Patterns of genetic alterations in pancreatic cancer: a pooled analysis

Both K-ras and p53 gene mutations are found commonly in pancreatic tumors. Analysis of the mutational patterns may provide insight into disease etiology. To further describe the mutational patterns of pancreatic cancer and to assess the evidence to date, we performed a pooled analysis of the published data on genetic mutations associated with pancreatic ductal adenocarcinoma. We included data from studies that evaluated point mutations in the two genes most studied in pancreatic cancer, K-ras and p53. A majority of the 204 tumors had mutations in at least one gene, with 29% having both K-ras and p53 mutations, 39% with K-ras mutation alone, and 16% having p53 mutation alone. Sixteen percent of tumors lacked mutation in either gene. K-ras mutations were present in high frequencies in all tumor grades (>69%). A statistically significant trend was observed for p53 mutation with higher tumor grade (P = 0.04). For K-ras, G2 and G3 grades, combined, had notably higher prevalences of mutation than G1 (P = 0.004). CGT mutations in K-ras codon 12 were marginally associated with lower tumor grade (P for trend = 0.09), and these tumors were somewhat less likely to have a p53 mutation than tumors with other K-ras mutations (P = 0.06). In the 59 K-ras+/p53+ tumors, 64% had the same type of mutation (transition or transversion) in both genes, suggesting a common mechanism. The mutational pattern of p53 in pancreatic cancer is similar to bladder cancer, another smoking-related cancer, but not to lung cancer. Analyses of molecular data, such as that performed here, present new avenues for epidemiologists in the study of the etiology of specific cancers.     

K-ras oncogene activation in adenocarcinoma of the human pancreas. A study of 82 carcinomas using a combination of mutant-enriched polymerase chain reaction analysis and allele-specific oligonucleotide hybridization.

We examined 82 surgically resected or biopsied, formalin-fixed, paraffin-embedded primary adenocarcinomas of the pancreas for the presence of activating point mutations in codon 12 of the K-ras oncogene. Mutations were detected using primer-mediated, mutant-enriched, polymerase chain reaction-restriction fragment length polymorphism analysis and characterized further by allele-specific oligonucleotide hybridization. This combination of mutant-enriched polymerase chain reaction-restriction fragment length polymorphism analysis and allele-specific oligonucleotide hybridization results in a rapid and sensitive characterization of the mutations in codon 12 of K-ras. Sixty-eight (83%) of the 82 carcinomas examined harbored a point mutation. Of the 68 mutations, 33 (49%) were guanine to adenine transitions, 27 (39%) were guanine to thymine transversions, and eight (12%) were guanine to cytosine transversions. Mutations were found in carcinomas of the head (61 of 75, 81%) as well as in carcinomas of the body or tail (seven of seven, 100%) of the pancreas. The overall prevalence of K-ras point mutations in adenocarcinomas of the pancreas obtained from patients who smoked cigarettes at some point during their lives (88%; 86% in current smokers and 89% in ex-smokers) was greater than that seen in pancreatic adenocarcinomas from patients who never smoked cigarettes (68%, P = 0.046). The presence of K-ras point mutations did not correlate with tumor ploidy, tumor proliferating index, or patient survival. These results demonstrate that primer-mediated, mutant-enriched polymerase chain reaction-restriction fragment length polymorphism analysis combined with allele-specific oligonucleotide hybridization can be used to detect and characterize mutations in codon 12 of the K-ras oncogene in formalin-fixed, paraffin-embedded tissues, and the results confirm that activating point mutations in codon 12 of the K-ras oncogene occur frequently in adenocarcinomas of the pancreas.     

Incidence of P53 and K-ras alterations in ovarian mucinous and serous tumors

Clarification of the pathogenic relationships existing among ovarian cystadenomas, tumors of low malignant potential (LMP) and various adenocarcinoma types, a series of 29 mucinous and 19 serous ovarian tumors including adenomas, LMP tumors and adenocarcinomas were examined. P53 protein was detected by the streptavidin-biotin method and point mutation of K-ras codon 12 was detected by polymerase chain reaction-restriction fragment length polymorphism analysis. P53 overexpression was observed more frequently in serous adenocarcinomas (5/8, 63%) than in mucinous adenocarcinomas (2/9, 22%) and was correlated with the malignant potential of serous tumors. Furthermore, the proportion of P53-positive cells was significantly higher in serous adenocarcinomas than in mucinous adenocarcinomas. P53 overexpression may therefore be closely related to the early events of carcinogenesis in serous tumors. Although mutation of the K-ras oncogene appears to be an important event in the early tumorigenesis of mucinous tumors, mutation of the K-ras oncogene in serous tumors may be dependent on morphology. Different complex pathways of oncogene and/or tumor suppressor gene abnormalities may be involved in the development of mucinous and serous adenocarcinomas.     

Mutational activation of the K-ras oncogene. A possible pathogenetic factor in adenocarcinoma of the lung

To define the role of cellular oncogenes in human cancers, we studied the prevalence of mutational activation of ras oncogenes in untreated non-small-cell lung cancer. Genomic DNA was extracted from 39 tumor specimens obtained by thoracotomy and was examined for activating point mutations in codons 12, 13, and 61 of the H-ras, K-ras, and N-ras genes. A novel, highly sensitive assay based on oligonucleotide hybridization following an in vitro amplification step was employed. The K-ras gene was found to be activated by point mutations in codon 12 in 5 of 10 adenocarcinomas. Two of these tumors were less than 2 cm in size and had not metastasized. No ras gene mutations were observed in 15 squamous-cell carcinomas, 10 large-cell carcinomas, 1 carcinoid, 2 metastatic adenocarcinomas from primary tumors outside the lung, and 1 small-cell carcinoma. An approximately 20-fold amplification of the unmutated K-ras gene was observed in a tumor that proved to be a solitary lung metastasis of a rectal carcinoma. We conclude that mutational K-ras activation may be an important early event in the pathogenesis of adenocarcinoma of the lung but that amplification of ras genes or mutational activation of H-ras or N-ras does not play a major part in non-small-cell lung cancer.     

A subset of lung adenocarcinomas and atypical adenomatous hyperplasia-associated foci are genotypically related: an EGFR, HER2, and K-ras mutational analysis

Atypical adenomatous hyperplasia (AAH) is considered the preinvasive lesion of pulmonary adenocarcinoma, and mutations of EGFR, HER2, and K-ras are involved in the early stage of lung adenocarcinoma carcinogenesis, also predicting clinical response to anti-EGFR small molecule inhibitors. We analyzed 18 cases of primary lung adenocarcinoma with concomitant AAH foci from 13 patients for mutations of EGFR (exons 18-21), HER2 (exons 19-20), and K-ras (exon 2) by direct sequencing polymerase chain reaction. Among mutated cases, concordant mutations of EGFR or K-ras in adenocarcinoma and related AAH were observed in 5 (63%) of 8 cases. In particular, 3 of 4 adenocarcinomas with EGFR mutations (all L858R point mutations in women, never or former smokers) had a concomitant and identical mutation in AAH, and 2 of 4 adenocarcinomas with K-ras mutations (both at codon 12 in women, a never and a current smoker) showed the same mutation in concomitant AAH. All cases were wild-type for HER2. Mutations of EGFR and K-ras genes represent an early event in lung adenocarcinomagenesis, and AAH convincingly seems to be a precursor lesion in a subset of cases of adenocarcinoma.     

K-ras mutation detection in colorectal cancer using the Pyrosequencing technique

The identification of gene mutations is a critical goal for the assessment of diagnosis and prognosis in cancer disease, particularly by direct sequencing. Pyrosequencing is a straightforward, non-electrophoretic DNA sequencing method using the luciferase-luciferin light release as a signal for nucleotide incorporation into a PCR template DNA. In this study, we aimed to investigate mutations in the K-ras gene using Pyrosequencing technology, because its reliable chemistry and robust detection mechanism allow for rapid, real-time detection of sequencing events. For the simultaneous detection of the predominant K-ras codons 12 and 13 mutations, we established a sequencing protocol based on the design of a single PCR primer pair and a single sequencing primer. The assay has been validated with DNA from 65 colorectal carcinomas. Furthermore, analysis of the rare K-ras codon 61 mutation was included. In 29% (19/65) of the patients, the K-ras gene was found to be mutated, whereas codons 12 and 13 were most frequently affected (18/65, 27.7%). Mutations with the highest frequency were G-->A transitions (12/19, 63%), followed by G-->T transversions (5/19, 26%). Overall survival was significantly shorter in patients with a tumor containing K-ras codon 12 mutations than in those without K-ras codon 12 mutations (p=0.024). In conclusion, we found Pyrosequencing to be a suitable technology for fast detection of hot-spot mutations in the K-ras oncogene. We demonstrated an important relationship between K-ras codon 12 mutations and overall survival in colorectal cancer patients.     

特异引物双扩增即时PCR与传统测序法检测肠癌、肺癌患者K-ras基因突变的比较

目的 以特异引物双扩增即时PCR技术K-ras检测试剂盒(下称ADx-K-ras即时PCR试剂盒)和Sanger DNA测序法同时检测结直肠癌和肺癌患者K-ras基因,以了解K-ras基因突变频率和突变类型,比较ADx-K-ras即时PCR试剂盒和Sanger DNA测序法用于肿瘤K-ras基因体细胞突变检测的临床价值.方法 收集临床肿瘤病理石蜡切片样品827例,其中肠癌样品583例,肺癌样品244例,提取DNA后,对K-ras基因第12和13密码子进行PCR扩增后,使用ADx-K-ras即时PCR试剂盒进行检测,与此同时,将PCR扩增后的产物进行Sanger DNA测序.两种方法对K-ras基因第12和13密码子的检测结果进一步进行各个突变类型的数目和突变率的统计对比.结果 ADx-K-ras即时PCR试剂盒对827例样品检测都得到了明确的结果,检测成功率为100%,Sanger DNA测序成功检测了677例,成功率为81.9%.583例肠癌样品中ADx-K-ras即时PCR试剂盒检测出突变192例,突变检出率为32.9%,Sanger DNA测序成功的样品533例,检出突变160例,突变检出率为30.0%.244例肺癌样品中ADx-K-ras即时PCR试剂盒检出突变26例,突变检出率为10.7%,Sanger DNA测序成功的样品144例,检出突变12例,突变检出率为8.3%.肠癌中第12密码子第2位的GGT→GAT最常见,占全部突变的35.1%(66/188),其次是第13密码子第2位的GGC→GAC,26.6%(50/188),第12密码子第2位的GGT→GTT,18.6%(35/188),第12密码子第1位的GGT→GCT最少见,1.6%(3/188).肺癌中第12密码子第1位的GGT→GTT最常见,占全部突变的40.9%(9/22),同样第12密码子第1位的GGT→GCT最少见,占全部突变的4.5%(1/22).结论 肠癌中K-ras突变率明显高于肺癌.对于甲醛固定石蜡包埋样品而言,ADx-K-ras即时PCR试剂盒对样品的DNA质量的耐受性较好,检测成功率高于Sanger DNA测序,可替代Sanger DNA测序法成为临床上对肿瘤K-ras基因体细胞突变检测的实用方法.     

Characterization of adenocarcinoma of the lung in a familial adenomatous polyposis patient

The incidence of several extracolonic tumors, such as duodenal carcinoma, is higher in familial adenomatous polyposis (FAP) patients than in the general population, but there is little information about lung carcinoma in FAP. A 43-year-old woman presented with a lung tumor 17 years after total colectomy for FAP. Pathohistological analysis of the lung tumor demonstrated mixed adenocarcinoma consisting of a papillary adenocarcinoma component and a bronchioloalveolar carcinoma component. Sequencing analysis indicated a germline APC mutation from TCA to TGA (stop) at codon 1110, but no pathogenic germline MYH mutations. The other APC allele in the lung carcinoma was not inactivated by somatic mutations, promoter methylation, or chromosomal deletion. No somatic mutations in any of the coding regions of the p53 gene or in the mutation hot spot regions of the K-ras or EGFR genes were detected in the carcinoma. Amplification, however, of three chromosome regions, 5p, 8q, and 12q14-12q21, was identified in the carcinoma on genome-wide high-resolution single-nucleotide polymorphism (SNP) microarray. The present results suggest that the chromosomal copy number alterations detected on SNP microarray were involved in the carcinogenesis of the adenocarcinoma of the lung in the present FAP patient.     

吸烟与肺癌p53及K-ras基因突变关系的研究进展

p53和K ras基因突变常见于肺癌,吸烟是引起p53和K ras基因突变的主要危险因素。吸烟 相关性肺癌基因突变以G→T为主,这在其它肿瘤及不吸烟者肺癌很少见。p53基因突变常发生于第157、 156、245、248、273密码子,K ras基因突变常发生于第12密码子,他们都是烟草致癌物的强结合位点。对吸烟 与p53、K ras基因突变关系的研究,在临床早期诊断及判断预后等方面均有应用价值。     

Differences in the frequencies of K-ras c12-13 genotypes by gender and pathologic phenotypes in colorectal tumors measured using the allele discrimination method

The frequencies of different genotypes of the K-ras oncogene in colorectal cancer (CRC) reveal complex relationships among gender, age, and tumor aggression, however, differences among these studies could also be attributed to a lack of standardization of the detection methods used. We developed the allele discrimination assay, which uses dual-color real-time polymerase chain reaction (qPCR) as a fast K-ras genotyping method, and demonstrated higher sensitivity and specificity than DNA sequencing with formalin-fixed paraffin tissues. The assay detected K-ras mutations among 83 of 204 patients with CRC (40.7%); 20.6% of these mutations were G12D (GAT) mutations, 7.4% were G13D (GAC) and G12V (GTT), and 5.3% were other types. A higher proportion of females was observed overall in tumors with K-ras mutations (60.2%, P = 0.01), codon 12 mutations (63.2%, P = 0.005), and transversions (69.6%, P = 0.02), which reflected the higher prevalence of females among the well- to moderately differentiated tumors (29% in males vs. 53% in females; interaction P = 0.03). The opposite was observed for poorly differentiated tumors (47% in males vs. 35% in females). No significant influence of age was found on the prevalence of K-ras mutation. Males with pathological changes and females with poorly differentiated tumors displayed GAT as a less common genotype compared with most other prevalence studies. In conclusion, allele discrimination, with no additional amplification step, is a fast and reliable genotyping method for detecting K-ras c12-13 mutations. Using this method, we demonstrate differences in the frequencies of K-ras genotypes by gender and pathologic phenotypes of CRC.     

卵巢浆液性交界及恶性肿瘤K-ras基因突变分析

目的探讨K-ras基因在卵巢浆液性交界及恶性肿瘤发生发展过程中的作用。方法收集51例卵巢浆液性肿瘤标本,包括经典型交界性浆液性肿瘤18例,微乳头型交界性浆液性肿瘤11例,浸润性微乳头型浆液性癌12例,经典型浆液性癌10例。采用显微切割技术获取肿瘤细胞后,提取基因组DNA、PCR技术扩增K—ras基因第一外显子,通过直接测序的方法鉴定K—ras基因第12、13密码子的突变情况。结果1例经典型交界性浆液性肿瘤K—ras基因第12密码子发生突变,突变类型为GGT→GTT即甘氨酸→缬氨酸,余50例标本未见突变;所有标本K—ras基因第13密码子均为野生型。结论K—ras基因第12、13密码子在被检患者中卵巢浆液性交界及恶性肿瘤中的突变频率很低,其在该肿瘤发生发展过程中可能不起主要作用。     

c-k-ras and p53 mutations occur very early in adenocarcinoma of the lung.

The topographical distribution of a mutation provides insight into past patterns of tumor evolution. This approach was applied to two loci commonly mutated in adenocarcinoma of the lung--p53 and c-K-ras. In 41 primary adenocarcinomas, c-K-ras codon 12 point mutations were detected in 8 (19.5%) tumors and p53 point mutations were detected in 10 (24.4%) tumors, with one tumor harboring both mutations. These mutations were only detected in malignant cells and with a homogeneous topographical distribution throughout 16 tumors, including metastasis. Intratumor heterogeneity was detected in only one tumor in which a small portion lacked the specific p53 mutation. Based on this topographical analysis, it is likely that when these mutations occur in adenocarcinoma of the lung, they are usually acquired during the very earliest phases of tumor formation before the bulk of clonal expansion, and in very small precursor lesions.     

Genetic alterations in K-ras and p53 cancer genes in lung neoplasms from B6C3F1 mice exposed to cumene

The incidences of alveolar/bronchiolar adenomas and carcinomas in cumene-treated B6C3F1 mice were significantly greater than those of the control animals. We evaluated these lung neoplasms for point mutations in the K-ras and p53 genes that are often mutated in humans. K-ras and p53 mutations were detected by cycle sequencing of PCR-amplified DNA isolated from paraffin-embedded neoplasms. K-ras mutations were detected in 87% of cumene-induced lung neoplasms, and the predominant mutations were exon 1 codon 12 G to T transversions and exon 2 codon 61 A to G transitions. P53 protein expression was detected by immunohistochemistry in 56% of cumene-induced neoplasms, and mutations were detected in 52% of neoplasms. The predominant mutations were exon 5, codon 155 G to A transitions, and codon 133 C to T transitions. No p53 mutations and one of seven (14%) K-ras mutations were detected in spontaneous neoplasms. Cumene-induced lung carcinomas showed loss of heterozygosity (LOH) on chromosome 4 near the p16 gene (13%) and on chromosome 6 near the K-ras gene (12%). No LOH was observed in spontaneous carcinomas or normal lung tissues examined. The pattern of mutations identified in the lung tumors suggests that DNA damage and genomic instability may be contributing factors to the mutation profile and development of lung cancer in mice exposed to cumene.     

ras gene mutations in salivary gland tumors

OBJECTIVE: To assess the prevalence of activating mutations in K-ras and H-ras genes in salivary gland tumors with ductal or acinar differentiation and to evaluate their potential correlation with clinical parameters. DESIGN: Paraffin-embedded tissue samples of salivary gland carcinomas were investigated by the application of a direct sequence analysis procedure with automated DNA sequencing of polymerase chain reaction-amplified ras sequences. SETTING: Tertiary care teaching hospital. PATIENTS: Twenty-four patients with salivary gland carcinoma were surgically treated. Nine had adenocarcinoma, 1 had adenosquamous carcinoma, 11 had mucoepidermoid carcinoma, and 3 had acinic cell carcinoma. RESULTS: Point mutations were detected in 7 (29%) of the 24 carcinomas examined. The K-ras gene was mutated in only 2 samples (8%): a GGC-to-ATC mutation at codon 13 in an adenocarcinoma and a GGC-to-GTC transversion mutation at codon 13 in a mucoepidermoid carcinoma. Five (21%) harbored H-ras mutations: 4 contained a GGC-to-GTC transversion mutation at codon 12 and 1 had 2 distinct mutations, the same G-to-T at codon 12 as was shown in the other cases and a GGT-to-GGA heterozygous mutation at codon 13. All the H-ras mutations were in the group of mucoepidermoid carcinoma lesions (45%; 5/11). CONCLUSION: Our data suggest that K-ras gene alteration is probably not an important factor in the oncogenesis of human salivary gland tumors. However, mutational activation of the H-ras gene appears to play a role in the development and/or progression of salivary gland mucoepidermoid carcinomas.     

Ras gene activation in malignant cells of human ovarian carcinoma peritoneal fluids

In this study, we showed, for the first time, the pattern of point mutations at codon 12 of the K-ras, H-ras and N-ras genes, using polymerase chain reaction and restriction fragment length polymorphism analysis in 47 malignant cytologic specimens of ovarian adenocarcinoma peritoneal fluids. Forty-seven % of the samples were found to carry a point mutation at codon 12 of K-ras gene. Also, 21 cystadenoma peritoneal fluids were used as control specimens for the detection of ras mutations. Fourteen % of these samples were found to carry a point mutation at codon 12 of the K-ras gene. The prevalence of K-ras gene mutations were statistically correlated with FIGO and surgical stage of the malignant specimens. Our data demonstrates that the K-ras gene mutations are mainly affected (47%) in the malignant cells of the peritoneal washings or ascites of women with ovarian adenocarcinomas and may have value for the early diagnosis and monitoring of these neoplasms.     

Lung cancer and past occupational exposure to asbestos. Role of p53 and K-ras mutations

Studies on somatic mutations in lung cancers associated with cigarette smoking and asbestos exposure are few. We investigated prevalence of mutations in the p53 and K-ras genes in lung tumors from smokers with and without asbestos exposure at work. For K-ras mutations, the study was an extension of an earlier analysis. Nearly all of the 105 consecutive patients examined were smokers and had non-small-cell carcinoma of the lung with squamous-cell carcinoma or adenocarcinoma histology. Exposure to asbestos was estimated by pulmonary fiber counts and occupational histories. A pulmonary burden of >/= 1 x 10(6) asbestos fibers per gram of lung tissue, indicating work-related exposure, was found in 32% of the patients for whom fiber-analysis data were available (33 of 102 patients, all men). The statistical analysis showed pulmonary fiber count as the only significant predictor of adenocarcinoma histology, in contrast to squamous-cell carcinoma (smoking-adjusted odds ratio [OR] 3.0, 95% confidence interval [CI] 1.1 to 8.5). The frequency of p53 mutations was 39% (13 of 33) among the asbestos-exposed cases, as compared with 54% (29 of 54) among the nonexposed cases; the difference was not significant, however. In male ever-smokers, a long duration of smoking was associated with p53 mutation (OR 3.2, 95% CI 1.2 to 8.8). In adenocarcinoma, p53 mutations were less prevalent (10 of 30, 33%) as compared with squamous-cell carcinoma (28 of 46, 61%; P = 0.02), whereas a strong and significant association was found between adenocarcinoma and K-ras mutation (OR 37, 95% CI 5.8 to 232, adjusted for smoking and asbestos exposure). Asbestos exposure alone was not significantly associated with increased occurrence of K-ras mutations. In conclusion, the results may primarily reflect the observed excess of adenocarcinoma in the asbestos- exposed patients, and hence the decrease in p53 mutations and increase in K-ras mutations.     

K-ras基因突变与结直肠癌生物学行为的关系

目的: 观察结直肠癌组织中k-ras基因突变情况,探讨k-ras基因突变与结直肠癌生物学行为的关系。方法: 采用实时荧光定量PCR法检测123例结直肠癌组织中k-ras基因1号外显子12、13密码子突变情况,结合其临床病理资料分析。结果: 123例结直肠癌组织中k-ras基因突变者53例(40.8%),其中12密码子突变42例(34.1%),13密码子突变者11例(8.9%)。基因突变率与肿瘤大小、肿瘤侵润深度、分化程度无明显相关性,与淋巴结转移、肝脏转移及TNM分期有相关性（P<0.05）。淋巴结转移多者k-ras基因突变率高,有肝脏转移者基因突变率高,TNM分期越晚基因突变率越高。结论: K-ras基因突变可能在结直肠癌的发生、发展中起重要作用,而且与淋巴结转移和肝脏转移有密切相关,可作为判断结直肠癌恶性程度的一个分子生物学指标。     

Genetic alterations in K-ras and p53 cancer genes in lung neoplasms from Swiss (CD-1) male mice exposed transplacentally to AZT

A transplacental carcinogenicity study was conducted by exposing pregnant Swiss (CD-1) mice to 0, 50, 100, 200, or 300 mg of 3'-azido-3'-deoxythymidine (AZT)/kg bw/day, through a 18 to 19-day gestation [National Toxicology Program, NIH Pub. No. 04-4458, 2004]. The incidences of alveolar/bronchiolar adenomas and carcinomas, in the 200 and 300 mg/kg male treatment groups, were significantly greater than that of the controls. In the present study, we evaluated the benign and malignant lung neoplasms from this bioassay for point mutations, in the K-ras and p53 cancer genes that are often mutated in human lung tumors. K-ras and p53 mutations were detected by cycle sequencing of polymerase chain reaction-amplified DNA, isolated from formalin-fixed, paraffin-embedded neoplasms. K-ras mutations were detected in 25 of 38 (66%) of the AZT-induced lung tumors, and the predominant mutations were codon 12 G-->T transversions. p53 mutations were detected in 32 of 38 (84%) of the AZT-induced lung tumors, with the predominant mutations being exon 8, codon 285 A-->T transversions, and exon 6, codon 198 T-->A transversions. No K-ras or p53 mutations were detected in five tumors, examined from control mice. The patterns of mutations identified in the lung tumors suggest that incorporation of AZT or its metabolites into DNA, oxidative stress, and genomic instability may be the contributing factors to the mutation profile and development of lung cancer in these mice.     

K-ras mutations are correlated to lymph node metastasis and tumor stage, but not to the growth pattern of colon carcinoma

In colorectal carcinoma, pathological assessment of tumors is essential for determining therapy and prognosis of the disease. Molecular associations of tumor complexity index and genetic alternations can be helpful to understand the tumor progression mechanism. Oncogenic K-ras is one of the major colorectal cancer associated genes, and is mutated in up to 50% of colorectal cancers. In this current study, we correlated tumor complexity index with mutations in K-ras codon 12, 13, and 61 in association with different clinicopathological parameters such as TNM stage, localization, sex, and age. Formalin-fixed paraffin embedded tissue blocks from colon cancer samples was selected from 88 patients diagnosed with adenocarcinoma. Mutations in the K-ras gene were detected using pyrosequencing technique. Tumor complexity index was calculated using immunohistochemically stained images of the tumor outline of the specimens and then analyzing these pictures using Photoshop CS, Fovea Pro, and Image J computer programs. Statistical analysis was performed with SPSS. K-ras mutations were detected in 17 (19.3%) colon cancer samples. Most of the samples were at a lower complexity index. No correlation was observed between K-ras mutations and complexity index. However, K-ras mutations were correlated with regional lymph node metastasis and tumor stages and complexity index with tumor wall penetration. In conclusion, complexity index and K-ras mutations are independent events; however, both correlate with tumor progression and are important in the biologic development of colon carcinoma.     

Detection of K-ras mutations in mucinous pancreatic duct hyperplasia from a patient with a family history of pancreatic carcinoma.

Mutations in the K-ras oncogene and in the p53 tumor suppressor gene are commonly identified in sporadic cases of pancreatic adenocarcinoma. Although these genes might serve as useful markers for early diagnosis of pancreatic carcinoma in patients at risk for the development of this disease, familial pancreatic carcinomas have not been studied for these mutations. We recently had the opportunity to examine a pancreas prophylactically removed from a patient with a strong family history of pancreatic carcinoma. This gave us the unique opportunity to study the early events in the development of familial adenocarcinoma of the pancreas. Histopathological examination of the pancreas revealed multifocal papillary and nonpapillary mucinous duct hyperplasia. Seven of these foci were microdissected and analyzed for K-ras and p53 mutations. The K-ras mutations were detected by combined mutant-enriched polymerase chain reaction-restriction fragment length polymorphism analysis and characterized further by allele-specific oligonucleotide hybridization. Five of the seven duct lesions harbored activating point mutations in codon 12 of K-ras; a G to A transition was found in four and a G to C transversion in one. In contrast, these lesions did not harbor detectable p53 mutations as determined by denaturing gradient gel electrophoresis of exons 5 to 8, nor was there overexpression of the p53 protein as determined by immunohistochemistry. These findings suggest that mutations in K-ras represent an early event in the pathogenesis of pancreatic carcinoma. In addition, monitoring of patients with a strong family history of pancreatic carcinoma for K-ras mutations may identify patients at risk for the development of invasive carcinoma.