Signal Transduction Factors on the Modulation of Radiosusceptibility in K562 Cells / 대한방사선종양학회지

PURPOSE: The human chronic myelogenous leukemia cell line, K562, expresses the chimeric bcr-abl oncoprotein, whose deregulated protein tyrosine kinase activity antagonizes the induction of apoptosis via DNA damaging agents. Previous experiments have shown that nanomolar concentrations of herbimycin A (HMA) coupled with X-irradiation have a synergistic effect in inducing apoptosis in the Ph-positive K562 leukemia cell line, but genistein, a PTK inhibitor, is non selective for the radiation-induced apoptosis of p210bcr/abl protected K562 cells. In these experiments, the cytoplasmic signal transduction pathways, the induction of a number of transcription factors and the differential gene expression in this model were investigated. MATERIALS AND METHODS: K562 cells in the exponential growth phase were used in this study. The cells were irradiated with 0.5-12 Gy, using a 6 MeV Linac (Clinac 1800, Varian, USA). Immediately after irradiation, the cells were treated with 0.25 microM of HMA and 25 microM of genistein, and the expressions and the activities of abl kinase, MAPK family, NF-kB, c-fos, c-myc, and thymidine kinase1 (TK1) were examined. The differential gene expressions induced by PTK inhibitors were also investigated. RESULTS: The modulating effects of herbimycin A and genistein on the radiosensitivity of K562 cells were not related to the bcr-abl kinase activity. The signaling responses through the MAPK family of proteins, were not involved either. In association with the radiation-induced apoptosis, which is accelerated by HMA, the expression of c-myc was increased. The combined treatment of genistein, with irradiation, enhanced NF-kB activity and the TK1 expression and activity. CONCLUSION: The effects of HMA and genistein on the radiosensitivity of the K562 cells were not related to the bcr-abl kinase activity. In this study, another signaling pathway, besides the MAPK family responses to radiation to K562 cells, was found. Further evaluation using this model will provide valuable information for the optional radiosensitization or radioprotection.

Smad6 Gene and Suppression of Radiation-Induced Apoptosis by Genistein in K562 cells / 대한방사선종양학회지

PURPOSE: The genes involved on the suppression of radiation-induced apoptosis by genistein in K562 leukemia cell line was investigated. MATERIALS AND METHODS: K562 cells in exponential growth phase were irradiated with a linear accelerator at room temperature. Forx-ray irradiation and drug treatment, cultures were prepared at 2x105 cells/mL. The cells were irradiated with 10 Gy (Clinac 1800C, Varian, USA). Stock solutions of herbimycin A (HMA, Calbiochem, UK) and genistein (Calbiochem, UK) were prepared in dimethylsulfoxide (DMSO, Sigma, UK). After incubation at 37degreesC for 24 h, PCR-select cDNA subtractive hybridization, dot hybridization, DNA sequencing and Northern hybridization were examined. RESULTS: Smad6 gene was identified from the differentially expressed genes in K562 cells incubated with genistein which had been selected by PCR-select cDNA subtractive hybridization. The mRNA expression of Smad6 in K562 cells incubated with genistein was also higher than control group by Northern hybridization analysis. CONCLUSION: We have shown that Smad6 involved on the suppression of radiation-induced apoptosis by genistein in K562 leukemia cell line. It is plausible that the relationship between Smad6 and the suppression of radiation-induced apoptosis is essential for treatment development based on molecular targeting designed to modify radiation-induced apoptosis.

Electrohydaulic Lithotripsy (EHL) of Retained Common Hile Duct Stone with Choledochoscopy / 대한소화기내시경학회지

Electrohydraulic lithotripsy (EHL) is a method used to breakup the stone by electric discharge in the presence of liquid medium. Recently we experienced a case of successful common bile duct stone removal after EHL during choledochoscopy via T-tube tract, which was the first case of EHL in biliary tract stone in Korea. A 65-year-old female patient was admitted to our hospital because of generalized pruritus after cholcystectomy with T-tube insertion. Obtained cholangiogram showed retained CBD stone which was implssible to remove by Dormian basket and tto dissolute by monooctanoin. After only one session of EHL, we can disintergrat CBD stone into several small pieces and removal of stone was easily done by Basket. After Small cut endoscopic sphincterotomy (EST) remained distal impacted stone was freely passed and control choledochoscopy and cholangiogram showed no remained stone. We think that EHL may be play a potential role in removal of biliary tract stones as in urinary tract stones.