The role of hypoxia on the acquisition of epithelial-mesenchymal transition and cancer stemness: a possible link to epigenetic regulation

A hypoxic microenvironment leads to cancer progression and increases the metastatic potential of cancer cells within tumors via epithelial-mesenchymal transition (EMT) and cancer stemness acquisition. The hypoxic response pathway can occur under oxygen tensions of < 40 mmHg through hypoxia-inducible factors (HIFs), which are considered key mediators in the adaptation to hypoxia. Previous studies have shown that cellular responses to hypoxia are required for EMT and cancer stemness maintenance through HIF-1α and HIF-2α. The principal transcription factors of EMT include Twist, Snail, Slug, Sip1 (Smad interacting protein 1), and ZEB1 (zinc finger E-box-binding homeobox 1). HIFs bind to hypoxia response elements within the promoter region of these genes and also target cancer stem cell-associated genes and mediate transcriptional responses to hypoxia during stem cell differentiation. Acquisition of stemness characteristics in epithelial cells can be induced by activation of the EMT process. The mechanism of these phenotypic changes includes epigenetic alterations, such as DNA methylation, histone modification, chromatin remodeling, and microRNAs. Increased expression of EMT and pluripotent genes also play a role through demethylation of their promoters. In this review, we summarize the role of hypoxia on the acquisition of EMT and cancer stemness and the possible association with epigenetic regulation, as well as their therapeutic applications.

Managing Outpatients with Dyslipidemia in a University Hospital

BACKGROUND: We evaluated physician's management of hypercholesterolemia on the basis of the third Adult Treatment Panel (ATP III) report of the National Cholesterol Education Program. METHODS: The subjects were, 85 adult patients. The inclusion criteria were follows: outpatients with an initial total cholesterol level of > or =200 mg/dL or HDL-cholesterol or =160 mg/dL for patients with risk factor or =130 mg/dL for patients with risk factors > or =2; > or =100 mg/dL for patients with CHD or diabetes). In 59.5% of patients with undesirable LDL reported that they did not provide education about TLC and in 40.0% of patients with desirable LDL were provided prescription of LDL- lowering drugs from physicians. Physicians were more likely to prescribe if the patients had more risk factors (P=0.001) and educated patients when they prescribed them (P=0.049). However, physicians did not educate on TLC and did not recheck lipid profile prior to first prescription. CONCLUSION: The physicians did not follow the ATP III guideline for management of hypercholesterolemia. Barriers to comply with these guidelines and ways to eliminate barriers should be found.

Characterization and Prevalence of Escherichia coli and Klebsiella pneumoniae Isolates Producing an Extended-Spectrum beta-Lactamase from Korean Hospitals / 대한진단검사의학회지

BACKGROUND: The aim of this study was to survey the nationwide susceptibilities of E. coli and K. pneumoniae against third generation cephalosporins and aztreonam in order to determine the prevalence of extended-spectrum beta-lactamase (ESBL)-producers and to characterize genotypes of ESBLs. METHODS: A total of 6, 567 E. coli and 2, 652 K. pneumoniae non-duplicate strains were isolated from 13 hospitals in April to June 2002. Antimicrobial susceptibilities were tested by the disk diffusion method. Twenty isolates of E. coli and 20 K. pneumoniae were collected from each hospital. ESBL production was determined by a double-disk synergy test. The ceftazidime-resistance of the ESBL-producers was transferred to azide-resistant E. coli J53 by conjugation. MICs of beta-lactam antibiotics to transconjugants were determined by the agar dilution method. Searches for blaTEM , blaSHV , blaCTX-M and blaCMY genes in transconjugants were performed by PCR amplification. RESULTS: Eighty-nine percents of E. coli and 71% of K. pneumoniae isolates were susceptible to ceftazidime. Nine percents of E. coli (23/249) and 30% (78/260) of K. pneumoniae isolates showed positive results in the double-disk synergy test. Ceftazidime-resistance of 13 (57%) E. coli and 42 (53%) K. pneumoniae isolates were transferred to E. coli J53 by conjugation. Among 55 transconjugants, 46 strains were resistant to ceftazidime, while only 16 strains were resistant to cefotaxime. Twelve transconjugants were also resistant to cefoxitin and cefotetan. Banding patterns of PCR amplification showed that the blaTEM , blaSHV , blaCTX-M and blaCMY genes were harboured by 44, 39, 4 and 5 transconjugants, respectively. CONCLUSIONS: E. coli and K. pneumoniae isolates producing TEM-, SHV-type, or CTX-M-type ESBLs are wide spread in Korean hospitals. The spread of ESBL genes could compromise the future usefulness of 3rd generation cephalosporins and aztreonam for the treatment of E. coli and K. pneumoniae infections.

Characterization of Extended-Spectrum-beta-Lactamase Genes from Clinical Isolates of Enterobacter species / 대한임상미생물학회지

BACKGROUND: Among Enterobacter spp. isolates from clinical specimens in Korea, the incidence of resistance to expanded-spectrum cephalosporins is becoming an ever-increasing problem. This study was designed to determine the prevalence of expanded-spectrum cephalosporins-resistant Enterobacter spp. isolates from patients in a tertiary care hospital in Busan, Korea, and to characterize the mechanism of resistance. MATERIALS AND METHODS: Nonduplicated clinical isolates of Enterobacter spp. were collected during the period of 1999-2000 in Kosin Medical Center, Busan, Korea. Antimicrobial susceptibilities were tested by disk diffusion method. Cefotaxime-resistant or intermediate isolates were examined for extended-spectrum beta-lactamase (ESBL)-production by double disk synergy (DDS) test. Minimal inhibitory concentrations were determined by agar dilution method. For detection of blaTEM and blaSHV genes, polymerase chain reactions (PCRs) were performed, and the DNA sequences of blaTEM and blaSHV genes were determined by using dideoxy-chain termination method. RESULTS: From 1999 to 2000, a total of 306 Enterobacter spp. strains were isolated from patients in Kosin Medical Center. Forty one percents of Enterobacter spp. isolates were susceptible to cefotaxime. Among 90 isolates resistant or intermediate to cefotaxime, 26 isolates (29%) showed positive results in double disk synergy test. Among DDS-positive- isolates, 22 isolates contained both of blaTEM and blaSHV genes, while one isolate only contained blaTEM gene and two isolates only contained blaSHV gene. Among 64 DDS-negative isolates, 47 isolates contained blaTEM genes, and 12 isolates also contained blaSHV genes. Nucleotide sequence analysis of PCR products from 10 DDS-positive and 6 DDS-negative isolates, which contained both of blaTEM and blaSHV genes, revealed that blaTEM-1b and blaSHV-12 genes were the dominant types of beta-lactamase gene. CONCLUSION: Expanded-spectrum cephalosporins-resistant Enterobacter spp. were wide spread in Kosin Medical Center, Busan, Korea. Some of the resistant isolates acquired resistance by production of ESBLs, and blaSHV-12 gene was the most frequent ESBL gene in cefotaxime-resistant Enterobacter spp.

Prevalence and Mechanism of Third-Generation Cephalosporins-Resistant Escherichia coli and Klebsiella pneumoniae Strains Isolated from Clinical Specimen / 대한임상미생물학회지

BACKGROUND: Among Gram-negative pathogens in Korea, the incidence of resistance to thirdgeneration cephalosporins is becoming an ever-increasing problem. This study was designed to determine the prevalence of third-generation cephalosporins-resistant Escherichia coli and Klebsiella pneumoniae isolates from patients in a tertiary care hospital in Busan, Korea, and to characterize the mechanism of resistance. METHODS: A total of 710 E. coli and 237 K. pneumoniae non-duplicate isolates were collected from patients in Kosin Medical Center in 1999. Antimicrobial susceptibilities were tested by the disk diffusion method. Extended-spectrum beta-lactamase (ESBL) production was determined by the double disk synergy test. MICs were determined by the agar dilution method. Searches for blaTEM, blaSHV, and blaCMY genes in cefotaxime-resistant or intermediate isolates were performed by PCR amplification. PCR products were used to determine the sequence of resistance genes by the dideoxy-chain termination method. RESULTS: Seven percent of E. coli and 25% of K. pneumoniae isolates were resistant to cefotaxime. Among the isolates with decreased susceptibility to cefotaxime, 69% (18/26) of E. coli and 80% (20/25) of K. pneumoniae isolates showed positive results in double disk synergy test. Banding patterns of PCR amplification showed that the blaTEM, blaSHV, and blaCMY genes were harboured by 71% (20/28), 86% (24/28) and 14% (4/28) of isolates with decreased susceptibility to cefotaxime,respectively. Seventy-one percent (20/28) of the isolates contained more than two types of beta- lactamase genes. Nucleotide sequence analysis of PCR products revealed that blaSHV-12 and blaTEM-1b were the dominant types of beta-lactamase gene. In addition, we also identified blaTEM-52, blaSHV-5, and a new ESBL gene named blaTEM-17b. CONCLUSIONS: Third-generation cephalosporins-resistant E. coli and K. pneumoniae are wide spread in Kosin Medical Center, Busan, Korea. Most of the isolates with decreased susceptibility to cefotaxime had blaTEM and/or blaSHV, and some isolates harboured blaCMY genes that may confer resistance against cephamycins. The spread of these beta-lactamase genes could compromise the future usefulness of third-generation cephalosporins for the treatment of infections caused by E. coli and K. pneumoniae.

Genotypes of Metallo-beta-Lactamases Produced by Imipenem-Resistant Acinetobacter spp. Isolates from Clinical Specimens / 감염

BACKGROUND: Carbapenem-resistant Acinetobacter spp. are being isolated with increasing frequency from clinical sources. This study was designed to determine the resistance mechanism to carbapenems of Acinetobacter spp. isolates from patients of a tertiary care hospital in Busan, Korea. METHODS: Nonduplicated clinical isolates of Acinetobacter spp. resistant to carbapenems were collected during the period of 2000-2001 in Kosin Medical Center, Busan, Korea. Antimicrobial susceptibilities were tested by disk diffusion method. Carbapenem-resistant Acinetobacter spp. isolates were examined for metallo-beta-lactamase-production by modified Hodge and EDTA-disk synergy tests. For the detection of blaIMP-1 and blaVIM-2 genes, polymerase chain reactions (PCR) were performed, and the DNA sequences of amplified products were determined by using dideoxy- chain termination method. RESULTS: Among 21 clinical isolates of Acinetobacter spp. intermediate or resistant to carbapenems, 17 isolates showed positive reactions in modified Hodge and EDTA-disk synergy tests. Nine isolates showed positive reaction in PCR for the detection of blaIMP-1 genes, and 8 isolates showed positive reaction in PCR for the detection of blaVIM-2 genes. Sequencing of amplified products showed that they were blaIMP-1 or blaVIM-2 genes. CONCLUSION: Acinetobacter spp. isolates with carbapenem-resistance are not uncommon in Kosin Medical Center, and most of the carbapenem-resistant isolates acquired resistance by production of IMP-1 or VIM-2 metallo-beta-lactamases. The spread of metallo-beta-lactamase genes could compromise the future usefulness of carbapenem for the treatment of gram-negative bacilli infections.