1,2,3,4-Tetrafluorobiphenylene: A Prototype Janus-Headed Scaffold for Ambipolar Materials.

The title compound was synthesized by Ullmann cross-coupling in low yield as the first representative of [n]phenylene containing hydrocarbon and fluorocarbon rings. Stille/Suzuki-Miyaura cross-coupling reactions, as well as substitution of fluorine in suitable starting compounds, failed to give the same product. The geometric and electronic structures of the title compound were studied by X-ray diffraction, cyclic voltammetry and density functional theory calculations, together with Hirshfeld surface and reduced density gradient analyses. The crystal structure features head-to-tail π-stacking and other fluorine-related secondary bonding interactions. From the nucleus-independent chemical shifts descriptor, the four-membered ring of the title compound is antiaromatic, and the six-membered rings are aromatic. The Janus molecule is highly polarized; and the six-membered fluoro- and hydrocarbon rings are Lewis π-acidic and π-basic, respectively. The electrochemically-generated radical cation of the title compound is long-lived as characterized by electron paramagnetic resonance, whereas the radical anion is unstable in solution. The title compound reveals electrical properties of an insulator. On expanding its molecular scaffold towards partially fluorinated [n]phenylenes (n≥2), the properties presumably can be transformed into those of semiconductors. In this context, the title compound is suggested as a prototype scaffold for ambipolar materials for organic electronics and spintronics.

Validity and Reliability of a Site-Level Assessment Questionnaire to Assess Nutrition and Physical Activity Practices in Schools.

Background: Schools are an ideal setting for policy, systems, and environmental approaches to obesity prevention. Although school health environment assessments exist for planning purposes, we developed and tested a comprehensive questionnaire that is suitable for both evaluation and planning. Methods: Reliability was measured by comparing data collected by school personnel from low-income elementary schools across California at two time points, an average of 2 months apart (n = 23). To assess convergent validity, school responses were compared with the responses completed by the research team (n = 28). A weighted kappa test statistic and percent agreement were calculated for each question and specific groups of questions (questionnaire section, item topic, and response type). Results: Test/retest reliability of the questionnaire yielded kappa statistics that ranged from -0.14 to 1.00 (interquartile range [IQR] 0.36). Percent agreement for reliability ranged from 34.78 to 100.00 (IQR 21.7). Kappa statistics for validity ranged from -0.14 to 1.00 (IQR 0.44). Percent agreement for validity ranged from 14.29 to 100.00 (IQR 39.2). Based on these findings, the tool was revised. Conclusions: Study findings indicate that the Site-Level Assessment Questionnaire as tested is a reliable and accurate instrument for use in low-income elementary schools. Revisions may have improved the validity and reliability. We therefore recommend either version for use to support low-income schools in their efforts to assess needs, evaluate progress, and create action plans; and to supply high-quality, aggregable data for large-scale analysis. Additional testing is recommended to validate the revised version, increase generalizability, and determine sensitivity to detect change over time.

A salvage pathway maintains highly functional respiratory complex I.

Regulation of the turnover of complex I (CI), the largest mitochondrial respiratory chain complex, remains enigmatic despite huge advancement in understanding its structure and the assembly. Here, we report that the NADH-oxidizing N-module of CI is turned over at a higher rate and largely independently of the rest of the complex by mitochondrial matrix protease ClpXP, which selectively removes and degrades damaged subunits. The observed mechanism seems to be a safeguard against the accumulation of dysfunctional CI arising from the inactivation of the N-module subunits due to attrition caused by its constant activity under physiological conditions. This CI salvage pathway maintains highly functional CI through a favorable mechanism that demands much lower energetic cost than de novo synthesis and reassembly of the entire CI. Our results also identify ClpXP activity as an unforeseen target for therapeutic interventions in the large group of mitochondrial diseases characterized by the CI instability.

Reducing Hematologic Toxicity With Short Course Postexposure Prophylaxis With Zidovudine for HIV-1 Exposed Infants With Low Transmission Risk.

Using retrospectively collected data from 383 infants born to HIV-1-infected mothers receiving antiretroviral therapy, we compared transmission rates and hematologic toxicity between infants receiving 2-week (short course) versus longer duration zidovudine postexposure prophylaxis. Short course resulted in lower hematologic toxicity without evidence of increased vertical transmission risk.

Phenotypic spectrum and diagnostic pitfalls of ABCB4 deficiency depending on age of onset.

Genetic variants in the adenosine triphosphate-binding cassette subfamily B member 4 (ABCB4) gene, which encodes hepatocanalicular phosphatidylcholine floppase, can lead to different phenotypes, such as progressive familial intrahepatic cholestasis (PFIC) type 3, low phospholipid-associated cholelithiasis, and intrahepatic cholestasis of pregnancy. The aim of this multicenter project was to collect information on onset and progression of this entity in different age groups and to assess the relevance of this disease for the differential diagnosis of chronic liver disease. Clinical and laboratory data of 38 patients (17 males, 21 females, from 29 families) with homozygous or (compound) heterozygous ABCB4 mutations were retrospectively collected. For further analysis, patients were grouped according to the age at clinical diagnosis of ABCB4-associated liver disease into younger age (<18 years) or adult age (≥18 years). All 26 patients diagnosed in childhood presented with pruritus (median age 1 year). Hepatomegaly and splenomegaly were present in 85% and 96% of these patients, respectively, followed by jaundice (62%) and portal hypertension (69%). Initial symptoms preceded diagnosis by 1 year, and 13 patients received a liver transplant (median age 6.9 years). Of note, 9 patients were misdiagnosed as biliary atresia, Alagille syndrome, or PFIC type 1. In the 12 patients with diagnosis in adulthood, the clinical phenotype was generally less severe, including intrahepatic cholestasis of pregnancy, low phospholipid-associated cholelithiasis, or (non)cirrhotic PFIC3. Conclusion: ABCB4 deficiency with onset in younger patients caused a more severe PFIC type 3 phenotype with the need for liver transplantation in half the children. Patients with milder phenotypes are often not diagnosed before adulthood. One third of the children with PFIC type 3 were initially misdiagnosed, indicating the need for better diagnostic tools and medical education. (Hepatology Communications 2018;2:504-514).

Changes in Nutrition Policies and Dietary Intake in Child Care Homes Participating in Healthy Eating and Active Living Initiative.

INTRODUCTION: From 2012 to 2014, a total of 17 family child care homes participated in a multisector, community-wide initiative to prevent obesity. Strategies included staff workshops, materials, site visits, and technical assistance regarding development and implementation of nutrition policies. The purpose of the evaluation was to examine the impact of the initiative on family child care home nutrition-related policies and practices and child dietary intake. STUDY DESIGN: Pre- and post-intervention without control group. Measures taken at baseline and follow-up included structured observations and questionnaires regarding nutrition policies, practices, and environments; documentation of lunch foods served on 5 days; and lunch plate waste observations on 2 days. Paired t-tests were used to determine the significance of change over time. SETTING/PARTICIPANTS: Seventeen family child care homes in a low-income diverse community in Northern California; children aged 2-5 years who attended the family child care homes. MAIN OUTCOME MEASURES: Change in nutrition-related policies and practices, lunch foods served and consumed. RESULTS: Data was collected at 17 sites for an average of 5.2 children aged 2-5 years per site per day at baseline and 4.6 at follow-up for a total of 333 plate waste observations. There were significant increases in staff training, parental involvement, and several of the targeted nutrition-related practices; prevalence of most other practices either improved or was maintained over time. There were significant increases in the number of sites meeting Child and Adult Care Food Program meal guidelines, variety of fruit and frequency of vegetables offered, and reductions in frequency of juice and high-fat processed meats offered. Adequate portions of all food groups were consumed at both time points with no significant change over time. CONCLUSIONS: A simple, policy-focused intervention by a child care resource and referral agency was successful at reinforcing and improving upon nutrition-related practices at family child care homes. Children consumed adequate, but not excessive, portions of the balanced meals served to them, suggesting there is no reason to offer unhealthy options. SUPPLEMENT INFORMATION: This article is part of a supplement entitled Building Thriving Communities Through Comprehensive Community Health Initiatives, which is sponsored by Kaiser Permanente, Community Health.

Improvements in Physical Activity Opportunities: Results From a Community-Based Family Child Care Intervention.

INTRODUCTION: Reaching preschool-aged children to establish healthy lifestyle habits, including physical activity, is an important component of obesity prevention efforts. However, few studies have examined family child care homes where nearly 1 million children receive care. STUDY DESIGN: A pre- and post-intervention evaluation without a control group was conducted to evaluate what changes occurred in family child care homes that participated in the Healthy Eating and Active Living project, a multicomponent obesity prevention initiative, focused on community-driven policy and environmental change in neighborhoods within Kaiser Permanente service areas. SETTING/PARTICIPANTS: From 2012 to 2014, a total of 17 family child care homes in Northern California participated in the intervention. INTERVENTION: A physical activity workshop for child care staff and technical assistance to develop a policy to promote physical activity and other healthy behaviors. MAIN OUTCOME MEASURES: Pre and post observations, questionnaires, and physical activity logs were completed to assess change in physical activity resources available in the family child care homes, the amount of child screen time offered, type and amount of physical activity offered to children, and implementation of physical activity best practices. RESULTS: Between baseline and follow-up, providers significantly increased both the number of structured, adult-led activities (2.6 vs 3.2 activities per day) and the number of structured, adult-led minutes of activity in which children participated (49 vs 83 minutes per day). Providers also improved screen time practices and made improvements to the physical activity environment. CONCLUSIONS: In this study, a community-based organization designed and implemented multicomponent strategies tailored for participating family child care homes. The successful implementation of the intervention likely contributed to implementation of practices that increased opportunities for physical activity for the young children attending these family child care homes. SUPPLEMENT INFORMATION: This article is part of a supplement entitled Building Thriving Communities Through Comprehensive Community Health Initiatives, which is sponsored by Kaiser Permanente, Community Health.

CLPP deficiency protects against metabolic syndrome but hinders adaptive thermogenesis.

Mitochondria are fundamental for cellular metabolism as they are both a source and a target of nutrient intermediates originating from converging metabolic pathways, and their role in the regulation of systemic metabolism is increasingly recognized. Thus, maintenance of mitochondrial homeostasis is indispensable for a functional energy metabolism of the whole organism. Here, we report that loss of the mitochondrial matrix protease CLPP results in a lean phenotype with improved glucose homeostasis. Whole-body CLPP-deficient mice are protected from diet-induced obesity and insulin resistance, which was not present in mouse models with either liver- or muscle-specific depletion of CLPP However, CLPP ablation also leads to a decline in brown adipocytes function leaving mice unable to cope with a cold-induced stress due to non-functional adaptive thermogenesis. These results demonstrate a critical role for CLPP in different metabolic stress conditions such as high-fat diet feeding and cold exposure providing tools to understand pathologies with deregulated Clpp expression and novel insights into therapeutic approaches against metabolic dysfunctions linked to mitochondrial diseases.

[Frequency and Timing of Decisions to Limit Intensive Medical Care and Tumor-Specific Therapy in University Hematology and Oncology]. / Häufigkeit und Zeitpunkt von Entscheidungen gegen intensivmedizinische Maßnahmen und tumorspezifische Therapien in einer universitären Hämatologie und Onkologie.

Background Decisions to limit treatment (DLT) are important in order to prevent overtreatment at the end of life. However, they are not always discussed with the patient in advance or sufficiently documented. In a study to improve DLT in patients with an advanced hematological/ oncological disease we examined how often DLT precede deaths and how early they are determined. Methods In a period of 6 months, 567 patients with advanced hematological/ oncological neoplasias had been recruited for the cross-sectional study at the University hospital in Munich. Using a standardized registration form an embedded researcher documented which DLT were determined for the patients and which of them were implemented until death. Results For 26 % (n = 147) of the 567 patients a DLT was determined. These DLT were mostly documented in writing from the beginning on (90 %; n = 132), 20 % (n = 30) were modified. The proportion of deceased patients with DLT was 82 % (n = 62 of 76 deceased). The median time between the initial determination of a DLT and the patient's death was 6 days at normal ward and 10.5 days at palliative ward. Compared to hematological patients, DLT were more frequently diagnosed in patients with an oncological disease (64 vs. 36 %) and the decisions were made slightly earlier (7 vs. 5 days before death). Conclusion Our results show that DLT precede the death of many patients with a hematological/ oncological disease, but usually are made in the last week of life. This leads to the risk that the remaining few days to death are not sufficient for discussions with all parties involved and the planning of the end of life. These findings resulted in the development of an ethics policy for treatment limitation in cancer patients, which should support the concept of advance care planning. The project is funded by the German Cancer Aid.

Ascites' neutrophil function is significantly impaired in patients with decompensated cirrhosis but can be restored by autologous plasma incubation.

Systemic immune cell dysfunction is a typical feature of liver diseases and increases the risk of bacterial infection, especially spontaneous bacterial peritonitis. We evaluated functional properties of neutrophil granulocytes in blood and ascites of patients both with and without decompensated cirrhosis. We collected blood and ascites samples from 63 patients with cirrhosis and eight without cirrhosis. Phagocytosis activity (PA) and oxidative burst activity (OBA) were evaluated after ex vivo stimulation with E. coli, while fluorescence signals were measured by flow cytometry. Ascites' neutrophil function tests were repeated after incubation with autologous plasma. Ascites' neutrophils showed an impaired PA and OBA (median blood PA 98.1% (86.8-99.8) vs. ascites' PA 50.5% (0.4-97.3), p < 0.0001; median blood OBA 98.7% (27.5-100) vs. ascites' OBA 27.5% (0.3-96.7), p < 0.0001). Patients with non-cirrhotic ascites showed higher PA but equally suppressed OBA. Ascites' neutrophil function could be partially restored after incubation with autologous plasma (median increase PA: 22.5% (-49.7 - +93.2), p = 0.002; OBA: 22.8% (-10.4 - +48.8), p = 0.002). Ascites' neutrophils of patients with cirrhosis are functionally impaired, but could be partially restored after incubation with plasma. Further investigations are needed to identify the factors in ascites that are associated with neutrophils' function.

CLPP coordinates mitoribosomal assembly through the regulation of ERAL1 levels.

Despite being one of the most studied proteases in bacteria, very little is known about the role of ClpXP in mitochondria. We now present evidence that mammalian CLPP has an essential role in determining the rate of mitochondrial protein synthesis by regulating the level of mitoribosome assembly. Through a proteomic approach and the use of a catalytically inactive CLPP, we produced the first comprehensive list of possible mammalian ClpXP substrates involved in the regulation of mitochondrial translation, oxidative phosphorylation, and a number of metabolic pathways. We further show that the defect in mitoribosomal assembly is a consequence of the accumulation of ERAL1, a putative 12S rRNA chaperone, and novel ClpXP substrate. The presented data suggest that the timely removal of ERAL1 from the small ribosomal subunit is essential for the efficient maturation of the mitoribosome and a normal rate of mitochondrial translation.

Impact of the Berkeley Excise Tax on Sugar-Sweetened Beverage Consumption.

OBJECTIVES: To evaluate the impact of the excise tax on sugar-sweetened beverage (SSB) consumption in Berkeley, California, which became the first US jurisdiction to implement such a tax ($0.01/oz) in March 2015. METHODS: We used a repeated cross-sectional design to examine changes in pre- to posttax beverage consumption in low-income neighborhoods in Berkeley versus in the comparison cities of Oakland and San Francisco, California. A beverage frequency questionnaire was interviewer administered to 990 participants before the tax and 1689 after the tax (approximately 8 months after the vote and 4 months after implementation) to examine relative changes in consumption. RESULTS: Consumption of SSBs decreased 21% in Berkeley and increased 4% in comparison cities (P = .046). Water consumption increased more in Berkeley (+63%) than in comparison cities (+19%; P < .01). CONCLUSIONS: Berkeley's excise tax reduced SSB consumption in low-income neighborhoods. Evaluating SSB taxes in other cities will improve understanding of their public health benefit and their generalizability.

Loss of CLPP alleviates mitochondrial cardiomyopathy without affecting the mammalian UPRmt.

The mitochondrial matrix protease CLPP plays a central role in the activation of the mitochondrial unfolded protein response (UPR(mt)) in Caenorhabditis elegans Far less is known about mammalian UPR(mt) signaling, although similar roles were assumed for central players, including CLPP To better understand the mammalian UPR(mt) signaling, we deleted CLPP in hearts of DARS2-deficient animals that show robust induction of UPR(mt) due to strong dysregulation of mitochondrial translation. Remarkably, our results clearly show that mammalian CLPP is neither required for, nor it regulates the UPR(mt) in mammals. Surprisingly, we demonstrate that a strong mitochondrial cardiomyopathy and diminished respiration due to DARS2 deficiency can be alleviated by the loss of CLPP, leading to an increased de novo synthesis of individual OXPHOS subunits. These results question our current understanding of the UPR(mt) signaling in mammals, while introducing CLPP as a possible novel target for therapeutic intervention in mitochondrial diseases.

Hepatitis B surface antigen genetic elements critical for immune escape correlate with hepatitis B virus reactivation upon immunosuppression.

UNLABELLED: Hepatitis B virus (HBV) reactivation during immunosuppression can lead to severe acute hepatitis, fulminant liver failure, and death. Here, we investigated hepatitis B surface antigen (HBsAg) genetic features underlying this phenomenon by analyzing 93 patients: 29 developing HBV reactivation and 64 consecutive patients with chronic HBV infection (as control). HBsAg genetic diversity was analyzed by population-based and ultradeep sequencing (UDS). Before HBV reactivation, 51.7% of patients were isolated hepatitis B core antibody (anti-HBc) positive, 31.0% inactive carriers, 6.9% anti-HBc/anti-HBs (hepatitis B surface antibody) positive, 6.9% isolated anti-HBs positive, and 3.4% had an overt HBV infection. Of HBV-reactivated patients, 51.7% were treated with rituximab, 34.5% with different chemotherapeutics, and 13.8% with corticosteroids only for inflammatory diseases. In total, 75.9% of HBV-reactivated patients (vs. 3.1% of control patients; P<0.001) carried HBsAg mutations localized in immune-active HBsAg regions. Of the 13 HBsAg mutations found in these patients, 8 of 13 (M103I-L109I-T118K-P120A-Y134H-S143L-D144E-S171F) reside in a major hydrophilic loop (target of neutralizing antibodies [Abs]); some of them are already known to hamper HBsAg recognition by humoral response. The remaining five (C48G-V96A-L175S-G185E-V190A) are localized in class I/II-restricted T-cell epitopes, suggesting a role in HBV escape from T-cell-mediated responses. By UDS, these mutations occurred in HBV-reactivated patients with a median intrapatient prevalence of 73.3% (range, 27.6%-100%) supporting their fixation in the viral population as a predominant species. In control patients carrying such mutations, their median intrapatient prevalence was 4.6% (range, 2.5%-11.3%; P<0.001). Finally, additional N-linked glycosylation (NLG) sites within the major hydrophilic loop were found in 24.1% of HBV-reactivated patients (vs. 0% of chronic patients; P<0.001); 5 of 7 patients carrying these sites remained HBsAg negative despite HBV reactivation. NLG can mask immunogenic epitopes, abrogating HBsAg recognition by Abs. CONCLUSION: HBV reactivation occurs in a wide variety of clinical settings requiring immune-suppressive therapy, and correlates with HBsAg mutations endowed with enhanced capability to evade immune response. This highlights the need for careful patient monitoring in all immunosuppressive settings at reactivation risk and of establishing a prompt therapy to prevent HBV-related clinical complications.

Loss of UCP2 attenuates mitochondrial dysfunction without altering ROS production and uncoupling activity.

Although mitochondrial dysfunction is often accompanied by excessive reactive oxygen species (ROS) production, we previously showed that an increase in random somatic mtDNA mutations does not result in increased oxidative stress. Normal levels of ROS and oxidative stress could also be a result of an active compensatory mechanism such as a mild increase in proton leak. Uncoupling protein 2 (UCP2) was proposed to play such a role in many physiological situations. However, we show that upregulation of UCP2 in mtDNA mutator mice is not associated with altered proton leak kinetics or ROS production, challenging the current view on the role of UCP2 in energy metabolism. Instead, our results argue that high UCP2 levels allow better utilization of fatty acid oxidation resulting in a beneficial effect on mitochondrial function in heart, postponing systemic lactic acidosis and resulting in longer lifespan in these mice. This study proposes a novel mechanism for an adaptive response to mitochondrial cardiomyopathy that links changes in metabolism to amelioration of respiratory chain deficiency and longer lifespan.

Protein expression from exogenous mRNA: uptake by receptor-mediated endocytosis and trafficking via the lysosomal pathway.

Insertional mutagenesis and the inherent risk of malignancy compromise the clinical use of DNA-based therapies. Being a transient copy of genetic material, mRNA is a safe alternative, overcoming this limitation. As a prerequisite for the development of efficient mRNA-based therapies, we investigated the cellular uptake and intracellular fate of mRNA for the first time. To this end we determined cell-type, dose and energy dependence of mRNA internalisation. Moreover, we employed markers for uptake pathways and cellular compartments to analyse the route of mRNA internalisation and its intracellular destination. Finally, we addressed the involvement of receptors and their nature using a competitor-based approach. We found that all cell types tested were amenable to uptake and expression of naked mRNA. Internalisation mainly occurred via caveolae/lipid raft-rich membrane domains and involved scavenger-receptor(s). Following endocytosis, mRNA eventually accumulated in lysosomes, while part of it escaped into the cytosol giving rise to protein synthesis. Taken together, our findings provide unprecedented insights into the internalisation and trafficking of exogenous mRNA, greatly facilitating the development of effective mRNA-based therapies in the future.

Identification of an aliphatic epoxide and the corresponding dihydrodiol as novel congeners of zearalenone in cultures of Fusarium graminearum.

The mycotoxin zearalenone (ZEN) is produced by various Fusarium fungi and frequently found as a contaminant in food and feed. There are reports in the literature that several closely related analogues of ZEN are also formed in cultures of Fusarium species. We have therefore analyzed the organic extract from a 40 day culture of Fusarium graminearum by LC-DAD-MS and detected 15 compounds, which could be congeners of ZEN because of their ultraviolet, mass spectroscopy, and tandem mass spectroscopy spectra. In addition to confirming the previously reported α- and ß-stereoisomers of 5-hydroxy-ZEN and 10-hydroxy-ZEN, we identified seven ZEN congeners for the first time. One of the major novel congeners was shown by nuclear magnetic resonance spectroscopy and chemical synthesis to have the structure of an aliphatic ZEN epoxide, whereas two minor products proved to be the corresponding dihydrodiols. In addition, three stereoisomers of a cyclization product of the dihydrodiols, carrying a spiro-acetal group, were identified as fungal products for the first time. The latter may be artifacts, because the ZEN epoxide and dihydrodiol are unstable under acidic conditions and rearrange easily to the spiro-acetal compounds.

Lack of HLA class II antigen expression in microsatellite unstable colorectal carcinomas is caused by mutations in HLA class II regulatory genes.

Colorectal cancers (CRCs) develop on the basis of a deficient DNA mismatch repair (MMR) system in about 15% of cases. MMR-deficient CRC lesions show high-level microsatellite instability (MSI-H) and accumulate numerous mutations located at coding microsatellite loci that lead to the generation of immunogenic neopeptides. Consequently, the host's antitumoral immune response is of high importance for the course of the disease in MSI-H CRC patients. Accordingly, immune evasion mediated by impairment of HLA class I antigen presentation is frequently observed in these cancers. In this study, we aimed at a systematic analysis of alterations affecting HLA class II antigen expression in MSI-H CRC. HLA class II antigens are expressed by only two-thirds of MSI-H CRCs. The mechanisms underlying the lack of HLA class II antigens in a subset of MSI-H CRCs remain unknown. We here screened HLA class II regulatory genes for the presence of coding microsatellites and identified mutations of the essential regulator genes RFX5 in 9 (26.9%) out of 34 and CIITA in 1 (2.9%) out of 34 MSI-H CRCs. RFX5 mutations were related to lack of or faint HLA class II antigen expression (p = 0.006, Fisher's exact test). Transfection with wild-type RFX5 was sufficient to restore interferon gamma-inducible HLA class II antigen expression in the RFX5-mutant cell line HDC108. We conclude that somatic mutations of the RFX5 gene represent a novel mechanism of loss of HLA class II antigen expression in tumor cells, potentially contributing to immune evasion in MSI-H CRCs.

Immunoselective pressure and human leukocyte antigen class I antigen machinery defects in microsatellite unstable colorectal cancers.

In colorectal cancer, the immune response is particularly pronounced against tumors displaying the high microsatellite instability (MSI-H) phenotype. MSI-H tumors accumulate mutations affecting microsatellites located within protein encoding regions (coding microsatellites, cMS), which lead to translational shifts of the respective reading frames. Consequently, novel tumor-specific frameshift-derived neopeptides (FSP) are generated and presented by MSI-H tumor cells, thus eliciting effective cytotoxic immune responses. To analyze whether the immunoselective pressure was reflected by the phenotype of MSI-H colorectal cancer cells, we compared here the expression of antigen processing machinery (APM) components and human leukocyte antigen (HLA) class I antigen subunits in 20 MSI-H and 20 microsatellite-stable (MSS) colorectal cancer using a panel of newly developed APM component-specific monoclonal antibodies. In addition, we did a systematic analysis of mutations at cMS located within APM genes and beta2-microglobulin (beta2m). Total HLA class I antigen loss was observed in 12 (60.0%) of the 20 MSI-H lesions compared with only 6 (30.0%) of the 20 MSS colorectal cancer lesions. Moreover, total loss of membraneous HLA-A staining was significantly more frequent in MSI-H colorectal cancer (P = 0.0024). Mutations at cMS of beta2m and genes encoding APM components (TAP1 and TAP2) were detected in at least 7 (35.0%) of 20 MSI-H colorectal cancers but in none of the MSS colorectal cancers (P = 0.0002). These data show that defects of HLA class I antigen processing and presentation seem to be significantly more frequent in MSI-H than in MSS colorectal cancer, suggesting that in MSI-H colorectal cancer the immunoselective pressure leads to the outgrowth of cells with defects of antigen presentation.