Dasatinib inhibits CXCR4 signaling in chronic lymphocytic leukaemia cells and impairs migration towards CXCL12

Chemokines and their ligands play a critical role in enabling chronic lymphocytic leukaemia (CLL) cells access to protective microenvironmental niches within tissues, ultimately resulting in chemoresistance and relapse: disruption of these signaling pathways has become a novel therapeutic approach in CLL. The tyrosine kinase inhibitor dasatinib inhibits migration of several cell lines from solid-organ tumours, but effects on CLL cells have not been reported. We studied the effect of clinically achievable concentrations of dasatinib on signaling induced by the chemokine CXCL12 through its' receptor CXCR4, which is highly expressed on CLL cells. Dasatinib pre-treatment inhibited Akt and ERK phosphorylation in CLL cells upon stimulation with CXCL12. Dasatinib also significantly diminished the rapid increase in actin polymerisation observed in CLL cells following CXCL12 stimulation. Moreover, the drug significantly inhibited chemotaxis in a transwell assay, and reduced the percentage of cells able to migrate beneath a CXCL12-expressing murine stromal cell line. Dasatinib also abrogated the anti-apoptotic effect of prolonged CXCL12 stimulation on cultured CLL cells. These data suggest that dasatinib, akin to other small molecule kinase inhibitors targeting the B-cell receptor signaling pathway, may redistribute CLL cells from protective tissue niches to the peripheral blood, and support the investigation of dasatinib in combination strategies

ruvA Mutants that resolve Holliday junctions but do not reverse replication forks

RuvAB and RuvABC complexes catalyze branch migration and resolution of Holliday junctions (HJs) respectively. In addition to their action in the last steps of homologous recombination, they process HJs made by replication fork reversal, a reaction which occurs at inactivated replication forks by the annealing of blocked leading and lagging strand ends. RuvAB was recently proposed to bind replication forks and directly catalyze their conversion into HJs. We report here the isolation and characterization of two separation-of-function ruvA mutants that resolve HJs, based on their capacity to promote conjugational recombination and recombinational repair of UV and mitomycin C lesions, but have lost the capacity to reverse forks. In vivo and in vitro evidence indicate that the ruvA mutations affect DNA binding and the stimulation of RuvB helicase activity. This work shows that RuvA's actions at forks and at HJs can be genetically separated, and that RuvA mutants compromised for fork reversal remain fully capable of homologous recombination

Teamlet Structure and Early Experiences of Medical Home Implementation for Veterans

BACKGROUND: High functioning interdisciplinary primary care teams are a critical component of the patient-centered medical home. In 2010, the Veterans Administration (VA) implemented a medical home model termed the Patient Aligned Care Teams (PACT), with reorganization of staff into small teams (“teamlets”) as a core feature. OBJECTIVE: To examine the early experiences of primary care personnel as they assumed new roles through reorganization into teamlets. DESIGN: Convergent mixed methods study design involving semi-structured interviews and a survey; data were collected in 2011 and 2012. PARTICIPANTS: We interviewed 41 frontline teamlet members (i.e., primary care physicians and staff) from three practices that were part of a PACT demonstration laboratory and examined clinician and staff survey data from 22 practices. MAIN MEASURES: Semi-structured interview guide and clinician and staff survey questions covering the following domains: teamlet formation and structure, within-teamlet communication, cross-coverage, role changes, teamlet training, impact on Veterans, and leadership facilitation and support. KEY RESULTS: Respondents had limited input into teamlet structure and indicated limited training on the PACT initiative. Guidelines delineating each teamlet member’s roles and responsibilities were emphasized as important needs. Chronic understaffing also contributed to implementation challenges and territorial attitudes surfaced when cross-coverage was not clear. In addition, several core features of VA’s medical home transformation were not fully implemented by teamlet members. Most also reported limited guidance and feedback from leadership. Despite these challenges, teamlet-based care was perceived to have a positive impact on Veterans’ experiences of primary care and also resulted in improved communication among staff. CONCLUSIONS: The PACT teamlet model holds much promise for improving primary care at the VA. However, more comprehensive training, improving the stability of teamlets, developing clear cross-coverage policies, and better defined teamlet member responsibilities are important areas in need of attention by VA leadership. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11606-013-2680-1) contains supplementary material, which is available to authorized users