Inhibiting the GAS6/AXL axis suppresses tumor progression by blocking the interaction between cancer-associated fibroblasts and cancer cells in gastric carcinoma

Co-targeting JAK1/STAT6/GAS6/TAM signaling improves chemotherapy efficacy in Ewing sarcoma

Ewing sarcoma is a pediatric bone and soft tissue tumor treated with chemotherapy, radiation, and surgery. Despite intensive multimodality therapy, ~50% patients eventually relapse and die of the disease due to chemoresistance. Here, using phospho-profiling, we find Ewing sarcoma cells treated with chemotherapeutic agents activate TAM (TYRO3, AXL, MERTK) kinases to augment Akt and ERK signaling facilitating chemoresistance. Mechanistically, chemotherapy-induced JAK1-SQ phosphorylation releases JAK1 pseudokinase domain inhibition allowing for JAK1 activation. This alternative JAK1 activation mechanism leads to STAT6 nuclear translocation triggering transcription and secretion of the TAM kinase ligand GAS6 with autocrine/paracrine consequences. Importantly, pharmacological inhibition of either JAK1 by filgotinib or TAM kinases by UNC2025 sensitizes Ewing sarcoma to chemotherapy in vitro and in vivo. Excitingly, the TAM kinase inhibitor MRX-2843 currently in human clinical trials to treat AML and advanced solid tumors, enhances chemotherapy efficacy to further suppress Ewing sarcoma tumor growth in vivo. Our findings reveal an Ewing sarcoma chemoresistance mechanism with an immediate translational value.

Recent discovery and development of AXL inhibitors as antitumor agents

AXL, a receptor tyrosine kinase (RTK), plays a pivotal role in various cellular functions. It is primarily involved in processes such as epithelial-mesenchymal transition (EMT) in tumor cells, angiogenesis, apoptosis, immune regulation, and chemotherapy resistance mechanisms. Therefore, targeting AXL is a promising therapeutic approach for the treatment of cancer. AXL inhibitors that have entered clinical trials, such as BGB324(1), have shown promising efficacy in the treatment of melanoma and non-small cell lung cancer. Additionally, novel AXL-targeted drugs, such as AXL degraders, offer a potential solution to overcome the limitations of traditional small-molecule AXL inhibitors targeting single pathways. We provide an overview of the structure and biological functions of AXL, discusses its correlation with various cancers, and critically analyzes the structure-activity relationship of AXL small-molecule inhibitors in cellular contexts. Additionally, we summarize multiple research and development strategies, offering insights for the future development of innovative AXL inhibitors.

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.

Deciphering drug resistance in gastric cancer: Potential mechanisms and future perspectives

Gastric cancer (GC) is a malignant tumor that originates from the epithelium of the gastric mucosa. The latest global cancer statistics show that GC ranks fifth in incidence and fourth in mortality among all cancers, posing a serious threat to public health. While early-stage GC is primarily treated through surgery, chemotherapy is the frontline option for advanced cases. Currently, commonly used chemotherapy regimens include FOLFOX (oxaliplatin + leucovorin + 5-fluorouracil) and XELOX (oxaliplatin + capecitabine). However, with the widespread use of chemotherapy, an increasing number of cases of drug resistance have emerged. This article primarily explores the potential mechanisms of chemotherapy resistance in GC patients from five perspectives: cell death, tumor microenvironment, non-coding RNA, epigenetics, and epithelial-mesenchymal transition. Additionally, it proposes feasibility strategies to overcome drug resistance from four angles: cancer stem cells, tumor microenvironment, natural products, and combined therapy. The hope is that this article will provide guidance for researchers in the field and bring hope to more GC patients.

Cancer-associated fibroblasts: protagonists of the tumor microenvironment in gastric cancer

Enhanced knowledge of the interaction of cancer cells with their environment elucidated the critical role of tumor microenvironment in tumor progression and chemoresistance. Cancer-associated fibroblasts act as the protagonists of the tumor microenvironment, fostering the metastasis, stemness, and chemoresistance of cancer cells and attenuating the anti-cancer immune responses. Gastric cancer is one of the most aggressive cancers in the clinic, refractory to anti-cancer therapies. Growing evidence indicates that cancer-associated fibroblasts are the most prominent risk factors for a poor tumor immune microenvironment and dismal prognosis in gastric cancer. Therefore, targeting cancer-associated fibroblasts may be central to surpassing resistance to conventional chemotherapeutics, molecular-targeted agents, and immunotherapies, improving survival in gastric cancer. However, the heterogeneity in cancer-associated fibroblasts may complicate the development of cancer-associated fibroblast targeting approaches. Although single-cell sequencing studies started dissecting the heterogeneity of cancer-associated fibroblasts, the research community should still answer these questions: "What makes a cancer-associated fibroblast protumorigenic?"; "How do the intracellular signaling and the secretome of different cancer-associated fibroblast subpopulations differ from each other?"; and "Which cancer-associated fibroblast subtypes predominate specific cancer types?". Unveiling these questions can pave the way for discovering efficient cancer-associated fibroblast targeting strategies. Here, we review current knowledge and perspectives on these questions, focusing on how CAFs induce aggressiveness and therapy resistance in gastric cancer. We also review potential therapeutic approaches to prevent the development and activation of cancer-associated fibroblasts via inhibition of CAF inducers and CAF markers in cancer.

Targeting GAS6/AXL signaling improves the response to immunotherapy by restoring the anti-immunogenic tumor microenvironment in gastric cancer

AIMS

Immunotherapy has shown remarkable effects on several malignancies; however, its impact on gastric cancers has been limited. Therefore, a novel strategy to overcome resistance to immunotherapy is required. In this study, we compared the gene expression profiles of two murine GC cell lines that exhibited different effects on tumor immunity. The functions of specific genes related to negative tumor immunity and the impact of a specific inhibitor were evaluated in syngeneic GC mouse models.

MATERIALS AND METHODS

RT-PCR and Western blotting validated Gas6 and AXL expression in murine cell lines. RT-PCR compared YTN16 and YTN3 GC cell's impact on T cell activation. AXL, the receptor for GAS6 in YTN16, was validated by western blotting. Gas6 was inhibited in YTN16 cells using shRNA, and then the gene expression pattern, effects to T cell activation, and tumor growth were assessed. YTN16 cells were injected into mice and treated with CCB-3233, anti-PD-1 antibody, or both. Immunohistochemistry and flow cytometry evaluated tumor-infiltrating immune cells.

KEY FINDINGS

YTN16 cells expressed more Gas6 and had reduced T cell activation compared to YTN3 cells. AXL activation was higher in YTN16. CCB-3233 reduced AXL phosphorylation. Knocking down Gas6 in YTN16 reduced immunosuppression-related genes and increased tumor-infiltrating T cells. Combined CCB-3233 and anti-PD-1 treatment reduced tumor growth and increased T-cell infiltration. Human GC data revealed a negative correlation between GAS6 and immune activation-related genes.

SIGNIFICANCE

The GAS6/AXL pathway contributes to immunotherapy resistance in GC. Targeting this pathway may be a novel therapeutic strategy.

Intervention of AXL in EGFR Signaling via Phosphorylation and Stabilization of MIG6 in Non-Small Cell Lung Cancer

About 80% of lung cancer patients are diagnosed with non-small cell lung cancer (NSCLC). EGFR mutation and overexpression are common in NSCLC, thus making EGFR signaling a key target for therapy. While EGFR kinase inhibitors (EGFR-TKIs) are widely used and efficacious in treatment, increases in resistance and tumor recurrence with alternative survival pathway activation, such as that of AXL and MET, occur frequently. AXL is one of the EMT (epithelial-mesenchymal transition) signature genes, and EMT morphological changes are also responsible for EGFR-TKI resistance. MIG6 is a negative regulator of ERBB signaling and has been reported to be positively correlated with EGFR-TKI resistance, and downregulation of MIG6 by miR-200 enhances EMT transition. While MIG6 and AXL are both correlated with EMT and EGFR signaling pathways, how AXL, MIG6 and EGFR interplay in lung cancer remains elusive. Correlations between AXL and MIG6 expression were analyzed using Oncomine or the CCLE. A luciferase reporter assay was used for determining MIG6 promoter activity. Ectopic overexpression, RNA interference, Western blot analysis, qRT-PCR, a proximity ligation assay and a coimmunoprecipitation assay were performed to analyze the effects of certain gene expressions on protein-protein interaction and to explore the underlying mechanisms. An in vitro kinase assay and LC-MS/MS were utilized to determine the phosphorylation sites of AXL. In this study, we demonstrate that MIG6 is a novel substrate of AXL and is stabilized upon phosphorylation at Y310 and Y394/395 by AXL. This study reveals a connection between MIG6 and AXL in lung cancer. AXL phosphorylates and stabilizes MIG6 protein, and in this way EGFR signaling may be modulated. This study may provide new insights into the EGFR regulatory network and may help to advance cancer treatment.

Altered expression of AXL receptor tyrosine kinase in gastrointestinal cancers: a promising therapeutic target

Gastrointestinal (GI) cancers that include all cancers of the digestive tract organs are generally associated with obesity, lack of exercising, smoking, poor diet, and heavy alcohol consumption. Treatment of GI cancers typically involves surgery followed by chemotherapy and/or radiation. Unfortunately, intrinsic or acquired resistance to these therapies underscore the need for more effective targeted therapies that have been proven in other malignancies. The aggressive features of GI cancers share distinct signaling pathways that are connected to each other by the overexpression and activation of AXL receptor tyrosine kinase. Several preclinical and clinical studies involving anti-AXL antibodies and small molecule AXL kinase inhibitors to test their efficacy in solid tumors, including GI cancers, have been recently carried out. Therefore, AXL may be a promising therapeutic target for overcoming the shortcomings of standard therapies in GI cancers.

Identification and verification of eight cancer-associated fibroblasts related genes as a prognostic signature for head and neck squamous cell carcinoma

Cancer-associated fibroblasts (CAFs) can exert their immunosuppressive effects by secreting various effectors that are involved in the regulation of tumor-infiltrating immune cells as well as other immune components in the tumor immune microenvironment (TIME), thereby promoting tumorigenesis, progression, metastasis, and drug resistance. Although a large number of studies suggest that CAFs play a key regulatory role in the development of head and neck squamous cell carcinoma (HNSCC), there are limited studies on the relevance of CAFs to the prognosis of HNSCC. In this study, we identified a prognostic signature containing eight CAF-related genes for HNSCC by univariate Cox analysis, lasso regression, stepwise regression, and multivariate Cox analysis. Our validation in primary cultures of CAFs from human HNSCC and four human HNSCC cell lines confirmed that these eight genes are indeed characteristic markers of CAFs. Immune cell infiltration differences analysis between high-risk and low-risk groups according to the eight CAF-related genes signature hinted at CAFs regulatory roles in the TIME, further revealing its potential role on prognosis. The signature of the eight CAF-related genes was validated in different independent validation cohorts and all showed that it was a valid marker for prognosis. The significantly higher overall survival (OS) in the low-risk group compared to the high-risk group was confirmed by Kaplan-Meier (K-M) analysis, suggesting that the signature of CAF-related genes can be used as a non-invasive predictive tool for HNSCC prognosis. The low-risk group had significantly higher levels of tumor-killing immune cell infiltration, as confirmed by CIBERSORT analysis, such as CD8⁺ T cells, follicular helper T cells, and Dendritic cells (DCs) in the low-risk group. In contrast, the level of infiltration of pro-tumor cells such as M0 macrophages and activated Mast cells (MCs) was lower. It is crucial to delve into the complex mechanisms between CAFs and immune cells to find potential regulatory targets and may provide new evidence for subsequently targeted immunotherapy. These results suggest that the signature of the eight CAF-related genes is a powerful indicator for the assessment of the TIME of HNSCC. It may provide a new and reliable potential indicator for clinicians to predict the prognosis of HNSCC, which may be used to guide treatment and clinical decision-making in HNSCC patients. Meanwhile, CAF-related genes are expected to become tumor biomarkers and effective targets for HNSCC.

Regulation of epithelial-mesenchymal transition by tumor microenvironmental signals and its implication in cancer therapeutics

Epithelial-mesenchymal transition (EMT) has been implicated in various aspects of tumor development, including tumor invasion and metastasis, cancer stemness, and therapy resistance. Diverse stroma cell types along with biochemical and biophysical factors in the tumor microenvironment impinge on the EMT program to impact tumor progression. Here we provide an in-depth review of various tumor microenvironmental signals that regulate EMT in cancer. We discuss the molecular mechanisms underlying the role of EMT in therapy resistance and highlight new therapeutic approaches targeting the tumor microenvironment to impact EMT and tumor progression.

Oncolytic virus: A catalyst for the treatment of gastric cancer

Gastric cancer (GC) is a leading contributor to global cancer incidence and mortality. According to the GLOBOCAN 2020 estimates of incidence and mortality for 36 cancers in 185 countries produced by the International Agency for Research on Cancer (IARC), GC ranks fifth and fourth, respectively, and seriously threatens the survival and health of people all over the world. Therefore, how to effectively treat GC has become an urgent problem for medical personnel and scientific workers at this stage. Due to the unobvious early symptoms and the influence of some adverse factors such as tumor heterogeneity and low immunogenicity, patients with advanced gastric cancer (AGC) cannot benefit significantly from treatments such as radical surgical resection, radiotherapy, chemotherapy, and targeted therapy. As an emerging cancer immunotherapy, oncolytic virotherapies (OVTs) can not only selectively lyse cancer cells, but also induce a systemic antitumor immune response. This unique ability to turn unresponsive 'cold' tumors into responsive 'hot' tumors gives them great potential in GC therapy. This review integrates most experimental studies and clinical trials of various oncolytic viruses (OVs) in the diagnosis and treatment of GC. It also exhaustively introduces the concrete mechanism of invading GC cells and the viral genome composition of adenovirus and herpes simplex virus type 1 (HSV-1). At the end of the article, some prospects are put forward to determine the developmental directions of OVTs for GC in the future.

Research Progress on Therapeutic Targeting of Cancer-Associated Fibroblasts to Tackle Treatment-Resistant NSCLC

Non-small cell lung cancer (NSCLC) accounts for most lung cancer cases and is the leading cause of cancer-related deaths worldwide. Treatment options for lung cancer are no longer limited to surgery, radiotherapy, and chemotherapy, as targeted therapy and immunotherapy offer a new hope for patients. However, drug resistance in chemotherapy and targeted therapy, and the low response rates to immunotherapy remain important challenges. Similar to tumor development, drug resistance occurs because of significant effects exerted by the tumor microenvironment (TME) along with cancer cell mutations. Cancer-associated fibroblasts (CAFs) are a key component of the TME and possess multiple functions, including cross-talking with cancer cells, remodeling of the extracellular matrix (ECM), secretion of various cytokines, and promotion of epithelial-mesenchymal transition, which in turn provide support for the growth, invasion, metastasis, and drug resistance of cancer cells. Therefore, CAFs represent valuable therapeutic targets for lung cancer. Herein, we review the latest progress in the use of CAFs as potential targets and mediators of drug resistance for NSCLC treatment. We explored the role of CAFs on the regulation of the TME and surrounding ECM, with particular emphasis on treatment strategies involving combined CAF targeting within the current framework of cancer treatment.

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.

Extracellular Vesicles Promote the Formation of Pre-Metastasis Niche in Gastric Cancer

Globally, gastric cancer (GC) ranks fourth in the incidence of malignant tumors. The early clinical manifestations of GC lack specificity. Most patients are already at an advanced stage when they are first diagnosed, and their late progression is mainly due to peritoneal metastasis. A pre-metastatic microenvironment is formed, before the macroscopic tumor metastasis. Extracellular vesicles (EVs) are nanovesicles released by cells into body fluids. Recent studies have shown that EVs can affect the tumor microenvironment by carrying cargos to participate in cell-to-cell communication. EVs derived from GC cells mediate the regulation of the pre-metastasis niche and act as a coordinator between tumor cells and normal stroma, immune cells, inflammatory cells, and tumor fibroblasts to promote tumor growth and metastasis. This review highlights the regulatory role of EVs in the pre-metastatic niche of GC and mulls EVs as a potential biomarker for liquid biopsy.

PDIA4, a new endoplasmic reticulum stress protein, modulates insulin resistance and inflammation in skeletal muscle

INTRODUCTION

Endoplasmic reticulum (ER) stress has emerged as a key player in insulin resistance (IR) progression in skeletal muscle. Recent reports revealed that ER stress-induced the expression of protein disulfide isomerase family a member 4 (PDIA4), which may be involved in IR-related diseases. A previous study showed that metformin modulated ER stress-induced IR. However, it remained unclear whether metformin alleviated IR by regulating PDIA4 expression in skeletal muscle.

METHODS

Herein, we used palmitate-induced IR in C2C12 cells and a high-fat diet-induced IR mouse model to document the relations between metformin, IR, and PDIA4.

RESULTS

In C2C12 cells, palmitate-induced IR increased inflammatory cytokines and PDIA4 expression. Besides, knocking down PDIA4 decreased palmitate-induced IR and inflammation in C2C12 cells. Furthermore, metformin modulated PDIA4 expression and alleviated IR both in vitro and in vivo. In addition, serum PDIA4 concentrations are associated with IR and inflammatory cytokines levels in human subjects.

DISCUSSION

Thus, this study is the first to demonstrate that PDIA4 participates in the metformin-induced effects on skeletal muscle IR and indicates that PDIA4 is a potential novel therapeutic target for directly alleviating IR.

Immune Evasion Mechanism and AXL

Extensive interest in cancer immunotherapy is reported according to the clinical importance of CTLA-4 and (PD-1/PD-L1) [programmed death (PD) and programmed death-ligand (PD-L1)] in immune checkpoint therapies. AXL is a receptor tyrosine kinase expressed in different types of cancer and in relation to resistance against various anticancer therapeutics due to poor clinical prognosis. AXL and its ligand, i.e., growth arrest-specific 6 (GAS6) proteins, are expressed on many cancer cells, and the GAS6/AXL pathway is reported to promote cancer cell proliferation, survival, migration, invasion, angiogenesis, and immune evasion. AXL is an attractive and novel therapeutic target for impairing tumor progression from immune cell contracts in the tumor microenvironment. The GAS6/AXL pathway is also of interest immunologically because it targets fewer antitumor immune responses. In effect, several targeted therapies are selective and nonselective for AXL, which are in preclinical and clinical development in multiple cancer types. Therefore, this review focuses on the role of the GAS6/AXL signaling pathway in triggering the immunosuppressive tumor microenvironment as immune evasion. This includes regulating its composition and activating T-cell exclusion with the immune-suppressive activity of regulatory T cells, which is related to one of the hallmarks of cancer survival. Finally, this article discusses the GAS6/AXL signaling pathway in the context of several immune responses such as NK cell activation, apoptosis, and tumor-specific immunity, especially PD-1/PDL-1 signaling.

Therapeutic Targeting of the Gas6/Axl Signaling Pathway in Cancer

Many signaling pathways are dysregulated in cancer cells and the host tumor microenvironment. Aberrant receptor tyrosine kinase (RTK) pathways promote cancer development, progression, and metastasis. Hence, numerous therapeutic interventions targeting RTKs have been actively pursued. Axl is an RTK that belongs to the Tyro3, Axl, MerTK (TAM) subfamily. Axl binds to a high affinity ligand growth arrest specific 6 (Gas6) that belongs to the vitamin K-dependent family of proteins. The Gas6/Axl signaling pathway has been implicated to promote progression, metastasis, immune evasion, and therapeutic resistance in many cancer types. Therapeutic agents targeting Gas6 and Axl have been developed, and promising results have been observed in both preclinical and clinical settings when such agents are used alone or in combination therapy. This review examines the current state of therapeutics targeting the Gas6/Axl pathway in cancer and discusses Gas6- and Axl-targeting agents that have been evaluated preclinically and clinically.

A review on the role of GAS6 and GAS6-AS1 in the carcinogenesis

Growth arrest specific 6 (GAS6) encodes a protein that serves as a ligand for AXL receptor tyrosine kinase and stimulates cell proliferation. Notably, an antisense RNA, namely GAS6-AS1 is transcribed from chromosome 13q34, near GAS6 gene. In vitro functional experiments have demonstrated that GAS6-AS1 can promote proliferation, migration and invasive properties of transformed cells through enhancing entry into S-phase. Notably, mechanistic investigations have shown that GAS6-AS1 can regulate expression of GAS6 at the transcriptional or translational stages through constructing a RNA-RNA duplex, thus enhancing expression of AXL and inducing AXL signaling. Both GAS6 and its antisense transcript contribute in the pathogenesis of human malignancies. In the current review, we provide a summary of studies that appraised the role of these genes in the carcinogenesis.

Targeting AXL in NSCLC

State-of-the-art cancer precision medicine approaches involve targeted inactivation of chemically and immunologically addressable vulnerabilities that often yield impressive initial anti-tumor responses in patients. Nonetheless, these responses are overshadowed by therapy resistance that follows. AXL, a receptor tyrosine kinase with bona fide oncogenic capacity, has been associated with the emergence of resistance in an array of cancers with varying pathophysiology and cellular origins, including in non-small-cell lung cancers (NSCLCs). Here in this review, we summarize AXL biology during normal homeostasis, oncogenic development and therapy resistance with a focus on NSCLC. In the context of NSCLC therapy resistance, we delineate AXL's role in mediating resistance to tyrosine kinase inhibitors (TKIs) deployed against epidermal growth factor receptor (EGFR) as well as other notable oncogenes and to chemotherapeutics. We also discuss the current understanding of AXL's role in mediating cell-biological variables that function as important modifiers of therapy resistance such as epithelial to mesenchymal transition (EMT), the tumor microenvironment and tumor heterogeneity. We also catalog and discuss a set of effective pharmacologic tools that are emerging to strategically perturb AXL mediated resistance programs in NSCLC. Finally, we enumerate ongoing and future exciting precision medicine approaches targeting AXL as well as challenges in this regard. We highlight that a holistic understanding of AXL biology in NSCLC may allow us to predict and improve targeted therapeutic strategies, such as through polytherapy approaches, potentially against a broad spectrum of NSCLC sub-types to forestall tumor evolution and drug resistance.

20 (S)-ginsenoside Rh2 inhibits colorectal cancer cell growth by suppressing the Axl signaling pathway in vitro and in vivo

Background

Colorectal cancer (CRC) has a high morbidity and mortality worldwide. 20 (S)-ginsenoside Rh2 (G-Rh2) is a natural compound extracted from ginseng, which exhibits anticancer effects in many cancer types. In this study, we demonstrated the effect and underlying molecular mechanism of G-Rh2 in CRC cells in vitro and in vivo.

Methods

Cell proliferation, migration, invasion, apoptosis, cell cycle, and western blot assays were performed to evaluate the effect of G-Rh2 on CRC cells. In vitro pull-down assay was used to verify the interaction between G-Rh2 and Axl. Transfection and infection experiments were used to explore the function of Axl in CRC cells. CRC xenograft models were used to further investigate the effect of Axl knockdown and G-Rh2 on tumor growth in vivo.

Results

G-Rh2 significantly inhibited proliferation, migration, and invasion, and induced apoptosis and G₀/G₁ phase cell cycle arrest in CRC cell lines. G-Rh2 directly binds to Axl and inhibits the Axl signaling pathway in CRC cells. Knockdown of Axl suppressed the growth, migration and invasion ability of CRC cells in vitro and xenograft tumor growth in vivo, whereas overexpression of Axl promoted the growth, migration, and invasion ability of CRC cells. Moreover, G-Rh2 significantly suppressed CRC xenograft tumor growth by inhibiting Axl signaling with no obvious toxicity to nude mice.

Conclusion

Our results indicate that G-Rh2 exerts anticancer activity in vitro and in vivo by suppressing the Axl signaling pathway. G-Rh2 is a promising candidate for CRC prevention and treatment.

An Investigation of the Antigastric Cancer Effect in Tumor Microenvironment of Radix Rhei Et Rhizome: A Network Pharmacology Study

Background

Tumor microenvironment (TME) takes a vital effect on the occurrence and development of cancer. Radix Rhei Et Rhizome (RRER, Da-Huang in pinyin), a classical Chinese herb, has been widely used in gastric cancer (GC) for many years in China. However, inadequate systematic studies have focused on the anti-GC effect of RRER in TME. This study intended to uncover the mechanism of it by network pharmacology.

Methods

We collected compounds and targets of RRER from traditional Chinese medicine system pharmacology database and analysis platform (TCMSP) and SwissTargetPrediction. GC targets were obtained from GeneCards. Protein-protein interaction (PPI) network and RRER-GC-target network were built by STRING and Cytoscape 3.2.1. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed using Database for Annotation, Visualization, and Integrated Discovery (DAVID).

Results

We obtained 92 compounds of RRER. A total of 10 key compounds and 20 key targets were selected by “RRER-GC-target network” topological analysis. GO analysis showed that the biological process mainly involved in response to the tumor necrosis factor, positive regulation of fibroblast proliferation, and DNA damage response, signal transduction by p53 class mediator resulting in cell cycle arrest. Molecular functions included cyclin-dependent protein serine/threonine kinase activity, RNA polymerase II transcription factor activity, ligand-activated sequence-specific DNA binding, and transmembrane receptor protein tyrosine kinase activity. Cellular components mainly were centrosome, cell surface, and membrane. KEGG pathway enrichment results mainly involved in the p53 signaling pathway, estrogen signaling pathway, and regulation of lipolysis in adipocytes.

Conclusion

This study explored the anti-GC mechanism of RRER from the perspective of TME based on network pharmacology, which contributed to the development and application of RRER.

Signaling pathways in cancer-associated fibroblasts and targeted therapy for cancer

To flourish, cancers greatly depend on their surrounding tumor microenvironment (TME), and cancer-associated fibroblasts (CAFs) in TME are critical for cancer occurrence and progression because of their versatile roles in extracellular matrix remodeling, maintenance of stemness, blood vessel formation, modulation of tumor metabolism, immune response, and promotion of cancer cell proliferation, migration, invasion, and therapeutic resistance. CAFs are highly heterogeneous stromal cells and their crosstalk with cancer cells is mediated by a complex and intricate signaling network consisting of transforming growth factor-beta, phosphoinositide 3-kinase/AKT/mammalian target of rapamycin, mitogen-activated protein kinase, Wnt, Janus kinase/signal transducers and activators of transcription, epidermal growth factor receptor, Hippo, and nuclear factor kappa-light-chain-enhancer of activated B cells, etc., signaling pathways. These signals in CAFs exhibit their own special characteristics during the cancer progression and have the potential to be targeted for anticancer therapy. Therefore, a comprehensive understanding of these signaling cascades in interactions between cancer cells and CAFs is necessary to fully realize the pivotal roles of CAFs in cancers. Herein, in this review, we will summarize the enormous amounts of findings on the signals mediating crosstalk of CAFs with cancer cells and its related targets or trials. Further, we hypothesize three potential targeting strategies, including, namely, epithelial-mesenchymal common targets, sequential target perturbation, and crosstalk-directed signaling targets, paving the way for CAF-directed or host cell-directed antitumor therapy.

Regulation of ARL2 in colorectal cancer cell proliferation and tumorigenicity, and its negative association with AXL

Colorectal cancer (CRC) is the third most common malignant disease in adults. ADP ribosylation factor-like GTPase 2 (ARL2) is crucial for controlling the dynamics of microtubules and mitochondrial functions. However, the biological function of ARL2 in CRC remains unclear. The present study was performed to identify the expression level and functional role of ARL2 in CRC. A total of 19 CRC and 3 normal healthy colorectal tissues were collected. Furthermore, ARL2 expression was analyzed in healthy colorectal and CRC tissues by immunohistochemistry (IHC). ARL2 overexpression and knockdown was achieved using lentiviral vectors and plasmid transfection in HCT8 and HCT116 cells. The protein and mRNA expression levels of ARL2 and AXL were analyzed using western blot and reverse transcription-quantitative PCR in ARL2 knockdown and ARL2 overexpressing HCT8 and HCT116 cells. Cell Counting Kit-8, colony formation, wound healing, and Matrigel assays were used to investigate the biological functions of ARL2. Taken together, ARL2 protein expression level was upregulated in CRC tissues. Furthermore, ARL2 overexpression decreased proliferation and weakened the colony-formation abilities of the CRC cells, as well as their migratory and invasive abilities. ARL2 interference enhanced proliferation and colony-formation rates of the CRC cells, as well as their migratory and invasive abilities. ARL2 regulated CRC proliferation and tumorigenicity and was negatively associated with AXL. The results of the present study suggested that the proliferation, migration and tumorigenicity of the CRC cells could be inhibited by ARL2 overexpression. The latter may be used as a predicted and potential therapeutic target for CRC.

Gas6/Axl Signaling Pathway in the Tumor Immune Microenvironment

Receptor tyrosine kinases have been shown to dysregulate a number of pathways associated with tumor development, progression, and metastasis. Axl is a receptor tyrosine kinase expressed in many cancer types and has been associated with therapy resistance and poor clinical prognosis and outcomes. In addition, Axl and its ligand growth arrest specific 6 (Gas6) protein are expressed by a number of host cells. The Gas6/Axl signaling pathway has been implicated in the promotion of tumor cell proliferation, survival, migration, invasion, angiogenesis, and immune evasion. As a result, Axl is an attractive, novel therapeutic target to impair multiple stages of tumor progression from both neoplastic and host cell axes. This review focuses on the role of the Gas6/Axl signaling pathway in promoting the immunosuppressive tumor microenvironment, as immune evasion is considered one of the hallmarks of cancer. The review discusses the structure and activation of the Gas6/Axl signaling pathway, GAS6 and AXL expression patterns in the tumor microenvironment, mechanisms of Axl-mediated tumor immune response, and the role of Gas6/Axl signaling in immune cell recruitment.

Implications of the Receptor Tyrosine Kinase Axl in Gastric Cancer Progression

Background

Gastric cancer (GC) is an aggressive malignancy with high lethality. Systematic chemotherapy is the main therapeutic strategy for advanced GC patients. The overexpression of Axl is associated with poor prognosis and regulates tumor growth and metastasis in many types of cancer. However, the role of Axl in GC progression remains elusive.

Materials and Methods

Western blot and quantitative real-time PCR assay (RT-PCR) assays were used to detect the expression of Gas6, Axl, ZEB1 and epithelial-mesenchymal transition (EMT)-related markers in GC cells. Cell proliferation was determined by EdU cell proliferation assay and CCK-8 assay. Transwell invasion assay was performed to explore the effect of Axl and ZEB1 on cell invasion. Tumor xenografts and lung metastasis models were conducted to examine the effect of Axl on the growth and lung metastasis of GC cells.

Results

In our study, we found that high levels of Gas6 and Axl expression were associated with reduced overall survival (OS) in GC patients and the expression of Gas6 and Axl was upregulated in GC cell lines. Ectopic expression of Axl induced EMT and promoted GC cell invasion and proliferation. The knockdown of Axl inhibited EMT and suppressed the proliferation and invasion of GC cell. In vivo study showed that inhibition of Axl impaired tumor growth and lung metastasis of GC cells. Mechanistic investigations revealed that Axl promoted EMT, invasion, and proliferation via upregulating ZEB1 expression in GC cells.

Conclusion

Our results demonstrated that the Gas6/Axl/ZEB1 signaling pathway regulated EMT, invasion, and proliferation in GC cells and might represent a potential therapeutic target for GC treatment.

Qigesan inhibits esophageal cancer cell invasion and migration by inhibiting Gas6/Axl-induced epithelial-mesenchymal transition

Qigesan (QGS) has been used to effectively treat esophageal cancer (EC) for decades in China, but the mechanism by which it suppresses EC metastasis remains unknown. In this study, we examined the effects of QGS on EC cell mobility. Using immunohistochemistry and immunofluorescence, expression of Gas6 and Axl, which promote tumor cell migration and invasion, was examined in carcinoma tissues and adjacent normal tissues from EC patients. Levels of Gas6, Axl, and the Gas6/Axl complex were also examined in ECA109 and TE13 EC cells treated with QGS. In addition, immunofluorescent staining and quantitative protein analysis were used to examine E-cadherin, N-cadherin, and Snail levels in ECA109 and TE13 EC cells after QSG administration, and cell mobility was assessed. The results demonstrated that levels of Gas6 and Axl expression are higher in EC tissues than in adjacent normal tissues. Moreover, QGS decreased Gas6/Axl levels, increased E-cadherin expression, decreased Snail and N-cadherin expression, and inhibited epithelial-mesenchymal transition (EMT) in EC cells. QGS thus suppresses EMT in EC by inhibiting Gas6/Axl binding.