Emerging Roles of ALK in Immunity and Insights for Immunotherapy

Identification of a Fully Human Antibody VH Domain Targeting Anaplastic Lymphoma Kinase (ALK) with Applications in ALK-Positive Solid Tumor Immunotherapy

The anaplastic lymphoma kinase (ALK, CD247) is a potential target for antibody-based therapy. However, no antibody-based therapeutics targeting ALK have entered clinical trials, necessitating the development of novel antibodies with unique therapeutic merits. Single-domain antibodies (sdAb) bear therapeutic advantages compared to the full-length antibody including deeper tumor penetration, cost-effective production and fast washout from normal tissues. In this study, we identified a human immunoglobulin heavy chain variable domain (VH domain) (VH20) from an in-house phage library. VH20 exhibits good developability and high specificity with no off-target binding to ~6000 human membrane proteins. VH20 efficiently bound to the glycine-rich region of ALK with an EC50 of 0.4 nM and a KD of 6.54 nM. Both VH20-based bispecific T cell engager (TCE) and chimeric antigen receptor T cells (CAR Ts) exhibited potent cytolytic activity to ALK-expressing tumor cells in an ALK-dependent manner. VH20 CAR Ts specifically secreted proinflammatory cytokines including IL-2, TNFα and IFNγ after incubation with ALK-positive cells. To our knowledge, this is the first reported human single-domain antibody against ALK. Our in vitro characterization data indicate that VH20 could be a promising ALK-targeting sdAb with potential applications in ALK-expressing tumors, including neuroblastoma (NBL) and non-small cell lung cancer.

Mechanisms of resistance to targeted therapy and immunotherapy in non-small cell lung cancer: promising strategies to overcoming challenges

Resistance to targeted therapy and immunotherapy in non-small cell lung cancer (NSCLC) is a significant challenge in the treatment of this disease. The mechanisms of resistance are multifactorial and include molecular target alterations and activation of alternative pathways, tumor heterogeneity and tumor microenvironment change, immune evasion, and immunosuppression. Promising strategies for overcoming resistance include the development of combination therapies, understanding the resistance mechanisms to better use novel drug targets, the identification of biomarkers, the modulation of the tumor microenvironment and so on. Ongoing research into the mechanisms of resistance and the development of new therapeutic approaches hold great promise for improving outcomes for patients with NSCLC. Here, we summarize diverse mechanisms driving resistance to targeted therapy and immunotherapy in NSCLC and the latest potential and promising strategies to overcome the resistance to help patients who suffer from NSCLC.

Targeting ALK averts ribonuclease 1-induced immunosuppression and enhances antitumor immunity in hepatocellular carcinoma

Tumor-secreted factors contribute to the development of a microenvironment that facilitates the escape of cancer cells from immunotherapy. In this study, we conduct a retrospective comparison of the proteins secreted by hepatocellular carcinoma (HCC) cells in responders and non-responders among a cohort of ten patients who received Nivolumab (anti-PD-1 antibody). Our findings indicate that non-responders have a high abundance of secreted RNase1, which is associated with a poor prognosis in various cancer types. Furthermore, mice implanted with HCC cells that overexpress RNase1 exhibit immunosuppressive tumor microenvironments and diminished response to anti-PD-1 therapy. RNase1 induces the polarization of macrophages towards a tumor growth-promoting phenotype through activation of the anaplastic lymphoma kinase (ALK) signaling pathway. Targeting the RNase1/ALK axis reprograms the macrophage polarization, with increased CD8+ T- and Th1- cell recruitment. Moreover, simultaneous targeting of the checkpoint protein PD-1 unleashes cytotoxic CD8+ T-cell responses. Treatment utilizing both an ALK inhibitor and an anti-PD-1 antibody exhibits enhanced tumor regression and facilitates long-term immunity. Our study elucidates the role of RNase1 in mediating tumor resistance to immunotherapy and reveals an RNase1-mediated immunosuppressive tumor microenvironment, highlighting the potential of targeting RNase1 as a promising strategy for cancer immunotherapy in HCC.

ALK peptide vaccination restores the immunogenicity of ALK-rearranged non-small cell lung cancer

Anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer (NSCLC) is treated with ALK tyrosine kinase inhibitors (TKIs), but the lack of activity of immune checkpoint inhibitors (ICIs) is poorly understood. Here, we identified immunogenic ALK peptides to show that ICIs induced rejection of ALK+ tumors in the flank but not in the lung. A single-peptide vaccination restored priming of ALK-specific CD8+ T cells, eradicated lung tumors in combination with ALK TKIs and prevented metastatic dissemination of tumors to the brain. The poor response of ALK+ NSCLC to ICIs was due to ineffective CD8+ T cell priming against ALK antigens and is circumvented through specific vaccination. Finally, we identified human ALK peptides displayed by HLA-A*02:01 and HLA-B*07:02 molecules. These peptides were immunogenic in HLA-transgenic mice and were recognized by CD8+ T cells from individuals with NSCLC, paving the way for the development of a clinical vaccine to treat ALK+ NSCLC.

ALK-JNK signaling promotes NLRP3 inflammasome activation and pyroptosis via NEK7 during Streptococcus pneumoniae infection

Streptococcus pneumoniae (S. pneumoniae), a clinically important pathogen worldwide, causes serious invasive diseases, such as pneumonia, otitis media, and meningitis. The NLR family pyrin domain-containing 3 (NLRP3) inflammasome, an important component of the innate immune system, plays a key role in defense against pathogen infection; however the specific activation mechanism induced by S. pneumoniae infection is not fully understood. Here, primary mouse macrophages were selected as the in vitro cell model, and the effect of kinases on S. pneumoniae infection-induced NLRP3 inflammasome activation was investigated in vivo and in vitro using the western blot/RT-PCR/Co-IP/immunofluorescence staining/ELISA with or without kinase inhibitor or siRNA pretreatment. In this study, we found that the formation of the NEK7-NLRP3 complex significantly increased during S. pneumoniae infection and that anaplastic lymphoma kinase (ALK) and Jun N-terminal kinase (JNK) were phosphorylated rapidly. ALK and JNK inhibitors significantly reduced the ability of bacterial killing, the gene expression of NLRP3 inflammasome, the formation of apoptosis-associated speck-like protein containing caspase-recruitment domain (ASC) specks and the NEK7-NLRP3 complex, which in turn decreased the activation level of NLRP3 inflammasome-associated molecules and the maturation of interleukin-1β (IL-1β). In addition, ALK regulated the phosphorylation of JNK. Interestingly, the ALK/JNK/NEK7-NLRP3 signaling pathway is also involved in regulating pyroptosis and IL-1β secretion triggered by S. pneumoniae infection. In conclusion, our data suggest, for the first time, that the ALK/JNK/NEK7-NLRP3 signaling pathway may play an important role in NLRP3 inflammasome activation and pyroptosis and consequently regulate the host immune response upon S. pneumoniae infection.

Current status and challenges of immunotherapy in ALK rearranged NSCLC

Rearrangements of the anaplastic lymphoma kinase (ALK) gene account for 5-6% in non-small cell lung cancer (NSCLC). ALK rearranged NSCLC is sensitive to ALK tyrosine kinase inhibitors (TKIs) but prone to drug resistance. Meanwhile, ALK rearranged NSCLC has poor response to single immunotherapy. Here we mainly describe the immune escape mechanisms of ALK mutated NSCLC and the role of related biomarkers. Additionally, we collate and evaluate preclinical and clinical studies of novel immune combination regimens, and describe the prospects and perspectives for the in vivo application of novel immune technologies in patients with ALK rearranged NSCLC.

Anaplastic lymphoma kinase-special immunity and immunotherapy

Alterations in the anaplastic lymphoma kinase (ALK) gene play a key role in the development of various human tumors, and targeted therapy has transformed the treatment paradigm for these oncogene-driven tumors. However, primary or acquired resistance remains a challenge. ALK gene variants (such as gene rearrangements and mutations) also play a key role in the tumor immune microenvironment. Immunotherapy targeting the ALK gene has potential clinical applications. Here, we review the results of recent studies on the immunological relevance of ALK-altered tumors, which provides important insights into the development of tumor immunotherapies targeting this large class of tumors.

Targeting ALK Rearrangements in NSCLC: Current State of the Art

Anaplastic lymphoma kinase (ALK) alterations in non-small cell lung cancer (NSCLC) can be effectively treated with a variety of ALK-targeted drugs. After the approval of the first-generation ALK inhibitor crizotinib which achieved better results in prolonging the progression-free survival (PFS) compared with chemotherapy, a number of next-generation ALK inhibitors have been developed including ceritinib, alectinib, brigatinib, and ensartinib. Recently, a potent, third-generation ALK inhibitor, lorlatinib, has been approved by the Food and Drug Administration (FDA) for the first-line treatment of ALK-positive (ALK+) NSCLC. These drugs have manageable toxicity profiles. Responses to ALK inhibitors are however often not durable, and acquired resistance can occur as on-target or off-target alterations. Studies are underway to explore the mechanisms of resistance and optimal treatment options beyond progression. Efforts have also been undertaken to develop further generations of ALK inhibitors. This review will summarize the current situation of targeting the ALK signaling pathway.

The Role of Oncogenes and Redox Signaling in the Regulation of PD-L1 in Cancer

Tumor cells can evade the immune system via multiple mechanisms, including the dysregulation of the immune checkpoint signaling. These signaling molecules are important factors that can either stimulate or inhibit tumor immune response. Under normal physiological conditions, the interaction between programmed cell death ligand 1 (PD-L1) and its receptor, programmed cell death 1 (PD-1), negatively regulates T cell function. In cancer cells, high expression of PD-L1 plays a key role in cancer evasion of the immune surveillance and seems to be correlated with clinical response to immunotherapy. As such, it is important to understand various mechanisms by which PD-L1 is regulated. In this review article, we provide an up-to-date review of the different mechanisms that regulate PD-L1 expression in cancer. We will focus on the roles of oncogenic signals (c-Myc, EML4-ALK, K-ras and p53 mutants), growth factor receptors (EGFR and FGFR), and redox signaling in the regulation of PD-L1 expression and discuss their clinical relevance and therapeutic implications. These oncogenic signalings have common and distinct regulatory mechanisms and can also cooperatively control tumor PD-L1 expression. Finally, strategies to target PD-L1 expression in tumor microenvironment including combination therapies will be also discussed.

The mechanisms of resistance to second- and third-generation ALK inhibitors and strategies to overcome such resistance

INTRODUCTION

Anaplastic lymphoma kinase (ALK) inhibitors are widely known to contribute to the long-term survival of ALK-rearranged non-small cell lung cancer (NSCLC) patients. Based on clinical trial data, treatment with second- or third-generation ALK inhibitors can be initiated after crizotinib therapy without analyzing resistance mechanisms, and some randomized trials have recently shown the superiority of second- or third-generation ALK inhibitors over crizotinib as the initial treatment; however, the optimal treatment for patients who relapse while on second- or third-generation ALK inhibitors is not well-defined.

AREAS COVERED

This review provides an overview of the mechanisms of resistance to second- or third-generation ALK inhibitors that have been identified in both clinical and pre-clinical settings, and introduces strategies for overcoming resistance and discusses ongoing clinical trials.

EXPERT OPINION

The comprehensive elucidation of both ALK-dependent and ALK-independent resistance mechanisms is necessary to improve the prognosis of patients with ALK-rearranged NSCLC. Liquid biopsy to clarify these mechanisms of resistance might play an important role in the near future.

Tumor Mutation Burden and Differentially Mutated Genes Among Immune Phenotypes in Patients with Lung Adenocarcinoma

Introduction

Nowadays, immune checkpoint blockades (ICBs) have been extensively applied in non-small cell lung cancer (NSCLC) treatment. However, the outcome of anti-program death-1/program death ligand-1 (anti-PD-1/PD-L1) therapy is not satisfying in EGFR-mutant lung adenocarcinoma (LUAD) patients and its exact mechanisms have not been fully understood. Since tumor mutation burden (TMB) and tumor immune phenotype had been thought as potential predictors for efficacy of ICBs, we further studied the TMB and immune phenotype in LUAD patients to explore potential mechanisms for poor efficacy of ICBs in EGFR positive mutated patients and to find possible factors that could impact the tumor immune phenotype which might uncover some new therapeutic strategies or combination therapies.

Methods

We enrolled 223 LUAD patients who underwent surgery in our hospital. We evaluated TMB through targeted panel sequencing. The tumor immune phenotype, which could be divided into non-inflamed, intermediate and inflamed, was determined through immunohistochemistry using formalin-fixed paraffin-embedded samples. Enumeration data were analyzed by Chi-square test or Fisher exact test and shown as number (proportion). Logistic regression model was employed for univariate and multivariate analysis of the association between TMB levels and clinical characteristics.

Results

The median TMB level was 4.0445 mutations/Mb. Multivariate analysis showed the TMB level was significantly associated with age (P=0.026), gender (P=0.041) and EGFR mutation status (P=0.015), and in EGFR-mutant patients we found a lower proportion of patients with mutated KRAS and BRCA2. Furthermore, we found patients with or without metastatic lesions would have different immune phenotype (P=0.007). And the mutational frequencies of ALK, CDKN2A, MAP2K1, IDH2 and PTEN were significantly different among three immune phenotypes.

Conclusion

Low TMB level could be the reason for the poor efficacy of ICBs in patients having EGFR mutation. And mutational frequencies of KRAS and BRCA2 were lower in EGFR-mutant patients. Furthermore, ALK, CDKN2A, MAP2K1, IDH2 and PTEN might involve in the formation of immune phenotypes.

Mst1/2-ALK promotes NLRP3 inflammasome activation and cell apoptosis during Listeria monocytogenes infection

Listeria monocytogenes (L. monocytogenes) is a Gram-positive intracellular foodborne pathogen that causes severe diseases, such as meningitis and sepsis. The NLR family pyrin domain-containing 3 (NLRP3) inflammasome has been reported to participate in host defense against pathogen infection. However, the exact molecular mechanisms underlying NLRP3 inflammasome activation remain to be fully elucidated. In the present study, the roles of mammalian Ste20-like kinases 1/2 (Mst1/2) and Anaplastic Lymphoma Kinase (ALK) in the activation of the NLRP3 inflammasome induced by L. monocytogenes infection were investigated. The expression levels of Mst1/2, phospho (p)-ALK, p-JNK, Nek7, and NLRP3 downstream molecules including activated cas-pase-1 (p20) and mature interleukin (IL)-1β (p17), were up-regulated in L. monocytogenes-infected macrophages. The ALK inhibitor significantly decreased the expression of p-JNK, Nek7, and NLRP3 downstream molecules in macrophages infected with L. monocytogenes. Furthermore, the Mst1/2 inhibitor markedly inhibited the L. monocytogenes-induced activation of ALK, subsequently downregulating the expression of p-JNK, Nek7, and NLRP3 downstream molecules. Therefore, our study demonstrated that Mst1/2-ALK mediated the activation of the NLRP3 inflammasome by promoting the interaction between Nek7 and NLRP3 via JNK during L. monocytogenes infection, which subsequently increased the maturation and release of proinflammatory cytokine to resist pathogen infection. Moreover, Listeriolysin O played a key role in the process. In addition, we also found that the L. monocytogenes-induced apoptosis of J774A.1 cells was reduced by the Mst1/2 or ALK inhibitor. The present study reported, for the first time, that the Mst1/2-ALK-JNK-NLRP3 signaling pathway plays a vital proinflammatory role during L. monocytogenes infection.

Immunotherapy for ALK-Rearranged Non-Small Cell Lung Cancer: Challenges Inform Promising Approaches

Rearrangements in the Anaplastic Lymphoma Kinase (ALK) gene have been implicated in 5-6% of all non-small cell lung cancers. ALK-rearranged non-small cell lung cancers are sensitive to ALK-directed tyrosine kinase inhibitors, but generally resistant to single-agent immune checkpoint inhibitors. Here, we aim to describe the mechanisms of ALK aberrations in non-small cell lung cancer by which an immunosuppressed tumor microenvironment is created, leading to host immune evasion. We report pre-clinical and clinical studies evaluating novel immunotherapeutic approaches and describe the promises and challenges of incorporating immune-based treatments for ALK-rearranged non-small cell lung cancer.

Therapeutic Sequencing in ALK+ NSCLC

Anaplastic lymphoma kinase-rearranged non-small-cell lung cancer (ALK⁺ NSCLC) is a model disease for the use of targeted pharmaceuticals in thoracic oncology. Due to higher systemic and intracranial efficacy, the second-generation ALK tyrosine kinase inhibitors (TKI) alectinib and brigatinib have irrevocably displaced crizotinib as standard first-line treatment, based on the results of the ALEX and ALTA-1L trials. Besides, lorlatinib and brigatinib are the preferred second-line therapies for progression under second-generation TKI and crizotinib, respectively, based on the results of several phase II studies. Tissue or liquid rebiopsies at the time of disease progression, even though not mandated by the approval status of any ALK inhibitor, are gaining importance for individualization and optimization of patient management. Of particular interest are cases with off-target resistance, for example MET, HER2 or KRAS alterations, which require special therapeutic maneuvers, e.g., inclusion in early clinical trials or off-label administration of respectively targeted drugs. On the other hand, up to approximately half of the patients failing TKI, develop anatomically restricted progression, which can be initially tackled with local ablative measures without switch of systemic therapy. Among the overall biologically favorable ALK⁺ tumors, with a mean tumor mutational burden uniquely below 3 mutations per Mb and the longest survival among NSCLC currently, presence of the EML4-ALK fusion variant 3 and/or TP53 mutations identify high-risk cases with earlier treatment failure and a need for more aggressive surveillance and treatment strategies. The potential clinical utility of longitudinal ctDNA assays for earlier detection of disease progression and improved guidance of therapy in these patients is a currently a matter of intense investigation. Major pharmaceutical challenges for the field are the development of more potent, fourth-generation TKI and effective immuno-oncological interventions, especially ALK-directed cell therapies, which will be essential for further improving survival and achieving cure of ALK⁺ tumors.