K-ras gene mutation in the diagnosis of ultrasound guided fine-needle biopsy of pancreatic masses

K-ras mutational status in cytohistological tissue as a molecular marker for the diagnosis of pancreatic cancer: a systematic review and meta-analysis

Background. More clinically meaningful diagnostic tests are needed in pancreatic cancer (PC). K-ras mutations are the most frequently acquired genetic alteration. Methods. Original research articles involving the diagnostic accuracy of K-ras mutation detection in PC were selected. Data were presented as forest plots and summary receiver operating characteristic (SROC) curve analysis was used to summarize the overall test performance. Results. We assessed 19 studies from 16 published articles. The reports were divided into three groups according to the process used to obtain the test material. The summary estimates for detecting K-ras status using an invasive method (fine needle aspiration (FNA), endoscopic retrograde cholangiopancreatography (ERCP), or surgery) were better than cytology: the pooled sensitivity was 77% (95% confidence interval (CI): 74–80%) versus 54% (95% CI: 47–61%); specificity was 88% (95% CI: 85–91%) versus 91% (95% CI: 83–96%); and diagnostic odds ratio (DOR) was 20.26 (11.40–36.03) versus 7.52 (95% CI: 2.80–20.18), respectively. When two procedures were combined, the diagnostic accuracy was markedly improved. Conclusions. The analysis of K-ras mutations in pancreatic tissue has a promising diagnostic significance in PC. Further valuable studies are needed.

Diagnostic accuracy of K-ras mutation for pancreatic carcinoma: a meta-analysis

BACKGROUND

The conventional tests for the diagnosis of early stage pancreatic carcinoma are not acceptable. This meta-analysis is to evaluate the accuracy of K-ras mutation for the diagnosis of pancreatic carcinoma.

DATA SOURCES

A systemic search of all relevant literature was performed in Web of Science, EMBASE, Cochrane Database, and MEDLINE (PubMed as the search engine) prior to June 1, 2011. Thirty-four studies fulfilled the inclusion criteria and data were pooled for analysis.

RESULTS

The pooled estimates for K-ras mutation in diagnosis of pancreatic carcinoma were as follows: sensitivity 0.68 (95% CI: 0.66-0.71), specificity 0.87 (95% CI: 0.85-0.88), positive likelihood ratio 4.54 (95% CI: 3.47-5.94), negative likelihood ratio 0.37 (95% CI: 0.30-0.44) and diagnostic odds ratio 14.90 (95% CI: 10.02-22.15). Summary receiver operating characteristic analysis demonstrated that the maximum joint sensitivity and specificity was 0.79, and the overall area under the curve was 0.86.

CONCLUSIONS

Diagnostic accuracy of K-ras mutation was not superior to that of conventional tests. Therefore, K-ras mutation analysis alone is not recommended for the diagnosis of pancreatic carcinoma.

Clinical impact of K-ras mutation analysis in EUS-guided FNA specimens from pancreatic masses

BACKGROUND

EUS-guided FNA (EUS-FNA) is considered optimal for differentially diagnosing pancreatic masses. However, the sensitivity of EUS-FNA ranges from 65% to 95%, respectively, which requires improvement.

OBJECTIVE

To evaluate clinical impact of K-ras mutation analysis in EUS-FNA specimens from pancreatic masses.

DESIGN

Prospective registration, single-center study.

SETTING

Tertiary referral center.

PATIENTS

This study involved 394 consecutive patients with pancreatic masses (307 pancreatic ductal adenocarcinomas [PDACs], 47 pancreatic inflammatory lesions, and 40 other types of tumors) who underwent EUS-FNA and analysis of K-ras mutations.

INTERVENTION

EUS-FNA, Cycleave polymerase chain reaction.

MAIN OUTCOME MEASUREMENTS

Improvement of the diagnostic accuracy by K-ras mutation analysis; absence of K-ras mutations in non-PDAC masses.

RESULTS

K-ras mutations were detected in 266 of 307 PDAC aspirates (87%) and in 3 of 87 non-PDAC masses (3%). K-ras mutations were detected in 18 of 39 patients (46%) who remained cytohistopathologically undiagnosed. The sensitivity, specificity, positive and negative predictive values, and accuracy of cytohistopathological and K-ras mutation analyses alone were 87%, 100%, 100%, 54%, and 89%, respectively, and, when combined, were 93%, 100%, 100%, 68%, and 94%, respectively. Adding K-ras mutation analysis to standard cytohistopathological assessment increased the sensitivity and accuracy of EUS-FNA by 6% (P < .001) and 5% (P < .001), respectively.

LIMITATIONS

Single-center study.

CONCLUSIONS

K-ras mutation analysis may be helpful in patients with suspected PDAC yet inconclusive EUS-FNA findings. K-ras mutations were extremely rare in pancreatic inflammation and other pancreatic tumors.

How useful is it clinically to analyse the K-ras mutational status for the diagnosis of exocrine pancreatic cancer? A systematic review and meta-analysis

BACKGROUND

More clinically meaningful diagnostic tests are needed in exocrine pancreatic cancer (EPC). K-ras mutations are the most frequently acquired genetic alteration in EPC. We analysed the diagnostic utility of detecting K-ras mutations through a systematic analysis of the literature.

METHODS

We searched PubMed using suitable medical subject headings and text words. Original research articles that evaluated the diagnostic accuracy of detecting K-ras mutations for diagnosis of EPC were selected. Two investigators independently extracted data from each study regarding the methodology used, the methodological quality of the study, the diagnostic accuracy reported and the authors' conclusions about clinical applicability of the test. Combined estimates for the sensitivity and specificity of K-ras were determined using bivariate meta-analysis; heterogeneity was explored using meta-regression.

RESULTS

We assessed 34 studies from 30 published articles. The research reports were prone to numerous methodological biases and often lacked vital information for assessing external validity. The sensitivity of detecting K-ras status ranged from 0% through 100%, and the specificity from 58% through 100%. Diagnostic accuracy was highest when cytohistological samples were used: sensitivity and specificity were 76·5% (66·7-84·2) and 91·8% (87·6-94·1), respectively. Studies conducted in a clinically relevant population observed lower accuracy than case-control designs (68·4% vs. 82·7%).

CONCLUSIONS

Because of the numerous methodological limitations of studies, the utility of analysing K-ras mutations for the diagnosis of EPC remains unknown. Flaws in diagnostic biomarkers with well-established biological properties, as K-ras, become even more relevant when the promises of 'personalized medicine' are pondered.

Clinical validity of detecting K-ras mutations for the diagnosis of exocrine pancreatic cancer: a prospective study in a clinically-relevant spectrum of patients

The diagnostic utility of detecting K-ras mutations for the diagnosis of exocrine pancreatic cancer (EPC) has not been properly studied, and few reports have analysed a clinically relevant spectrum of patients. The objective was to evaluate the clinical validity of detecting K-ras mutations in the diagnosis of EPC in a large sample of clinically relevant patients. We prospectively identified 374 patients in whom one of the following diagnoses was suspected at hospital admission: EPC, chronic pancreatitis, pancreatic cysts, and cancer of the extrahepatic biliary system. Mutations in the K-ras oncogene were analysed by PCR and artificial RFLP in 212 patients. The sensitivity and specificity of the K-ras mutational status for the diagnosis of EPC were 77.7% (95% CI: 69.2-84.8) and 78.0% (68.1-86.0), respectively. The diagnostic accuracy was hardly modified by sex and age. In patients with either mutated K-ras or CEA > 5 ng/ml, the sensitivity and specificity were 81.0% (72.9-87.6) and 62.6% (72.9-87.6), respectively. In patients with mutated K-ras and CEA > 5 ng/ml the sensitivity was markedly reduced. In comparisons with a variety of non-EPC patient groups sensitivity and specificity were both always greater than 75%. In this clinically relevant sample of patients the sensitivity and specificity of K-ras mutations were not sufficiently high for independent diagnostic use. However, it seems premature to rule out the utility of K-ras analysis in conjunction with other genetic and 'omics' technologies.

Loss of heterozygosity of Kras2 gene on 12p12-13 in Chinese colon carcinoma patients

AIM: To study the loss of heterozygosity (LOH) on 12p12-13 in Chinese colon carcinoma patients.

METHODS: DNA was extracted from 10 specimens of cancer tissue, 10 specimens of adjacent tissue and 10 specimens of normal tissue, respectively. LOH of Kras2 gene was analyzed by polymerase chain reaction (PCR) and denaturing polyacrylamide gel electrophoresis using 11 microsatellite markers on 12p-12-13.

RESULTS: LOH of Kras gene was detected at least on one marker of 12p-12-13 in 30% (3/10) of adjacent tissue specimens. The highest frequency of LOH was identified on D12S1034 in 28.57% (2/7) of adjacent tissue specimens. LOH was detected at least on one marker of 12p12-13 in 60% (6/10) of carcinoma tissue specimens, the most frequent LOH was found on D12S1034 and D12S1591 in 42.86% (3/7) of carcinoma tissue specimens. LOH was detected in 30% (3/10) of carcinoma tissue specimens, 30% (3/10) of adjacent tissue specimens, and no signal in 1% (1/0) carcinoma tissue specimen. The occurrence of LOH did not correlate with sex, age, tumor size and lymph node metastasis.

CONCLUSION: Genomic instability may occur on 12p-12-13 of Kras2 gene in the development and progression of colon carcinoma. The high LOH of Kras2 gene may directly influence the transcription and translation of wild type Kras2 gene.

Current diagnosis and treatment of pancreatic cancer in China

In China, morbidity and mortality for pancreatic cancer differs from that in most Western countries. Pancreatic cancer is the sixth leading cause of death from malignant disease in China, with an overall cumulative 5-year survival rate of 1% to 3%. Pancreatic cancer has the highest incidence in Shanghai (7.21/100,000) and the lowest (0.47/100,000) in the Hunan Province. As in the Western world, the main reason for the poor outcome of patients with pancreatic cancer is the late establishment of the diagnosis. Pancreatic cancer is seldom detected in early disease stages, and until now, the process of cancer initiation, progression, and formation of metastasis is not sufficiently understood. In this article, we reviewed recent data on patients in China with pancreatic cancer and obtained the most updated information on the different aspects of oncologic research, including epidemiology, molecular biology, diagnosis, and treatment.

Aberrant expression and mutations of K-ras gene in pancreatic adenocarcinoma and chronic pancreatitis

AIM: To investigate frequency and clinical significance of P21^ras expression and K-ras mutations in pancreatic diseases and to identify their diagnostic values in pancreatic carcinoma.

METHODS: A total of 117 ductal lesions were identified in the available sections from pancreatic resection specimens of patients with pancreatic diseases, comprising 24 pancreatic ductal adenocarcinoma, 19 peritumoral ductal atypical hyperplasia, 58 peritumoral ductal hyperplasia and 19 normal duct at the tumor free resection margin. 24 ductal lesions were gotten from 24 chronic panctratitis. The expression of P21^ras was examined by immunohistochemical method. DNA was extracted. Codon 12 K-ras mutations were examined using the two-step polymerase chain reaction (PCR) combined with restriction enzyme digestion, followed by nonradioisotopic single-strand conformation polymorphism (SSCP) analysis by means of automated DNA sequencing.

RESULTS: The expression level of P21^ras in pancreatic carcinoma and chronic pancreatitis was higher than that of normal pancreatic tissue, but the expression of P21^ras in ductal hyperplasia neighboring pancreatic carcinoma was similar to that in ductal hyperplasia of chronic pancretitis. P21^ras showed a gradual stepwise increase in the frequency of expression ranged from normal pancreatic duct (0%), to hyperplasia duct (36.6%) and to atypical hyperplasia duct (78.9%). The expression level of P21^ras of atypical hyperplasia duct was higher than that of hyperplasia duct (P < 0.01). K-ras mutation rate of the pancreatic carcinoma was 79%, which was significantly higher than that in the chronic pancreatitis (33%) (P < 0.01). It was also found that K-ras mutation rate was gradually increased from normal duct at the tumor free resection margin, peritumoral ductal hyperplasia, peritumoral ductal atypical hyperplasia to pancreatic ductal adenocarcinoma. The mutation pattern of K-ras 12 codon of chronic pancreatitis was GGT→GAT, GGT and CGT, which was identical to that in pancreatic carcinoma.

CONCLUSION: Overexpression of P21^ras and K-ras mutation may play roles in the malignant transformation of pancreatic ductal cell. K-ras mutation only is not specific enough to diagnose pancreatic carcinoma.

Expression of MGMT, hMLH1 and hMSH2 and its clinopathological significance in pancreatic carcinoma tissues

AIM: To study the expression of MGMT, hMLH₁ and hMSH₂ and their clinicopathological significances in the tissues of chronic pancreatitis and pancreatic adenocarcinoma.

METHODS: The expression levels of MGMT, hMLH₁ and hMSH₂ were assayed by immunohistochemical method of avidin-biotin complex on the formalin-fixed and routinely paraffin-embedded sections of surgical resected specimen with chronic pancreatitis (n = 10) and pancreatic carcinoma (n = 51).

RESULTS: The positive rates and the scores of MGMT, hMLH₁ and hMSH₂ were significantly higher in chroinic pancreatitis than those of pancreatic carcinoma (MGMT: 100.0% vs 39.2%,3.8±0.8 vs 1.8±1.4; hMLH1: 100.0% vs 45.1%, 3.8±1.0 vs 1.7±1.6; hMSH2: 90.0% vs 50.9%, 3.5±0.9 vs 1.9±1.7). The positive rates and the scores of MGMT, hMLH₁ and hMSH₂ were significantly higher in well-differentiated adenocarcinomas than those of poorly differentiated adenocarcinomas (P < 0.05 or P < 0.01). The positive rates and the scores of MGMT, hMLH₁ and hMSH₂ were higher in metastasis-free cases than those of ones with metastasis, but no statistic difference was found (P>0.05). There was also no difference among the expression of three proteins and the other clinicopathological characteristics of pancreatic carcinoma.

CONCLUSION: The expression of MGMT, hMLH₁ or hMSH₂ may be related to the carcinogenesis and progression, and have inhibifory effects on the carcinogenesis and progression of pancreatic carcinoma.

Somatic mutation analysis of p53 and ST7 tumor suppressor genes in gastric carcinoma by DHPLC

AIM: To verify the effectiveness of denaturing high-performance liquid chromatography (DHPLC) in detecting somatic mutation of p53 gene in gastric carcinoma tissues. The superiority of this method has been proved in the detection of germline mutations, but it was not very affirmative with respect to somatic mutations in tumor specimens. ST7 gene, a candidate tumor suppressor gene identified recently at human chromosome 7q31.1, was also detected because LOH at this site has also been widely reported in stomach cancer.

METHODS: DNA was extracted from 39 cases of surgical gastric carcinoma specimen and their correspondent normal mucosa. Seven fragments spanning the 11 exons were used to detect the mutation of p53 gene and the four exons reported to have mutations in ST7 gene were amplified by PCR and directly analyzed by DHPLC without mixing with wild-type allele.

RESULTS: In the analysis of p53 gene mutation, 9 aberrant DHPLC chromatographies were found in tumor tissues, while their normal-adjacent counterparts running in parallel showed a normal shape. Subsequent sequencing revealed nine sequence variations, 1 polymorphism and 8 mutations including 3 mutations not reported before. The mutation rate of p53 gene (21%) was consistent with that previously reported. Furthermore, no additional aberrant chromatography was found when wild-type DNA was added into the DNA of other 30 tumor samples that showed normal shapes previously. The positivity of p53 mutations was significantly higher in intestinal-type carcinomas (40%) than that in diffuse-type (8.33%) carcinomas of the stomach. No mutation of ST7 gene was found.

CONCLUSION: DHPLC is a very convenient method for the detection of somatic mutations in gastric carcinoma. The amount of wild type alleles supplied by the non-tumorous cells in gastric tumor specimens is enough to form heteroduplex with mutant alleles for DHPLC detection. ST7 gene may not be the target gene of inactivation at 7q31 site in gastric carcinoma.

Relationship between nuclear morphometry, DNA content and resectability of pancreatic cancer

AIM: To investigate the association of nuclear morphometry and DNA content with resectability of pancreatic cancer.

METHODS: A total of 36 patients with pancreatic adenocarcinoma were divided into resectable group and unresectable group. The nuclear morphometry and DNA contents of tumor cells were analyzed by IBAS autoimagine analyzer from paraffin-embedded materials. Localization size, histological type and grade, and clinical stage of the tumor were evaluated. Factors influencing resectability of pancreatic cancer were investigated using stepwise regression analysis.

RESULTS: Statistical significance was found in nuclear DNA content (integrated optical density, IOD) of tumor cells (1.64 ± 0.41 vs 2.96 ± 0.55), DNA ploidy, ages (46.5 ± 5.3 years vs 58.6 ± 0.7 years) and tumor volumes (298.1 ± 101.5 cm³vs 634.7 ± 512.5 cm³) in both groups (P < 0.05), and no difference was found in the nuclear morphometry (P > 0.05). The rates of diploid/tetraploid and aneuploid were 66.7% and 33.3% in resectable group respectively, and 38.9% and 62.1% in unresectable group, respectively (P < 0.05). IOD (X₁₂), ploidy status (X₁₃) and clinical stage (X₃) were radical resectable indicators with statistical significance. The regression equation for resectability was Y = -9.2053 + 3.5428X₁₂ + 2.5390X₁₃ - 2.3001X₃ (RR = 0.8780, P < 0.01).

CONCLUSION: There is a high correlation between resectability of pancreatic cancers and their DNA contents, DNA ploidy status and clinical stage.