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Biomedical subjects

Markus W Büchler

Publications and source records attributed to Markus W Büchler.

At least 19 recordsLinked to original sources
PubMed2003

Pathogenesis of pain in chronic pancreatitis: ongoing enigma.

The pathogenesis of pain in chronic pancreatitis remains an enigma. The cause of pain is almost certainly multifactorial and may vary at different stages of the disease process. These factors may include the release of excessive oxygen-derived free radicals, tissue hypoxia and acidosis, inflammatory infiltration with influx of pain transmittent substances into damaged nerve ends, and the development of pancreatic ductal and tissue fluid hypertension due to morphological changes of the pancreas. Investigations into the causes of pain have been limited by changes in the dynamics with the progression of the disease process, limitations in studying functional and morphological changes of the pancreas in the clinical setting, and the psychosomatic profile of patients. Many of these patients are addicted to alcohol, and suffer from personality disorders. The difficulty in quantifying pain, which is at best subjective, further compounds the issue, especially when assessing the efficacy of treatment.

Abdominal Pain↗
PubMed2003

Effects of STI571 (gleevec) on pancreatic cancer cell growth.

BACKGROUND: Pancreatic cancer is an aggressive malignancy characterized by low responsiveness to chemotherapy and radiotherapy. This resistance is partly due to the overexpression of several tyrosine kinase receptors and their ligands. STI571 has specific activity in inhibiting c-kit, PDGF and Abl receptor tyrosine kinases and has proven successful in the treatment of CML and GIST patients. Here, we investigated the potential role of STI571 in pancreatic cancer. RESULTS: The GI50 of STI571 as well as the effects of STI571 on growth factor actions in pancreatic cell lines were analyzed using the MTT assay. FACS analysis using Annexin and PI staining was performed to study cell cycle, apoptosis, and cell death. Western blot analysis was carried out to investigate MAP kinase and receptor tyrosine kinase phosphorylation. STI571 inhibited cell proliferation in pancreatic cancer cell lines with GI50 concentrations ranging from 17 to 31.5 microM. EGF, IGF-1, and FGF-2 but not PDGF exerted growth stimulatory effects in pancreatic cancer cell lines. STI571 only partly blocked these effects on cell growth, and did not abrogate growth factor-induced receptor and MAPK phosphorylation. CONCLUSION: Our data demonstrate that STI571 inhibits pancreatic cancer cell growth with high GI50 concentrations through tyrosine-kinase receptor independent pathways. The clinical application of STI571 in pancreatic cancer is therefore rather doubtful.

Antineoplastic Agents↗
PubMed2003

Risk of malignancy in serous cystic neoplasms of the pancreas.

BACKGROUND: In contrast to mucinous cystic neoplasms of the pancreas, which are known to have considerable malignant potential, the serous variant is generally thought to be benign. There are, however, several reports of malignancy in serous cystic neoplasms of the pancreas. AIMS: To assess the risk of malignancy of serous cystic tumors of the pancreas and to investigate specific clinical and histological features. METHODS: Clinical and pathological characteristics of benign and malignant serous cystic neoplasms of the pancreas were investigated by a review of the literature and documented by a case of a serous cystadenocarcinoma and immunohistochemical analysis of a series of serous cystadenomas. Reviewing the literature prevalence, age and sex distribution of serous cystic neoplasms were analyzed. RESULTS: The prevalence of cancer among serous cystic neoplasms reported since 1989 was 3%. Serous cystadenoma of the pancreas present at an earlier age (61 years) than serous cystadenocarcinoma (66 years; p = 0.056) and are symptomatic in the majority of patients. Pathological examination of the primary tumor was not able to distinguish cystadenoma from cystadenocarcinoma in 38% of cases. In 25% the diagnosis of cancer was established only after growth of metachronous metastases. In the present case, nuclear atypia, papillary structures, proliferation marker Ki-67 and p53 protein were increased in the primary tumor and/or metachronous metastasis. CONCLUSION: Serous cystic neoplasms of the pancreas do have malignant potential with a risk of malignancy of 3% and should be surgically treated if the operative risk is acceptable. Routine analysis of genetic and proliferation markers may improve diagnosis of malignancy in these tumors.

Cystadenocarcinoma, Serous↗
PubMed2003

Perspectives of evidence-based surgery.

The assessment of the optimal treatment option based on best current knowledge is called evidence-based medicine (EBM). Considering the cost explosion in public health systems, EBM should also incorporate proper utilization of the restricted economical resources and should enforce quality assurance in medicine. It is imperative that surgeons realize that randomized controlled trials are applicable to the operative specialties in a large scale, and are necessary to provide evidence-based surgery. So far, only 3.4% of all publications in the leading surgical journals are randomized controlled trials. Furthermore, only 44.1% of the published surgical randomized controlled studies compared different surgical procedures, whereas 55.9% of the articles compared medical therapies in surgical patients. Evidence-based surgical therapy is essential for further development of a high- quality surgical standard, which will also provide quality assurance in future surgical care. This article presents the definition of EBM and discusses specific problems involved in the introduction of its principles into the surgical discipline.

Evidence-Based Medicine↗
PubMed2003

Evidence-based surgery in chronic pancreatitis.

BACKGROUND: In the past two decades our knowledge of the pathophysiology and surgical treatment options in chronic pancreatitis has improved substantially. Surgical treatment in chronic pancreatitis has evolved from extending to organ-preserving procedures. DISCUSSION: The classical Whipple resection is no longer a standard procedure in chronic pancreatitis, and is continuously being replaced by operations such as the duodenum-preserving pancreatic head resection and pylorus-preserving Whipple. These procedures allow the preservation of exocrine and endocrine pancreatic function, provides pain relief in up to 90% of patients, and contributes to an improvement in life quality. CONCLUSIONS: In addition to presently available results from randomized controlled trials, new studies comparing available surgical approaches in chronic pancreatitis are needed to determine which procedure is the most effective in the treating chronic pancreatitis.

Chronic Disease↗
PubMed2003

Invasion and metastasis in pancreatic cancer.

Pancreatic cancer remains a challenging disease with an overall cumulative 5-year survival rate below 1%. The process of cancer initiation, progression and metastasis is still not understood well. Invasion and tumor metastasis are closely related and both occur within a tumour-host microecology, where stroma and tumour cells exchange enzymes and cytokines that modify the local extracellular matrix, stimulate cell migration, and promote cell proliferation and tumor cell survival. During the last decade considerable progress has been made in understanding genetic alterations of genes involved in local and systemic tumor growth. The most important changes occur in genes which regulate cell cycle progression, extracellular matrix homeostasis and cell migration. Furthermore, there is growing evidence that epigenetic factors including angiogenesis and lymphangiogenesis may participate in the formation of tumor metastasis. In this review we highlight the most important genetic alterations involved in tumor invasion and metastasis and further outline the role of tumor angiogenesis and lymphangiogenesis in systemic tumor dissemination.

Animals↗
PubMed2003

Intraductal papillary mucinous tumors of the pancreas.

Cystic neoplasms of the exocrine pancreas are a small fraction of pancreatic tumors. Within that group of cystic neoplasms, intraductal papillary mucinous tumors (IPMTs) can be distinguished from mucinous cystic neoplasms, serous cystic neoplasms, and pseudopapillary cystic tumors. Awareness of IPMTs has increased since the World Health Organization classified these tumors as its own group in 1996. Because of their favorable prognosis, an extensive diagnostic workup for IPMTs should be performed in patients presenting with cystic lesions of the pancreas. This workup often leads to the diagnosis and the predominant tumor location and size, although the extent of the ductal changes can only be established by histopathology. Surgical resection is the therapy of choice for IPMTs. The type of resection depends upon the extent of the quantitative and qualitative ductal involvement. Total pancreatectomy is currently the treatment for an IPMT that comprises the entire main duct.

Carcinoma, Pancreatic Ductal↗
PubMed2003

Down-regulation of the dual-specificity phosphatase MKP-1 suppresses tumorigenicity of pancreatic cancer cells.

BACKGROUND & AIMS: In both pancreatic cancer and chronic pancreatitis, there is enhanced expression of mitogenic growth factors and their tyrosine kinase receptors, which have the capacity to activate mitogen-activated protein kinase (MAPK). In view of the important role of MAPK kinase phosphatase (MKP)-1 in the regulation of MAPK activation, the expression and functional role of MKP-1 was analyzed. METHODS: Pancreatic tissues were analyzed by Northern blotting, Western blotting, and immunohistochemistry. Pancreatic cancer cells were transfected with a full-length MKP-1 antisense construct. Growth characteristics and tumorigenicity in vivo and the effects of mitogenic growth factors on cell growth and MAPK activation were determined in transfected and control cells. RESULTS: MKP-1 messenger RNA (mRNA) levels were increased in pancreatic cancer and chronic pancreatitis (CP) tissues. Moderate to strong MKP-1 immunoreactivity was present in the cancer cells, ductal cells of pancreatic intraepithelial neoplasia, and in tubular complexes in CP. Down-regulation of MKP-1 resulted in decreased anchorage-dependent and -independent growth of pancreatic cancer cells, and decreased tumorigenicity in a nude mouse tumor model. MKP-1 down-regulation led to decreased proliferation and sustained MAPK activation in response to mitogens. CONCLUSIONS: Suppression of MKP-1 expression reduces the tumorigenicity of pancreatic cancer cells in vivo, suggesting that MKP-1 contributes to enhanced mitogenic signaling in pancreatic cancer cells.

Adolescent↗
PubMed2003

Distribution of CCK1 and CCK2 receptors in normal and diseased human pancreatic tissue.

BACKGROUND & AIMS: The localization and functional role of cholecystokinin (CCK) receptor proteins in normal and diseased human pancreas, particularly in ductal pancreatic carcinomas, remain unclear. METHODS: Tissue samples of normal human pancreas, chronic pancreatitis, and ductal pancreatic carcinomas were investigated under carefully controlled conditions for expression of CCK1 and CCK2 receptor messenger RNA (mRNA) and proteins using in situ hybridization and in vitro CCK receptor autoradiography by means of subtype-selective analogues. Synaptophysin immunohistochemistry was used concomitantly for optimal identification of islets, nerves, and tumor areas with neuroendocrine features. RESULTS: CCK2 receptor mRNA and proteins were found abundantly in human pancreatic islets in normal pancreas and chronic pancreatitis. CCK1 receptor proteins were found occasionally in small-sized pancreatic nerves, whereas acini expressed a low density of CCK2 receptors in a few cases of chronic pancreatitis. Ductal pancreatic carcinomas rarely expressed CCK receptors; a few receptor-positive tumors, often characterized by neuroendocrine differentiation, expressed the CCK2 receptor at the mRNA or protein level. However, the main source of CCK receptors in the pancreatic tumor samples consisted of CCK2-expressing islets and/or CCK1-expressing nerves rather than neoplastic tissue. CONCLUSIONS: These data indicate that the presence of CCK receptors in human ductal pancreatic tumor samples is mainly due to CCK2 expression in residual pancreatic islets and CCK1 in pancreatic nerves. Pancreatic acini and ductal pancreatic tumor cells very rarely express CCK2 receptors. These observations suggest that CCK analogues may not be of clinical use to target most of these cancers.

Adult↗
PubMed2003

Primary human hepatocytes--a valuable tool for investigation of apoptosis and hepatitis B virus infection.

BACKGROUND/AIMS: Apoptosis is a key event in the pathophysiology of many liver diseases. Primary human hepatocytes (PHH) provide a useful model to study physiological and pathophysiological processes in the liver. Our aim was to optimize PHH cultures to allow studies on induction of apoptosis and of hepatitis B virus (HBV) infection. METHODS: PHH were isolated from human liver tissue by two-step collagenase perfusion. PHH and hepatoma cells were treated with different apoptosis-inducing agents in parallel. PHH cultures were infected with wild type HBV and transduced with HBV genomes using adenoviral vectors. RESULTS: PHH were successfully isolated from 40 different tissue samples with high viability and purity. Perfusion time and seeding density turned out to be critical parameters for optimal cell yield and culture conditions, respectively. Serum addition to the medium reduced viability of PHH. PHH allowed reproducible studies of CD95-dependent and -independent apoptosis. Sensitivity towards CD95-mediated apoptosis was markedly higher than in hepatoma cells. PHH could efficiently be infected with HBV, but infection did neither induce apoptosis nor prevent CD95-induced cell death. CONCLUSIONS: Our data show that PHH provide an excellent tool for the investigation of apoptosis induced by agents like death receptor-ligands and hepatotropic viruses.

Apoptosis↗
PubMed2003

Up-regulation of p75 neurotrophin receptor (p75NTR) is associated with apoptosis in chronic pancreatitis.

Activation of apoptosis in chronic pancreatitis has been demonstrated. The low-affinity neurotrophin receptor p75 (p75NTR) mediates apoptosis in many cell types in vivo and in vitro. The aim of this study was to examine whether p75NTR is involved in the apoptotic process in chronic pancreatitis. The quantity and localization of the receptor was evaluated using northern blot analysis, in situ hybridization, immunohistochemistry, and western blot analysis. Apoptosis was determined by TUNEL assay. By northern blot analysis, p75NTR mRNA levels were increased 40-fold in chronic pancreatitis compared with normal pancreas (P < 0.01). In situ hybridization revealed weak p75NTR mRNA expression in some ductal cells in the normal pancreas. In contrast in chronic pancreatitis moderate p75NTR expression was present in acinar cells next to fibrosis, ductal cells, and cells of ductular structures as well as in some islet cells. Immunostaining of p75NTR in normal pancreas and chronic pancreatitis tissue samples showed a similar intensity and distribution pattern as found by in situ hybridization. Higher p75NTR protein levels could be confirmed by western blot analysis, which revealed an 8.6-fold increase of p75NTR in chronic pancreatitis. TUNEL staining showed, in chronic pancreatitis samples, positivity in some acinar cells next to fibrosis, some ductal cells, and cells of ductular structures. Also some islet cells were positive by TUNEL staining. The presence of p75NTR immunoreactivity was positively correlated (P < 0.05) with the apoptotic index in the exocrine and endocrine pancreas. In conclusion, p75NTR, the low-affinity receptor of neurotrophins which mediates apoptosis, is up-regulated in CP and is involved in the apoptotic process of the exocrine and endocrine pancreas.

Adolescent↗
PubMed2003

Up-regulation, nuclear import, and tumor growth stimulation of the adhesion protein p120 in pancreatic cancer.

BACKGROUND & AIMS: Cell adhesion proteins have been implicated as tumor suppressors because they prevent malignant cells from dissociating their cell contacts. We have studied the role of p120(ctn), a recently discovered member of the cadherin/catenin family, in human pancreatic cancer. METHODS: In 32 resection specimens of pancreatic adenocarcinoma and 10 control samples the expression of p120(ctn) was studied by Northern blot, immunocytochemistry, and immunogold electron microscopy. Patient survival data, tumor grading, and staging were correlated to the experimental results. In PaTu 8889 T pancreatic cancer cells, p120(ctn) expression was suppressed with 21-nucleotide small interfering RNA (siRNA) duplexes and proliferation was determined by bromodeoxyuridine (BrdU) incorporation. RESULTS: In pancreatic cancer p120(ctn) messenger RNA (mRNA) was increased 3- to 4-fold. Although p120(ctn) was localized exclusively at cell contacts in controls it was found in the cytosol and nucleus of pancreatic cancer cells. This redistribution correlated to the degree of tumor dedifferentiation but was independent of tumor stage. The mean survival of patients with predominant membrane localization of p120(ctn) was 24 +/- 7 (SEM) months vs. 9 +/- 2 months for patients with predominant cytoplasmic p120(ctn) expression (P < 0.05). Silencing of p120(ctn) with siRNA duplexes reduced pancreatic cancer cell growth by 40%. CONCLUSIONS: Up-regulation, cytoplasmic redistribution, and nuclear import of p120(ctn) are associated with a more malignant phenotype of pancreatic cancer. This study further represents conclusive evidence for a direct involvement of p120(ctn) in malignant tumor cell proliferation. Both p120(ctn)-defective tumor cell contacts and p120(ctn)-mediated growth signals appear to contribute to the aggressive spread of pancreatic cancer.

Active Transport, Cell Nucleus↗
PubMed2003

Hypoxia-inducible factor 1 regulates vascular endothelial growth factor expression in human pancreatic cancer.

INTRODUCTION: The microenvironment of low oxygen that is present in human pancreatic cancer in vivo may actively influence tumor growth as well as neovascularization. AIMS: To determine whether hypoxia-inducible factor 1 (HIF-1) is specifically activated by hypoxia in vitro in pancreatic cancer cells and correlated these findings with tumor specimens. METHODOLOGY: Hypoxic regulation of vascular endothelial growth factor (VEGF) was studied by northern blot analysis and enzyme-linked immunosorbent assay. Electrophoretic mobility shift assays and western blot analysis were used to demonstrate hypoxic activation of HIF-1. The relationship between HIF-1 and VEGF in human pancreatic cancer specimens was studied by immunohistochemical analysis, northern blot analysis, and in situ hybridization. RESULTS: Studies in vivo of human pancreatic cancer tissue showed co-localization of VEGF mRNA, which is produced in ductal cancer cells, and HIF-1alpha protein, which was detectable in cell nuclei of the same cells. HIF-1alpha mRNA expression was dramatically upregulated (approximately 13-fold) in these specimens as well. In vitro, all pancreatic cancer cell lines increased VEGF production when exposed to low oxygen levels, by highly specific activation of HIF-1 DNA binding activity to the VEGF promoter. Cancer cell lines with high constitutive levels of HIF-1alpha protein were found to produce higher basal levels of VEGF. CONCLUSION: We conclude that HIF-1 is the regulatory link between tumor hypoxia and VEGF production in pancreatic cancer, thus establishing a biochemical pathway between tumor hypoxia and neoangiogenesis in this highly aggressive neoplasm.

Adenocarcinoma↗
PubMed2003

Cefepime tissue penetration in experimental acute pancreatitis.

INTRODUCTION: Antibiotic treatment represents a cornerstone in the management of severe acute pancreatitis. However, different antibiotic substances are currently used. In this study, we analyzed penetration of cefepime into pancreatic tissue in two models of acute pancreatitis. AIMS AND METHODOLOGY: Following induction of acute pancreatitis, animals were treated with a single intravenous dose of cefepime (0.1 mg/g of body weight). At two different time points, blood and tissue samples were obtained for determination of cefepime concentration and microbiologic analysis. RESULTS: Mean pancreatic tissue concentrations +/- SEM 30 minutes after drug administration were significantly higher in animals with either mild acute pancreatitis (113 +/- 22 mg/kg) or severe acute pancreatitis (75 +/- 22 mg/kg) than in control animals (30 +/- 6 mg/kg) (p < 0.005). The minimal inhibitory concentrations (MIC90) for organisms usually isolated from infected pancreatic necrosis vary between 0.05 and 8 mg/L, which is between nine and 1,500 times lower than the mean peak concentration found in necrotic pancreatic tissue. Seven hours 30 minutes after antibiotic administration, pancreatic cefepime concentrations were still above the MIC90 in 100% and 83% of animals with mild and severe disease, respectively. The infection rate of pancreatic tissue was significantly lower after antibiotic treatment and was similar after imipenem/cilastatin or cefepime treatment. CONCLUSION: Because of its antibacterial coverage and proven tissue penetration in acute pancreatitis, cefepime should be studied in patients with severe acute pancreatitis.

Animals↗
PubMed2003

Impaired insulin action on phosphatidylinositol 3-kinase activity and glucose transport in skeletal muscle of pancreatic cancer patients.

INTRODUCTION: Glucose intolerance or overt diabetes occurs in 80% of patients with pancreatic cancer (PC). This associated metabolic disorder includes peripheral insulin resistance, which may be caused by factors produced by the PC. The mechanism underlying PC-associated insulin resistance has not been clearly defined. AIM: To characterize basal and insulin-stimulated glucose transport, phosphatidylinositol (PI) 3-kinase activity, and glucose transporter 4 (GLUT4) in skeletal muscles of PC patients. METHODOLOGY: Skeletal muscle samples were obtained from the abdominal wall of 17 PC patients during surgery. Control muscles were sampled in the same way from 11 donors undergoing abdominal surgery for benign diseases. PI 3-kinase activity, glucose transport, and GLUT4 were assessed in vitro in these muscles. RESULTS: In the presence of physiologic concentrations of insulin, glucose transport and PI 3-kinase activity were significantly decreased in the PC group compared with controls. At supraphysiologic insulin concentrations, glucose transport was significantly decreased but PI 3-kinase activity was normalized. In the absence of insulin, these parameters were not significantly different between PC and control groups. Muscle GLUT4 contents were similar between PC and control groups. CONCLUSION: Defects in insulin-mediated PI 3-kinase activity and glucose transport contribute to the insulin resistance in patients with PC.

3-O-Methylglucose↗
PubMed2003

Prevention of metastatic pancreatic cancer growth in vivo by induction of apoptosis with genistein, a naturally occurring isoflavonoid.

INTRODUCTION: The critical need for novel therapeutic approaches to pancreatic cancer treatment is clear. Genistein, a naturally occurring isoflavonoid, is active against certain solid malignancies, but its effect on pancreatic cancer is unknown. AIMS: To investigate the bioactivity of genistein in experimental pancreatic cancer in vitro and in vivo. METHODOLOGY: The effect of intraperitoneal genistein administration on local tumor growth and metastatic disease was determined in an orthotopic nude mouse model. Apoptosis in tumor specimens was determined by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) technique. In vitro, the effect of genistein on cell growth was assessed by cell count and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) colorimetric assay. Apoptosis was determined in vitro by DNA laddering and annexin-V. Caspase-3 and nuclear factor-kappaB activity were measured following genistein treatment. RESULTS: In vivo, genistein significantly improved survival, almost completely inhibited metastasis, and increased apoptosis in an orthotopic model of pancreatic cancer. In vitro genistein treatment resulted in apoptosis in all pancreatic cancer cell lines tested, and this appeared to be mediated by activation of caspase-3. CONCLUSION: These findings suggest that the antimetastatic effect of genistein treatment in vivo is mediated by induction of apoptosis. Genistein may have a therapeutic benefit for patients with pancreatic cancer, in particular after surgery, to prevent recurrence of metastatic disease.

Animals↗
PubMed2003

Neurokinin-1 receptor expression and its potential effects on tumor growth in human pancreatic cancer.

The neurokinin-1 receptor (NK-1R) and its ligand substance P (SP) are involved in the pathogenesis of certain neural tumors. Because nerves are significantly altered in pancreatic cancer, evidence for alteration of this pathway in human pancreatic cancer was sought. Expression of NK-1R was analyzed by real-time quantitative RT-PCR, in situ hybridization, immunohistochemistry, and Western blot analysis in normal human pancreatic and pancreatic cancer tissue samples and in pancreatic cancer cell lines. Furthermore, the influence of SP analogs and of the NK-1R antagonist MEN 11467 on pancreatic cancer cell growth was analyzed by sulforhodamine B (SRB) assay. By real-time quantitative RT-PCR, NK-1R mRNA was increased 36.7-fold (p < 0.001) in human pancreatic cancer samples compared with normal controls. Enhanced NK-1R expression levels were not related to tumor grade but were associated with advanced tumor stage and poorer prognosis. By in situ hybridization and immunohistochemistry, NK-1R mRNA and immunoreactivity were only occasionally weakly present in acinar and ductal cells in the normal pancreas. In contrast, moderate to strong NK-1R mRNA signals and immunoreactivity were present in most cancer cells. By Western blot analysis, NK-1R was increased 26-fold (p < 0.01) in pancreatic cancer samples in comparison to normal controls. NK-1R mRNA was detected in five pancreatic cancer cell lines by real-time quantitative RT-PCR, with the highest levels in CAPAN-1 cells and the lowest in ASPC-1 cells. SP analogs stimulated pancreatic cancer cell growth, depending on the NK-1R expression level, and this effect could be blocked by a selective NK-1R antagonist. These findings illustrate that the NK-1R pathway is activated in human pancreatic cancer and has the potential to contribute to cancer cell growth, thus suggesting the existence of a neuro-cancer cell interaction in vivo.

Blotting, Western↗