Jae-Gahb Park

Methylation of the CDH1 promoter as the second genetic hit in hereditary diffuse gastric cancer.

Aberrant promoter methylation and the associated loss of gene expression is a common accompaniment of human cancers. Nonetheless, it has been challenging to demonstrate in any given tumour that methylation of a specific gene was causal and not consequent to malignant transformation. In this regard, our attention was drawn to the genesis of gastric cancers in individuals with hereditary diffuse gastric cancer (HDGC). These individuals harbour germline mutations in the gene encoding E-cadherin, CDH1 (refs 2–4), but their cancers have consistently demonstrated absence of loss of heterozygosity at the CDH1 locus. These findings suggested the hypothesis that CDH1 promoter methylation might function as the ‘second genetic hit’ in the genesis of these cancers.

Nationwide Cancer Incidence in Korea, 1999~2001; First Result Using the National Cancer Incidence Database

PURPOSE The first Korean national population-based cancer registry using nationwide hospital-based recording system and the regional cancer registries provided the source to obtain national cancer incidences for the period 1999~2001. MATERIALS AND METHODS The incidence of cancer in Korea was calculated based on the Korea Central Cancer Registry database, data from additional medical record review survey, the Regional Cancer Registry databases, site-specific cancer registry databases, and cancer mortality data from the Korea National Statistical Office. Crude and age-standardized rates were calculated by sex for 18 age groups. RESULTS The overall crude incidence rates (CR) were 247.3 and 188.3 per 100,000 for men and women and the overall age-standardized incidence rates (ASR) were 281.2 and 160.3 per 100,000, respectively. Among men, five leading primary cancer sites were stomach (CR 58.6, ASR 65.6), lung (CR 42.1, ASR 50.9), liver (CR 41.9, ASR 44.9), colon and rectum (CR 24.2, ASR 27.3) and bladder (CR 7.7, ASR 9.2). Among women, the most common cancers were stomach (CR 30.8, ASR 25.8), breast (CR 25.7, ASR 21.7), colon and rectum (CR 19.6, ASR 16.7), uterine cervix (CR 18.4, ASR 15.5), and lung cancer (CR 15.1, ASR 12.4). In 0~14 age group, leukemia was most common for both sexes. For men, stomach cancer was most common in 15~64 age group, but lung cancer was more frequent for over 65 age group. For women, thyroid cancer in 15~34 age group, breast cancer in 35~64 age group, and stomach cancer in over 65 age group were most common for each age group. The proportions of death certificate only were 7.5% for men and 7.4% for women. CONCLUSION This is the first attempt to determine the national cancer incidence and this data will be useful to plan for research and national cancer control in Korea.

Identification of Genes with Differential Expression in Acquired Drug-Resistant Gastric Cancer Cells Using High-Density Oligonucleotide Microarrays

Purpose: A major obstacle in chemotherapy is treatment failure due to anticancer drug resistance. The emergence of acquired resistance results from host factors and genetic or epigenetic changes in the cancer cells. The purpose of this study was to identify differentially expressed genes associated with acquisition of resistance in human gastric cancer cells. Experimental Design: We performed global gene expression analysis in the acquired drug-resistant gastric cancer cell lines to the commonly used drugs 5-fluorouracil, doxorubicin, and cisplatin using Affymetrix HG-U133A microarray. The gene expression patterns of 10 chemoresistant gastric cancer cell lines were compared with those of four parent cell lines using fold-change and Wilcoxon’s test for data analysis. Results: We identified over 250 genes differentially expressed in 5-fluorouracil-, cisplatin-, or doxorubicin-resistant gastric cancer cell lines. Our expression analysis also identified eight multidrug resistance candidate genes that were associated with resistance to two or more of the tested chemotherapeutic agents. Among these, midkine (MDK), a heparin-binding growth factor, was overexpressed in all drug-resistant cell lines, strongly suggesting that MDK might contribute to multidrug resistance in gastric cancer cells. Conclusions: Our investigation provides comprehensive gene information associated with acquired resistance to anticancer drugs in gastric cancer cells and a basis for additional functional studies.

Down-regulation of Mitochondrial F1F0-ATP Synthase in Human Colon Cancer Cells with Induced 5-Fluorouracil Resistance

5-Fluorouracil (5-FU) is widely used for treatment of advanced colorectal cancer. However, it is common for such patients to develop resistance to 5-FU, and this drug resistance becomes a critical problem for chemotherapy. The mechanisms underlying this resistance are largely unknown. To screen for proteins possibly responsible for 5-FU resistance, cells resistant to 5-FU were derived from human colon cancer cell lines and two-dimensional gel electrophoresis–based comparative proteomics was done. Two-dimensional gel electrophoresis data showed there was lower expression of the α subunit of mitochondrial F1F0-ATP synthase (ATP synthase) in 5-FU–resistant cells compared with parent cells. Western blotting showed that expression of other ATP synthase complex subunits was also lower in 5-FU–resistant cell lines and that these resistant cells also showed decreased ATP synthase activity and reduced intracellular ATP content. The ATP synthase inhibitor, oligomycin A, strongly antagonized 5-FU–induced suppression of cell proliferation. When 5-FU sensitivity was compared with ATP synthase activity in six different human colon cancer cell lines, a positive correlation has been found. Furthermore, suppressed ATP synthase d-subunit expression by siRNA transfection increased cell viability in the presence of 5-FU. Bioenergetic dysfunction of mitochondria has been reported as a hallmark of many types of cancers (i.e., down-regulation of ATP synthase β-subunit expression in liver, kidney, colon, squamous oesophageal, and lung carcinomas, as well as in breast and gastric adenocarcinomas). Our findings show that ATP synthase down-regulation may not only be a bioenergetic signature of colorectal carcinomas but may also lead to cellular events responsible for 5-FU resistance.

Common variant in 6q26-q27 is associated with distal colon cancer in an Asian population

Background and aim Colorectal cancer (CRC) is a multifactorial disease with both environmental and genetic factors contributing to its development. The incidence of CRC is increasing year by year in Japan. Patients with CRC in advanced stages have a poor prognosis, but detection of CRC at earlier stages can improve clinical outcome. Therefore, identification of epidemiologial factors that influence development of CRC would facilitate the prevention or early detection of disease. Methods To identify loci associated with CRC risk, we performed a genome-wide association study (GWAS) for CRC and sub-analyses by tumour location using 1583 Japanese CRC cases and 1898 controls. Subsequently, we conducted replication analyses using a total of 4809 CRC cases and 2973 controls including 225 Korean subjects with distal colon cancer and 377 controls. Results We identified a novel locus on 6q26-q27 region (rs7758229 in SLC22A3, p=7.92×10−9, OR of 1.28) that was significantly associated with distal colon cancer. We also replicated the association between CRC and SNPs on 8q24 (rs6983267 and rs7837328, p=1.51×10−8 and 7.44×10−8, ORs of 1.18 and 1.17, respectively). Moreover, we found cumulative effects of three genetic factors (rs7758229, rs6983267, and rs4939827 in SMAD7) and one environmental factor (alcohol drinking) which appear to increase CRC risk approximately twofold. Conclusions We found a novel susceptible locus in SLC22A3 that contributes to the risk of distal colon cancer in an Asian population. These findings would further extend our understanding of the role of common genetic variants in the aetiology of CRC.

Establishment and characterization of human gastric carcinoma cell lines

We report 8 newly established gastric‐carcinoma cell lines (SNU‐216, 484, 520, 601, 620, 638, 668, 719) from Korean patients. Morphologic study was carried out using light and electron microscopes. CEA, αFP, and CA 19‐9 and TPA in supernatant and in cell lysate were measured by radioimmunoassay. p53 and c‐Ki‐ras gene mutations were screened and confirmed by sequencing. The cell lines, derived from tumors with moderate differentiation, grew as a diffuse monolayer, and those from tumors with poor differentiation and minimal desmoplasia grew exclusively as non‐adherent. Out of the 8 gastric‐cancer cell lines, 5 had detectable levels of CEA both in supernatant and in cell lysate; there was no expression or secretion of αFP in these cells; 4 cell lines showed high levels of CA 19‐9 in cell pellets. All cell lines except SNU‐484 had high concentrations of TPA both in cell lysate and in supernatants. p53 mutation was found in 6 cell lines (75%): 2 (SNU‐216 and SNU‐668) had mutations in exon 6, and other 3 in exon 8. The c‐Ki‐ras mutation was found in 2 cell lines (25%), SNU‐601 and SNU‐668. The former showed GGT‐to‐GAT transition mutation at codon 12, while the latter showed CAA‐to‐AAA transversion mutation at codon 61. DNA profiles using restriction endonuclease Hinfl and polymorphic DNA probes ChdTC‐15 and ChdTC‐114 showed different unique patterns; which suggests that these cell lines are unique and not cross‐contaminated. We believe that the newly characterized gastric‐cancer cell lines presented in this paper will provide a useful in vitro model for studies related to human gastric cancer. Int. J. Cancer, 70:0–0, 1997.

Long-term clinical course and prognostic factors in intestinal Behçet's disease.

PURPOSE: The present study was aimed at evaluating the long-term course of intestinal Behçets disease and determining predictive factors of prognosis. METHODS: This report is a retrospective study based on the records of 43 patients with intestinal Behçets disease. The mean follow-up duration was 73±60 months. We evaluated the efficacy of medical treatment for the intestinal lesion at initial eight weeks. The cumulative probabilities were calculated by using Kaplan-Meier method, and the results were compared by using the log-rank test. RESULTS: Sixteen patients (38 percent) achieved a complete remission of intestinal lesions eight weeks after medical treatment had begun. The patients who achieved a complete remission had a lower probability of receiving an operation than those who had not (13 percent at 2 and 5 yearsvs. 36 and 43 percent, respectively;P=0.028). The recurrence probability of intestinal lesions was 25 percent at two years and 49 percent at five years after complete remission with medical treatment. Patients who had a history of intestinal perforation or fistula had a higher probability of recurrence after operation than those without such history (59vs. 33 percent at 2 years; 88vs. 57 percent at 5 years;P=0.020). Patients who had taken azathioprine had a lower probability of receiving reoperation than those who did not (7vs. 25 percent at 2 years; 25vs. 47 percent at 5 years;P=0.035). The length of ileal resection and whether hemicolectomy was performed had no significant effect on the recurrence or reoperation rate. CONCLUSIONS: Intestinal Behçets disease frequently requires a surgical treatment and has a high recurrence rate. The patients who achieved a complete remission with medical treatment, who had no history of intestinal performation, and who received azathioprine after operation showed better clinical courses. Resection of a short segment of bowel would be a more appropriate surgical procedure.

Germline mutations of E-cadherin gene in Korean familial gastric cancer patients.

AbstractGastric cancer is the most common cancer in Korea. Germline mutations of the E-cadherin gene have recently been identified in familial gastric cancer patients. We screened five Korean familial gastric cancer patients to investigate germline mutations of the E-cadherin gene. These patients fulfilled the following criteria: presence of at least two gastric cancer patients within first-degree relatives and one patient diagnosed before the age of 50 years. Abnormal band patterns were found in exons 6 and 10 in two familial gastric cancer patients by polymerase chain reaction-single strand conformation polymorphism analysis (probands from the SNU-G2 and SNU-G1001 families, respectively). DNA sequencing analysis of the E-cadherin gene of these two patients revealed missense mutations in each exon. The SNU-G2 proband harbored a missense mutation from aspartic acid (GAT) to glycine (GGT) at codon 244 in exon 6 of the E-cadherin gene, and the SNU-G1001 proband had a missense mutation from valine (GTG) to alanine (GCG) at codon 487 in exon 10. The SNU-G2 proband was diagnosed with gastric cancer at the age of 38; three brothers and two sisters had died of gastric cancer under the age of 50, and their mother had died of gastric cancer at the age of 63. The SNU-G1001 proband was diagnosed with gastric cancer at the age of 42 and one brother had died of gastric cancer at the age of 49. In summary, we found germline mutations of the E-cadherin gene in two of five Korean familial gastric cancer patients screened.

Promoter hypermethylation downregulates RUNX3 gene expression in colorectal cancer cell lines.

It was recently reported that RUNX3 gene expression is significantly downregulated in human gastric cancer cells due to hypermethylation of its promoter region or hemizygous deletion (Cell, 109, 2002). To verify the genetic alterations and methylation status of the RUNX3 gene in colorectal carcinogenesis, we analysed for mutations, loss of heterozygosity (LOH), and RUNX3 gene promoter hypermethylation, in 32 colorectal cancer cell lines. RT–PCR analysis showed undetectable or low RUNX3 expression in 16 cell lines, and no mutations were found in the RUNX3 gene by PCR-SSCP analysis. Of these 16 cell lines, hypermethylation of the RUNX3 promoter was confirmed in 12. The following observations were made: (i) RUNX3 was re-expressed after 5-aza-2′-deoxycytidine treatment, (ii) the RUNX3 promoter was found to be methylated by MS-PCR, and (iii) hypermethylation of the RUNX3 promoter was confirmed by direct sequencing analysis after sodium bisulfite modification in the above 12 cell lines. RUNX3 was neither methylated nor expressed in four cell lines. Of these four, microsatellite instability (MSI) at the RUNX3 locus was found in three, SNU-61 (D1S246), SNU-769A, and SNU-769B (D1S199). This study suggests that transcriptional repression of RUNX3 is caused by promoter hypermethylation of the RUNX3 CpG island in colorectal cancer cell lines, and the results of these experiments may contribute to an understanding of the role of RUNX3 inactivation in the pathogenesis of colorectal cancers.

Cancer Incidence in Korea

PURPOSE We estimated the incidence of cancer in Korea. MATERIALS AND METHODS The indicence of cancer was estimated using national mortality data, and the incidence data from four frontier regional cancer registries, including Kangwha, Seoul, Busan and Deagu. These four registries served a population about seventeen million, which is almost 38% of entire population in Korea. RESULTS The overall age-standardized incidence rates (ASR) were 287.0 and 163.1 per 100,000 for males and females, respectively. Among males, stomach cancer was the most frequent (ASR 69.6), followed by lung cancers, including bronchus cancer (ASR 54.5), liver cancer (ASR 47.0) and colo-rectal cancer (ASR 25.2). The most frequent sites of cancer in females, by rank order, were stomach (ASR 26.8), breast (ASR 20.1), uterine cervix (ASR 18.0), colo-rectum (ASR 15.9), lung (ASR 13.0) and liver (ASR 12.0). CONCLUSION It is hoped that these results will provide valuable leads for cancer research and cancer control in Korea.