When RON MET TAM in Mesothelioma: All Druggable for One, and One Drug for All?

Small-molecule agents for cancer immunotherapy

Cancer immunotherapy, exemplified by the remarkable clinical benefits of the immune checkpoint blockade and chimeric antigen receptor T-cell therapy, is revolutionizing cancer therapy. They induce long-term tumor regression and overall survival benefit in many types of cancer. With the advances in our knowledge about the tumor immune microenvironment, remarkable progress has been made in the development of small-molecule drugs for immunotherapy. Small molecules targeting PRR-associated pathways, immune checkpoints, oncogenic signaling, metabolic pathways, cytokine/chemokine signaling, and immune-related kinases have been extensively investigated. Monotherapy of small-molecule immunotherapeutic drugs and their combinations with other antitumor modalities are under active clinical investigations to overcome immune tolerance and circumvent immune checkpoint inhibitor resistance. Here, we review the latest development of small-molecule agents for cancer immunotherapy by targeting defined pathways and highlighting their progress in recent clinical investigations.

The mystery of titan hunter: Rationalized striking of the MAPK pathway via Newly synthesized 6-Indolylpyridone-3-Carbonitrile derivatives

MAPK pathway sparkles with RTK activation, passes through subsequent downstream RAS-RAF-MEK-ERK signaling cascades, with consequent direct and indirect CDK4/6 signaling activation, and ends with cell survival, division, and proliferation. However, the emergence of anomalies such as mutations or overexpression in one or more points of the pathway could lead to cancer development and drug resistance. Therefore, designing small inhibitors to strike multitudinous MAPK pathway steps could be a promising synergistic strategy to confine cancer. In this study, twelve 6-indolylpyridone-3-carbonitrile candidates were synthesized and assessed in vitro for antineoplastic activity using four cancer cell lines. The initial antiproliferative screening revealed that compounds 3g, 3h, and 3i were the most potent candidates (GI% Avg = 70.10, 73.94, 74.33%, respectively) compared to staurosporine (GI% Avg = 70.99%). The subsequent safety and selectivity assessment showed that 3h exhibited sub-micromolar inhibition against lung cancer cells (HOP-92 GI50 = 0.75 μM) and 13.7 times selectivity toward cancerous cells over normal cells. As a result, 3h was nominated for deep mechanistic studies which evidenced that compound 3h impressively blocks multiple keystones of the MAPK pathway with nanomolar potency (EGFRWT IC50 = 281 nM, c-MET IC50 = 205 nM, B-RAFWT IC50 = 112 nM, and CDK4/6 IC50 = 95 and 184 nM, respectively). Surprisingly, 3h showed a remarkable potency against mutated EGFR and B-RAF, being 4 and 1.3 more selective to the mutated enzymes over the wild-type forms (EGFRT790M IC50 = 69 nM and B-RAFV600E IC50 = 83 nM). Ultimately, combined molecular docking and molecular dynamics (MD) calculations were executed to inspect the mode of binding and the complex stability of 3h towards the keystones of the MAPK pathway.

A network map of macrophage-stimulating protein (MSP) signaling

Macrophage-stimulating protein (MSP), a serum-derived growth factor belonging to the plasminogen-related kringle domain family, is mainly produced by the liver and released into the blood. MSP is the only known ligand for RON ("Recepteur d'Origine Nantais", also known as MST1R), which is a member of the receptor tyrosine kinase (RTK) family. MSP is associated with many pathological conditions, including cancer, inflammation, and fibrosis. Activation of the MSP/RON system regulates main downstream signaling pathways, including phosphatidylinositol 3-kinase/ AKT serine/threonine kinase/ (PI3-K/AKT), mitogen-activated protein kinases (MAPK), c-Jun N-terminal kinase (JNK) & Focal adhesion kinase (FAK). These pathways are mainly involved in cell proliferation, survival, migration, invasion, angiogenesis & chemoresistance. In this work, we created a pathway resource of signaling events mediated by MSP/RON considering its contribution to diseases. We provide an integrated pathway reaction map of MSP/RON that is composed of 113 proteins and 26 reactions based on the curation of data from the published literature. The consolidated pathway map of MSP/RON mediated signaling events contains seven molecular associations, 44 enzyme catalysis, 24 activation/inhibition, six translocation events, 38 gene regulation events, and forty-two protein expression events. The MSP/RON signaling pathway map can be freely accessible through the WikiPathways Database URL: https://classic.wikipathways.org/index.php/Pathway:WP5353 .

Targeting AXL in Mesothelioma: from functional characterization to clinical implication

Malignant pleural mesothelioma (MM) is a highly aggressive and lethal cancer with a poor survival rate. Current treatment approaches primarily rely on chemotherapy and radiation, but their effectiveness is limited. Consequently, there is an urgent need for alternative treatment strategies, a comprehensive understanding of the molecular mechanisms underlying MM, and the identification of potential therapeutic targets. Extensive studies over the past decade have emphasized the role of Axl in driving tumor development and metastasis, while high levels of Axl expression have been associated with immune evasion, drug resistance, and reduced patient survival in various cancer types. Ongoing clinical trials are investigating the efficacy of Axl inhibitors for different cancers. However, the precise role of Axl in MM progression, development, and metastasis, as well as its regulatory mechanisms within MM, remain inadequately understood. This review aims to comprehensively investigate the involvement of Axl in MM. We discuss Axl role in MM progression, development, and metastasis, along with its specific regulatory mechanisms. Additionally, we examined the Axl associated signaling pathways, the relationship between Axl and immune evasion, and the clinical implications of Axl for MM treatment. Furthermore, we discussed the potential utility of liquid biopsy as a non-invasive diagnostic technique for early detection of Axl in MM. Lastly, we evaluated the potential of a microRNA signature that targets Axl. By consolidating existing knowledge and identifying research gaps, this review contributes to a better understanding of Axl's role in MM and sets the stage for future investigations and the development of effective therapeutic interventions.

Fibrosis in Mesothelioma: Potential Role of Lysyl Oxidases

Immunotherapies (such as checkpoint inhibitors) and standard chemotherapies (such as cisplatin) have limitations in the successful treatment of malignant pleural mesothelioma (MPM). Fibrosis is the accumulation of collagen in the extracellular matrix (ECM) of tissues, making them denser than that of healthy tissues and thereby affecting drug delivery and immune cell infiltration. Moreover, fibrosis severely affects the patient's breathing and quality of life. The production of collagen and its assembly is highly regulated by various enzymes such as lysyl oxidases. Many solid tumors aberrantly express the family of lysyl oxidases (LOX/LOXL). This review examines how LOX/LOXLs were found to be dysregulated in noncancerous and cancerous settings, discusses their roles in solid tumor fibrosis and pathogenesis and explores the role of fibrosis in the development and poor clinical outcomes of patients with MPM. We examine the current preclinical status of drugs targeting LOX/LOXLs and how the incorporation of such drugs may have therapeutic benefits in the treatment and management of patients with MPM.

A potential signaling axis between RON kinase receptor and hypoxia-inducible factor-1 alpha in pancreatic cancer

The Cancer Genome Atlas (TCGA) of a pancreatic cancer cohort identified high MST1R (RON tyrosine kinase receptor) expression correlated with poor prognosis in human pancreatic cancer. RON expression is null/minimal in normal pancreas but elevates from pan-in lesions through invasive carcinomas. We report using multiple approaches RON directly regulates HIF-1α, a critical driver of genes involved in cancer cell invasion and metastasis. RON and HIF-1α are highly co-expressed in the 101 human PDAC tumors analyzed and RON expression correlated with HIF-1α expression in a subset of PDAC cell lines. knockdown of RON expression in RON positive cells blocked HIF-1α expression, whereas ectopic RON expression in RON null cells induced HIF-1α expression suggesting the direct regulation of HIF-1α by RON kinase receptor. RON regulates HIF-1α through an unreported transcriptional mechanism involving PI3 kinase-mediated AKT phosphorylation and Sp1-dependent HIF-1α promoter activity leading to increased HIF-1α mRNA expression. RON/HIF-1α modulation altered the invasive behavior of PDAC cells. A small-molecule RON kinase inhibitor decreased RON ligand, MSP-induced HIF-1α expression, and invasion of PDAC cells. Immunohistochemical analysis on RON knockdown orthotopic PDAC tumor xenograft confirmed that RON inhibition significantly blocked HIF-1α expression. RON/HIF-1α co-expression also exists in triple-negative breast cancer cells, a tumor type that also lacks molecular therapeutic targets. This is the first report describing RON/HIF-1α axis in any tumor type and is a potential novel therapeutic target.

Loop-Mediated Isothermal Amplification in a Core-Shell Bead Assay for the Detection of Tyrosine Kinase AXL Overexpression

The upregulated expression of tyrosine kinase AXL has been reported in several hematologic and solid human tumors, including gastric, breast, colorectal, prostate and ovarian cancers. Thus, AXL can potentially serve as a diagnostic and prognostic biomarker for various cancers. This paper reports the first ever loop-mediated isothermal amplification (LAMP) in a core-shell bead assay for the detection of AXL gene overexpression. We demonstrated simple instrumentation toward a point-of-care device to perform LAMP. This paper also reports the first ever use of core-shell beads as a microreactor to perform LAMP as an attempt to promote environmentally-friendly laboratory practices.

Combined Analysis of RNA Sequence and Microarray Data Reveals a Competing Endogenous RNA Network as Novel Prognostic Markers in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a highly aggressive cancer with short survival time. Unbalanced competing endogenous RNAs (ceRNAs) have been shown to participate in the tumor pathogenesis and served as biomarkers for the clinical prognosis. However, the comprehensive analyses of the ceRNA network in the prognosis of MPM are still rarely reported. In this study, we obtained the transcriptome data of the MPM and the normal samples from TCGA, EGA, and GEO databases and identified the differentially expressed (DE) mRNAs, lncRNAs, and miRNAs. The functions of the prognostic genes and the overlapped DEmRNAs were further annotated by the multiple enrichment analyses. Then, the targeting relationships among lncRNA–miRNA and miRNA–mRNA were predicted and calculated, and a prognostic ceRNA regulatory network was established. We included the prognostic 73 mRNAs and 13 miRNAs and 26 lncRNAs into the ceRNA network. Moreover, 33 mRNAs, three miRNAs, and seven lncRNAs were finally associated with prognosis, and a model including seven mRNAs, two lincRNAs, and some clinical factors was finally established and validated by two independent cohorts, where CDK6 and SGMS1-AS1 were significant to be independent prognostic factors. In addition, the identified co-expressed modules associated with the prognosis were overrepresented in the ceRNA network. Multiple enrichment analyses showed the important roles of the extracellular matrix components and cell division dysfunction in the invasion of MPM potentially. In summary, the prognostic ceRNA network of MPM was established and analyzed for the first time and these findings shed light on the function of ceRNAs and revealed the potential prognostic and therapeutic biomarkers of MPM.

Ligand-based Discovery of Novel Small Molecule Inhibitors of RON Receptor Tyrosine Kinase

BACKGROUND

RON (Recepteur d'Origine Nantais) receptor tyrosine kinase is a promising target for anti-cancer therapeutics. The aim of this study was to identify new RON inhibitors using virtual screening methods.

METHODS

To this end, a ligand-based virtual screening approach was employed for screening of ZINC database on the homology model of RON receptor. All the selected hits were inspected in terms of drug-likeness, ADME properties, and toxicity profiles. Ligand-based similarity searches along with further filtering criteria led to the identification of two compounds, TKI1 and TKI2 that were evaluated using in vitro cell-based RON inhibition assays.

RESULTS

The results showed that TKI1 and TKI2 could reduce phosphorylation of RON. Both compounds showed inhibitory activity of the downstream mTOR pathway with no apparent effects on other signaling mediators in a dose-dependent manner.

CONCLUSION

These compounds can provide a basis for developing novel anti-RON inhibitors applicable to cancer therapy using medicinal chemistry-oriented optimization strategies.