Absence of K-ras mutations in the pancreatic parenchyma of patients with chronic pancreatitis

Pancreatic Cancer-Related Mutational Burden Is Not Increased in a Patient Cohort With Clinically Severe Chronic Pancreatitis

INTRODUCTION

Chronic pancreatitis is associated with an increased risk of developing pancreatic cancer, and patients with inherited forms of pancreatitis are at greatest risk. We investigated whether clinical severity of pancreatitis could also be an indicator of cancer risk independent of etiology by performing targeted DNA sequencing to assess the mutational burden in 55 cancer-associated genes.

METHODS

Using picodroplet digital polymerase chain reaction and next-generation sequencing, we reported the genomic profiles of pancreases from severe clinical cases of chronic pancreatitis that necessitated palliative total pancreatectomy with islet autotransplantation.

RESULTS

We assessed 57 tissue samples from 39 patients with genetic and idiopathic etiologies and found that despite the clinical severity of disease, there was no corresponding increase in mutational burden. The average allele frequency of somatic variants was 1.19% (range 1.00%-5.97%), and distinct regions from the same patient displayed genomic heterogeneity, suggesting that these variants are subclonal. Few oncogenic KRAS mutations were discovered (7% of all samples), although we detected evidence of frequent cancer-related variants in other genes such as TP53, CDKN2A, and SMAD4. Of note, tissue samples with oncogenic KRAS mutations and samples from patients with PRSS1 mutations harbored an increased total number of somatic variants, suggesting that these patients may have increased genomic instability and could be at an increased risk of developing pancreatic cancer.

DISCUSSION

Overall, we showed that even in those patients with chronic pancreatitis severe enough to warrant total pancreatectomy with islet autotransplantation, pancreatic cancer-related mutational burden is not appreciably increased.

Progression of Chronic Pancreatitis to Pancreatic Cancer: Is There a Role of Gene Mutations as a Screening Tool?

OBJECTIVES

Early detection of pancreatic ductal adenocarcinoma still remains a challenge. Patients with chronic pancreatitis (CP) have a markedly increased risk of pancreatic cancer. Mutations in oncogenes and/or tumor suppressor genes play a role in development of pancreatic ductal adenocarcinoma. This study assessed mutations in KRAS and p53 gene in blood as a screening tool for malignant transformation in CP patients.

METHODS

This was a cohort, single-center study including 294 CP patients. DNA was isolated from plasma of CP patients, and KRAS mutations were identified using polymerase chain reaction-restriction fragment length polymorphism. Patients with positive KRAS mutation were screened for malignancy using positron emission tomography or endoscopic ultrasound. Mutations in p53 gene were analyzed by sequencing. Tissue samples from CP and pancreatic cancer patients were also tested for mutations in KRAS and p53 genes.

RESULTS

The plasma samples of 64 CP patients were positive for KRAS mutation, and 4 had mutation in p53 gene also. No patient positive for KRAS mutation and/or p53 mutation was found to have malignant transformation.

CONCLUSION

Detection of KRAS or p53 mutation in plasma is not an effective screening tool for pancreatic cancer because accumulation of multiple mutations is required for malignant transformation in the pancreas.

EGFR and KRAS mutational analysis and their correlation to survival in pancreatic and periampullary cancer

OBJECTIVES

Pancreatic and periampullary cancers have a high incidence of activating KRAS mutations. The aim of this study was to determine the incidence of KRAS and EGFR mutations in pancreatic and periampullary cancers and their relationship with survival.

METHODS

One hundred patients undergoing pancreaticoduodenectomy or pancreatic biopsy for cancer were recruited. Samples of formalin-fixed paraffin-embedded or fresh pancreatic tissue were obtained. EGFR was analyzed by DNA sequencing of exons 18 to 21. KRAS was analyzed by pyrosequencing of codons 12, 13, and 61.

RESULTS

EGFR mutations were found in 2 (2.3%) of 88 assessable cases. One in exon 18 (c.1966C>T, p.Q710X) and 1 in exon 19 (c.2066A>G, p.E734G). A synonymous single-nucleotide polymorphism in exon 20 (c.2361G>A, p.Q787) was identified in 57 (67.8%) of 84 patients studied. Twenty-eight (41.2%) of 68 cases harbored a point mutation in KRAS codon 12 (26 cases) and codon 61 (2 cases). The overall median survival was 308 days (range, 7-2623 days). The presence of KRAS point mutations did not significantly alter median survival time (22.8 vs 28.1 months, P = 0.88).

CONCLUSIONS

EGFR somatic mutations are rare in pancreatobiliary malignancies. KRAS mutations are less common than previous reports and do not correlate with survival.

Comprehensive genomic analysis of a BRCA2 deficient human pancreatic cancer

Capan-1 is a well-characterised BRCA2-deficient human cell line isolated from a liver metastasis of a pancreatic adenocarcinoma. Here we report a genome-wide assessment of structural variations and high-depth exome characterization of single nucleotide variants and small insertion/deletions in Capan-1. To identify potential somatic and tumour-associated variations in the absence of a matched-normal cell line, we devised a novel method based on the analysis of HapMap samples. We demonstrate that Capan-1 has one of the most rearranged genomes sequenced to date. Furthermore, small insertions and deletions are detected more frequently in the context of short sequence repeats than in other genomes. We also identify a number of novel mutations that may represent genetic changes that have contributed to tumour progression. These data provide insight into the genomic effects of loss of BRCA2 function.

Ras activity in acinar cells links chronic pancreatitis and pancreatic cancer

The relationship between chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDAC) is unclear. CP is a risk factor for PDAC, CP is found within the vicinity of PDAC, and both share many similar genetic alterations. However, it has been long thought that PDAC arises only from duct cells. However, we have recently found that excessive activity within the Ras signaling pathway can lead to acinar cell death or metaplasia and is associated with the development of fibrosis resembling CP and the development of PDAC from acinar cells through the full complement of preneoplastic (pancreatic intraepithelial neoplasia) lesions. Therefore, it is time to reevaluate the relationship between CP and PDAC. We proposed a new model in which Ras activity is the direct link between these 2 diseases. Here we will briefly review the shared properties between CP and PDAC and describe the new model.

Clinical significance of K-ras and c-erbB-2 mutations in pancreatic adenocarcinoma and chronic pancreatitis

BACKGROUND

The differentiation of chronic pancreatitis (CP) from pancreatic adenocarcinoma (PA) remains the great challenge for clinicians. The purpose of this study was to compare the prevalence of K-ras and c-erbB-2 mutations in PA and CP in order to evaluate their usefulness in differential diagnosis of those diseases.

METHODS

The study included 49 patients who underwent Whipple resection or distal pancreatectomy for pancreatic adenocarcinoma (26 subjects) or chronic pancreatitis (23 subjects). DNA from pancreatic tissue was analyzed for K-ras codon 12 and c-erbB-2 mutations with PCR amplifications.

RESULTS

The K-ras gene mutation has been shown in 20 (76.9%) PA cases and in 8 (34.8%) CP cases (p<0.01). Prevalence of c-erbB-2 amplification in patients with PA was 17 (65.3%), which was not different from CP, 16 (56.5%) (p=0.58). There was a significant correlation between K-ras mutation and lymph node metastases (p=0.025) as well as between K-ras mutation and G3 tumor differentiation (p=0.037). Overall median survival in patients with PA was 9.5 mo. There was no relationship between presence of K-ras (p=0.58) or c-erbB-2 (p=0.17) mutation and survival time in PA patients.

CONCLUSION

Those results may indicate that both K-ras and c-erbB-2 play a role in pancreatic carcinogenesis, however only K-ras may provide an additional tool in differential diagnosis of CP and PC.

Clinical significance of K-ras and c-erbB-2 mutations in pancreatic adenocarcinoma and chronic pancreatitis

BACKGROUND

The differentiation of chronic pancreatitis (CP) from pancreatic adenocarcinoma (PA) remains the great challenge for clinicians. The purpose of this study was to compare the prevalence of K-ras and c-erbB-2 mutations in PA and CP in order to evaluate their usefulness in differential diagnosis of those diseases.

METHODS

The study included 49 patients who underwent Whipple resection or distal pancreatectomy for pancreatic adenocarcinoma (26 subjects) or chronic pancreatitis (23 subjects). DNA from pancreatic tissue was analyzed for K-ras codon 12 and c-erbB-2 mutations with PCR amplifications.

RESULTS

The K-ras gene mutation has been shown in 20 (76.9%) PA cases and in 8 (34.8%) CP cases (p<0.01). Prevalence of c-erbB-2 amplification in patients with PA was 17 (65.3%), which was not different from CP, 16 (56.5%) (p=0.58). There was a significant correlation between K-ras mutation and lymph node metastases (p=0.025) as well as between K-ras mutation and G3 tumor differentiation (p=0.037). Overall median survival in patients with PA was 9.5 mo. There was no relationship between presence of K-ras (p=0.58) or c-erbB-2 (p=0.17) mutation and survival time in PA patients.

CONCLUSION

Those results may indicate that both K-ras and c-erbB-2 play a role in pancreatic carcinogenesis, however only K-ras may provide an additional tool in differential diagnosis of CP and PC.

Vascular endothelial growth factor-trap suppresses tumorigenicity of multiple pancreatic cancer cell lines

PURPOSE

Vascular endothelial growth factor A (VEGF-A) is a potent angiogenic agent that binds to two high affinity VEGF receptors (VEGFRs), a process facilitated by the low affinity neuropilin receptors. Although VEGF-A is overexpressed in pancreatic ductal adenocarcinoma, it is not known whether the in vivo growth of multiple pancreatic cancer cells can be efficiently blocked by VEGF-A sequestration.

EXPERIMENTAL DESIGN

Four human pancreatic cancer cell lines were grown s.c. in athymic nude mice. One cell line also was used to generate an orthotopic model of metastatic pancreatic cancer. The consequences of VEGF-A sequestration on tumor growth and metastasis were examined by injecting the mice with a soluble VEGFR chimer (VEGF-Trap) that binds VEGF-A with high affinity.

RESULTS

VEGF-Trap, initiated 2 days after tumor cell inoculation, suppressed the s.c. growth of four pancreatic cancer cell lines and markedly decreased tumor microvessel density. Analysis of RNA from tumors generated with T3M4 cells revealed that VEGF-Trap decreased the expression of VEGFR-1 and neuropilin-1 and -2. VEGF-Trap, initiated 3 weeks after tumor implantation, also attenuated intrapancreatic tumor growth and metastasis in an orthotopic model using PANC-1 cells.

CONCLUSIONS

VEGF-Trap is a potent suppressor of pancreatic tumor growth and metastasis and also may act to attenuate neuropilin-1 and -2 and VEGFR-1 expression. Therefore, VEGF-Trap may represent an exceedingly useful therapeutic modality for pancreatic ductal adenocarcinoma.

Pancreatic cancer after surgery for chronic pancreatitis

BACKGROUND

Chronic pancreatitis is known to be a risk factor for pancreatic cancer.

AIMS

To identify patients who were diagnosed with pancreatic cancer after undergoing surgery for histologically documented chronic pancreatitis.

PATIENTS/METHODS

Records of 484 consecutive patients who underwent surgery for chronic pancreatitis from 1976 to 1997 were reviewed.

RESULTS

Pancreatic cancer was diagnosed after a mean of 3.4 years (range: 2 months-1 years) in 14 patients (2.9%). In four patients, pancreatic cancer became evident within 12 months of surgery for chronic pancreatitis, suggesting cancer was present at the original surgery. Cancer presented with recurrent or persistent pain, jaundice, and/or weight loss. Pancreatic resection was possible in eight patients, but in the others, the cancer was inoperable. There was one long-term survivor (alive 14 years postoperatively), but for theothers mean survival was 10 months (16 months after resection vs. 4 months for inoperable cancer).

CONCLUSION

Pancreatic malignancy should be suspected in patients who have had surgery for chronic pancreatitis when symptoms (such as recurrent pain, jaundice, weight loss, or anorexia) recur. Attempts at curative pancreatic resection are indicated and can offer palliation and the potential for a cure.

Detection of oncogenes in chronic pancreatitis

BACKGROUND

The pathogenesis of chronic pancreatitis (CP) remains poorly understood. Recently, molecular biology has identified the genetic background for many patients with hereditary CP. In addition, a number of studies have focused on the detection of proto-oncogenes and tumour suppressor gene mutations in the pathogenesis of CP. So far, the use of these mutations (with the exception of mutations causing hereditary CP), as diagnostic and prognostic markers is still controversial.

DISCUSSION

It is well known that the risk of pancreatic cancer in patients with CP, especially the hereditary form, is high. At present, there is insufficient evidence to show a clear relationship between the development of pancreatic cancer and certain mutations. New biotechnological methods, such as DNA array expression analysis, expand our knowledge of the molecular pathogenesis of this disease and may help to develop specific diagnostic, prognostic and therapeutic tools. However, until long-term studies examine the safety and efficacy of certain genetic markers, long-term follow-up of patients with CP who harbour mutations is needed.

p53 and K-ras mutations in pancreatic juice samples from patients with chronic pancreatitis

BACKGROUND

Mutations in p53 and ras genes are frequent in pancreatic carcinoma. Several ras mutations are consistently detected in the pancreatic juice from patients with chronic pancreatitis. The p53 gene mutations have been detected occasionally in chronic pancreatitis tissue. It was the aim of this study to evaluate the presence and clinical significance of p53 and ras mutations in clinical pancreatic juice samples from patients with chronic pancreatitis.

METHODS

Pancreatic juice was obtained from 66 patients with chronic pancreatitis and no evidence of pancreatic carcinoma (51 men, 15 women; age 17-86 years [mean 49.6 +/- 12.9]). Patients were followed prospectively for 26 +/- 3 (4-54) months. Detection of p53 gene mutations was by temperature gradient gel electrophoresis (TGGE) and single strand conformation polymorphism (SSCP) for exons 5-8. Analysis of ras mutations was performed by SSCP/polymerase chain reaction, restriction fragment length polymorphism/polymerase chain reaction. All mutations were confirmed by sequencing.

RESULTS

Five of 66 (7.5%) pancreatic juice samples contained p53 mutations, and ras mutations were detected in 6 cases (9%). Cytology was negative in all cases. No pancreatic carcinoma developed during follow-up and neither cancer cells nor preneoplastic lesions could be detected histologically in resected specimens. Although no correlation between p53 mutations and duration of pancreatitis or drinking habits was found, K-ras mutations correlated with both heavy smoking and severity of the disease.

CONCLUSION

p53 and ras mutations can be detected in a minority of pancreatic juice samples from patients with chronic pancreatitis in the absence of malignancy.

Surveillance of pre-malignant disease of the pancreatico-biliary system

Technical advancements in ultrasonography, contrast-enhanced computed tomography and magnetic resonance imaging, as well as the wider availability of these ultramodern imaging techniques, have resulted in the early detection and a better classification of various asymptomatic and symptomatic pancreatico-biliary lesions. Pre-malignant biliary and pancreatic lesions are rare disorders, and no clear data are available to define their malignant potential. Because of the lack of controlled epidemiological data, the time span for malignant transformation and its frequency cannot be defined in the majority of these lesions. Adenomyomatosis of the gallbladder and gallbladder polyps larger than 10 mm should be treated by cholecystectomy even in asymptomatic patients because of an increased risk of malignant transformation. Chronic cholangitis, primary sclerosing cholangitis and choledochal cysts are also pre-malignant conditions. The timing of surgery, once it is advised for a pre-malignant condition that is still benign, should, however, be individualized to the particular patient situation. In patients with chronic pancreatitis, surgery may be indicated for disease-related complications. In as much as chronic pancreatitis predisposes to a higher risk of pancreatic cancer, any suspicion of malignancy should warrant a surgical exploration. Intraductal papillary tumours and mucin-producing pancreatic tumours are other pre-malignant pancreatic lesions whose malignant potential cannot be precisely determined pre-operatively. They should be resected in situations where there is a high degree of suspicion even without a clear objective diagnosis. In conclusion, pre-malignant hepato-biliary and pancreatic lesions of uncertain pathology should undergo early resection in view of treatment limitations and the dismal prognosis of established cancers. While hepato-biliary and pancreatic surgery is nowadays performed in specialized centres, with a low post-operative morbidity and mortality, it is equally important to understand that observation alone with regular computed tomography or magnetic resonance imaging control can no longer be recommended in the management of these lesions.

Telomerase activity in pure pancreatic juice for the diagnosis of pancreatic cancer may be complementary to K-ras mutation

BACKGROUND

The usefulness of K-ras mutation in pancreatic juice for the diagnosis of pancreatic cancer is questionable. Telomerase is positive in pancreatic cancer but rarely in benign pancreatic diseases. We conducted this study to determine the usefulness of K-ras mutation and telomerase activity in pancreatic juice for the diagnosis of pancreatic cancer.

METHODS

Pancreatic juice collected during endoscopic retrograde cholangiopancreatography was examined in 31 patients: 12 with pancreatic cancer, 11 with chronic pancreatitis, and 8 control patients. The K-ras gene was detected by using the restriction fragment length polymorphism method. Telomerase activity was detected by using the telomeric repeat amplification protocol.

RESULTS

K-ras mutation was positive in 75% (9 of 12) of pancreatic cancers and in 27% (3 of 11) of cases of chronic pancreatitis but in none of the control patients. Telomerase activity was detected in 92% (11 of 12) of pancreatic cancers and in 18% (2 of 11) of cases of chronic pancreatitis. The diagnostic value in pancreatic cancer was comparable between K-ras mutation and telomerase when evaluated separately. However, by combining these 2 methods, the specificity rose to 100%.

CONCLUSIONS

For the diagnosis of pancreatic cancer, telomerase activity in pancreatic juice may possibly be complementary to K-ras mutation because it may decrease the rate of false-positive diagnosis.

Ductal lesions in patients with chronic pancreatitis show K-ras mutations in a frequency similar to that in the normal pancreas and lack nuclear immunoreactivity for p53

BACKGROUND

Chronic pancreatitis (CP) is considered to be a risk factor for the development of pancreatic carcinoma. The detection of K-ras mutations in the duodenal or pancreatic juice has been held to be a reliable tool for its early diagnosis. However, K-ras mutations also occur in hyperplastic ductal epithelium, making it difficult to interpret their role in pancreatic carcinogenesis.

METHODS

The study included 30 resection specimens, 15 from patients with alcoholic CP, and 15 from patients with idiopathic CP. The mean duration of disease was 6.8 years. A total of 429 ductal lesions were classified according to the World Health Organization classification (1996) and microdissected. K-ras analysis was performed by means of polymerase chain reaction (45 cycles), constant denaturing gel electrophoresis, and sequencing. Immunostaining was performed with antibodies against p53, Ki-S5, carcinoembryonic antigen, and two types of mucins.

RESULTS

The 30 specimens demonstrated all types of ductal lesions. Severe cellular atypia was not observed. A total of 429 ductal lesions were analyzed. Approximately 4.4% of the lesions (19 of 429) from 27% of the patients (8 of 30) showed K-ras mutations, but they were unrelated to the duration or type of CP. Immunostaining for mutated p53 protein always was negative. Increased proliferative activity was noted only in patients with papillary hyperplasia. No patient developed pancreatic carcinoma within a follow-up period of at least 3 years.

CONCLUSIONS

Ductal lesions in patients with CP exhibit K-ras mutations without additional indications of neoplastic transformation such as severe dysplasia or mutated p53 protein. Therefore, for diagnostic and therapeutic purposes, the detection of K-ras mutations should be supplemented by the demonstration of additional genetic alterations or clinical signs of malignancy.

Tumor angiogenesis in chronic pancreatitis and pancreatic adenocarcinoma: impact of K-ras mutations

Chronic pancreatitis (CP) is one condition in which epidemiologic studies have demonstrated a definite association with pancreatic adenocarcinoma (PAC). The pathophysiologic and molecular events that either predispose to the development of, or potentiate the growth of, PAC are unknown. Mutation of the codon 12 K-ras gene is one genetic aberration commonly associated with development of PAC. Tumor angiogenesis, or microvascular proliferation of new capillaries, is another pathophysiologic alteration associated with PAC. Although activated ras oncogenes modulate tumor angiogenesis/neovascularization in some tumors, the importance of tumor angiogenesis and the role of K-ras mutation in regulating angiogenesis in CP and PAC are unknown. The aim of this study was to elucidate the relationship between angiogenesis and K-ras mutations in CP and PAC. Tumor angiogenesis and K-ras mutations were evaluated in resected specimens from 25 CP (23 CP plus two CP with PAC) and 16 PAC patients. Tumor angiogenesis was determined using immunohistochemistry of factor VIII-related antigen (FVIIIRAg) and ras mutations were identified by enriched-nested polymerase chain reaction. The mean number of FVIIIRAg-positive blood vessels was significantly (p < 0.005) higher in PAC (23.0 +/- 7.5), CP with a mutant K-ras genome (17.7 +/- 2.8) and CP with a normal K-ras genome (6.5 +/- 3.8), compared to unaffected areas. Codon 12 K-ras mutations were detected in three of 25 CP specimens (12%) and in 15 of 16 PAC specimens (94%). In CP patients with mutant K-ras in their genome, microvessel density was significantly (p < 0.01) elevated, compared to patients with a normal K-ras genome. Statistical analyses (Spearman rank-difference correlation coefficient, Student t test, and chi2 analysis) indicated a significant association between codon 12 K-ras mutations and tumor angiogenesis in both CP and PAC. This study demonstrates a significant association between angiogenesis and K-ras mutation in both PAC and CP. At a minimum, K-ras mutation is associated with the events that increase angiogenesis and it may potentiate or promote tumor angiogenesis.

K-Ras mutations and benign pancreatic disease

This review addresses the history of the ras oncogene, the techniques used to detect molecular alterations in the ras oncogene, and the application of polymerase chain reaction (PCR)-based methods to determine point mutations in clinical samples of patients with pancreatic diseases, namely pancreatic carcinoma and chronic pancreatitis. The frequency of ras mutations in pancreatic carcinoma is high, ranging from 70 to almost 100%. The frequence of ras mutations in chronic pancreatitis, either in pancreatic tissue or pancreatic secretions, vary between 0 and 100%. This wide range in part may be owing to differences in sampling, DNA extraction, or PCR method. The meaning of a k-ras mutation is under debate. Taking into account the positivity of ductal hyperplasias in normal pancreas and ras mutations in normal appearing duct cells, this molecular finding may not mean anything. In contrast, ras mutations are associated with smoking, one acknowledged risk factor for pancreatic carcinoma. The need for large prospective cohort studies is emphasized.

Molecular biology in cytopathology: current applications and future directions

The use of molecular techniques in cytopathology has become an accepted and billable practice for certain applications. Other applications still are in the developmental or experimental stages but may soon be clinically useful. The current study provides a review of these techniques including molecular detection of clonality, in situ hybridization, loss of heterozygosity, and single base mutation detection. A number of new molecular techniques recently have been described that may have a dramatic impact on diagnostic pathology. These techniques, in situ detection of single base mutations and microarray technology, are introduced and discussed in the context of potential applications to cytopathology in the future.

Pancreatic cancer in patients with chronic pancreatitis: a challenge from a surgical perspective

Chronic pancreatitis (CP) is generally considered as a risk factor for pancreatic adenocarcinoma (PAC). However, the cumulative risk differs among the epidemiological studies. In the individual patient, the differential diagnosis between PAC and CP cannot be always resolved preoperatively and even intraoperatively. In those cases, the uncertainty can only be answered with histological studies of the resected specimen after a radical resection, provided that this type of surgery can be performed with a reasonable risk in a surgically fit patient. The type of resection depends on the location of the suspicious mass. For masses in the tail of the pancreas, a distal pancreatectomy is the procedure of choice. For suspicious lesions in the head of the pancreas, a pancreatoduodenectomy (PD) should be performed. The surgeon and the patient should also acknowledge that a radical resection will occasionally be performed for a suspected malignancy only to find that another etiology (i.e. CP) accounts for the suspicious pancreatic mass. In the presence of a strong suspicion for an underlying malignancy in a patient with head dominant CP, PD should probably be preferred over the newer organ-preserving Beger and Frey procedures, since it is an adequate procedure for both CP and PAC.