Jinko Ishikawa

Promoter Hypermethylation in Cancer Silences LDHB, Eliminating Lactate Dehydrogenase Isoenzymes 1-4

Lactate dehydrogenase (LD; EC 1.1.1.27) isoenzymes are formed by the random combination of two different subunits encoded by two structurally distinct genes, LDHA and LDHB (1). Expression of mammalian LDHA and LDHB is regulated during development and is tissue specific (2)(3); therefore, alterations in the serum LD isoenzyme pattern serve as indicators of pathologic involvement and cancer development (3). In cancer patients, LD isoenzymes originate primarily from tumor tissues and partly from healthy tissues damaged by tumor expansion and invasion. Different phenotypes may originate from expression regulation by other regulatory genes and by the alteration of LDHA or LDHB caused by mutation; chromosomal deletion; duplication, or increase of copy number; and promoter methylation. The increase in LD1 correlates with the total copy number of the short arm of chromosome 12 in tumor cells (4). Recently, we found a high proportion of LD1 in a patient with retinoblastoma. The unique LD isoenzyme pattern was attributable to transcriptional silencing by promoter hypermethylation of LDHA (5). In mammals, DNA methylation usually occurs at CpG dinucleotides, which are cytosines located 5′ of guanines. Methylation is known to play a role in regulating gene expression during cell development, X chromosome inactivation, genomic imprinting, and carcinogenesis (6)(7). In neoplastic cells, some CpG islands in the promoter region that are usually unmethylated become aberrantly methylated, and this leads to transcriptional silencing. Therefore, an epigenetic event is thought to be one mechanism for the inactivation of tumor suppressor genes (8). Human LDHB has a CpG-rich region in its promoter that is similar to that of human LDHA and LDHC (9). We found that five cancer cell lines had only LDHA mRNA (10). Most gastrointestinal cancer patients had electrophoretically slow-moving isoenzymes and the LD-A subunit in their sera (3). We predicted that this …

Genetic basis of the silent phenotype of serum butyrylcholinesterase in three compound heterozygotes

Three Japanese patients showed very low butyrylcholinesterase activity in their sera and appeared to be homozygous for silent genes for butyrylcholinesterase. From DNA analysis, all three patients were compound heterozygotes: GGA(Gly) to CGA(Arg) at codon 365 (G365R) and TTC(Phe) to TCC(Ser) at codon 418 (F418S) in patient 1, G365R and CGT(Arg) to TGT(Cys) at codon 515 (R515C) in patient 2 and ACT(Thr) to CCT(Pro) at codon 250 (T250P) and AGA(Arg) to TGA(Stop) at codon 465 (R465X) in patient 3. The K-variant, GCA(Ala) to ACA(Thr) at codon 539, was also found in patients 1 and 2. Simple identification methods for all the mutations were developed and applied to family analysis and control individuals. The mutant alleles (with silent gene and K-variant) were segregated as predicted by theory in pedigrees of patients 1 and 2. Four of the mutations, F418S, R515C, T250P and R465X, were initially discovered in Japan and genetic heterogeneity among the human population for the butyrylcholinesterase gene was suggested.

Effects of Mupirocin at Subinhibitory Concentrations on Biofilm Formation in Pseudomonas aeruginosa

Background: Subinhibitory concentrations of mupirocin can suppress flagellar formation in Pseudomonas aeruginosa. In this study, we evaluated the effect of mupirocin on biofilm formation in P. aeruginosa. Methods:P. aeruginosa PAO-1 (MIC, >1,024 µg/ml for mupirocin) was used. Viable bacteria adhering or forming biofilm on a Cell Desk were counted and observed by scanning electron microscopy. Results: With or without continuous exposure to 256 µg/ml of mupirocin, counts of adherent and/or biofilm-forming bacteria showed no difference until day 10. Whereas biofilm formation with glycocalyx was observed on day 6–10 without mupirocin, mupirocin reduced biofilm formation and glycocalyx production for 10 days. Conclusions: Subinhibitory concentrations of mupirocin can reduce biofilm formation in vitro in P. aeruginosa.