Journal of Cellular Biochemistry 88:569–577 (2003) Differential Regulation of Notch Signal Transduction in Leukaemia and Lymphoma Cells in Culture Raffaella Chiaramonte, 1 Elisabetta Calzavara, 1 Francesca Balordi, 1 Marta Sabbadini, 1 Daniela Capello, 2 Gianluca Gaidano, 2 Anna Serra, 3 Paola Comi, 1 and G.V. Sherbet 4,5 * 1 Department of Biomedical Sciences and Technologies, University of Milano, LITA-via Fratelli Cervi 93-20090 Segrate (MI), Italy 2 Department of Medical Sciences, Universita ` degli Studi del Piemonte Orientale, via Solaroli 17, 28100 Novara, Italy 3 Department of Clinical and Biological Science, University of Torino, San Luigi Hospital, 10043 Orbassano, Torino, Italy 4 Communications and Signal Processing Research Group, Department of Electrical and Electronic Engineering, University of Newcastle upon Tyne, United Kingdom 5 Institute for Molecular Medicine, 15162 Triton Lane, Huntington Beach, California Abstract The transduction of Notch signal plays an intricate role in cell differentiation and pathogenesis of haematological malignancies as well as in certain congenital conditions. We found no genomic changes in either gene in 34 leukaemic samples and 25 leukaemia and lymphoma cell lines. The functionality of Notch signalling was tested using HES1 gene activation. We show that Notch signalling is differentially regulated in T-acute lymphoblastic leukaemia (ALL) and B-lymphoma cells. The Notch pathway is intact in a majority of B-lymphoma cell lines, but EBNA2, which mimics notch function, can occasionally activate the pathway. In contrast, the Notch pathway is constitutively active in T-ALL. This is the first demonstration of a distinction between B-lymphomas and T-cell leukaemias in the functioning of the Notch-signalling pathway. This might be related to their pathogenesis. J. Cell. Biochem. 88: 569 – 577, 2003. ß 2003 Wiley-Liss, Inc. Key words: leukaemia; lymphoma; notch signalling; HES1; EBNA The Notch signalling pathway plays a major role in the differentiation of many cell types as well as in the pathogenesis of haematological malignancies such as leukaemias and lympho- mas, congenital autosomal dominant condition known as the Alagille syndrome and in cerebral autosomal dominant arteriopathy with subcor- tical infracts and leukoencephalopathy (CADA- SIL). Notch1 plays an essential role during embryogenesis [Swiatek et al., 1994], specifi- cally being implicated in myogenesis and neu- rogenesis [Nye et al., 1994; De la Pompa et al., 1997]. Its role is fundamental to the hemato- poietic process, yet it is not fully understood. Notch is expressed in the human bone marrow haemopoietic precursor cells and may be involved in the renewal and differentia- tion of these cells. It is able to inhibit the differentiation of haemopoietic cells into mye- loid lineage [Milner et al., 1996] and is involved in determining lymphopoietic lineage. Four notch genes viz. Notch1/TAN-1, Notch2, Notch3 and Notch4/int-3 have been identified and these are expressed in unique develop- mental patterns [Williams and Lardelli, 1995; Lindsell et al., 1996]. The Notch proteins bind their ligands in a non-preferential fashion. The DSL (Delta/Serrate/Lag2) family of genes encode for these ligands, which include the vertebrate homologues of Jagged1 and Jagged2 ß 2003 Wiley-Liss, Inc. Grant sponsor: MURST; Grant sponsor: CARIPLO (to P.C.). *Correspondence to: Prof. G. V. Sherbet, Dept. of Electrical and Electronic Engineering, University of Newcastle upon Tyne, Merz Court, Newcastle upon Tyne NE1 7RU, United Kingdom. E-mail: gsherbet@immed.org Received 29 April 2002; Accepted 11 September 2002 DOI 10.1002/jcb.10383