Molecular detection of the (2;5) translocation of non-Hodgkin's lymphoma by reverse transcriptase-polymerase chain reaction

Abstract

The t(2;5)(p23;q35) translocation was initially identified in cases of anaplastic large-cell lymphoma (ALCL) that expressed the Ki-1 (CD30) antigen. We have recently cloned this translocation and shown it to encode a chimeric product consisting of the N-terminal portion of a nonribosomal nucleolar phosphoprotein, nucleophosmin (NPM), from chromosome 5, fused to the kinase domain of a novel transmembrane tyrosine-specific protein kinase, anaplastic lymphoma kinase (ALK), from chromosome 2. To better define the spectrum of lymphomas that contain this translocation, we have analyzed 70 cases of non-Hodgkin's lymphoma (NHL) for expression of the t(2;5)-derived NPM/ALK chimeric message by reverse transcriptase-polymerase chain reaction (RT-PCR). Using a previously described set of oligonucleotide primers, NPM/ALK chimeric transcripts were detected in 21 of 22 cases that contained the t(2;5) by cytogenetic analysis and in 10 of 48 cases that either lacked evidence of the t(2;5) or had unsuccessful cytogenetics. In all but 1 case, the NPM/ALK PCR products were of identical size and sequence, suggesting that the genomic chromosome breaks are clustered in a single intron in both NPM and ALK. The NPM/ALK-expressing cases were not confined to NHLs with anaplastic morphology and included 15 ALCLs, 6 immunoblastic lymphomas, and 10 diffuse large-cell lymphomas. Moreover, only slightly greater than half of the cases with anaplastic morphology and 59% of CD30-expressing cases were NPM/ALK positive. Thus, neither anaplastic morphology nor the expression of CD30 accurately predicted the presence of this molecular genetic subtype of lymphoma.

NPM/ALK gene fusion transcripts identify a distinct subgroup of null type Ki‐1 positive anaplastic large cell lymphomas

“…A recent study on 70 NHL cases included a undefined number of paediatric patients. Among 10 NHL cases of non-T/non-B phenotype including five ALCL, six expressed NPM/ALK (Downing et al, 1995). An association between this specific translocation and null-type childhood tumours has not previously been reported.…”

Detection of the t(2;5)‐associated NPM/ALK fusion cDNA in peripheral blood cells of healthy individuals

“…ALK protein expression in haemopoietic tissue has only been shown in cases where aberrant ALK gene expression was caused by the fusion to the npm (nucleophosmin) gene. The translocation has been detected by RT‐PCR and ALK‐protein expression in anaplastic large cell lymphoma (ALCL) of the T or null‐phenotype ( Wellmann et al , 1995 ; Herbst et al , 1995 ; Downing et al , 1995 ), in some cases of peripheral T‐cell lymphomas and B‐cell derived lymphomas ( Weisenburger et al , 1996 ) and in rare H&RS cells of a minority of cases with Hodgkin's disease ( Trümper et al , 1997a ). We show here that a significant percentage of apparently healthy volunteers carry NPM/ALK‐positive cells in the peripheral blood.…”

Alk+ CD30+ lymphomas: a distinct molecular genetic subtype of non‐hodgkin's lymphoma

“…Many CD30‐positive B‐cell tumours are non‐anaplastic (monomorphic, immunoblastic or hyperlobate) and most are EMA negative (Hamilton et al , 1999). Generally, less than 15% (range 0–25%) of B‐cell ALCLs are ALK positive, and as ALK‐positive B‐cell tumours tend to have a complex karyotype it has been suggested, although by no means proven, that ALK gene dysregulation may be a secondary event in an unstable genome rather than the initial pathogenic mutation in these tumours (Downing et al , 1995a; Lopategui et al , 1995; Arber et al , 1996; Weisenburger et al , 1996; Alsabeth et al , 1997; Hamilton et al , 1999; Haralambieva et al , 2000). For these reasons, CD30‐positive B‐cell lymphomas do not appear sufficiently distinct to warrant separation from other large B‐cell lymphomas at present, and the REAL and proposed WHO classifications have included B‐ALCLs with other diffuse large B‐cell NHLs.…”