HMGIC, the gene for an architectural transcription factor, is ampli®ed and rearranged in a subset of human sarcomas Jeanne-Marie Berner 1 , Leonardo A Meza-Zepeda 1 , Patrick FJ Kools 2 , Anne Forus 1 , Eric FPM Schoenmakers 2 , Wim JM Van de Ven 2 , éystein Fodstad 1 and Ola Myklebost 1 1 Department of Tumor Biology, The Norwegian Radium Hospital, Oslo, Norway; 2 Laboratory of Molecular Oncology, Center for Human Genetics, University of Leuven, Flanders Interuniversity Institute for Biotechnology, Herestraat 49, B-3000 Leuven, Belgium Ampli®ed segments of the long arm of chromosome 12 are frequently observed in human sarcomas. In most cases there are separate ampli®ed regions around the MDM2 and CDK4 genes. Here we show recurrent ampli®cation of a third region encompassing HMGIC, a human architectural transcription factor gene. Reduced ampli®- cation frequency of sequences ¯anking the gene was observed, indicating that inclusion of this third region in the amplicons is also selected for. In three samples only the 5' part of HMGIC was ampli®ed, suggesting preferential loss of the 3' part of the gene preceding or during ampli®cation. In several other samples rearrange- ment of the gene was observed. Expression analysis showed transcripts of aberrant sizes, lacking 3' sequences, and 3' RACE of one sample revealed replacement of exons 4 and 5 with ectopic sequences. This truncation of HMGIC resembles that reported for translocations of HMGIC in benign tumors, including lipomas, and it is striking that the gene was frequently ampli®ed or rearranged in well dierentiated liposarcomas, the malignant counterpart of lipomas. It seems conceivable that high levels of either full length or truncated hmgic could be relevant for the etiology of these tumors Keywords: chromosome 12q13 ± 15; amplicon; MAR; MDM2; HMGIC Introduction The q13 ± 15 segment of chromosome 12 is frequently ampli®ed in human sarcomas of various kinds (Roberts et al., 1989; Forus et al., 1991, 1993, 1994; Oliner et al., 1992; Smith et al., 1992; Khatib et al., 1993; Flùrenes et al., 1994). In our sarcoma panel, the most frequently ampli®ed genes were MDM2, CDK4 and SAS, but none of these were included in all amplicons (Forus et al., 1993; Maelandsmo et al., 1995; Berner et al., 1996). It seems likely that ampli®cation could be selected for by over-production of mdm2, a protein that binds to and inactivates the tumor suppressor p53 (Momand et al., 1992). Cyclin-dependent kinase 4 (cdk4), on the other hand, under certain conditions phosphorylates the retinoblastoma tumor suppressor protein (pRB), releasing pRB-mediated G 1 arrest (Ewen et al., 1993). Thus, by ampli®cation of this chromosomal segment, both these two major growth regulatory pathways may be inhibited. We have previously found discrete amplicons around MDM2 and CDK4, suggesting that there is separate selection for ampli®cation of the two genes, and making a common selective gene located in the intergenic region unlikely (Berner et al., 1996). The region around MDM2 is shown to harbor recurrent breakpoints in a variety of benign solid tumors (Schoenmakers et al., 1994; Van de Ven et al., 1995). Recently, the HMGIC gene was localized to this `multiple aberration region' (MAR) and reported to be target for translocation in eight dierent benign solid tumor types (Ashar et al., 1995; Schoenmakers et al., 1995b). HMGIC encodes a member of the family of high mobility group (HMG) proteins, characterized by AT-hooks; DNA binding domains that are able to bind to the minor groove of DNA (Reeves and Nissen, 1990). These proteins may modulate DNA conforma- tion and are thought to be architectural elements in the assembly of transcriptional complexes (Grosschedl et al., 1994; Wollfe, 1994). The hmgic protein is abundant only in transformed cells, and a correlation between an elevated level of hmgic and a malignant phenotype has been demonstrated (Patel et al., 1994; Chiappetta et al., 1995). Furthermore, it has been shown that expression of antisense HMGIC is able to prevent retrovirally induced tumor progression in rat thyroid cells (Berlingieri et al., 1995). In this study we have determined the ampli®cation status of this gene in 122 human sarcomas. We have further analysed the involvement of 11 loci mapped within MAR in 21 human sarcomas with 12q13 ± 15 ampli®cation, and rearrangement of HMGIC was studied in a subset of sarcomas by Northern and 3' RACE analysis. Results Ampli®cation of MAR loci We have previously detected ampli®cation in the q13 ± 15 region of chromosome 12 in a large panel of human sarcomas by molecular analysis and comparative genomic hybridization (CGH) (Forus et al., 1993, 1995a,b; Maelandsmo et al., 1995; Berner et al., 1996). Here we used Southern blot hybridization to determine the ampli®cation pattern of HMGIC in essentially the same panel, consisting of 122 human sarcomas. Using a probe from the 5' part of HMGIC, including the coding region (probe B), we detected ampli®cation of HMGIC in 13 of the sarcomas (10%), all samples with Correspondence: O Myklebost Received 30 September 1996; revised 3 March 1997; accepted 4 March 1997 Oncogene (1997) 14, 2935 ± 2941  1997 Stockton Press All rights reserved 0950 ± 9232/97 $12.00