Ablation of oncogenic ALK is a viable therapeutic approach for anaplastic large-cell lymphomas

Abstract

IntroductionAnaplastic large-cell lymphomas (ALCLs) represent a subset of neoplasms with distinctive genetic defects that are immunophenotypically characterized by the sustained expression of CD30. 1 In the late 1980s several groups described the unique association of the t(2;5)(p23;q35) chromosome translocation with ALCL. However, the corresponding genes were discovered several years later by Morris and colleagues. 2 In the t(2;5)(p23;q35) translocation the ALK (anaplastic lymphoma kinase) gene on chromosome 2 is fused to the NPM1 (nucleophosmin) gene on chromosome 5. Recently, several groups have successfully cloned many additional ALK translocations. 3 Translocations of ALK have also been discovered in inflammatory myofibroblastic tumors (IMTs), 4 and deregulated expression of ALK has been documented in a subgroup of diffuse large-cell lymphomas (DLCL). [5][6][7] Notably, the constitutive expression of the wild-type ALK receptor (ALK-R) has been shown in several cancer cell lines 8 and in primary neuroblastoma and rhabdomyosarcoma. 9,10 The ALK gene encodes a tyrosine kinase receptor whose physiologic expression in mammals is largely limited to neuronal cells. 11,12 At present, the physiologic role of ALK is still largely unclear. Nevertheless, ALK and its ligand play an important role in the formation of visceral muscle in Drosophila, 13,14 and in the regulation of neurologic synapses in Caenorhabditis elegans. 15 All ALK fusion proteins maintain the intracytoplasmic moiety of the ALK-R at their C terminus. This region, which contains the catalytic domain, is required for cellular transformation, 16 whereas the N-terminal fusion partners act as dimerizing domains. 17,18 Activated ALK chimeras bind multiple adaptor proteins such as Grb2, Shc, IRS-1, and p130Cas, which link them to diverse pathways regulating cell proliferation, survival, and cell transformation. Among them, PLC-␥, PI3K, and Jak3 lead to the activation of numerous downstream molecules including cyclin D, Erk1/2, STAT3, and AKT. 19,20 Using cell lineage-specific conditional knock-out models, we have recently demonstrated that the genetic ablation of STAT3 in ALK ϩ cells leads to T-and B-cell death, and prevents the generation of B-cell neoplasms. 21 Previously, PLC-␥ and AKT have been shown to play an essential role in ALK-mediated transformation, in vitro. 16,[22][23][24] Thus, it is conceivable that the inhibition of ALK could induce biologic changes capable of inhibiting cell growth and/or promoting cell death. This hypothesis is supported by a study in which a nonselective, but active drug against ALK was shown to successfully lead to tumor cell death. 25 Nonetheless, the specific down-modulation of NPM-ALK mRNA via siRNA does not induce apoptosis, despite a significant reduction in NPM-ALK protein. 26 Thus, the formal demonstration that the specific loss of ALK kinase activity has relevant biologic effects is still missing. Several kinase inhibitors were recently developed and successfully used in the treatment of human tumors. Systematic ...

Exon Array Profiling Detects EML4-ALK Fusion in Breast, Colorectal, and Non–Small Cell Lung Cancers

“…The presence of EML-ALK fusion in NSCLC was confirmed in a number of subsequent studies (14)(15)(16)(17)(18); however, it has not yet been detected in other carcinomas, including breast and colorectal (19,20). A number of EML4-ALK fusion variants have been identified up to date (12,18,(20)(21)(22)(23); all of them involve an almost identical portion of ALK (exons [20][21][22][23][24][25][26][27][28][29] The constitutive kinase activity of ALK is essential for proliferation of ALCL cells and its inactivation represents a feasible therapeutic approach for the treatment of ALCL (24). The intact ALK kinase domain within EML4-ALK possesses marked transforming as well as oncogenic activity in vitro and in vivo, respectively (12,21,25).…”

Functional validation of the anaplastic lymphoma kinase signature identifies CEBPB and Bcl2A1 as critical target genes

“…To analyze the effects of NPM-ALK expression in its native cellular background (ALCL), we used an inducible RNAi approach capable of silencing the expression of NPM-ALK fusion protein in ALK-positive cells. We have previously shown, using a constitutively expressed shRNA construct and small-molecule approach, that ALK expression is strictly required for the survival of ALK-positive ALCL cells in vitro and in vivo (11,12). Here, we have further exploited this tool to generate ALK-positive cell lines expressing a doxycycline-inducible ALK shRNA.…”

“…We have previously demonstrated that the constitutive expression and phosphorylation of NPM-ALK are sufficient for cellular transformation in vitro and for the development of lymphoid neoplasia in transgenic mice (10). Moreover, ALK activity is strictly required for the survival of ALCL cells in vitro and in vivo (11,12). However, the precise mechanisms by which NPM-ALK mediates cellular transformation and its requirements for tumor growth and survival are still unclear.…”

“…These studies confirm that combined approaches will ultimately disclose the pathogenetic networks in human cancers, paving the way for the discovery of new targets for alternative therapeutic strategies. ated ALK-knockdown and small-molecule approach, we recently demonstrated that ALK is required for the maintenance of the neoplastic phenotype of ALCL and represents a suitable target for specific pharmacological therapies (11,12). Here, we exploited an inducible RNAi method to unveil new ALK oncogenic pathways.…”

Leukocyte transmigration is modulated by chemokine‐mediated PI3Kγ‐dependent phosphorylation of vimentin

“…The three constructs were cloned (BamHI-SalI) in pCCL.sin.PPT.hPGK.GFPWpre (kindly provided by L. Naldini, San Raffaele Institute, Milan, Italy) replacing the GFP cassette. High titer lentiviral vector stock was produced in HEK-293T cells by Effectene cotransfection of the plasmid with the packaging vectors pMDLg/pRRE, pRSV-Rev and pMD2.VSVG [46]. Supernatants were collected and concentrated by ultracentrifugation.…”