SHORT REPORT g-heregulin is the product of a chromosomal translocation fusing the DOC4 and HGL/NRG1 genes in the MDA-MB-175 breast cancer cell line Xiao-Zhong Wang 1,2 , Ethel M Jolicoeur 1,2 , Nathalie Conte 4 , Max Chaanet 4 , Yuhong Zhang 1,2 , Marie-JoeÈ lle Mozziconacci 5 , Helen Feiner 3 , Daniel Birnbaum 4 , Marie-JoseÁphe PeÂbusque 4 and David Ron* ,1,2 1 Department of Medicine, Skirball Institute of Biomolecular Medicine, Kaplan Cancer Center, NYU Medical Center, New York, NY 10016, USA; 2 Department of Cell Biology, Skirball Institute of Biomolecular Medicine, Kaplan Cancer Center, NYU Medical Center, New York, NY 10016, USA; 3 Department of Pathology, Skirball Institute of Biomolecular Medicine, Kaplan Cancer Center, NYU Medical Center, New York, NY 10016, USA; 4 Institut de CanceÂrologie et d'Immunologie de Marseille, France; 5 Institut Paoli-Calmettes, Laboratoire de Cyloge ÂneÂtique, 13009 Marseille, France g-heregulin is a recently described novel isoform of the heregulin/neuregulin class of EGF-like ligands that bind to and activate receptors of the ErbB family. Deregu- lated signaling through the heregulin-ErbB pathway is thought to be implicated in the development of a subset of human breast cancers. g-heregulin has been found to be expressed in the culture supernatant of MDA-MB- 175, a breast carcinoma cell line. g-heregulin is characterized by the presence of a large N-terminal peptide extension that is not found in other heregulin isoforms. Here we report that this unique N-terminal extension of g-heregulin is identical to the N-terminus of DOC4, a product of a recently identi®ed CHOP- dependent stress-induced gene. Human DOC4 and the heregulin-encoding genes map to dierent chromosomes and the MDA-MB-175 cell line contains a chromosomal translocation that leads to the fusion of DOC4 and HGL, on chromosomes 11 and 8, respectively. Thus, g- heregulin is a product of a mutant fusion gene and not a bona ®de normal isoform. We speculate that the mutation may be selected for by virtue of its ability to activate ErbB signaling through the production of an autocrine ligand. Keywords: signal transduction; EGF receptor; tyrosine kinase; tenascin; CHOP Heregulins (or neuregulins) are a group of soluble and cell-membrane bound EGF-like peptide ligands that signal through a related class of tyrosine kinase receptors belonging to the ERBB family and are encoded by three distinct genes (Burden and Yarden, 1997). Deregulated signaling through the heregulin- ErbB pathway is thought to play a role in the development of a subset of human breast cancers (reviewed in Lupu et al., 1996; Normanno et al., 1994). This has generated a substantial interest in identifying and characterizing the genes and proteins involved in this pathway. g-heregulin is a novel heregulin isoform that was identi®ed in the culture supernatant of MDA-MB-175, a human breast carcinoma cell line (Schaefer et al., 1997). Cloning of the g-heregulin cDNA revealed its C-terminus to be identical to previously characterized heregulin isoforms encoded by the HGL/NRG1 gene. However, its N-terminal predicted peptide sequence is unrelated to any known heregulin. It was suggested that g-heregulin is a novel splicing variant of the HGL gene. We have recently cloned DOC4, a gene that is induced during cellular stress (Wang et al., 1998). DOC4 encodes a large secreted protein that is related to Drosophila Tenm, a protein that plays a critical role in early ¯y development (Baumgartner et al., 1994; Levine et al., 1994). Comparison of the predicted peptide sequence of DOC4 to other known proteins revealed complete sequence identity between its N- terminus and the novel portion of g-heregulin. C- terminal to this region of identity, the two proteins are completely dissimilar (Figure 1). This alignment is consistent with two possibilities: either g-heregulin and DOC4 represent alternatively processed products of the same gene or g-heregulin is a product of a translocation that fuses two dierent genes (DOC4 and HGL). Here we present data supporting the latter explanation. We determined the chromosomal location of human DOC4 and con®rmed the address of human HGL. DOC4 mapped to band q13 on human chromosome 11. This result was obtained by both radiation hybrid mapping on the GeneBridge 4 panel and by FISH analysis using YAC 803D7 that contains the DOC4 gene (Figure 2a and b). The YAC was isolated from the CEPH libraries (Centre d'Etudes du Polymor- phisme Humain, Paris, France). HGL's location at band p12 of chromosome 8 was con®rmed by the same two criteria (Figure 2a and c). Next we performed dual channel FISH analysis using HGL and DOC4 speci®c YAC probes, that had been labeled with dierent ¯uorochromes as previously described (Chaanet et al., 1996). Overlapping DOC4 and HGL signals were identi®ed on the two 8;11 derivative chromosomes present in the aneuploid MDA-MB-175 cells (Figure 2c) but not in any other cell tested (not shown). The karyotype of MDA-MB-175 cell line is hypotetraploid, modal number: 89, with complex chromosomal rearrangements that include several alterations in chromosomes 8 and 11: 78, der(8;11)t(8;11) *Correspondence: D Ron, Department of Medicine, Skirball Institute of Biomolecular Medicine, Kaplan Cancer Centre, NYU Medical Center, New York, NY 10016, USA Received 24 February 1999; accepted 4 May 1999 Oncogene (1999) 18, 5718 ± 5721 ã 1999 Stockton Press All rights reserved 0950 ± 9232/99 $15.00 http://www.stockton-press.co.uk/onc