Evaluation Of Resistance Mechanisms Research Articles

Bioremediation of Aquatic Environments Contaminated with Heavy Metals: A Review of Mechanisms, Solutions and Perspectives

The degradation of water resources is related to anthropic actions such as rapid urbanization and industrial and agricultural activities with inefficient land use and occupation management. Water pollution caused by organic and inorganic contaminants represents a current challenge for researchers and humanity. One of the techniques used to remove pollutants from aquatic environments is bioremediation, through the metabolism of living organisms, and especially phytoremediation, with plants as a decontamination agent. Aiming to demonstrate the current mechanisms, solutions, and perspectives regarding bioremediation, and especially phytoremediation in aquatic environments, a literature review was conducted, highlighting the following subjects: heavy metals as contaminants, phytoremediation, evaluation of resistance mechanisms, removal of heavy metals by microorganisms and biofilters of the artificial floating islands type. From the literature research carried out, it can be concluded that alternatives such as macrophyte plants have proved to be an effective and efficient alternative with a high potential for removal of contaminants in aquatic environments, including concomitantly with microorganisms. There was no mechanism well-defined for specific absorption of heavy metals by plants; however, some results can indicate that if there was sporadic contamination with some contaminants, the plants can be indicators with some adsorption and absorption, even with low concentration in the watercourse by the moment of the evaluation. It is necessary to study bioremediation methods, resistance mechanisms, tolerance, and removal efficiencies for each biological agent chosen. Within the bioremediation processes of aquatic environments, the use of macrophyte plants with a high capacity for phytoremediation of metals, used combined with bioremediating microorganisms, such as biofilters, is an interesting perspective to remove contaminants.

Complete evaluation of resistance mechanisms to first-line osimertinib requires tissue biopsy.

e21154 Background: Osimertinib (osi) is the preferred 1st line (1L) therapy for patients (pts) with EGFR-mutant NSCLC, but acquired resistance is universal. Identification of mechanisms of resistance (MoR) to 1L osi can inform subsequent treatment strategies. Here, we report MoRs identified at our institution from tissue and/or liquid biopsy (bx) upon 1L osi progression. Methods: We included pts seen at MGH with advanced EGFR+ NSCLC who had tissue and/or liquid bx (for ctDNA analysis) obtained at progression on 1L osi. Molecular testing was performed using local next-generation sequencing (NGS) and, when available, MET/ EGFR FISH. We retrospectively collected clinical characteristics, tissue histology and NGS results. Results: 54 pts (38 Female; median age 61 yrs) had tissue (n = 35) and/or liquid (n = 32) bx upon progression on 1L osi between November 2016-January 2022. 13/54 pts had both tissue and ctDNA testing. Primary EGFR mutations included del19 (32), L858R (16) and other (6). Median time from osi start to 1st resistance bx was 12.3 mos (range, 1-37). MoRs are summarized in the table. Among 35 pts with tissue bx, histologic transformations (trans) were the most common MoR, seen in 23% pts, including both small cell histology (tSCLC; 5/35), squamous histology (tSqCC; 2/35) and 1 pt with both SCLC + SqCC features in one bx. Among 5 pts with tSCLC and pre-trans NGS, only 2 had baseline TP53/RB1 loss. MET amp was seen in 20% tissue (including one with tSqCC) and secondary EGFR mutations in 9%; 43% of tissue bx had no identified MoR. Among 32 pts with ctDNA NGS, secondary EGFR mutations (16%) were the most prevalent MoR, with MET amp seen in 13%. 65% pts had no MoR by ctDNA. 6/13 pts with both tissue and ctDNA had concordant findings (MET amp-2, EGFR L718Q – 1; No MoR - 3). As expected, the 2 pts with tSCLC had no MoR in ctDNA. In 2 cases, MET amp was seen in tissue but not ctDNA; the converse was true in 1 pt. Conclusions: Histologic transformations were the most common MoR to first-line osimertinib accounting for 23% tissue biopsies and, in 3/5 pts, occurred in the absence of the known risk factor of baseline TP53/RB1 loss. In this small cohort, MET amp was more commonly seen in tissue than in ctDNA, and 63% of liquid biopsies showed no detectable MoR. Our findings suggest that tissue biopsy is critical for complete evaluation of MoRs in pts progressing on first line osimertinib, and that tissue and ctDNA may be complementary.[Table: see text]

BRD4 bimodal binding at promoters and drug-induced displacement at Pol II pause sites associates with I-BET sensitivity

BackgroundDeregulated transcription is a major driver of diseases such as cancer. Bromodomain and extra-terminal (BET) proteins (BRD2, BRD3, BRD4 and BRDT) are chromatin readers essential for maintaining proper gene transcription by specifically binding acetylated lysine residues. Targeted displacement of BET proteins from chromatin, using BET inhibitors (I-BETs), is a promising therapy, especially for acute myeloid leukemia (AML), and evaluation of resistance mechanisms is necessary to optimize the clinical efficacy of these drugs.ResultsTo uncover mechanisms of intrinsic I-BET resistance, we quantified chromatin binding and displacement for BRD2, BRD3 and BRD4 after dose response treatment with I-BET151, in sensitive and resistant in vitro models of leukemia, and mapped BET proteins/I-BET interactions genome wide using antibody- and compound-affinity capture methods followed by deep sequencing. The genome-wide map of BET proteins sensitivity to I-BET revealed a bimodal pattern of binding flanking transcription start sites (TSSs), in which drug-mediated displacement from chromatin primarily affects BRD4 downstream of the TSS and prolongs the pausing of RNA Pol II. Correlation of BRD4 binding and drug-mediated displacement at RNA Pol II pause sites with gene expression revealed a differential behavior of sensitive and resistant tumor cells to I-BET and identified a BRD4 signature at promoters of sensitive coding and non-coding genes.ConclusionsWe provide evidence that I-BET-induced shift of Pol II pausing at promoters via displacement of BRD4 is a determinant of intrinsic I-BET sensitivity. This finding may guide pharmacological treatment to enhance the clinical utility of such targeted therapies in AML and potentially other BET proteins-driven diseases.

Epidermal growth factor receptor T790M testing in progressed lung cancer: A review of sensitive methods for analysis of tissue and liquid biopsy samples.

Lung cancer is one of the major causes of mortality worldwide and is on the rise in India. The identification of epidermal growth factor receptor (EGFR) mutations in nonsmall cell lung cancer (NSCLC) has paved the way for personalized therapy in lung cancer with EGFR-tyrosine kinase inhibitors (TKIs). Despite the proven efficacy of EGFR-TKIs in patients harboring EGFR mutations, their clinical utility is limited by the development of acquired resistance mechanisms by the tumor cells. T790M mutation accounts for 60% of all resistance mechanisms to EGFR TKIs and is responsible for treatment failure with first- and second-generation TKIs. With the development of novel therapeutic agents such as osimertinib to overcome this resistance mechanism, it is essential to detect patients harboring T790M mutation. There are several limitations with the use of tissue biopsy specimens for molecular testing such as poor quality and quantity of sample, tumor heterogeneity, occurrence of complications, and issues with repeat biopsy. Liquid biopsy offers a noninvasive approach that can be used for diagnostic purposes as well as for monitoring treatment response and evaluation of resistance mechanisms. This review focuses on the methods for molecular testing of tissue and liquid biopsy specimens for EGFR mutations, particularly EGFR T790M mutation.

BET inhibitor resistance emerges from leukaemia stem cells.

Bromodomain and extra terminal protein (BET) inhibitors are first-in-class targeted therapies that deliver a new therapeutic opportunity by directly targeting bromodomain proteins that bind acetylated chromatin marks. Early clinical trials have shown promise, especially in acute myeloid leukaemia, and therefore the evaluation of resistance mechanisms is crucial to optimize the clinical efficacy of these drugs. Here we use primary mouse haematopoietic stem and progenitor cells immortalized with the fusion protein MLL-AF9 to generate several single-cell clones that demonstrate resistance, in vitro and in vivo, to the prototypical BET inhibitor, I-BET. Resistance to I-BET confers cross-resistance to chemically distinct BET inhibitors such as JQ1, as well as resistance to genetic knockdown of BET proteins. Resistance is not mediated through increased drug efflux or metabolism, but is shown to emerge from leukaemia stem cells both ex vivo and in vivo. Chromatin-bound BRD4 is globally reduced in resistant cells, whereas the expression of key target genes such as Myc remains unaltered, highlighting the existence of alternative mechanisms to regulate transcription. We demonstrate that resistance to BET inhibitors, in human and mouse leukaemia cells, is in part a consequence of increased Wnt/β-catenin signalling, and negative regulation of this pathway results in restoration of sensitivity to I-BET in vitro and in vivo. Together, these findings provide new insights into the biology of acute myeloid leukaemia, highlight potential therapeutic limitations of BET inhibitors, and identify strategies that may enhance the clinical utility of these unique targeted therapies.

Modelling Resistance to Emerging Epigenetic Therapies

The BET inhibitors are first-in-class, epigenetic targeted therapies that deliver a new therapeutic paradigm by directly targeting protein-protein interactions at chromatin. Early clinical trials have shown significant promise, especially in AML, suggesting that these compounds are likely to form an important component of future anti-cancer regimens. Therapeutic resistance is an inevitable consequence of most cancer therapies, therefore the evaluation of resistance mechanisms is of utmost importance in order to optimize the clinical utility of this novel class of drugs.Using primary murine stem and progenitor cells immortalized with MLL-AF9, we have developed a novel approach to generate over 20 clones stably resistant to the prototypical BET inhibitor, IBET. Resistance has been established at >IC90 of the parental cell line. In parallel, we have maintained matched vehicle treated clones in addition to the parental cell line. Resistant clones maintain their clonogenic capacity in IBET and are also impervious to IBET induced cell-cycle arrest and apoptosis. Resistance to IBET confers cross-resistance to other chemically distinct BET inhibitors such as JQ1 and also resistance to genetic knockdown of BET proteins. Moreover, resistance is stably maintained across subsequent cell generations in the absence of ongoing selective pressure.Resistance is not mediated through increased drug efflux or metabolism but is demonstrated to emerge from the leukemia stem cell (LSC) compartment. Resistant clones display an immature phenotype (c-kithi/Gr1-/CD11b-) and functionally, exhibit increased clonogenic capacity in vitro and markedly shorter disease latency following primary syngeneic transplantation (Figure A, B and C). Importantly, resistant clones maintain their resistance to IBET therapy in vivo.We will present data gleaned from exome capture sequencing, ChIP-seq and RNA-seq, to demonstrate the underlying molecular mechanisms of resistance to epigenetic therapies, including genetic changes, molecular events at chromatin and the upregulation of compensatory pathways that will inform future combination therapies to obviate and/or overcome BET inhibitor resistance.In summary, we have utilized a primary murine model of MLL leukemia to derive over 20 individual clones that are resistant to BET inhibition. Our data is consistent with resistance emerging from the LSC population. This data will allow us to develop rational drug combinations to overcome resistance and enhance the therapeutic efficacy of emerging epigenetic therapies. Furthermore, our data provides novel insights into the biology of AML and provides an unprecedented opportunity to study leukemia stem cells and develop therapeutic strategies to eradicate them. [Display omitted] DisclosuresLugo:GlaxoSmithKline: Employment. Jeffrey:GlaxoSmithKline: Employment. Gregory:GlaxoSmithKline: Employment. Prinjha:GlaxoSmithKline: Employment.

Erratum to: Evaluation of resistance mechanisms and serotype and genotype distributions of macrolide-resistant strains in clinical isolates of Streptococcus pneumoniae in Aydın, Turkey

Erratum to: Evaluation of resistance mechanisms and serotype and genotype distributions of macrolide-resistant strains in clinical isolates of Streptococcus pneumoniae in Aydın, Turkey

Evaluation of resistance mechanisms and serotype and genotype distributions of macrolide-resistant strains in clinical isolates of Streptococcus pneumonia in Aydın, Turkey

Macrolide resistance mechanisms in 89 Streptococcus pneumoniae strains isolated from several clinical samples between February 2007 and May 2009 were investigated. Erythromycin resistance was noted in 35 (40%) S. pneumoniae strains. In these strains, the most frequent resistance phenotype was cMLS(B) (74%), and the most frequent resistance genotype was ermB (82%). Both ermB and mefA genes were positive in 20% of macrolide-resistant strains. While no resistance to vancomycin, linezolid and telithromycin was noted in 89 S. pneumoniae strains, 12 (13%) strains were penicillin resistant, 26 (30%) strains were clindamycin resistant, 35 (40%) were azithromycin resistant, 32 (36%) strains were tetracycline resistant, and 1 (1%) strain was levofloxacin resistant. The serotype distribution of 35 macrolide-resistant S. pneumoniae strains revealed that the most frequent serotype was serogroup 19 (45%). Multidrug resistance was present in 19 (86%) of 22 strains carrying only the ermB resistance gene. No clonal dissemination was noted in the macrolide-resistant pneumococcal strains. These findings suggest that macrolide resistance rates, resistance phenotype and genotype, as well as resistant serotypes of S. pneumoniae strains should be continuously monitored in our country.