Tyrosine phosphatases regulate resistance to ALK inhibitors in ALK+ anaplastic large cell lymphoma

ALK in cancer: from function to therapeutic targeting

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) that acts as an oncogenic driver in solid and haematological malignancies in both children and adults. Although ALK-expressing (ALK+) tumours show strong initial responses to the series of ALK inhibitors currently available, many patients will develop resistance. In this Review, we discuss recent advances in ALK oncogenic signalling, together with existing and promising new modalities to treat ALK-driven tumours, including currently approved ALK-directed therapies, namely tyrosine kinase inhibitors, and novel approaches such as ALK-specific immune therapies. Although ALK inhibitors have changed the management and clinical history of ALK+ tumours, they are still insufficient to cure most of the patients. Therefore, more effort is needed to further improve outcomes and prevent the tumour resistance, recurrence and metastatic spread that many patients with ALK+ tumours experience. Here, we outline how a multipronged approach directed against ALK and other essential pathways that sustain the persistence of ALK+ tumours, together with potent or specific immunotherapies, could achieve this goal. We envision that the lessons learned from treating ALK+ tumours in the clinic could ultimately accelerate the implementation of innovative combination therapies to treat tumours driven by other tyrosine kinases or oncogenes with similar properties.

HDAC1 acts as a tumor suppressor in ALK-positive anaplastic large cell lymphoma: implications for HDAC inhibitor therapy

Histone deacetylases (HDACs) are frequently deregulated in cancer, and several HDAC inhibitors (HDACi) have gained approval for treating peripheral T cell lymphomas. Here, we investigated the effects of pharmacological or genetic HDAC inhibition on NPM::ALK positive anaplastic large cell lymphoma (ALCL) development to assess the potential use of HDACi for the treatment of this disease. Short-term systemic pharmacological inhibition of HDACs using the HDACi Entinostat in a premalignant ALCL mouse model postponed or even abolished lymphoma development, despite high expression of the NPM::ALK fusion oncogene. To further disentangle the effects of systemic HDAC inhibition from thymocyte intrinsic effects, conditional genetic deletions of HDAC1 and HDAC2 enzymes were employed. In sharp contrast, T cell-specific deletion of Hdac1 or Hdac2 in the ALCL mouse model significantly accelerated NPM::ALK-driven lymphomagenesis, with Hdac1 loss having a more pronounced effect. Integration of gene expression and chromatin accessibility data revealed that Hdac1 deletion selectively perturbed cell type-specific transcriptional programs, crucial for T cell differentiation and signaling. Moreover, multiple oncogenic signaling pathways, including PDGFRB signaling, were highly upregulated. Our findings underscore the tumor-suppressive function of HDAC1 and HDAC2 in T cells during ALCL development. Nevertheless, systemic pharmacological inhibition of HDACs could still potentially improve current therapeutic outcomes.

Case report: Musculoskeletal metastastic inflammatory myofibroblastic tumor (IMT) treated by sequential ALK-TKI with longterm response

Inflammatory myofibroblastic tumors (IMTs) are known to be associated with rearrangements of the anaplastic lymphoma kinase (ALK) gene. The treatment of this type of tumor includes systemic therapies such as chemotherapies or anti-inflammatories; in recent years, targeted anti-ALK therapies have emerged and became the standard of care in ALK rearranged patients. We aimed to present a rare case of musculoskeletal IMT with ALK rearrangement, characterized by metastatic evolution and enhanced responses to sequential treatment with all ALK-TKI. We have outlined a potential treatment pathway involving sequential ALK-TKI targeted therapies and successive local interventions to control the cancer.

Targeting ERBB3 and AKT to overcome adaptive resistance in EML4-ALK-driven non-small cell lung cancer

The fusion event between EML4 and ALK drives a significant oncogenic activity in 5% of non-small cell lung cancer (NSCLC). Even though potent ALK-tyrosine kinase inhibitors (ALK-TKIs) are successfully used for the treatment of EML4-ALK-positive NSCLC patients, a subset of those patients eventually acquire resistance during their therapy. Here, we investigate the kinase responses in EML4-ALK V1 and V3-harbouring NSCLC cancer cells after acute inhibition with ALK TKI, lorlatinib (LOR). Using phosphopeptide chip array and upstream kinase prediction analysis, we identified a group of phosphorylated tyrosine peptides including ERBB and AKT proteins that are upregulated upon ALK-TKI treatment in EML4-ALK-positive NSCLC cell lines. Dual inhibition of ALK and ERBB receptors or AKT disrupts RAS/MAPK and AKT/PI3K signalling pathways, and enhances apoptosis in EML4-ALK + NSCLC cancer cells. Heregulin, an ERBB3 ligand, differentially modulates the sensitivity of EML4-ALK cell lines to ALK inhibitors. We found that EML4-ALK cells made resistant to LOR are sensitive to inhibition of ERBB and AKT. These findings emphasize the important roles of AKT and ERBB3 to regulate signalling after acute LOR treatment, identifying them as potential targets that may be beneficial to prevent adaptive resistance to EML4-ALK-targeted therapies in NSCLC.

Anaplastic Lymphoma Kinase (ALK) Inhibitors Enhance Phagocytosis Induced by CD47 Blockade in Sensitive and Resistant ALK-Driven Malignancies

BACKGROUND

Anaplastic lymphoma kinase (ALK) plays a role in the development of lymphoma, lung cancer and neuroblastoma. While tyrosine kinase inhibitors (TKIs) have improved treatment outcomes, relapse remains a challenge due to on-target mutations and off-target resistance mechanisms. ALK-positive (ALK+) tumors can evade the immune system, partly through tumor-associated macrophages (TAMs) that facilitate immune escape. Cancer cells use "don't eat me" signals (DEMs), such as CD47, to resist TAMs-mediated phagocytosis. TKIs may upregulate pro-phagocytic stimuli (i.e., calreticulin, CALR), suggesting a potential therapeutic benefit in combining TKIs with an anti-CD47 monoclonal antibody (mAb). However, the impact of this combination on both TKIs-sensitive and resistant ALK+ tumors requires further investigation.

METHODS

A panel of TKIs-sensitive and resistant ALK+ cancer subtypes was assessed for CALR and CD47 expression over time using flow cytometry. Flow cytometry co-culture and fluorescent microscopy assays were employed to evaluate phagocytosis under various treatment conditions.

RESULTS

ALK inhibitors increased CALR expression in both TKIs-sensitive and off-target resistant ALK+ cancer cells. Prolonged TKIs exposure also led to CD47 upregulation. The combination of ALK inhibitors and anti-CD47 mAb significantly enhanced phagocytosis compared to anti-CD47 alone, as confirmed by flow cytometry and fluorescent microscopy.

CONCLUSIONS

Anti-CD47 mAb can quench DEMs while exposing pro-phagocytic signals, promoting tumor cell phagocytosis. ALK inhibitors induced immunogenic cell damage by upregulating CALR in both sensitive and off-target resistant tumors. Continuous TKIs exposure in off-target resistant settings also resulted in the upregulation of CD47 over time. Combining TKIs with a CD47 blockade may offer therapeutic benefits in ALK+ cancers, especially in overcoming off-target resistance where TKIs alone are less effective.

Recurrent somatic mutations of FAT family cadherins induce an aggressive phenotype and poor prognosis in anaplastic large cell lymphoma

BACKGROUND

Anaplastic Large Cell Lymphoma (ALCL) is a rare and aggressive T-cell lymphoma, classified into ALK-positive and ALK-negative subtypes, based on the presence of chromosomal translocations involving the ALK gene. The current standard of treatment for ALCL is polychemotherapy, with a high overall survival rate. However, a subset of patients does not respond to or develops resistance to these therapies, posing a serious challenge for clinicians. Recent targeted treatments such as ALK kinase inhibitors and anti-CD30 antibody-drug conjugates have shown promise but, for a fraction of patients, the prognosis is still unsatisfactory.

METHODS

We investigated the genetic landscape of ALK + ALCL by whole-exome sequencing; recurring mutations were characterized in vitro and in vivo using transduced ALCL cellular models.

RESULTS

Recurrent mutations in FAT family genes and the transcription factor RUNX1T1 were found. These mutations induced changes in ALCL cells morphology, growth, and migration, shedding light on potential factors contributing to treatment resistance. In particular, FAT4 silencing in ALCL cells activated the β-catenin and YAP1 pathways, which play crucial roles in tumor growth, and conferred resistance to chemotherapy. Furthermore, STAT1 and STAT3 were hyper-activated in these cells. Gene expression profiling showed global changes in pathways related to cell adhesion, cytoskeletal organization, and oncogenic signaling. Notably, FAT mutations associated with poor outcome in patients.

CONCLUSIONS

These findings provide novel insights into the molecular portrait of ALCL, that could help improve treatment strategies and the prognosis for ALCL patients.

Identification of APBB1 as a substrate for anaplastic lymphoma kinase

Anaplastic lymphoma kinase (ALK) is a well-known oncogene involved in various malignancies such as anaplastic large cell lymphoma, lung cancer and neuroblastoma. Several substrates for fused ALK have been identified and their biological functions have been described. However, the lack of a comprehensive identification of ALK substrates limits our understanding of the biological roles of receptor ALK. Thus, this study aimed to identify novel ALK substrates and characterize their biological functions. We screened the interactors of the kinase domain of receptor ALK using proximity-dependent biotin identification and identified 43 interactors. We narrowed down the candidates by evaluating whether these interactors were downstream of ALK in a neuroblastoma cell line, NB-1. Amongst these, we identified amyloid beta precursor protein-binding family B member 1 (APBB1) as an ALK downstream molecule involved in NB-1 cell viability. Finally, we assessed the kinase-substrate relationship between ALK and APBB1 and found that ALK phosphorylated multiple tyrosine residues in APBB1 both in-cell and in-tube assays, with tyrosine 269 as a major target. In conclusion, we successfully identified a new substrate for receptor ALK. Our results may help further elucidate the molecular mechanism of ALK downstream signalling in neuroblastoma.

Targeting undruggable phosphatase overcomes trastuzumab resistance by inhibiting multi-oncogenic kinases

AIMS

Resistance to targeted therapy is one of the critical obstacles in cancer management. Resistance to trastuzumab frequently develops in the treatment for HER2+ cancers. The role of protein tyrosine phosphatases (PTPs) in trastuzumab resistance is not well understood. In this study, we aim to identify pivotal PTPs affecting trastuzumab resistance and devise a novel counteracting strategy.

METHODS

Four public datasets were used to screen PTP candidates in relation to trastuzumab responsiveness in HER2+ breast cancer. Tyrosine kinase (TK) arrays were used to identify kinases that linked to protein tyrosine phosphate receptor type O (PTPRO)-enhanced trastuzumab sensitivity. The efficacy of small activating RNA (saRNA) in trastuzumab-conjugated silica nanoparticles was tested for PTPRO upregulation and resistance mitigation in cell models, a transgenic mouse model, and human cancer cell line-derived xenograft models.

RESULTS

PTPRO was identified as the key PTP which influences trastuzumab responsiveness and patient survival. PTPRO de-phosphorated several TKs, including the previously overlooked substrate ERBB3, thereby inhibiting multiple oncogenic pathways associated with drug resistance. Notably, PTPRO, previously deemed "undruggable," was effectively upregulated by saRNA-loaded nanoparticles. The upregulated PTPRO simultaneously inhibited ERBB3, ERBB2, and downstream SRC signaling pathways, thereby counteracting trastuzumab resistance.

CONCLUSIONS

Antibody-conjugated saRNA represents an innovative approach for targeting "undruggable" PTPs.

GeneRaMeN enables integration, comparison, and meta-analysis of multiple ranked gene lists to identify consensus, unique, and correlated genes

High-throughput experiments often produce ranked gene outputs, with forward genetic screening being a notable example. While there are various tools for analyzing individual datasets, those that perform comparative and meta-analytical examination of such ranked gene lists remain scarce. Here, we introduce Gene Rank Meta Analyzer (GeneRaMeN), an R Shiny tool utilizing rank statistics to facilitate the identification of consensus, unique, and correlated genes across multiple hit lists. We focused on two key topics to showcase GeneRaMeN: virus host factors and cancer dependencies. Using GeneRaMeN 'Rank Aggregation', we integrated 24 published and new flavivirus genetic screening datasets, including dengue, Japanese encephalitis, and Zika viruses. This meta-analysis yielded a consensus list of flavivirus host factors, elucidating the significant influence of cell line selection on screening outcomes. Similar analysis on 13 SARS-CoV-2 CRISPR screening datasets highlighted the pivotal role of meta-analysis in revealing redundant biological pathways exploited by the virus to enter human cells. Such redundancy was further underscored using GeneRaMeN's 'Rank Correlation', where a strong negative correlation was observed for host factors implicated in one entry pathway versus the alternate route. Utilizing GeneRaMeN's 'Rank Uniqueness', we analyzed human coronaviruses 229E, OC43, and SARS-CoV-2 datasets, identifying host factors uniquely associated with a defined subset of the screening datasets. Similar analyses were performed on over 1000 Cancer Dependency Map (DepMap) datasets spanning 19 human cancer types to reveal unique cancer vulnerabilities for each organ/tissue. GeneRaMeN, an efficient tool to integrate and maximize the usability of genetic screening datasets, is freely accessible via https://ysolab.shinyapps.io/GeneRaMeN.

From Tyrosine Kinases to Tyrosine Phosphatases: New Therapeutic Targets in Cancers and Beyond

Protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs) regulate the level of tyrosine phosphorylation in proteins. PTKs are key enzymes that catalyze the transfer of an ATP phosphoric acid to a tyrosine residue on target protein substrates. Protein tyrosine phosphatases (PTPs) are responsible for the dephosphorylation of tyrosine residues and play a role in countering PTK overactivity. As widespread oncogenes, PTKs were once considered to be promising targets for therapy. However, tyrosine kinase inhibitors (TKIs) now face a number of challenges, including drug resistance and toxic side effects. Treatment strategies now need to be developed from a new perspective. In this review, we assess the current state of TKIs and highlight the role of PTPs in cancer and other diseases. With the advances of allosteric inhibition and the development of multiple alternative proprietary drug strategies, the reputation of PTPs as "undruggable" targets has been overturned, and they are now considered viable therapeutic targets. We also discuss the strategies and prospects of PTP-targeted therapy, as well as its future development.

STAT3 couples activated tyrosine kinase signaling to the oncogenic core transcriptional regulatory circuitry of anaplastic large cell lymphoma

Anaplastic large cell lymphoma (ALCL) is an aggressive, CD30+ T cell lymphoma of children and adults. ALK fusion transcripts or mutations in the JAK-STAT pathway are observed in most ALCL tumors, but the mechanisms underlying tumorigenesis are not fully understood. Here, we show that dysregulated STAT3 in ALCL cooccupies enhancers with master transcription factors BATF3, IRF4, and IKZF1 to form a core regulatory circuit that establishes and maintains the malignant cell state in ALCL. Critical downstream targets of this network in ALCL cells include the protooncogene MYC, which requires active STAT3 to facilitate high levels of MYC transcription. The core autoregulatory transcriptional circuitry activity is reinforced by MYC binding to the enhancer regions associated with STAT3 and each of the core regulatory transcription factors. Thus, activation of STAT3 provides the crucial link between aberrant tyrosine kinase signaling and the core transcriptional machinery that drives tumorigenesis and creates therapeutic vulnerabilities in ALCL.

Targeting Protein Tyrosine Phosphatases to Improve Cancer Immunotherapies

Advances in immunotherapy have brought significant therapeutic benefits to many cancer patients. Nonetheless, many cancer types are refractory to current immunotherapeutic approaches, meaning that further targets are required to increase the number of patients who benefit from these technologies. Protein tyrosine phosphatases (PTPs) have long been recognised to play a vital role in the regulation of cancer cell biology and the immune response. In this review, we summarize the evidence for both the pro-tumorigenic and tumour-suppressor function of non-receptor PTPs in cancer cells and discuss recent data showing that several of these enzymes act as intracellular immune checkpoints that suppress effective tumour immunity. We highlight new data showing that the deletion of inhibitory PTPs is a rational approach to improve the outcomes of adoptive T cell-based cancer immunotherapies and describe recent progress in the development of PTP inhibitors as anti-cancer drugs.

Dependence of peripheral T-cell lymphoma on constitutively activated JAK3: Implication for JAK3 inhibition as a therapeutic approach

Peripheral T-cell lymphoma (PTCL) is a clinically heterogeneous group that represents 10%-15% of all lymphomas. Despite improved genetic and molecular understanding, treatment outcomes for PTCL have not shown significant improvement. Although Janus kinase-2 (JAK2) plays an important role in myeloproliferative neoplasms, the critical role of JAK isoforms in mediating prosurvival signaling in PTCL cells is not well defined. Immunohistochemical analysis of PTCL tumors (n = 96) revealed high levels of constitutively active JAK3 (pJAK3) that significantly (p < 0.04) correlated with the activation state of its canonical substrate STAT3. Furthermore, constitutive activation of JAK3 and STAT3 positively correlated, at least in part, with an oncogenic tyrosine phosphatase PTPN11. Pharmacological inhibition of JAK3 but not JAK1/JAK2 significantly (p < 0.001) decreased PTCL proliferation, survival and STAT3 activation. A sharp contrast was observed in the pJAK3 positivity between ALK+ (85.7%) versus ALK-negative (10.0%) in human PTCL tumors and PTCL cell lines. Moreover, JAK3 and ALK reciprocally interacted in PTCL cells, forming a complex to possibly regulate STAT3 signaling. Finally, combined inhibition of JAK3 (by WHI-P154) and ALK (by crizotinib or alectinib) significantly (p < 0.01) decreased the survival of PTCL cells as compared to either agent alone by inhibiting STAT3 downstream signaling. Collectively, our findings establish that JAK3 is a therapeutic target for a subset of PTCL, and provide rationale for the clinical evaluation of JAK3 inhibitors combined with ALK-targeted therapy in PTCL.

SHP2 Inhibition with TNO155 Increases Efficacy and Overcomes Resistance of ALK Inhibitors in Neuroblastoma

Survival rates among patients with high-risk neuroblastoma remain low and novel therapies for recurrent neuroblastomas are required. ALK is commonly mutated in primary and relapsed neuroblastoma tumors and ALK tyrosine kinase inhibitors (TKI) are promising treatments for ALK-driven neuroblastoma; however, innate or adaptive resistance to single-agent ALK-TKIs remain a clinical challenge. Recently, SHP2 inhibitors have been shown to overcome ALK-TKI resistance in lung tumors harboring ALK rearrangements. Here, we have assessed the efficacy of the SHP2 inhibitor TNO155 alone and in combination with the ALK-TKIs crizotinib, ceritinib, or lorlatinib for the treatment of ALK-driven neuroblastoma using in vitro and in vivo models. In comparison to wild-type, ALK-mutant neuroblastoma cell lines were more sensitive to SHP2 inhibition with TNO155. Moreover, treatment with TNO155 and ALK-TKIs synergistically reduced cell growth and promoted inactivation of ALK and MAPK signaling in ALK-mutant neuroblastoma cells. ALK-mutant cells engrafted into larval zebrafish and treated with single agents or dual SHP2/ALK inhibitors showed reduced growth and invasion. In murine ALK-mutant xenografts, tumor growth was likewise reduced or delayed, and survival was prolonged upon combinatorial treatment of TNO155 and lorlatinib. Finally, we show that lorlatinib-resistant ALK-F1174L neuroblastoma cells harbor additional RAS-MAPK pathway alterations and can be resensitized to lorlatinib when combined with TNO155 in vitro and in vivo. Our results report the first evaluation of TNO155 in neuroblastoma and suggest that combinatorial inhibition of ALK and SHP2 could be a novel approach to treating ALK-driven neuroblastoma, potentially including the increasingly common tumors that have developed resistance to ALK-TKIs.

SIGNIFICANCE

These findings highlight the translatability between zebrafish and murine models, provide evidence of aberrant RAS-MAPK signaling as an adaptive mechanism of resistance to lorlatinib, and demonstrate the clinical potential for SHP2/ALK inhibitor combinations for the treatment of ALK-mutant neuroblastoma, including those with acquired tolerance or potentially resistance to ALK-TKIs.

ALK fusions in the pan-cancer setting: another tumor-agnostic target?

Anaplastic lymphoma kinase (ALK) alterations (activating mutations, amplifications, and fusions/rearrangements) occur in ~3.3% of cancers. ALK fusions/rearrangements are discerned in >50% of inflammatory myofibroblastic tumors (IMTs) and anaplastic large cell lymphomas (ALCLs), but only in ~0.2% of other cancers outside of non-small cell lung cancer (NSCLC), a rate that may be below the viability threshold of even large-scale treatment trials. Five ALK inhibitors -alectinib, brigatinib, ceritinb, crizotinib, and lorlatinib-are FDA approved for ALK-aberrant NSCLCs, and crizotinib is also approved for ALK-aberrant IMTs and ALCL, including in children. Herein, we review the pharmacologic tractability of ALK alterations, focusing beyond NSCLC. Importantly, the hallmark of approved indications is the presence of ALK fusions/rearrangements, and response rates of ~50-85%. Moreover, there are numerous reports of ALK inhibitor activity in multiple solid and hematologic tumors (e.g., histiocytosis, leiomyosarcoma, lymphoma, myeloma, and colorectal, neuroendocrine, ovarian, pancreatic, renal, and thyroid cancer) bearing ALK fusions/rearrangements. Many reports used crizotinib or alectinib, but each of the approved ALK inhibitors have shown activity. ALK inhibitor activity is also seen in neuroblastoma, which bear ALK mutations (rather than fusions/rearrangements), but response rates are lower (~10-20%). Current data suggests that ALK inhibitors have tissue-agnostic activity in neoplasms bearing ALK fusions/rearrangements.

Targeting CCR7-PI3Kγ overcomes resistance to tyrosine kinase inhibitors in ALK-rearranged lymphoma

Anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors (TKIs) show potent efficacy in several ALK-driven tumors, but the development of resistance limits their long-term clinical impact. Although resistance mechanisms have been studied extensively in ALK-driven non-small cell lung cancer, they are poorly understood in ALK-driven anaplastic large cell lymphoma (ALCL). Here, we identify a survival pathway supported by the tumor microenvironment that activates phosphatidylinositol 3-kinase γ (PI3K-γ) signaling through the C-C motif chemokine receptor 7 (CCR7). We found increased PI3K signaling in patients and ALCL cell lines resistant to ALK TKIs. PI3Kγ expression was predictive of a lack of response to ALK TKI in patients with ALCL. Expression of CCR7, PI3Kγ, and PI3Kδ were up-regulated during ALK or STAT3 inhibition or degradation and a constitutively active PI3Kγ isoform cooperated with oncogenic ALK to accelerate lymphomagenesis in mice. In a three-dimensional microfluidic chip, endothelial cells that produce the CCR7 ligands CCL19/CCL21 protected ALCL cells from apoptosis induced by crizotinib. The PI3Kγ/δ inhibitor duvelisib potentiated crizotinib activity against ALCL lines and patient-derived xenografts. Furthermore, genetic deletion of CCR7 blocked the central nervous system dissemination and perivascular growth of ALCL in mice treated with crizotinib. Thus, blockade of PI3Kγ or CCR7 signaling together with ALK TKI treatment reduces primary resistance and the survival of persister lymphoma cells in ALCL.

Refractory Anaplastic Large Cell Lymphoma Rescued by the Combination of the Second-Generation ALK Inhibitor Brigatinib, High-dose Chemotherapy and Allogeneic Stem Cell Transplantation: A Case Report and Review of the Literature

The treatment of pediatric patients with refractory or relapsed anaplastic large cell lymphoma (ALCL) is still a major challenge. In addition to conventional chemotherapy and stem cell transplantation, new therapeutic options such as anti-CD30 drugs and anaplastic lymphoma kinase (ALK) inhibitors have been recently introduced in this setting. Among ALK inhibitors, only the first-generation molecule crizotinib is approved for pediatric use, while second-generation molecules, such as brigatinib, are still under investigation. Here we report the case of a 13-year-old boy diagnosed with stage IV ALCL, refractory to first-line conventional chemotherapy and second-line therapy with the anti CD30 antibody-drug conjugate brentuximab-vedotin, who finally achieved remission after a combination of conventional high-dose chemotherapy and the second-generation ALK inhibitor brigatinib. The latter was chosen for its ability to penetrate through the blood-brain barrier, due to the persistent involvement of the patient's cerebral nervous system. The remission was then consolidated with an allogeneic hematopoietic stem cell transplantation (HSCT) from an unrelated donor using myeloablative conditioning with total body irradiation. At 24 months after HSCT, the patient is in complete remission, alive and well. An updated review regarding the use of ALK inhibitors in ALCL patients is provided.

The 5-lipoxygenase/cyclooxygenase-2 cross-over metabolite, hemiketal E2, enhances VEGFR2 activation and promotes angiogenesis

Consecutive oxygenation of arachidonic acid by 5-lipoxygenase and cyclooxygenase-2 yields the hemiketal eicosanoids, HKE2 and HKD2. Hemiketals stimulate angiogenesis by inducing endothelial cell tubulogenesis in culture; however, how this process is regulated has not been determined. Here, we identify vascular endothelial growth factor receptor 2 (VEGFR2) as a mediator of HKE2-induced angiogenesis in vitro and in vivo. We found that HKE2 treatment of human umbilical vein endothelial cells dose-dependently increased the phosphorylation of VEGFR2 and the downstream kinases ERK and Akt that mediated endothelial cell tubulogenesis. In vivo, HKE2 induced the growth of blood vessels into polyacetal sponges implanted in mice. HKE2-mediated effects in vitro and in vivo were blocked by the VEGFR2 inhibitor vatalanib, indicating that the pro-angiogenic effect of HKE2 was mediated by VEGFR2. HKE2 covalently bound and inhibited PTP1B, a protein tyrosine phosphatase that dephosphorylates VEGFR2, thereby providing a possible molecular mechanism for how HKE2 induced pro-angiogenic signaling. In summary, our studies indicate that biosynthetic cross-over of the 5-lipoxygenase and cyclooxygenase-2 pathways gives rise to a potent lipid autacoid that regulates endothelial cell function in vitro and in vivo. These findings suggest that common drugs targeting the arachidonic acid pathway could prove useful in antiangiogenic therapy.

Tyrosine kinases in nodal peripheral T-cell lymphomas

Nodal peripheral T-cell lymphomas (PTCL) are uncommon and heterogeneous tumors characterized by a dismal prognosis. Targeted therapy has been proposed. However, reliable targets are mostly represented by a few surface antigens (e.g., CD52 and CD30), chemokine receptors (e.g., CCR4), and epigenetic gene expression regulation. In the last two decades, however, several studies have supported the idea that tyrosine kinase (TK) deregulation might be relevant for both the pathogenesis and treatment of PTCL. Indeed, they can be expressed or activated as a consequence of their involvement in genetic lesions, such as translocations, or by ligand overexpression. The most striking example is ALK in anaplastic large-cell lymphomas (ALCL). ALK activity is necessary to support cell proliferation and survival, and its inhibition leads to cell death. Notably, STAT3 was found to be the main downstream ALK effector. Other TKs are consistently expressed and active in PTCLs, such as PDGFRA, and members of the T-cell receptor signaling family, such as SYK. Notably, as in the case of ALK, STAT proteins have emerged as key downstream factors for most of the involved TK.

Regulation of CD45 phosphatase by oncogenic ALK in anaplastic large cell lymphoma

Anaplastic Large Cell Lymphoma (ALCL) is a subtype of non-Hodgkin lymphoma frequently driven by the chimeric tyrosine kinase NPM-ALK, generated by the t (2,5)(p23;q35) translocation. While ALK+ ALCL belongs to mature T cell lymphomas, loss of T cell identity is observed in the majority of ALCL secondary to a transcriptional and epigenetic repressive program induced by oncogenic NPM-ALK. While inhibiting the expression of T cell molecules, NPM-ALK activates surrogate TCR signaling by directly inducing pathways downstream the TCR. CD45 is a tyrosine phosphatase that plays a central role in T cell activation by controlling the TCR signaling and regulating the cytokine responses through the JAK/STAT pathway and exists in different isoforms depending on the stage of T-cell maturation, activation and differentiation. ALK+ ALCL cells mainly express the isoform CD45RO in keeping with their mature/memory T cell phenotype. Because of its regulatory effect on the JAK/STAT pathway that is essential for ALK+ ALCL, we investigated whether CD45 expression was affected by oncogenic ALK. We found that most ALK+ ALCL cell lines express the CD45RO isoform with modest CD45RA expression and that NPM-ALK regulated the expression of these CD45 isoforms. Regulation of CD45 expression was dependent on ALK kinase activity as CD45RO expression was increased when NPM-ALK kinase activity was inhibited by treatment with ALK tyrosine kinase inhibitors (TKIs). Silencing ALK expression through shRNA or degradation of ALK by the PROTAC TL13-112 caused upregulation of CD45RO both at mRNA and protein levels with minimal changes on CD45RA, overall indicating that oncogenic ALK downregulates the expression of CD45. CD45 repression was mediated by STAT3 as demonstrated by ChIP-seq data on ALCL cells treated with the ALK-TKI crizotinib or cells treated with a STAT3 degrader. Next, we found that knocking-out CD45 with the CRISPR/Cas9 system resulted in increased resistance to ALK TKI treatment and CD45 was down-regulated in ALCL cells that developed resistance in vitro to ALK TKIs. Overall, these data suggest that CD45 expression is regulated by ALK via STAT3 and acts as a rheostat of ALK oncogenic signaling and resistance to TKI treatment in ALCL.

Hallmarks of Anaplastic Lymphoma Kinase Inhibitors with Its Quick Emergence of Drug Resistance

Anaplastic lymphoma kinase (ALK) is one of the most popular targets for anticancer therapies. In the past decade, the use of anaplastic lymphoma tyrosine kinase inhibitors (ALK-TKIs), including crizotinib and ceritinib, has been a reliable and standard options for patients with lung cancer, particularly for patients with nonsmall cell lung carcinoma. ALK-targeted therapies initially benefit the patients, yet, resistance eventually occurs. Therefore, resistance mechanisms of ALK-TKIs and the solutions have become a formidable challenge in the development of ALK inhibitors. In this review, based on the knowledge of reported ALK inhibitors, we illustrated the crystal structures of ALK, summarized the resistance mechanisms of ALK-targeted drugs, and proposed potential therapeutic strategies to prevent or overcome the resistance.

Obesity and Risk for Lymphoma: Possible Role of Leptin

Obesity, which is considered a pandemic due to its high prevalence, is a risk factor for many types of cancers, including lymphoma, through a variety of mechanisms by promoting an inflammatory state. Specifically, over the last few decades, obesity has been suggested not only to increase the risk of lymphoma but also to be associated with poor clinical outcomes and worse responses to different treatments for those diseases. Within the extensive range of proinflammatory mediators that adipose tissue releases, leptin has been demonstrated to be a key adipokine due to its pleotropic effects in many physiological systems and diseases. In this sense, different studies have analyzed leptin levels and leptin/leptin receptor expressions as a probable bridge between obesity and lymphomas. Since both obesity and lymphomas are prevalent pathophysiological conditions worldwide and their incidences have increased over the last few years, here we review the possible role of leptin as a promising proinflammatory mediator promoting lymphomas.

Protein tyrosine kinase inhibitor resistance in malignant tumors: molecular mechanisms and future perspective

Protein tyrosine kinases (PTKs) are a class of proteins with tyrosine kinase activity that phosphorylate tyrosine residues of critical molecules in signaling pathways. Their basal function is essential for maintaining normal cell growth and differentiation. However, aberrant activation of PTKs caused by various factors can deviate cell function from the expected trajectory to an abnormal growth state, leading to carcinogenesis. Inhibiting the aberrant PTK function could inhibit tumor growth. Therefore, tyrosine kinase inhibitors (TKIs), target-specific inhibitors of PTKs, have been used in treating malignant tumors and play a significant role in targeted therapy of cancer. Currently, drug resistance is the main reason for limiting TKIs efficacy of cancer. The increasing studies indicated that tumor microenvironment, cell death resistance, tumor metabolism, epigenetic modification and abnormal metabolism of TKIs were deeply involved in tumor development and TKI resistance, besides the abnormal activation of PTK-related signaling pathways involved in gene mutations. Accordingly, it is of great significance to study the underlying mechanisms of TKIs resistance and find solutions to reverse TKIs resistance for improving TKIs efficacy of cancer. Herein, we reviewed the drug resistance mechanisms of TKIs and the potential approaches to overcome TKI resistance, aiming to provide a theoretical basis for improving the efficacy of TKIs.

Holistic View of ALK TKI Resistance in ALK-Positive Anaplastic Large Cell Lymphoma

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase expressed at early stages of normal development and in various cancers including ALK-positive anaplastic large cell lymphoma (ALK+ ALCL), in which it is the main therapeutic target. ALK tyrosine kinase inhibitors (ALK TKIs) have greatly improved the prognosis of ALK+ALCL patients, but the emergence of drug resistance is inevitable and limits the applicability of these drugs. Although various mechanisms of resistance have been elucidated, the problem persists and there have been relatively few relevant clinical studies. This review describes research progress on ALK+ ALCL including the application and development of new therapies, especially in relation to drug resistance. We also propose potential treatment strategies based on current knowledge to inform the design of future clinical trials.

Protein Tyrosine Phosphatases in Neuroblastoma: Emerging Roles as Biomarkers and Therapeutic Targets

Neuroblastoma is a type of cancer intimately related with early development and differentiation of neuroendocrine cells, and constitutes one of the pediatric cancers with higher incidence and mortality. Protein tyrosine phosphatases (PTPs) are key regulators of cell growth and differentiation by their direct effect on tyrosine dephosphorylation of specific protein substrates, exerting major functions in the modulation of intracellular signaling during neuron development in response to external cues driving cell proliferation, survival, and differentiation. We review here the current knowledge on the role of PTPs in neuroblastoma cell growth, survival, and differentiation. The potential of PTPs as biomarkers and molecular targets for inhibition in neuroblastoma therapies is discussed.

Resistance to Targeted Agents Used to Treat Paediatric ALK-Positive ALCL

Simple Summary

In general, the non-Hodgkin lymphoma (NHL), anaplastic large cell lymphoma (ALCL) diagnosed in childhood has a good survival outcome when treated with multi-agent chemotherapy. However, side effects of treatment are common, and outcomes are poorer after relapse, which occurs in up to 30% of cases. New drugs are required that are more effective and have fewer side effects. Targeted therapies are potential solutions to these problems, however, the development of resistance may limit their impact. This review summarises the potential resistance mechanisms to these targeted therapies.

Abstract

Non-Hodgkin lymphoma (NHL) is the third most common malignancy diagnosed in children. The vast majority of paediatric NHL are either Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL), anaplastic large cell lymphoma (ALCL), or lymphoblastic lymphoma (LL). Multi-agent chemotherapy is used to treat all of these types of NHL, and survival is over 90% but the chemotherapy regimens are intensive, and outcomes are generally poor if relapse occurs. Therefore, targeted therapies are of interest as potential solutions to these problems. However, the major problem with all targeted agents is the development of resistance. Mechanisms of resistance are not well understood, but increased knowledge will facilitate optimal management strategies through improving our understanding of when to select each targeted agent, and when a combinatorial approach may be helpful. This review summarises currently available knowledge regarding resistance to targeted therapies used in paediatric anaplastic lymphoma kinase (ALK)-positive ALCL. Specifically, we outline where gaps in knowledge exist, and further investigation is required in order to find a solution to the clinical problem of drug resistance in ALCL.