Clostridium perfringens α-toxin interaction with red cells and model membranes.

The effects of Clostridium perfringens α-toxin on host cells have previously been studied extensively but the biophysical processes associated with toxicity are poorly understood. The work reported here shows that the initial interaction between the toxin and lipid membrane leads to measurable changes in the physical properties and morphology of the membrane. A Langmuir monolayer technique was used to assess the response of different lipid species to toxin. Sphingomyelin and unsaturated phosphatidylcholine showed the highest susceptibility to toxin lypolitic action, with a two stage response to the toxin (an initial, rapid hydrolysis stage followed by the insertion and/or reorganisation of material in the monolayer). Fluorescence confocal microscopy on unsaturated phosphatidylcholine vesicles shows that the toxin initially aggregates at discrete sites followed by the formation of localised "droplets" accumulating the hydrolysis products. This process is accompanied by local increases in the membrane dipole potential by about 50 (±42) mV. In contrast, red blood cells incubated with the toxin suffered a decrease of the membrane dipole potential by 50 (±40) mV in areas of high toxin activity (equivalent to a change in electric field strength of 10(7) V m(-1)) which is sufficient to affect the functioning of the cell membrane. Changes in erythrocyte morphology caused by the toxin are presented, and the early stages of interaction between toxin and membrane are characterised using thermal shape fluctuation analysis of red cells which revealed two distinct regimes of membrane-toxin interaction.Royal Society University Research Fellowshi

Reduced expression of the polymeric immunoglobulin receptor in pancreatic and periampullary adenocarcinoma signifies tumour progression and poor prognosis

The polymeric immunoglobulin receptor (pIgR) is a key component of the mucosal immune system that mediates epithelial transcytosis of immunoglobulins. High pIgR expression has been reported to correlate with a less aggressive tumour phenotype and an improved prognosis in several human cancer types. Here, we examined the expression and prognostic significance of pIgR in pancreatic and periampullary adenocarcinoma. The study cohort encompasses a consecutive series of 175 patients surgically treated with pancreaticoduodenectomy for pancreatic and periampullary adenocarcinoma in Malmö and Lund University Hospitals, Sweden, between 2001-2011. Tissue microarrays were constructed from primary tumours (n = 175) and paired lymph node metastases (n = 105). A multiplied score was calculated from the fraction and intensity of pIgR staining. Classification and regression tree analysis was used to select the prognostic cut-off. Unadjusted and adjusted hazard ratios (HR) for death and recurrence within 5 years were calculated. pIgR expression could be evaluated in 172/175 (98.3%) primary tumours and in 96/105 (91.4%) lymph node metastases. pIgR expression was significantly down-regulated in lymph node metastases as compared with primary tumours (p = 0.018). Low pIgR expression was significantly associated with poor differentiation grade (p < 0.001), perineural growth (p = 0.027), lymphatic invasion (p = 0.016), vascular invasion (p = 0.033) and infiltration of the peripancreatic fat (p = 0.039). In the entire cohort, low pIgR expression was significantly associated with an impaired 5-year survival (HR = 2.99, 95% confidence interval (CI) 1.71-5.25) and early recurrence (HR = 2.89, 95% CI 1.67-4.98). This association remained significant for survival after adjustment for conventional clinicopathological factors, tumour origin and adjuvant treatment (HR = 1.98, 95% CI 1.10-3.57). These results demonstrate, for the first time, that high tumour-specific pIgR expression signifies a more favourable tumour phenotype and that low expression independently predicts a shorter survival in patients with pancreatic and periampullary cancer. The mechanistic basis for the putative tumour suppressing properties of pIgR in these cancers merits further study

Detection of mismatch repair gene germline mutation carrier among Chinese population with colorectal cancer

<p>Abstract</p> <p>Background</p> <p>Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant syndrome. The National Cancer Institute (NCI) has recommended the Revised Bethesda guidelines for screening HNPCC. There has been a great deal of research on the value of these tests in other countries. However, literature about the Chinese population is scarce. Our objective is to detect and study microsatellite instability (MSI) and mismatch repair (MMR) gene germline mutation carriers among a Chinese population with colorectal cancer.</p> <p>Methods</p> <p>In 146 prospectively recruited consecutive patients with clinically proven colorectal cancer, MSI carriers were identified by analysis of tumor tissue using multiplex fluorescence polymerase chain reaction (PCR) using the NCI recommended panel and classified into microsatellite instability-low (MSI-L), microsatellite instability-high (MSI-H) and microsatellite stable (MSS) groups. Immunohistochemical staining for MSH2, MSH6 and MLH1 on tissue microarrays (TMAs) was performed, and methylation of the MLH1 promoter was analyzed by quantitative methylation specific PCR (MSP). Germline mutation analysis of blood samples was performed for MSH2, MSH6 and MLH1 genes.</p> <p>Results</p> <p>Thirty-four out of the 146 colorectal cancers (CRCs, 23.2%) were MSI, including 19 MSI-H CRCs and 15 MSI-L CRCS. Negative staining for MSH2 was found in 8 CRCs, negative staining for MSH6 was found in 6 CRCs. One MSI-H CRC was negative for both MSH6 and MSH2. Seventeen CRCs stained negatively for MLH1. MLH1 promoter methylation was determined in 34 MSI CRCs. Hypermethylation of the MLH1 promoter occurred in 14 (73.7%) out of 19 MSI-H CRCs and 5 (33.3%) out of 15 MSI-L CRCs. Among the 34 MSI carriers and one MSS CRC with MLH1 negative staining, 8 had a MMR gene germline mutation, which accounted for 23.5% of all MSI colorectal cancers and 5.5% of all the colorectal cancers. Five patients harbored MSH2 germline mutations, and three patients harbored MSH6 germline mutations. None of the patients had an MLH1 mutation. Mutations were commonly located in exon 7 and 12 of MSH2 and exon 5 of MSH6. Right colonic lesions and mucinous carcinoma were not common in MSI carriers.</p> <p>Conclusion</p> <p>Our data may imply that the characteristics of HNPCC in the Chinese population are probably different from those of Western countries. Application of NCI recommended criteria may not be effective enough to identify Chinese HNPCC families. Further studies are necessary to echo or refute our results so as to make the NCI recommendation more universally applicable.</p

The revised Bethesda guidelines: extent of utilization in a university hospital medical center with a cancer genetics program

<p>Abstract</p> <p>Background</p> <p>In 1996, the National Cancer Institute hosted an international workshop to develop criteria to identify patients with colorectal cancer who should be offered microsatellite instability (MSI) testing due to an increased risk for Hereditary Nonpolyposis Colorectal Cancer (HNPCC). These criteria were further modified in 2004 and became known as the revised Bethesda Guidelines. Our study aimed to retrospectively evaluate the percentage of patients diagnosed with HNPCC tumors in 2004 who met revised Bethesda criteria for MSI testing, who were referred for genetic counseling within our institution.</p> <p>Methods</p> <p>All HNPCC tumors diagnosed in 2004 were identified by accessing CoPath, an internal database. Both the Tumor Registry and patients' electronic medical records were accessed to collect all relevant family history information. The list of patients who met at least one of the revised Bethesda criteria, who were candidates for MSI testing, was then cross-referenced with the database of patients referred for genetic counseling within our institution.</p> <p>Results</p> <p>A total of 380 HNPCC-associated tumors were diagnosed at our institution during 2004 of which 41 (10.7%) met at least one of the revised Bethesda criteria. Eight (19.5%) of these patients were referred for cancer genetic counseling of which 2 (25%) were seen by a genetics professional. Ultimately, only 4.9% of patients eligible for MSI testing in 2004 were seen for genetic counseling.</p> <p>Conclusion</p> <p>This retrospective study identified a number of barriers, both internal and external, which hindered the identification of individuals with HNPCC, thus limiting the ability to appropriately manage these high risk families.</p