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Beneficial mutations that arise in an evolving asexual population may compete or interact in ways that alter the overall rate of adaptation through mechanisms such as clonal or functional interference. The application of multiple selective pressures simultaneously may allow for a greater number of adaptive mutations, increasing the opportunities for competition between selectively advantageous alterations, and thereby reducing the rate of adaptation. We evolved a strain of Saccharomyces cerevisiae that could not produce its own histidine or uracil for ~500 generations under one or three selective pressures: limitation of the concentration of glucose, histidine, and/or uracil in the media. The rate of adaptation was obtained by measuring evolved relative fitness using competition assays. Populations evolved under a single selective pressure showed a statistically significant increase in fitness on those pressures relative to the ancestral strain, but the populations evolved on all three pressures did not show a statistically significant increase in fitness over the ancestral strain on any single pressure. Simultaneously limiting three essential nutrients for a population of S. cerevisiae effectively slows the rate of evolution on any one of the three selective pressures applied, relative to the single selective pressure cases. We identify possible mechanisms for fitness changes seen between populations evolved on one or three limiting nutrient pressures by high‐throughput sequencing. Adding multiple selective pressures to evolving disease like cancer and infectious diseases could reduce the rate of adaptation and thereby may slow disease progression, prolong drug efficacy and prevent deaths. [ABSTRACT FROM AUTHOR]

Background: Red blood cell (RBC) alloimmunization is a concern for patients who receive multiple or chronic transfusions. Alloimmunization prevalence in transfused patients with bone marrow failure syndrome (BMFS) is unknown. This study aimed to determine physician practice for RBC antigen matching, immunization rates, and antibody specificities in patients with BMFS.Study Design and Methods: The clinical records of all patients with BMFS seen at the Children's Hospital of Philadelphia between 2001 and 2015 were reviewed. Immunization rate was determined per 100 units transfused.Results: ABO/D, C, E, and K (CEK) RBC matching was requested for 21.8% of patients. A total of 3782 RBC units were transfused to 87 patients, of which 2551 (67.5%) were CEK matched and 1231 (32.5%) were ABO/D only matched. The majority of units transfused to patients on a chronic transfusion regimen were CEK matched (89.6% of 2728 units). No anti-C, -E, or -K antibodies formed in any patient during the 14-year study period. Two alloantibodies and two autoantibodies formed, resulting in a rate of 0.05 alloantibodies and 0.05 autoantibodies per 100 units transfused. The prevalence of alloimmunization was 2.3%.Conclusion: The rate and prevalence of RBC alloimmunization were low in patients with BMFS. CEK matching avoided alloimmunization to these antigens in chronically transfused patients. [ABSTRACT FROM AUTHOR]

BRAF inhibitors improve melanoma patient survival, but resistance invariably develops. Here we report the discovery of a novel BRAF mutation that confers resistance to PLX4032 employing whole-exome sequencing of drug-resistant BRAF V600K melanoma cells. We further describe a new screening approach, a genome-wide piggy Bac mutagenesis screen that revealed clinically relevant aberrations ( N-terminal BRAF truncations and CRAF overexpression). The novel BRAF mutation, a Leu505 to His substitution ( BRAF L505H), is the first resistance-conferring second-site mutation identified in BRAF mutant cells. The mutation replaces a small nonpolar amino acid at the BRAF- PLX4032 interface with a larger polar residue. Moreover, we show that BRAF L505H, found in human prostate cancer, is itself a MAPK-activating, PLX4032-resistant oncogenic mutation. Lastly, we demonstrate that the PLX4032-resistant melanoma cells are sensitive to novel, next-generation BRAF inhibitors, especially the 'paradox-blocker' PLX8394, supporting its use in clinical trials for treatment of melanoma patients with BRAF-mutations. [ABSTRACT FROM AUTHOR]