CASE REPORT

Complex t(5;8) involving the CSPG2 and PTK2B genesin a case of dermatofibrosarcoma protuberanswithout the COL1A1-PDGFB fusion

Laurence Bianchini & Georges Maire & Bernard Guillot &Jean-Marie Joujoux & Philippe Follana &

Marie-Pierre Simon & Jean-Michel Coindre &

Florence Pedeutour

Received: 13 November 2007 /Accepted: 11 January 2008 /Published online: 6 February 2008# Springer-Verlag 2008

Abstract Dermatofibrosarcoma protuberans (DFSP) is arare, dermal neoplasm of intermediate malignancy. It ismade of spindle-shaped tumor cells in a storiform patternpositive for CD34. Cytogenetically, DFSP cells are charac-terized by either supernumerary ring chromosomes com-posed of sequences derived from chromosomes 17 and 22or more rarely of translocations t(17;22). These chromo-somal rearrangements lead to the formation of a specific

chimeric gene fusing COL1A1 to PDGFB. So far, theCOL1A1-PDGFB fusion gene remains the sole fusion geneidentified in DFSP. However, some observations suggestthat genes, other than COL1A1 and PDGFB, might beinvolved in some DFSP cases. We report in this paper aDFSP case presenting as a unique chromosomal abnormal-ity a complex translocation between chromosomes 5 and 8.This is the first report of a DFSP case where the lack ofchromosomes 17 and 22 rearrangement and the absence ofCOL1A1-PDGFB fusion gene have been demonstrated.Using fluorescence in situ hybridization analysis, weshowed that the CSPG2 gene at 5q14.3 and the PTK2Bgene at 8p21.2 were disrupted by this rearrangement.Although rare, the existence of cases of DFSP negativefor the COL1A1-PDGFB fusion has to be taken inconsideration when performing molecular diagnosis for atumor suspected to be a DFSP.

Keywords Dermatofibrosarcoma protuberans .

Translocation t(5;8) .CSPG2 . PTK2B .

Cytogenetics) . FISH

Introduction

Dermatofibrosarcoma protuberans (DFSP) is a rare, slow-growing dermal neoplasm of intermediate malignancy. Theclassic histologic form shows a storiform or cartwheelcellular pattern with a strong immunopositivity for CD34[1, 12]. DFSP cells most often contain supernumerary ringchromosomes composed of sequences derived from chro-mosomes 17 and 22. Balanced or unbalanced t(17;22)translocations are also observed, especially in pediatric

Virchows Arch (2008) 452:689–696DOI 10.1007/s00428-008-0580-2

L. Bianchini :G. Maire : P. Follana : F. PedeutourLaboratoire de Génétique des Tumeurs Solides,Faculté de Médecine, Centre Hospitalier Universitaire de Nice,Université de Nice-Sophia Antipolis,Nice, France

L. Bianchini :G. Maire : P. Follana :M.-P. Simon :F. Pedeutour (*)CNRS UMR 6543, Centre-Antoine-Lacassagne,Nice, Francee-mail: florence.pedeutour@unice.fr

B. GuillotDépartement de Dermatologie, Hôpital Saint-Eloi,Centre Hospitalier Universitaire de Montpellier,Montpellier, France

J.-M. JoujouxDépartement de Pathologie,Centre Hospitalier Universitaire de Nîmes,Nîmes, France

J.-M. CoindreDépartement de Pathologie, Institut Bergonié,Bordeaux, France

Present address:G. MairePrincess Margaret Hospital, Ontario Cancer Institute,Toronto, ON, Canada

cases [34]. These chromosomal rearrangements lead to theformation of a chimeric gene resulting from the fusion ofCOL1A1 (17q21) with PDGFB (22q13) [32].

So far, the COL1A1-PDFGB fusion gene remains theonly fusion gene identified in DFSP and variant tumorssuch as giant cell fibroblastomas and Bednar tumors, and itsdetection is a useful tool for diagnosis. To date, amongmore than 50 DFSP karyotypes that have been published,only 4 cases showed chromosomal anomalies other thanring chromosomes or t(17;22) [20, 34]. These four variantkaryotypes included a t(X;7)(q21.2;q11.2) in a pediatriccase [7], a t(9;22)(q32;q12.2) [35], a t(2;17)(q33;q25) [33],and a complex unbalanced translocation involving chromo-somes 3, 5, 7, and 22 [27]. These observations suggest thatgenes other than COL1A1 or PDGFB might indeed beinvolved in a small subset of DFSP cases.

We report in this paper a case presenting a translocationbetween chromosomes 5 and 8 with no rearrangement ofeither chromosome 17 or chromosome 22 as a uniquekaryotypic abnormality. This is the first report of a DFSPcase with an abnormal karyotype where the absence ofCOL1A1-PDGFB rearrangement has been demonstrated.

Clinical history

A 66-year-old man presented with a brownish plaque andnodule of 2 cm diameter located on the right thighdeveloping for the past 5 years. His medical history wasunremarkable except for a prostate adenoma resected 1 yearbefore. A biopsy was performed. Histologically, the tumorwas composed of spindle fibroblast-like cells arranged infascicles and a few histiocytic cells without any mitosis. Onthe basis of the histologic examination, the tumor wasdiagnosed as a benign histiocytofibroma. The CD34-immunoreactivity was not tested on this first biopsybecause CD34 antibody was not commercially available atthat time. The tumor was surgically removed and recurredas a nodule of 2.5×3 cm in size 10 years later. The biopsyexamination of the recurrent tumor showed that it was madeof spindle-shaped cells organized in a storiform patterncharacteristic of DFSP (Fig. 1a). The cells were positive forCD34 (Fig. 1b) and negative for S100 protein and alphasmooth muscle actin. Based on the histologic findings andthe CD34-immunoreactivity, the tumor was diagnosed as aDFSP. The diagnosis of DFSP was confirmed by apathologist expert in soft tissue tumors (JMC). The initialbiopsy of the primary tumor was also re-examined anddiagnosed as a DFSP as well. The patient underwent acomplete surgical resection of the tumor with surgical marginsof 4.5×3.5 cm followed by reparative skin graft. After a 10-year follow-up, the patient remained free of disease.

Materials and methods

Cytogenetic and fluorescence in situ hybridization analysis

After surgical resection of the recurrent tumor, a freshfragment was prepared for cytogenetic analysis accordingto established procedures [17]. All probes used for thestudy are described in Table 1. Commercially availableprobes were used according to the manufacturer’s recom-mendations. Yeast artificial chromosomes (YAC) were fromthe Centre d’Etudes du Polymorphisme Humain (CEPH,Fondation Jean Dausset, Paris, France) and selected usingthe GDB Human Genome Database (http://www.gdb.org).Bacterial artificial chromosomes clones (BAC) from theRoswell Park Cancer Institute library were selected accord-ing to their location in the University of California SantaCruz genome browser (http://genome.ucsc.edu/) andobtained from the Children’s Hospital Oakland ResearchInstitute (CHORI; http://bacpac.chori.org/). YAC and BACprobes were prepared for fluorescence in situ hybridization(FISH) analysis according to standard procedures [19].Microscopic analysis was performed using an Axioplan IIimaging microscope (Carl Zeiss, Jena, Germany). FISHimages were processed using the ISIS software (Metasys-tems, Altlussheim, Germany).

RNA isolation and RT-PCR analysis

Total RNAs were extracted from paraffin-embedded tumortissue samples [37] and from short-term cultured cells usingthe Trizol method according to the manufacturer’s recom-mendations (Invitrogen, Carlsbad, CA). Detection of theCOL1A1-PDGFB fusion gene was performed on RNA bymultiplex reverse transcriptase polymerase chain reaction(RT-PCR) as described in Maire et al. [20] and Terrier-Lacombe et al. [37].

Results

Rearrangement of chromosomes 5 and 8

Eight RHG-banded metaphases were analyzed. The karyo-type showed a rearrangement involving the chromosome 5long arm at 5q13–14 and the chromosome 8 short arm at8p21 (Fig. 1c). The der(5) was identified by RHG-bandingand FISH analysis using whole chromosome painting(WCP) probes for chromosomes 5 and 8 as resulting froma t(5;8)(q13–14;p21). An additional deletion or inversion ofthe translocated 5q fragment was suspected on the der(8).Trisomy 8 was observed in approximately 10% of tumorcell metaphases.

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Fig. 1 a, b Histological and immunohistochemical analysis of thetumor (×100 magnification). a Hematoxylin–eosin staining is showingspindle-shaped cells organized in a storiform pattern characteristic ofdermatofibrosarcoma protuberans. b Tumor cells strongly express theCD34, as shown by the immunohistochemical staining. c–g Molecularcytogenetic analysis. c Partial RGH-banded karyotype showingabnormal chromosomes 5 and 8—der(5) and der(8)—resulting froma translocation t(5;8) and a paracentric inversion of 5q on the der(8).The chromosomes 17 and 22 are apparently normal. According to theInternational System for Human Cytogenetic Nomenclature [30], thekaryotype was 46,XY,der(5)t(5;8)(q14;p21),der(8)t(5;8)inv(5)(q14q33)/47,idem, +8/47,XY,+8. d–g Fluorescence in situ hybridiza-tion (FISH) on tumor cell metaphases. d Schematic representation ofthe breakpoints (double arrows) within chromosomes 5 (blue) and8 (green). The der(5) resulted from a translocation with chromosome8, while the der(8) resulted from the t(5;8) and from a paracentricinversion of a 71-Mb fragment comprised between 5q14.2 and 5q33.2.The orientation of the 5q14.2–q33.2 is identified by a gradient of blue:dark on the 5q14.2 extremity and light on the 5q33.2 extremity. AllBAC probes presented are from the RP11 library. Genes present in

breakpoints are in brackets. The proximal breakpoint of the 5q14.2–q33.2 inverted fragment was identified by a split of the RP11-5503probe containing CSPG2. The distal breakpoint was identified by asplit of the BAC clone RP11-653K21 containing CNOT8, GEMIN5,and MRPL22. e Signals of the BAC probe RP11-615F9 (green),containing the PTK2B gene (8p21.2) are observed on both der(5) andder(8) indicating that the 8p21 breakpoint is located in PTK2B. f Co-hybridization of centromeric probe for chromosome 8 (red) and BACclone RP11-55O3 (green) containing the CSPG2 gene (5q14.2)showed green signals on both der(5) and der(8) indicating that the5q14.2 breakpoint was located in CSPG2. In addition, the presence ofthe green signal on the der(8) on the distal position close to thetelomere confirmed the inversion of the 5q14.2–q33.2 fragment on theder(8). g Co-hybridization of the centromeric probe for chromosome8 (red) and the BAC clone RP11-653K21 (containing CNOT8,GEMIN5, and MRPL22) showed two green signals on the short armof the der(8), indicating that the distal breakpoint of the inverted5q14.2–q33.2 fragment was located on the der(8) close to thecentromere

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Table 1 Description and origin of the FISH probes used for the characterization of the complex t(5;8) in a case of dermatofibrosarcomaprotuberans without COL1A1-PDGFB fusion

Result: chromosomal localization Probe name Type Chromosomal location/accession number/ gene of interest Origin/reference(s)

Whole chromosome painting probesNormal WCP17 Chromosome 17 Euro-DiagnosticaNormal WCP22 Chromosome 22 Euro-Diagnosticader(5)/der(8) WCP5 Chromosome 5 Euro-Diagnosticader(5)/der(8) WCP8 Chromosome 8 Q-BiogeneGene- and locus-specific probesChromosome 22Normal RP11-1149b8 BAC 22q13.1 58 kb centromeric to PDGFB RPCINormal RP11-434E5 BAC 22q13.1 79 kb telomeric to PDGFB RPCINormal RP11-101B10 BAC 22q13.1 RPCIChromosome 8der(5) 965_d_3 YAC 8p22 PDGFRL CEPHder(5) RP11-203E8 BAC 8p21.2 RMCder(5) 767_g_4 YAC 8p21.2 NEFL CEPHder(5) RP11-199N14 BAC 8p21.2 RPCIder(5) CTD-3000I12 BAC 8p21.2 Invitrogender(5)/der(8)* RP11-615F9 BAC 8p21.2 PTK2B RPCIder(8)* RP11-138J2 BAC 8p21.2 PTK2B RPCIder(8)* SCB-212E3 BAC 8p21.1 AF311103/PTK2B LIAR-FLIder(8)* RP11-360M9 BAC 8p21.1 AC011132 RMCder(8)* 778_b_12 YAC 8p21.1 CEPHder(8)* 901_e_10 YAC 8p12 CEPHder(8)* 815_e_8 YAC 8p12 CEPHder(8)* 978_b_9 YAC 8p12 HGL CEPHder(8)* 953_h_12 YAC 8p12 FGFR1, WRN CEPHder(8)* 959_a_4 YAC 8p11.23 FGFR1 CEPHChromosome 5der(5) RP11-195E2 BAC 5q13.2 RPCIder(5) RP11-172K14 BAC 5q13.3 RPCIder(5) RP11-1H14 BAC 5q14.1 RPCIder(5) RP11-1E10 BAC 5q14.1 RPCIder(5) RP11-47N20 BAC 5q14.2 RPCIder(5)/der(8)** CTD-3143O9 BAC 5q14.2–14.3 CSPG2 (exons 1 to 12) Invitrogender(5)/der(8)** RP11-275E14 BAC 5q14.2 CSPG2 (all exons) RPCIder(5)/der(8)** RP11-55O3 BAC 5q14.2 CSPG2 (exons 6 to 15) RPCIder(8)** RP11-95A21 BAC 5q14.3 RPCIder(8)* RP11-136E22 BAC 5q33.1 PERC, PDEGA RPCIder(8)* RP11-21I20 BAC 5q33.1 PDGFRB RPCIder(8)* RP11-754J8 BAC 5q33.1 PDGFRB RPCIder(8)* RP11-368O19 BAC 5q33.1 PDGFRB RMCder(8)* RP11-759G10 BAC 5q33.1 RPCIder(8)* RP11-802B10 BAC 5q33.1–q32 RPCIder(8)* RP11-802B10 BAC 5p33.1 RPCIder(8)* RP11-59F21 BAC 5q33.1 RPCIder(8)* RP11-963P19 BAC 5q33.1 RPCIder(8)* RP11-109B15 BAC 5q33.1 RPCIder(8)* RP11-91G17 BAC 5q33.2 RPCIder(8)* RP11-282L23 BAC 5q33.2 RPCIder(8)* CTD-2332P4 BAC 5q33.2 CNOT8 Invitrogender(8)*/der(8)** CTD-2527O23 BAC 5q33.2 CNOT8, GEMIN5, MRPL22 Invitrogender(8)*/der(8)** RP11-452J22 BAC 5q33.2 CNOT8, GEMIN5, MRPL22 RPCIder(8)*/der(8)** RP11-653K21 BAC 5q33.2 CNOT8, GEMIN5, MRPL22 RPCIder(8)** RP11-1149B7 BAC 5q33.2 RPCI

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Absence of chromosomes 17 and 22 rearrangementand COL1A1-PDGFB fusion

The karyotype analysis (Fig. 1c) and FISH experimentswith WCP probes for chromosomes 17 and 22 showed noevidence for rearrangements of chromosomes 17 and 22(Table 1). In addition, FISH with PDGFB “break-apart”probes RP11-1149B8 (3′), RP11-434E5 (5′), and RP11-101B10 (5′) showed no rearrangement and no extra signalin addition of the signals on the two normal chromosomes22 (Table 1). The RT-PCR analysis was negative for theCOL1A1-PDGFB fusion gene detection.

Mapping of the 8p breakpoint

A collection of 15 probes located between 8p11.23 and 8p22were hybridized on tumor cell metaphases (Table 1). Thebreakpoint was identified at 8p21.2, between the probesCTD-3000I12 (distal side), and RP11-138J2 (proximal side)within a 870-kb interval. The hybridization of the probeRP11-615F9 spanning this interval exhibited signals on bothder(5) and der(8) (Fig. 1d,e). According to the detailed mapof this region (USCS Genome Browser; chr8:27,364,183–27,365,993; Mar. 2006), the breakpoint was located withinthe intron 2 of the PTK2B (protein tyrosine kinase B) gene.

Detailed characterization of the chromosome 5rearrangements

The characterization of the 5q rearrangement was per-formed using a collection of 30 BAC probes located withinthe 5q13.2–q35.1 region (Table 1). Probes comprisedbetween RP11-195E2 (5q13.2) and RP11-47N20 (5q14.2)were observed on the der(5), while the probes locatedbetween RP11-95A21 (5q14.3) and CTD-2332P4 (5q33.2)were detected on the der(8). As suggested by theconventional cytogenetic analysis, the position of the 5qprobes on the der(8) showed the presence of a paracentric

inversion of the 5q14.2–q33.2 fragment in addition to thet(5;8). Indeed, probes from the 5q14.3 region and probes ofthe 5q33-qter region located distally to RP11-1149B7 werepositioned close to the telomere of the der(8) short arm,while the probes from the 5q33.2 region located proximallyto CTD-2332P4 were positioned on the short arm of the der(8) close to the centromere. These results indicated that the5q paracentric inversion was generated by the occurrence oftwo breakpoints, one at 5q14.2 and one at 5q33.2,respectively. Probes RP11-275E14 and RP11-55O3 locatedat 5q14.2 (Table 1) exhibited two fluorescent signals, oneon the der(5) and one on the der(8), respectively (Fig. 1f).Probe CTD-3143O9 exhibited a bright signal on the der(5)and a very faint signal on the der(8). The signals on the der(8) were observed close to the telomere of the der(8) shortarm. Analysis of the detailed map of this region (UCSCgenome browser version Mar. 2006; chr5:82,736,091–82,981,443) identified the breakpoint within the CSPG2gene (Chondroitin Sulphate Proteoglycan 2 or Versican)between exons 9 and 12 (Table 1 and Fig. 1f). The distalbreakpoint on chromosome 5 was located within the 5q33.2cytoband. Each of the probes CTD-2527O23, RP11-452J22and RP11-653K21 showed two signals on the short armof the der(8): one close to the telomere, the other close tothe centromere (Table 1 and Fig. 1g). The analysis of thegenomic interval delineated by these three probes on theUSCC map (chr5:154,193,027–154,416,284; version Mar.2006) indicated that the area of the breakpoint containedthree genes: GEMIN5 (GEM-Associated Protein 5),MRPL22 (Mitochondrial Ribosomal Protein L22), andCNOT8 (CCR4-NOT transcription complex, subunit 8).

Discussion

Abnormal fusion genes resulting from simple chromosomaltranslocations are frequent in leukemias and sarcomas andhave recently been identified also in carcinomas [23]. Over

Table 1 (continued)

Result: chromosomal localization Probe name Type Chromosomal location/accession number/ gene of interest Origin/reference(s)

der(8)** RP11-1082K13 BAC 5q33.2 RPCIder(8)** RP11-31B18 BAC 5q33.2–q33.3 RPCIder(8)** RP11-117L6 BAC 5q35.1 RPCI

All BACs probes were chosen according to their localization on the University of California Santa Cruz genome browser version March 2006(http://www.genome.ucsc.edu); YAC probes were chosen according to their localization on the GDB Human Genome Database (http://www.gdb.org).BAC Bacterial artificial chromosome; YAC yeast artificial chromosome; WCP whole chromosome painting probe; RPCI Roswell Park CancerInstitute; CEPH Centre d’étude du polymorphisme Humain (http://www.cephb.fr); RMC Resources for Molecular Biology (University of Bari,Bari, Italy; http://www.biologia.uniba.it/rmc); LIAR-FLI Leibniz Institute for Age Research-Fritz Lipmann Institute (Jena, Germany: http://genome.imb-jena.de/); der(8)* the signal is observed on the p arm of the der(8), close to the centromere; der(8)** the signal is observed on the parm of the der(8), close to the telomere; Invitrogen, Carlbad, CA; Euro-Diagnostica, Arnhem, The Netherlands

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the last decades, the progressive discoveries of fusion geneshave been crucial for establishing novel tumor classifica-tions. Moreover, the detection of specific fusion genes byFISH or RT-PCR is now used routinely for diagnosingtumors or after residual diseases. When fusion genes areidentified in a type or subtype of sarcoma, it is usual thatmost cases exhibit a “major” type of fusion gene, while asmall subset of cases presents “variant” fusion genes. These“variant” fusion genes are usually made of the fusion of oneof the gene involved in the “major” type with anotherpartner gene. For instance, the predominant fusion gene inperipheral neuroectodermic tumors (PNET) is EWS-FLI1,present in 90–95% of cases. Genes of the ETS family otherthan FLI1, such as ERG, FEV, ETV1, or ETV4 are alsofound to be fused with EWS in PNET [28]. In some othertypes of tumors, two major types of fusion are observed: forinstance, in pleomorphic adenoma of the salivary gland,fusion genes involving either PLAG1 at 8q12 (CTNNB1-PLAG1, LIFR-PLAG1, and TCEA1-PLAG1) [3, 14, 39] orHMGA2 at 12q15 (HMGA2-NFIB, HMGA2-FHIT, andHMGA2-WIF1) [10, 11, 25] are detected.

Only one type of fusion gene — the COL1A1-PDGFBfusion — had been identified in DFSP so far [4, 34]. Wehave described in this paper the first DFSP case with a“variant” molecular rearrangement. This DFSP case had noclinical or histological particularity and was characterizedby a complex rearrangement of chromosomes 5 and8 involving three breakpoints located at 8p21, 5q14, and5q33, respectively. Strikingly, the PDGFRB gene thatencodes the receptor of PDGFB is located at 5q33. It hasbeen shown that the chimeric COL1A1-PDGFB protein isable to undergo cleavage and acts as a ligand for PDGFR,therefore, leading to activation of the PDGFR signalingpathway [31]. This abnormal stimulation of PDGFR isinactivated by the tyrosine kinase inhibitor imatinibmesylate and allows an efficient pharmacological treatmentfor metastatic or non-operable DFSP [22]. Moreover,PDGFRB is a gene that is prone to the formation of fusiongenes resulting from chromosomal translocations. Indeed,chimeric genes generated by the fusion of PDGFRB withPDE4DIP, HIP1, H4, or ETV6 have been reported inmyeloproliferative disorders and leukemias [16]. ThePDGFRB gene was therefore a likely candidate for beinginvolved in the 5q33 breakpoint of the present DFSP case.However, we showed that the breakpoint at 5q33.2 waslocated in the region of the CNOT8, MRPL22, and GEMIN5 genes. PDGFRB was located on the short arm of the der(8) at distances of 63 Mb from the proximal breakpoint and153 Mb from the distal breakpoint, respectively (Table 1).These large distances excluded PDGFRB from beingdirectly or indirectly involved in this rearrangement. Weidentified that the breakages in 5q14 and 8p21.2 werelocated in the CSPG2 and PTK2B genes, respectively. We

mapped the 8p breakpoint within the intron 2 of PTK2B(also called PYK2) and the 5q14 breakpoint between theexons 9 and 12 of CSPG2. The genomic rearrangementgenerated by the t(5;8) and the paracentric 5q inversionmay potentially lead to the formation of three fusion genes:CSPG2-PTK2B on the der(5), PTK2B-CNOT8 (or PTK2B-MRPL22 or PTK2B-GEMIN5) on the proximal side of theder(8) short arm, and CNOT8-CSPG2 or (MRPL22-CSPG2or GEMIN5-CSPG2) on the distal side of the der(8) shortarm. However, because of their 5′–3′ orientation, some ofthese putative fusion genes might not be functional. Thesole genomic configurations compatible with the produc-tion of in frame fusion transcripts are MRPL22-PTK2B,CNOT8-PTK2B, or GEMIN5-CSPG2. PTK2B is a cyto-plasmic tyrosine kinase structurally related to the focaladhesion kinase [29]. The activation of PTK2B leads to theactivation of the MAP kinase pathway via interaction with aSrc kinase protein [15]. The breakage of PTK2B in intron 2is able to preserve the tyrosine kinase domain integrity.Therefore, the functional consequences of the PTK2Bactivation could be similar to the PDGFRB activationobserved in “classical” DFSP by stimulating the MAPkinase pathway. The overexpression of PTK2B has beenreported in hepatocellular carcinomas as a marker of poorprognosis; in glioma, PTK2B promotes cellular migrationand invasion [18, 36]. We described in this paper the firstcase of genomic involvement of PTK2B in a chromosomalrearrangement. In the hypothesis of a MRPL22-PTK2Bfusion, MRPL22, which encodes a ribosomal protein part ofthe 39S subunit, could be able to drive an abnormalexpression of PTK2B by its “housekeeping” promoter [9].CNOT8 encodes the 8 subunit of the CCR4-NOT complex,which acts as an ubiquitous transcription regulator [2].CNOT8 is a relevant candidate to form a fusion gene withPTK2B, as one or both of the genes involved inchromosomal translocations often encode transcriptionfactors. CSPG2 codes for a large chondroitin sulfateproteoglycan found in the extracellular matrix; it modulatescell adhesion, migration, proliferation, and differentiation[40]. High levels of CSPG2 have been detected in a varietyof malignant solid tumors, such as pancreatic carcinomas,breast carcinomas, prostate carcinomas, brain tumors,melanomas, and malignant fibrous histiocytomas [5, 13,21, 24, 26, 38]. GEMIN5 encodes a WD-repeat scaffoldingprotein involved in ribonucleoprotein assembly [8]. Thedomains downstream exon 9 of CSPG2 have been reportedto enhance cell proliferation via the EGF-like motifs in amodel of NIH3T3 fibroblasts and in a sarcoma cell line [6,41]. As these motifs are potentially preserved in the 3′ endof the GEMIN5-CSPG2 fusion gene, GEMIN5 promotercould act as an activator for the transcription of CSPG2.

In conclusion, we have described in this paper the firstcase of DFSP without a molecular rearrangement of

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COL1A1 and PDGFB. We have identified a novelrearrangement of chromosomes 5 and 8 involving theCSPG2 and PTK2B genes. Three other genes located at5q33, CNOT8, MRPL22, and GEMIN5, might also beinvolved in this rearrangement. The identification of variantfusion genes in DFSP is of importance for improving themolecular diagnoses of this tumor. Indeed, while thepositive detection of the COL1A1-PDGFB fusion gene ina tumor sample ascertains the diagnosis of DFSP, a negativeresult has to be carefully interpreted. This negative resultindicates in most cases that the tumor is not a DFSP.However, in a small number of cases, it could reflect thepresence of a molecular variant, as in the case described inthis paper. The characterization of these variant cases ismandatory to provide not only a more accurate diagnosisbut also a better understanding of the molecular andbiological mechanisms that are involved in the DFSPtumorigenesis.

Acknowledgments We thank M. Rocchi (University of Bari, Italy),M-J Pébusque, M. Chaffanet, and D. Birnbaum (Institut PaoliCalmettes, Marseille, France) for kindly providing some of the BACand YAC clones used in this study. This work was supported by theComité des Alpes-Maritimes de la Ligue Nationale contre le Cancer,the Association pour la Recherche sur le Cancer, the Institut Nationaldu Cancer, and the Fondation pour la Recherche Médicale (mastergrant to P. Follana). The experiments described in this study complywith the current laws of France.

Conflict of interest statement We declare that we have no conflictof interest.

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