Abnormal expression of MDM-2 in breast carcinomas

MDM-2 is a cellular oncoprotein that binds to the p53 protein and abrogates its growth-suppressing function. At least seven MDM-2 mRNAs and five proteins (p90, p85, p76, p74, and p57) have been reported in tissue culture. MDM-2 gene amplification occurs in human sarcomas and high-grade gliomas. MDM-2 overexpression without gene amplification has been reported in leukemias and lymphomas. Here we report MDM-2 mRNA overexpression in 24 (73%) out of 33 cases of human breast carcinoma as compared with normal breast tissue. The MDM-2 overexpression was seen in the absence of MDM-2 gene amplification. MDM-2 protein expression was studied by western blot analysis in 21 of these cases of carcinoma. We found complete concordance between MDM-2 mRNA overexpression and MDM-2 protein levels. MDM-2 proteins were overexpressed in 15 of 21 breast carcinoma tissue samples but not in normal breast tissue controls. Ten of these fifteen cases overexpressed MDM-2 p57 protein, two cases overexpressed both p57 and p90, and three cases overexpressed only p90. MDM-2 overexpression was confirmed by immunohistochemistry. p53 overexpression was also studied by immunohistochemistry; 69% of breast carcinomas that overexpressed the MDM-2 mRNA had detectable nuclear p53 protein. These findings demonstrate that MDM-2 oncoprotein expression is altered in primary human breast carcinomas at both mRNA and protein levels. In addition, our results suggest that MDM-2 p57 protein represents the main MDM-2 protein altered in breast carcinomas.     

Multi-platform profiling of over 2000 sarcomas: Identification of biomarkers and novel therapeutic targets

Background: Drug development in sarcoma has been hampered by the rarity and heterogeneity of the disease and lack of predictive biomarkers to therapies. We assessed protein expression and gene alterations in a large number of bone and soft tissue sarcomas in order to categorize the molecular alterations, identify predictive biomarkers and discover new therapeutic targets. Methods: Data from sarcoma specimens profiled for protein expression, gene amplification/translocation and DNA sequencing was reviewed. Results: 2539 sarcoma specimens of 22 subtypes were included. TOPO2A was the most overexpressed protein at 52.8%. There was overexpression or loss of other sarcoma relevant proteins such as SPARC, PTEN and MGMT. Approximately 50% of the sarcomas expressed PD-L1 by IHC and presented with PD-1+ TILs, notably the LMS, chondrosarcomas, liposarcomas and UPS. Gene amplification/rearrangement of ALK, cMYC, HER2, PIK3CA, TOPO2A and cMET was relatively uncommon. EGFR gene amplification occurred at a rate of 16.9%. DNA sequencing of 47 genes identified mutations in 47% of the samples. The most commonly mutated genes were TP53 (26.3%) and BRCA2 (17.6%). Overexpression of TOPO2A was associated with TP53 mutation (P = 0.0001). Conclusion: This data provides the landscape of alterations in sarcoma. Future clinical trials are needed to validate these targets.     

MDM2 gene amplification in bone and soft-tissue tumors: Association with tumor progression in differentiated adipose-tissue tumors

We have studied 107 bone and soft-tissue sarcomas and 8 lipomas for amplification of the MDM2 gene. This gene was amplified in 3 out of 67 osteosarcomas, 3 out of 20 malignant fibrous histiocytomas, 4 out of 20 liposarcomas, and 4 out of 8 lipomas. The amplification was associated with overexpression of mRNA. In osteosarcomas, contrary to previous findings, all amplifications were observed in primary lesions. In liposarcomas, the amplification was seen exclusively in well-differentiated tumors with high frequency (4/5) but not in other subtypes (0/15). In addition, MDM2 amplification was also frequently found in deep-seated intra- or intermuscular lipomas (4/5). Hence, it is suggested that MDM2 amplification plays a significant role in the development of differentiated adipose-tissue tumors. Three well-differentiated liposarcomas with MDM2 amplification coexisted with high-grade dedifferentiated sarcomas, in which MDM2 amplification was also observed. Interestingly, in 2 of these cases, the grades of amplification correlated with the histological grades, indicating an important role of MDM2 overexpression in tumor progression. © 1995 Wiley-Liss, Inc.     

High expression of neuropeptide Y1 receptors in ewing sarcoma tumors

PURPOSE: Peptide receptors are frequently overexpressed in human tumors, allowing receptor-targeted scintigraphic imaging and therapy with radiolabeled peptide analogues. Neuropeptide Y (NPY) receptors are new candidates for these applications, based on their high expression in specific cancers. Because NPY receptors are expressed in selected sarcoma cell lines and because novel treatment options are needed for sarcomas, this study assessed the NPY receptor in primary human sarcomas. EXPERIMENTAL DESIGN: Tumor tissues of 88 cases, including Ewing sarcoma family of tumors (ESFT), synovial sarcomas, osteosarcomas, chondrosarcomas, liposarcomas, angiosarcomas, rhabdomyosarcomas, leiomyosarcomas, and desmoid tumors, were investigated for NPY receptor protein with in vitro receptor autoradiography using (125)I-labeled NPY receptor ligands and for NPY receptor mRNA expression with in situ hybridization. RESULTS: ESFT expressed the NPY receptor subtype Y1 on tumor cells in remarkably high incidence (84%) and density (mean, 5,314 dpm/mg tissue). Likewise, synovial sarcomas expressed Y1 on tumor cells in high density (mean, 7,497 dpm/mg; incidence, 40%). The remaining tumors expressed NPY receptor subtypes Y1 or Y2 at lower levels. Moreover, many of the sarcomas showed Y1 expression on intratumoral blood vessels. In situ hybridization for Y1 mRNA confirmed the autoradiography results. CONCLUSIONS: NPY receptors are novel molecular markers for human sarcomas. Y1 may inhibit growth of specific sarcomas, as previously shown in an in vivo mouse model of human ESFT. The high Y1 expression on tumor cells of ESFT and synovial sarcomas and on blood vessels in many other sarcomas represents an attractive basis for an in vivo tumor targeting.     

Apport des analyses moléculaires à la classification anatomopathologique des sarcomes

Conventional histology and immunohistochemistry remain the basic tools for the diagnosis and classification of sarcomas. However, molecular biology can enrich the pathologists analysis: the identification of a specific molecular abnormality can confirm diagnosis, rule out a differential diagnosis, and sometimes provide prognostic information. About 15% of sarcomas bear a specific translocation, such as rearrangements of SS18 (SYT) [synovial sarcoma], DDIT3 (CHOP) [myxoid liposarcoma], FUS (TLS) [low-grade fibromyxoid sarcoma, myxoid liposarcoma], FOXO1 (FHKR) [alveolar rhabdomyosarcoma], PDGFB (dermatofibrosarcoma protuberans), and ALK (inflammatory myofibroblastic tumor). Rearrangements of the EWSR1 gene are less specific as found in many sarcomas (Ewing sarcoma, desmoplastic round cell tumor, clear cell sarcoma, myxoid liposarcoma, andmyoepithelioma). The search for an amplification of MDM2 gene is a sensitive and specific tool for the diagnosis of atypical lipomatous tumors/welldifferentiated liposarcomas and dedifferentiated liposarcomas (ALT/WDL). The same molecular abnormality can be observed in several tumor types, emphasizing the importance of integrating the results of any molecular study within clinical, morphological, and immunohistochemical context: ASPSCR1 (ASPL)-TFE3 translocation can be observed in alveolar soft tissue sarcoma but also in juvenile renal carcinomas, ETV6 (TEL)-NTRK3 (TRKC) translocation in infantile fibrosarcoma and secretory breast carcinoma, ALK rearrangements in inflammatory myofibroblastic tumors, anaplastic lymphomas, and lung adenocarcinomas. In some cases immunochemistry can highlight the consequence of a molecular abnormality: MDM2 overexpression in ALT/WDL, loss of INI1 expression in rhabdoid tumors and epithelioid sarcoma, and overexpression of ALK in inflammatory myofibroblastic tumors.     

MDM2基因在骨生肉瘤及脂肪肉瘤中的表达及临床意义

目的 研究MDM2基因与国人骨肉瘤和脂肪肉瘤的关系从而了解MDM2基因在肉瘤发生中的作用及其临床意义。方法 用免疫组化方法研究了31例骨肉瘤,2例骨旁骨肉瘤,6例软骨肉瘤,14例脂肪肉瘤MDM2的表达。结果 31例骨肉瘤中MDM2阳性表达者18例,为58.6％,骨旁骨肉瘤2例皆为阳性表达,6例软骨肉瘤中2例阳性表达;14例脂肪肉瘤中8例阳性表达,为57.1％。结论 MDM2癌基因异常与肉瘤的发生关系密切,但对肉瘤的恶性级别和预后的影响仍不明确,有待讲一步研究。     

Analysis of p53 mutational events and MDM2 amplification in canine soft-tissue sarcomas.

Canine cancer is of major significance in terms of animal health and welfare and soft tissue sarcomas are an important group of tumours accounting for approximately 15% of all canine tumours presented. Abnormal p53 protein expression and gene mutations have been identified in a number of different canine tumour types. However, mdm2 gene amplification has only been investigated in a limited number of canine osteosarcomas. In this present study a series of canine soft-tissue sarcomas (STS) were examined for p53 mutations and/or mdm2 amplification. For p53 mutational studies polymerase chain reaction and direct DNA sequencing was used. Gene mutations were identified in 6 of 30 (20%) primary tumour cases including MPNST (n=3) leiomysarcoma (n=1), heamangiosarcoma (n=1) and sarcoma (n=1). mdm2 gene amplification was assessed by Southern Blot. Although there was no evidence for major gene rearrangements, gene amplification was detected in 4 of 35 (11.4 %) primary tumours including MPNST (n=2), rhabdomyosarcoma (n=2). A total of 33 cases were examined for both p53 mutations and mdm2 amplification. Seven of the tumours were positive for p53 mutations, while five were positive for mdm2 amplification. With the exception of one case, a reciprocal relationship between the presence of a p53 mutation and mdm2 gene amplification was demonstrated.     

Molecular biology of soft-tissue sarcomas

Sarcomas represent a heterogeneous group of tumors with a complex and poorly reproducible classification. However, in the last ten years, several specific genetic alterations have been described allowing a molecular classification with: 1) sarcomas with a specific translocation which can be used as a diagnostic marker. These translocations can be demonstrated by RT-PCR or by FISH with commercially available break apart probes ; 2) sarcomas with simple genomic profile showing amplification of a few genes. Well differentiated liposarcomas, dedifferentiated liposarcomas and intimal sarcomas show a simple genomic profile characterised by MDM2 and CDK4 amplifications associated with amplification of other genes in dedifferentiated liposarcomas ; 3) sarcomas with activating mutations: about 90% of GIST show activating mutation of a receptor tyrosine kinase gene, either KIT or PDGFRA. The most frequent mutation involves exon 11 of KIT followed by exon 9 of KIT and exon 18 of PDGFRA. Demonstration of these mutations is useful for the diagnosis of CD117 negative GIST, for predicting response to imatinib and to explain secondary resistance to imatinib ; 4) sarcomas with inactivating mutations: malignant rhabdoid tumors show biallelic inactivation of INI1 gene with a lost of INI1 expression which can be demonstrated by immunohistochemistry ; 5) other sarcomas usually show a complex genomic profile characterised by numerous gains and losses of genes with a frequent loss of RB1 and alterations of P53. Leiomyosarcomas, pleomorphic rhabdomyosarcomas, pleomorphic liposarcomas, myxofibrosarcomas, poorly differentiated sarcomas (so-called MFH and fibrosarcomas) belong to this category and show no specific molecular abnormality.     

From cytogenetics to cytogenomics of adipose tissue tumors: 2. Malignant adipose tissue tumors

Malignant adipose tissue tumors, also called liposarcomas, are the most common sarcoma of adult life. They may be hard to distinguish from benign adipose tissue tumors as well as from other types of sarcomas. Well-differentiated liposarcomas and myxoid liposarcomas are the two histological subtypes that have been best characterized at the genetic level. The defining genetic features of well-differentiated liposarcoma cells are supernumerary circular ("ring") and giant linear rod chromosomes. These rings and giant chromosomes contain amplification of the 12q14-15 region, including the MDM2 gene, associated with coamplification of various other chromosomal regions. In addition, they most often lack alpha-satellite centromeric sequences. The detection of MDM2 amplification is a valuable tool for the differential diagnosis between well-differentiated liposarcomas and lipomas. Dedifferentiated liposarcomas usually present with patterns of MDM2 amplification similar to those observed in well-differentiated liposarcomas. In addition, recent CGH-array studies suggest that co-amplification of MDM2 with the 6q23-25 region might be a specific feature. Myxoid and round-cell liposarcomas are characterized by a translocation t(12;16)(q13;p11) that fuses the DDIT3 and FUS genes. A rare variant translocation t(12;22) that fuses DDIT3 with EWS has also been described. The genetics of pleomorphic liposarcoma is still obscure. Pleomorphic liposarcomas show complex karyotypes with many numerical and structural chromosomal aberrations. To date, no specific molecular abnormality has been identified.     

Low grade amplification of MDM2 gene in a subset of human breast cancers without p53 alterations

MDM2 protein is thought to bind to p53 tumor suppressor protein leading to inhibition of p53-mediated transactivation. Amplification of the MDM2 gene has been frequently observed in human sarcoma, and relevant overexpression of the MDM2 protein is assumed to contribute to tumorigenesis through inactivation of the p53 function. In order to determine whether MDM2 amplification plays a role in the development of human breast cancer without genetic alteration of p53, we analyzed, MDM2 gene amplification by quantitative hybridization and genetic alteration of p53, in 32 primary tumors and 26 metastatic lymph nodes. Low grade amplification of the MDM2 gene (2-6 fold) was observed in four cases, none of which showed even subtle genetic alterations of p53 or loss of alleles on 17p. Moreover, in three of the four cases with MDM2 gene amplification, the level of gene amplification in the metastatic lymph nodes was slightly higher than that in the primary tumors. These results, taken together with previous findings, suggest that a subset of breast cancers without genetic alteration of p53 may also arise by inactivation of the p53 function through interaction with the overexpressed MDM2 protein induced by gene amplification.     

Amplification of cyclin D1 and MDM-2 in oesophageal carcinoma.

AIMS: This study investigated amplification of the cyclin D1 and MDM-2 genes, and overexpression of the cyclin D1 gene product, in oesophageal carcinoma. METHODS: Paired tumour and normal DNA samples from 26 oesophageal adenocarcinomas and 19 squamous cell carcinomas were analysed by Southern blotting with specific DNA probes for cyclin D1 and MDM-2, and for a control gene (alpha-lactalbumin). The cyclin D1 and MDM-2 gene copy numbers were calculated for each tumour. Expression of the cyclin D1 gene was assessed by immunohistochemical analysis of its protein product. RESULTS: Cyclin D1 gene amplification (by a factor of between two and six) was identified in seven tumours (16%). MDM-2 gene amplification (by a factor of between two and 11) was identified in 10 tumours (22%). Overexpression of cyclin D1 protein was identified in eight tumours and was significantly associated with gene amplification (P=0.04; Fisher's exact test), and with early T stage (P=0.01; Fisher's exact test). CONCLUSIONS: Cyclin D1 and MDM-2 amplification and cyclin D1 overexpression occur, although infrequently, in the development of oesophageal carcinoma. Cyclin D1 overexpression may influence tumour behaviour, causing the disease to present at an earlier T stage. The mechanism for this effect is unclear, and warrants further investigation.     

Current soft-tissue sarcoma classifications

In order to analyse the impact of modern sarcoma classification criteria, pathological material from 281 extremity soft-tissue sarcomas (STS) was reviewed. The cases were originally diagnosed between 1972 and 1994, and the most frequent diagnoses then were malignant fibrous histiocytoma (MFH) (26%), liposarcoma (21%), fibrosarcoma (11%), and leiomyosarcoma (10%). After reclassification, the proportions had changed significantly, with the largest group now being leiomyosarcomas (20%), liposarcomas (17%), synovial sarcomas (14%), and sarcomas "not otherwise specified" (NOS) (11%). The original diagnosis was changed in 57% of the cases; in particular, the number of fibrosarcomas was reduced from 32 to 6, and MFHs from 72 to 2, with 22 renamed as myxofibrosarcomas; 20 (7%) were found not to be sarcomas. The main reasons for these results are the recent advances in immunohistochemistry (IHC) together with changes in nomenclature. The findings have obvious implications, in particular for retrospective research.     

SAS amplification in soft tissue sarcomas.

Gene amplification is an important mechanism of increased gene expression in a number of human solid tumors. We have recently identified and cloned sequences from a novel DNA amplification unit in malignant fibrous histiocytoma. The amplified sequences are derived from chromosome 12q13-14 and encode a gene designated SAS (sarcoma amplified sequence). In the present study, a series of soft tissue sarcomas was studied to characterize further the phenomenon of SAS amplification. Seven of 22 (32%) malignant fibrous histiocytomas and three liposarcomas contained SAS amplification. Strikingly, all of the tumors with SAS amplification occurred in central sites (i.e., in the abdominal or inguinal regions) rather than in the extremities (i.e., in the arms of legs). These observations demonstrate that SAS amplification occurs with a significant frequency in mesenchymal tumors and is particularly associated with abdominal disease.