With the use of microarray gene-expression profiling, we analyzed a homogeneous series of 32 patients with systemic anaplastic large-cell lymphoma (ALCL) and 5 ALCL cell lines. Unsupervised analysis classified ALCL in 2 clusters, corresponding essentially to morphologic subgroups (ie, common type vs small cell and "mixed" variants) and clinical variables. Patients with a morphologic variant of ALCL had advanced-stage disease. This group included a significant number of patients who experienced early relapse. Supervised analysis showed that ALK+ALCL and ALK- ALCL have different gene-expression profiles, further confirming that they are different entities. Among the most significantly differentially expressed genes between ALK+ and ALK- samples, we found BCL6, PTPN12, CEBPB, and SERPINA1 genes to be overexpressed in ALK+ ALCL. This result was confirmed at the protein level for BCL-6, C/EBPbeta and serpinA1 through tissue microarrays. The molecular signature of ALK- ALCL included overexpression of CCR7, CNTFR, IL22, and IL21 genes but did not provide any obvious clues to the molecular mechanism underlying this tumor subtype. Once confirmed on a larger number of patients, the results of the present study could be used for clinical and therapeutic management of patients at the time of diagnosis.

Majority of anaplastic large-cell lymphomas (ALCLs) are associated with the t(2;5)(p23;q35) translocation, fusing the NPM (nucleophosmin) and ALK (anaplastic lymphoma kinase) genes (NPM-ALK). Recent studies demonstrated that ALK may also be involved in variant translocations, namely, t(1;2)(q25;p23), t(2;3)(p23;q21), t(2;17)(p23;q23) and inv(2)(p23q35), which create the TPM3-ALK, TFG-ALK5, CLTC-ALK, and ATIC-ALK fusion genes, respectively. Although overexpression of NPM-ALK has previously been shown to transform fibroblasts, the transforming potential of variant X-ALK proteins has not been precisely investigated. We stably transfected the cDNAs coding for NPM-ALK, TPM3-ALK, TFG-ALK, CLTC-ALK or ATIC-ALK into nonmalignant NIH3T3 cells. All X-ALK variants are tyrosine phosphorylated and their subcellular distribution was in agreement with that observed in tumors. Moreover, our results show that the in vitro transforming capacity of NIH3T3-transfected cells are in relation to the level of X-ALK fusion proteins excepted for TPM3-ALK for which there is an inverse correlation. The differences between the five X-ALK variants with regard to proliferation rate, colony formation in soft agar, invasion, migration through the endothelial barrier and tumorigenicity seem to be due to differential activation of various signaling pathways such as PI3-kinase/AKT. These findings may have clinical implications in the pathogenesis and prognosis of ALKpositive ALCLs.