Anaplastic large-cell lymphoma (ALCL) was initially recognized on the basis of morphologic features and the consistent expression of CD30. It then became evident that the majority of these tumors are derived from lymphoid cells of T or null immunophenotype. The subsequent finding that t(2;5)(p23;q35) occurs in 40% to 60% of ALCL patients established a distinct clinicopathologic entity. This chromosomal translocation induces the formation of the chimeric protein nucleophosmin–anaplastic lymphoma kinase (NPM-ALK), which possesses significant oncogenic potential resulting from the constitutive activation of the tyrosine kinase ALK. In addition to its specific pathophysiologic events, NPM-ALK–expressing lymphoma presents with consistent clinical manifestations. Only 13 years after the identification of NPM-ALK, tremendous progress has been made in our understanding of this molecule because of the relentless efforts of multiple investigators who have dissected its biologic roles using in vitro and in vivo experimental models. Several upstream modulators, cross-reacting oncogenes, and downstream effectors of NPM-ALK have been identified and characterized. Understanding these interacting oncogenic systems is expected to facilitate the design of new therapeutic strategies and agents. In this review, we briefly discuss ALCL and focus on NPM-ALK.

Anaplastic large cell lymphoma (ALCL) is a highly proliferative neoplasm that frequently carries the t(2;5)(p23;q35) and aberrantly expresses nucleophosmin–anaplastic lymphoma kinase (NPM-ALK). Previously, NPM-ALK had been shown to activate the phosphatidylinositol 3 kinase (PI3K)/Akt pathway. As the cyclin-dependent kinase (CDK) inhibitor p27Kip1 (p27) is usually not expressed in ALCL, we hypothesized that activated Akt (pAkt) phosphorylates p27 resulting in increased p27 proteolysis and cell cycle progression. Here we demonstrate that inhibition of pAkt activity in ALCL decreases p27 phosphorylation and degradation, resulting in increased p27 levels and cell cycle arrest. Using immunohistochemistry, pAkt was detected in 24 (57%) of 42 ALCL tumors, including 8 (44%) of 18 ALK-positive tumors and 16 (67%) of 24 ALK-negative tumors, and was inversely correlated with p27 levels. The mean percentage of p27-positive tumor cells was 5% in the pAkt-positive group compared with 26% in the pAkt-negative group (P = .0076). These findings implicate that Akt activation promotes cell cycle progression through inactivation of p27 in ALCL.

The aberrant fusion protein NPM-ALK plays an important pathogenetic role in ALK⁺ anaplastic large-cell lymphoma (ALCL). We previously demonstrated that Jak3 potentiates the activity of NPM-ALK. Jak3 activation is restricted to interleukins that recruit the common γ chain (γc) receptor, including IL-9. NPM-ALK was previously shown to promote widespread lymphomas in IL-9 transgenic mice by unknown mechanisms. We hypothesized that IL-9 plays an important role in ALK⁺ ALCL via Jak3 activation. Our studies demonstrate the expression of IL-9Rα and IL-9 in 3 ALK⁺ ALCL-cell lines and 75% and 83% of primary tumors, respectively. IL-9 was detected in serum-free culture medium harvested from ALK⁺ ALCL-cell lines, supporting autocrine release of IL-9. Treatment of these cells with an anti–IL-9–neutralizing antibody decreased pJak3 and its kinase activity, along with pStat3 and ALK kinase activity. These effects were associated with decreased cell proliferation and colony formation in soft agar and cell-cycle arrest. Evidence suggests that cell-cycle arrest can be attributed to up-regulation of p21 and down-regulation of Pim-1. Our results illustrate that IL-9/Jak3 signaling plays a significant role in the pathogenesis of ALK⁺ ALCL and that it represents a potential therapeutic target for treating patients with ALK⁺ ALCL.

Mantle cell lymphoma (MCL) is a distinct type of B-cell non-Hodgkin lymphoma characterized by t(11;14)(q13;q32) and cyclin D1 overexpression. The pathogenesis of MCL has not been comprehensively studied, which can be attributed in part to the paucity of well-characterized MCL cell lines. We collected 4 previously developed MCL cell lines and performed extensive characterization, including the susceptibly of these cell lines to transduction by adenovirus vectors. Our aim was to facilitate the establishment of an in vitro model that can be reliably used to study the pathogenesis of MCL. Standard techniques were used to compare the morphologic, immunophenotypic, and cytogenetic features of the 4 cell lines. In addition, Western blotting was used to investigate the presence of several cell cycle- and apoptosis-related proteins. TP53 DNA sequencing was also performed on the cell lines. The adenoviral transduction efficiency was assessed using an adenoviral vector carrying the gene encoding for the green fluorescence protein (Ad-GFP). All cell lines demonstrated evidence of t(11;14)(q13;q32) and overexpression of cyclin D1. Cyclin D2 was not detectable in all cell lines, whereas cyclin D3 was weakly expressed in JeKo-1 and SP-53. Other abnormalities of the cell cycle G1 phase regulatory pathway were detected, including loss of expression of p53 (JeKo-1) and p16(INK4a) (SP-53 and Granta 519), as well as TP53 mutation (Mino). All cell lines express high levels of cyclin E, c-Myc, Bcl-2, Bax, Bcl-x(L), and Mcl-1. Retinoblastoma protein is hyperphosphorylated in all cell lines. With the exception of Mino, MCL cell lines are highly transducible with adenoviral vectors. These cell lines are representative of MCL and can be used as an in vitro model to further explore the pathogenesis of this disease. The susceptibility of these cell lines to gene transfer provides opportunities to evaluate the importance of various oncogenes and tumor suppressor genes that may have an impact on developing effective therapeutic regimens for MCL.

Type I insulin-like growth factor receptor signaling in hematological malignancies