Dual Inhibition of Hedgehog and c-Met Pathways for Pancreatic Cancer Treatment

Recent advancements in the small-molecule drugs for hepatocellular carcinoma (HCC): Structure-activity relationships, pharmacological activities, and the clinical trials

BACKGROUND AND AIMS: Hepatocellular carcinoma (HCC) is one of the most common malignancies in the world and the sixth leading cause of cancer death worldwide, and it is urgent to find safe and effective drugs for treatment. As an important therapeutic method, small-molecule drugs are continually being updated to achieve improved therapeutic effects. The purpose of this study was to investigate the structural effects of various FDA-listed small-molecule drugs sorafenib, cabozantinib, lenvatinib, and regorafenib on the corresponding HCC targets and possible structural optimization methods, and to explore the mechanism for identifying potential therapeutic drugs that offer better efficacy and fewer side effects.

METHODS

The structure-activity relationship, pharmacological actions, and clinical applications of small-molecule drugs were reviewed by referencing MEDLINE, Web of Science, CNKI, and other databases, summarizing and integrating the relevant content.

RESULTS

The results showed that small-molecule drugs can inhibit HCC primarily by forming hydrogen bonds with Glu885, Asp1046, and Cys919 on the HCC target. HCC can be targeted by inhibiting the activation of multiple pathways, blocking the conduction of downstream signaling, and reducing the formation of tumor blood vessels. In general, small-molecule drugs primarily target four key receptors in HCC: VEGFR, PDGFR, EGFR, and FGFR, to achieve effective treatment.

CONCLUSIONS

By revealing their structure-activity relationships, pharmacological actions, and clinical trials, small-molecule drugs can offer broad prospects for the development of new medications.

Exosomal miRNA 16-5p/29a-3p from pancreatic cancer induce adipose atrophy by inhibiting adipogenesis and promoting lipolysis

Over 80% of the patients with pancreatic ductal adenocarcinoma (PDAC) have cachexia/wasting syndrome. Cachexia is associated with reduced survival, decreased quality of life, and higher metastasis rates. Here, we demonstrate that fat loss is the earliest feature of PDAC-exosome-induced cachexia. MicroRNA sequencing of exosomal components from normal and cancer-derived exosomes revealed enrichment of miR-16-5p, miR-21-5p, miR-29a-3p, and miR-125b-5p in serum exosomes of mice harboring PDAC and patients with PDAC. Further, miR-16-5p and miR-29a-3p inhibited adipogenesis through decreasing Erlin2 and Cmpk1 expression which downregulates C/EBPβ and PPARγ. Synergistically, miR-29a-3p promotes lipolysis through increasing ATGL expression by suppressing MCT1 expression. Furthermore, PDAC-exosomes deprived of miR-16-5p and miR-29a-3p fail to induce fat loss. Hence, miR-16-5p and miR-29a-3p exosomal miRs are essential for PDAC-induced fat loss. Thus, we unravel that PDAC induces adipose atrophy via exosomal miRs. This knowledge may provide new diagnostic and therapeutic strategies for PDAC-induced cachexia.

Recent advances in cancer-associated fibroblast: Biomarkers, signaling pathways, and therapeutic opportunities

ABSTRACT

Anti-cancer therapies usually focus on tumor cells, but non-tumor stromal components in the tumor microenvironment also play vital roles in tumor initiation and progression, which may be the prognostic factors and potential therapeutic targets. Cancer-associated fibroblasts (CAFs) are the essential component in the tumor environment, exhibiting high heterogeneity in their cell origin and phenotype with diverse functions that influence tumor angiogenesis, immune systems, and metabolism. Single-cell RNA sequencing and genetically engineered mouse models have increased our understanding of CAF diversity, and many subtypes have been defined. However, the precise functions of these subtypes need to be studied and validated. Studies of signaling pathways and epigenetic changes in CAFs facilitate understanding of the phenotypes of CAFs and the crosstalk between tumor cells and CAFs to provide potential therapeutic targets. Some clinical trials, including phase III trials targeting CAFs, have been performed recently. However, few of these trials have generated promising results, which indicates that the complexity of CAFs in the tumor microenvironment remains largely unknown, and in-depth investigations of CAFs should be performed. This review summarizes the research on CAFs, focusing on the heterogeneity of their phenotypes and functions, specific signaling pathways, and the therapeutic strategies involving CAFs. Additionally, we briefly discuss the current technologies commonly used in CAF studies and describe the challenges and future perspectives of CAF research.

Pancreatic Cancer Treatment Targeting the HGF/c-MET Pathway: The MEK Inhibitor Trametinib

Pancreatic cancer is characterized by fibrosis/desmoplasia in the tumor microenvironment, which is primarily mediated by pancreatic stellate cells and cancer-associated fibroblasts. HGF/c-MET signaling, which is instrumental in embryonic development and wound healing, is also implicated for its mitogenic and motogenic properties. In pancreatic cancer, this pathway, along with its downstream signaling pathways, is associated with disease progression, prognosis, metastasis, chemoresistance, and other tumor-related factors. Other features of the microenvironment in pancreatic cancer with the HGF/c-MET pathway include hypoxia, angiogenesis, metastasis, and the urokinase plasminogen activator positive feed-forward loop. All these attributes critically influence the initiation, progression, and metastasis of pancreatic cancer. Therefore, targeting the HGF/c-MET signaling pathway appears promising for the development of innovative drugs for pancreatic cancer treatment. One of the primary downstream effects of c-MET activation is the MAPK/ERK (Ras, Ras/Raf/MEK/ERK) signaling cascade, and MEK (Mitogen-activated protein kinase kinase) inhibitors have demonstrated therapeutic value in RAS-mutant melanoma and lung cancer. Trametinib is a selective MEK1 and MEK2 inhibitor, and it has evolved as a pivotal therapeutic agent targeting the MAPK/ERK pathway in various malignancies, including BRAF-mutated melanoma, non-small cell lung cancer and thyroid cancer. The drug's effectiveness increases when combined with agents like BRAF inhibitors. However, resistance remains a challenge, necessitating ongoing research to counteract the resistance mechanisms. This review offers an in-depth exploration of the HGF/c-MET signaling pathway, trametinib's mechanism, clinical applications, combination strategies, and future directions in the context of pancreatic cancer.

Targeting the hedgehog pathway in MET mutation cancers and its effects on cells associated with cancer development

The mutation of MET plays a crucial role in the initiation of cancer, while the Hedgehog (Hh) pathway also plays a significant role in cell differentiation and the maintenance of tumor stem cells. Conventional chemotherapy drugs are primarily designed to target the majority of cell populations within tumors rather than tumor stem cells. Consequently, after a brief period of remission, tumors often relapse. Moreover, the exclusive targeting of tumor stemness cell disregards the potential for other tumor cells to regain stemness and acquire drug resistance. As a result, current drugs that solely target the HGF/c-MET axis and the Hh pathway demonstrate only moderate efficacy in specific types of cancer. Mounting evidence indicates that these two pathways not only play important roles in cancer but also exert significant influence on the development of resistance to single-target therapies through the secretion of their own ligands. In this comprehensive review, we analyze and compare the potential impact of the Hh pathway on the tumor microenvironment (TME) in HGF/c-MET-driven tumor models, as well as the interplay between different cell types. Additionally, we further substantiate the potential and necessity of dual-pathway combination therapy as a critical target in MET addicted cancer treatment. Video Abstract.

CLDN18.2 BiTE Engages Effector and Regulatory T Cells for Antitumor Immune Response in Preclinical Models of Pancreatic Cancer

BACKGROUND & AIMS

BiTE (bispecific T-cell engager) immune therapy has demonstrated clinical activity in multiple tumor indications, but its influence in the tumor microenvironment remains unclear. CLDN18.2 is overexpressed in solid tumors including gastric cancer (GC) and pancreatic ductal adenocarcinoma (PDAC), both of which are characterized by the presence of immunosuppressive cells, including regulatory T cells (Tregs) and few effector T cells (Teffs).

METHODS

We evaluated the activity of AMG 910, a CLDN18.2-targeted half-life extended (HLE) BiTE molecule, in GC and PDAC preclinical models and cocultured Tregs and Teffs in the presence of CLDN18.2-HLE-BiTE.

RESULTS

AMG 910 induced potent, specific cytotoxicity in GC and PDAC cell lines. In GSU and SNU-620 GC xenograft models, AMG 910 engaged human CD3+ T cells with tumor cells, resulting in significant antitumor activity. AMG 910 monotherapy, in combination with a programmed death-1 (PD-1) inhibitor, suppressed tumor growth and enhanced survival in an orthotopic Panc4.14 PDAC model. Moreover, Treg infusion enhanced the antitumor efficacy of AMG 910 in the Panc4.14 model. In syngeneic KPC models of PDAC, treatment with a mouse surrogate CLDN18.2-HLE-BiTE (muCLDN18.2-HLE-BiTE) or the combination with an anti-PD-1 antibody significantly inhibited tumor growth. Tregs isolated from mice bearing KPC tumors that were treated with muCLDN18.2-HLE-BiTE showed decreased T cell suppressive activity and enhanced Teff cytotoxic activity, associated with increased production of type I cytokines and expression of Teff gene signatures.

CONCLUSIONS

Our data suggest that BiTE molecule treatment converts Treg function from immunosuppressive to immune enhancing, leading to antitumor activity in immunologically "cold" tumors.

Discovery of anticancer agents with c-Met inhibitory potential by virtual and experimental screening of a chemical library

c-Met receptor tyrosine kinase has recently emerged as an important target with therapeutic implications in pancreatic cancer. In this study, we carried out a docking virtual screening on an in-house library of 441 synthesized compounds and selected the compounds with the best interactions with the c-Met protein to be subjected to experimental tests. Ten compounds belonging to 3 different classes of chemical structures were selected for this purpose and their antiproliferative effects were studied against 4 pancreatic ductal adenocarcinoma (PDAC) cell lines including AsPC-1, Suit-2, Panc-1 and Mia-Paca-2 cells, primary PDAC cells and also c-Met amplified EBC-1 cell line by sulforhodamine-B assay. Apoptosis induction was examined by Hoechst 33258 staining and annexin V-FITC/propidium iodide flow cytometric assay. The best compound was also assayed in three-dimensional cultures of AsPC-1 cells and its c-Met inhibitory potential was studied by immunoblotting and a homogenous time resolved fluorescence (HTRF) assay. The compound with a phenanthrotriazine hydrazinyl scaffold bearing nitrophenyl pendant (PhTH) was the most active derivative, with IC50 values in the range of 5-8 μM. This compound exerted antiproliferative effect against AsPC-1 cells also in the presence of hepatocyte growth factor (HGF). PhTH induced apoptosis, dose-dependently inhibited spheroid growth, inhibited c-Met activity in cell-free HTRF assay and also inhibited the phosphorylation of c-Met and its downstream effector ERK1/2 in AsPC-1 cells. Molecular docking and dynamics simulation and MM-PBSA analysis confirmed close interactions of PhTH with c-Met kinase domain. Some of the tested compounds in this study seem to be potential c-Met inhibitors with promising activities against PDAC cells.

Design, Synthesis, and Evaluation of New Mesenchymal–Epithelial Transition Factor (c-Met) Kinase Inhibitors with Dual Chiral Centers

A series of tepotinib derivatives with two chiral centers was designed, synthesized, and evaluated as anticancer agents. The optimal compound (R, S)-12a strongly exhibited antiproliferative activity against MHCC97H cell lines with an IC50 value of 0.002 μM, compared to tepotinib (IC50 = 0.013 μM). Mechanistic studies revealed that compound (R, S)-12a significantly inhibited c-Met activation, as well as the downstream AKT signaling pathway, and suppressed wound closure. Moreover, compound (R, S)-12a induced cellular apoptosis and cell cycle arrest at the G1 phase in a dose-dependent fashion.

Targeting hedgehog signaling in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains a leading cause of cancer related death. The urgent need for effective therapies is highlighted by the lack of adequate targeting. In PDAC, hedgehog (Hh) signaling is known to be aberrantly activated, which prompted the pathway as a possible target for effective treatment for PDAC patients. Unfortunately, specific targeting of upstream molecules within the Hh signaling pathway failed to bring clinical benefit. This led to the ongoing debate on Hh targeting as a therapeutic treatment for PDAC patients. Additionally, concurrent non-canonical activation routes also result in translocation of Gli transcription factors into the nucleus. Therefore, different downstream targets of the Hh signaling pathway were identified and evaluated in preclinical and clinical research. In this review we summarize the variety of Hh signaling antagonists in different preclinical models of PDAC. Furthermore, we discuss published and ongoing clinical trials that evaluated Hh antagonists and point out the current hurdles and future perspectives in the light of redesigning Hh-targeting therapies for the treatment of PDAC patients.

Molecular signatures of tumor progression in pancreatic adenocarcinoma identified by energy metabolism characteristics

BACKGROUND

In this study, we performed a molecular evaluation of primary pancreatic adenocarcinoma (PAAD) based on the comprehensive analysis of energy metabolism-related gene (EMRG) expression profiles.

METHODS

Molecular subtypes were identified by nonnegative matrix clustering of 565 EMRGs. An overall survival (OS) predictive gene signature was developed and internally and externally validated based on three online PAAD datasets. Hub genes were identified in molecular subtypes by weighted gene correlation network analysis (WGCNA) coexpression algorithm analysis and considered as prognostic genes. LASSO cox regression was conducted to establish a robust prognostic gene model, a four-gene signature, which performed better in survival prediction than four previously reported models. In addition, a novel nomogram constructed by combining clinical features and the 4-gene signature showed high-confidence clinical utility. According to gene set enrichment analysis (GSEA), gene sets related to the high-risk group participate in the neuroactive ligand receptor interaction pathway.

CONCLUSIONS

In summary, EMRG-based molecular subtypes and prognostic gene models may provide a novel research direction for patient stratification and trials of targeted therapies.

Mesenchymal Epithelial Transition Factor (MET): A Key Player in Chemotherapy Resistance and an Emerging Target for Potentiating Cancer Immunotherapy

The MET protein is a cell surface receptor tyrosine kinase predominately expressed in epithelial cells. Upon binding of its only known ligand, hepatocyte growth factor (HGF), MET homodimerizes, phosphorylates, and stimulates intracellular signalling to drive cell proliferation. Amplification or hyperactivation of MET is frequently observed in various cancer types and it is associated with poor response to conventional and targeted chemotherapy. More recently, emerging evidence also suggests that MET/HGF signalling may play an immunosuppressive role and it could confer resistance to cancer immunotherapy. In this review, we summarized the preclinical and clinical evidence of MET's role in drug resistance to conventional chemotherapy, targeted therapy, and immunotherapy. Previous clinical trials investigating MET-targeted therapy in unselected or MET-overexpressing cancers yielded mostly unfavourable results. More recent clinical studies focusing on MET exon 14 alterations and MET amplification have produced encouraging treatment responses to MET inhibitor therapy. The translational relevance of MET inhibitor therapy to overcome drug resistance in cancer patients is discussed.

The tumor microenvironment in pancreatic ductal adenocarcinoma: current perspectives and future directions

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal malignancies and is characterized by a unique tumor microenvironment (TME) consisting of an abundant stromal component. Many features contained with the PDAC stroma contribute to resistance to cytotoxic and immunotherapeutic regimens, as well as the propensity for this tumor to metastasize. At the cellular level, PDAC cells crosstalk with a complex mixture of non-neoplastic cell types including fibroblasts, endothelial cells, and immune cells. These intricate interactions fuel the progression and therapeutic resistance of this aggressive cancer. Moreover, data suggest the polarization of these cell types, in particular immune and fibroblast populations, dictate how PDAC tumors grow, metastasize, and respond to therapy. As a result, current research is focused on how to best target these populations to render tumors responsive to treatment. Herein, we summarize the cell populations implicated in providing a supporting role for the development and progression of PDAC. We focus on stromal fibroblasts and immune subsets that have been widely researched. We discuss factors which govern the phenotype of these populations and provide insight on how they have been targeted therapeutically. This review provides an overview of the tumor microenvironment and postulates that cellular and soluble factors within the microenvironment can be specifically targeted to improve patient outcomes.

Combinational blockade of MET and PD-L1 improves pancreatic cancer immunotherapeutic efficacy

BACKGROUND

Dysregulated expression and activation of receptor tyrosine kinases (RTKs) are associated with a range of human cancers. However, current RTK-targeting strategies exert little effect on pancreatic cancer, a highly malignant tumor with complex immune microenvironment. Given that immunotherapy for pancreatic cancer still remains challenging, this study aimed to elucidate the prognostic role of RTKs in pancreatic tumors with different immunological backgrounds and investigate their targeting potential in pancreatic cancer immunotherapy.

METHODS

Kaplan-Meier plotter was used to analyze the prognostic significance of each of the all-known RTKs to date in immune "hot" and "cold" pancreatic cancers. Gene Expression Profiling Interactive Analysis-2 was applied to assess the differential expression of RTKs between pancreatic tumors and normal pancreatic tissues, as well as its correlation with immune checkpoints (ICPs). One hundred and fifty in-house clinical tissue specimens of pancreatic cancer were collected for expression and correlation validation via immunohistochemical analysis. Two pancreatic cancer cell lines were used to demonstrate the regulatory effects of RTKs on ICPs by biochemistry and flow cytometry. Two in vivo models bearing pancreatic tumors were jointly applied to investigate the combinational regimen of RTK inhibition and immune checkpoint blockade for pancreatic cancer immunotherapy.

RESULTS

MET was identified as a pancreatic cancer-specific RTK, which is significantly associated with prognosis in both immune "hot" and "cold" pancreatic cancers. MET was observed to be highly upregulated in pancreatic cancer tissues, and positively correlated with PD-L1 levels. Elevated MET and PD-L1 expressions were closely associated with lymph node metastasis, tumor TNM stage, and overall survival in pancreatic cancer. Mechanistically, MET could interact with PD-L1, and maintain its expression level in multiple ways. MET deficiency was found to facilitate lymphocyte infiltration into pancreatic tumors. Finally, significant benefits of combining MET inhibition with PD-1/PD-L1 blockage were verified in both orthotopic and subcutaneous mouse models of pancreatic cancer.

CONCLUSIONS

This study systematically investigated the potential effectiveness of a novel pancreatic cancer immunotherapy targeting RTKs, and revealed the function of MET in PD-L1 regulation as well as the combined therapeutic efficacy of MET and PD-L1 in pancreatic cancer.

The Role of the Hedgehog Pathway in Chemoresistance of Gastrointestinal Cancers

The hedgehog pathway, which plays a significant role in embryonic development and stem cell regulation, is activated in gastrointestinal cancers. Chemotherapy is widely used in cancer treatment. However, chemoresistance becomes a substantial obstacle in cancer therapy. This review focuses on the recent advances in the hedgehog pathway's roles in drug resistance of gastrointestinal cancers and the novel drugs and strategies targeting hedgehog signaling.

Breaking the cycle: Targeting of NDRG1 to inhibit bi-directional oncogenic cross-talk between pancreatic cancer and stroma

Pancreatic cancer (PaCa) is characterized by dense stroma that hinders treatment efficacy, with pancreatic stellate cells (PSCs) being a major contributor to this stromal barrier and PaCa progression. Activated PSCs release hepatocyte growth factor (HGF) and insulin-like growth factor (IGF-1) that induce PaCa proliferation, metastasis and resistance to chemotherapy. We demonstrate for the first time that the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), is a potent inhibitor of the PaCa-PSC cross-talk, leading to inhibition of HGF and IGF-1 signaling. NDRG1 also potently reduced the key driver of PaCa metastasis, namely GLI1, leading to reduced PSC-mediated cell migration. The novel clinically trialed anticancer agent, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), which upregulates NDRG1, potently de-sensitized PaCa cells to ligands secreted by activated PSCs. DpC and NDRG1 also inhibited the PaCa-mediated activation of PSCs via inhibition of sonic hedgehog (SHH) signaling. In vivo, DpC markedly reduced PaCa tumor growth and metastasis more avidly than the standard chemotherapy for this disease, gemcitabine. Uniquely, DpC was selectively cytotoxic against PaCa cells, while "re-programming" PSCs to an inactive state, decreasing collagen deposition and desmoplasia. Thus, targeting NDRG1 can effectively break the oncogenic cycle of PaCa-PSC bi-directional cross-talk to overcome PaCa desmoplasia and improve therapeutic outcomes.

Lidocaine suppresses the malignant behavior of gastric cancer cells via the c-Met/c-Src pathway

The present study was designed to investigate the role and mechanism of action behind the action of lidocaine in gastric cancer cells. Lidocaine was tested for its potential role in affecting the viability of cells using Cell Counting Kit-8 (CCK-8) assays. It was found that there was a decreased MKN45 cell viability upon lidocaine treatment in a dose-dependent manner. Phosphorylated c-Met, phosphorylated c-Src, c-Met and c-Src levels were detected using western blotting following lidocaine or hepatocyte growth factor (HGF) intervention. It was found that the phosphorylation levels of c-Met and c-Src were markedly reduced by lidocaine treatment, with this effect being further relieved by the addition of HGF. Subsequently, whether lidocaine repressed the malignant biological properties of gastric cancer cells through the c-Met/c-Src axis was further investigated through the detection of epithelial-mesenchymal transition markers (N-caderin and vimentin), wound healing and transwell assay analysis. In addition, cell apoptosis and the levels of apoptosis-related proteins were determined using TUNEL and western blot assays, respectively. The results demonstrated that the malignant behavior of cells were notably repressed upon lidocaine treatment, but the addition of HGF markedly reversed these effects, indicating that the effects of lidocaine on supressing the malignant behaviour of cells could be mediated through the c-Met/c-Src axis. Subsequently, whether lidocaine affected the sensitivity of cells to cisplatin or 5-FU was analyzed using a CCK-8 assay. Enhanced sensitivity of cells to cisplatin or 5-FU was observed when treated in combination with lidocaine. The present study concluded that the involvement of the c-Met/c-Src pathway in the biological behaviour of MKN45 cells was mediated by lidocaine. Therefore, lidocaine may have the potential to suppress the malignant behaviour and proliferation of gastric cancer cells.

Combination of HGF/MET-targeting agents and other therapeutic strategies in cancer

MET receptor has emerged as a druggable target across several human cancers. Agents targeting MET and its ligand hepatocyte growth factor (HGF) including small molecules such as crizotinib, tivantinib and cabozantinib or antibodies including rilotumumab and onartuzumab have proven their values in different tumors. Recently, capmatinib was approved for treatment of metastatic lung cancer with MET exon 14 skipping. In this review, we critically examine the current evidence on how HGF/MET combination therapies may take advantage of synergistic effects, overcome primary or acquired drug resistance, target tumor microenvironment, modulate drug metabolism or tackle pharmacokinetic issues. Preclinical and clinical studies on the combination of HGF/MET-targeted agents with conventional chemotherapeutics or molecularly targeted treatments (including EGFR, VEGFR, HER2, RAF/MEK, and PI3K/Akt targeting agents) and also the value of biomarkers are examined. Our deeper understanding of molecular mechanisms underlying successful pharmacological combinations is crucial to find the best personalized treatment regimens for cancer patients.

Sensitivity of pancreatic cancer cells to chemotherapeutic drugs, signal transduction inhibitors and nutraceuticals can be regulated by WT-TP53

Pancreatic ductal adenocarcinoma (PDAC) is a highly metastatic malignancy. Approximately 85% of pancreatic cancers are classified as PDACs. The survival of PDAC patients is very poor and only 5-10% of patients survive 5 years after diagnosis. Mutations at the KRAS and TP53 gene are frequently observed in PDAC patients. The PANC-28 cell line lacks wild-type (WT) TP53. In the following study, we have investigated the effects of restoration of WT TP53 activity on the sensitivity of PANC-28 pancreatic cancer cells to various drugs which are used to treat PDAC patients as well as other cancer patients. In addition, we have examined the effects of signal transduction inhibitors which target critical pathways frequently deregulated in cancer. The effects of the anti-diabetes drug metformin and the anti-malarial drug chloroquine were also examined as these drugs may be repurposed to treat other diseases. Finally, the effects of certain nutraceuticals which are used to treat various ailments were also examined. Introduction of WT-TP53 activity in PANC-28 PDAC cells, can increase their sensitivity to various drugs. Attempts are being made clinically to increase TP53 activity in various cancer types which will often inhibit cell growth by multiple mechanisms.

The role of MET in chemotherapy resistance

Chemotherapy remains the mainstay of treatment in the majority of solid and haematological malignancies. Resistance to cytotoxic chemotherapy is a major clinical problem and substantial research is ongoing into potential methods of overcoming this resistance. One major target, the receptor tyrosine kinase MET, has generated increasing interest with multiple clinical trials in progress. Overexpression of MET is frequently observed in a range of different cancers and is associated with poor prognosis. Studies have shown that MET promotes resistance to targeted therapies, including those targeting EGFR, BRAF and MEK. More recently, several reports suggest that MET also contributes to cytotoxic chemotherapy resistance. Here we review the preclinical evidence of MET's role in chemotherapy resistance, the mechanisms by which this resistance is mediated and the translational relevance of MET inhibitor therapy for patients with chemotherapy resistant disease.

Computational and in vitro characterization of ICY-5: A potential candidate promoting mitochondrial apoptosis via the c-MET and STAT3 pathways

Targeted chemotherapy remains the primary choice in controlling various forms of breast cancer (BC) due to its heterogenous gene expressions in various subtypes. In silico and in vitro evaluation of ICY-5, a novel arylidene analogue against c-MET, was performed. ICY-5 exhibited a docking score of -9.6 kcal/mol in inactive conformation and, - 8.6 kcal/mol in active conformation for c-MET. ICY-5 inhibited c-MET enzyme with an IC₅₀ of 34.34 nM. The compound effectively inhibited MDA-MB 231 and MCF-7 cell proliferation, with GI₅₀ values of 62.61 and 75.31 nM, respectively, and hepatocyte growth factor (HGF)/R c-MET phosphorylation with IC₅₀ s of 71.41 and 83.77 nM, respectively. ICY-5 dose-dependently inhibited HGF-induced transmigration, cell scattering, invasion and altered cell cycle. An increase in apoptotic populations of these cells, with a dose-dependent decease in phosphorylation of STAT3 protein was observed. Furthermore, ICY-5 upregulated the caspase-3, caspase-9, Bcl-2-associated X and survivin, and downregulated Bcl-2, vascular endothelial growth factor, matrix metalloproteinase-2 (MMP-2), and MMP-9 in both BC cell lines. In summary, ICY-5 exhibited excellent efficacy in BC cells, targeting c-MET/SAT-3-mediated mitochondrial apoptosis. Further research will be required to ascertain ICY-5 suitability as a targeted chemotherapeutic against multiple forms of BC.

Phase 1 trial of Vismodegib and Erlotinib combination in metastatic pancreatic cancer

BACKGROUND/OBJECTIVES

Interplay between the Hedgehog (HH) and epidermal growth factor receptor (EGFR) pathways modulating the outcome of their signaling activity have been reported in various cancers including pancreatic ductal adenocarcinoma (PDAC). Therefore, simultaneous targeting of these pathways may be clinically beneficial. This Phase I study combined HH and EGFR inhibition in metastatic PDAC patients.

METHODS

Combined effects of HH and EGFR inhibition using Vismodegib and Erlotinib with or without gemcitabine in metastatic solid tumors were assessed by CT. Another cohort of patients with metastatic PDAC was evaluated by FDG-PET and tumor biopsies-derived biomarkers.

RESULTS

Treatment was well tolerated with the maximum tolerated dose cohort experiencing no grade 4 toxicities though 25% experienced grade 3 adverse effects. Recommended phase II dose of Vismodegib and Erlotinib were each 150 mg daily. No tumor responses were observed although 16 patients achieved stable disease for 2-7 cycles. Paired biopsy analysis before and after first cycle of therapy in PDAC patients showed reduced GLI1 mRNA, phospho-GLI1 and associated HH target genes in all cases. However, only half of the cases showed reduced levels of desmoplasia or changes in fibroblast markers. Most patients had decreased phospho-EGFR levels.

CONCLUSIONS

Vismodegib and Erlotinib combination was well-tolerated although overall outcome in patients with metastatic PDAC was not significantly impacted by combination treatment. Biomarker analysis suggests direct targets inhibition without significantly affecting the stromal compartment. These findings conflict with pre-clinical mouse models, and thus warrant further investigation into how upstream inhibition of these pathways is circumvented in PDAC.

Strategies in Developing Immunotherapy for Pancreatic Cancer: Recognizing and Correcting Multiple Immune "Defects" in the Tumor Microenvironment

With the advent of cancer immunotherapies, significant advances have been made in the treatment of many tumor types including melanoma, lung cancer, squamous cell carcinoma of the head and neck, renal cell carcinoma, bladder cancer, etc. However, similar success has not been observed with the treatment of pancreatic cancer and all other immunogenic “cold” tumors. This prompts the need for a better understanding of the complexity of the cold tumor microenvironment (TME) of pancreatic cancer and what are truly the “defects” in the TME making the cancer unresponsive to immune checkpoint inhibitors. Here we discuss four major immune defects that can be recognized in pancreatic cancer, including lack of high-quality effector intratumoral T cells, heterogeneous dense stroma as a barrier to effector immune cells infiltrating into the tumor, immunosuppressive tumor microenvironment, and failure of the T cells to accomplish tumor elimination. We also discuss potential strategies for pancreatic cancer treatment that work by correcting these immune defects.

Exploring Signaling Pathways and Pancreatic Cancer Treatment Approaches Using Genetic Models

Despite available treatment options, the overall survival rates of pancreatic cancer patients remain dismal. Multiple counter-regulatory pathways have been identified and shown to be involved in interfering with the efficacy of therapeutic agents. In addition, various known genetic alterations in the cellular signaling pathways have been implicated in affecting the growth and progression of pancreatic cancer. Nevertheless, the significance of other unknown pathways is yet to be explored, which provides the rationale for the intervention of new approaches. Several experimental genetic models have been explored to define the impact of key signaling cascades, and their mechanisms in the pathophysiology as well as treatment approaches of pancreatic cancer. The current review highlights the recent updates, and significance of such genetic models in the therapeutic efficacy of anti-tumor agents including the standard chemotherapeutic agents, natural products, cell signaling inhibitors, immunebased therapies and the combination of these approaches in pancreatic cancer.

Novel Targets in Pancreatic Cancer Therapy - Current Status and Ongoing Translational Efforts

Pancreatic ductal adenocarcinoma (PDAC, pancreatic cancer) carries one of the poorest overall prognoses of all human malignancies known to date. Despite the introduction of novel therapeutic regimens, the outcome has not markedly improved over the past decades, the incidence rates are almost identical to the mortality rates, and PDAC is projected to soon become the second most common cause of cancer-related mortality in Western countries. Despite this clear medical need to develop novel therapeutic strategies against this dire malady, this need has so far not been addressed with sufficient institutional attention and support in terms of research funding and strategical programs. Given the still growing life expectancy and projected demographic changes with a growing proportion of senior citizens in many European societies, this discrepancy is likely to become even more pressing in the future. This article provides a brief overview of ongoing preclinical efforts to identify novel targets and, based on this, to develop novel strategies to treat advanced pancreatic cancer and improve survival and the quality of life of patients suffering from this malignancy.

Function of the c-Met receptor tyrosine kinase in carcinogenesis and associated therapeutic opportunities

c-Met is a receptor tyrosine kinase belonging to the MET (MNNG HOS transforming gene) family, and is expressed on the surfaces of various cells. Hepatocyte growth factor (HGF) is the ligand for this receptor. The binding of HGF to c-Met initiates a series of intracellular signals that mediate embryogenesis and wound healing in normal cells. However, in cancer cells, aberrant HGF/c-Met axis activation, which is closely related to c-Met gene mutations, overexpression, and amplification, promotes tumor development and progression by stimulating the PI3K/AKT, Ras/MAPK, JAK/STAT, SRC, Wnt/β-catenin, and other signaling pathways. Thus, c-Met and its associated signaling pathways are clinically important therapeutic targets. In this review, we elaborate on the molecular structure of c-Met and HGF and the mechanism through which their interaction activates the PI3K/AKT, Ras/MAPK, and Wnt signaling pathways. We also summarize the connection between c-Met and RON and EGFR, which are also receptor tyrosine kinases. Finally, we introduce the current therapeutic drugs that target c-Met in primary tumors, and their use in clinical research.

Pancreatic Cancer: Molecular Characterization, Clonal Evolution and Cancer Stem Cells

Pancreatic Ductal Adenocarcinoma (PDAC) is the fourth most common cause of cancer-related death and is the most lethal of common malignancies with a five-year survival rate of <10%. PDAC arises from different types of non-invasive precursor lesions: intraductal papillary mucinous neoplasms, mucinous cystic neoplasms and pancreatic intraepithelial neoplasia. The genetic landscape of PDAC is characterized by the presence of four frequently-mutated genes: KRAS, CDKN2A, TP53 and SMAD4. The development of mouse models of PDAC has greatly contributed to the understanding of the molecular and cellular mechanisms through which driver genes contribute to pancreatic cancer development. Particularly, oncogenic KRAS-driven genetically-engineered mouse models that phenotypically and genetically recapitulate human pancreatic cancer have clarified the mechanisms through which various mutated genes act in neoplasia induction and progression and have led to identifying the possible cellular origin of these neoplasias. Patient-derived xenografts are increasingly used for preclinical studies and for the development of personalized medicine strategies. The studies of the purification and characterization of pancreatic cancer stem cells have suggested that a minority cell population is responsible for initiation and maintenance of pancreatic adenocarcinomas. The study of these cells could contribute to the identification and clinical development of more efficacious drug treatments.