Tae-Bum Lee

Lipid raft-dependent death receptor 5 (DR5) expression and activation are critical for ursodeoxycholic acid-induced apoptosis in gastric cancer cells

Ursodeoxycholic acid (UDCA) is known as a suppressor of cholestatic liver diseases and colorectal cancer development. Here, we demonstrate that UDCA induces apoptosis without necrotic features in SNU601, SNU638, SNU1 and SNU216 human gastric cancer cells, implying its possible use as an effective chemotherapeutic agent in treatment of gastric cancer. UDCA-induced apoptosis was dominantly mediated by an extrinsic pathway dependent on caspase-8, -6 and -3. UDCA increased expression of death receptor 5 [(DR5), also known as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor 2], and this DR appeared to be responsible for UDCA-induced apoptosis, as evidenced by DR5 knockdown. UDCA triggered formation of lipid rafts that played crucial roles in UDCA-induced apoptotic actions. Lipid rafts were required not only for provision of a proper site for DR5 action but also for mediation of DR5 expression. In addition, reactive oxygen species (ROS) and protein kinase C (PKC) δ appeared to be implicated in UDCA-induced raft-dependent DR5 expression. Our results indicate that UDCA-induced apoptosis is mediated by DR5 expression, which is regulated by the raft formation/ROS production/PKCδ activation pathway and DR5 localization into lipid rafts in gastric cancer cells. Tumor-suppressive activity of UDCA was confirmed in an in vivo system: UDCA (120 mg/kg/day) significantly decreased tumor growth in gastric cancer xenograft mice. Taken together, our results demonstrate that UDCA can be used as a potent chemotherapeutic agent for treatment of gastric cancer.

Fas (Apo-1/CD95) and Fas ligand interaction between gastric cancer cells and immune cells

Background and aims: It has been proposed that the expression of Fas ligand (Fas L) in tumors may play an important role in immune escape. This study was undertaken to test a ‘counterattack’ theory as a mechanism of immune escape in gastric carcinoma.

Histone H4 deacetylation down-regulates catalase gene expression in doxorubicin-resistant AML subline.

We explored if epigenetic mechanisms could be involved in the down-regulated expression of catalase gene (CAT) in the doxorubicin-resistant acute myelogenous leukemia (AML)-2/DX100 cells. Down-regulated CAT expression in AML-2/DX100 cells was completely recovered after treatment of hydrogen peroxide (H2O2) and histone deacetylase inhibitor, trichostatin A (TSA) but was increased slightly by the treatment of DNA methylation inhibitor, 5-aza-2′-deoxycytidine (5-AdC). Bisulfite-sequencing PCR revealed that a CpG island of CAT was not methylated in AML-2/DX100 cells. Chromatin immunoprecipitation assay confirmed that acetylation of histone H4 in AML-2/DX100 cells significantly decreased as compared with that in AML-2/WT cells, which was significantly increased by TSA more than 5-AdC. Meanwhile, overexpression of other up-regulated peroxidase genes appears to make compensation for decreased H2O2-scavenging activity for the down-regulated CAT expression in AML-2/DX100 cells. These results suggest that histone H4 deacetylation is responsible for the down-regulated CAT expression in AML-2/DX100 cells, which are well adapted to oxidative stress.

Melanoma antigen gene family A as a molecular marker of gastric and colorectal cancers

The present study aimed to evaluate the role of melanoma antigen family A (MAGEA) in gastric and colorectal cancer cell lines and clinical tissue samples. we used 10 gastric and 9 colorectal cancer cell lines, 20 early-stage and 21 advanced-stage gastric cancer tissues, 20 colon adenomas and 19 colorectal cancer tissues. Real-time RT-PCR assay was used for the determination of MAGEA mRNA levels. Western blot analysis and immunohistochemistry were used for the determination of MAGEA protein levels in cell lines and tissues, respectively. Gastric and colorectal cancer cell lines showed variable mRNA expression levels of MAGEA. The MAGEA protein was detected in 30% of gastric cancer cell lines and in 22.2% of colorectal cancer cell lines. There was a high correlation between mRNA and protein expression. Regarding the clinical samples, MAGEA expression was noted in 25, 28.6 and 31.6%, respectively in early-stage, advanced-stage gastric cancer tissues and colon adenocarcinoma, but was negative in the adjacent normal tissues of the stomach and colon as well as colon adenoma. These results indicate that MAGEA is involved in the carcinogenesis of gastric and colorectal cancer and, therefore, can be used as a diagnostic marker to predict these cancers.

Detection of drug transporter expression using a 25-multiplex RT-PCR assay

Membrane transporters play important roles in mediating chemoresistance and chemosensitivity of tumor cells. Five sets of 5 genes were designed to simultaneously detect drug transporter expression in a single reaction tube using multiplex RT-PCR for 25 genes, including 17 ABC transporters, one non-ABC transporter, 4 SLC transporters, 2 copper transporters and one housekeeping gene. We optimized the multiplex RT-PCR conditions using chemosensitive cancer cells and then validated the system using chemoresistant cancer cells. This reliable multiplex RT-PCR assay can be utilized not only to investigate anticancer drug-resistance mechanisms but also to estimate the efficacy of anticancer chemotherapy in the clinic.

PS 14-23 EFFECTS OF RUBUS OCCIDENTALIS EXTRACT ON BLOOD PRESSURE IN SUBJECTS WITH PREHYPERTENSION: RANDOMIZED, DOUBLE-BLINDED, PLACEBO CONTROLLED CLINICAL TRIAL

Objective: Black raspberry (Rubus occidentalis) is known for improving vascular function. However, there has been no study evaluating the effects of black raspberry on 24 hour systolic and diastolic blood pressure in prehypertensive patients. Design and Method: Patients with prehypertension (n = 45) were prospectively randomized into the moderate-dose black raspberry group (n = 15, 1500mg/day), high-dose black raspberry group (n = 15, 2500mg/day) or placebo group (n = 15) during the 8-week follow-up. Raspberries were consumed in the form of dried powder extract which was fashioned in to capsules. The capsules contained 187.5 mg and 312.5 mg of raspberry powder which were equivalent to 1500 mg and 2500 mg raspberries. Ambulatory 24-hour blood pressure, central blood pressure, pulse wave velocity, abdominal visceral fat, serum renin, angiotensin converting enzyme and inflammatory cytokines such as IL-6, TNF-&agr;, C-reactive protein, sICAM-1, sVCAM-1, PAI-1 were measured at baseline and at 8-week follow-up. Results: High-dose black raspberry significantly reduced 24-hour systolic blood pressure (3.3 ± 10.0 mmHg vs. −6.7 ± 11.8 mmHg, p < 0.05) and night-time systolic blood pressure (5.4 ± 10.6 mmHg vs. −4.5 ± 11.3 mmHg, p < 0.05), as compared to the controls during the 8-week follow-up. Black raspberry powder did not produce any significant changes in most of the parameters other than blood pressure. Conclusions: The use of black raspberry significantly lowered 24 hour blood pressure in prehypertensive patients during the 8-week follow-up. Black raspberry used as a dietary supplement could be beneficial in reducing systolic blood pressure in prehypertensive patients.