In-silico based identification of phytochemicals from Houttuynia cordata Thunb. as potential inhibitors for overexpressed HER2 and VEGFR2 cancer genes

Human epidermal growth factor receptor2 (HER2) and Vascular endothelial growth factor receptor2 (VEGFR2) - a tyrosine kinase receptors play a key role in breast and stomach cancers. The overexpression of HER2 and VEGFR2 genes increases the number of HER2 and VEGFR2 in the cell which initiates breast and stomach cancer respectively. The phytochemicals from traditional medicinal herb Houttuynia cordata Thunb. are reported to possess anti-inflammatory and anti-cancer potential. However, isolation of phytochemicals from this herb is fraught with uncertainly and time-consuming. Here, a molecular docking approach provides probable binding affinities between the receptors and phytochemicals (ligands) which initiate the first step of anticancer drug discovery and development. In the present study, In-silico docking approaches were used to identify the top-hit phytochemicals from H. cordata as potential inhibitors for overexpressed HER2 (breast) and VEGFR2 (stomach) cancer genes. A total of 100 biologically active phytochemicals from H. cordata were screened and docked against the ligand-binding pocket of HER2 and VEGFR2 kinase domains. Docking results revealed only a few phytochemicals (molecules) which appropriately fit into the ligand-binding pocket with higher binding affinity than the natural ATP ligand. A competitive docking was used to ascertain the top-hit phytochemicals that bind perfectly to the ATP ligand-binding pocket. Among the top-hit phytochemicals docked from H. cordata, the β-sitosterol and Quercetin showed highest binding affinity towards HER2 and VEGFR2 receptors using both hydrogen and hydrophobic interactions. This study confirmed β-sitosterol and Quercetin as potential drug candidates against breast and stomach cancer.Communicated by Ramaswamy H. Sarma.

Gastric cancer management: Kinases as a target therapy

The molecular diagnostics revolution has reshaped the practice of oncology by facilitating the identification of genetic, epigenetic and proteomic modifications correlated with cancer, thus delineating 'oncomaps' for various cancer types. These advances have enhanced our understanding of gastric cancer, one of the most fatal diseases worldwide, and culminated in the approval of novel molecular therapies such as trastuzumab. Gastric tumours display recurrent aberrations in key kinase oncogenes such as Her2, epidermal growth factor receptor (EGFR), PI3K, mTOR or c-Met, suggesting that these receptors are amenable to inhibition using specific drug agents. In this review, we examine the mutational landscape of gastric cancer, the use of kinase inhibitors as targeted therapies in gastric tumours and the clinical trials underway for novel inhibitors, highlighting successes, failures and future directions.

Targeting c-MET in gastrointestinal tumours: rationale, opportunities and challenges

Data from many preclinical studies, including those using cellular models of colorectal, gastric, gastro-oesophageal and gastro-oesophageal junction cancers, indicate that the hepatocyte growth factor (HGF)-hepatocyte growth factor receptor (c-MET) pathway is vital for the growth, survival and invasive potential of gastrointestinal cancers. Following the availability of data from these various studies, and data on c-MET expression as a biomarker that indicates a poor prognosis in patients with gastrointestinal cancer and increased c-MET expression, inhibitors targeting this pathway have entered the clinic in the past decade. However, the design of clinical trials that incorporate the use of HGF/c-MET inhibitors in their most appropriate genetic and molecular context remains crucial. Recognizing and responding to this challenge, the European Commission funded Framework 7 MErCuRIC programme is running a biomarker-enriched clinical trial investigating the efficacy of combined c-MET/MEK inhibition in patients with RAS-mutant or RAS-wild-type metastatic colorectal cancer with aberrant c-MET expression. The design of this trial enables the continued refinement of the predictive biomarker and co-development of companion diagnostics. In this Review, we focus on advances in our understanding of inhibition of the HGF/c-MET pathway in patients with gastro-intestinal cancers, the prominent challenges facing the clinical translation and implementation of agents targeting HGF/c-MET, and discuss the various efforts, and associated obstacles to the discovery and validation of biomarkers that will enable patient stratification in this context.

Unravelling the pharmacologic opportunities and future directions for targeted therapies in gastro-intestinal cancers Part 1: GI carcinomas

Until the 1990s, cytotoxic chemotherapy has been the cornerstone of medical therapy for gastrointestinal (GI) cancers. Better understanding of the molecular biology of cancer cell has led to the therapeutic revolution of targeted therapies, i.e. monoclonal antibodies or small molecule inhibitors directed against proteins that are specifically overexpressed or mutated in cancer cells. These agents being more specific to cancer cells were expected to be less toxic than cytotoxic agents. Targeted agents have provided clinical benefit in many GI cancer types. For example, antiangiogenics and anti-EGFR therapies have significantly improved survival of patients affected by metastatic colorectal cancer and have deeply changed the therapeutic strategy in this disease. However, their effects have sometimes been disappointing, due to intrinsic or acquired resistance mechanisms (e.g., RAS mutation for anti-EGFR therapies), or to an activity restricted to some tumour settings (e.g., lack of activity in other cancer types, or on the microscopic residual disease in adjuvant setting). Many studies are negative in overall population but positive in some specific patient subgroups (e.g., trastuzumab in HER2-positive gastric cancer), illustrating the importance of patient selection and early identification of predictive biomarkers of response to these therapies. We propose a comprehensive two-part review providing a panoramic approach of the successes and failures of targeted agents in GI cancers to unravel the pharmacologic opportunities and future directions for these agents in GI oncology. In this first part, we will focus on adenocarcinomas and squamous cell carcinomas, for which targeted therapies are mostly used in combination with chemotherapy.

Targeted Therapies for Advanced Oesophagogastric Cancer: Recent Progress and Future Directions

The genomic landscape of oesophagogastric (OG) cancer is highly complex. The recent elucidation of some of the pathways involved has suggested a number of novel targets for therapy. This therapy is urgently required as with conventional chemotherapy regimens patients with advanced OG cancer still have a median overall survival of under a year. This review outlines the rationale for the current treatment of OG cancer with chemotherapy and describes both previously conducted and ongoing clinical trials of novel agents in this area. The targets and associated treatments discussed include HER-2, EGFR, VEGF, c-Met, FGFR-2, PI3K, mTOR andIGF-1. To date only two targeted treatments, trastuzumab and ramucirumab, have become part of the treatment paradigm for OG cancer, partly due to difficulties in defining predictive biomarkers in this disease. However, there are a number of promising drugs in the pipeline and this article seeks to describe these and other potential novel approaches including targeting DNA repair deficiencies and the immune system.

Gastric biomarkers: a global review

BACKGROUND

Gastric cancer is an aggressive disease with a poor 5-year survival and large global burden of disease. The disease is biologically and genetically heterogeneous with a poorly understood carcinogenesis at the molecular level. Despite the many prognostic, predictive, and therapeutic biomarkers investigated to date, gastric cancer continues to be detected at an advanced stage with resultant poor clinical outcomes.

MAIN BODY

This is a global review of gastric biomarkers with an emphasis on HER2, E-cadherin, fibroblast growth factor receptor, mammalian target of rapamycin, and hepatocyte growth factor receptor as well as sections on microRNAs, long noncoding RNAs, matrix metalloproteinases, PD-L1, TP53, and microsatellite instability.

CONCLUSION

A deeper understanding of the pathogenesis and biological features of gastric cancer, including the identification and characterization of diagnostic, prognostic, predictive, and therapeutic biomarkers, hopefully will provide improved clinical outcomes.

c-Met targeting in advanced gastric cancer: An open challenge

Despite significant improvements in systemic chemotherapy over the last two decades, the prognosis of patients with advanced gastric and gastroesophageal junction adenocarcinoma (GC) remains poor. Because of molecular heterogeneity, it is essential to classify tumors based on the underlying oncogenic pathways and to develop targeted therapies acting on individual tumors. High-quality research and advances in technology have contributed to the elucidation of molecular pathways underlying disease progression and have stimulated many clinical studies testing target therapies in an advanced disease setting. In particular, strong preclinical evidence for the aberrant activation of the HGF/c-Met signaling pathways in GC cancers exists. This review will cover the c-Met pathway, the mechanisms of c-Met activation and the different strategies of its inhibition. Next, we will focus on the current state of the art in the clinical evaluation of c-Met-targeted therapies and the description of ongoing randomized trials with the idea that in this disease, high quality translational research to identify and validate biomarkers is a priority task.

Emerging tyrosine kinase inhibitors for esophageal cancer

INTRODUCTION

Because of the poor prognosis for patients with esophagogastric cancers (EGCs), increasing attention has focused on targeted agents.

AREAS COVERED

Targets include epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), Her2, mammalian target of rapamycin (mTOR), and MET. We briefly discuss preclinical data and the rationale for targeting these pathways and summarize the results of clinical trials of tyrosine kinase inhibitors (TKIs) against these targets.

EXPERT OPINION

While anti-EGFR therapy has been extensively investigated, completed Phase III trials suggest that this is not a promising target. A Phase III trial of an anti-VEGF antibody failed to show improvement in the primary endpoint of overall survival but response rates and progression-free survival were improved; a Phase III trial of an anti-VEGF receptor 2 antibody in second-line therapy did show improved survival. As such, Phase II and III evaluations of anti-VEGF TKIs are ongoing. The only Food and Drug Administration-approved targeted therapy in EGC is trastuzumab, an anti-Her2 antibody, and the results of a Phase III evaluation of lapatinib, an anti-Her2 TKI, are awaited. Phase III evaluation of an mTOR inhibitor has been negative. Finally, MET inhibition appears to have significant clinical potential and early testing of MET TKIs is underway.

Molecular targeted agents for gastric cancer: a step forward towards personalized therapy

Gastric cancer (GC) represents a major cancer burden worldwide, and remains the second leading cause of cancer-related death. Due to its insidious nature, presentation is usually late and often carries a poor prognosis. Despite having improved treatment modalities over the last decade, for most patients only modest improvements have been seen in overall survival. Recent progress in understanding the molecular biology of GC and its signaling pathways, offers the hope of clinically significant promising advances for selected groups of patients. Patients with Her-2 overexpression or amplification have experienced benefit from the integration of monoclonal antibodies such as trastuzumab to the standard chemotherapy. Additionally, drugs targeting angiogenesis (bevacizumab, sorafenib, sunitinib) are under investigation and other targeted agents such as mTOR inhibitors, anti c-MET, polo-like kinase 1 inhibitors are in preclinical or early clinical development. Patient selection and the development of reliable biomarkers to accurately select patients most likely to benefit from these tailored therapies is now key. Future trials should focus on these advances to optimize the treatment for GC patients. This article will review recent progress and current status of targeted agents in GC.

Targeted therapies in the treatment of gastric cancer

Gastric cancer (GC) constitutes a major cause of cancer deaths worldwide. Recent improvements in both surgical techniques and adjuvant and neoadjuvant radiotherapy and chemotherapy approaches have increased the survival of patients with loco-regional disease. However most patients with GC have advanced disease either at diagnosis or at follow up. Despite recent advances in the treatment of advanced disease, these patients still have poor outcomes. An emerging understanding of the molecular pathways that characterize cell growth, cell cycle, apoptosis, angiogenesis and invasion has provided novel targets in cancer therapy. In this review we describe the current status of targeted therapies in the treatment of GC. These therapeutic strategies include epidermal growth factor receptor inhibitors, antiangiogenic agents, cell cycle inhibitors, apoptosis, promoters and matrix metalloproteinases inhibitors.

Phase I and II clinical trials for gastric cancer

Gastric cancer remains a global public health problem with considerable heterogeneity in pathogenesis and clinical presentation across geographic regions. Improved understanding of the molecular biology of this disease has opened avenues for targeted intervention. An individualized treatment approach is required for optimal management of this cancer. Overcoming resistance to therapy requires combining targeted agents with the traditional options of chemotherapy/radiation therapy, and also targeting more than 1 pathway of carcinogenesis at a time. Encouraging molecular hypothesis and biomarker-driven trials will lead to improved patient outcomes and may eventually enable the therapeutic nihilism associated with gastric cancer to be overcome.

Targeted therapy in the management of advanced gastric cancer: are we making progress in the era of personalized medicine?

BACKGROUND

Gastric cancer is one of the leading causes of cancer death. With greater understanding of the molecular basis of carcinogenesis, targeted agents have led to a modest improvement in the outcome of advanced gastric cancer (AGC) patients.

METHODS AND RESULTS

We conducted an overview of the published evidence regarding the use of targeted therapy in AGC patients. Thus far, the human epidermal growth factor receptor (HER) pathway, angiogenic pathway, and phosphatidylinositol-3-kinase (PI3K)-Akt-mammalian target of rapamycin pathway have emerged as potential avenues for targeted therapy in AGC patients. The promising efficacy results of the Trastuzumab for Gastric Cancer trial led to the approved use of trastuzumab-based therapy as first-line treatment for patients with HER-2+ AGC. On the other hand, the Avastin® in Gastric Cancer trial evaluating bevacizumab in combination with chemotherapy did not meet its primary endpoint of a longer overall survival duration despite a significantly higher response rate and longer progression-free survival time in patients in the bevacizumab arm. Phase III data are awaited for other targeted agents, including cetuximab, panitumumab, lapatinib, and everolimus.

CONCLUSION

Recent progress in targeted therapy development for AGC has been modest. Further improvement in the outcome of AGC patients will depend on the identification of biomarkers in different patient populations to facilitate the understanding of gastric carcinogenesis, combining different targeted agents with chemotherapy, and unraveling new molecular targets for therapeutic intervention.

Targeted therapies for gastric cancer: current status

Gastric cancer represents one of the most common cancers internationally. Unfortunately the majority of patients still present at an advanced stage, and despite advances in diagnostic and treatment strategies, outcomes still remain poor with high mortality rates despite a decline in incidence. Whilst the utility of classical chemotherapy agents has been explored thoroughly (and continues to be investigated, alone or in various combinations), advances have been slow and the efficacy of these agents has reached a plateau. As such, the focus of recent study has shifted toward developing a greater understanding of the molecular biology of carcinogenesis and the cancer cell phenotype, and, in turn, the development of rationally designed drugs that target molecular aberrancies in signal transduction pathways specific to gastric cancer. These targets include circulating growth and angiogenic factors, cell surface receptors, and other molecules that comprise downstream intracellular signalling pathways, including receptor tyrosine kinases. Therapeutic advances in this area significantly lag behind other solid organ malignancies such as breast and colorectal cancer. This article reviews the role of targeted therapies in gastric cancer, including rationale and mechanism of action, current and emerging data, as single-agent therapy or in combination regimens. A recently published randomized phaseIII trial supporting the use of trastuzumab, an anti-human epidermal growth factor receptor 2 (HER2)/neu monoclonal antibody, in a selected population of patients is discussed. Therapies that have been evaluated in phase II trials are also reviewed, as well as promising new therapies currently being investigated in preclinical or phase I studies. There is optimism that targeted therapies, whether as single-agent therapy or in combination with traditional therapies, including chemotherapy, radiotherapy and surgery, may yet have an impact on improvement of the overall prognosis of gastric cancer.

Antitumor activity of SNX-2112, a synthetic heat shock protein-90 inhibitor, in MET-amplified tumor cells with or without resistance to selective MET Inhibition

PURPOSE

Heat shock protein-90 (HSP-90), a molecular chaperone required by numerous oncogenic kinases [e.g., HER-2, epidermal growth factor receptor (EGFR), Raf-1, v-Src, and AKT] for conformational stability, has attracted wide interest as a novel target for cancer therapy. HSP-90 inhibition induces degradation of HSP-90 client proteins, leading to a combinatorial inhibition of multiple oncogenic signaling pathways with consecutive growth arrest and apoptosis. MET, a tyrosine kinase that is constitutively active in tumor cells with MET oncogene amplification, has recently been identified as another HSP-90 client.

EXPERIMENTAL DESIGN

The aim of our study was to assess the efficacy of SNX-2112, a synthetic HSP-90 inhibitor, in 3 different MET-amplified tumor cell lines (GTL-16, MKN-45, and EBC-1) as well as PR-GTL-16 cells, a GTL-16 subline selected for resistance to the highly selective MET kinase inhibitor PHA-665752.

RESULTS

In all cell lines, SNX-2112 led to degradation of MET, HER-2, EGFR, and AKT, as well as abrogation of Ras/Raf/MEK/MAPK and PI3K/AKT signaling, followed by complete cell cycle arrest. SNX-5542, an orally bioavailable prodrug of SNX-2112, displayed significant antitumor efficacy in vivo in nude mice bearing MET-amplified tumor xenografts. Importantly, HSP-90 inhibition maintained its antitumor efficacy in PR-GTL-16 cells both in vitro and in vivo, suggesting that HSP-90 inhibition could be a particularly valuable strategy in MET-amplified tumors that have acquired resistance to MET kinase inhibition.

CONCLUSIONS

Our study provides evidence for the efficacy of HSP-90 inhibition in MET-amplified cancer cells, particularly when MET kinase inhibitor resistance has emerged.

Foretinib (GSK1363089), an orally available multikinase inhibitor of c-Met and VEGFR-2, blocks proliferation, induces anoikis, and impairs ovarian cancer metastasis

PURPOSE

Currently, there are no approved targeted therapies for the treatment of ovarian cancer, despite the fact that it is the most lethal gynecological malignancy. One proposed target is c-Met, which has been shown to be an important prognostic indicator in a number of malignancies, including ovarian cancer. The objective of this study was to determine whether an orally available multikinase inhibitor of c-Met and vascular endothelial growth factor receptor-2 (foretinib, GSK1363089) blocks ovarian cancer growth.

EXPERIMENTAL DESIGN

The effect of foretinib was tested in a genetic mouse model of endometrioid ovarian cancer, several ovarian cancer cell lines, and an organotypic 3D model of the human omentum.

RESULTS

In the genetic mouse model, treatment with foretinib prevented the progression of primary tumors to invasive adenocarcinoma. Invasion through the basement membrane was completely blocked in treated mice, whereas in control mice, invasive tumors entirely replaced the normal ovary. In 2 xenograft mouse models using human ovarian cancer cell lines, the inhibitor reduced overall tumor burden (86% inhibition, P < 0.0001) and metastasis (67% inhibition, P < 0.0001). The mechanism of inhibition by foretinib involved (a) inhibition of c-Met activation and downstream signaling, (b) reduction of ovarian cancer cell adhesion, (c) a block in migration and invasion, (d) reduced proliferation mediated by a G(2)-M cell-cycle arrest, and (e) induction of anoikis.

CONCLUSIONS

This study shows that foretinib blocks tumorigenesis and reduces invasive tumor growth in different models of ovarian cancer by affecting several critical tumor functions. We believe that it provides a rationale for the further clinical development of foretinib for the treatment of ovarian cancer.

MET expression and amplification in patients with localized gastric cancer

BACKGROUND

MET, the receptor for hepatocyte growth factor, has been proposed as a therapeutic target in gastric cancer. This study assessed the incidence of MET expression and gene amplification in tumors of Western patients with gastric cancer.

METHODS

Tumor specimens from patients enrolled on a preoperative chemotherapy study (NCI 5700) were examined for the presence of MET gene amplification by FISH, MET mRNA expression by quantitative PCR, MET overexpression by immunohistochemistry (IHC), and for evidence of MET pathway activation by phospho-MET (p-MET) IHC.

RESULTS

Although high levels of MET protein and mRNA were commonly encountered (in 63% and 50% of resected tumor specimens, respectively), none of these tumors had MET gene amplification by FISH, and only 6.6% had evidence of MET tyrosine kinase activity by p-MET IHC.

CONCLUSIONS

In this cohort of patients with localized gastric cancer, the presence of high MET protein and RNA expression does not correlate with MET gene amplification or pathway activation, as evidenced by the absence of amplification by FISH and negative p-MET IHC analysis.

IMPACT

This article shows a lack of MET amplification and pathway activation in a cohort of 38 patients with localized gastric cancer, suggesting that MET-driven gastric cancers are relatively rare in Western patients.

Targeted therapies for metastatic esophagogastric cancer

The prognosis and long-term survival for patients with metastatic esophagogastric cancer (EGC) is poor. Historically, the mainstay of treatment has been combination chemotherapy. More recently, a number of targeted therapies have been developed and are being studied with the goal of improving response rate and survival in patients with metastatic EGC. To date, the only targeted therapy which has been clinically approved is trastuzumab which targets the HER2/Neu oncogene. However, only a small group of patients with EGCs are HER2 amplified, and there are other important targets/pathways which play a role in the development of these cancers that are currently being studied. With the identification of these other clinically relevant pathways, it is anticipated that several other therapies will be approved in the future.

Novel perspectives for the treatment of gastric cancer: from a global approach to a personalized strategy

Although recent advances have been made, surgery still remains the mainstay of any curative treatment for gastric cancer patients, with radical gastrectomy representing the procedure of choice. However, patients with locally advanced disease show high rates of locoregional or distant recurrence even after potentially curative resections. According to global results presented in the setting of locally advanced resectable gastric carcinoma, perioperative chemotherapy may be considered a valuable option. On the other hand, clinical trials for advanced gastric cancer seem to suggest that a limit in efficacy has been reached for standard chemotherapy. Interesting data are expected from the development of targeted agents that, similarly to other cancer sites, showed appealing results in gastric cancer as well. Along with new effective therapeutic opportunities, better clinical and molecularly driven patient selection will represent the cornerstone of the global care for these patients.

Targeting the HGF/Met signalling pathway in cancer

Under normal conditions, hepatocyte growth factor (HGF)-induced Met tyrosine kinase (TK) activation is tightly regulated by paracrine ligand delivery, ligand activation at the target cell surface, and ligand activated receptor internalisation and degradation. Despite these controls, HGF/Met signalling contributes to oncogenesis and tumour progression in several cancers and promotes aggressive cellular invasiveness that is strongly linked to tumour metastasis. The prevalence of HGF/Met pathway activation in human malignancies has driven rapid growth in cancer drug development programmes. Pathway inhibitors can be divided broadly into biologicals and low molecular weight synthetic TK inhibitors; of these, the latter now outnumber all other inhibitor types. We review here the basic properties of HGF/Met pathway antagonists now in preclinical and clinical development as well as the latest clinical trial results. The main challenges facing the effective use of HGF/Met-targeted antagonists for cancer treatment include optimal patient selection, diagnostic and pharmacodynamic biomarker development, and the identification and testing of optimal therapy combinations. The wealth of basic information, analytical reagents and model systems available concerning HGF/Met oncogenic signalling will continue to be invaluable in meeting these challenges and moving expeditiously toward more effective disease control.

Esophagogastric cancer: targeted agents

Because of the poor prognosis for patients with locally advanced and metastatic esophageal, gastroesophageal junction and gastric cancers, increasing attention has focused on the integration of targeted agents into current therapies. The molecular targets of these agents include epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF) or its receptor, cyclooxygenase-2 (COX-2), mammalian target of rapamycin (mTOR) and components and regulators of the cell cycle. In this review article, we briefly discuss pre-clinical data and the rationale for targeting these pathways and summarize the results of clinical trials to-date, including completed and ongoing phase III evaluations.