A Cross-Linker-Sensitive Myeloid Leukemia Cell Line from a 2-Year-old Boy with Severe Fanconi Anemia and Biallelic FANCD1/BRCA2 Mutations Stefan Meyer, 1,2 * William D. Fergusson, 3 Anneke B. Oostra, 4 Annette L. Medhurst, 4 Quinten Waisfisz, 4 JohanP. de Winter, 4 Fei Chen, 4 Trevor F. Carr, 2 Jill Clayton-Smith, 3 Tara Clancy, 3 Mike Green, 5 Lisa Barber, 1 Osborn B. Eden, 2 Andrew M. Will, 2 Hans Joenje, 4 and G. Malcolm Taylor 1 1 Cancer-Immunogenetics Laboratory, University of Manchester, Manchester, United Kingdom 2 Department of Paediatric Haematology and Oncology, Central Manchester and Manchester Children’s University Hospital NHS Trust, Manchester, United Kingdom 3 Regional Genetics Service and Academic Unit of Medical Genetics, Central Manchester and Manchester Children’s University Hospital NHS Trust, Manchester, United Kingdom 4 Department of Human Genetics and Clinical Genetics, Free University of Amsterdam, Amsterdam, The Netherlands 5 Regional Oncology Cytogenetics Service, Christie Hospital NHS Trust, Manchester, United Kingdom Fanconi anemia (FA) is a rare autosomal recessive disorder characterized by congenital and developmental abnormalities, hypersensitivity to DNA cross-linking agents such as mitomycin C (MMC), and strong predisposition to acute myeloid leuke- mia (AML). In this article, we describe clinical and molecular findings in a boy with a severe FA phenotype who developed AML by the age of 2. Although he lacked a strong family history of cancer, he was subsequently shown to carry biallelic muta- tions in the FANCD1/BRCA2 gene. These included an IVS7 splice-site mutation, which is strongly associated with early AML in homozygous or compound heterozygous carrier status in FA-D1 patients. Myeloid leukemia cells from this patient have been maintained in culture for more than 1 year and have been designated as the SB1690CB cell line. Growth of SB1690CB is dependent on granulocyte macrophage colony stimulating factor or interleukin-3. This cell line has retained its MMC sensitiv- ity and has undergone further spontaneous changes in the spectrum of cytogenetic aberrations compared with the primary leukemia. This is the second AML cell line derived from an FA-D1 patient and the first proof that malignant clones arising in FA patients can retain inherited MMC sensitivity. As FA-derived malignancies are normally not very responsive to treatment, this implies there are important mechanisms of acquiring correction of the cellular FA phenotype that would explain the poor chemoresponsiveness observed in FA-associated malignancies and might also play a role in the initiation and progression of cancer in the general population. ' 2005 Wiley-Liss, Inc. INTRODUCTION Fanconi anaemia (FA) is a rare autosomal reces- sive disorder characterized by variable congenital and developmental abnormalities and very high predisposition to acute myeloid leukemia (AML) and squamous cell carcinoma. Cells from FA patients display spontaneous chromosomal break- age and increased sensitivity to DNA cross-linking agents such as mitomycin C (MMC) and dieboxy- butane (DEB). Demonstration of MMC and DEB hypersensitivity is used as the standard diagnostic test for FA (Joenje and Patel, 2001; D’Andrea and Grompe, 2003). FA is genetically heterogeneous; current evidence suggests that it can be caused by pathogenic mutations in at least 11 genes. Cellular complementation analysis has identified FA groups A, B, C, D1, D2, E, F, G, and, more recently,I and J, for which FANCA, FANCC, FANCD2, FANCE, FANCF, and FANCG/XRCC9 have been identified as distinct disease genes (Joenje and Patel, 2001; D’Andrea and Grompe, 2003; Levitus et al., 2004). Most recently, FANCL was discovered by protein association (Metei et al., 2003). Patients of the FA-complementation group D1 FA have been shown to carry mutations in the BRCA2 gene, implying that BRCA2 is another disease gene for FA (Howlett et al., 2002). Proteins encoded by FA genes interact with each other in a common pathway, which explains the shared cellular and clinical phenotypic features of FA. The upstream component of this pathway *Correspondence to: Dr. Stefan Meyer, MD, MRCPCH, Cancer- Immunogenetics Laboratory, Paediatric Oncology, St. Mary’s Hospi- tal, Hathersage Road, Manchester M13 OJH, United Kingdom. E-mail: stefan.meyer@man.ac.uk Supported by: Leukaemia Research Fund (UK) Clinical Research Fellowship (to S.M.); Cancer Research UK (to O.B.E., G.M.T., and L.B.); Netherlands Organization for Health and Development (to J.P.dW. and Q.W.); and Dutch Cancer Society (to A.L.M.) Received 1 June 2004; Accepted 26 October 2004 DOI 10.1002/gcc.20153 Published online 11 January 2005 in Wiley InterScience (www.interscience.wiley.com). # 2005 Wiley-Liss, Inc. GENES, CHROMOSOMES & CANCER 42:404–415 (2005)