Anaplastic lymphoma kinase and its signalling molecules as novel targets in lymphoma therapy

Discovery and antitumor activity of Benzo[d]imidazol-containing 2,4-diarylaminopyrimidine analogues as ALK inhibitors with mutation-combating effects

To address drug resistance caused by ALK kinase mutations, a series of novel 2,4-diarylaminopyrimidine (DAAP) analogues were designed by incorporating 1H-benzo[d]imidazol motif onto the maternal framework. All compounds were efficiently synthesized and antiproliferative activities against Karpas299, H2228 and A549 cell lines were evaluated by MTT assay. Delightly, the most promising derivative H-11 was detected with IC₅₀ values of 0.016 μM and 0.099 μM against ALK- positive Karpas299 and H2228 cells. Meanwhile, H-11 displayed encouraging enzymatic inhibitory potency with IC₅₀ values of 2.7 nM, 3.8 nM and 5.7 nM toward ALK^WT, ALK^L1196M and ALK^G1202R, respectively. Ultimately, the binding modes of optimal H-11 with ALK wild-type and mutants were ideally established which further confirmed the structural basis in accordance with the SARs analysis.

Structure-based optimization identified novel furyl-containing 2,4-diarylaminopyrimidine analogues as ALK/ROS1 dual inhibitors with anti-mutation effects

Aiming to develop ALK/ROS1 dual inhibitors overcoming ceritinib-resistant G1202R mutant, a dedicated structure-guided modification campaign was conducted based on ALK co-crystal structures. Twenty eight diarylaminopyrimidine (DAAP) analogues possessing furan or tetrahydrofuran group were designed and synthesized, among which compound 16 bearing (dimethylamino)methyl)furan-2-yl)methyl)thio fragment was identified. Compound 16 exhibited significant cytotoxicity on ALK-positive Karpas299 and H2228 cells with IC₅₀ values of 20 nM and 110 nM. Meanwhile, compound 16 turned out as the most potent entity superior to ceritinib with IC₅₀ values of 2.8, 2.6, 3.8 and 2.3 nM against ALK^WT, ALK^L1196M, ALK^G1202R and ROS1^WT, respectively. Subsequently, western blot assay showed that compound 16 significantly suppressed ALK and its downstream protein expression in a dose-dependent manner. Alternatively, the Hoechst 33258 and AO/EB staining assays illustrated that compound 16 could induce H2228 cell apoptosis. Ultimately, the binding models of compound 16 with ALK^WT, ALK^G1202R as well as ROS1 clearly presented the essential interactions within the active site. Together, compound 16 was validated as a promising ALK/ROS1 dual inhibitor for ALK^G1202R mutation correlated tumors.

The heterogeneous landscape of ALK negative ALCL

Anaplastic Large Cell Lymphoma (ALCL) is a clinical and biological heterogeneous disease including systemic ALK positive and ALK negative entities. Whereas ALK positive ALCLs are molecularly characterized and readily diagnosed, specific immunophenotypic or genetic features to define ALK negative ALCL are missing, and their distinction from other T-cell non-Hodgkin lymphomas (T-NHLs) can be controversial. In recent years, great advances have been made in dissecting the heterogeneity of ALK negative ALCLs and in providing new diagnostic and treatment options for these patients. A new revision of the World Health Organization (WHO) classification promoted ALK negative ALCL to a definite entity that includes cytogenetic subsets with prognostic implications. However, a further understanding of the genetic landscape of ALK negative ALCL is required to dictate more effective therapeutic strategies specifically tailored for each subgroup of patients.

Exploring Missense Mutations in Tyrosine Kinases Implicated with Neurodegeneration

Protein kinases are one of the largest families of evolutionarily related proteins and the third most common protein class of human genome. All the protein kinases share the same structural organization. They are made up of an extracellular domain, transmembrane domain and an intra cellular kinase domain. Missense mutations in these kinases have been studied extensively and correlated with various neurological disorders. Individual mutations in the kinase domain affect the functions of protein. The enhanced or reduced expression of protein leads to hyperactivation or inactivation of the signalling pathways, resulting in neurodegeneration. Here, we present extensive analyses of missense mutations in the tyrosine kinase focussing on the neurodegenerative diseases encompassing structure function relationship. This is envisaged to enhance our understanding about the neurodegeneration and possible therapeutic measures.

Oncogenic anaplastic lymphoma kinase (ALK) mutation in neuroblastomas and other pediatric tumors

Neuroblastoma (NB) is one of the most common malignant pediatric tumors that show aggressive behavior. Most advanced-stage NBs have proven refractory to many treatment modalities, and a fundamental alternative therapy, such as inhibition of biological pathways, is now being explored. Anaplastic lymphoma kinase (ALK) has recently been identified as an activation mutation in familial or high-risk sporadic NBs. We examined the prevalence of the ALK mutation in 54 NB cases (23 pre-treatment cases and 31 cases for which specimens were available before and after treatment) and the presence of the ALK mutation in various pediatric tumors. We detected the ALK mutation (F1174C and R1275Q) in 2 (3.7%) of the 54 NB specimens. Both cases showed poorly differentiated and advanced-stage NBs. No ALK mutations were detected in other pediatric tumors. The frequency of the ALK mutation was somewhat lower than that expected in Korean patients with NBs. The mutation detected in the present study was one of the hotspot mutations, including positions of F1174 and R1275 reported previously. The results of the present study suggest the possibility of potential roles of ALK inhibitors in the therapeutics of a small population of neuroblastoma carrying mutated ALK kinases.

Single-drug vinblastine as salvage treatment for refractory or relapsed anaplastic large-cell lymphoma: a report from the French Society of Pediatric Oncology

PURPOSE

To evaluate the efficacy of vinblastine for relapsed/refractory anaplastic large-cell lymphoma (ALCL).

PATIENTS AND METHODS

Data were reviewed on all 36 patients included prospectively in the French database for pediatric ALCL who were treated with vinblastine (6 mg/m(2)/wk) for resistant primary disease (one), a first relapse (15), or subsequent relapses (20). Fifteen patients had undergone hematopoietic stem-cell transplantation (HSCT) for a previous relapse.

RESULTS

Six patients were not evaluable for response, 25 (83%) of 30 evaluable patients achieved a complete remission (CR), and five experienced progressive disease. Among the 31 patients who achieved a CR with vinblastine or before its initiation, six patients were treated with HSCT and 25 with vinblastine alone (median duration, 14 months). Overall, nine of 25 patients treated with vinblastine alone have remained in CR (median, 7 years since the end of treatment), and 16 patients have relapsed. Vinblastine was still efficient for subsequent relapses. With a median follow-up of 9.2 years, 12 patients have died (four as a result of toxicity after HSCT and eight as a result of disease), and 24 patients are alive (15 following treatment with single-agent vinblastine for the last event). Five-year overall survival is 65% (95% CI, 48% to 79%), and 5-year event-free survival is 30% (95% CI, 17% to 47%).

CONCLUSION

Vinblastine is highly efficient in relapsed ALCL and may produce durable remissions. The optimal treatment duration still has to be assessed. These results should be borne in mind when designing future phase II studies with the targeted therapies directed against anaplastic lymphoma kinase.

Mutation-independent anaplastic lymphoma kinase overexpression in poor prognosis neuroblastoma patients

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase predominantly expressed in the developing nervous system. Recently, mutated ALK has been identified as a major oncogene associated with familial and sporadic neuroblastomas (NBL). Yet, a direct correlation between endogenous expression level of the ALK protein, oncogenic potential, and clinical outcome has not been established. We investigated ALK genetic mutations, protein expression/phosphorylation, and functional inhibition both in NBL-derived cell lines and in 34 localized and 48 advanced/metastatic NBL patients. ALK constitutive phosphorylation/activation was observed in high-ALK expressing cells, harboring either a mutated or a wild-type receptor. No activation was found in cell lines with low expression of wild-type ALK. After 72 hours of treatments, small molecule ALK inhibitor CEP-14083 (60 nmol/L) induced growth arrest and cell death in NBL cells overexpressing wild-type (viability: ALK(high) 12.8%, ALK(low) 73%, P = 0.0035; cell death: ALK(high) 56.4%, ALK(low) 16.2%, P = 0.0001) or mutated ALK. ALK protein expression was significantly up-regulated in advanced/metastatic compared with localized NBLs (ALK overexpressing patients: stage 1-2, 23.5%; stage 3-4, 77%; P < 0.0001). Interestingly, protein levels did not always correlate with ALK genetic alterations and/or mRNA abundance. Both mutated and wild-type ALK receptor can exert oncogenic activity in NBL cells. However, wild-type ALK receptor requires a critical threshold of expression to achieve oncogenic activation. Overexpression of either mutated or wild-type ALK defines poor prognosis patients. Alternative mechanisms other than direct mutations and/or gene amplification regulate the ALK level of expression in NBL cells. Wild-type ALK is a potential therapeutic target for advanced/metastatic NBLs.

Chromosomal translocations in cancer

Genetic alterations in DNA can lead to cancer when it is present in proto-oncogenes, tumor suppressor genes, DNA repair genes etc. Examples of such alterations include deletions, inversions and chromosomal translocations. Among these rearrangements chromosomal translocations are considered as the primary cause for many cancers including lymphoma, leukemia and some solid tumors. Chromosomal translocations in certain cases can result either in the fusion of genes or in bringing genes close to enhancer or promoter elements, hence leading to their altered expression. Moreover, chromosomal translocations are used as diagnostic markers for cancer and its therapeutics. In the first part of this review, we summarize the well-studied chromosomal translocations in cancer. Although the mechanism of formation of most of these translocations is still unclear, in the second part we discuss the recent advances in this area of research.

Development of anaplastic lymphoma kinase (ALK) small-molecule inhibitors for cancer therapy

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) involved in the genesis of several human cancers; indeed, ALK was initially identified in constitutively activated and oncogenic fusion forms--the most common being nucleophosmin (NPM)-ALK--in a non-Hodgkin's lymphoma (NHL) known as anaplastic large-cell lymphoma (ALCL) and subsequent studies identified ALK fusions in the human sarcomas called inflammatory myofibroblastic tumors (IMTs). In addition, two recent reports have suggested that the ALK fusion, TPM4-ALK, may be involved in the genesis of a subset of esophageal squamous cell carcinomas. While the cause-effect relationship between ALK fusions and malignancies such as ALCL and IMT is very well established, more circumstantial links implicate the involvement of the full-length, normal ALK receptor in the genesis of additional malignancies including glioblastoma, neuroblastoma, breast cancer, and others; in these instances, ALK is believed to foster tumorigenesis following activation by autocrine and/or paracrine growth loops involving the reported ALK ligands, pleiotrophin (PTN) and midkine (MK). There are no currently available ALK small-molecule inhibitors approved for clinical cancer therapy; however, recognition of the variety of malignancies in which ALK may play a causative role has recently begun to prompt developmental efforts in this area. This review provides a succinct summary of normal ALK biology, the confirmed and putative roles of ALK fusions and the full-length ALK receptor in the development of human cancers, and efforts to target ALK using small-molecule kinase inhibitors.

Behavioral and neurochemical alterations in mice deficient in anaplastic lymphoma kinase suggest therapeutic potential for psychiatric indications

The receptor tyrosine kinase product of the anaplastic lymphoma kinase (ALK) gene has been implicated in oncogenesis as a product of several chromosomal translocations, although its endogeneous role in the hematopoietic and neural systems has remained poorly understood. We describe that the generation of animals homozygous for a deletion of the ALK tyrosine kinase domain leads to alterations in adult brain function. Evaluation of adult ALK homozygotes (HOs) revealed an age-dependent increase in basal hippocampal progenitor proliferation and alterations in behavioral tests consistent with a role for this receptor in the adult brain. ALK HO animals displayed an increased struggle time in the tail suspension test and the Porsolt swim test and enhanced performance in a novel object-recognition test. Neurochemical analysis demonstrates an increase in basal dopaminergic signalling selectively within the frontal cortex. Altogether, these results suggest that ALK functions in the adult brain to regulate the function of the frontal cortex and hippocampus and identifies ALK as a new target for psychiatric indications, such as schizophrenia and depression, with an underlying deregulated monoaminergic signalling.

Characterization of some molecular mechanisms governing autoactivation of the catalytic domain of the anaplastic lymphoma kinase

NPM/ALK is an oncogenic fusion protein expressed in approximately 50% of anaplastic large cell lymphoma cases. It derives from the t(2;5)(p23;q35) chromosomal translocation that fuses the catalytic domain of the tyrosine kinase, anaplastic lymphoma kinase (ALK), with the dimerization domain of the ubiquitously expressed nucleophosmin (NPM) protein. Dimerization of the ALK kinase domain leads to its autophosphorylation and constitutive activation. Activated NPM/ALK stimulates downstream survival and proliferation signaling pathways leading to malignant transformation. Herein, we investigated the molecular mechanisms of autoactivation of the catalytic domain of ALK. Because kinases are typically regulated by autophosphorylation of their activation loops, we systematically mutated (Tyr --> Phe) three potential autophosphorylation sites contained in the "YXXXYY" motif of the ALK activation loop, and determined the effect of these mutations on the catalytic activity and biological function of NPM/ALK. We observed that mutation of both the second and third tyrosine residues (YFF mutant) did not affect the kinase activity or transforming ability of NPM/ALK. In contrast, mutation of the first and second (FFY), first and third (FYF), or all three (FFF) tyrosine residues impaired both kinase activity and transforming ability of NPM/ALK. Furthermore, a DFF mutant, in which the aspartic residue introduces a negative charge similar to a phosphorylated tyrosine, possessed catalytic activity similar to the YFF mutant. Together, our findings indicate that phosphorylation of the first tyrosine of the YXXXYY motif is necessary for the autoactivation of the ALK kinase domain and the transforming activity of NPM/ALK.

NPM/ALK binds and phosphorylates the RNA/DNA-binding protein PSF in anaplastic large-cell lymphoma

The oncogenic fusion tyrosine kinase nucleophosmin/anaplastic lymphoma kinase (NPM/ALK) induces cellular transformation in anaplastic large-cell lymphomas (ALCLs) carrying the t(2;5) chromosomal translocation. Protein-protein interactions involving NPM/ALK are important for the activation of downstream signaling pathways. This study was aimed at identifying novel NPM/ALK-binding proteins that might contribute to its oncogenic transformation. Using a proteomic approach, several RNA/DNA-binding proteins were found to coimmunoprecipitate with NPM/ALK, including the multifunctional polypyrimidine tract binding proteinassociated splicing factor (PSF). The interaction between NPM/ALK and PSF was dependent on an active ALK kinase domain and PSF was found to be tyrosine-phosphorylated in NPM/ALK-expressing cell lines and in primary ALK(+) ALCL samples. Furthermore, PSF was shown to be a direct substrate of purified ALK kinase domain in vitro, and PSF Tyr293 was identified as the site of phosphorylation. Y293F PSF was not phosphorylated by NPM/ALK and was not delocalized in NPM/ALK(+) cells. The expression of ALK fusion proteins induced delocalization of PSF from the nucleus to the cytoplasm and forced overexpression of PSF-inhibited proliferation and induced apoptosis in cells expressing NPM/ALK. PSF phosphorylation also increased its binding to RNA and decreased the PSF-mediated suppression of GAGE6 expression. These results identify PSF as a novel NPM/ALK-binding protein and substrate, and suggest that PSF function may be perturbed in NPM/ALK-transformed cells.

Identification of NVP-TAE684, a potent, selective, and efficacious inhibitor of NPM-ALK

Constitutive overexpression and activation of NPM-ALK fusion protein [t(2:5)(p23;q35)] is a key oncogenic event that drives the survival and proliferation of anaplastic large-cell lymphomas (ALCLs). We have identified a highly potent and selective small-molecule ALK inhibitor, NVP-TAE684, which blocked the growth of ALCL-derived and ALK-dependent cell lines with IC(50) values between 2 and 10 nM. NVP-TAE684 treatment resulted in a rapid and sustained inhibition of phosphorylation of NPM-ALK and its downstream effectors and subsequent induction of apoptosis and cell cycle arrest. In vivo, NVP-TAE684 suppressed lymphomagenesis in two independent models of ALK-positive ALCL and induced regression of established Karpas-299 lymphomas. NVP-TAE684 also induced down-regulation of CD30 expression, suggesting that CD30 may be used as a biomarker of therapeutic NPM-ALK kinase activity inhibition.

Structural insights into the ATP binding pocket of the anaplastic lymphoma kinase by site-directed mutagenesis, inhibitor binding analysis, and homology modeling

Anaplastic lymphoma kinase (ALK) is a valid target for anticancer therapy; however, potent ALK inhibitors suitable for clinical use are lacking. Because the majority of described kinase inhibitors bind in the ATP pocket of the kinase domain, we have characterized this pocket in ALK using site-directed mutagenesis, inhibition studies, and molecular modeling. Mutation of the gatekeeper residue, a key structural determinant influencing inhibitor binding, rendered the fusion protein, NPM/ALK, sensitive to inhibition by SKI-606 in the nanomolar range, while PD173955 inhibited the NPM/ALK mutant at micromolar concentrations. In contrast, both wild type and mutant NPM/ALK were insensitive to imatinib. Computer modeling indicated that docking solutions obtained with a homology model representing the intermediate conformation of the ALK kinase domain reflected closely experimental data. The good agreement between experimental and virtual results indicate that the ALK molecular models described here are useful tools for the rational design of ALK selective inhibitors. In addition, 4-phenylamino-quinoline compounds may have potential as templates for ALK inhibitors.