Biomedical subjects

S C Jhanwar

Publications and source records attributed to S C Jhanwar.

At least 37 records · Page 2Linked to original sources

PubMed1999

Comparative genomic hybridization and loss of heterozygosity analyses identify a common region of deletion at 15q11.1-15 in human malignant mesothelioma.

Comparative genomic hybridization analysis was performed to identify chromosomal imbalances in 24 human malignant mesothelioma (MM) cell lines derived from untreated primary tumors. Chromosomal losses accounted for the majority of genomic imbalances. The most frequent underrepresented segments were 22q (58%) and 15q1.1-21 (54%); other recurrent sites of chromosomal loss included 1p12-22 (42%), 13q12-14 (42%), 14q24-qter (42%), 6q25-qter (38%), and 9p21 (38%). The most commonly overrepresented segment was 5p (54%). DNA sequence amplification at 3p12-13 was observed in two cases. Whereas some of the regions of copy number decreases (i.e., segments in 1p, 6q, 9p, and 22q) have previously been shown to be common sites of karyotypic and allelic loss in MM, our comparative genomic hybridization analyses identified a new recurrent site of chromosomal loss within 15q in this malignancy. To more precisely map the region of 15q deletion, loss of heterozygosity analyses were performed with a panel of polymorphic microsatellite markers distributed along 15q, which defined a minimal region of chromosomal loss at 15q11.1-15. The identification of frequent losses of a discrete segment in 15q suggests that this region harbors a putative tumor suppressor gene whose loss/inactivation may contribute to the pathogenesis of many MMs.

Chromosomes, Human, Pair 15↗

PubMed1999

Cytogenetic analysis of 363 consecutively ascertained diffuse large B-cell lymphomas.

Cytogenetic analysis was performed on 363 biopsy specimens with histologically confirmed diffuse large B-cell lymphoma (DLBCL), consecutively ascertained at the Memorial Sloan-Kettering Cancer Center, New York, between 1984 and 1994. Among 248 samples successfully karyotyped, clonal chromosomal abnormalities were noted in 215 (87%). The salient cytogenetic features of DLBCL from this analysis comprised the following. Breakpoints clustered, in decreasing frequency, at 10 recurring sites: 14q32, 18q21, 1q21, 3q27, 1p36, 8q24, 3p21, 6q21, 1p22, and 22q11. Of these, deletion breaks affecting bands 3p2 and 1p22 and translocation breaks affecting bands 14q32, 3q27, and 1q2 were frequent and distinctive for this subset of lymphomas. Translocations affecting band 14q32 were noted in 110 cases (51%) of which 42 (20%) had t(14;18)(q32;q21), 21 (10%) had t(8;14)(q24;q32) or t(8;22)(q24;q11), 14 (6.5%) had t(3;14)(q27;q32) or t(3;22)(q27;q11), and 33 (15%) had other rearrangements of 14q32. Among 144 new translocations detected in the entire group, the breakpoints in 19 were recurrent and clustered at three sites: 1q21, 3q27, and 14q32. Regions of common cytogenetic deletions were identified at 11 sites, 1p36, 1p33-34, 1p31, 1q32, 3p25-26, 3p21, 3q21, 6q15, 6q21, 6q23-24, and 7q32, suggesting possible loss of candidate tumor suppressor genes associated with DLBCL development. Of these, only those at 6q21, 6q23, and 7q32 have previously been described in lymphoid neoplasms. The group of DLBCL with translocations affecting band 14q32 showed a significantly different pattern of additional cytogenetic changes compared to the group lacking such translocation. This new comprehensive cytogenetic characterization provides the basis for investigations aimed at identifying molecular mechanisms as well as the clinical impact of cytogenetic changes in DLBCL.

Chromosome Aberrations↗

PubMed1999

Frequent mutations of NF2 and allelic loss from chromosome band 22q12 in malignant mesothelioma: evidence for a two-hit mechanism of NF2 inactivation.

We previously reported NF2 mutations in malignant mesothelioma (MM) cell lines and corresponding primary tumors. We have now generated polyclonal antibodies that specifically recognize the C-terminus of the NF2 protein. Western blot analysis was performed on 25 MM cell lines, 14 of which showed no NF2 expression. Single-strand conformation polymorphism and DNA sequence analyses revealed NF2 mutations in each of these 14 cell lines. To explore the mechanism of inactivation of NF2, loss of heterozygosity analysis was performed with two microsatellite markers located in the vicinity of the NF2 locus in chromosome band 22q12. Eighteen of the 25 cell lines (72%) showed losses at one or both loci tested. All cases exhibiting mutation and/or aberrant expression of NF2 showed allelic losses, suggesting that inactivation of NF2 in MM occurs via a two-hit mechanism.

Blotting, Western↗

PubMed1998

Multicolor spectral karyotyping identifies new recurring breakpoints and translocations in multiple myeloma.

Karyotypic information on multiple myeloma (MM) is less extensive than that on other myeloid or lymphoid malignancies due to low mitotic activity of plasma cells. An add(14)(q32) marker chromosome has been reported to be the most frequent recurring abnormality in clonally abnormal cases; in approximately one third of the latter cases, this marker has been identified as a der(14)t(11;14)(q13;q32) chromosome. To map chromosomal breakpoints, characterize the add(14)(q32) marker chromosomes, and to identify other recurring translocations in MM, we used spectral karyotyping (SKY) to analyze a panel of nine bone marrow (BM) biopsy samples from eight patients and 10 tumor cell lines derived from MM patients. SKY involves hybridization of 24 fluorescently labeled chromosome painting probes to metaphase spreads in such a manner that simultaneous visualization of each of the chromosomes in a different color is accomplished. By this method, it was possible to define all chromosomal rearrangements and identify all of the clonal marker chromosomes in tumor cells. By detailed mapping of breakpoints of rearrangement, it was also possible to identify several novel recurring sites of breakage that map to the chromosomal bands 3q27, 17q24-25, and 20q11. The partner chromosomes in translocations that generated the add (14)(q32) marker chromosomes were identified in all cases in which they were detected by G-banding (one biopsy and six cell lines). In addition, two new translocations involving band 14q32, ie, t(12;14)(q24;q32) and t(14;20)(q32;q11) have also been identified. These studies demonstrate the power of SKY in resolving the full spectrum of chromosome abnormalities in tumors.

Aged↗

PubMed1998

Chromosomal and gene amplification in diffuse large B-cell lymphoma.

Chromosomal translocations leading to deregulation of specific oncogenes characterize approximately 50% of cases of diffuse large B-cell lymphomas (DLBL). To characterize additional genetic features that may be of value in delineating the clinical characteristics of DLBL, we studied a panel of 96 cases at diagnosis consecutively ascertained at the Memorial Sloan-Kettering Cancer Center (MSKCC) for incidence of gene amplification, a genetic abnormality previously shown to be associated with tumor progression and clinical outcome. A subset of 20 cases was subjected to comparative genomic hybridization (CGH) analysis, which identified nine sites of chromosomal amplification (1q21-23, 2p12-16, 8q24, 9q34, 12q12-14, 13q32, 16p12, 18q21-22, and 22q12). Candidate amplified genes mapped to these sites were selected for further analysis based on their known roles in lymphoid cell and lymphoma development, and/or history of amplification in tumors. Probes for six genes, which fulfilled these criteria, REL (2p12-16), MYC (8q24), BCL2 (18q21), GLI, CDK4, and MDM2 (12q13-14), were used in a quantitative Southern blotting analysis of the 96 DLBL DNAs. Each of these genes was amplified (four or more copies) with incidence ranging from 11% to 23%. This analysis is consistent with our previous finding that REL amplification is associated with extranodal presentation. In addition, BCL2 rearrangement and/or REL, MYC, BCL2, GLI, CDK4, and MDM2 amplification was associated with advanced stage disease. These data show, for the first time, that amplification of chromosomal regions and genes is a frequent phenomenon in DLBL and demonstrates their potential significance in lymphomagenesis.

Chromosome Mapping↗

PubMed1998

Characterization of nonrandom chromosomal gains and losses in multiple myeloma by comparative genomic hybridization.

Clonal chromosomal changes in multiple myeloma (MM) and related disorders are not well defined, mainly due to the low in vivo and in vitro mitotic index of plasma cells. This difficulty can be overcome by using comparative genomic hybridization (CGH), a DNA-based technique that gives information about chromosomal copy number changes in tumors. We have performed CGH on 25 cases of MM, 4 cases of monoclonal gammopathy of uncertain significance, and 1 case of Waldenstrom's macroglobulinemia. G-banding analysis of the same group of patients demonstrated clonal chromosomal changes in only 13 (43%), whereas by CGH, the number of cases with clonal chromosomal gains and losses increased to 21 (70%). The most common recurrent changes detected by CGH were gain of chromosome 19 or 19p and complete or partial deletions of chromosome 13. +19, an anomaly that has so far not been detected as primary or recurrent change by G-banding analysis of these tumors, was noted in 2 cases as a unique change. Other recurrent changes included gains of 9q, 11q, 12q, 15q, 17q, and 22q and losses of 6q and 16q. We have been able to narrow the commonly deleted regions on 6q and 13q to bands 6q21 and 13q14-21. Gain of 11q and deletion of 13q, which have previously been associated with poor outcome, can thus be detected by CGH, allowing the use of this technique for prognostic evaluation of patients, without relying on the success of conventional cytogenetic analysis.

Adult↗

PubMed1998

Deregulation of BCL6 in non-Hodgkin lymphoma by insertion of IGH sequences in complex translocations involving band 3q27.

Chromosomal band 3q27 frequently engages in translocations with a number of sites within the genome, including those containing IG and other genes, during the development of B-cell lymphoma. The BCL6 gene, mapped at 3q27, is deregulated in these translocations and was isolated from a t(3;14)(q27;q32) translocation. It encodes a zinc-finger transcription repressor protein, which is expressed mainly in the germinal center (GC) B cells and plays a key role in GC development and T-cell-dependent immune response. BCL6 deregulation in 3q27 translocations is brought about by substitution of its 5' regulatory sequences by promoters of the rearranging genes. BCL6-rearranging genes studied so far (IGH, IGLL, TTF, BOBI, H4) displayed a broader pattern of expression than BCL6 during B-cell development. This observation has led to the suggestion that continued expression of BCL6 beyond its developmentally regulated point of downregulation under the direction of substituted promoters may keep the GC B cell in a cycling mode and lead to clonal expansion and lymphoma development. However, the rearranging partners of BCL6 in several of the 3q27 translocations have not yet been identified. In a molecular cloning analysis of two such translocations, t(1;3)(q21;q27) and t(3;6)(q27;p25), and an immunoblastic lymphoma cell line, OSI-LY8, we identified a novel mechanism of BCL6 deregulation. This comprised replacement of BCL6 5' regulatory sequences by insertion of IG gene transcriptional regulatory sequences at the translocation junction. These studies demonstrate novel features of instability of 3q27, and of the BCL6 and IGH genes, in B-cell lymphomagenesis.

Base Sequence↗

PubMed1998

Neuroblastoma and treatment-related myelodysplasia/leukemia: the Memorial Sloan-Kettering experience and a literature review.

PURPOSE: To assess treatment-related myelodysplasia/leukemia (t-AML) in neuroblastoma patients by a review of the Memorial Sloan-Kettering Cancer Center (MSKCC) data and the literature. PATIENTS AND METHODS: We studied 380 previously untreated and treated MSKCC patients. Low-risk patients received no cytotoxic therapy. High-risk patients received the N4, N5, or N6 regimens. Dosing per cycle and cumulative dosing of leukemogenic agents peaked with N6, which included four cycles of cyclophosphamide 4,200 mg/m2 and doxorubicin 75 mg/m2, plus three cycles of cisplatin 200 mg/m2 and etoposide 600 mg/m2. We reviewed the literature. RESULTS: t-AML occurred in six MSKCC patients, which included three of 53 patients in whom the only chemotherapy consisted of N6, and three patients treated for relapsed or refractory neuroblastoma; no case of leukemia emerged among the 50 low-risk patients. Four cases were found incidentally in routine follow-up bone marrow tests. The 36-month cumulative incidence of t-AML in the N6 cohort was 7% (95% confidence interval, 0 to 15). Published data parallel the MSKCC experience in that t-AML after neuroblastoma was once rare but has become less so since the mid-1980s, when the intensified use of topoisomerase-II inhibitors and alkylators first gained wide acceptance and produced better response rates and longer survival. CONCLUSION: Neuroblastoma itself is not associated with a host susceptibility to leukemia. However, current neuroblastoma treatment programs that use high-dose cyclophosphamide, cisplatin, and topoisomerase-II inhibitors may entail a considerable risk for t-AML. The incidence of t-AML in neuroblastoma patients may be underestimated because treatment and clinical factors can mask its presence. Efforts to devise effective but less leukemogenic treatment for neuroblastoma or to truncate leukemogenic therapy, eg, by exploiting molecular techniques for the early identification of complete remission, are warranted.

Antineoplastic Agents↗

PubMed1998

EWS-FLI1 fusion transcript structure is an independent determinant of prognosis in Ewing's sarcoma.

PURPOSE: More than 90% of Ewing's sarcomas (ES) contain a fusion of the EWS and FLI1 genes, due to the t(11;22)(q24;q12) translocation. At the molecular level, the EWS-FLI1 rearrangements show great diversity. Specifically, many different combinations of exons from EWS and FLI1 encode in-frame fusion transcripts and result in differences in the length and composition of the chimeric protein, which functions as an oncogenic aberrant transcription factor. In the most common fusion type (type 1), EWS exon 7 is linked in frame with exon 6 of FLI1. As the fundamental pathogenetic lesion in ES, the molecular heterogeneity of these fusion transcripts may have functional and clinical significance. PATIENTS AND METHODS: We performed a clinical and pathologic analysis of 112 patients with ES in which EWS-FLI1 fusion transcripts were identified by reverse-transcriptase polymerase chain reaction (RT-PCR). Adequate treatment and follow-up data were available in 99 patients treated with curative intent. Median follow-up in these 99 patients was 26 months (range, 1 to 140 months). Univariate and multivariate survival analyses were performed that included other prognostic factors, such as age, tumor location, size, and stage. RESULTS: Among the 99 patients suitable for survival analysis, the tumors in 64 patients contained the type 1 fusion and in 35 patients contained less common fusion types. Stage at presentation was localized in 74 patients and metastatic in 25. Metastases (relative risk [RR] = 2.6; P = .008), and type 1 EWS-FLI1 fusion (RR = 0.37; P = .014) were, respectively, independent negative and positive prognostic factors for overall survival by multivariate analysis. Among 74 patients with localized tumors, the type 1 EWS-FLI1 fusion was also a significant positive predictor of overall survival (RR = 0.32; P = .034) by multivariate analysis. CONCLUSION: EWS-FLI1 fusion type appears to be prognostically relevant in ES, independent of tumor site, stage, and size. Further studies are needed to clarify the biologic basis of this phenomenon.

Adolescent↗

PubMed1997

Multiple regions of allelic loss from chromosome arm 6q in malignant mesothelioma.

Our previous cytogenetic studies of malignant mesotheliomas (MMs) revealed losses from 6q15-21 in approximately 40% of cases, suggestive of recurrent loss of function of a putative tumor suppressor gene(s) located in this chromosome region. To more precisely define the critical region of molecular genetic loss within 6q, we have constructed a high-resolution deletion map of this chromosome arm in 46 MMs. We analyzed 32 microsatellite markers to detect loss of heterozygosity in tumor DNAs. Allelic losses from 6q were observed in a high percentage (61%) of cases. Partial deletions of 6q were identified in 11 cases, and these were used to define four nonoverlapping regions of chromosomal loss: a region involving 6q14-21 (approximately 9 cM; 7 of 11 cases with partial deletions), a region within 6q16.3-21 (approximately 8 cM; 9 cases), a region within 6q21-23.2 (approximately 10 cM; 8 cases), and a distal region located at 6q25 (approximately 13 cM; 9 cases). Most cases exhibited losses from more than one of these regions. We conclude from these data that genomic losses involving 6q in MM are more frequent than previously recognized cytogenetically and that the deletions fall into four discrete locations, suggesting the existence of multiple tumor suppressor loci in 6q that may contribute to the pathogenesis of this malignancy.

Alleles↗

PubMed1997

Loss of heterozygosity and homozygous deletion of the tpr locus in human gastric cancer.

BACKGROUND: Despite being one of the world's most common neoplasias, there is little information on the molecular events that lead to gastric cancer. Molecular studies have shown that inactivation of tumor suppressor genes by mutation and/or allelic loss is an important genetic alteration in the multistep process of tumorigenesis. METHODS: In an attempt to identify a putative tumor suppressor gene involved in the carcinogenesis of gastric cancer, we performed Southern blot analysis using the tpr probe for 44 patients with gastric cancer, using tumor tissue and normal tissue from the same specimen. RESULTS: Of the 44 samples, 7 (16%) were informative, heterozygous cases for the tpr probe. Three of the informative cases showed a loss of heterozygosity and 3 cases showed homozygous deletion for the tpr probe (6 of 7; 85%). CONCLUSIONS: These findings suggest that tpr gene plays a role in gastric tumorigenesis, and this may be due to a tumor suppressor effect for the tpr gene.

Blotting, Southern↗

PubMed1997

Molecular analysis of the fusion of EWS to an orphan nuclear receptor gene in extraskeletal myxoid chondrosarcoma.

The pathogenesis of myxoid chondrosarcoma (CS) is poorly understood. A recurrent translocation, t(9;22) (q22;q12), has been recognized in CS, specifically in extraskeletal myxoid CS. Recently, this translocation has been shown to represent a rearrangement of the EWS gene at 22q12 with a novel gene at 9q22 designated CHN (or TEC). Sequence analysis suggests that CHN encodes a novel orphan nuclear receptor with a zinc finger DNA-binding domain. The structure of this gene fusion has been characterized in only a limited number of extraskeletal myxoid CSs and its presence in other types of CS has not been extensively examined. We studied 46 cases of CS (8 extraskeletal myxoid, 4 skeletal myxoid, 4 mesenchymal, and 30 other) for the EWS/CHN gene fusion by reverse transcriptase polymerase chain reaction, Southern blotting, and long-range DNA polymerase chain reaction. The EWS/CHN gene fusion was present in 6 of 8 extraskeletal myxoid CSs and was not detected in any of the remaining cases, including the 4 skeletal myxoid CSs. The negative findings in the latter cases suggest that skeletal myxoid CS is pathogenetically distinct from its extraskeletal counterpart. Notably, 2 cases of extraskeletal myxoid CS showed neither an EWS/CHN fusion transcript nor EWS/CHN genomic fusion nor EWS or CHN genomic rearrangement, suggesting genetic heterogeneity within extraskeletal myxoid CS. Finally, we also provide evidence for alternative splicing of the 3' end of the fusion transcript. Extraskeletal myxoid CS thus represents yet another sarcoma type containing a gene fusion involving EWS.

Adult↗

PubMed1996

Establishment, characterization and drug sensitivity of four new human soft tissue sarcoma cell lines.

Four new cell lines were established from patients with soft tissue sarcomas. Drug sensitivity as well as genotypic characterization, which may be related to drug sensitivity in these cell lines, was determined. Karyotype, H-ras, c-myc and mutant p53 gene expression, Rb, G1- and S-phase cyclins, E2F and major cyclin/CDK inhibitors such as p16 and p21 and p-glycoprotein were analyzed using cytogenetic, Northern blot and immunological methods. Drug sensitivity was determined using growth inhibition tests. These cell lines differed in their morphology and growth rates, forming colonies in soft agar with a cloning efficiency of 4.3-13.4%, and 3 of the 4 cell lines grew in nude mice. Cytogenetic analysis of cell lines revealed highly aneuploid karyotypes. Deletion and/or translocation of chromosome 17 was seen in HS-16, HS-18 and HS-30 cells, and both copies of chromosome 13 were lost or re-arranged in the HS-18 cell line. Mutant p53 protein was present in all 4 cell lines. HS-18 cells showed no expression of the Rb protein and high levels of expression of E2F, cyclin A, cyclin E and CDK2. HS-16 expressed a higher level of cyclin D than the other 3 cell lines. p21WAF1 expression was seen in all cell lines, but p16ink4 was expressed only in HS-30 and HS-42 cell lines. These cell lines were sensitive to taxol and relatively resistant to methotrexate, vinblastine and 5-fluorouracil when compared with the fibrosarcoma cell line HT-1080. These new cell lines should provide a useful model for the study of soft tissue sarcomas and for evaluating new drugs or treatments.

Animals↗

PubMed1996

Loss of heterozygosity analysis defines a critical region in chromosome 1p22 commonly deleted in human malignant mesothelioma.

Previous cytogenetic analysis has revealed frequent losses of chromosome 1p21-22 in human malignant mesothelioma, suggesting that the loss or inactivation of a tumor suppressor gene's) residing at this site may contribute to the tumorigenic conversion of mesothelial cells. To more precisely define the location of the target gene, primary tumor specimens and cell lines from 50 malignant mesotheliomas were examined for loss of heterozygosity using short tandem repeat polymorphism (STRP) markers. Nineteen STRP markers established by the Cooperative Human Linkage Center were selected for the initial screening of the entire short arm of chromosome 1. Thirty-seven cases (74%) showed allelic losses at least at one locus in 1p. Thirty-six of these cases showed losses of 1p21-22, including 23 with partial deletions involving this region. To obtain a higher resolution map of this region, another 13 STRP markers from the Genethon map were used to define the shortest region of overlapping deletions to a 4-cM segment flanked by the loci D1S435 and D1S236. The chromosomal location of the critically deleted region was confirmed to be within 1p22 by karyotypic and fluorescence in situ hybridization analyses.

Chromosomes, Human, Pair 1↗

PubMed1996

Isolation, characterization, and mapping to human chromosome 11q24-25 of a cDNA encoding a highly conserved putative transmembrane protein, TMC.

We report the isolation of a novel human cDNA encoding a putative transmembrane protein, TMC. The predicted protein sequence is highly conserved evolutionarily. The cDNA clone was mapped to human chromosome 11q24-25 by fluorescence in situ hybridization. mRNA expression was observed in all tissues tested with the highest levels in testes and ovary.

Amino Acid Sequence↗

PubMed1995

Hormonal regulation of the p53 tumor suppressor protein in T47D human breast carcinoma cell line.

Under normal culturing conditions, the T47D human breast cancer cell line expresses progesterone receptor constitutively and is responsive to estrogen. Because the tumor suppressor protein p53 plays a central role in determining genetic stability and cell proliferation, we have examined the effects of 17 beta-estradiol, the synthetic progestin R5020, and the antiprogestin RU486 on the levels of this protein in T47D cells. Western blot analysis of cellular extracts, performed with a monoclonal antibody capable of quantitatively supershifting a specific p53-p53 response element complex in a gel mobility shift assay, detected a single immunoreactive band representing p53. When cells were grown for 4-5 days in culture medium containing charcoal-treated fetal calf serum, p53 levels declined to 10% of the level seen in the control (no charcoal treatment) group. Supplementation of culture medium containing charcoal-treated calf serum with 0.1-1 nM 17 beta-estradiol restored p53 to its normal levels. A 4-day treatment of cells with R5020 or RU486 lowered the p53 levels in cells grown in normal culturing conditions to 15 and 30% of control levels, respectively. R5020 and RU486 treatments also caused down-regulation and/or hyperphosphorylation of the progesterone receptor, which correlated with the down-regulation of p53. These observations by estradiol while R5020 down-regulates this protein. Since estradiol is known to promote cell proliferation, the induction of p53 observed in this study leads us to propose that estradiol stimulates p53 to regulate proliferation of T47D cells in culture.

Base Sequence↗

PubMed1995

High frequency of inactivating mutations in the neurofibromatosis type 2 gene (NF2) in primary malignant mesotheliomas.

Malignant mesotheliomas (MMs) are aggressive tumors that develop most frequently in the pleura of patients exposed to asbestos. In contrast to many other cancers, relatively few molecular alterations have been described in MMs. The most frequent numerical cytogenetic abnormality in MMs is loss of chromosome 22. The neurofibromatosis type 2 gene (NF2) is a tumor suppressor gene assigned to chromosome 22q which plays an important role in the development of familial and spontaneous tumors of neuroectodermal origin. Although MMs have a different histogenic derivation, the frequent abnormalities of chromosome 22 warranted an investigation of the NF2 gene in these tumors. Both cDNAs from 15 MM cell lines and genomic DNAs from 7 matched primary tumors were analyzed for mutations within the NF2 coding region. NF2 mutations predicting either interstitial in-frame deletions or truncation of the NF2-encoded protein (merlin) were detected in eight cell lines (53%), six of which were confirmed in primary tumor DNAs. In two samples that showed NF2 gene transcript alterations, no genomic DNA mutations were detected, suggesting that aberrant splicing may constitute an additional mechanism for merlin inactivation. These findings implicate NF2 in the oncogenesis of primary MMs and provide evidence that this gene can be involved in the development of tumors other than nervous system neoplasms characteristic of the NF2 disorder. In addition, unlike NF2-related tumors, MM derives from the mesoderm; malignancies of this origin have not previously been associated with frequent alterations of the NF2 gene.

Base Sequence↗

PubMed1995

MDM2 and CDK4 gene amplification in Ewing's sarcoma.

Amplification of the MDM2 gene, which maps to chromosome band 12q13 and encodes a p53-binding protein, may result in functional inactivation of p53 and has been observed in various bone and soft tissue sarcomas. Published studies have included few cases of Ewing's sarcoma (ES) or peripheral neuroectodermal tumour (PNET), a tumour group in which alterations of the p53 pathway have so far not been extensively studied. We examined two ES cell lines, RD-ES and SK-ES-1, and 30 specimens from 27 patients (24 ES, 6 PNET; 19 primary, 4 local recurrence, 7 metastasis) for MDM2 gene amplification by Southern blot analysis. All 30 clinical specimens had been confirmed to contain sufficient ES/PNET DNA by the demonstration of a rearrangement of the t(11;22)-associated EWS gene using an EWS cDNA probe on the same blots. MDM2 gene amplification was detected in 3 of 30 specimens (10 per cent), including two ES and one PNET, but in neither of the cell lines. The three cases with amplification were morphologically typical primary tumours. Two of the three cases also showed co-amplification of the CDK4 gene, which encodes a cyclin-dependent kinase and also maps to band 12q13. Clinically, all three cases had metastatic disease at diagnosis, compared with only 1 of 15 MDM2-negative cases where the primary tumour was studied. The difference was statistically significant (P = 0.005), suggesting an association of MDM2 amplification with advanced stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗