Title: Correlation of Neuron-Glial Antigen 2 (NG2) Expression to MLL Gene Rearrangements in Acute Lymphoblastic Leukemia
Authors: Hanaa Mohamed Afifi, Gehan Mostafa Hamed, Esraa Maonsour Shehata
DOI: http://dx.doi.org/10.18535/jmscr/v4i6.43
Background: Acute lymphoblastic leukemias (ALL) carrying a chromosomal translocation involving the mixed-lineage leukemia gene (MLL) has a particularly poor prognosis. The presence of the MLL translocation often results in an early relapse after chemotherapy. For this reason, the accurate detection of MLL rearrangements (MLL-r) is crucial when dealing with this aggressive type of leukemia. We determined the correlation of the surface antigen neuron-glial antigen 2 (NG2) to the presence of MLL-r, and its value as a rapid inexpensive method for prediction of MLL-r at diagnosis of ALL patients. Methods: 44 newly diagnosed children with ALL were studied for the presence of MLL rearrangement by fluorescence in situ hybridization (FISH), as well as measurement of NG2 expression by flow cytomery. Results: MLL-r was successfully detected in 16 (36.4%) patients, while NG2 expression was positive in 14 (31.8%) patients. A positive correlation was found between NG2 expression and MLL–r (r=0.531, p<0.001), receiver operating characteristic curve (ROC) analysis revealed that NG2 value ≥ 18.6% could predict the presence of MLL-r with 85% sensitivity, 95% specificity, and 90% accuracy (p=0.004). Hyperleucocytosis, high lactate dehydrogenase (LDH) level, and presence of central nervous system (CNS) infiltration were significantly higher in patients with MLL-r and positive NG2 expression compared with MLL-r negative and NG2 negative ALL patients (p<0.001). In conclusion, immunophenotypic analysis of NG2 expression with a cutoff value ≥ 18.6% allows the identification and prediction of MLL-r, with high specificity and accuracy suggesting that flow cytometry is a reliable, cost-effective and rapid tool for detection of MLL-r. Keywords: ALL, NG2 expression, MLL rearrangements. 1. Pui CH, Robison LL, Look AT. Acute lymphoblastic leukaemia. Lancet 2008;371:1030–43. 2. Marchesi E, Girardi K, Avvisati G. 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