ROCK2 inhibition triggers the collective invasion of colorectal adenocarcinomas.

The metastatic progression of cancer is a multi-step process initiated by the local invasion of the peritumoral stroma. To identify the mechanisms underlying colorectal carcinoma (CRC) invasion, we collected live human primary cancer specimens at the time of surgery and monitored them ex vivo. This revealed that conventional adenocarcinomas undergo collective invasion while retaining their epithelial glandular architecture with an inward apical pole delineating a luminal cavity. To identify the underlying mechanisms, we used microscopy-based assays on 3D organotypic cultures of Caco-2 cysts as a model system. We performed two siRNA screens targeting Rho-GTPases effectors and guanine nucleotide exchange factors. These screens revealed that ROCK2 inhibition triggers the initial leader/follower polarization of the CRC cell cohorts and induces collective invasion. We further identified FARP2 as the Rac1 GEF necessary for CRC collective invasion. However, FARP2 activation is not sufficient to trigger leader cell formation and the concomitant inhibition of Myosin-II is required to induce invasion downstream of ROCK2 inhibition. Our results contrast with ROCK pro-invasive function in other cancers, stressing that the molecular mechanism of metastatic spread likely depends on tumour types and invasion mode.

Missing Voices: What Early Career Hospitalists View as Essential in Hospital Medicine-Focused Education.

OBJECTIVES: Acknowledging that a successful career in hospital medicine (HM) requires specialized skills, residency programs have developed hospital medicine-focused education (HMFE) programs. Surveys of Internal Medicine residency leaders have described HMFE curricula but are limited to that specialty and lack perspectives from early career hospitalists (ECHs) who recently completed this training. As such, we surveyed multispecialty ECHs to evaluate their preferences for HMFE and to identify gaps in standard residency training and career development that HMFE can bridge. The objectives of our study were to describe multispecialty ECH needs and preferences for HMFE and to identify gaps in standard residency training and career development that HMFE can bridge. METHODS: From February to March 2021, ECHs (defined as hospitalists within 0-5 years from residency) were surveyed using the Society of Hospital Medicine's listserv. Respondents identified as having participated in HMFE or not during residency (defining them as HMFE participants or non-HMFE participants). RESULTS: From 257 respondents, 84 (33%) ECHs met inclusion criteria. Half (n = 42) were HMFE participants. ECHs ranked clinical hospitalist career preparation (86%) and mentorship from HM faculty (85%) as the most important gaps in standard residency training and career development that HMFE can bridge. Other key components of HMFE included exposure to quality improvement, patient safety, and high-value care (67%); provision of autonomy through independent rounding (54%); and preparation for the job application process (70%). CONCLUSIONS: Multispecialty ECHs describe HMFE as positively influencing their decision to pursue a hospitalist career and increasing their preparedness for practice. HMFE may be particularly well suited to foster advanced clinical skills such as independent rounding, critical thinking, and self-reflection. We propose an organizing framework for HMFE in residency that may assist in the implementation and innovation of HMFE programs nationwide and in the development of standardized HMFE competencies.

Impact of Bedside Rounding on Attending Teaching Evaluations.

OBJECTIVE: To examine associations between bedside rounding (BSR) and other rounding strategies (ORS) with resident evaluations of teaching attendings and self-reported attending characteristics. METHODS: Faculty from three academic medical centers who attended resident teaching services for ≥4 weeks during the 2018-2019 academic year were invited to complete a survey about personal and rounding characteristics. The survey instrument was iteratively developed to assess rounding strategy as well as factors that could affect choosing one rounding strategy over another. Survey results and teaching evaluation scores were linked, then deidentified and analyzed in aggregate. Included evaluation items assessed resident perceptions of autonomy, time management, professionalism, and teaching effectiveness, as well as a composite score (the numeric average of each attending's scores for all of the items at his or her institution). BSR was defined as spending >50% of rounding time in patients' rooms with the team. Hallway rounding and conference room rounding were combined into the ORS category and defined as >50% of rounding time in these settings. All of the scores were normalized to a 10-point scale to allow aggregation across sites. RESULTS: A total of 105 attendings were invited to participate, and 65 (62%) completed the survey. None of the resident evaluation scores significantly differed based on rounding strategy. Composite scores were similar for BSR and ORS (difference of <0.1 on a 10-point scale). Spearman correlation coefficients identified no statistically significant correlation between rounding strategy and evaluation scores. An exploratory analysis of variance model identified no single factor that was significantly associated with composite teaching scores (P > 0.45 for all) or the domains of teaching efficacy, professionalism, or autonomy (P > 0.13 for all). Having a formal educational role was significantly associated with better evaluation scores for time management, and the number of lectures delivered per year approached statistical significance for the same domain. CONCLUSIONS: Conducting BSR did not significantly affect resident evaluations of teaching attendings. Resident perception of teaching effectiveness based on rounding strategy should be neither a motivator nor a barrier to widespread institution of BSR.

ß-Pix directs collective migration of anterior visceral endoderm cells in the early mouse embryo.

Collective epithelial migration is important throughout embryonic development. The underlying mechanisms are poorly understood but likely involve spatially localized activation of Rho GTPases. We previously reported that Rac1 is essential for generating the protrusive activity that drives the collective migration of anterior visceral endoderm (AVE) cells in the early mouse embryo. To identify potential regulators of Rac1, we first performed an RNAi screen of Rho family exchange factors (guanine nucleotide exchange factor [GEF]) in an in vitro collective epithelial migration assay and identified ß-Pix. Genetic deletion of ß-Pix in mice disrupts collective AVE migration, while high-resolution live imaging revealed that this is associated with randomly directed protrusive activity. We conclude that ß-Pix controls the spatial localization of Rac1 activity to drive collective AVE migration at a critical stage in mouse development.

Corrosive substances ingestion: a review.

Corrosive chemical substance ingestions are a major problem, especially in developing countries, but also in developed countries such as the United States, France, and Belgium. Ingestions may be deliberate as suicide attempts (mostly in adolescents and adults) or accidental (mostly in children). The results can be devastating in terms of individual suffering and disability, but also in terms of resource utilization and costs. In developing countries, outcomes may be worse because of limited medical/surgical resources. Common sequelae include gastrointestinal (GI) tract (esophagus, stomach, pylorus, and duodenum) stricture formation, GI tract perforation, and hemorrhage. Systemic effects may also occur, such as disseminated intravascular coagulation (DIC), multi-organ system failure, and sepsis. Various interventions in the acute phase to reduce the severity of injury have been attempted, but there are no large controlled clinical trials to demonstrate efficacy. Dilation therapy in various forms is commonly used for the treatment of strictures and a variety of surgical procedures including esophagectomy and delayed replacement may be required in severe corrosive injury cases.

Acute chemical skin injuries in the United States: a review.

The objective was to perform a thorough review of published and other available data to elucidate the extent of chemical skin injuries in the US. Chemical skin injuries differ significantly from skin lesions produced by other injury mechanisms, so this review was restricted to the former. Retrieval of relevant published data was performed in PubMed and Google. Other data were retrieved from the American College of Surgeons National Trauma Databank, American Burn Association National Burn Repository, US Department of Labor Bureau of Labor Statistics, websites of all 50 US States Departments of Health, and the National Poison Data System of the American Association of Poison Control Centers. Two areas of significance in disfiguring skin burn injuries and particularly of chemical skin injuries, psychosocial issues and the associated financial burden, have been briefly reviewed. Because of the paucity of published data, international as well as US data have been included. A brief description of an active flushing fluid as an alternative to potable water, Diphoterine® solution, has also been included. Chemical skin injuries generally comprise approximately 2-5% of all skin burns, but sometimes higher percentages have been reported. Data analysis shows that while there are various sources regarding the epidemiology of chemical skin injuries, the total annual number cannot be determined because there is no centralized US national reporting mechanism. Literature and clinical experience demonstrate the importance of chemical skin injuries in USA. Dermal exposures to chemicals can result in mortality and morbidity. Chemical skin injuries can be avoided or ameliorated and preventive advanced measures should be taken to reduce or ameliorate them.

SOS1 and Ras regulate epithelial tight junction formation in the human airway through EMP1.

The human airway is lined with respiratory epithelial cells, which create a critical barrier through the formation of apical tight junctions. To investigate the molecular mechanisms underlying this process, an RNAi screen for guanine nucleotide exchange factors (GEFs) was performed in human bronchial epithelial cells (16HBE). We report that SOS1, acting through the Ras/MEK/ERK pathway, is essential for tight junction formation. Global microarray analysis identifies epithelial membrane protein 1 (EMP1), an integral tetraspan membrane protein, as a major transcriptional target. EMP1 is indispensable for tight junction formation and function in 16HBE cells and in a human airway basal progenitor-like cell line (BCi-NS1.1). Furthermore, EMP1 is significantly downregulated in human lung cancers. Together, these data identify important roles for SOS1/Ras and EMP1 in tight junction assembly during airway morphogenesis.

Wnt signaling pathways meet Rho GTPases.

Wnt ligands and their receptors orchestrate many essential cellular and physiological processes. During development they control differentiation, proliferation, migration, and patterning, while in the adult, they regulate tissue homeostasis, primarily through their effects on stem cell proliferation and differentiation. Underpinning these diverse biological activities is a complex set of intracellular signaling pathways that are still poorly understood. Rho GTPases have emerged as key mediators of Wnt signals, most notably in the noncanonical pathways that involve polarized cell shape changes and migrations, but also more recently in the canonical pathway leading to beta-catenin-dependent transcription. It appears that Rho GTPases integrate Wnt-induced signals spatially and temporally to promote morphological and transcriptional changes affecting cell behavior.

Functional cross-talk between Cdc42 and two downstream targets, Par6B and PAK4.

The establishment of polarity is an essential step in epithelial morphogenesis. Polarity proteins promote an apical/basal axis, which, together with the assembly of apical adherens and tight junctions, directed vesicle transport and the reorganization of the actomyosin filament network, generate a stable epithelium. The regulation of these cellular activities is complex, but the Rho family GTPase Cdc42 (cell division cycle 42) is known to play a key role in the establishment of polarity from yeast to humans. Two Cdc42 target proteins, the kinase PAK4 [p21 protein (Cdc42/Rac)-activated kinase 4] and the scaffold partitioning defective (Par) 6B, are required to promote the assembly of apical junctions in human bronchial epithelial cells. We show in the present paper that PAK4 phosphorylates Par6B at Ser143 blocking its interaction with Cdc42. This provides a potential new mechanism for controlling the subcellular localization of Par6B and its interaction with other proteins.

Identifying knowledge activism in worker health and safety representation: A cluster analysis.

BACKGROUND: Although worker representation in OHS has been widely recognized as contributing to health and safety improvements at work, few studies have examined the role that worker representatives play in this process. Using a large quantitative sample, this paper seeks to confirm findings from an earlier exploratory qualitative study that worker representatives can be differentiated by the knowledge intensive tactics and strategies that they use to achieve changes in their workplace. METHODS: Just under 900 worker health and safety representatives in Ontario completed surveys which asked them to report on the amount of time they devoted to different types of representation activities (i.e., technical activities such as inspections and report writing vs. political activities such as mobilizing workers to build support), the kinds of conditions or hazards they tried to address through their representation (e.g., housekeeping vs. modifications in ventilation systems), and their reported success in making positive improvements. A cluster analysis was used to determine whether the worker representatives could be distinguished in terms of the relative time devoted to different activities and the clusters were then compared with reference to types of intervention efforts and outcomes. RESULTS: The cluster analysis identified three distinct groupings of representatives with significant differences in reported types of interventions and in their level of reported impact. Two of the clusters were consistent with the findings in the exploratory study, identified as knowledge activism for greater emphasis on knowledge based political activity and technical-legal representation for greater emphasis on formalized technical oriented procedures and legal regulations. Knowledge activists were more likely to take on challenging interventions and they reported more impact across the full range of interventions. CONCLUSIONS: This paper provides further support for the concepts of knowledge activism and technical-legal representation when differentiating the strategic orientations and impact of worker health and safety representatives, with important implications for education, political support and recruitment.

Cellular responses to extracellular guidance cues.

Extracellular guidance cues have a key role in orchestrating cell behaviour. They can take many forms, including soluble and cell-bound ligands (proteins, lipids, peptides or small molecules) and insoluble matrix substrates, but to act as guidance cues, they must be presented to the cell in a spatially restricted manner. Cells that recognize such cues respond by activating intracellular signal transduction pathways in a spatially restricted manner and convert the extracellular information into intracellular polarity. Although extracellular cues influence a broad range of cell polarity decisions, such as mitotic spindle orientation during asymmetric cell division, or the establishment of apical-basal polarity in epithelia, this review will focus specifically on guidance cues that promote cell migration (chemotaxis), or localized cell shape changes (chemotropism).

Making narrative feedback meaningful.

BACKGROUND: Narrative written feedback given to students by faculty often fails to identify areas for improvement and recommended actions to lead to this improvement. When these elements are missing, it is challenging for students to improve and for medical schools to use narrative feedback in promotion decisions, to guide coaching plans and to pass on meaningful information to residency programs. Large-group faculty development has improved narrative written feedback, but less is known about individualised faculty development to supplement large-group sessions. To fill this gap, we built a curriculum with general and individualised faculty development to improve narrative written feedback from Internal Medicine faculty to clerkship students. APPROACH: We used Kern's steps to build a curriculum with general and individualised one-on-one faculty development to improve the problem of inadequate narrative written feedback. We used a novel narrative feedback rubric for pre and post-intervention faculty scores. RESULTS/FINDINGS/EVALUATION: Through general and individualised one-on-one faculty development with peer comparison scores, we were able to improve narrative written feedback from 3.7/6 to 4.6/6, for an increase of 23%. IMPLICATIONS: We found our faculty development program effective in improving feedback and was easy to implement. Our rubric was easy to use, and faculty were receptive to feedback in one-on-one meetings. We plan to extend this work locally to other divisions/departments and into graduate medical education; it should also be easily extended to other medical disciplines or health professions.

Thiamine-responsive megaloblastic anaemia in a young adult with acute pancytopenia.

Thiamine-responsive megaloblastic anaemia (TRMA) is a rare autosomal recessive disorder characterised by the clinical triad of megaloblastic anaemia, sensorineural hearing loss and diabetes mellitus (DM) in young patients. We present a case of a young man with type 1 DM who presented with pancytopenia of unclear aetiology, initially attributed to a COVID-19 infection. After obtaining a bone marrow biopsy and pursuing genetic testing, two pathogenic variants of the SLC19A2 gene consistent with TRMA were discovered in this patient. Treatment with 100 mg of thiamine oral supplementation daily led to the complete resolution of his pancytopenia. It is important to consider a genetic cause of pancytopenia in a young person. Early recognition and diagnosis of TRMA can be life-altering given early treatment can reduce insulin requirements and resolve anaemia.

Do acting interns need residents? A comparison of acting intern experience on hospital medicine resident versus nonresident teams.

BACKGROUND: The clinical demands for hospitalist groups have grown at academic medical centers, without similar growth of teaching opportunities for faculty. Traditional resident teaching teams are often crowded with learners which can limit acting intern (or subintern) patient encounters. Medical students are often placed on nonresident teaching teams, although there are few studies on learner experience on a nonresident teaching team model. METHODS: To address these concerns, we created two nonresident teaching teams composed of one attending and two acting interns. We compared acting intern experience on the nonresident teaching teams to the traditional resident teams to determine if there were significant differences in student experience by reviewing course evaluation data on the two team models. RESULTS: Of the 276 students who completed the Internal Medicine Acting Internship from 2019 to 2023, 224 students (81%) completed the course evaluation. The course was highly rated, and the ratings were similar in both models demonstrating that the nonresident teaching team model is an effective option for acting interns. CONCLUSION: The nonresident teaching team model can offload crowded teaching teams, add additional acting intern experiences, and add teaching opportunities for hospital medicine attendings.

Rac1-dependent collective cell migration is required for specification of the anterior-posterior body axis of the mouse.

Cell migration and cell rearrangements are critical for establishment of the body plan of vertebrate embryos. The first step in organization of the body plan of the mouse embryo, specification of the anterior-posterior body axis, depends on migration of the anterior visceral endoderm from the distal tip of the embryo to a more proximal region overlying the future head. The anterior visceral endoderm (AVE) is a cluster of extra-embryonic cells that secretes inhibitors of the Wnt and Nodal pathways to inhibit posterior development. Because Rac proteins are crucial regulators of cell migration and mouse Rac1 mutants die early in development, we tested whether Rac1 plays a role in AVE migration. Here we show that Rac1 mutant embryos fail to specify an anterior-posterior axis and, instead, express posterior markers in a ring around the embryonic circumference. Cells that express the molecular markers of the AVE are properly specified in Rac1 mutants but remain at the distal tip of the embryo at the time when migration should take place. Using tissue specific deletions, we show that Rac1 acts autonomously within the visceral endoderm to promote cell migration. High-resolution imaging shows that the leading wild-type AVE cells extend long lamellar protrusions that span several cell diameters and are polarized in the direction of cell movement. These projections are tipped by filopodia-like structures that appear to sample the environment. Wild-type AVE cells display hallmarks of collective cell migration: they retain tight and adherens junctions as they migrate and exchange neighbors within the plane of the visceral endoderm epithelium. Analysis of mutant embryos shows that Rac1 is not required for intercellular signaling, survival, proliferation, or adhesion in the visceral endoderm but is necessary for the ability of visceral endoderm cells to extend projections, change shape, and exchange neighbors. The data show that Rac1-mediated epithelial migration of the AVE is a crucial step in the establishment of the mammalian body plan and suggest that Rac1 is essential for collective migration in mammalian tissues.

Par6B and atypical PKC regulate mitotic spindle orientation during epithelial morphogenesis.

Cdc42 plays an evolutionarily conserved role in promoting cell polarity and is indispensable during epithelial morphogenesis. To further investigate the role of Cdc42, we have used a three-dimensional matrigel model, in which single Caco-2 cells develop to form polarized cysts. Using this system, we previously reported that Cdc42 controls mitotic spindle orientation during cell division to correctly position the apical surface in a growing epithelial structure. In the present study, we have investigated the specific downstream effectors through which Cdc42 controls this process. Here, we report that Par6B and its binding partner, atypical protein kinase C (aPKC), are required to regulate Caco-2 morphogenesis. Depletion or inhibition of Par6B or aPKC phenocopies the loss of Cdc42, inducing misorientation of the mitotic spindle, mispositioning of the nascent apical surface, and ultimately, the formation of aberrant cysts with multiple lumens. Mechanistically, Par6B and aPKC function interdependently in this context. Par6B localizes to the apical surface of Caco-2 cysts and is required to recruit aPKC to this compartment. Conversely, aPKC protects Par6B from proteasomal degradation, in a kinase-independent manner. In addition, we report that depletion or inhibition of aPKC induces robust apoptotic cell death in Caco-2 cells, significantly reducing both cyst size and number. Cell survival and apical positioning depend upon different thresholds of aPKC expression, suggesting that they are controlled by distinct downstream pathways. We conclude that Par6B and aPKC control mitotic spindle orientation in polarized epithelia and, furthermore, that aPKC coordinately regulates multiple processes to promote morphogenesis.

Rho family GTPases.

Rho GTPases comprise a family of molecular switches that control signal transduction pathways in eukaryotic cells. A conformational change induced upon binding GTP promotes an interaction with target (effector) proteins to generate a cellular response. A highly conserved function of Rho GTPases from yeast to humans is to control the actin cytoskeleton, although, in addition, they promote a wide range of other cellular activities. Changes in the actin cytoskeleton drive many dynamic aspects of cell behaviour, including morphogenesis, migration, phagocytosis and cytokinesis, and the dysregulation of Rho GTPases is associated with numerous human diseases and disorders.

Cdc42 and noncanonical Wnt signal transduction pathways cooperate to promote cell polarity.

Scratch-induced disruption of cultured monolayers induces polarity in front row cells that can be visualized by spatially localized polymerization of actin at the front of the cell and reorientation of the centrosome/Golgi to face the leading edge. We previously reported that centrosomal reorientation and microtubule polarization depend on a Cdc42-regulated signal transduction pathway involving activation of the Par6/aPKC complex followed by inhibition of GSK-3beta and accumulation of the adenomatous polyposis coli (APC) protein at the plus ends of leading-edge microtubules. Using monolayers of primary rodent embryo fibroblasts, we show here that dishevelled (Dvl) and axin, two major components of the Wnt signaling pathway are required for centrosome reorientation and that Wnt5a is required for activation of this pathway. We conclude that disruption of cell-cell contacts leads to the activation of a noncanonical Wnt/dishevelled signal transduction pathway that cooperates with Cdc42/Par6/aPKC to promote polarized reorganization of the microtubule cytoskeleton.

Practice Doesn't Make Perfect: Clinical Experience With Procedures Does Not Correlate Well With Competence in Third-Year Medical Students.

OBJECTIVE: There is limited data available about factors which promote competence with procedures in medical students. Specifically, the relationship between procedural clinical experience and performance on an assessment is unclear. We sought to determine whether a correlation exists between the amount and type of clinical experience with a procedure and student performance on a standardized assessment of that procedure. DESIGN: Faculty performed standardized assessments of third-year medical students on ten procedures using simulation. We prospectively surveyed students about 3 types of experience (performed, observed, and simulated) with these procedures during their clerkships. We then analyzed whether a correlation exists between student experience and their competency assessment scores using Pearson's correlation. SETTING/PARTICIPANTS: Third-year medical students at the University of Kentucky College of Medicine. RESULTS: In 2018 to 2019, 131 students were assessed on procedural competency with 10 failures. One hundred and twenty students (91.6%) completed the clinical experience survey. Correlations between types of experience and competency scores were small to moderate, with only 5 of 40 being significant. We found no correlation between experience having performed a procedure and competency score. CONCLUSIONS: Overall, we did not find convincing evidence of a correlation between experience with procedures during clerkships and performance on a competency assessment. This suggests other factors may be contributing to procedural competence, which has implications for how educators should develop procedural competence in students.

Cell polarity: Par6, aPKC and cytoskeletal crosstalk.

Par6 and atypical protein kinase C are key players in the establishment of cell polarity. First discovered in Caenorhabditis elegans, the function of this protein complex is conserved in all multicellular organisms. Recent work is beginning to throw light on how it converts information generated by extracellular cues into intracellular asymmetry.