A dual-color FISH assay distinguishes between ELL and MLLT1 (ENL) gene rearrangements in t(11;19)-positive acute leukemia

Abstract

Bonhoure et al. 8 reported that sustained SPHK1 overexpresion can render HL60 cells chemoresistant by decreasing the cellular ceramide level and that a novel SPHK1 inhibitor, F-12509a, could recover chemosensitivity. Considering the molecular target of chemotherapy, enzyme inhibitors are more practical than agents for enzyme activation (NSMase2 in our case). Inhibitor of SPHK1 is almost at the stage of clinical investigation. In the present study, we could analyze only one time point of patients (mostly at their first diagnosis before chemotherapy) and could not measure enzyme activities due to the paucity of samples. The measurement of SPHK1 gene expression and/or SPHK enzyme activity of each patient might be necessary to assess the efficacy of enzyme inhibitors in future clinical settings. Sequential analysis of the same patients will also add further information.The localization and activation of enzymes are also important factors to determine the final cellular ceramide/S1P rheostat. SPHK1 was reportedly activated by phosphorylation by agonists and translocated to membranes. 2 Therefore, further analysis of enzyme activation is necessary to conclude firmly that sphingolipid metabolizing enzymes such as SPHK1 are a novel and promising molecular target for acute leukemia chemotherapy.Taken together, this is, to our knowledge, the first report of a gene expression profile of major sphingolipid metabolizing enzymes of AL and MDS using quantitative RT-PCR, It documents the increase of SPHK1 gene expression in AL and RAEB-t and the decrease of NSMase2 gene expression in AL and RAEB, suggesting that sphingolipid metabolizing enzymes such as SPHK1 could be a novel target for the chemotherapy of AL. AcknowledgementsWe express sincere thanks to Professor S Nakamura and other members

A paediatric patient with AML M1 and a t(11;19)(q23;p13.1) rearrangement

“…In this patient the t(11;19) appears as the sole abnormality, which is characteristic of the t(11;19) rearrangement [1], and the myeloid sarcoma reported in the patient is a common finding in acute paediatric cases [3]. The 19p13.1 and 19p13.3 breakpoints are not always cytogenetically distinguishable [4]; however, the 19p13.2 band was observed on the der(11) in this case (Figure 1), meaning the proband is likely to have the t(11;19)(q23;p13.1) rearrangement (11q+, 19p-) which results in an MLL/ELL gene fusion [7]. As the banding resolution was only 350bph, confirmation of the rearrangement by FISH [4] or PCR-based testing would be desirable, as the literature suggests the MLL/ELL (MEN) fusion protein does not have a direct leukemogenic effect whereas the MLL/ENL (MLLT1) protein does [3,15].…”

“…The 19p13.1 and 19p13.3 breakpoints are not always cytogenetically distinguishable [4]; however, the 19p13.2 band was observed on the der(11) in this case (Figure 1), meaning the proband is likely to have the t(11;19)(q23;p13.1) rearrangement (11q+, 19p-) which results in an MLL/ELL gene fusion [7]. As the banding resolution was only 350bph, confirmation of the rearrangement by FISH [4] or PCR-based testing would be desirable, as the literature suggests the MLL/ELL (MEN) fusion protein does not have a direct leukemogenic effect whereas the MLL/ENL (MLLT1) protein does [3,15]. The proband is described as an AML with recurrent genetic abnormalities under the World Health Organisation (WHO) classification [16] due to the presence of an 11q23 MLL gene rearrangement (Figure 2).…”

“…All patients with the t (11;19) share a common 11q23 (MLL gene) breakpoint, but two cytogenetically different 19p breakpoints have been observed, one at 19p13.1 (ELL gene) and the other at 19p13.3 (ENL gene) [3], although they may be indistinguishable when G-banding is less than 400 bands per haploid set (bph) [4]. The 19p13.1 ELL (eleven lysine-rich leukaemia) gene breakpoint is exclusive to AML patients, but generally occurs only in adult AMLs (over 40 years of age), whereas the 19p13.3 ENL (eleven nineteen leukaemia) gene breakpoint is thought to occur in younger patients affecting myeloid or lymphoid lineages [1,3,5], particularly in congenital myeloid cases [6].…”