Interphase fluorescent in situ hybridization deletion analysis of the 9 p 21 region and prognosis in childhood acute lymphoblastic leukaemia ( ALL ) : results from a prospective analysis of 519 Nordic patients

Inactivation of the 9p21 region has been reported in numerous malignant tumours, e.g. melanoma, mesotheliona, urinary bladder cancer, chordoma, gastrointestinal tumours (Chiosea et al, 2008; Haller et al, 2008; Hallor et al, 2008; Walker et al, 1998), as well as in acute lymphoblastic leukaemia (ALL) (Heyman & Einhorn, 1996; Mullighan et al, 2007; Ogawa et al, 1995; Tsuzuki et al, 2007). The prognostic importance of 9p21 deletion in childhood ALL has been debated for a long time (Calero Moreno et al, 2002; Faderl et al, 1999; Graf Einsiedel et al, 2001; Mirebeau et al, 2006). It is well recognized that the frequency of homozygous deletion in T-ALL is higher than in B-cell precursor (BCP)-ALL (approximately two-thirds of Ekaterina Kuchinskaya,* Mats Heyman,* Ann Nordgren, Stefan Söderhäll, Erik Forestier, Peder Wehner, Kim Vettenranta, Olafur Jonsson, Finn Wesenberg, Sigrid Sahlén, Magnus Nordenskjöld and Elisabeth Blennow Centre of Molecular Medicine and Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden, Astrid Lindgren’s Children’s Hospital, Karolinska University Hospital, Stockholm, Sweden, Department of Clinical Sciences, Paediatrics, University of Umeå, Umeå, Sweden, Paediatric Oncology Department, University Hospital, Odense, Denmark, Paediatric Oncology Department, University Hospital, Tampere, Finland, Childrens Hospital, Hringsins, Landspitali, Hringbraut, Reykjavik, Iceland, and Barneklinikken, Rikshospitalet, Oslo, Norway