Tumor tissue and plasma levels of AXL and GAS6 before and after tyrosine kinase inhibitor treatment in EGFR-mutated non-small cell lung cancer

AXL as immune regulator and therapeutic target in Acute Myeloid Leukemia: from current progress to novel strategies

Until recently, treatment options for patients diagnosed with Acute Myeloid Leukemia (AML) were limited and predominantly relied on various combinations, dosages, or schedules of traditional chemotherapeutic agents. Patients with advanced age, relapsed/refractory disease or comorbidities were often left without effective treatment options. Novel advances in the understanding of leukemogenesis at the molecular and genetic levels, alongside recent progress in drug development, have resulted in the emergence of novel therapeutic agents and strategies for AML patients. Among these innovations, the receptor tyrosine kinase AXL has been established as a promising therapeutic target for AML. AXL is a key regulator of several cellular functions, including epithelial-to-mesenchymal transition in tumor cells, immune regulation, apoptosis, angiogenesis and the development of chemoresistance. Clinical studies of AXL inhibitors, as single agents and in combination therapy, have demonstrated promising efficacy in treating AML. Additionally, novel AXL-targeted therapies, such as AXL-specific antibodies or antibody fragments, present potential solutions to overcome the limitations associated with traditional small-molecule AXL inhibitors or multikinase inhibitors. This review provides a comprehensive overview of the structure and biological functions of AXL under normal physiological conditions, including its role in immune regulation. We also summarize AXL's involvement in cancer, with a specific emphasis on its role in the pathogenesis of AML, its contribution to immune evasion and drug resistance. Moreover, we discuss the AXL inhibitors currently undergoing (pre)clinical evaluation for the treatment of AML.

Hallmarks of pancreatic cancer: spotlight on TAM receptors

Pancreatic ductal adenocarcinoma (PDAC) represents the most prevalent type of pancreatic cancer and ranks among the most aggressive tumours, with a 5-year survival rate of less than 11%. Projections indicate that by 2030, it will become the second leading cause of cancer-related deaths. PDAC presents distinctive hallmarks contributing to its dismal prognosis: (i) late diagnosis, (ii) heterogenous and complex mutational landscape, (iii) high metastatic potential, (iv) dense fibrotic stroma, (v) immunosuppressive microenvironment, and (vi) high resistance to therapy. Mounting evidence has shown a role for TAM (Tyro3, AXL, MerTK) family of tyrosine kinase receptors in PDAC initiation and progression. This review aims to describe the impact of TAM receptors on the defining hallmarks of PDAC and discuss potential future directions using these proteins as novel biomarkers for early diagnosis and targets for precision therapy in PDAC, an urgent unmet clinical need.

Phase 1b study of batiraxcept in combination with durvalumab in patients with platinum-resistant ovarian cancer

Combining an immune checkpoint inhibitor with batiraxcept (AVB-S6-500), an AXL inhibitor that acts via selective binding to growth arrest-specific protein 6 (GAS6), may improve anti-tumor immunity in platinum-resistant ovarian cancer (PROC). This phase 1b trial of durvalumab in combination with escalating doses of batiraxcept enrolled patients with recurrent PROC (NCT04019288). The primary objective was to determine the toxicity profile of the combination. Eleven patients were enrolled on the trial. No dose-limiting toxicities were observed, and no objective responses were noted. Median progression free survival (PFS) was 1.81 months (95% confidence interval (CI) 1.71-2.40), and median overall survival (OS) was 4.53 months (95% CI 2.10-24.74). Batiraxcept effectively reduced serum GAS6 levels at 1-h post-treatment, resulting in trough levels below the limit of detection in all cases but one. In conclusion, the combination of batiraxcept and durvalumab was safe and tolerable but did not demonstrate anti-tumor activity in a heterogenous population of patients with recurrent PROC.

Therapeutic targeting of the functionally elusive TAM receptor family

The TAM receptor family of TYRO3, AXL and MERTK regulates tissue and immune homeostasis. Aberrant TAM receptor signalling has been linked to a range of diseases, including cancer, fibrosis and viral infections. Specifically, the dysregulation of TAM receptors can enhance tumour growth and metastasis due to their involvement in multiple oncogenic pathways. For example, TAM receptors have been implicated in the epithelial-mesenchymal transition, maintaining the stem cell phenotype, immune modulation, proliferation, angiogenesis and resistance to conventional and targeted therapies. Therapeutically, multiple TAM receptor inhibitors are in preclinical and clinical development for cancers and other indications, with those targeting AXL being the most clinically advanced. Although there has been notable clinical advancement in recent years, challenges persist. This Review aims to provide both biological and clinical insights into the current therapeutic landscape of TAM receptor inhibitors, and evaluates their potential for the treatment of cancer and non-malignant diseases.

Ningetinib plus gefitinib in EGFR-mutant non-small-cell lung cancer with MET and AXL dysregulations: A phase 1b clinical trial and biomarker analysis

BACKGROUND

MET and AXL dysregulations are implicated in acquired resistance to EGFR-TKIs in NSCLC. But consensus on the optimal definition for MET/AXL dysregulations in EGFR-mutant NSCLC is lacking. Here, we investigated the efficacy and tolerability of ningetinib (a MET/AXL inhibitor) plus gefitinib in EGFR-mutant NSCLC, and evaluated the clinical relevance of MET/AXL dysregulations by different definitions.

METHODS

Patients in this phase 1b dose-escalation/dose-expansion trial received ningetinib 30 mg/40 mg/60 mg plus gefitinib 250 mg once daily. Primary endpoints were tolerability (dose-escalation) and objective response rate (dose-expansion). MET/AXL status were analyzed using FISH and IHC.

RESULTS

Between March 2017 and January 2021, 108 patients were enrolled. The proportion of MET focal amplification, MET polysomy, MET overexpression, AXL amplification and AXL overexpression is 18.1 %, 5.6 %, 55.8 %, 8.1 % and 45.3 %, respectively. 6.8 % patients have concurrent MET amplification and AXL overexpression. ORR is 30.8 % for tumors with MET amplification, 0 % for MET polysomy, 24.1 % for MET overexpression, 20 % for AXL amplification and 27.6 % for AXL overexpression. For patients with concurrent MET amplification and AXL overexpression, ningetinib plus gefitinib provides an ORR of 80 %, DCR of 100 % and median PFS of 4.7 months. Tumors with higher MET copy number and AXL expression tend to have higher likelihood of response. Biomarker analyses show that MET focal amplification and overexpression are complementary in predicting clinical benefit from MET inhibition, while AXL dysregulations defined by an arbitrary level may dilute the efficacy of AXL blockade.

CONCLUSIONS

This study demonstrates that combined blockade of MET, AXL and EGFR is a feasible strategy for a subset of EGFR-mutant NSCLC.

TRIAL REGISTRATION

Chinadrugtrials.org.cn, CTR20160875.

Evaluation of combination treatment with DS-1205c, an AXL kinase inhibitor, and osimertinib in metastatic or unresectable EGFR-mutant non-small cell lung cancer: results from a multicenter, open-label phase 1 study

The objective of this study was to evaluate the safety and tolerability of DS-1205c, an oral AXL-receptor inhibitor, in combination with osimertinib in metastatic or unresectable EFGR-mutant non-small cell lung cancer (NSCLC) patients who developed disease progression during EGFR tyrosine kinase inhibitor (TKI) treatment. An open-label, non-randomized phase 1 study was conducted in Taiwan, in which 13 patients received DS-1205c monotherapy at a dosage of 200, 400, 800, or 1200 mg twice daily for 7 days, followed by combination treatment with DS-1205c (same doses) plus osimertinib 80 mg once daily in 21-day cycles. Treatment continued until disease progression or other discontinuation criteria were met. At least one treatment-emergent adverse event (TEAE) was reported in all 13 patients treated with DS-1205c plus osimertinib; with ≥ 1 grade 3 TEAE in 6 patients (one of whom also had a grade 4 increased lipase level), and 6 patients having ≥ 1 serious TEAE. Eight patients experienced ≥ 1 treatment-related AE (TRAE). The most common (2 cases each) were anemia, diarrhea, fatigue, increased AST, increased ALT, increased blood creatinine phosphokinase, and increased lipase. All TRAEs were non-serious, with the exception of an overdose of osimertinib in 1 patient. No deaths were reported. Two-thirds of patients achieved stable disease (one-third for > 100 days), but none achieved a complete or partial response. No association between AXL positivity in tumor tissue and clinical efficacy was observed. DS-1205c was well-tolerated with no new safety signals in patients with advanced EGFR-mutant NSCLC when administered in combination with the EFGR TKI osimertinib. ClinicalTrials.gov ; NCT03255083.

Dissecting the Role of AXL in Cancer Immune Escape and Resistance to Immune Checkpoint Inhibition

The development and implementation of Immune Checkpoint Inhibitors (ICI) in clinical oncology have significantly improved the survival of a subset of cancer patients with metastatic disease previously considered uniformly lethal. However, the low response rates and the low number of patients with durable clinical responses remain major concerns and underscore the limited understanding of mechanisms regulating anti-tumor immunity and tumor immune resistance. There is an urgent unmet need for novel approaches to enhance the efficacy of ICI in the clinic, and for predictive tools that can accurately predict ICI responders based on the composition of their tumor microenvironment. The receptor tyrosine kinase (RTK) AXL has been associated with poor prognosis in numerous malignancies and the emergence of therapy resistance. AXL is a member of the TYRO3-AXL-MERTK (TAM) kinase family. Upon binding to its ligand GAS6, AXL regulates cell signaling cascades and cellular communication between various components of the tumor microenvironment, including cancer cells, endothelial cells, and immune cells. Converging evidence points to AXL as an attractive molecular target to overcome therapy resistance and immunosuppression, supported by the potential of AXL inhibitors to improve ICI efficacy. Here, we review the current literature on the prominent role of AXL in regulating cancer progression, with particular attention to its effects on anti-tumor immune response and resistance to ICI. We discuss future directions with the aim to understand better the complex role of AXL and TAM receptors in cancer and the potential value of this knowledge and targeted inhibition for the benefit of cancer patients.

Acquired Mechanisms of Resistance to Osimertinib-The Next Challenge

Simple Summary

Osimertinib has revolutionized the treatment of EGFR-mutated tumors. Its current applications include the first-line setting, second-line setting, as well as the adjuvant setting. Although it represents a milestone in the context of targeted therapy, inevitably all tumors develop an acquired resistance, some mechanisms involve EGFR, others do so through alternative pathways leading to a bypass in osimertinib inhibition. It is key to understand these acquired mechanisms of resistance, both in the clinical setting, as well as in preclinical models, in order to develop and contribute to the identification of possible therapeutic strategies to overcome this acquired resistance.

Abstract

EGFR-mutated tumors represent a significant percentage of non-small cell lung cancer. Despite the increasing use of osimertinib, a treatment that has demonstrated an outstanding clinical benefit with a tolerable toxicity profile, EGFR tumors eventually acquire mechanisms of resistance. In the last years, multiple mechanisms of resistance have been identified; however, after progressing on osimertinib, treatment options remain bleak. In this review, we cover the most frequent alterations and potential therapeutic strategies to overcome them.

The First Evaluation of Serum Levels of MGP, Gas6 and EGFR after First Dose of Chemotherapy in Lung Cancer

Simple Summary

Serum levels of MGP, Gas6, vitamin K₁, and EGFR were not significantly changed in response to the first cycle of chemotherapy. We found a strong correlation between MGP and VitK₁ serum values, and a moderate negative correlation between VitK₁ and EGFR in pre-treatment patients. The post-treatment value of EGFR is a strong independent factor that correlates positively with the Gas6 post-treatment values.

Abstract

Background: Vitamin K-dependent proteins (VKDPs) and the epidermal growth factor receptor (EGFR) are involved in lung cancer progression. Therefore, we aimed to study the serum concentration of Matrix Gla protein (MGP), Growth Arrest-specific 6 (Gas6), and EGFR before and after the first cycle of chemotherapy and to investigate how MGP, Gas6, and EGFR are modified after one cycle of chemotherapy. Methods: We performed an observational study on twenty patients diagnosed with lung cancer, by assessing the serum concentration of vitaminK₁ (VitK₁), MGP, Gas6, and EGFR using the ELISA technique before and after three weeks of the first cycle of chemotherapy. Patients were evaluated using RECIST 1.1 criteria. Results: Serum levels of MGP, Gas6, EGFR, and VK₁ before and after treatment were not changed significantly. Regarding the pre-treatment correlation of the MGP values, we found a strong positive relationship between MGP and VK₁ pre-treatment values (r = 0.821, 95%CI 0.523; 0.954, p < 0.001). Furthermore, there was a moderately negative correlation between VK₁ and EGFR pre-treatment values, with the relationship between them being marginally significant (r = −0.430, 95%CI −0.772; 0.001, p = 0.058). Post-treatment, we found a strong positive relationship between MGP and VK₁ post-treatment values (r = 0.758, 95%CI 0.436; 0.900, p < 0.001). We also found a moderate positive relationship between Gas6 and EGFR post-treatment values, but the correlation was only marginally significant (r = 0.442, p = 0.051).

Cell Line Models for Acquired Resistance to First-Line Osimertinib in Lung Cancers-Applications and Limitations

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are first-line drugs for lung cancers with activating EGFR mutations. Although first- and second-generation EGFR-TKIs were standard first-line treatments, acquired resistance (AR) to these drugs is almost inevitable. Cell line models have been widely used to explore the molecular mechanisms of AR to first- and second-generation EGFR-TKIs. Many research groups, including ours, have established AR cell lines that harbor the EGFR T790M secondary mutation, MET gene amplification, or epithelial–mesenchymal transition (EMT) features, which are all found in clinical specimens obtained from TKI-refractory lesions. Currently, many oncologists prescribe osimertinib, a third-generation EGFR-TKI that can overcome T790M-mediated resistance, as a first-line TKI. Although few clinical data are available about AR mechanisms that arise when osimertinib is used as a first-line therapy, many research groups have established cell lines with AR to osimertinib and have reported on their AR mechanisms. In this review, we summarize the findings on AR mechanisms against first-line osimertinib obtained from analyses of cell line models.

Current Strategies for Treating NSCLC: From Biological Mechanisms to Clinical Treatment

The identification of specific epidermal growth factor receptor (EGFR)-activating mutations heralded a breakthrough in non-small-cell lung cancer (NSCLC) treatments, with the subsequent development of EGFR-tyrosine kinase inhibitor (TKIs) becoming the first-line therapy for patients harboring EGFR mutations. However, acquired resistance to EGFR-TKIs inevitably occurs in patients following initial TKI treatment, leading to disease progression. Various mechanisms are behind the acquired resistance, and mainly include (1) target gene modification, (2) alternative parallel pathway activation, (3) downstream pathway activation, and (4) histological/phenotypic transformation. Approaches to combat the acquired resistance have been investigated according to these mechanisms. Newer generations of TKIs have been developed to target the secondary/tertiary EGFR mutations in patients with acquired resistance. In addition, combination therapies have been developed as another promising strategy to overcome acquired resistance through the activation of other signaling pathways. Thus, in this review, we summarize the mechanisms for acquired resistance and focus on the potential corresponding therapeutic strategies for acquired resistance.

Mechanism research of miR-34a regulates Axl in non-small-cell lung cancer with gefitinib-acquired resistance

Background

To investigate the regulatory mechanism behind miR‐34a‐altered Axl levels in non‐small‐cell lung cancer (NSCLC) with gefitinib‐acquired resistance.

Methods

The expression of miR‐34a, Axl, Gas6 and related downstream signaling proteins in the EGFR mutant NSCLC cell lines were determined by qRT‐PCR and Western blot; PC9‐Gef‐miR‐34a and HCC827‐Gef‐miR‐34a cells were established by transfecting the parent cells with a miR‐34a overexpressing virus, then the expression of Axl, Gas6 and the downstream channel‐related proteins were also compared in PC9‐Gef‐miR‐34a and HCC827‐Gef‐miR‐34a and drug‐resistant strains. The survival rate of the cells were measured by CCK8 assay. A luciferase reporter detected whether Axl was the target of miR‐34a. Finally, a tumor‐bearing nude mouse model was established to verify the relationship between the expression of miR‐34a, Axl and Gas6 mRNA in vivo.

Results

The expression levels of Axl mRNA and protein, Gas6 mRNA and protein, and related downstream proteins in PC9‐Gef and HCC827‐Gef cell lines were higher than those in PC9 and HCC827 parental cell lines, while the expression of miR‐34a was lower than it was in the parental cell lines (P < 0.05). The expression of Axl mRNA and protein, Gas6 mRNA and protein, and related downstream signaling proteins in PC9‐Gef and HCC827‐Gef cell lines was higher than the expression in PC9‐Gef‐miR‐34a and HCC827‐Gef‐miR‐34a cells, which overexpressed miR‐34a (P < 0.05).

Conclusion

The miR‐34a regulation of Axl plays an important role in NSCLC‐acquired gefitinib resistance, and their expression is inversely correlated, which suggests that they can be used as prognostic markers or potential therapeutic targets for NSCLC.