Biomedical subjects

S G Chi

Publications and source records attributed to S G Chi.

At least 19 recordsLinked to original sources

PubMed2001

Frequent epigenetic inactivation of RASSF1A by aberrant promoter hypermethylation in human gastric adenocarcinoma.

Methylation associated inactivation of RASSF1, a putative tumor suppressor identified at 3p21.3, has been frequently observed in several human malignancies, including lung and breast cancers. To explore the penetrance of RASSF1 in gastric carcinogenesis, we performed expression and mutation analyses of 3 isotypes of RASSF1 (A, B, and C) in 150 gastric specimens, including 15 carcinoma cell lines. RASSF1A and RASSF1B transcripts were not expressed in 60% (9 of 15) and 33% (5 of 15) of gastric carcinoma cell lines, respectively, whereas RASSF1C was detectable in all cell lines. Bisulfite DNA sequencing analysis revealed that the CpG island in the RASSF1A promoter is hypermethylated in all RASSF1A-nonexpressing cell lines. In addition, both RASSF1A and RASSF1B were re-expressed by treatment with the demethylating agent 5-aza-2'-deoxycytidine. Among 90 primary gastric adenocarcinomas examined, 41 (46%) and 19 (21%) expressed no or abnormally low levels of RASSF1A and RASSF1B, respectively, and 12 (13%) tumors showed no expression of both isoforms. Loss or abnormal down-regulation of RASSF1A correlated with tumor stage and grade but not with histological types of tumors. Methylation-specific PCR analysis demonstrated that 95% (39 of 41) of RASSF1A-nonexpressing primary tumors are methylated at the CpG sites in the promoter, whereas none of the adjacent noncancerous or normal tissues are methylated. No somatic mutations were detected in RASSF1 transcripts expressed in unmethylated tumors. However, 10 methylated tumors, including 4 cell lines, showed low genomic levels of RASSF1 and expressed no RASSF1A transcripts, suggesting that RASSF1A inactivation might be caused by both epigenetic and genetic mechanisms in a subset of gastric adenocarcinomas. In conclusion, our data indicate that epigenetic transcriptional silencing of RASSF1, especially RASSF1A isoform, is a frequent event in gastric tumorigenesis and might play an important role in the malignant progression of gastric adenocarcinomas.

Adenocarcinoma↗

PubMed2001

Frequent epigenetic inactivation of RASSF1A in human bladder carcinoma.

Allelic deletion or transcriptional silencing of RASSF1, a putative tumor suppressor at 3p21.3, has been found in a considerable proportion of lung, breast, and ovarian cancers. In this study, we analyzed the expression and mutation status of three RASSF1 isoforms (-A, -B, and -C) in 55 primary bladder carcinomas and 10 bladder and prostate cancer cell lines. The RASSF1A transcript was not found in 80% (4 of 5) and 100% (4 of 4) of bladder and prostate cell lines, respectively. Compared with normal bladder tissues, loss or significant reduction of RASSF1A was identified in 62% (34 of 55) of primary bladder carcinomas and 10 (83%) of 12 matched sets showed tumor-specific alteration of RASSF1A expression. Moreover, loss or abnormal down-regulation of RASSF1A correlated with advanced tumor stage. RASSF1B was undetectable in 60% (3 of 5) of bladder cell lines and in 31% (17 of 55) of primary tumors, but none of these tumors showed altered expression exclusively in RASSF1B. RASSF1C transcript was detected in all cell lines and primary tumors we examined. Expression of RASSF1A and RASSF1B was reactivated in all nonexpressor cell lines by treatment with the demethylating agent 5-aza-2'-deoxycytidine. Bisulfite DNA sequencing analysis revealed that aberrant hypermethylation at the CpG island in the RASSF1A promoter is strongly associated with the loss of RASSF1A expression in cell lines and uncultured primary tumors. Methylation-specific PCR and BstUI digestion analyses also demonstrated that 97% (33 of 34) of RASSF1A-nonexpressing primary tumors are methylated. Although somatic mutations were not identified in RASSF1 transcripts expressed in unmethylated tumors, 24% (9 of 37) of methylated cell lines and primary tumors showed detectable reductions in genomic levels of RASSF1, suggesting that RASSF1A inactivation might be caused by both epigenetic and genetic mechanisms in a subset of bladder tumors. Together, our data suggest that RASSF1A inactivation may play a critical role in the malignant progression of human bladder carcinomas.

Adult↗

PubMed2001

Increased expression of cFLIP(L) in colonic adenocarcinoma.

During tumour progression, cancer cells use diverse mechanisms to escape from apoptosis-inducing stimuli, which may include receptor internalization, inhibition of signal pathways, and regulation of specific sets of genes. Substantial numbers of colon cancer cells have been observed to express Fas/Fas ligand, but are resistant to Fas-mediated apoptosis, suggesting that colonic tumours might develop specific mechanisms to overcome Fas-mediated apoptosis. Recently, cellular FLICE-like inhibitory protein (cFLIP) has been identified as an endogenous inhibitor of Fas- or other receptor-mediated apoptosis and its altered high expression has a suspected association with tumour development or progression. In an effort to investigate the prevalence of cFLIP(L) alterations in colon carcinomas and their possible implications for the progression of colon cancers, cFLIP(L) expression was analysed in adenocarcinomas and adenomatous polyps of colon, with matched normal tissues, at RNA and protein levels, by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. cFLIP(L) transcripts were constitutively expressed in colon cancers and expression levels were significantly higher in carcinomas than in normal tissues (p<0.05). Overexpression of cFLIP(L) protein was found exclusively in carcinoma cells in all matched sets analysed and approximately three-fold induction was detected in cancer cells (p<0.05). The expression of cFLIP(L) protein was not significantly altered in adenomatous polyps compared with normal tissues. Taken together, these results strongly suggest that abnormal overexpression of cFLIP(L) is a frequent event in colon carcinomas and might contribute to in vivo tumour transformation.

Adenocarcinoma↗

PubMed2001

Costunolide induces apoptosis by ROS-mediated mitochondrial permeability transition and cytochrome C release.

Costunolide is an active compound isolated from the root of Saussurea lappa Clarks, a Chinese medicinal herb, and is considered a therapeutic candidate for various types of cancers. Nevertheless, the pharmacological pathways of costunolide are still unknown. In this study, we investigate the effects of costunolide on the induction of apoptosis in HL-60 human leukemia cells and its putative pathways of action. Using apoptosis analysis, measurement of reactive oxygen species (ROS), and assessment of mitochondrial membrane potentials, we show that costunolide is a potent inducer of apoptosis, and facilitates its activity via ROS generation, thereby inducing mitochondrial permeability transition (MPT) and cytochrome c release to the cytosol. ROS production, mitochondrial alteration, and subsequent apoptotic cell death in costunolide-treated cells were blocked by the antioxidant N-acetylcystein (NAC). Cyclosporin A, a permeability transition inhibitor, also inhibited mitochondrial permeability transition and apoptosis. Our data indicate that costunolide induces the ROS-mediated mitochondrial permeability transition and resultant cytochrome c release. This is the first report on the mechanism of the anticancer effect of costunolide.

Animals↗

PubMed2001

Overexpression of p53 and absent genetic mutation in clear cell chondrosarcoma.

Clear cell chondrosarcoma is one of the extremely rare chondrosarcomas. The pathogenesis and the molecular genetic events, which contribute to the development of clear cell chondrosarcoma, are not well elucidated, due in part to the lack of sufficient tumor tissue available. To characterize the involvement of the p53 gene abnormality in this disease, we analyzed expression and sequence alteration of p53 by immunohistochemical analysis of the protein expression and quantitative DNA/PCR and PCR-SSCP assays of the gene in 28 paraffin-embedded tissue specimens. Immunohistochemical analysis demonstrated that 7 (25%) showed patchy positive nuclear staining for p53 and 5 (18%) showed diffuse positive nuclear staining patterns. Sixteen (57%) were negative for p53 immunostaining. Quantitative DNA/PCR analysis revealed that none of the cases we studied showed significantly reduced levels of p53 amplification (<0.50), strongly suggesting an allelic deletion of the p53 gene. In contrast, however, DNA/PCR-SSCP analysis failed to detect any types of mutations resulting in amino acid substitution within exons 5-9 regions of the gene. Taken together, our data suggest that genetic alteration of p53 is a relatively rare event in clear cell chondrosarcomas but a substantial fraction of this type of tumors carries abnormal overexpression of p53, which might result from an as yet unidentified mechanism(s).

Chondrosarcoma↗

PubMed2001

Low incidence of genetic alterations of the p16CDKN2a in clear cell chondrosarcoma.

Mutational inactivation of the cyclin-dependent kinase inhibitors (CDKIs) (p16CDKN2a) tumor suppressor gene has been found in a variety of human tumor types. To investigate the involvement of CDKI abnormality in clear cell chondrosarcoma, alterations of CDKIs were examined in clear cell chondrosarcoma tissues using a quantitative DNA/PCR, PCR-SSCP. Two of 38 specimens (5.2%) we analyzed showed abnormally low levels of p16CDKN2a amplification, suggesting that the allelic deletion of the gene might be low frequent event in progression of this tumor. For detection of subtle sequence alterations such as point mutations, we performed SSCP analysis of the entire coding region of the p16CDKN2a gene. No altered SSCP patterns were found in 38 clear cell chondrosarcoma specimens. This study reflects the very low incidence of genetic alterations of the p16CDKN2a gene in clear cell chondrosarcoma. Therefore, we conclude that the alteration of the p16CDKN2a gene is not involved significantly in the development of clear cell chondrosarcoma.

Bone Neoplasms↗

PubMed2000

Frequent alteration of p63 expression in human primary bladder carcinomas.

p63, a recently identified member of the p53 gene family, encodes multiple products with transactivating, death-inducing, and dominant-negative activities. To explore the penetrance of p63 in bladder carcinogenesis, we performed expression and mutation analyses of two major isotypes, TAp63 and deltaNp63, in 63 bladder specimens. In 12 normal tissues, TAp63 was expressed at an easily detectable level whereas deltaNp63 was absent or extremely low. While none of 47 carcinomas showed allelic deletion of the gene, marked reduction of TAp63 and abnormal overexpression of deltaNp63 were found in 25 (53.2%) and 30 (63.8%) carcinomas, respectively. Tumor-specific alteration of TAp63 and deltaNp63 expression was identified in two and three of six matched sets, respectively. In addition, reduced expression of TAp63 showed a correlation with tumor stage and grade. Abnormal expression of TAp63 or deltaNp63 isoform was also observed in three of four cell lines, and treatment with 5-Aza-2'-deoxycytidine led to up- or down-regulation of TAp63 and/or deltaNp63 expression, suggesting that the promoters of both isoforms might be affected by DNA methylation, but not in a reciprocal fashion. No sequence alteration of p63 was identified in 47 carcinomas whereas 17 (34.8%) of these showed p53 mutations, and no association between p63 expression and the mutational status of p53 or expression of p21Waf1, MDM2, and 14-3-3sigma was recognized. Our data suggest that altered expression of p63 is a frequent event in bladder carcinogenesis and might contribute to the progression of bladder tumors, possibly via the mechanism(s) distinct from the p53 pathway.

Antimetabolites, Antineoplastic↗

PubMed2000

Mitogenic conversion of transforming growth factor-beta1 effect by oncogenic Ha-Ras-induced activation of the mitogen-activated protein kinase signaling pathway in human prostate cancer.

Elevated expression of transforming growth factor (TGF)-beta1 has been implicated in prostate tumorigenesis despite its growth-inhibitory effect on normal epithelial and carcinoma cells of the prostate. In this study, we identified that G1-to-S transition of the cell cycle is stimulated by TGF-beta1 in the prostate cancer cell line TSU-Pr1. No mutation of signal mediators, including Smads, and induction of PAI-1 transcription indicated that the TGF-beta1 signaling cascade is functionally intact in this cell line. Whereas pharmacological inhibitors of various mitogenic signaling pathways showed no effects, blockade of the mitogen-activated protein kinase (MAPK) pathway by the MAPK kinase 1 inhibitor PD98059 restored the growth inhibitory role of TGF-beta1 in TSU-Pr1, which carries an oncogenic mutation in Ha-Ras (V12). Moreover, expression of antisense Ha-Ras or dominant negative Raf-1 abrogated the mitogenic effect of TGF-beta1 in TSU-Pr1, and the TGF-beta1 inhibition of DU145 was switched to stimulation by V12Ha-Ras transfection. Whereas the negative growth regulation by TGF-beta1 was completely inhibited by dominant negative Smad2, Smad3, or Smad4, its mitogenic effect was not affected, suggesting that this action is Smad-independent. Interestingly, whereas the TGF-beta1-mediated up-regulation of p15INK4B and p21WAF1 transcription was abolished in TSU-Pr1 and V12Ha-Ras-transfected DU145, inhibition of the Ras/MAPK pathway restored the TGF-beta1 induction of these genes. Taken together, our data suggest that prostate carcinomas with the Ras/MAPK pathway activation might have a selective growth advantage by autocrine TGF-beta1 production.

Cell Cycle↗

PubMed2000

Mutational alterations of the p16CDKN2A tumor suppressor gene have low incidence in mesenchymal chondrosarcoma.

Mutational inactivation of the cyclin-dependent kinase inhibitors (CDKIs) (p16INK4A/MTS1) tumor suppressor gene has been found in a variety of human tumor types. To investigate the involvement of CDKI abnormality in mesenchymal chondrosarcoma, alterations of CDKIs were examined in human mesenchymal chondrosarcoma tissues using a quantitative DNA/PCR, PCR-SSCP. Seven of 33 specimens (21.2%) showed abnormally low levels of p16CDKN2A amplification, suggesting that the allelic deletion of the gene might be a less frequent event in progression of this tumor. To detect subtle sequence alterations such as point mutations, SSCP analysis of the entire coding region of the p16CDKN2A gene, exons 1, 2, and 3 regions, showed no altered SSCP patterns in 33 mesenchymal chondrosarcoma specimens. A low incidence of genetic alterations of the p16CDKN2A was found in mesenchymal chondrosarcoma. Through this study, we conclude that alteration of the p16CDKN2A gene does not participate significantly in the tumorigenesis of mesenchymal chondrosarcoma.

Base Sequence↗

PubMed2000

Loss of imprinting and elevated expression of wild-type p73 in human gastric adenocarcinoma.

The p73 gene located at 1p36.3 encodes for a protein with significant similarity to p53. To investigate the penetrance of p73 in gastric carcinogenesis, we analyzed the expression, allelotype, and mutation of p73 in five cell lines and 75 tissues. Although extremely low levels of p73 expression were observed in all noncancerous gastric tissues and four of five cell lines, a significant elevation of p73 was detected in 37 of 39 (94.9%) carcinoma tissues. Furthermore, a tumor-specific increase of p73 was identified in 14 of 16 (87.5%) matched sets. Allelotyping analysis using a StyI or BanI polymorphism revealed that 5 of 21 (23.8%) informative carcinomas, but none of 19 noncancerous cases, express p73 biallelically, suggesting the transcriptional activation of a silent allele in a subset of cancers. Whereas the transcription of an active allele was markedly induced by serum starvation or clump formation of the cells, treatment with 5-aza-2'deoxycytidine activated a silent allele with a subsequent up-regulation of an active allele, supporting the genomic imprinting and autoregulation of the gene. Allelic deletion or mutation of the gene was not found, and no association of p73 expression with the mutational status of p53 or expression of p21Waf1 was recognized. Taken together, this study argues that p73 is not a target of genetic alteration in gastric carcinogenesis and suggests that overexpression of p73 might be triggered by physiological stresses accompanied with outgrowth of tumors, such as hypoxia or nutrient deprivation.

Adenocarcinoma↗

PubMed1999

TGF-beta1 inhibition of apoptosis through the transcriptional up-regulation of Bcl-X(L) in human monocytic leukemia U937 cells.

To characterize the TGF-beta1 response of monocytic leukemia cells, we analyzed the effects of TGF-beta1 on cell proliferation, differentiation, and apoptosis of human monoblastic U937 cells. Treatment of cells with TGF-beta1 in the absence of growth factors significantly enhanced cell viability. Flow cytometric analysis of DNA content and CD14 expression revealed that TGF-beta1 does not affect cell proliferation and differentiation. Consistent with these results was the finding that no transcriptional induction of Cdk inhibitors such as p21Waf1, p15Ink4b, and p27Kip1 was detected following TGF-beta1 treatment. Interestingly, however, pretreatment of TGF-beta1 significantly inhibited Fas-, DNA damage-, and growth factor deprivation-induced apoptosis. This antiapoptotic effect was totally abrogated by anti-TGF-beta1 antibody. Quantitative RT-PCR analysis demonstrated a dose- and time-dependent transcriptional up-regulation of Bcl-X(L), suggesting its implication in the TGF-1-mediated antiapoptotic pathway. We also observed elevated expression of c-Fos and PTEN/MMAC1. But, no detectable change was recognized in expression of c-Jun, Fas, Fadd, Fap-1, Bcl-2, and Bax. Taken together, our study shows that TGF-beta1 enhancement of cellular viability is associated with its antiapoptotic effect, which may result from the transcriptional up-regulation of Bcl-X(L).

Apoptosis↗

PubMed1999

Elevated and biallelic expression of p73 is associated withprogression of human bladder cancer.

p73, a member of the p53 family at 1p36.3, has been demonstrated to be expressed monoallelically and induce apoptosis or G1 arrest of the cell cycle. To explore the candidacy of p73 as a suppressor in bladder tumorigenesis, we examined expression level, allelic origin, and mutation of p73 mRNA in 45 primary bladder carcinomas. Quantitative PCR analysis showed no allelic loss of the gene but showed various levels of mRNA expression in both carcinoma and noncancerous tissues. Elevated expression of p73 was frequently observed in carcinoma tissues [18 (40.0%) of 45] and showed a strong correlation with tumor stage or grade. Allotyping analysis using a StyI polymorphism detected biallelic expression in 12 (52.2%) of 23 heterozygous carcinomas but none in 4 noncancerous tissues. Tumor-specific biallelic expression was also identified from one matched set. In addition, 8 (66.7%) of these 12 expressed high levels of p73 mRNA, whereas only 2 (18.2%) of 11 monoallelic expressors showed high expression, which suggests that the increased expression of p73 might be caused by the transcriptional activation of a silent allele in carcinomas. Single-strand conformational polymorphism analysis of the entire coding region of p73 revealed no mutation, whereas 12 (26.7%) of the same set showed p53 alterations. No relationship between expression of p73 and p53 mutation or expression of p21Waf1 or MDM2 was identified. Taken together, our data argue that p73 does not play a role as a tumor suppressor in bladder carcinogenesis and suggest that the activation of a silent allele may contribute to the progression of bladder tumors.

Alleles↗

PubMed1999

Overexpression of cyclin D1 is rare in human prostate carcinoma.

BACKGROUND: Overexpression of cyclin D1 has been documented in a number of human cancers. Increased expression of cyclin D1 can contribute to cellular transformation and abnormal proliferation. METHODS: Quantitative RT-PCR and/or Western blot analysis were used to determine the level of cyclin D1 expression in 96 human prostate tumors, 15 benign prostate hyperplasias, 4 prostate cancer cell lines, and 3 xenografts. RESULTS: Our results demonstrate that 4.2% of the prostate tumors examined overexpressed cyclin D1 transcripts. In the cell lines, expression was normal, with the exception that reduced levels of cyclin D1 transcript and protein were observed in the DU145 cell line, as expected from cells with mutant RB. Normal levels of cyclin D1 were found in all xenograft tumors and BPH specimens examined. CONCLUSIONS: These data show that overexpression of cyclin D1 occurs rarely in human prostate tumors. However, when overexpression of cyclin D1 does occur, it may identify a subset of tumors with a different molecular biology.

Blotting, Southern↗

PubMed1998

Very frequent p53 mutations in metastatic prostate carcinoma and in matched primary tumors.

BACKGROUND: The frequency of mutant p53 in bone marrow metastases of patients with carcinoma of the prostate (CaP) and in matched sets of metastatic and primary lesions from the same patients was investigated. The data were examined in relation to prior treatment with androgen ablation (AA) therapy and were compared with the frequency of mutant p53 reported for primary CaP. METHODS: Seventeen patients with M1b (bone metastasis: TNM Stage IV) CaP had either unilateral or bilateral bone marrow biopsies taken for these studies. Specimens were divided and the outer one-third examined histologically to confirm the presence of CaP cells. Immunohistochemical (IHC) staining for accumulated p53 protein was performed by an antibody cocktail technique. RNA was extracted from the remaining portion of the biopsy, and p53 transcripts were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) and screened for base sequence changes in the exon 4-11 region using nonisotopic single-strand conformation polymorphism (SSCP) analysis and direct DNA sequencing. RESULTS: Ten of 17 metastases (59%) demonstrated accumulation of p53. Six of 7 (86%) of the p53 IHC positive bone marrow samples contained RT-PCR-SSCP abnormalities, as did 2 of 3 IHC negative samples. Overall, 12 of 17 metastases (71%) contained mutant p53. Four of 7 biopsies (57%) retrieved prior to AA contained mutant p53, whereas 8 of 10 post-AA biopsies (80%) contained mutant p53. One patient showed identical SSCP abnormalities in right and left iliac crest metastases after therapy, and in this patient DNA sequencing demonstrated a missense mutation at codon 126 (TAC --> GGC, Tyr --> Gly). Archival primary cancers from seven patients were retrieved. All seven were IHC positive for p53 accumulation. CONCLUSIONS: p53 mutations are associated with increased metastatic potential of CaP. Abnormalities are found at approximately twice the frequency in metastases than in unselected samples of primary CaP, whereas in matched specimens there is a high rate of consonance. Mutant p53 may contribute to systemic therapy resistance, due to increased association with post-AA CaP specimens.

Bone Marrow↗

PubMed1998

Heterogeneous HBV mutants coexist in Korean hepatitis B patients.

Although many hepatitis B virus (HBV) mutants have been found in all open reading frames since the precore defective mutant was initially reported, systematic investigations of diverse HBV mutant populations in hepatitis B patients have not been performed. Therefore, we examined whether heterogeneous mutant populations simultaneously exist in Korean hepatitis B patients. In order to detect hepatitis B virus mutants, we amplified a conserved core region and a surface antigen region of HBV DNA by PCR from sera of 27 Korean chronic hepatitis B patients, and then performed single strand conformational polymorphism analysis followed by DNA sequencing analysis. The results showed that heterogeneous HBV mutants in both regions were present in a single as well as in various hepatitis B patients. Sequence analysis revealed a defective interfering particle with missense mutation in the core region. We also found that two subtypes of adr and adw coexisted in a single patient. In addition, a point mutation causing a stop codon in the surface antigen region was observed. We are further analyzing the clinical implications of HBV mutants to identify their roles in the pathogenesis of chronic hepatic disorders induced by HBV.

Adult↗

PubMed1998

Increased RB1 abnormalities in human primary prostate cancer following combined androgen blockade.

BACKGROUND: The RB1 proliferation control pathway is a critical determinant of cell cycle progression. Abnormalities of RB1 are found in a variety of cancers, and the association with human prostate cancer (CaP) was examined here. METHODS: RNA expression levels of RB1 in CaPs were examined by RT-PCR. RNA integrity was assessed by evaluating expression of an endogenous gene standard. RESULTS: Abnormally low RB1 mRNA expression was found in 12/33 (36%) of CaPs from patients who had received combined androgen blockade (CAB) treatment. In contrast, 6/48 (13%) untreated CaPs showed abnormally low expression. This difference was statistically significant (P = 0.015). In the samples from untreated patients, a higher frequency of abnormal RB1 was found in specimens with a higher Gleason grade (P = 0.038). In addition, one untreated stage C, grade 9 specimen was found to express RB1 transcripts lacking exon 22, as determined by sequencing of DNA from the truncated transcripts. CONCLUSIONS: These findings suggest that abnormalities of RB1 may contribute to hormone-withdrawal-related survival of CaP cells.

Androgen Antagonists↗

PubMed1998

Mutational abrogation of the PTEN/MMAC1 gene in gastrointestinal polyps in patients with Cowden disease.

BACKGROUND & AIMS: To understand the molecular etiology of Cowden disease-associated gastrointestinal polyps, we analyzed the mutational status of PTEN/MMAC1, a recently identified Cowden disease gene located at 10q23, in gastric hamartomas, colonic adenoma, and juvenile polyps of 3 patients with Cowden disease. METHODS: Messenger RNA expression, gene deletion, and sequence alteration of PTEN/MMAC1 were evaluated by quantitative polymerease chain reaction (PCR), PCR-single-strand conformation polymorphism, and sequencing analysis. RESULTS: Germline missense mutation at codon 289 (AAA to GAA, Lys to Glu) and deletion of the wild-type allele were detected in the polyps of 2 patients with Cowden disease in the same family. Germline allelic deletion and transcriptional silencing of the remaining allele, probably caused by abnormal methylation, were also observed in a gastric hamartoma of 1 patient. CONCLUSIONS: The germline mutation and alteration of the remaining allele observed in this study strongly support that PTEN/MMAC1 functions as a tumor suppressor in Cowden disease. This study is the first to show that the mutational abrogation of PTEN/MMAC1 plays a causal role in the genesis of gastrointestinal polyps in Cowden disease, providing molecular genetic evidence that colonic adenoma, juvenile polyp, and gastric hamartoma could be included in the manifestations of Cowden disease.

Adolescent↗

PubMed1998

Detection of t(11;22)(q24;q12) translocation of Ewing's sarcoma in paraffin embedded tissue by nested reverse transcription-polymerase chain reaction.

Ewing's sarcoma is a poorly characterized malignant tumor with a relatively uniform histologic appearance, made up of densely packed small cells with round to oval nuclei, without distinct cell borders and without any structural differentiation. Often the diagnosis has to be made by exclusion. Recently, it has been made possible to identify characteristic chromosomal rearrangements associated with certain solid tumors. More than 85% of Ewing's sarcoma and peripheral neuroectodermal tumor present a specific t(11;22)(q24;q12) balanced translocation, resulting in the production of a novel chimerical EWS/FLI-1 message. Using oligonucleotide primers derived from EWS and FLI-1 complementary DNAs, we were able to use reverse transcription-polymerase chain reaction (RT-PCR) as a diagnostic tool. The described nested RT-PCR method as another supportive diagnostic method enables pathologists to differentiate small blue cell tumors not only to make correct diagnosis but also to investigate retrospective archival tumor samples, using formalin fixed paraffin embedded tissue as a source of RNA.

Chromosomes, Human, Pair 11↗