Clinical relevance of Fas expression in oesophageal squamous cell carcinoma

AIMS

To determine the extent of Fas expression in oesophageal squamous cell carcinomas (ESCCs) from Chinese patients and to correlate Fas expression with clinicopathological prognostic parameters.

METHODS

Clinicopathological data were collected from 58 patients with ESCC who underwent oesophagectomy and had no prior radiotherapy or chemotherapy. Immunostaining was performed on the primary tumours. Expression of Fas was correlated with patients' demographics, tumour characteristics and stage, R category of surgery, and patients' survival.

RESULTS

The actuarial survival rates of all patients at two and five years after surgery were 48% and 14%, respectively. Fas expression was detected in 89.7% of ESCCs. Higher Fas expression recorded on a four point scale correlated with better tumour differentiation (p < 0.01), but not with other patient or tumour variables. Importantly, higher Fas expression was associated with better survival (p = 0.0317).

CONCLUSIONS

These findings suggest that Fas activated apoptosis is important in the pathogenesis of ESCC. This molecular pathway may be a potential therapeutic target for ESCC.

ICA-based procedures for removing ballistocardiogram artifacts from EEG data acquired in the MRI scanner

Electroencephalogram (EEG) data acquired in the MRI scanner contains significant artifacts, one of the most prominent of which is ballistocardiogram (BCG) artifact. BCG artifacts are generated by movement of EEG electrodes inside the magnetic field due to pulsatile changes in blood flow tied to the cardiac cycle. Independent Component Analysis (ICA) is a statistical algorithm that is useful for removing artifacts that are linearly and independently mixed with signals of interest. Here, we demonstrate and validate the usefulness of ICA in removing BCG artifacts from EEG data acquired in the MRI scanner. In accordance with our hypothesis that BCG artifacts are physiologically independent from EEG, it was found that ICA consistently resulted in five to six independent components representing the BCG artifact. Following removal of these components, a significant reduction in spectral power at frequencies associated with the BCG artifact was observed. We also show that our ICA-based procedures perform significantly better than noise-cancellation methods that rely on estimation and subtraction of averaged artifact waveforms from the recorded EEG. Additionally, the proposed ICA-based method has the advantage that it is useful in situations where ECG reference signals are corrupted or not available.

Transformation of diffuse large B-cell lymphoma into pre-B acute lymphoblastic leukemia: clinicopathologic features and clonal relationship

A patient with fibrosing alveolitis developed a diffuse large B-cell (DLBC) lymphoma that expressed CD20 and CD30. After an initial response, the lymphoma relapsed and was salvaged with further chemotherapy. After another remission of 3 years, a pre-B-cell acute lymphoblastic leukemia (ALL), which expressed CD10, CD19, CD22, CD79a, CD34 and terminal deoxyribonucleotidyl transferase, developed and led to death. Molecular analysis of the immunoglobulin heavy-chain gene showed that the initial lymphoma and its relapse were clonally related. At leukemic relapse, 2 clones related to the initial and relapsed lymphoma clones were present. DLBC lymphomas arise from post-follicle center B cells, whereas ALL arises from pregerminal B cells. Therefore, a direct transformation of DLBC lymphoma to ALL appears unlikely. The overall features suggest instead separate lymphoma and leukemic evolution from a common mutated B-cell precursor rather than transformation of DLBC lymphoma to ALL.

Clinicohistological disparity in leprosy

A healthy elderly man presented with localized isolated erythematous tender, anesthetic, oval plaque with little scaling near the medial angle of right eye, of 3 years' duration without any obvious nerve thickening, treated irregularly with WHO MDT for 3 months, clinically simulating BT leprosy with downgrading reversal reaction. Histology showed a BL granuloma with plenty of solid staining AFB within the foamy macrophages. Lepromin test was very weakly positive. The case is discussed in the light of clinicohistological disparity in leprosy cases with review of relevant literatures. A stress is laid on the importance of newer MDT in such cases to prevent drug-resistance, relapse and recurrence.

E-cadherin expression is commonly downregulated by CpG island hypermethylation in esophageal carcinoma cells

E-cadherin, a cell adhesion molecule, is regarded as an invasion-suppressor molecule and a prognostic marker in many types of human cancers. Downregulation of E-cadherin is common in esophageal carcinoma and is associated with an increase in invasive and metastatic potential. To study the mechanisms responsible for inactivation of this gene in esophageal squamous cell carcinoma (ESCC), we investigated the methylation status around the 5' promoter region of E-cadherin gene of six ESCC cell lines by methylation-specific polymerase chain reaction, and compared it with E-cadherin protein and mRNA expression. We also studied the methylation status of 20 ESCC clinical specimens. Methylation was noted in four of the six cell lines (one fully methylated and three partially methylated). The completely methylated cell line lacked E-cadherin protein expression and mRNA transcription. E-cadherin expression and transcription were reduced in a partially methylated cell line but preserved in the other partially methylated cell lines. Treatment of E-cadherin-negative carcinoma cells with the demethylating agent, 5-aza-2'-deoxycytidine, induced re-expression of the gene. A high frequency of methylation (16/20, 80%) was also noted in the 20 ESCC clinical samples. Our results indicate that 5' CpG island methylation is common in esophageal carcinoma and may play an important role in downregulation of E-cadherin.

Profiling of differentially expressed cancer-related genes in esophageal squamous cell carcinoma (ESCC) using human cancer cDNA arrays: overexpression of oncogene MET correlates with tumor differentiation in ESCC

PURPOSE

To examine the global gene expression of cancer-related genes in esophageal squamous cell carcinoma (ESCC) through the use of Atlas Human Cancer Array membranes printed with 588 well-characterized human genes involved in cancer and tumor biology.

EXPERIMENTAL DESIGN

Two human ESCC cell lines (HKESC-1 and HKESC-2) and one morphologically normal esophageal epithelium tissue specimen from the patient of which the HKESC-2 was derived were screened in parallel using cDNA expression arrays. The array results were additionally validated using semiquantitative PCR. The overexpression of oncogene MET was studied more extensively for its protein expression by immunohistochemistry in the two ESCC cell lines and their corresponding primary tissues and 61 primary ESCC resected specimens. Sixteen of these 61 ESCC cases also had available the corresponding morphologically normal esophageal epithelium tissues and were also analyzed for MET expression. The clinicopathological features associated with overexpression of the MET gene were also correlated.

RESULTS

The results of cDNA arrays showed that 13 cancer-related genes were up-regulated > or =2-fold (CDC25B, cyclin D1, PCNA, MET, Jagged 2, Integrin alpha3, Integrin alpha6, Integrin beta4, Caveolin-2, Caveolin-1, MMP13, MMP14, and BIGH3) and 5 genes were down-regulated > or =2-fold (CK4, Bad, IGFBP2, CSPCP, and IL-1RA) in both ESCC cell lines at the mRNA level. Semiquantitative RT-PCR analysis of 9 of these differentially expressed genes, including the MET gene, gave results consistent with cDNA array findings. The immunostaining results of the expression of MET gene showed that MET was overexpressed in both ESCC cell lines and their corresponding primary tumors at the protein level, validating the cDNA arrays findings. The results of the clinical specimens showed that the MET gene was overexpressed in ESCC compared with normal esophageal epithelium in 56 of 61 cases (92%). Moreover, the overexpression of MET protein was more often seen in well/moderately differentiated than in poorly differentiated ESCC.

CONCLUSIONS

Multiple cancer-related genes are differentially expressed in ESCC, the oncogene MET is overexpressed in ESCC compared with normal esophageal epithelium, and its protein overexpression correlates with tumor differentiation in ESCC.

Identification of differentially expressed genes in esophageal squamous cell carcinoma (ESCC) by cDNA expression array: overexpression of Fra-1, Neogenin, Id-1, and CDC25B genes in ESCC

PURPOSE

This study aims to identify differentially expressed genes in esophageal squamous cell carcinoma (ESCC) through the use of a membrane-based cDNA array.

EXPERIMENTAL DESIGN

Two newly established human ESCC cell lines (HKESC-1 and HKESC-2) and one corresponding to a morphologically normal, esophageal epithelium tissue specimen, prospectively collected from the HKESC-2-related patient, were screened in parallel using a cDNA expression array containing gene-specific fragments for 588 human genes spotted onto nylon membranes.

RESULTS

The results of cDNA expression array showed that 53 genes were up-regulated 2-fold or higher and 8 genes were down-regulated 2-fold or higher in both ESCC cell lines at the mRNA level. Semiquantitative RT-PCR analysis of a subset of these differentially expressed genes gave results consistent with cDNA array findings. Four of the differentially expressed genes that belong to the categories of oncogenes/tumor suppressor genes (Fra-1 and Neogenin) and cell cycle-related genes (Id-1 and CDC25B) were studied more extensively for their protein expression by immunohistochemistry. The two ESCC cell lines and their corresponding primary tissues, 61 primary ESCC resected specimens and 16 matching, morphologically normal, esophageal epithelium tissues were analyzed. The immunostaining results showed that Fra-1, Neogenin, Id-1, and CDC25B were overexpressed in both ESCC cell lines and their corresponding primary tumors at the protein level, validating the microarray findings. The results of the clinical specimens showed that the Fra-1 gene was overexpressed in ESCC compared with normal esophageal epithelium in 53 of 61 cases (87%), Neogenin in 57 of 61 cases (93%), Id-1 in 57 of 61 cases (93%), and CDC25B in 48 of 61 cases (79%). Furthermore, the expression of Fra-1, Neogenin, and Id-1 in ESCC correlated with tumor differentiation.

CONCLUSIONS

Overall, this study demonstrates that multiple genes are differentially expressed in ESCC and provides the first evidence that oncogenes Fra-1 and Neogenin and cell cycle-related genes Id-1 and CDC25B are overexpressed in ESCC.

Expression of HLA class I, beta(2)-microglobulin, TAP1 and IL-10 in Epstein-Barr virus-associated nasal NK/T-cell lymphoma: Implications for tumor immune escape mechanism

Several mechanisms of immune escape might be in operation in Epstein-Barr virus (EBV)-associated nasal NK/T-cell lymphoma. We have previously shown the downregulation of the immunogenic EBV nuclear antigens by alternative promoter usage and the preferential selection of the deletion genotype of latent membrane protein 1 in nasal lymphoma. To understand further the strategies used for immune escape by this tumor, we examined by immunohistochemistry HLA class I expression in 15 cases using frozen sections, along with beta(2)-microglobulin and transporter associated with antigen processing 1 (TAP1) expression in 39 cases using paraffin sections. All nasal NK/T-cell lymphomas showed positive staining for HLA class I, beta(2)-microglobulin and TAP1 on most tumor cells, except for two cases (5%) in which most of the tumor cells lacked beta(2)-microglobulin staining. We next immunostained for interleukin-10 on frozen sections in 13 cases, all of which showed strong expression by most tumor cells. Transcription of human interleukin-10 but not EBV BCRF1 (viral interleukin-10) was identified by reverse transcriptase-polymerase chain reaction in these nasal NK/T-cell lymphomas. Overall, our data suggest that global downregulation of HLA class I or TAP1 rarely accounts for the ability of nasal NK/T-cell lymphoma to evade immunosurveillance and that other immune escape mechanisms may be operating in nasal NK/T-cell lymphoma, such as production of interleukin-10 to suppress the local immune response.

BCL10 somatic mutations rarely occur in gastric lymphoma: detection of high frequency of polymorphisms in BCL10 coding region

The BCL10 gene, recently isolated due to its involvement in the t(1;14)(p22;q32) of mucosa-associated lymphoid tissue B cell non-Hodgkin lymphoma (MALToma), was shown to have frequent somatic mutations and short deletions within the coding region in MALToma and a variety of other lymphomas and solid tumors. These observations have been recently questioned. In this study, we examined BCL10 gene mutations by direct sequencing of the entire coding region of the BCL10 gene, amplified from paired normal and tumor genomic DNAs, as well as tumor cDNAs, in 23 cases of primary gastric B cell non-Hodgkin lymphomas, comprising of 6 cases of MALToma and 17 cases of diffuse large cell (DLC) lymphoma. Heterozygosity due to three types of known polymorphisms in codon 5 (17.3%), codon 8 (21.7%), and codon 213 (8.6%) were observed in both normal germline DNA and tumor DNAs and tumor cDNAs in individual cases. In one case (4.3%) G/C heterozygosity in codon 8 in normal germline DNA was reduced to homozygosity (LOH) in tumor DNA and cDNA. Mutations inactivating BCL10 gene product function were not found in any of these cases. Moreover, post-transcriptional alterations were not indicated by abnormalities in BCL10 mRNA sequence in tumor cDNAs in these gastric lymphoma cases. Our results show that somatic mutations in the BCL10 gene rarely occur in gastric lymphoma and indicate that this gene is unlikely to be of pathogenetic significance in the majority of gastric lymphomas.

Detection of genetic alterations in esophageal squamous cell carcinomas and adjacent normal epithelia by comparative DNA fingerprinting using inter-simple sequence repeat PCR

In this study, we screened 19 esophageal squamous cell carcinomas (ESCCs) for the detection of genetic alterations using inter-simple sequence repeat PCR, a DNA fingerprinting approach. Three simple repetitive unanchored primers representing tri- and tetranucleotide repeats [(GTG)(5), (GACA)(4), and (GATA)(4)] were used, and evidence of gains and losses of chromosomal sequences were detected in all tumors (19 of 19 cases) for at least one of the primers. In 13 of these cases, apparently normal marginal epithelia adjacent to the tumors were also collected and examined. Eight of the 13 (62%) patients showed matching somatic mutations in the marginal epithelia adjacent to the tumors. Five of these 8 (63%) marginal epithelial samples were histologically normal, two were dysplastic, and one had extremely rare tumor cells. In 3 of these 13 (23%) cases, the profile bands were also seen to quantitatively increase in intensity, progressing from normal epithelia to marginal epithelia to tumors. Ten profile bands showing gains and one profile band showing loss in tumors compared with the corresponding normal epithelia were cloned, and their origins were determined by sequencing. The DNA sequence of one of the profile bands showing gain in the tumor could be matched to an expressed sequence tag sequence that has been mapped to the 7q22 region, a genomic amplification novel to ESCC. The sequence of the other profile band showing gain in the tumor could be matched to a nonexonic sequence of chromosome 20, whereas the sequences of the remaining profile bands could not be matched with any known sequences after comparison with the genomic sequence data in the European Molecular Biology Laboratory and GenBank databases. The bona fide nature of the gains or losses of 11 profile bands in the original cases was confirmed by direct genomic PCR amplification. The frequencies of these specific gene alterations in tumors were then analyzed in a total of 60 ESCCs, which included 41 additional cases of ESCC. Significantly, 26 of 60 (43%) tumors showed the DNA amplification for the expressed sequence tag sequence of chromosome 7, whereas the frequency of other individual gene alterations ranged from 7% to 15%. It is concluded that the inter-simple sequence repeat PCR strategy is adequate for the detection of somatic mutations in tumors, most of which are quantitative alterations in anonymous genomic sequences. This approach is also suitable for detection of somatic mutations preceding the onset of morphologically detectable neoplasia in ESCC.

[Detection of Immunoglobulin light chain restriction of mucosa-associated lymphoid tissue type gastric lymphoma using mRNA in situ hybridization]

OBJECTIVE

To evaluate the usefulness of in situ hybridization for Immunoglobulin kappa and lambda light chain mRNA to detect light chain restriction in the diagnosis of primary gastric lymphoma (PGL) of mucosa-associated lymphoid tissue (MALT) type.

METHODS

Twenty-seven cases of PGL of MALT type and 5 cases of gastritis were analyzed using in situ hybridization with fluorescent isothiocyanate (FITC)-labeled oligonucleotide probes for kappa and lambda light chain mRNA. The kappa:lambda ratios of tumor cells, lymphocytes and plasma cells were analyzed to detect light chain restriction and clonal plasma cells.

RESULTS

Light chain restriction was found in 10 of 27 (37%) cases of PGL cases (in 5/9 low grade and 5/18 in high grade). Clonal plasma cells were detected in low grade but not in high-grade cases. No light chain restriction was found in gastritis specimens, the adjacent tissue of tumors or the distant stomach mucosa in lymphoma cases.

CONCLUSIONS

The detection of clonality using mRNA in situ hybridization could be a helpful diagnostic tool for gastric lymphoma. The presence of clonal plasma cells can be a marker of the early lesion of low-grade PGL.

Establishment and characterization of a new xenograft-derived human esophageal squamous cell carcinoma cell line SLMT-1 of Chinese origin

A new human esophageal cancer cell line, named SLMT-1, was established from a nude-mouse xenograft of a well-differentiated esophageal squamous cell carcinoma (ESCC) of the lower esophagus from a male Hong Kong Chinese patient. SLMT-1, passaged over 34 times and with a doubling time of 31 hours, has the microscopic features of epithelial cells with adherent growth as a monolayer. The general biologic properties of SLMT-1 cells were characterized by (1) a positive test of tumorigenicity obtained by injecting cells subcutaneously into athymic nude mice and observing their development into well-differentiated squamous cell carcinoma; (2) immunohistochemical staining using antibodies (AE1/AE3, CAM5.2 and MAK 6) which show the presence of cytokeratin intermediate filaments; and (3) electron microscopy demonstrating the morphologic features of epithelial cells with the presence of desmosomes. The cytogenetic abnormalities found in both the primary culture and SLMT-1 included der(1;14)(q10;q10), add(1)(p1?), +1, +2, del(3)(q11), +6, +7, i(8)(q10), +8, +10, +11, -13, -15, +16, +17, -18, -19, -Y and marker chromosomes. Additional changes observed in the 34th passage included gains as well as losses of both numerical and structural abnormalities. Comparative genomic hybridization (CGH) indicated copy number gains on chromosomal regions 3q32-qter, 5p, 8p12-p11.2, 11q13-q22 and 13q22-qter, and loss of the Y. The gains of 8p12-p11.2 in SLMT-1 cells are novel to ESCC. Based on its distinct and common characteristics, the SLMT-1 cell line serves as a useful tool for studying the molecular and genetic basis of the pathogenesis of ESCC.

Establishment and characterization of HKESC-1, a new cancer cell line from human esophageal squamous cell carcinoma

The establishment of an esophageal cancer cell line can facilitate the search for molecular mechanisms involved in esophageal carcinogenesis. A new human cancer cell line, HKESC-1, was established from a primary moderately-differentiated squamous cell carcinoma of the esophagus from a 47-year-old Hong Kong Chinese man. The pathological characteristics (morphology, immunohistochemical, and electron microscopic studies), the tumorigenecity in nude mice, the cytogenetic features, the DNA ploidy, and telomerase activity of the cell line were investigated. The HKESC-1 cells have been maintained continuously in vitro for more than 16 months and passaged over 96 times. HKESC-1 cells grow as a monolayer, with a doubling time of 46 hours. The HKESC-1 cells are of a squamous epithelial origin, as shown by their immunopositivity with the anti-cytokeratin antibodies and ultrastructural demonstration of tonofilaments and desmosomes. The HKESC-1 cells possess characteristics of malignancy because they are highly tumorigenic in nude mice and have strong telomerase activity. The HKESC-1 cells had an aneuploid DNA content, as demonstrated by flow cytometric analysis. Cytogenetic analysis revealed hyperdiploidy of greater than 50 in 80% of analyzable metaphases. Chromosome gains and losses were common, and loss of the Y chromosome was a consistent numerical aberration. Additionally, many structural chromosomal abnormalities were encountered, with frequent breakpoints at 1p32, 7p22, 7q34, and 20q13. This newly established cell line serves as a useful model for studying the molecular pathogenesis, and testing new therapeutic reagents for esophageal squamous cell carcinoma.

Coinfection of multiple strains of Epstein-Barr virus in immunocompetent normal individuals: reassessment of the viral carrier state

This study reassesses the occurrence of Epstein-Barr virus (EBV) diversity and coinfection versus dominance of a single viral strain within immunocompetent normal carriers. Polymerase chain reaction analysis of several different polymorphic loci of the EBV genome was performed on collections of peripheral blood mononuclear cells and multiple lymphoid and epithelial tissues of the same individuals. Autopsy specimens from 15 individuals who died of causes unrelated to EBV infection served as normal viral carriers. Unexpectedly, coinfection of multiple distinct strains of EBV of the same type (usually type 1) and less frequently of both types 1 and 2 was found to be very high within individual viral carriers. These data indicate that coinfection with multiple EBV strains is much more prevalent in normal carriers than previously appreciated, which in turn has direct implications on EBV persistence, host-viral interaction and pathogenesis.

Incidence and pathology of primary brain lymphoma in Hong Kong Chinese patients

Primary brain lymphoma (PBL) is an uncommon extranodal lymphoma. Its incidence is rapidly increasing in both immunocompromised and immunocompetent patients in Western countries. Eighteen cases of PBL were identified during a 16-year period among HIV negative patients in Queen Mary Hospital, Hong Kong. One case of post-transplantation lymphoproliferative disease (PTLD) was positive for Epstein Barr virus (EBV) encoded RNA (EBER) by in situ hybridization. All the remaining 17 immunocompetent cases were classified as diffuse large B-cell lymphoma, except for one case of Burkitt's lymphoma. EBER expression was negative in all 13 cases tested. Immunostaining for bcl-2 and bcl-6 was positive in 8/11 and 6/11 cases tested, with heterogeneous combination of expression and intensity. The incidence rate of PBL in immunocompetent patients was stable at 1.03 per million per year. The incidence of PBL in post transplantation (0.16%) and HIV related setting (0.29%) is also low in Chinese. PBL in Chinese patients is almost uniformly represented by EBV negative, diffuse large B-cell lymphoma, confined to the brain. However, the molecular pathogenesis may be heterogeneous.

Identification and characterization of BCL6 translocation partner genes in primary gastric high-grade B-cell lymphoma: heat shock protein 89 alpha is a novel fusion partner gene of BCL6

Primary gastric high-grade B-cell lymphoma (HGBL) is a special type of non-Hodgkin's lymphoma. So far, the genetic features of this tumor have not been well characterized. Recently, a high incidence of BCL6 rearrangements has been detected in HGBL. However, no previous cytogenetic studies have found translocations involving the BCL6 locus (3q27) in HGBL, and the genetic basis underlying the BCL6 rearrangements in this tumor remains unclear. We therefore characterized the partner genes of BCL6 in five primary gastric HGBLs with a rearranged BCL6 gene by analyzing BCL6 transcripts using the 5' RACE (rapid amplification of cDNA end) strategy. BCL6 translocation partner genes were identified at the 5' end of the chimeric transcripts in all five cases, including the immunoglobulin heavy-chain (IGH) gene in three cases and the immunoglobulin lambda-light-chain gene and the heat shock protein 89 alpha (HSP89A) gene in the other two cases. The chimeric transcripts in all cases contained the intact BCL6 exon 2, but lacked exon 1, which was replaced by sequences from the partner genes, suggesting that BCL6 expression was under the control of regulatory sequences of the partner genes. These results, for the first time, indicate that immunoglobulin genes, especially IGH, are the most common BCL6 translocation partner genes in primary gastric HGBL and that HSP89A is a novel partner of BCL6. Because immunoglobulin genes are also the most frequent partners of BCL6 in nodal diffuse large B-cell lymphoma (DLBCL), these data suggest that primary gastric HGBL shares a common genetic basis with nodal DLBCL. Genes Chromosomes Cancer 27:69-75, 2000.

A study to determine the incidence and prevalence of newly discovered human immunodeficiency virus infection during the prenatal care period

OBJECTIVES

This study asked the following questions: 1) Does HIV testing in pregnancy identify women who previously were not known to be HIV positive? 2) When in pregnancy are women identified as HIV infected? 3) Does HIV seroconversion occur during the prenatal care period?

METHODS

Medical records of 97 women from two primarily indigent care hospitals in Houston, TX who were found to be HIV positive at delivery were reviewed to determine if they had tested positive during the prenatal care period. Demographics and time of gestation of the prenatal testing also were recorded. The outcome measures were: 1) number of women found positive during prenatal care; 2) week of gestation at discovery of HIV positivity; and 3) number of women seroconverting between the initiation of prenatal care and delivery.

RESULTS

Thirty women were known to be HIV positive prior to pregnancy. Fifty-six women were found to be positive during prenatal care and the seropositivity of 44 was discovered before the 34th week of pregnancy. Ten women were found to be positive at their first prenatal visit, which occurred after the 34th week. Date of testing was unknown for two women. Eleven women who received no prenatal care were found to be HIV positive at delivery. There were no seroconversions while women were under prenatal care.

CONCLUSIONS

HIV testing at delivery did not find any HIV-positive women who had tested negative during prenatal care. Testing is very important for women who do not receive prenatal care. Making certain that high-risk women get into prenatal care also is very important.

Mutational analysis of the PTEN/MMAC1 gene in primary oesophageal squamous cell carcinomas

AIM

To investigate whether PTEN/MMAC1 mutations play a role in the carcinogenesis of oesophageal squamous cell carcinoma.

METHODS

A panel of 33 primary oesophageal squamous cell carcinoma tumour samples and 20 corresponding morphologically normal tissues was examined for mutations in all nine exons of the PTEN/MMAC1 gene by means of polymerase chain reaction single strand conformational polymorphism analysis (PCR-SSCP) and direct DNA sequencing methods.

RESULTS

Only one of 33 oesophageal squamous cell carcinomas showed an aberrant SSCP band. Further sequencing analysis of this sample revealed an 802 -29 T-->C substitution in intron 7. PTEN/MMAC1 mutations were not found in the mutational "hot spot" in exon 5, even after direct sequencing of six oesophageal squamous cell carcinoma samples and three normal tissues. However, a deletion of one nucleotide T at position 492 +8 in intron 5 was seen in all samples.

CONCLUSION

These results suggest that PTEN/MMAC1 mutations do not play a major role in the carcinogenesis of oesophageal squamous cell carcinoma.