Showing papers by "Sug Hyung Lee published in 2005"

PIK3CA gene is frequently mutated in breast carcinomas and hepatocellular carcinomas

Abstract: A recent report revealed that phosphoinositide-3-kinase, catalytic, alpha (PIK3CA) gene is somatically mutated in several types of human cancer, suggesting the mutated PIK3CA gene as an oncogene in human cancers. However, because the previous report focused the mutational search primarily on colon cancers, the data on PIK3CA mutations in other types of human cancers have been largely unknown. Here, we performed mutational analysis of the PIK3CA gene by polymerase chain reaction-single-strand conformation polymorphism assay in 668 cases of common human cancers, including hepatocellular carcinomas, acute leukemias, gastric carcinomas, breast carcinomas, and non-small-cell lung cancers. We detected PIK3CA somatic mutations in 26 of 73 hepatocellular carcinomas (35.6%), 25 of 93 breast carcinomas (26.9%), 12 of 185 gastric carcinomas (6.5%), one of 88 acute leukemias (1.1%), and three of 229 non-small-cell lung cancers (1.3%). Some of the PIK3CA mutations were detected in the early lesions of breast cancer carcinoma, hepatocellular carcinoma, and gastric carcinomas, suggesting that PIK3CA mutation may occur independent of stage of the tumors. The high incidence and wide distribution of PIK3CA gene mutation in the common human cancers suggest that alterations of lipid kinase pathway by PIK3CA mutations contribute to the development of human cancers.

Increased expression of histone deacetylase 2 is found in human gastric cancer

Abstract: Accumulated evidence has established that aberrant regulation of histone deacetylases (HDACs) is one of the major causes of the development of human malignancies. Among different iso-enzymes of HDAC and sirtuins grouped as the HDAC super family, little is known as to how histone deacetylase 2 (HDAC2) causes carcinogenesis in solid tumors. Here, in order to investigate the possible role of HDAC2 in gastric carcinogenesis, we analyzed the expression of HDAC2 in 71 gastric adenocarcinomas by immunohistochemistry. Moderate to strong expression of HDAC2 was found in 44 (62%) out of a total of 71 tumors. The majority of positive tumors, which were detected in the nucleus but not in normal gastric epithelium, did not express HDAC2 or showed only weak positive staining. Interestingly, we also noted that HDAC2 expression appeared to be associated with tumor aggressiveness as HDAC2 expression was observed to be statistically significant in advanced gastric cancer (P=0.0023, Chi-square test) and in positive lymph node metastasis (P=0.0713, Chi-square test). Taken together, these results suggest that HDAC2 may play an important role in the aggressiveness of gastric cancer.

Somatic Mutations of EGFR Gene in Squamous Cell Carcinoma of the Head and Neck

Abstract: Purpose: Recently, the kinase domain mutations of epidermal growth factor receptor ( EGFR ) gene have been identified in non–small-cell lung cancer, and these mutations have been related to the clinical response to the tyrosine kinase inhibitor gefitinib. Gefitinib treatment has also shown clinical benefits in squamous cell carcinoma of the head and neck (SCCHN). The aim of this study was to explore the possibility that SCCHN harbored the EGFR mutations. Experimental Design: In this study, we analyzed EGFR gene in 41 SCCHN for the detection of the somatic mutations by PCR-single-strand conformational polymorphism analysis. Results: Overall, we detected three EGFR mutations (7.3%), and all of the mutations were the same in-frame deletion mutation in exon 19 (E746_A750del). Conclusion: These data indicated that in addition to non–small-cell lung cancer, SCCHN harbors the EGFR gene mutations, and suggested the rationale for the clinical applicability of gefinitib to SCCHN patients.

CASPASE-8 gene is inactivated by somatic mutations in gastric carcinomas.

Abstract: Several lines of evidence indicate that deregulation of apoptosis is involved in the mechanisms of cancer development. Caspase-8 activation plays a central role in the initiation phase of apoptosis. The aim of this study was to explore the possibility that genetic alteration of CASPASE-8 gene is involved in the development of human cancers, including gastric cancers. We have analyzed the entire coding region of human CASPASE-8 gene for the detection of somatic mutations in 162 gastric carcinomas (40 early and 122 advanced cancers), 185 non-small cell lung cancers, 93 breast carcinomas, and 88 acute leukemias by PCR-single-strand conformation polymorphism. Of the cancers analyzed, 13 cancers harbored CASPASE-8 somatic mutations. Interestingly, all of the mutations were detected in the advanced gastric cancers (10.7% of the 122 samples). We expressed the tumor-derived caspase-8 mutants in 293T, 293, and HT1080 cells and found that most of the mutants (9 of the 10 mutations tested) markedly decreased the cell death activity of caspase-8. In addition, in the cells with the inactivating caspase-8 mutants, cleavage of poly(ADP-ribose)polymerase was markedly reduced compared with that of wild-type caspase-8. The occurrence of CASPASE-8 mutation and the inactivation of cell death activity by the mutants suggest that CASPASE-8 gene mutation may affect the pathogenesis of gastric cancers, especially at the late stage of gastric carcinogenesis.

Caspase-8 gene is frequently inactivated by the frameshift somatic mutation 1225_1226delTG in hepatocellular carcinomas.

Abstract: Evidence exists that alterations of the genes encoding apoptosis-related proteins contribute to either development or progression of human cancers. Caspase-8 plays a crucial role in the initiation phase of apoptosis. To explore the possibility that the genetic alteration of caspase-8 gene is involved in the development of hepatocellular carcinomas (HCCs), we have analysed the entire coding region of human caspase-8 gene for the detection of somatic mutations by polymerase chain reaction-single-strand conformation polymorphism in 69 HCCs with low-grade dysplastic nodule (LGDN, n=2) or high-grade dysplastic nodule (HGDN, n=2) or without any dysplastic nodules (n=65). Overall, we detected a total of nine somatic mutations in 69 HCCs (13.0%). Interestingly, all of the nine mutations were an identical frameshift mutation with two base-pair deletion (1225_1226delTG), which would result in a premature termination of amino-acid synthesis in the p10 protease subunit. In a patient sample, we detected the 1225_1226delTG mutation both in HCC and LDGN lesions, suggesting that caspase-8 mutation could be involved in the early stage of HCC carcinogenesis. We expressed the tumor-derived caspase-8 mutant in the cells and found that the mutant abolished cell death activity of caspase-8. Our data indicate that caspase-8 gene is frequently mutated in HCC and the majority of the mutations may be the frameshift mutation 1225_1226delTG. Also, the data suggest that caspase-8 gene mutation might lead to the loss of its cell death function and contribute to the pathogenesis of HCC.

Mutational analysis of EGFR and K-RAS genes in lung adenocarcinomas

Abstract: Both epidermal growth factor receptor (EGFR) and RAS gene mutations contribute to the development of non-small cell lung cancer (NSCLC). Because RAS is one of the downstream molecules in the EGFR signal transduction, the association between the somatic mutations of EGFR and RAS may be important in the pathogenesis of NSCLC . However, to date, such data are lacking. In this study, we analyzed the hotspot regions of K-RAS gene (codons 12, 13, 59 and 61) and EGFR gene (exons 18, 19 and 21) in 153 NSCLC tissue samples including 69 adenocarcinomas. Overall, we detected 30 EGFR mutations (19.6%) and 6 K-RAS mutations (3.9%) in the 153 NSCLCs. In the 69 adenocarcinomas, 26 EGFR mutations (37.7%) and six K-RAS mutations (8.7%) were detected. Of note, the 26 tumors with EGFR mutations did not harbor any K-RAS mutations, and the six tumors with K-RAS mutations did not harbor any EGFR mutations. Inverse relationship between K-RAS and EGFR mutations in the lung adenocarcinoma was statistically significant (P=0.046, χ2 test). As regards smoking history, EGFR mutation was significantly associated with never-smoking history, whereas K-RAS mutation was significantly associated with smoking history. Our data suggest that mutations of EGFR and K-RAS genes might separately, but not cooperatively, contribute to lung adenocarcinoma pathogenesis, and that EGFR and K-RAS mutants could separately be anti-neoplastic targets in lung adenocarcinomas.

Absence of EGFR mutation in the kinase domain in common human cancers besides non-small cell lung cancer.

Abstract: somatic mutations in the adenocarcinomas, bronchioloalveolarcarcinomas and large cell carcinomas of lung that all correlatedwith a clinical response to gefitinib. The mutations were de-tected in the exon 18, 19 and 20 that encode the intracellularkinase domain. The mutations detected in the exon 18 wouldsubstitute the amino acid G719 in the P-loop, while thosedetected in the exon 21 would substitute amino acids in theactivation domain. The mutations in the exon 19 were in-framedeletions that may alter the structure of C helix. All of the

Mutations of beta-catenin and AXIN I genes are a late event in human hepatocellular carcinogenesis.

Abstract: Background: Hepatocellular carcinoma (HCC) is a well-known cancer involving the Wnt pathway in its carcinogenesis. Aims: However, it is not clear whether these genetic changes are early genetic events in hepatocarcinogenesis or not. Method: In this study, we performed mutational analysis of the β-catenin and AXIN I genes, and immunohistochemistry for β-catenin in a series of 114 hepatocellular nodular lesions, including premalignant lesions such as low-grade dysplastic nodules (LGDNs) and high-grade dysplastic nodules (HGDNs). Results: In the present study, mutations of the β-catenin and AXIN I genes were detected in 16% (13 out of 81) and 6.2% (five of 81) of the HCCs, respectively. However, no mutations were found in 14 LGDNs and 19 HGDNs. Moreover, abnormal nuclear β-catenin immunostaining was observed in 30 of 81 HCCs, but not in dysplastic nodules. Conclusion: Taken together, our data suggest that β-catenin stabilization because of either β-catenin or AXIN I mutation might be a late event for malignant progression rather than an early genetic event involving the initiation of HCC development.

Hypermethylation of the RUNX3 gene in hepatocellular carcinoma

Abstract: Methylation events play a critical role in various cellular processes including regulation of gene transcription and proliferation. Recently, RUNX3 gene, one of TGF-beta-Smads signaling transduction pathway genes, showed strong tumor-suppressor activity by regulation of epithelial proliferation and apoptosis. To elucidate the potential etiological role of the RUNX3 gene in the development of hepatocellular carcinoma (HCC), we have analyzed the methylation status of 5' CpG island of the RUNX3 gene in a series of 73 HCC tissues and 11 liver cell lines. Expectedly, promoter methylation of RUNX3 gene was found in 2 (2.7%) of 73 corresponding normal liver, whereas 30 (41.1%) of 73 HCCs and 4 (40%) of 10 liver cancer cell lines showed hypermethylation of the gene, respectively. There was no significant difference between promoter hypermethylaion and clinicopathologic parameters of primary HCC samples, including histologic grade, microvascular invasion, and clinical stage. Interestingly, demethylating agent 5-aza-2-deoxycytidine induced reactivation and more potent expression of RUNX3 gene in HCC cell lines. Our findings indicate that promoter hypermethylation of RUNX3 gene may occur as an early event in the development of HCC and that methylation may be a major mechanism for inactivation of RUNX3 gene in HCC.

Mutational analysis of the ARAF gene in human cancers.

Abstract: Deregulation of RAS signal transduction has been implicated in the malignant growth of human cancer cells. The BRAF gene, encoding a RAF family member in the downstream pathway of RAS, is somatically mutated in a number of human cancers, raising the possibility that other RAF family members might be mutated in human cancers. In this study we analyzed the genomic DNAs for the detection of somatic mutations of the ARAF gene in 60 human cancer cell lines and 323 primary human cancer tissues, including colorectal carcinomas, gastric carcinomas, ovarian tumors and acute leukemias. The MOLT-4 leukemia cell line was found to harbor an ARAF gene mutation resulting in an amino acid substitution (A451T) at the activation segment in the kinase domain of ARAF. In the cancer tissues we could not detect any ARAF gene mutation. Our data indicate that, in contrast to the BRAF gene, the ARAF gene is rarely mutated in human cancers, and suggest that alterations of the RAS pathway by ARAF gene mutation may not play an important role in the pathogenesis of human cancers.

ArrayCyGHt: a web application for analysis and visualization of array-CGH data

Abstract: Summary: ArrayCyGHt is a web-based application tool for analysis and visualization of microarray-comparative genomic hybridization (array-CGH) data. Full process of array-CGH data analysis, from normalization of raw data to the final visualization of copy number gain or loss, can be straightforwardly achieved on this arrayCyGHt system without the use of any further software. ArrayCyGHt, therefore, provides an easy and fast tool for the analysis of copy number aberrations in any kinds of data format. Availability: ArrayCyGHt can be accessed at http://genomics.catholic.ac.kr/arrayCGH/ Contact: yejun@catholic.ac.kr Supplementary information: Technical documentation is available. See http://genomics.catholic.ac.kr/arrayCGH/

ERBB2 kinase domain mutation in a gastric cancer metastasis.

Abstract: ERBB2 is a member of the epidermal growth factor receptor (EGFR) family. Recent studies revealed that the kinase domain of the ERBB2 gene was mutated in human cancers, including gastric cancer. Despite the importance of cancer metastasis in the pathogenesis of cancers, data on the ERBB2 kinase domain mutation in cancer metastasis are lacking. In this study, to explore the possibility that ERBB2 mutation is involved in the metastasis mechanism, we analyzed the kinase domain of ERBB2 for the detection of somatic mutations in 58 gastric adenocarcinomas with lymph node metastasis. We found one ERBB2 mutation, which was detected in the lymph node metastasis, but not in the primary tumor of the same patient. The ERBB2 mutation was a missense mutation which substituted an amino acid in exon 21 (V832I). We simultaneously analyzed the somatic mutations of EGFR, K-RAS, PIK3CA and BRAF genes in the sample with the ERBB2 mutation, and found that this metastatic carcinoma did not harbor any of the mutations. Our data suggest that ERBB2 kinase domain mutation occasionally occurs in metastatic gastric carcinoma and might play a role in the metastatic process of some gastric carcinomas.

Absence of the ERBB2 kinase domain mutation in lung adenocarcinomas in Korean patients.

Abstract: Dear Sir, Protein tyrosine kinases regulate cell-signaling pathways that mediate a number of processes in tumor survival and growth activity. Epidermal growth factor receptor (EGFR) is a prototypical receptor tyrosine kinase, and the EGFR gene is the mammalian equivalent of the avian viral oncogene v-erb. Two research groups have discovered that lung adenocarcinomas (including bronchioloalveolar carcinomas) harbor EGFR gene mutations. In addition, the EGFR gene mutations in lung cancers could predict significant clinical responses to gefitinib (Iressa), an orally active EGFR tyrosine kinase inhibitor that has given significant clinical benefit to a subset of lung cancer patients. EGFR mutations have been detected in the exons that encode the intracellular kinase domain.

Death Receptor Mutations

Abstract: It is generally believed that human cancers may arise as the result of an accumulation of mutations in genes and subsequent clonal selection of variant progeny with increasingly aggressive behaviors. Also, among the remarkable advances in our understanding in cancer biology is the realization that apoptosis has a profound effect on the malignant phenotypes. Along with these, compelling evidence indicates that somatic mutations in the genes encoding apoptosis-related proteins contribute to either development or progression of human cancers. In this chapter, we present an overview of the death receptor pathway and its dysregulation in cancers. We then review the current knowledge of death receptor mutations that have been detected in humans.

Kinase domain mutation of NTRK3 gene is uncommon in gastric carcinomas.

Abstract: Protein kinases regulate intracellular signal-trans-duction pathway mediating cell proliferation, differ-entiation and survival [1]. Protein kinase family isone of the most frequently mutated gene familyfound in human cancers and thus are potentialtherapeutic targets for human cancers [1]. Neuro-trophic tyrosine kinase receptor type 3 (NTRK3),also referred to as TrkC, is a receptor tyrosine kinaseand plays an important role in the development ofneural tissues [2]. NTRK3 expression is not re-stricted to neural tissues, and various types of tissues,including the gastrointestinal epithelia (stomach,small intestine and colon), have also been shown toexpress NTRK3 [3]. These data suggest a role ofNTRK3 in the growth and maintenance of thegastrointestinal cells.Recently, Bardelli et al. [4] analyzed 138 tyrosinekinase genes in 147 colorectal cancer tissues for thedetection of the somatic mutations. They identified46 mutations in 14 genes. Of those, seven genes(NTRK3,FES,KDR,EPHA3,NTRK2, MLK4andGUCY2F) were mutated in more than one tumor.NTRK3 gene mutations were found in six (4.1%) ofthe 147 colorectal cancers. Of note, the NTRKmutations were exclusively identified in the kinasedomain. Because NTRK3 is expressed in gastricepithelium as well as in colorectal epithelium [3], wehypothesized that gastric carcinomas might alsoharbor NTRK3 mutation. To see whether alterationof NTRK3 gene is involved in the tumorigenesis ofgastric carcinoma, we analyzed NTRK3 gene for thedetection of somatic mutations in gastric carcinomasby polymerase chain reaction (PCR)-based singlestrand conformation polymorphism (SSCP) assay.We analyzed methacarn-fixed tissues of 140 gas-tric carcinomas. All of the patients of the cancerswere Asians (Koreans). The gastric carcinomasconsisted of 60 diffuse-type, 49 intestinal-type and31 mixed-type gastric adenocarcinomas by Lauren’sclassification, and 25 early and 115 advanced gastriccarcinomas according to the depth of invasion.Malignant cells and normal cells from the samepatients were selectively procured from hematoxylinand eosin-stained slides using a 30G1/2 hypodermicneedle (Becton Dickinson, Franklin Lakes, NJ)affixed to a micromanipulator, as described pre-viously [5]. DNA extraction was performed by amodified single-step DNA extraction method [5].Because NTRK3 mutations were previously de-tected only in the exons 15