Antoine Italiano

HMGA2 is the partner of MDM2 in well-differentiated and dedifferentiated liposarcomas whereas CDK4 belongs to a distinct inconsistent amplicon

Data concerning the fine structure of the 12q13‐15 amplicon which contains MDM2 and CDK4 in well‐differentiated and dedifferentiated liposarcomas (WDLPS/DDLPS) are scarce. We investigated a series of 38 WDLPS/DDLPS using fluorescence in situ hybridization analysis with 17 probes encompassing the 12q13‐15 region. In addition, using quantitative RT‐PCR we studied the expression of MDM2, CDK4, DDIT3 (CHOP/GADD153), DYRK2, HMGA2, TSPAN31 and YEATS4 (GAS41) in 11 cases. We showed that CDK4 (12q14.1) belonged to a distinct amplicon than MDM2 (12q15). There was no continuity in the amplified sequences between MDM2 and CDK4. Moreover, while MDM2 was amplified and overexpressed in all cases, CDK4 was not amplified or overexpressed in 13% of cases. The centromeric border of the CDK4 amplicon was located immediately downstream the 5′ end of DDIT3, a gene known for being involved in myxoid liposarcoma translocations. DDIT3 was amplified in 3 cases and overexpressed in 9 cases. The overexpression of DDIT3 was correlated to the CDK4 amplification and not to its own amplification status. This suggested that the CDK4 amplicon, as well as the overexpression of DDIT3, might be generated by the disruption of a fragile region in 5′ DDIT3. HMGA2 was always amplified and rearranged indicating that it plays a central role in WDLPS/DDLPS. HMGA2 rearrangement frequently resulted in a loss of the 3′ end region that is a binding site for let‐7. We also found a frequent amplification and overexpression of YEATS4, an oncogene that inactivates P53, suggesting that YEATS4 might play an important role together with MDM2 in WDLPS/DDLPS oncogenesis.

KRAS and BRAF Mutational Status in Primary Colorectal Tumors and Related Metastatic Sites: Biological and Clinical Implications

BackgroundKRAS and BRAF mutations in primary colorectal tumors (PT) are predictive of nonresponse to anti–epidermal growth factor receptor (EGFR) antibodies in patients with metastatic colorectal cancer (mCRC). The question of primary resistance to anti-EGFR treatment as a result of the presence of KRAS or BRAF mutations only in metastases has been raised but not resolved.MethodsWe analyzed the mutational status of KRAS and BRAF in 64 new patients with mCRC and performed a systematic review of published data from 285 patients.ResultsA total of 285 and 95 matched PT/metastases were available for the analysis of the KRAS and the BRAF status, respectively. An identical mutational pattern of KRAS in PT and the matching metastases were reported in all the cases but 14 (5%). In six cases (2%), KRAS was mutated in the PT and wild type in the metastatic site, whereas in eight cases (3%), KRAS was wild type in the PT and mutated in the metastatic site. An identical mutational pattern of BRAF in PT and the matching metastases was reported in all but two cases (3%). In one case (1.5%), BRAF was mutated in the PT and wild type in the metastatic site, whereas in one case (1.5%), BRAF was wild type in the PT and mutated in the metastatic site.ConclusionsThe acquisition by metastases of a KRAS or a BRAF mutation that was not present in the PT is a rare event, occurring in 5% of cases of mCRC. This is not a frequent mechanism of primary resistance to anti-EGFR treatments in mCRC.

Cetuximab shows activity in colorectal cancer patients with tumors for which FISH analysis does not detect an increase in EGFR gene copy number.

BackgroundEGFR (epidermal growth factor receptor) gene gain assessed by FISH (fluorescence in situ hybridization) has been shown to be predictive of response to EGFR-targeted therapies in patients with non–small cell lung cancer. The aim or our study was to relate the EGFR gene copy number to therapeutic results in patients with metastatic colorectal cancer (CRC) treated with a cetuximab-containing regimen.MethodsForty-seven patients with metastatic CRC treated with a cetuximab-containing regimen between August 2004 and September 2006 were included in our study. EGFR status was assessed by immunohistochemistry (IHC) and by FISH on fixed paraffin-embedded sections of tumor specimens.ResultsBy IHC (n = 47), 39 patients (83%) had EGFR-positive tumors. EGFR gene copy gain was detected in 8 (19.5%) of 41 tumors. Neither EGFR expression assessed by IHC nor EGFR gene copy gain assessed by FISH were statistically significantly correlated with objective response rate, disease control rate, progression-free survival, and overall survival. Of the 33 patients whose tumors were FISH negative, 8 patients (24.2%) had a partial response, and 10 (30.3%) had stable disease.ConclusionsEGFR FISH analysis does not seem to be a sufficiently robust test for selecting candidate CRC patients for cetuximab therapy.

Gains and complex rearrangements of the 12q13-15 chromosomal region in ordinary lipomas: The “missing link” between lipomas and liposarcomas?

Well‐differentiated liposarcomas (WDLPS) classically contain high‐level amplification of 12q14‐15 sequences, including the MDM2 and CDK4 genes, while lipomas are characterized by simple structural chromosome aberrations often involving HMGA2 at 12q15. Previous studies have shown that low‐level gain of the 12q14‐15 region, such as trisomy 12 and 12q15‐24 duplication, might be sufficient for the development of minimal atypia and formation of WDLPS. Moreover, because some features, such as overexpression of HMGA2, are shared by both lipomas and WDLPS, it has been hypothesized that lipomas and WDLPS may form a genetic and morphological continuum. We report here the results of molecular cytogenetic analysis of 8 lipomas that had unusual chromosomal features resulting in gains of 12q14‐15. While 3 cases had simple numerical rearrangements (trisomy 12) or structural rearrangements (unbalanced translocations with 12q gains), 5 cases were particularly intriguing because of peculiar features such as giant chromosomes, supernumerary chromosomes or neocentromeres that usually are the hallmark of WDLPS. Gain of 12q14‐15 sequences including extra copies of MDM2 and CDK4 were detected by fluorescence in situ hybridization analysis in all analyzed cases but no expression of MDM2 and CDK4 was observed suggesting that these genomic imbalances had no functional consequence. We observed rearrangements of HMGA2 in 5 out 8 cases. Altogether, our results indicate that moderate gains of 12q are not always associated with a malignant phenotype, and that some intermediary forms exist between classical lipomas and classical WDLPS. Some of these intermediary forms may correspond to a genomic premalignant condition while some may have no malignant potential.

Variability of origin for the neocentromeric sequences in analphoid supernumerary marker chromosomes of well-differentiated liposarcomas

Well-differentiated liposarcomas (WDLPS) and dedifferentiated liposarcomas are cytogenetically characterized by the presence of supernumerary ring or giant chromosomes containing amplified material from the 12q14-15 region. These chromosomes contain neocentromeres, which are able to bind the kinetochore proteins and to ensure a stable mitotic transmission although they do not show detectable alpha-satellite sequences. WDLPS is the sole solid tumor for which the presence of a neocentromere is a consistent and specific feature. By immunostaining with anti-centromere antibodies in combination with FISH analysis (immunoFISH) in four cases of WDLPS, we have shown that sequences from the region 12q14-21 region were not located at the neocentromere site. In addition, we have microdissected the neocentromeric region from a giant supernumerary chromosome in the 94T778 WDLPS cell line. By using immunoFISH and positional cloning we have shown that the neocentromere of this cell line originated from a region at 4p16.1, rich in AT sequences and in long interspersed nucleotide element (LINE)1, that was co-amplified with 12q14-15. We have observed that this 4p sequence was not involved in the neocentromere of the supernumerary giant chromosome present in the 93T449 WDLPS cell line derived from a metachronous recurrence of the same primary WDLPS than 94T778. Altogether, these results indicate that the neocentromeres in WDLPS originate from amplified chromosomal regions other than 12q14-15 and do not involve a specific and recurrent DNA sequence. These sequences might be activated for centromeric function by epigenetic mechanisms.

Naevus lipomatosus superficialis: a case report with a 2p24 deletion

1 Al-Hajj M, Wicha MS, Benito-Hernandez A et al. Prospective identification of tumorigenic breast cancer cells. Proc Natl Acad Sci USA 2003; 100:3983–8. 2 Singh SK, Clarke ID, Terasaki M et al. Identification of a cancer stem cell in human brain tumors. Cancer Res 2003; 63:5821–8. 3 Hemmati HD, Nakano I, Lazareff JA et al. Cancerous stem cells can arise from pediatric brain tumors. Proc Natl Acad Sci USA 2003; 100:15178–83. 4 Fang D, Nguyen TK, Leishear K et al. A tumorigenic subpopulation with stem cell properties in melanomas. Cancer Res 2005; 65:9328– 37. 5 Lyle S, Christoficou-Solomidou M, Liu Y et al. The C8/144B monoclonal antibody recognizes cytokeratin 15 and defines the location of human hair follicle stem cells. J Cell Sci 1998; 111:3179–88. 6 Liu Y, Lyle S, Yang Z, Cotsarelis G. Keratin 15 promoter targets putative epithelial stem cells in the hair follicle bulge. J Invest Dermatol 2003; 121:963–8. 7 Morris RJ, Liu Y, Marles L et al. Capturing and profiling adult hair follicle stem cells. Nat Biotechnol 2004; 22:411–17. 8 Schwartz RA, Torre DP. The Muir–Torre syndrome: a 25-year retrospect. J Am Acad Dermatol 1995; 33:90–104.

Monosomy 7 and absence of 12q amplification in two cases of spindle cell liposarcomas.

Spindle cell liposarcoma (SCL) is a rare malignant adipose tissue tumor presently regarded as a variant of well-differentiated liposarcoma (WDLPS). While WDLPS is cytogenetically characterized by the presence of supernumerary ring or giant chromosomes containing MDM2 amplification, data concerning the genomic alterations of SCL are scarce. Here, we describe the molecular cytogenetic characterization of two SCL cases. In these two cases, we did not identify supernumerary ring or giant chromosomes containing 12q amplification or any other chromosome 12 rearrangement. Instead, we observed a partial or complete monosomy 7 as the sole anomaly or among a few additional simple numeric and structural abnormalities. Monosomy 7 is not usual in adipose tissue tumors. It has been described in myelodysplastic syndromes and acute myeloid or lymphoblastic leukemias, as well as in several benign or malignant solid tumors. Our data suggest that the loss of material from chromosome 7 might play a crucial role in the pathogenesis of some SCL probably through the inactivation of tumor suppressor genes located on chromosome 7. On the basis of cytogenetic and molecular findings, some SCL may constitute an independent entity rather than being regarded as variants of WDLPS.

Cutaneous myxolipoma with apocrine glandular differentiation: description of a new clinicopathological variant with chromosome 6p21 rearrangement

N McAndrew S Birdsall R L Attanoos Department of Histopathology, Cardiff and Vale NHS Trust, University Hospital of Wales, Heath Park, Cardiff, Department of Respiratory Medicine, Wrexham Maelor Hospital, Croesnewydd Road, Wrexham, Department of Haematology, Cardiff and Vale NHS Trust, University Hospital of Wales, Heath Park, Cardiff, Department of Histopathology, Cardiff and Vale NHS Trust, Llandough Hospital, South Glamorgan, UK