpression.