Citations

Abstract Little is known about the regulatory roles of specific soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins in cytotoxic lymphocytes. Recent information suggests that mutations in the SNARE protein syntaxin 11 result in a form of familial hemophagocytic lymphohistiocytosis (FHL). Because genetic abnormalities in key granule components (e.g., perforin) or in regulators of secretion (e.g., Munc13–4) underlie the other identified forms of FHL, we assessed whether syntaxin 11 might also serve a related regulatory role. We determined that syntaxin 11 is expressed in NK cells and activated CTLs and is located in discrete membrane-associated structures in the cytoplasm. Enhanced expression of syntaxin 11 augments the secretion and killing of tumor targets, and suppression of syntaxin 11 expression inhibits these functions. Our data identify and characterize a role for syntaxin 11 in granule exocytosis and in the generation of cell-mediated killing. These results also provide new insights on the mechanisms of hemopoietic dysregulation in FHL.

Abstract NK cells are innate immune cells that can eliminate their targets through granule release. In this study, we describe a specialized role for the large GTPase Dynamin 2 (Dyn2) in the regulation of these secretory events leading to cell-mediated cytotoxicity. By modulating the expression of Dyn2 using small interfering RNA or by inhibiting its activity using a pharmacological agent, we determined that Dyn2 does not regulate conjugate formation, proximal signaling, or granule polarization. In contrast, during cell-mediated killing, Dyn2 localizes with lytic granules and polarizes to the NK cell–target interface where it regulates the final fusion of lytic granules with the plasma membrane. These findings identify a novel role for Dyn2 in the exocytic events required for effective NK cell-mediated cytotoxicity.

Abstract Activation-induced cytidine deaminase (AID) initiates Ab class-switch recombination (CSR) in activated B cells resulting in exchanging the IgH C region and improved Ab effector function. During CSR, AID instigates DNA double-strand break (DSB) formation in switch (S) regions located upstream of C region genes. DSBs are necessary for CSR, but improper regulation of DSBs can lead to chromosomal translocations that can result in B cell lymphoma. The protein kinase ataxia telangiectasia mutated (ATM) is an important proximal regulator of the DNA damage response (DDR), and translocations involving S regions are increased in its absence. ATM phosphorylates H2AX, which recruits other DNA damage response (DDR) proteins, including mediator of DNA damage checkpoint 1 (Mdc1) and p53 binding protein 1 (53BP1), to sites of DNA damage. As these DDR proteins all function to promote repair and recombination of DSBs during CSR, we examined whether mouse splenic B cells deficient in these proteins would show alterations in S region DSBs when undergoing CSR. We find that in atm−/− cells Sμ DSBs are increased, whereas DSBs in downstream Sγ regions are decreased. We also find that mutations in the unrearranged Sγ3 segment are reduced in atm−/− cells. Our data suggest that ATM increases AID targeting and activity at downstream acceptor S regions during CSR and that in atm−/− cells Sμ DSBs accumulate as they lack a recombination partner.

Purpose Liver injury is a serious adverse event leading to permanent discontinuation of lapatinib in affected patients. This study aimed to validate previously associated major histocompatibility complex (MHC) variants as predictors of risk of liver injury by using a large, randomized, placebo-controlled trial of lapatinib in human epidermal growth factor receptor 2–positive, early-stage breast cancer (Tykerb Evaluation After Chemotherapy [TEACH]: Lapatinib Versus Placebo In Women With Early-Stage Breast Cancer). Patients and Methods The frequency of ALT elevation cases was compared among four MHC variants in 1,194 patients randomly assigned to lapatinib. Cumulative ALT elevation time courses during treatment were also compared between carriers and noncarriers of specified MHC variants. Results In lapatinib-treated patients, there was a significant difference in ALT case incidence between HLA carriers and noncarriers. The highly correlated alleles HLA-DRB1*07:01 and HLA-DQA1*02:01 (study frequency, 22.4%) were associated with ALT elevation (odds ratio, 14) between cases (n = 37) and controls (n = 1,071). These associations strengthened at higher ALT elevation thresholds and in Hy's Law cases. In lapatinib-treated patients, the overall risk for National Cancer Institute-Common Terminology Criteria for Adverse Events grade 3 ALT elevation (> 5× upper limit of normal) was 2.1%; HLA allele carriers had an increased risk of 7.7%; in noncarriers, risk was reduced to 0.5%, comparable to ALT elevation for all patients receiving placebo. The increase in ALT case incidence in the lapatinib arm showed no evidence of plateau during 1 year of lapatinib treatment. Conclusion These results validate HLA-DRB1*07:01 allele carriage as a predictor of increased risk of lapatinib-induced liver injury and implicate an immune pathology. The HLA association could support clinical management of patients experiencing hepatotoxicity during lapatinib treatment.

Background and Purpose— To address the increasing need to counsel patients about treatment indications for unruptured intracranial aneurysms (UIA), we endeavored to develop a consensus on assessment of UIAs among a group of specialists from diverse fields involved in research and treatment of UIAs. Methods— After composition of the research group, a Delphi consensus was initiated to identify and rate all features, which may be relevant to assess UIAs and their treatment by using ranking scales and analysis of inter-rater agreement (IRA) for each factor. IRA was categorized as very high, high, moderate, or low. Results— Ultimately, 39 specialists from 4 specialties agreed (high or very high IRAs) on the following key factors for or against UIA treatment decisions: (1) patient age, life expectancy, and comorbid diseases; (2) previous subarachnoid hemorrhage from a different aneurysm, family history for UIA or subarachnoid hemorrhage, nicotine use; (3) UIA size, location, and lobulation; (4) UIA growth or de novo formation on serial imaging; (5) clinical symptoms (cranial nerve deficit, mass effect, and thromboembolic events from UIAs); and (6) risk factors for UIA treatment (patient age and life expectancy, UIA size, and estimated risk of treatment). However, IRAs for features rated with low relevance were also generally low, which underlined the existing controversy about the natural history of UIAs. Conclusions— Our results highlight that neurovascular specialists currently consider many features as important when evaluating UIAs but also highlight that the appreciation of natural history of UIAs remains uncertain, even within a group of highly informed individuals.

BACKGROUNDGeneral internists suffer higher rates of burnout and lower satisfaction with work‐life balance than most specialties, but the impact of inpatient vs outpatient practice location is unclear.METHODSPhysicians in the American Medical Association Physician Masterfile were previously surveyed about burnout, depression, suicidal ideation, quality of life, fatigue, work‐life balance, career plans, and health behaviors. We extracted and compared data for these variables for the 130 internal medicine hospitalists and 448 outpatient general internists who participated. Analyses were adjusted for age, sex, hours worked, and practice setting.RESULTSThere were 52.3% of the hospitalists and 54.5% of the outpatient internists affected by burnout (P = 0.86). High scores on the emotional exhaustion subscale (43.8% vs 48.1%, P = 0.71) and on the depersonalization subscale (42.3% vs 32.7%, P = 0.17) were common but similar in frequency in the 2 groups. Hospitalists were more likely to score low on the personal accomplishment subscale (20.3% vs 9.6%, P = 0.04). There were no differences in symptoms of depression (40.3% for hospitalists vs 40.0% for outpatient internists, P = 0.73) or recent suicidality (9.2% vs 5.8%, P = 0.15). Rates of reported recent work‐home conflict were similar (48.4% vs 41.3%, P = 0.64), but hospitalists were more likely to agree that their work schedule leaves enough time for their personal life and family (50.0% vs 42.0%, P = 0.007).CONCLUSIONSBurnout was common among both hospitalists and outpatient general internists, although hospitalists were more satisfied with work‐life balance. A better understanding of the causes of distress and identification of solutions for all internists is needed. Journal of Hospital Medicine 2014;9:176–181. © 2014 Society of Hospital Medicine