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Etoposide is used to treat a wide range of malignant cancers, including acute myeloid leukemia (AML) in children. Despite the use of intensive chemotherapeutic regimens containing etoposide, a significant proportion of pediatric patients with AML become resistant to treatment and relapse, leading to poor survival. This poses a pressing clinical challenge to identify mechanisms underlying drug resistance to enable effective pharmacologic targeting. We performed a genome-wide CRISPR/Cas9 synthetic-lethal screening to identify functional modulators of etoposide response in leukemic cell line and integrated results from CRISPR-screen with gene expression and clinical outcomes in pediatric patients with AML treated with etoposide-containing regimen. Our results confirmed the involvement of well-characterized genes, including TOP2A and ABCC1, as well as identified novel genes such as RAD54L2, PRKDC, and ZNF451 that have potential to be novel drug targets. This study demonstrates the ability for leveraging CRISPR/Cas9 screening in conjunction with clinically relevant endpoints to make meaningful discoveries for the identification of prognostic biomarkers and novel therapeutic targets to overcome treatment resistance.

Medication-related osteonecrosis of the jaw (MRONJ) is a rare but serious adverse drug reaction. Our previous whole-exome sequencing study found SIRT1 intronic region single-nucleotide polymorphism (SNP) rs7896005 to be associated with MRONJ in cancer patients treated with intravenous (iv) bisphosphonates (BPs). This study aimed to identify causal variants for this association. In silico analyses identified three SNPs (rs3758391, rs932658, and rs2394443) in the SIRT1 promoter region that are in high linkage disequilibrium (r2 > 0.8) with rs7896005. To validate the association between these SNPs and MRONJ, we genotyped these three SNPs on the germline DNA from 104 cancer patients of European ancestry treated with iv BPs (46 cases and 58 controls). Multivariable logistic regression analysis showed the minor alleles of these three SNPs were associated with lower odds for MRONJ. The odds ratios (95% confidence interval) and p values were 0.351 (0.164-0.751; p = 0.007) for rs3758391, 0.351 (0.164-0.751; p = 0.007) for rs932658, and 0.331 (0.157-0.697; p = 0.0036) for rs2394443, respectively. In the reporter gene assays, constructs containing rs932658 with variant allele A had higher luciferase activity than the reference allele, whereas constructs containing SNP rs3758391 and/or rs2394443 did not significantly affect activity. These results indicate that the promoter SNP rs932658 regulates the expression of SIRT1 and presumably lowers the risk of MRONJ by increasing SIRT1 expression. © 2020 American Society for Bone and Mineral Research (ASBMR).

Recently, mRNA-expression signature enriched in LSCs was used to create a 17-gene leukemic stem cell (LSC17) score predictive of prognosis in adult AML. By fitting a Cox-LASSO regression model to the clinical outcome and gene-expression levels of LSC enriched genes in 163 pediatric participants of the AML02 multi-center clinical trial (NCT00136084), we developed a six-gene LSC score of prognostic value in pediatric AML (pLSC6). In the AML02 cohort, the 5-year event-free survival (EFS) of patients within low-pLSC6 group (n = 97) was 78.3 (95% CI = 70.5–86.9%) as compared with 34.5(95% CI = 24.7–48.2 %) in patients within high-pLSC6 group (n = 66 subjects), p

The COVID-19 pandemic has resulted in 153 million infections and 3.2 million deaths as of May 2021. While effective vaccines are being administered globally, there is still a great need for antiviral therapies as potentially antigenically distinct SARS-CoV-2 variants continue to emerge across the globe. Viruses require host factors at every step in their life cycle, representing a rich pool of candidate targets for antiviral drug design. To identify host factors that promote SARS-CoV-2 infection with potential for broad-spectrum activity across the coronavirus family, we performed genome-scale CRISPR knockout screens in two cell lines (Vero E6 and HEK293T ectopically expressing ACE2) with SARS-CoV-2 and the common cold-causing human coronavirus OC43. While we identified multiple genes and functional pathways that have been previously reported to promote human coronavirus replication, we also identified a substantial number of novel genes and pathways. Of note, host factors involved in cell cycle regulation were enriched in our screens as were several key components of the programmed mRNA decay pathway. Finally, we identified novel candidate antiviral compounds targeting a number of factors revealed by our screens. Overall, our studies substantiate and expand the growing body of literature focused on understanding key human coronavirus-host cell interactions and exploit that knowledge for rational antiviral drug development.One Sentence SummaryGenome-wide CRISPR screens identified host factors that promote human coronavirus infection, revealing novel antiviral drug targets.

Cytarabine has been an integral part of acute myeloid leukemia (AML) chemotherapy for over four decades. However, development of resistance and high rates of relapse is a significant impediment in successfully treating AML. We performed a genome-wide association analysis (GWAS) and identified 113 (83 after adjusting for Linkage Disequilibrium) SNPs associated with in vitro cytarabine chemosensitivity of diagnostic leukemic cells from a cohort of 50 pediatric AML patients (p

Acute myeloid leukemia (AML) may be an epigenetically-driven malignancy because it harbors fewer genomic mutations than other cancers. In recent studies of AML in adults, DNA methylation patterns associate with clinical risk groups and prognosis. However, thorough evaluations of methylation in pediatric AML have not been done. Therefore, we performed an integrated analysis (IA) of the methylome and transcriptome with clinical outcome in 151 pediatric patients from the multi-center AML02 clinical trial discovery cohort. Intriguingly, reduced methylation and increased expression of DNMT3B was associated with worse clinical outcomes (IA p ≤ 10-5; q ≤ 0.002). In particular, greater DNMT3B expression associated with worse minimal residual disease (MRD; p < 10-5; q = 0.01), a greater rate of relapse or resistant disease (RR) (p = 0.00006; q = 0.06), and event-free survival (EFS; p = 0.00003; q = 0.04). Also, greater DNMT3B expression associated with greater genome-wide methylation burden (GWMB; R = 0.39; p = 10-6) and greater GWMB associated with worse clinical outcomes (IA p < 10-5). In an independent validation cohort of 132 similarly treated AAML0531 clinical trial patients, greater DNMT3B expression associated with greater GWMB, worse MRD, worse RR, and worse EFS (all p < 0.03); also, greater GWMB associated with worse MRD (p = 0.004) and EFS (p = 0.037). These results indicate that DNMT3B and GWMB may have a central role in the development and prognosis of pediatric AML.

Introduction: Despite cure rates in acute lymphoblastic leukemia (ALL) exceeding 90% in clinical trials, morbidity due to drug toxicities is high. Genetic polymorphisms can influence gene expression and activity, impacting pharmacokinetics and causing inter-individual variation in drug levels, which contributes to toxicity if levels are high or relapse if levels are low. We hypothesize that pharmacogenomic testing will identify patient specific variations in genes involved in metabolism of cytotoxic agents. This knowledge will allow clinicians to optimize therapy by providing pharmacogenomics based biomarkers related to increased toxicities. Data has shown that treatment interruptions and omissions due to toxicities affect outcomes and morbidities in children with cancer. Objective : To correlate pharmacogenomic biomarkers with toxicity phenotypes in children receiving therapy for ALL. Methods: This cross-sectional study involved subjects at a tertiary academic center (Fig. 1A). Subjects aged 1 year to 26 years with ALL treated after May 2012 were eligible. A total of 75 patients treated between 2012 and 2020 were included. Pharmacogenomic testing was performed on peripheral blood. Genomic DNA was tested for 118 single-nucleotide polymorphisms (SNP) in 55 genes for transport and metabolism of cytarabine, vincristine, methotrexate, dauno/doxorubicin, and mercaptopurine/thioguanine were analyzed using the Sequenom-based genotyping that uses MALDI-TOF based chemistry. SNPs were tested using logistic regression models for association with toxicities in additive, dominant, and recessive modes of inheritance. CTCAE v4.0 was used for grading all toxicities during the first 100 days of therapy. For endocrine (endo) and neurological (neuro) toxicities, 25 patients exhibited between grade 1-3 toxicities. For gastrointestinal (GI) toxicities, 25 patients exhibited between grade 2-3 toxicities. For hematological (heme) toxicities, 11 patients exhibited between grade 2-4 toxicities. Odds ratio and 95% confidence interval were calculated for each test and SNPs with association P-value 0, 0 or Results: For a GI toxicity score derived from 3 SNPs (TYMS-rs151264360, FPGS-rs1544105, and GSTM5-rs3754446), patients with >0 score had 79% incidence of GI toxicity (N=67) as compared to 10% in patients with score of 0 and 8% in patients with score 0; no toxicity was observed in patients with neurotoxicity score of 0 (p=4.7E-08, Fig. 1E). None of the patients with a score of Discussion: We identified germline SNPs predictive of toxicity phenotypes in a cohort of 75 subjects with ALL. The results of our multivariable SNP combination analysis suggest susceptibility to chemotherapy-induced toxicities is likely multigenic in nature. Instead of a single SNP approach, identification of combinations of mutations in drug pathways increases the robustness of predicting a patient's response to chemotherapy. Our results provide promising SNP models that can help establish clinically relevant biomarkers allowing for individualization of cancer therapy to optimize treatment for each patient. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Background and Objectives: Pseudomonas aeruginosa is the most frequent opportunistic pathogen isolated from the sputum of patients with cystic fibrosis (CF). Resistance to β -lactam antibiotics may arise from over expression of the naturally occurring AmpC cephalosporinases or acquired extended-spectrum β-lactamases (ESBL). The aim of this study was to determine the antibiotic resistance profiles as well as the prevalence of ESBL and AmpC production in clinical isolates of P. aeruginosa from CF patients in Tehran. Methods: Antibiotic resistance of 50 non-duplicate P. aeruginosa isolates was determined by the disc diffusion method. AmpC β-lactamase production was detected by the antagonism disc test and ESBL production was detected by the phenotypic confirmatory test. The presence of ESBL and AmpC genes was assessed by PCR, followed by sequencing the PCR products. Results: The antibiotic resistance rates were as follows: 22% to ceftriaxone, 20% to cefotaxime, 10% to imipenem, 8% to carbenicillin and 6% to ticarcillin, 4% each to cefepime, tobramycin, amikacin and aztreonam and 2% to each piperacilin, meropenem and ceftazidime. AmpC production was observed in 47 isolates (94%) and ESBL production was observed in one isolate (2%). PCR results showed that all isolates carried the blaAmpC β-lactamase gene. One multidrug-resistant isolate carried both blaTEM and blaPER-1 genes. Conclusion: The results showed that despite the low rate of antibiotic resistance in P. aeruginosa CF isolates,the presence of multiple β-lactamases even in one isolate is alarming and can complicate the already difficult treatment of chronic infections in the lungs of CF patients.

Pancreatic ductal adenocarcinoma (PDAC) clinically has a very poor prognosis. No small molecule is available to reliably achieve cures. Meisoindigo is chemically related to the natural product indirubin and showed substantial efficiency in clinical chemotherapy for CML in China. However, its effect on PDAC is still unknown. Our results showed strong anti-proliferation effect of meisoindigo on gemcitabine-resistant PDACs. Using a recently established primary PDAC cell line, called Jopaca-1 with a larger CSCs population as model, we observed a reduction of CD133+ and ESA+/CD44+/CD24+ populations upon treatment and concomitantly a decreased expression of CSC-associated genes, and reduced cellular mobility and sphere formation. Investigating basic cellular metabolic responses, we detected lower oxygen consumption and glucose uptake, while intracellular ROS levels increased. This was effectively neutralized by the addition of antioxidants, indicating an essential role of the cellular redox balance. Further analysis on energy metabolism related signaling revealed that meisoindigo inhibited LKB1, but activated AMPK. Both of them were involved in cellular apoptosis. Additional in situ hybridization in tissue sections of PDAC patients reproducibly demonstrated co-expression and -localization of LKB1 and CD133 in malignant areas. Finally, we detected that CD133+/CD44+ were more vulnerable to meisoindigo, which could be mimicked by LKB1 siRNAs. Our results provide the first evidence, to our knowledge, that LKB1 sustains the CSC population in PDACs and demonstrate a clear benefit of meisoindigo in treatment of gemcitabine-resistant cells. This novel mechanism may provide a promising new treatment option for PDAC.

[This corrects the article DOI: 10.18632/oncotarget.25475.].

Background: The emergence and spread of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae are recognized as a major clinical problem and a public health challenge. Enterobacteria are transient colonizers of lungs affected by cystic fibrosis (CF). Klebsiella pneumoniae has been shown to cause chronic obstructive pulmonary infections. Objectives: We aimed to determine the antibiotic resistance profile and ESBL production in K. pneumoniae isolates from Iranian patients with CF. Methods: Sixteen K. pneumoniae strains were isolated from the sputum samples of 98 pediatric CF patients at Mofid children’s hospital in Tehran, Iran. Antibiotic susceptibility was determined via disc diffusion, and ESBL phenotype was detected by double disc synergy test (DDST). β-lactamase genes, including TEM, SHV, CTX-M, and OXA genes, were detected using polymerase chain reaction (PCR) and confirmed by sequencing the PCR products. Finally, genetic fingerprints of the isolates were determined via random amplified polymorphic DNA (RAPD)-PCR method. Results: Ten isolates had ESBL phenotypes, all of which contained non-ESBL blaTEM-1 genes. Seven isolates harbored blaCTX-M-15 genes (ESBL genes), five of which also showed non-ESBL blaSHV-11, blaTEM-1, and blaOXA-1 genes (1 isolate with blaTEM-1 and 1 isolate with blaTEM-1 plus blaOXA-1 gene). However, PER-1 and VEB-1 β-lactamase genes were not detected. Genetic fingerprinting profiles showed heterogeneity among K. pneumoniae isolates. Conclusions: This study highlights not only the presence of multiple β-lactamases, but also the carriage of ESBL blaCTX-M-15 gene among K. pneumoniae isolates from CF patients.

Despite the use of intensive chemotherapeutic regimens containing ara-C, daunorubicin and etoposide (ADE), in combination with stem cell transplantation for high-risk group patients, approximately significant patients experience relapse. Resistant and relapsed disease remains the most prevalent forms of clinical failure in treating this disease. The current scientific challenge is to identify candidate genes that are truly essential to drug resistance and thus may be pharmacologically targeted in a clinically effective manner. The development of the CRISPR/cas9 genome editing tool has dramatically improved the capabilities for functional screening in multiple systems including AML where genome-wide drop-out screens in AML cancer cell lines identified AML-essential genes. None of the studies have unfortunately integrated the CRISPR/cas9 screening tool with patient outcome data. In this study, we have successfully performed Genome scale Crispr knock out GeCKO -CRISPR/cas9 screening using Brunello library (targeting 19,114 genes) in K562 cell lines followed by treatments with etoposide, dauno and cytarabine. We performed a large-scale transduction into ~30 x 106 cells at a low multiplicity of infection (0.3). After puromycin selection the mutant cell library was exposed in triplicate to IC30 concentration of chemotherapeutic agents for up to 18 days with collection of samples at day 4 (ara-C, dauno, etoposide) days 12 and 18 (dauno and etoposide). A vehicle-only exposure was similarly carried out for 18 days. Direct sequencing of PCR amplified sgRNA guides from the pooled cells by short read sequencing (Illumina) was used to quantify the representation of each knockout clone in the pooled population (schema shown in Fig 1). The relative enrichment/depletion of each knockout clone was determined by ratio of the abundance of each clone between two samples. The FASTX-Toolkit, was used to extract the unique sgRNA sequences which were assembled into a Burrows-Wheeler index using the Bowtie build-index function and number of uniquely aligned reads for each sgRNA were calculated. The MaGeCK algorithms was used to analyze the read count data and perform statistical comparisons. The results for the etoposide screening are shown in Fig 2, overall 17 genes showed significant association with responsiveness to etoposide at all the three different time points (4, 12 and 18 days). Further investigation of these candidate genes in AML patients treated on AML02 trial demonstrated consistent and significant association between expression levels of several genes identified in CRISPR screening and clinical outcome. Fig 3 shows a representative result for 2 of the genes identified in etoposide screening, ABCC1and RAD54L2 both were associated with etoposide resistance in CRISPR screening and concordantly high expression was associated with greater induction 1 MRD, inferior event free survival (EFS, Fig 3) and overall survival (OS) in the AML02 cohort. ABCC1 is a drug efflux transporter that has been implicated in resistance to etoposide and daunorubicin as well as has been associated with poor prognosis in AML consistent with our results. RAD54L2, is a helicase involved in DNA damage repair response pathway. Other genes of interest identified in etoposide screening with significant association with clinical endpoints as MRD, EFS and OS included TKT, involved in pentose phosphate pathway and implicated in regulation of metabolic switch in cancer. A nucleotide excision repair gene, RAD23B, implicated in breast cancer progression as well as in CML and ALL. Similarly, for daunorubicin and cytarabine CRISPR/cas9 synthetic lethal screening identified target genes of clinical relevance that will be discussed in the presentation. Our approach shows that using CRISPR/cas9 targeted synthetic lethal screening as a reliable approach to not only identify and establish genes predictive of drug resistance and poor outcome but also potential targets for novel drug development that could be used in combination with currently approved agents. Disclosures No relevant conflicts of interest to declare.

In nature, essential oils play an important role in the protection of the plants by exerting anti-bacterial, -viral, -fungal, -oxidative, -genotoxic, and free radical scavenging properties, as well as in some cases acting as insecticides. Several Satureja species are used in traditional medicine due to recognized therapeutic properties, namely anti-microbial and cytotoxic activities. The purpose of the present work was to determine the biologic activity of the essential oil of S. khuzistanica Jamzad (Lamiaceae) against four human cancer cell lines, as well as its inhibitory effects against a wide array (i.e. n = 11) of pathogenic bacteria and fungi. The essential oil was isolated by hydro-distillation and analyzed by GC-FID and GC-MS. Carvacrol (92.87%) and limonene (1.2%) were found to be the main components of the isolated oil. Anti-microbial activity of the essential oil was assessed using a disc diffusion method; an MTT cytotoxicity assay was employed to test effects of the oil on each cancer cell line. The oil exhibited considerable anti-microbial activity against the majority of the tested bacteria and fungi. The test oil also significantly reduced cell viability of Vero, SW480, MCF7, and JET 3 cells in a dose-dependent manner, with the IC50 values calculated for each cell type being, respectively, 31.2, 62.5, 125, and 125 μg/ml. Based on the findings, it is concluded that the essential oil of S. khuzistanica and its major constituents have a potential for further use in anti-bacterial and anti-cancer applications, pending far more extensive testing of toxicities in normal (i.e. primary) cells.

Several Satureja species are used in traditional medicine due to recognized therapeutic properties, namely antimicrobial and cytotoxic activities. In order to explore the potential for commercial purposes and industrial utilization of its essentiail oil, scientific studies addressing the chemical composition, the action mechanism and the toxicological safety are needed. The purpose of the present work was to determine the cytotoxic activity of the essential oil of S. sahendica Bornm. (Lamiaceae) on four human cancer cell lines as well as its inhibitory effects in vitro against 11 pathogenic bacteria and fungi. The essential oil was isolated by hydrodistillation and analyzed by the combination of capillary GC-FID and GC-MS. Thymol (40%), γ-terpinene (28%), and ρ-cymene (22%) were the main components of the essential oil. Antimicrobial activity of the essential oil according to the disk diffusion method and minimum inhibitory concentration value and the in vitro toxicological study based on the MTT cytotoxi...

Introduction: Gemtuzumab ozogamicin (GO), a CD33-antibody conjugated to DNA damaging cytotoxin-calicheamcin is a re-emerging and promising drug in AML treatment. Promising results from multiple clinical trials demonstrated GO improved outcomes in both adult and pediatric patients with most pronounced effect in favorable-risk cytogenetics. In light of these results GO was reapproved for treatment of AML by FDA in Sep 2017. Given the anticipated increase in GO use post approval, it is very timely to understand mechanisms contributing to differences in patient response. Calicheamicin releases intracellularly and causes DNA strand breaks which leads to apoptosis and cell death. The anti-leukemic effects of GO are thus entirely due to calicheamicin-induced DNA damage. Given that calicheamicin is a substrate of drug transporter ABCB1 (Pgp1), genetic polymorphisms in ABCB1 can impact the intra-cellular accumulation of calicheamicin and thus clinical outcome. Our group have recently shown that ABCB1 synonymous SNP rs1045642 C>T (also well known as 3435C>T) is associated with clinical outcome in children with AML trial, now we report the results of the in vitro evaluation of impact of ABCB1 SNP on calicheamicin mediated cell cytotoxicity. Methods: To understand differences in in vitro calicheamicin toxicity mediated by ABCB1 variation, HL-60 cells with low native ABCB1 expression were transfected with expression plasmid of ABCB1*1 (rs1045642-C and also WT for other two other SNPs in ABCB1) (WT Plasmid), and rs1045642-T. Cells were harvested 48 hours' post-transfection and treated with 40nM calicheamicin for 24 hours. Posttreatment cell were stained with permeant nuclear stain (NucRed® 647 Live Invitrogen) that emits bright far-red fluorescence upon binding to DNA in live cells. One-hour after incubation with the dye, calicheamicin toxicity was assessed by checking cell viability using flow cytometry (BDTM LSR II) and Nikon fluoresce microscope for additional visualization. Results: As shown in Figure 1a, our previous data show rs1045642 a synonymous coding change in ABCB1, in patients treated with GO presence of variant allele (CT/TT) is associated with significantly improved outcome as compared to patients with CC genotype (risk of relapse CC=45±10%, CT=30±7% TT=28±10%, CC vs. CT/TT p=0.007). Consistent with these results we observe significant decrease in cell viability with transfection with ABCB1-rs1045642/3435T as compared to the ABCB1-rs1045642/3435-C (P < 0.05) expression constructs. These results indicate that higher levels of calicheamicin toxicity in ABCB1-3435T transfected cells as opposed to cells transfected with the WT plasmid (Figure 1b and c) probably due to impact of T allele on ABCB1 levels. rs1045642-T allele has been shown to be associated with lower ABCB1 expression in several studies and with higher expression in one study. Hofmeyer et al has previously inked TT genotype of rs1045642 with lower expression and activity of ABCB1 which is consistent with our observation with respect to calicheamicin. Although more work is required to establish the clear relationship between ABCB1 genotypes and calicheamicin efflux, our results suggest that presence of ABCB1- low expressing rs1045642 TT genotype might be resulting in lower-efflux and thus higher intracellular abundance of calicheamicin in leukemic cells which in turn makes cells more sensitive to calicheamicin. Acknowledgments: Funding support from R21CA155524 and Children's Oncology group Disclosures No relevant conflicts of interest to declare.

Pharmaceutical industry now accept the worlds ocean which contains a vast array of organisms with unique biological properties, as a major frontier for medical investigation. Bioactive compounds with different modes of action, such as, antiproliferative, antioxidant, antimicrotubule, have been isolated from marine sources, specifically macro and micro algae, and cyanobacteria. The aim of this work was to investigate antimicrobial and cytotoxic activities of the extracts of marine macro algae Ulva flexuosa, Padina antillarum and Padina boergeseni from the northern coasts of the Persian Gulf, Qeshm Island, Iran, against three cell lines including MCF7, HeLa and Vero, as well as their inhibitory effects against a wide array (i.e. n = 11) of pathogenic bacteria and fungi. Antimicrobial activity of the marine macro algal extracts was assessed using a disc diffusion method; an MTT cytotoxicity assay was employed to test the effects of the extracts on each cancer cell line. The algal extracts showed considerable antimicrobial activity against the majority of the tested bacteria and fungi. Both ethyl acetate and methanol extracts at the highest concentration (100 µg/ml) caused cell death, with the IC50 values calculated for each cell type and each algal extracts. Results are exhibited a higher decrease in the viability of the cells treated at the highest concentration of marine macro algal ethyl acetate extracts compared to the methanol extracts (78.9 % death in Vero cells by ethyl acetate extracts from U. flexuosa). Despite, the ethyl acetate extracts with lower dose- response of cells, exhibited better cytotoxic activity than methanol extracts (IC50: 55.26 μg/ml in Vero cells by ethyl acetate extracts from U. flexuosa). Based on the findings, it is concluded that the marine macro algal extracts from the Persian Gulf possess antibacterial and cytotoxic potential, which could be considered for future applications in medicine and identifying novel drugs from the marine resources.

A modification of the iodometric technique using an overlay gel was employed for fast identification and isolation of β-lactamase types TEM, SHV and AmpC from non-denaturing gels. Osmotic shock preparations of the three β-lactamases were run on polyacrylamide gels without SDS and ampicillin containing overlay gels were flooded with the iodine solution before being placed on polyacrylamide gel strips. Distinct clear bands appeared in dark blue backgrounds indicating β-lactamase activity.

Background: Pseudomonas aeruginosa is one of the most common causes of nosocomial infections. Resistance of P. aeruginosa to β-lactam antibiotics may be the result of acquired resistance through mutation and over production of various antibiotic inactivating enzymes. This research aimed to determine the prevalence of extended-spectrum β-lactamases (ESBL) and metallo β-lactamase (MBL) production as well as the presence of their related genes among AmpC β-lactamase producing P. aeruginosa isolated from burns. Objectives: The current study aimed to determine the prevalence of class A ESBL and MBL production in relation to the presence of their related genes among AmpC β-lactamase producing P. aeruginosa isolated from burns. Materials and Methods: The antimicrobial susceptibility of 51 P. aeruginosa isolates from patients with burns was examined against 13 antibiotics by the disc diffusion method. Minimum inhibitory concentrations (MIC) for imipenem and ceftazidime were measured by the microdilution method. AmpC production was detected by AmpC disc and the modified three-dimensional extract tests. ESBL phenotype was confirmed by the double disc synergy test (DDST). Presence of β-lactamase genes was detected by specific primers and polymerase chain reaction (PCR). Results: All isolates were multidrug resistant. AmpC, ESBL and MBL production were observed in 35 (68.6%), 20 (39.2%) and 19 (37.3%) isolates, respectively. Overall, 43 isolates (84.3%) carried β-lactamase genes, out of which 31 (60.8%) harbored bla AmpC , 20 (39.2%) had bla TEM and 11 (21.6%) carried bla PER -1 genes. Among the AmpC producers, two isolates (6.5%) carried bla AmpC + bla ESBL , 13 (41.9%) had bla AmpC + bla MBL and six (19.4%) produced the three enzymes. Conclusions: A high prevalence of multiple β-lactamase production was observed among the AmpC producers (60%), of which the majority co-produced AmpC and MBL. The current study results showed correlation between β-lactamase production and the presence of antibiotic resistance genes in the isolates.