Peritoneal dialysis inevitability results in activation of inflammatory processes and its efficiency is highly variable between patients. An improved method to isolate biomarkers and study pathophysiological mechanisms in peritoneal dialysis effluent (PDE) is expected to be of much benefit for the development of this treatment approach and help with patient management. Extracellular vesicles (EVs) are released as part of normal cellular processes. Their proteome is expected to reflect both type and health of their cell of origin. Although there is a significant interest in using EVs for “liquid biopsies”, little is reported of their presence or composition in plentiful dialysis waste fluids, including peritoneal dialysis effluent (PDE). Here we determined the presence of EVs in PDE and subsequently characterized their proteome. EVs were first isolated from PDE using differential centrifugation, then a further enrichment using size exclusion chromatography (SEC) was performed. The presence of EVs was demonstrated using transmission electron microscopy, and their particle counts were investigated using nanoparticle tracking analysis and dynamic light scattering. Using tandem mass spectrometry, marker proteins from three types of EVs i.e. apoptotic bodies, ectosomes, and exosomes were identified. The proteomic results demonstrated that the isolation of EVs by differential centrifugation helped enrich for over 2,000 proteins normally masked by abundant proteins in PDE such as albumin and SEC markedly further improved the isolation of low abundant proteins. Gene ontology analysis of all identified proteins showed the marked enrichment of exosome and membrane-associated proteins. Over 3,700 proteins were identified in total, including many proteins with known roles in peritoneal pathophysiology. This study demonstrated the prominence of EVs in PDE and their potential value as a source of biomarkers for peritoneal dialysis patients.
In all patients with particle-coated peritoneal dialysis tubing, spent dialysate should be screened for BG and GMI. Manipulation of the TK catheter by squeezing, hard flushing, or even brushing to dislodge black particles should be avoided. Replacement of the TK catheter should be suspended until a cause for the particles is determined.
NA mismatch repair (MMR) is necessary for all organisms in order to maintain DNA integrity. Loss of expression of one of the MMR proteins results in several sporadic and inherited human cancers of various organs such as colon, rectum, stomach, uterus, and ovary. 1 Microsatellite instability (MSI) was shown to be associated with some cancer types, better survival and/or outcome, and reduced likelihood of distant metastases and susceptible to chemotherapy. 2-4 Either immunohistochemical study showing loss of MMR proteins expression or PCR-based assay for microsatellite instability can be used to evaluate the MMR status of cancer tissue. 5 Colorectal cancer (CRC), particularly those occurring in the setting of Lynch syndrome, is the prototype of malignancy with microsatellite instability. MMR status has extensively been studied in CRCs 3,4,6-10 and although deficiency of DNA mismatch repair was reported in 15% of Thai patients with sporadic CRCs, 11 MSI testing is not routinely performed as part of the clinical practice in Thailand. Immunotherapy has played a significant role in cancer treatment and recent clinical studies have suggested that mismatch repair-deficient cancers, regardless of tissue origin, are susceptible to immune-checkpoint inhibitors e.g. PD-1 blockade. 12,13 In May 2017, the US Food and Drug Administration (FDA) granted an accelerated approval to pembrolizumab, an antibody to the PD-1 receptor, as an alternative Abstract RATIONALE: Loss of DNA mismatch repair function has long been known in various malignancies, particularly colorectal cancer. However, microsatellite instability (MSI) testing was rarely requested in Thailand. Recently, the US Food and Drug Administration (FDA) has approved pembrolizumab, an antibody to PD-1 receptor, as an alternative treatment for high MSI (MSI-H) and/or MMR (mismatch repair)-deficient solid tumors. We report our recent observation on MSI testing in Thailand. MATERIALS AND METHODS: Data was collected from Chulalongkorn GenePRO Center, Faculty of Medicine, Chulalongkorn University, during July 2013 and July 2017. MSI testing was performed, using 5 microsatellite markers (BAT-25, BAT-26, D2S123, D5S346 and D17S250). The number, source, and result of samples underwent MSI assay were analyzed. RESULTS: Requests for MSI testing have increased significantly in recent years. The shift started in 2015 when the MMR status was found to predict clinical benefit with the immune checkpoint blockade. There were 118 (75.2%) colorectal, 11 (7%) gastric, and 28 (17.8%) other cancers tested. MSI-H, MSI-L, and microsatellite stable (MSS) tumors were detected in 18 (11.5%), 11 (7%), and 128 (81.5%) patients, respectively. Of the 18 MSI-H cancers; 13 (72.2%), 4 (22.2%), and 1 (5.6%) were colorectal, gastric, and gynecologic malignancy, respectively. BAT25 and BAT26 markers were unstable in all MSI-H tumors. CONCLUSION: We have experienced increasing demand for MSI testing in Thai patients at Chulalongkorn GenePRO Center. Colorectal cancers were most frequently tested, and accounted ...
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