Original Article Cytogenet Cell Genet 94:9–14 (2001) The characterisation of the lymphoma cell line U937, using comparative genomic hybridisation and multi-plex FISH J.C. Strefford, a,c N.J. Foot, a T. Chaplin, a M.J. Neat, a R.T.D. Oliver, b,c B.D. Young a and L.K. Jones a a ICRF Medical Oncology Unit, Queen Mary and Westfield College, London; b Department of Medical Oncology and c The Orchid Cancer Appeal, St Bartholomew’s Hospital, London (UK) Supported by the Orchid Cancer Appeal and by the Imperial Cancer Research Fund. Received 10 January 2001; accepted 10 May 2001. Request reprints from Jon C. Strefford, ICRF Medical Oncology Unit, Queen Mary and Westfield College, Charterhouse Square, London, EC1M 6BQ (UK); telephone: 0207 882 6003; fax: 0207 882 6004; email: J.Strefford@icrf.icnet.uk ABC Fax + 41 61 306 12 34 E-mail karger@karger.ch www.karger.com © 2001 S. Karger AG, Basel 0301–0171/01/0942–0009$17.50/0 Accessible online at: www.karger.com/journals/ccg Abstract. The cell line U937, which has been used exten- sively for studies of myeloid differentiation, bears the t(10;11)(p13;q14) translocation which results in a fusion be- tween the MLLT10 (myeloid/lymphoid or mixed-lineage leuke- mia [trithorax, Drosophila, homolog]; translocated to 10; alias AF10) gene and the Ap-3-like clathrin assembly protein, PI- CALM (Clathrin assembly lymphoid myeloid leukaemia). Apart from this translocation, very little is known about the other genetic alterations in this cell line that may represent sig- nificant events in disease progression. In this study, conven- tional G-banding, CGH and M-FISH have been used to charac- terise fully all of the cytogenetic alterations present in the U937 cell line. M-FISH analysis confirmed the presence of the t(10;11) and an apparently normal copy of both chromosomes 10 and 11. A t(1;5) translocation was observed as well as several unbalanced rearrangements. CGH detected amplifications re- sulting from duplications of 2q, 6p and 13q. These changes could result in fusion gene products involved in carcinogenesis or the positions of putative oncogenes and tumour suppressor genes. A good correlation between conventional G-banding, CGH and M-FISH was observed. Copyright © 2001 S. Karger AG, Basel The U937 cell line was originally established from a patient with diffuse histiocytic lymphoma (Sundstrom and Nilsson, 1976). This cell line has been used extensively in myeloid dif- ferentiation studies (Ralph et al., 1976; 1983) and in the char- acterisation of the t(10;11)(p13;q14), a fusion between the MLLT10 gene and the Ap-3-like clathrin assembly protein, PICALM (Dreyling et al., 1996). Apart from the PICALM: MLLT10 gene fusion, very little is known about the genetic abnormalities of U937. Its karyotype is complex (Shipley et al., 1988) and the true identities of many rearrangements have not yet been resolved. Although the t(10;11) and its genetic role in leukaemogenesis has been well characterised (Dreyling et al., 1996), little is known about other significant genetic events in this cell line and their potential synergistic effects. Recent advances in molecular technology have had consid- erable impact on cytogenetic analysis, allowing greater resolu- tion and accuracy. Significant advances in fluorescence tech- nology include the development of comparative genomic hy- bridisation (CGH) (Kallioniemi et al., 1994) and multiplex FISH (M-FISH) (Speicher et al., 1996). In essence, CGH pro- vides information on those regions gained or lost in the DNA of a tumour specimen. This method has been used to investigate genetic changes in a wide spectrum of human cancer (Visakorpi et al., 1995; Bergamo et al., 2000; Loveday et al., 2000; Schleger et al., 2000) including lymphoma (Ohshima et al., 1999; Arranz et al., 2000; Peters et al., 2000). M-FISH is a combinatorial technique that allows the identification of human chromo- somes by “painting” them with a spectrum of DNA probes labelled with a unique combination of five fluorochromes.