Improvements in antimicrobial prescribing for treatment of upper respiratory tract infections through provider education

BACKGROUND: Inappropriate use of antimicrobials to treat acute upper respiratory tract infections (URIs), which usually have a viral etiology, contributes to emergence and spread of antimicrobial resistance in Streptococcus pneumoniae and other human bacterial pathogens. OBJECTIVE: To reduce antimicrobial use for management of acute URIs in adult and pediatric patients. DESIGN: Prospective, nonrandomized, controlled trial. SETTING: Four primary care clinics within a staff model HMO in Detroit, Mich. PARTICIPANTS: Twenty-one primary care physicians at clinics where the educational intervention was implemented, and 9 primary care physicians at control clinics where no educational programs were implemented. MEASUREMENTS: Antibiotic prescribing for acute URIs during the baseline and study years among the intervention and control groups. Results: A generalized linear mixed-effects model was used and showed that antimicrobial prescribing among the intervention group physicians decreased 24.6% from the baseline to the postintervention period (P<.0001) for both pediatric and adult medicine physicians. From the baseline to the study period, there was no significant decline in rates of antimicrobial prescribing by the control group of physicians (pediatricians, P=.35; internists, P=.42). The rates of decline in antimicrobial prescribing differed significantly between the intervention and control groups (P<.0003 for pediatricians and P<.01 for Internists). CONCLUSIONS: An interactive, case-based educational program for physicians and their staff proved effective for reducing unwarranted prescribing of antibiotics in the treatment of URIs by primary care physicians in a Medicaid HMO setting.     

Oncogenic KRAS engages an RSK1/NF1 pathway to inhibit wild-type RAS signaling in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy with limited treatment options. Although activating mutations of the KRAS GTPase are the predominant dependency present in >90% of PDAC patients, targeting KRAS mutants directly has been challenging in PDAC. Similarly, strategies targeting known KRAS downstream effectors have had limited clinical success due to feedback mechanisms, alternate pathways, and dose-limiting toxicities in normal tissues. Therefore, identifying additional functionally relevant KRAS interactions in PDAC may allow for a better understanding of feedback mechanisms and unveil potential therapeutic targets. Here, we used proximity labeling to identify protein interactors of active KRAS in PDAC cells. We expressed fusions of wild-type (WT) (BirA-KRAS4B), mutant (BirA-KRAS4B^G12D), and nontransforming cytosolic double mutant (BirA-KRAS4B^G12D/C185S) KRAS with the BirA biotin ligase in murine PDAC cells. Mass spectrometry analysis revealed that RSK1 selectively interacts with membrane-bound KRAS^G12D, and we demonstrate that this interaction requires NF1 and SPRED2. We find that membrane RSK1 mediates negative feedback on WT RAS signaling and impedes the proliferation of pancreatic cancer cells upon the ablation of mutant KRAS. Our findings link NF1 to the membrane-localized functions of RSK1 and highlight a role for WT RAS signaling in promoting adaptive resistance to mutant KRAS-specific inhibitors in PDAC.

A total of 60,430 new cases of pancreatic cancer were estimated for 2021, and the 5-y relative survival rate has consistently remained below 11% (1). About 85% of these pancreatic cancer tumors are pancreatic ductal adenocarcinoma (PDAC) (2). Poor outcomes of PDAC cases result from late diagnoses leading to unresectable and heterogeneous tumors as well as ineffective therapies, which only prolong survival on the order of months (3–5). Mutations in the KRAS proto-oncogene are present in over 90% of PDAC cases and are associated with a poor prognosis (6). Furthermore, mice expressing mutant KRAS in the pancreas develop precursor lesions, which sporadically progress into frank PDAC. This progression is accelerated when combined with other mutations or deletion of tumor suppressor genes (7–11). Additionally, independent studies have shown that the maintenance of murine PDAC cells require KRAS (12–14).As a RAS GTPase, KRAS acts as a molecular switch at the plasma membrane that relays growth factor signaling from receptor tyrosine kinases to downstream pathways such as RAF/MEK and PI3K/AKT (15). GTP binding alters the conformation of the KRAS G domain, thereby creating binding sites for downstream effectors to trigger enzymatic cascades that promote cell transformation (16–19). Intrinsically, KRAS slowly hydrolyzes GTP into GDP to halt signaling; however, GTPase activating proteins (GAPs) such as neurofibromin 1(NF1) catalyze this process (20). In contrast, guanine nucleotide exchange factors, such as son of sevenless homolog 1 (SOS1), catalyze the exchange of GTP for bound GDP. In most PDAC cases, KRAS is mutated at the 12th residue located in the G domain from glycine to either a valine (G12V), or more commonly, aspartate (G12D). These mutations sterically prevent the “arginine finger domain” of GAPs from entering the GTPase site, thereby blocking extrinsic allosteric GTPase activation and stabilizing RAS-GTP (21, 22). Activating mutations in KRAS constitutively trigger RAF/MEK and PI3K/AKT pathways leading to increased cell proliferation as well as other prooncogenic behaviors (15). KRAS signaling not only relies on the G domain but also the C-terminal hypervariable domain (HVR), which is required to stabilize KRAS on membranes where signaling is most efficient (23–26). Independent studies suggest that specific biochemical and cellular consequences of KRAS activation are attributed to the unique properties of the HVR of the predominant splice form KRAS4B, namely the polybasic domain and the lipid anchor (27–30). Localization of RAS proteins to the plasma membrane requires the prenylation of the CAAX motif (23). Additionally, for KRAS4B, the hypervariable region contains a highly polybasic domain consisting of several consecutive lysines, which can interact with the negative charges on the polar heads of phospholipids and stabilize protein interactions (31). Structural and biochemical characterization of the HVR and G domain has contributed to a better understanding of the signaling outputs of KRAS and led to KRAS-targeting strategies.Various approaches to inhibit KRAS include direct inhibition, expression interference, mislocalization, and targeting of downstream effectors (32). Thus far, direct inhibitors against KRAS have only successfully targeted the G12C mutant, which comprises 2.9% of KRAS mutant PDAC (21, 33). For other KRAS mutants, targeting downstream effectors of KRAS in pancreatic cancer remains an alternative approach. Unfortunately, dual inhibition of MEK and AKT pathways was ineffective in PDAC patients (34). Difficulty in targeting KRAS due to adaptive resistance and feedback regulation motivates a better understanding of KRAS biology (35). For example, although PDAC typically features a mutant KRAS, there may be a role for its wild-type (WT) counterpart as well as WT RAS paralogs (HRAS and NRAS), which are GAP sensitive and subject to signaling feedback. While oncogenic KRAS has been shown to activate WT HRAS and NRAS via allosteric stimulation of SOS1 (36), WT KRAS has been proposed to be a tumor suppressor in some KRAS mutant cancers based on the commonly observed mutant-specific allele imbalance that occurs throughout tumor progression (37). Additionally, the reintroduction of WT KRAS abolished tumor T cell acute lymphoblastic leukemia development and impaired tumor growth in KRAS mutant lung cancer cells in vivo (37–39). The discovery of novel KRAS protein interactors involved in downstream signaling or feedback and compensatory pathways may elucidate why inhibition of downstream pathways have had limited clinical impact in PDAC. Here, we perform proximity labeling experiments by expressing a fusion of BirA^R118G biotin ligase and KRAS in PDAC cells, which, in the presence of high concentrations of biotin, generates reactive biotinoyl-AMP that labels lysines of nearby proteins, such as interactors of its fusion partner KRAS (40–42). The biotinylated interactor proteins can be isolated by streptavidin pulldown and analyzed by proteomics to identify novel protein interactors (43–45). Because covalent labeling occurs in living cells, enzymatic labeling may potentially identify transient interactors and protein complexes.Two recent studies used proximity-dependent biotin identification (BioID) labeling methods to identify KRAS interactors in 293T and colon cancer cells (46, 47). These studies uncovered and validated the functional relevance of PIP5KA1 and mTORC2 in PDAC cells. However, BirA-KRAS screens in PDAC models have not yet been performed. Since the tumor context may determine protein expression and relevant interactions, we sought to perform a BirA-KRAS screen in PDAC cells. We hypothesize that proximity labeling with BioID presents a means for identifying new mutant KRAS-specific interactions in PDAC, which may unveil new insights into therapeutic design for this malignancy.     

A role for Toll-like receptors in acquired immunity: up-regulation of TLR9 by BCR triggering in naive B cells and constitutive expression in memory B cells

Toll-like receptors (TLRs) are pattern recognition receptors that trigger innate immunity. In this study we investigated the expression of 10 TLRs in human naive and memory B-cell subsets. We report that in human naive B cells most TLRs are expressed at low to undetectable levels, but the expression of TLR9 and TLR10 is rapidly induced following B-cell-receptor (BCR) triggering. In contrast, memory B cells express several TLRs at constitutively high levels. The differential expression of TLR9 correlates with responsiveness to its agonist, CpG DNA. Thus, human memory B cells proliferate and differentiate to immunoglobulin (Ig)-secreting cells in response to CpG, while naive B do so only if simultaneously triggered through the BCR. The BCR-induced expression of TLRs in human naive B cells prevents polyclonal activation in a primary response, because it restricts stimulation to antigen-specific B cells. In contrast, the constitutive expression of TLRs in memory B cells allows polyclonal activation of the entire memory pool. Thus, in human B cells TLRs are downstream of BCR and play a role both in the primary response and in the memory phase.     

MARS: a futile tool in centres without active liver transplant support.

BACKGROUND AND AIM: Studies on Molecular Adsorbent Recycling Systems (MARS) showed inconclusive survival benefits. PATIENTS AND METHOD: We evaluated the efficacy of MARS for patients with either acute liver failure (ALF) or acute-on-chronic liver failure (AoCLF) at our centre, from February 2002 till April 2006 retrospectively. RESULTS: Fifty ALF patients underwent median (range) three (1-10) sessions of MARS. Acute exacerbations of chronic hepatitis B (n=26) and drug-induced liver injury (n=12) were the commonest causes. Living donors were available in 6, 2 paediatric patients underwent left lobe and four adults underwent right lobe living donor liver transplant. Among the 44 ALF patients without a suitable living donor, one underwent deceased donor liver transplant and survived, another 19-year-old male with acute exacerbations of chronic hepatitis B recovered without transplant, and the rest died. Twenty-six had AoCLF and underwent four (1-10) MARS sessions. Sepsis (n=16) and upper gastrointestinal bleeding (n=4) were the commonest precipitating factors. None had a suitable living or deceased donor, suitable for transplantation during their hospitalization. Only one of 26 AoCLF patients survived the hospitalization, but the survivor died of sepsis 1 month later. CONCLUSION: In this non-randomized study, survival after MARS was related to the availability of transplant, and in patients where living or deceased donor transplant was unavailable, MARS was of little benefit. Randomized-controlled trials on MARS((R)) are urgently needed to clarify its clinical utility.     

Increased presence of anti-HLA antibodies early after allogeneic granulocyte colony-stimulating factor-mobilized peripheral blood hematopoietic stem cell transplantation compared with bone marrow transplantation

We have recently shown that the use of allogeneic granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood hematopoietic stem cell transplantation (PBHSCT), as compared with bone marrow transplantation (BMT), is associated with increased titers of antibodies (Abs) directed against red blood cell ABO antigens. To further evaluate the influence of a G-CSF-mobilized PBHSCT graft on alloimmune Ab responses, we examined the frequency of anti-HLA Abs after transplantation in the setting of the same randomized study, comparing PBHSCT with BMT in adults. Anti-HLA Ab presence was determined by complement-dependent cytotoxicity assay (CDC) and flow cytometry in the recipient before and 30 days after transplantation as well as in the donor before graft donation. The use of PBHSCT was significantly associated with increased detection of anti-HLA immunoglobulin G (IgG) Abs early after transplantation as evidenced by flow cytometry (11 of 24 versus 4 of 27 transplant recipients, P =.03) and, less so, by CDC (5 of 24 versus 1 of 27 transplant recipients, P =.09). The difference between PBHSCT and BMT was further heightened when analysis was restricted to anti-HLA IgG Ab-negative donor/recipient pairs. In such a setting, early anti-HLA Ab was never detected after BMT but was repeatedly detected after PBHSCT (flow cytometry, 6 of 18 versus 0 of 17 transplant recipients, P =.02; CDC, 4 of 23 versus 0 of 26 transplant recipients, P =.04). Importantly, the PBHSCT-associated increase in anti-HLA Ab detection was observed despite a reduction in the median number of platelet-transfusion episodes per patient in PBHSC transplant versus BM transplant recipients (3 platelet-transfusion episodes [range, 1-21] in PBHSCT group vs 6 platelet-transfusion episodes [range, 3-33] in the BMT group; P =.02). In conclusion, this study strongly suggests that G-CSF-mobilized PBHSCT results in an increased incidence of circulating anti-HLA Abs and further confirms that the use of such a graft alters alloimmune Ab responses.     

Inguinal hernia repair: Toward Asian guidelines

Groin hernias are very common, and surgical treatment is usually recommended. In fact, hernia repair is the most common surgical procedure performed worldwide. In countries such as the USA, China, and India, there may easily be over 1 million repairs every year. The need for this surgery has become an important socioeconomic problem and may affect health‐care providers, especially in aging societies. Surgical repair using mesh is recommended and widely employed in Western countries, but in many developing countries, tissue‐to‐tissue repair is still the preferred surgical procedure due to economic constraints. For these reason, the development and implementation of guidelines, consensus, or recommendations may aim to clarify issues related to best practices in inguinal hernia repair in Asia. A group of Asian experts in hernia repair gathered together to debate inguinal hernia treatments in Asia in an attempt to reach some consensus or develop recommendations on best practices in the region. The need for recommendations or guidelines was unanimously confirmed to help overcome the discrepancy in clinical practice between countries; the experts decided to focus mainly on the technical aspects of open repair, which is the most common surgery for hernia in our region. After the identification of 12 main topics for discussion (indication, age, and sex; symptomatic and asymptomatic hernia: type of hernia; type of treatment; hospital admission; preoperative care; anesthesia; surgical technique; perioperative care; postoperative care; early complications; and long‐term complications), a search of the literature was carried out according to the five levels of the Oxford Classification of Evidence and the four grades of recommendation.