Woo-Yoon Park

Runt-Related Transcription Factor RUNX3 Is a Target of MDM2-Mediated Ubiquitination

The p14(ARF)-MDM2-p53 pathway constitutes an effective mechanism for protecting cells from oncogenic stimuli such as activated Ras and Myc. Importantly, Ras activation induces p14(ARF) and often occurs earlier than p53 inactivation during cancer development. Here, we show that RUNX3, a tumor suppressor in various tumors including stomach, bladder, colon, and lung, is stabilized by Ras activation through the p14(ARF)-MDM2 signaling pathway. RUNX3 directly binds MDM2 through its Runt-related DNA-binding domain. MDM2 blocks RUNX3 transcriptional activity by interacting with RUNX3 through an acidic domain adjacent to the p53-binding domain of MDM2 and ubiquitinates RUNX3 on key lysine residues to mediate nuclear export and proteasomal degradation. Our data indicate that the lineage-specific tumor suppressor RUNX3 and the ubiquitous p53 protein are both principal responders of the p14(ARF)-MDM2 cell surveillance pathway that prevents pathologic consequences of abnormal oncogene activation.

Effect of pentoxifylline on radiation response of non-small cell lung cancer: a phase III randomized multicenter trial.

PURPOSES The objectives of this prospective clinical trial were to determine whether pentoxifylline improves the radiation response and survival in patients with non-small cell lung cancer. MATERIALS AND METHODS From July 1993 through October 1994, 64 patients with histologically confirmed Stage I, II and III non-small cell lung cancer were randomly divided into pentoxifylline (Pento)+Radiotherapy (RT) group and RT alone group. Out of the 64 patients, only 47 patients who had measurable tumors on chest X-ray views were analyzed and divided into Pento+RT group (n=27) and RT alone group (n=20). Total tumor dose of 65-70 Gy was delivered as conventional fractionated radiation schedules. Pento was given to the patients 3 x 400 mg/day with a daily dose of 1200 mg during RT. RESULTS Complete response (CR), partial response (PR), and stable in Pento+RT group were three (11%), 13 (48%), and 11 (41%), respectively, as compared with corresponding values of three (15%), 13 (65%), and four (20%) in the RT alone group. The median time to relapse in the Pento+RT group was 11 months which was 2 months longer than for the RT alone group (P>0.05). All the patients in both groups showed lower than or equal to grade 2 dysphagia, odynophagia, pulmonary fibrosis, and pneumonitis. The median survival was 18 months in the Pento+RT group and 7 months in the RT alone group. The 1-year survival rate was 60% in the Pento+RT group and 35% in the RT alone group, the 2-year survival rate was 18% in the Pento+RT group and 12% in the RT alone group. But these differences were not statistically significant (P>0.05). CONCLUSION We concluded that Pento is a modestly effective radiation response modifier and provide benefit in the treatment of non-small cell lung cancer.

Melatonin exerts differential actions on X-ray radiation-induced apoptosis in normal mice splenocytes and Jurkat leukemia cells

Abstract:  The ability of melatonin as a potent antioxidant was used as a rationale for testing its antiapoptotic ability in normal cells. Recently, melatonin was shown to possess proapoptotic action by increasing reactive oxygen species in certain cancer cells. The modification of radiation‐induced apoptosis by melatonin and the expression of apoptosis‐associated upstream regulators were studied in normal mice splenocytes and Jurkat T leukemia cells. C57BL/6 mice were exposed to a single whole body X‐ray radiation dose of 2 Gy with or without 250 mg/kg melatonin pretreatment. The Jurkat cells were divided into four groups of control, 1 mm melatonin alone, 4 Gy irradiation‐only and melatonin pretreatment before irradiation. The highest level of apoptosis in the normal splenic white pulp was detected by TUNEL assay at 8 hr after irradiation. At this time, the apoptotic index of irradiation‐only and melatonin pretreatment groups were 35.6% and 20.7%, respectively. This reduced apoptosis by melatonin was associated with the increase of Bcl‐2 expression and a reduction of Bax/Bcl‐2 ratio through a relative decrease of p53 mRNA and protein. In the Jurkat cells treated with a combination of melatonin and radiation, both Annexin V‐FITC(+)/PI(−) and Annexin V‐FITC(+) cells were increased at 48 hr after irradiation when compared with irradiation‐only or melatonin alone. The expressions of p53 between groups were well correlated with the results of Annexin V binding. The irradiation or melatonin did not influence the JNK1 expression in Jurkat cells. The present results suggest that melatonin enhances radiation‐induced apoptosis in Jurkat leukemia cells, while reducing radiation‐induced apoptosis in normal mice splenocytes. These differential effects on radiation‐induced apoptosis by melatonin might involve the regulation of p53 expression.

Clinical predictive factors of pathologic tumor response after preoperative chemoradiotherapy in rectal cancer

Purpose The aim of this study was to identify clinical predictive factors for tumor response after preoperative chemoradiotherapy (CRT) in rectal cancer. Materials and Methods The study involved 51 patients who underwent preoperative CRT followed by surgery between January 2005 and February 2012. Radiotherapy was delivered to the whole pelvis at a dose of 45 Gy in 25 fractions, followed by a boost of 5.4 Gy in 3 fractions to the primary tumor with 5 fractions per week. Three different chemotherapy regimens were used (5-fluorouracil and leucovorin, capecitabine, or tegafur/uracil). Tumor responses to preoperative CRT were assessed in terms of tumor downstaging and pathologic complete response (ypCR). Statistical analyses were performed to identify clinical factors associated with pathologic tumor response. Results Tumor downstaging was observed in 28 patients (54.9%), whereas ypCR was observed in 6 patients (11.8%). Multivariate analysis found that predictors of downstaging was pretreatment relative lymphocyte count (p = 0.023) and that none of clinical factors was significantly associated with ypCR. Conclusion Pretreatment relative lymphocyte count (%) has a significant impact on the pathologic tumor response (tumor downstaging) after preoperative CRT for locally advanced rectal cancer. Enhancement of lymphocyte-mediated immune reactions may improve the effect of preoperative CRT for rectal cancer.

Multiplex PCR Detection of Waterborne Intestinal Protozoa: Microsporidia, Cyclospora, and Cryptosporidium

Recently, emerging waterborne protozoa, such as microsporidia, Cyclospora, and Cryptosporidium, have become a challenge to human health worldwide. Rapid, simple, and economical detection methods for these major waterborne protozoa in environmental and clinical samples are necessary to control infection and improve public health. In the present study, we developed a multiplex PCR test that is able to detect all these 3 major waterborne protozoa at the same time. Detection limits of the multiplex PCR method ranged from 101 to 102 oocysts or spores. The primers for microsporidia or Cryptosporidium used in this study can detect both Enterocytozoon bieneusi and Encephalitozoon intestinalis, or both Cryptosporidium hominis and Cryptosporidium parvum, respectively. Restriction enzyme digestion of PCR products with BsaBI or BsiEI makes it possible to distinguish the 2 species of microsporidia or Cryptosporidium, respectively. This simple, rapid, and cost-effective multiplex PCR method will be useful for detecting outbreaks or sporadic cases of waterborne protozoa infections.

Detection of Cryptosporidium parvum in Environmental Soil and Vegetables

Cryptosporidium parvum is a zoonotic protozoan parasite that causes cryptosporidial enteritis. Numerous outbreaks of cryptosporidiosis have been reported worldwide. Cryptosporidium is transmitted to hosts via consumption of contaminated water and food but also by direct contact with contaminated soil or infected hosts. The present study investigated farm soil collected from 34 locations along the western Korean peninsula and 24 vegetables purchased from local grocery markets in Seoul. The soil and vegetable samples were examined by real-time polymerase chain reaction (qPCR) to estimate the risk of infection. Eleven of 34 locations (32.4%) and 3 of 24 vegetable samples (12.5%) were contaminated with Cryptosporidium parvum, as confirmed by TaqI enzyme digestion of qPCR products and DNA sequencing. It is suggested that Cryptosporidium infection can be mediated via farm soil and vegetables. Therefore, it is necessary to reduce contamination of this organism in view of public health. Graphical Abstract

EGF-induced expression of Fused Toes Homolog (FTS) facilitates epithelial-mesenchymal transition and promotes cell migration in ME180 cervical cancer cells

The role of Fused Toes Homolog (FTS) in epidermal growth factor (EGF) induced epithelial-mesenchymal transition (EMT) in cervical cancer cells was studied. EGF treatment induced the change of EMT markers and increased cell migration. EGF treatment also increased phosphorylated EGFR and ERK and nuclear level of ATF-2. The binding of ATF-2 to the promoter region of FTS was evidenced after EGF treatment. Pretreatment with PD98059 and gefitinib prevented EGF-induced FTS expression. FTS silencing reduced EMT and cell migration by EGF treatment. These results demonstrate a novel function for FTS in EGF-mediated EMT process.

Fenofibrate decreases radiation sensitivity via peroxisome proliferator-activated receptor α-mediated superoxide dismutase induction in HeLa cells

Purpose The fibrates are ligands for peroxisome proliferator-activated receptor (PPAR) α and used clinically as hypolipidemic drugs. The fibrates are known to cause peroxisome proliferation, enhance superoxide dismutase (SOD) expression and catalase activity. The antioxidant actions of the fibrates may modify radiation sensitivity. Here, we investigated the change of the radiation sensitivity in two cervix cancer cell lines in combination with fenofibrate (FF). Materials and Methods Activity and protein expression of SOD were measured according to the concentration of FF. The mRNA expressions were measured by using real time reverse-transcription polymerase chain reaction. Combined cytotoxic effect of FF and radiation was measured by using clonogenic assay. Results In HeLa cells total SOD activity was increased with increasing FF doses up to 30 µM. In the other hand, the catalase activity was increased a little. As with activity the protein expression of SOD1 and SOD2 was increased with increasing doses of FF. The mRNAs of SOD1, SOD2, PPARα and PPARγ were increased with increasing doses of FF. The reactive oxygen species (ROS) produced by radiation was decreased by preincubation with FF. The surviving fractions (SF) by combining FF and radiation was higher than those of radiation alone. In Me180 cells SOD and catalase activity were not increased with FF. Also, the mRNAs of SOD1, SOD2, and PPARα were not increased with FF. However, the mRNA of PPARγ was increased with FF. Conclusion FF can reduce radiation sensitivity by ROS scavenging via SOD induction in HeLa. SOD induction by FF is related with PPARα.

Helicase-like transcription factor confers radiation resistance in cervical cancer through enhancing the DNA damage repair capacity

Helicase-like transcription factor (HLTF) is a member of the SWI/SNF (mating type switching/sucrose non-fermenting) family of ATPases/helicases and also has a RING-finger motif characteristic of ubiquitin ligase proteins. These features have led to suggestions that HLTF functions like yeast Rad5, which promotes replication through DNA lesions via a post-replication repair pathway. However, the function of HLTF in higher eukaryotes is still unknown. Herein, we found the overexpression of HLTF in radiation recurrent human uterine cervical carcinoma tissues when compared to disease free survived patients tissues. In this study, we used RNA interference techniques to investigate the potential function of HLTF in cervical cancer cell line HeLa and found that the cell proliferation was reduced by knockdown (KD) of HLTF. A host-cell reactivation assay showed that the capacity for repair to DNA damage induced by X-ray irradiation was reduced in HLTF KD cells. X-rays also increased apoptosis in HLTF KD cells. These results suggest that HLTF is involved in DNA repair and apoptosis in cancer cells, which might represent a target for gene therapies of human cancer.

Characterization of the thioredoxin peroxidase from Cryptosporidium parvum.

Cryptosporidium parvum can survive exposure to harsh environmental conditions, various disinfectants, and high doses of γ-radiation. Recently, it was found that the expression of thioredoxin peroxidase (CpTPx) in C. parvum increased after a high dose of γ-irradiation to the parasite. CpTPx is a two-cysteine peroxiredoxin that contains cysteines at positions 49 and 170. Recombinant CpTPx fused to an N-terminal hexahistidine sequence, (His)(6)-CpTPx, exhibited substantial thiol-dependent peroxidase activity that protected plasmid DNA from damage by metal-catalyzed oxidation in vitro. (His)(6)-CpTPx was used to screen sera from C. parvum-infected mice and humans for antibodies against CpTPx. In Western blots, 10% of the mouse sera and 20% of the human sera reacted with (His)(6)-CpTPx, suggesting that after infection by C. parvum CpTPx can induce a host-immune reaction but is not a major antigen. Immunolocalization studies revealed that CpTPx is expressed mainly in the cytoplasm of C. parvum at various developmental stages.