Progress in Glioma Stem Cell Research

Glioblastoma multiforme (GBM) represents a diverse spectrum of primary tumors notorious for their resistance to established therapeutic modalities. Despite aggressive interventions like surgery, radiation, and chemotherapy, these tumors, due to factors such as the blood-brain barrier, tumor heterogeneity, glioma stem cells (GSCs), drug efflux pumps, and DNA damage repair mechanisms, persist beyond complete isolation, resulting in dismal outcomes for glioma patients. Presently, the standard initial approach comprises surgical excision followed by concurrent chemotherapy, where temozolomide (TMZ) serves as the foremost option in managing GBM patients. Subsequent adjuvant chemotherapy follows this regimen. Emerging therapeutic approaches encompass immunotherapy, including checkpoint inhibitors, and targeted treatments, such as bevacizumab, aiming to exploit vulnerabilities within GBM cells. Nevertheless, there exists a pressing imperative to devise innovative strategies for both diagnosing and treating GBM. This review emphasizes the current knowledge of GSC biology, molecular mechanisms, and associations with various signals and/or pathways, such as the epidermal growth factor receptor, PI3K/AKT/mTOR, HGFR/c-MET, NF-κB, Wnt, Notch, and STAT3 pathways. Metabolic reprogramming in GSCs has also been reported with the prominent activation of the glycolytic pathway, comprising aldehyde dehydrogenase family genes. We also discuss potential therapeutic approaches to GSC targets and currently used inhibitors, as well as their mode of action on GSC targets.

Looking for a strategy in treating peritoneal gastric cancer carcinomatosis: an Italian multicenter Gastric Cancer Research group's analysis

BACKGROUND

The present study provides a snapshot of Italian patients with peritoneal metastasis from gastric cancer treated by surgery in Italian centers belonging to the Italian Research Group on Gastric Cancer. Prognostic factors affecting survival in such cohort of patients were evaluated with the final aim to identify patients who may benefit from radical intent surgery.

METHODS

It is a multicentric retrospective study based on a prospectively collected database including demographics, clinical, surgical, pathological, and follow-up data of patients with gastric cancer and synchronous macroscopic peritoneal metastases. Patients were surgically treated from January 2005 to January 2017. We focused on patients with macroscopic peritoneal carcinomatosis (PC) treated with upfront surgery in order to provide homogeneous evidences.

RESULTS

Our results show that patients with peritoneal carcinomatosis cannot be considered all lost. Strictly selected cases (R0/R1 and P1 patients) could benefit from an aggressive surgical approach performing an extended lymphadenectomy and HIPEC treatment.

CONCLUSION

The main result of the study is that GC patients with limited peritoneal involvement can have a survival benefit from a surgery with "radical oncological intent", that means extended lymphadenectomy and R0 resection. The retrospective nature of this study is an important bias, and for this reason, we have started a prospective multicentric study including Italian stage IV patients that hopefully will give us more answers.

ctDNA analysis in the personalized clinical management of gastroesophageal adenocarcinoma: turning hope into reality

Gastroesophageal adenocarcinoma (GEA) is a global health issue with a high fatality-to-case ratio and a 5-year overall survival that has only slightly improved. High-throughput molecular profiling has uncovered a profound complexity and heterogeneity in GEA biology, which limits considerably the treatment advances. Liquid biopsy with circulating tumor (ct)DNA analysis could elucidate GEA molecular heterogeneity and provide diagnostic, prognostic and predictive information to guide clinical decision-making. However, only a handful of studies have shown positive results for the application of ctDNA analysis in GEA clinical management. As a result, no comprehensive information is available to date on this continuously evolving topic. Here, we discuss the current state of knowledge, along with promises and challenges related to ctDNA analysis in GEA.

Identification of ARGLU1 as a potential therapeutic target for gastric cancer based on genome-wide functional screening data

BACKGROUND

Due to the molecular mechanism complexity and heterogeneity of gastric cancer (GC), mechanistically interpretable biomarkers were required for predicting prognosis and discovering therapeutic targets for GC patients.

METHODS

Based on a total of 824 GC-specific fitness genes from the Project Score database, LASSOCox regression was performed in TCGA-STAD cohort to construct a GC Prognostic (GCP) model which was then evaluated on 7 independent GC datasets. Targets prioritization was performed in GC organoids. ARGLU1 was selected to further explore the biological function and molecular mechanism. We evaluated the potential of ARGLU1 serving as a promising therapeutic target for GC using patients derived xenograft (PDX) model.

FINDINGS

The 9-gene GCP model showed a statistically significant prognostic performance for GC patients in 7 validation cohorts. Perturbation of SSX4, DDX24, ARGLU1 and TTF2 inhibited GC organoids tumor growth. The results of tissue microarray indicated lower expression of ARGLU1 was correlated with advanced TNM stage and worse overall survival. Over-expression ARGLU1 significantly inhibited GC cells viability in vitro and in vivo. ARGLU1 could enhance the transcriptional level of mismatch repair genes including MLH3, MSH2, MSH3 and MSH6 by potentiating the recruitment of SP1 and YY1 on their promoters. Moreover, inducing ARGLU1 by LNP-formulated saRNA significantly inhibited tumor growth in PDX model.

INTERPRETATION

Based on genome-wide functional screening data, we constructed a 9-gene GCP model with satisfactory predictive accuracy and mechanistic interpretability. Out of nine prognostic genes, ARGLU1 was verified to be a potential therapeutic target for GC.

FUNDING

National Natural Science Foundation of China.

MET alterations and their impact on the future of non-small cell lung cancer (NSCLC) targeted therapies

Introduction: The MET gene and its pathway normally plays a crucial role in cell homeostasis, motility, and apoptosis. However, when the MET gene is altered, there is an imbalance toward cell proliferation and invasion commonly seen in numerous different types of cancers. The heterogeneous group of MET alterations that includes MET amplification, MET exon 14 skipping mutation, and MET fusions has been difficult to diagnose and treat. Currently, treatments are focused on tyrosine kinase inhibitors but now there is emerging data on novel MET-targeted therapies including monoclonal antibodies and antibody-drug conjugates that have emerged.Areas covered: We introduce new emerging data on MET alterations in non-small cell lung cancer (NSCLC) that has contributed to advances in MET targeted therapeutics. We offer our perspective and examine new information on the mechanisms of the MET alterations in this review.Expert opinion: Given the trends currently involving the targeting of MET altered malignancies, there will most likely be a continued rapid expansion of testing, novel tyrosine kinase inhibitors and potent antibody approaches. Combination treatments will be necessary to optimize management of advanced and early disease.

Molecularly targeted therapy for advanced gastrointestinal noncolorectal cancer treatment: how to choose? Past, present, future

Gastrointestinal cancer is a leading cause of death worldwide. Conventional cytotoxic chemotherapy has been the backbone of advanced gastrointestinal cancer treatment for decades and still represents a key element of the therapeutic armamentarium. However, only small increments in survival outcomes have been reached. New clinical trials are designed, including classic chemotherapy in association with either small-molecule inhibitors or mAb. During the past few years, remarkable progress in molecular biology of gastrointestinal noncolorectal cancers, the discovery of specific targets and the resulting development of systemic drugs that block critical kinases and several molecular pathways have all contributed to progress. New biological agents with molecularly targeted therapies are now available or currently included in clinical trials (EGFR inhibitors (i), antiangiogenic agents, c-METi, IDHi, FGFR2i, BRAFi, Pi3Ki/AKTi/mTORi, NTRKi). When we focus on the current state of precision medicine for gastrointestinal malignancies, it becomes apparent that there is a mixed history of success and failure. The aim of this review is to focus on the studies that have been completed to date with target therapies and to understand which of these are currently the accepted choice in clinical practice and which need further confirmation and approval for inclusion in guidelines. All these findings will enable to guide clinical practice for oncologists in the design of the next round of clinical trials.

Evolving therapies in advanced oesophago-gastric cancers and the increasing role of immunotherapy

INTRODUCTION

Esophagogastric cancers remain a considerable health burden and among the top causes of global cancer-related deaths. Chemotherapy remains the cornerstone of treatment for patients with advanced disease. Doublet platinum/fluoropyrimidine therapy is established as first-line treatment with the option of adding a taxane in selected patients. Irinotecan, taxanes, and ramucirumab are approved as second-line treatments. Results from the trials KEYNOTE-059, ATTRACTION-2, and TAGS have established the use of immune checkpoint inhibitors and trifluridine/tipiracil as a third-line treatment. High PD-L1 expression, microsatellite instability, tumor mutational burden, and Epstein-Barr virus status may also be used to enrich for responses to immunotherapy.

AREAS COVERED

In this review, we discuss the outcome of recent trials in the later lines of therapy for esophagogastric cancer and place these in the context of current treatment paradigms. We also discuss the biology of esophagogastric cancers and how this might inform the development of new treatments. Finally, we comment on promising new drugs in development.

EXPERT OPINION

Recent advances in the treatment of chemo-refractory esophagogastric cancer add to the improving survival of patients with this disease. Further research is needed to improve patient selection to therapies and the earlier incorporation of these agents in the treatment journey.

Luirink R, P. Geerke D, Op de Beeck K, Hermans C, Tiseo M, Van Schil P, Lardon F, Germonpré P, Rolfo C, Giovannetti E, J. Peters G, Pauwels P. The Role of c-Met as a Biomarker and Player in Innate and Acquired Resistance in Non-Small-Cell Lung Cancer: Two New Mutations Warrant Further Studies

The c-Met receptor is a therapeutically actionable target in non-small-cell lung cancer (NSCLC), with one approved drug and several agents in development. Most suitable biomarkers for patient selection include c-Met amplification and exon-14 skipping. Our retrospective study focused on the frequency of different c-Met aberrations (overexpression, amplification and mutations) in 153 primary, therapy-naïve resection samples and their paired metastases, from Biobank@UZA. Furthermore, we determined the correlation of c-Met expression with clinicopathological factors, Epidermal Growth Factor Receptor (EGFR)-status and TP53 mutations. Our results showed that c-Met expression levels in primary tumors were comparable to their respective metastases. Five different mutations were detected by deep sequencing: three (E168D, S203T, N375S) previously described and two never reported (I333T, G783E). I333T, a new mutation in the Sema(phorin) domain of c-Met, might influence the binding of antibodies targeting the HGF-binding domain, potentially causing innate resistance. E168D and S203T mutations showed a trend towards a correlation with high c-Met expression (p = 0.058). We found a significant correlation between c-MET expression, EGFR expression (p = 0.010) and EGFR mutations (p = 0.013), as well as a trend (p = 0.057) with regards to TP53 mutant activity. In conclusion this study demonstrated a strong correlation between EGFR mutations, TP53 and c-Met expression in therapy-naïve primary resection samples. Moreover, we found two new c-Met mutations that warrant further studies.

Combination of checkpoint inhibitors with radiotherapy in esophageal squamous cell carcinoma treatment: A novel strategy

Despite the rapid development of numerous types of treatment, including radiotherapy (RT) as the main strategy, esophageal squamous cell carcinoma (ESCC) has a poor prognosis. Recent studies demonstrated that immunotherapy can improve the survival of patients with locally advanced and metastatic ESCC. Furthermore, previous studies reported that the expression of programmed death-ligand 1 is significantly associated with esophageal cancer prognosis. At present, several ongoing clinical trials have extended the use of immunotherapy from palliative and salvage treatments to neoadjuvant treatment with concurrent chemoradiation. The first- or second-line treatments were used to explore antitumor efficacy with reduced adverse events. The combination of RT and immunotherapy can exert a local therapeutic effect and improve the function of the immune system, enhancing antitumor efficacy. This review investigated the role of immunotherapy and radiotherapy in ESCC and described the potential efficacy of combining immunotherapy with radiotherapy in ESCC.

Capmatinib for the treatment of non-small cell lung cancer

Introduction: Activation of the MET pathway through MET amplifications or mutations is present in 3-4% of stage IV non-squamous non-small cell lung cancers (NSCLC). High MET amplifications and exon 14 skipping mutations are associated with poor prognosis: new treatments are needed for these patients. Capmatinib is a highly selective, potent small-molecule MET inhibitor with antitumor activity in NSCLC in vitro and in vivo. Areas covered: This article provides an overview of the capmatinib clinical development program in NSCLC, both as monotherapy in NSCLC with a dysregulated MET pathway, and in combination with epidermal growth factor receptor (EGFR) inhibitor therapy in EGFR-mutant NSCLC with MET-based acquired resistance to previous EGFR inhibition. Expert opinion: In the GEOMETRY Mono-1 study, treatment with capmatinib resulted in high response rates in stage IV NSCLC with MET exon 14 skipping mutations, particularly in first line, supporting testing for this biomarker at the time of diagnosis. Durable responses have been reported and results in MET-amplified NSCLC are eagerly anticipated. In EGFR-mutant NSCLC, notable responses have been observed in combination with an EGFR-tyrosine kinase inhibitor (TKI) in case of acquired resistance to EGFR-TKIs based on high MET amplification.

Evaluation of Intratumoral and Intertumoral Heterogeneity of MET Protein Expression in Gastric Cancer

Tumor heterogeneity of a target molecule could contribute to failure of the targeted therapy. We investigated the heterogeneity of MET expression within same primary gastric cancer (GC) and between primary and corresponding secondary GC lesions using immunohistochemistry (IHC). Intratumoral heterogeneity was defined as discordant MET status among 3 tissue microarray cores (3 different areas of same tumor). IHC 3+ was considered positive for MET overexpression. MET overexpression was observed in 2.7% (50/1869) of all examined cores and 5.3% (33/623) of primary GCs. When we compared MET IHC results between 3 cores from each tumor, intratumoral heterogeneity was identified (65.0% in total 623 cases; 84.4% in 480 cases with any staining intensity; 84.9% in 251 cases with moderate to strong intensity; 90.9% in 33 cases with strong intensity). Of 33 MET-overexpressed GCs, the average proportion of strongly stained area was 19.6% in the whole sections. Of 269 cases with primary GC and regional lymph node metastasis, 17 (6.3%) showed MET positivity in which 9 (52.9%) were discordant (negative conversion). In 123 cases with primary and corresponding local recurrent/distant metastatic GC, 3 (2.4%) showed MET positivity in which 2 (66.7%) were discordant (positive conversion). In the survival analysis, MET IHC 3+ in lymph node metastases was an independent negative prognostic factor for overall survival. We found that MET overexpression is uncommon and highly heterogeneous in GC. This severe heterogeneity of MET status should be considered in tissue sampling and development of biomarkers for anti-MET therapy.

Tumor Genomic Profiling Guides Patients with Metastatic Gastric Cancer to Targeted Treatment: The VIKTORY Umbrella Trial

The VIKTORY (targeted agent eValuation In gastric cancer basket KORea) trial was designed to classify patients with metastatic gastric cancer based on clinical sequencing and focused on eight different biomarker groups (RAS aberration, TP53 mutation, PIK3CA mutation/amplification, MET amplification, MET overexpression, all negative, TSC2 deficient, or RICTOR amplification) to assign patients to one of the 10 associated clinical trials in second-line (2L) treatment. Capivasertib (AKT inhibitor), savolitinib (MET inhibitor), selumetinib (MEK inhibitor), adavosertib (WEE1 inhibitor), and vistusertib (TORC inhibitor) were tested with or without chemotherapy. Seven hundred seventy-two patients with gastric cancer were enrolled, and sequencing was successfully achieved in 715 patients (92.6%). When molecular screening was linked to seamless immediate access to parallel matched trials, 14.7% of patients received biomarker-assigned drug treatment. The biomarker-assigned treatment cohort had encouraging response rates and survival when compared with conventional 2L chemotherapy. Circulating tumor (ctDNA) analysis demonstrated good correlation between high MET copy number by ctDNA and response to savolitinib. SIGNIFICANCE: Prospective clinical sequencing revealed that baseline heterogeneity between tumor samples from different patients affected response to biomarker-selected therapies. VIKTORY is the first and largest platform study in gastric cancer and supports both the feasibility of tumor profiling and its clinical utility.This article is highlighted in the In This Issue feature, p. 1325.

MM-131, a bispecific anti-Met/EpCAM mAb, inhibits HGF-dependent and HGF-independent Met signaling through concurrent binding to EpCAM

Activation of the Met receptor tyrosine kinase, either by its ligand, hepatocyte growth factor (HGF), or via ligand-independent mechanisms, such as MET amplification or receptor overexpression, has been implicated in driving tumor proliferation, metastasis, and resistance to therapy. Clinical development of Met-targeted antibodies has been challenging, however, as bivalent antibodies exhibit agonistic properties, whereas monovalent antibodies lack potency and the capacity to down-regulate Met. Through computational modeling, we found that the potency of a monovalent antibody targeting Met could be dramatically improved by introducing a second binding site that recognizes an unrelated, highly expressed antigen on the tumor cell surface. Guided by this prediction, we engineered MM-131, a bispecific antibody that is monovalent for both Met and epithelial cell adhesion molecule (EpCAM). MM-131 is a purely antagonistic antibody that blocks ligand-dependent and ligand-independent Met signaling by inhibiting HGF binding to Met and inducing receptor down-regulation. Together, these mechanisms lead to inhibition of proliferation in Met-driven cancer cells, inhibition of HGF-mediated cancer cell migration, and inhibition of tumor growth in HGF-dependent and -independent mouse xenograft models. Consistent with its design, MM-131 is more potent in EpCAM-high cells than in EpCAM-low cells, and its potency decreases when EpCAM levels are reduced by RNAi. Evaluation of Met, EpCAM, and HGF levels in human tumor samples reveals that EpCAM is expressed at high levels in a wide range of Met-positive tumor types, suggesting a broad opportunity for clinical development of MM-131.

New drug developments in metastatic gastric cancer

Metastatic gastric cancer is associated with a poor prognosis and novel treatment options are desperately needed. The development of targeted therapies heralded a new era for the management of metastatic gastric cancer, however results from clinical trials of numerous targeted agents have been mixed. The advent of immune checkpoint inhibitors has yielded similar promise and results from early trials are encouraging. This review provides an overview of the systemic treatment options evaluated in metastatic gastric cancer, with a focus on recent evidence from clinical trials for targeted therapies and immune checkpoint inhibitors. The failure to identify appropriate predictive biomarkers has hampered the success of many targeted therapies in gastric cancer, and a deeper understanding of specific molecular subtypes and genomic alterations may allow for more precision in the application of novel therapies. Identifying appropriate biomarkers for patient selection is essential for future clinical trials, for the most effective use of novel agents and in combination approaches to account for growing complexity of treatment options.

Prognostic and predictive factors for overall survival in metastatic oesophagogastric cancer: A systematic review and meta-analysis

BACKGROUND

Consistent evidence on prognostic and predictive factors for advanced oesophagogastric cancer is lacking. Therefore, we performed a systematic review and meta-analysis.

METHODS

We searched PubMed, Embase and the Cochrane Central Register of Controlled Trials (CENTRAL) databases for phase II/III randomised controlled trials (RCTs) until February 2017 on palliative systemic therapy for advanced oesophagogastric cancer that reported prognostic or predictive factors for overall survival (PROSPERO-CRD42014015177). Prognostic factors were identified from multivariate regression analyses in study reports. Factors were considered potentially clinically relevant if statistically significant (P ≤ 0.05) in multivariate analysis in ≥50% of the total number of patients in the pooled sample of the RCTs and were reported with a pooled sample size of ≥600 patients in the first-line or ≥300 patients in the beyond first-line setting. Predictive factors were identified from time-to-event stratified treatment comparisons and deemed potentially clinically relevant if the P-value for interaction between subgroups was ≤0.20 and the hazard ratio in one of the subgroups was significant (P ≤ 0.05).

RESULTS

Forty-six original RCTs were included (n = 15,392 patients) reporting on first-line (n = 33) and beyond first-line therapy (n = 13). Seventeen prognostic factors for overall survival in the first-line and four in the beyond first-line treatment setting were potentially clinically relevant. Twenty-one predictive factors in first-line and nine in beyond first-line treatment setting were potentially relevant regarding treatment efficacy.

CONCLUSIONS

The prognostic and predictive factors identified in this systematic review can be used to characterise patients in clinical practice, be included in future trial designs, enrich prognostic tools and generate hypotheses to be tested in future research to promote patient-centred treatment.

Emerging Therapies in the Management of Advanced-Stage Gastric Cancer

Globally, gastric malignancy contributes to significant cancer-related morbidity and mortality. Despite a recent approval of two targeted agents, trastuzumab and ramucirumab, the treatment options for advanced-stage gastric cancer are limited. Consequently, the overall clinical outcomes for patients with advanced-stage gastric cancer remain poor. Numerous agents that are active against novel targets have been evaluated in the course of randomized trials; however, most have produced disappointing results because of the molecular heterogeneity of gastric cancer. The Cancer Genome Atlas (TCGA) project proposed a new classification system for gastric cancer that includes four different tumor subtypes based on molecular characteristics. This change led to the identification of several distinct and potentially targetable pathways. However, most agents targeting these pathways do not elicit any meaningful clinical benefit when employed for the treatment of advanced-stage gastric cancer. Most advanced-stage gastric cancer trials currently focus on agents that modulate tumor microenvironments and cancer cell stemness. In this review, we summarize data regarding novel compounds that have shown efficacy in early phase studies and show promise as effective therapeutic agents, with special emphasis on those for which phase III trials are either planned or underway.

Genomic markers of resistance to targeted treatments in gastric cancer: potential new treatment strategies

Gastric cancer is a highly heterogeneous disease, displaying a complex genomic landscape and an unfavorable outcome with standard therapies. Based on distinctive genomic alterations, novel targeted agents have been developed with the aim of personalizing treatments and improving patient outcome. However, a subgroup of patients is primarily treatment-resistant, and even in the initially sensitive population, secondary resistance emerges, thus limiting therapeutic benefit. In this review, we summarize the clinical data about standard targeted agents in gastric cancer, specifically anti-HER2 treatments and antivascular therapies. We also illustrate the available evidence regarding molecular mechanisms of resistance to these agents and we discuss potential strategies for new targeted treatments that could overcome such resistance.

Molecular biomarkers in gastro-esophageal cancer: recent developments, current trends and future directions

Gastro-esophageal adenocarcinomas (GEA) represent a severe global health burden and despite improvements in the multimodality treatment of these malignancies the prognosis of patients remains poor. HER2 overexpression/amplification has been the first predictive biomarker approved in clinical practice to guide patient selection for targeted treatment with trastuzumab in advanced gastric and gastro-esophageal junction cancers. More recently, immunotherapy has been approved for the treatment of GEA and PD-L1 expression is now a biomarker required for the administration of pembrolizumab in these diseases. Significant progress has been made in recent years in dissecting the genomic makeup of GEA in order to identify distinct molecular subtypes linked to distinct patterns of molecular alterations. GEA have been found to be highly heterogeneous malignances, representing a challenge for biomarkers discovery and targeted treatment development. The current review focuses on an overview of established and novel promising biomarkers in GEA, covering recent molecular classifications from TCGA and ACRG. Main elements of molecular heterogeneity are discussed, as well as emerging mechanisms of primary and secondary resistance to HER2 targeted treatment and recent biomarker-driven trials. Future perspectives on the role of epigenetics, miRNA/lncRNA and liquid biopsy, and patient-derived xenograft models as a new platform for molecular-targeted drug discovery in GEA are presented. Our knowledge on the genomic landscape of GEA continues to evolve, uncovering the high heterogeneity and deep complexity of these tumors. The availability of new technologies and the identification of promising novel biomarker will be critical to optimize targeted treatment development in a setting where therapeutic options are currently lacking. Nevertheless, clinical validation of novel biomarkers and treatment strategies still represents an issue.

Proposed Molecular and miRNA Classification of Gastric Cancer

Gastric cancer (GC) is a common malignant neoplasm worldwide and one of the main cause of cancer-related deaths. Despite some advances in therapies, long-term survival of patients with advanced disease remains poor. Different types of classification have been used to stratify patients with GC for shaping prognosis and treatment planning. Based on new knowledge of molecular pathways associated with different aspect of GC, new pathogenetic classifications for GC have been and continue to be proposed. These novel classifications create a new paradigm in the definition of cancer biology and allow the identification of relevant GC genomic subsets by using different techniques such as genomic screenings, functional studies and molecular or epigenetic characterization. An improved prognostic classification for GC is essential for the development of a proper therapy for a proper patient population. The aim of this review is to discuss the state-of-the-art on combining histological and molecular classifications of GC to give an overview of the emerging therapeutic possibilities connected to the latest discoveries regarding GC.

Genomic Profiling of HER2-Positive Gastric Cancer: PI3K/Akt/mTOR Pathway as Predictor of Outcomes in HER2-Positive Advanced Gastric Cancer Treated with Trastuzumab

BACKGROUND

HER2-positive gastric cancer (GC) affects 7%-34% of patients with GC. Trastuzumab-based first-line treatment has become the standard of care for HER2-positive advanced gastric cancer (AGC). However, there are no clinically validated biomarkers for resistance to HER2-targeted therapies. Upregulation of PI3K pathway and tyrosine kinase receptor (TKR) alterations have been noted as molecular mechanisms of resistance in breast cancer. Our study aimed to perform a molecular characterization of HER2-positive AGC and investigate the role of PI3K/Akt/mTOR signaling pathway activation and TKR gene copy number (GCN) gains as predictive biomarkers in HER2-positive AGC treated with trastuzumab.

PATIENTS AND METHODS

Forty-two HER2-positive GC samples from patients treated with trastuzumab-based first-line chemotherapy were selected. DNA samples were sequenced. PTEN and MET immunohistochemistry were also performed.

RESULTS

Concurrent genetic alterations were detected in 97.1% of HER2-positive AGC. We found activation of PI3K/Akt/mTOR pathway in 52.4% of patients and TKR GCN gains in 38.1%. TKR GCN gains did not correlate with overall survival (OS) or progression-free survival (PFS). Multivariate Cox models showed that PI3K/Akt/mTOR activation negatively affects the effectiveness of trastuzumab-based chemotherapy in terms of OS and PFS.

CONCLUSION

Our results provide for the first time a detailed molecular profile of concurrent genetic alterations in HER2-positive AGC. PI3K pathway activation could be used as a predictive marker of worse outcome in this patient population. In addition, gains in copy number of other TKR genes in this subgroup may also influence the survival benefit obtained with trastuzumab.

IMPLICATIONS FOR PRACTICE

This article reports, for the first time, a detailed molecular profile of genomic alterations in patients with HER2-positive advanced gastric cancer (AGC). PI3K/Akt/mTOR signaling pathway activation seems to have a differentially negative effect on overall survival and progression-free survival in AGC treated with trastuzumab-based chemotherapy. Combining different targeted agents could be a successful therapeutic strategy to improve the prognosis of HER2-positive AGC.

Untying the gordion knot of targeting MET in cancer

Despite compelling evidence backing the crucial role of a dysregulated MET axis in cancer and a myriad of agents targeting this pathway in active clinical development, the therapeutic value of MET inhibition in cancer oncology remains to be established. Although a series of disappointing clinical trials, at first, lessened fervor for targeting this pathway, investigations continue unabated with a number of novel active compounds entering clinical trials. Suboptimal designs which lacked biomarker selection have been the main reason for these early failures and this has stimulated a more biomarker enriched approach lately. Fresh insights into the mechanics of diverse MET aberrations (amplifications and mutations) have allowed trial enrichment for appropriate patients in appropriate disease settings. Development of MET inhibition as a therapeutic strategy in cancer has been a lesson in itself reflecting the challenging opportunities enclosed in the genetic landscape of cancer. Here, we will review the status of MET targeted therapy in development as it stands today, discuss emerging paradigms in MET inhibition and theorize on concepts for future development. We venture to propose that in spite of early disappointments, the future of this therapeutic strategy is promising with use of appropriate predictive biomarker in the right clinical context.

Treatment for unresectable or metastatic oesophageal cancer: current evidence and trends

Approximately half of the patients diagnosed with oesophageal cancer present with unresectable or metastatic disease. Treatment for these patients aims to control dysphagia and other cancer-related symptoms, improve quality of life and prolong survival. In the past 25 years, modestly improved outcomes have been achieved in the treatment of patients with inoperable non-metastatic cancer who are medically not fit for surgery or have unresectable, locally advanced disease. Concurrent chemoradiotherapy offers the best outcomes in these patients. In distant metastatic oesophageal cancer, several double-agent or triple-agent chemotherapy regimens have been established as first-line treatment options. In addition, long-term results of multiple large randomized phase III trials using additional targeted therapies have been published in the past few years, affecting contemporary clinical practice and future research directions. For the local treatment of malignant dysphagia, various treatment options have emerged, and self-expandable metal stent (SEMS) placement is currently the most widely applied method. Besides the continuous search for improved SEMS designs to minimize the risk of associated complications, efforts have been made to develop and evaluate the efficacy of antireflux stents and irradiation stents. This Review outlines the current evidence and ongoing trends in the different modern-day, multidisciplinary interventions for patients with unresectable or metastatic oesophageal cancer with an emphasis on key randomized trials.

Biomarker-driven targeted therapies for gastric/gastro-esophageal junction malignancies

Gastroesophageal malignancies often contain high amounts of genetic and molecular alterations that result in an aggressive disease capable of rapidly metastasizing to distant organs and early development of drug resistance. Most patients in the Western hemisphere present with locally advanced or metastatic disease that is treated with systemic chemotherapy used either in the neoadjuvant or palliative setting, respectively. This article will review the various recent advances in the development of targeted therapies for the treatment of advanced gastric and gastroesophageal cancer.

Novel Systemic Therapies for Advanced Gastric Cancer

Gastric cancer (GC) is the second leading cause of cancer mortality and the fourth most commonly diagnosed malignant diseases. While continued efforts have been focused on GC treatment, the introduction of trastuzumab marked the beginning of a new era of target-specific treatments. Considering the diversity of mutations in GC, satisfactory results obtained from various target-specific therapies were expected, yet most of them were unsuccessful in controlled clinical trials. There are several possible reasons underlying the failures, including the absence of patient selection depending on validated predictive biomarkers, the inappropriate combination of drugs, and tumor heterogeneity. In contrast to targeted agents, immuno-oncologic agents are designed to regulate and boost immunity, are not target-specific, and may overcome tumor heterogeneity. With the successful establishment of predictive biomarkers, including Epstein-Barr virus pattern, microsatellite instability status, and programmed death-ligand 1 (PD-L1) expression, as well as ideal combination regimens, a new frontier in the immuno-oncology of GC treatment is on the horizon. Since the field of immuno-oncology has witnessed innovative, practice-changing successes in other cancer types, several trials on GC are ongoing. Among immuno-oncologic therapies, immune checkpoint inhibitors are the mainstay of clinical trials performed on GC. In this article, we review target-specific agents currently used in clinics or are undergoing clinical trials, and highlight the future clinical application of immuno-oncologic agents in inoperable GC.

Customization of therapy for gastroesophageal adenocarcinoma patients

Gastroesophageal adenocarcinomas (GEACs) remain a global health problem. These are most often diagnosed at advanced stage and the estimated 5-year relative survival rate is about 5%. Although cure is not possible for patients with advanced GEAC, systemic therapy (chemotherapy or biochemotherapy) can palliate symptoms, improve survival and provide a better quality of life. One of the most promising options for some patients with advanced stage GEAC is immunotherapy, which can result in durable responses. Numerous phase III trials evaluating targeted therapies in different lines are ongoing and it is hoped that better biomarkers will emerge to identify patients who can benefit from targeted agents and immunotherapy in the future. Surgery remains as the corner stone for localized GEAC and adjunctive therapies can increase the survival rates by about 10%. The high toxicity and low completion rates of adjuvant therapy led to the strategies of preoperative treatment. With the results of ongoing pre-operative therapy trials we will be able to determine the optimal adjunctive approach for resectable GEAC.

HER2 Confers Resistance to Foretinib Inhibition of MET-Amplified Esophageal Adenocarcinoma Cells

BACKGROUND

Recent genomic studies indicated that esophageal adenocarcinoma (EAC) is driven by amplification of c-MET or HER2 or both in a subset of patients. We studied the effect of MET targeting by the small molecule inhibitor foretinib in EAC cells and the interplay between MET and HER2 signaling.

METHODS

We measured the expression levels and phosphorylation status of MET and HER2 proteins in EAC cell lines using Western blot analysis. The expression levels of MET and HER2 were manipulated by transfecting cells with specific siRNA or a plasmid expressing HER2. The small molecule inhibitors of c-MET and ERBB1/2 (foretinib and lapatinib, respectively) were tested for effect on growth, apoptosis, and downstream signaling pathways of EAC cells as single agents or in combination. The response to inhibitors was correlated to the levels of MET, HER2 expression, and amplification status.

RESULTS

Foretinib inhibits phosphorylation of MET, which correlated with reduced EAC cell growth and inhibition of AKT and ERK phosphorylation. Cell growth inhibition by foretinib is most profound in the ESO51 cell line, which has MET gene amplification and overexpression. Inhibition of MET signaling by foretinib or siRNA-specific knock down of MET expression induces apoptosis in ESO51 cells. Ectopic expression of HER2 reduces foretinib-mediated growth inhibition and downstream ERK phosphorylation in ESO51-HER2 cells. The EAC OE33 cell line, with amplification and overexpression of both MET and HER2, demonstrated reduced sensitivity to foretinib or lapatinib and had a transient effect on downstream inhibition of phosphorylated AKT and ERK (p-AKT, p-ERK). The coadministration of foretinib and lapatinib effectively blocked both MET and HER2 signaling through the p-AKT and p-ERK pathways, dramatically inhibited growth, and induced apoptosis to overcome single-agent resistance in OE33 cells.

CONCLUSIONS

The mechanism for foretinib growth inhibition in MET-amplified EAC tumor cells is demonstrated. The interplay of dual MET/HER2 overexpression in the AKT and ERK pathways for esophageal cancer is described. Therefore, combination therapy could be a novel strategy for EAC with amplification of both MET and HER2.

A Phase 1 study evaluating AMG 337 in Asian patients with advanced solid tumors

AMG 337, a selective small-molecule MET inhibitor, was evaluated in Asian patients with advanced solid tumors. Eligible patients orally self-administered AMG 337; the initial dose of 150 mg once daily (QD) was escalated to 300 mg QD (modified 3+3+3 design). Treatment continued until disease progression, intolerability, or death. The primary endpoint was adverse events (AEs) and clinical abnormalities defined as dose-limiting toxicities (DLTs). Secondary endpoints included other AEs, pharmacokinetics and tumor response. Eleven patients were enrolled. No DLTs occurred. The most common treatment-emergent AEs were headache (73%) and nausea (45%). Cmax and AUC0-24 exposures increased proportionally with dose; t1/2 was comparable between groups; plasma accumulation was minimal over 28 days. One patient (150 mg) had partial response; one patient (300 mg) had stable disease. Safety, tolerability, pharmacokinetics and efficacy of AMG 337 in Asian patients were consistent with those observed in Western patient populations. The study was terminated early.

MP0250, a VEGF and HGF neutralizing DARPin® molecule shows high anti-tumor efficacy in mouse xenograft and patient-derived tumor models

Background

The VEGF/VEGFR and the HGF/cMET pathways are key mediators of the interplay of tumor cells and their microenvironment. However, inhibition of VEGF has been shown to produce only limited clinical benefit and inhibition of the activation of cMET by HGF has not translated into clinical benefit in pivotal trials. MP0250, a DARPin^® molecule that specifically inhibits both VEGF and HGF has been developed to explore the clinical potential of dual inhibition of these pathways.

Results

MP0250 binding to VEGF and HGF inhibited downstream signalling through VEGFR2 and cMET resulting in inhibition of proliferation of VEGF- and HGF-dependent cells. Antitumor activity was demonstrated in VEGF- and HGF-dependent xenograft and syngeneic models with activity superior to that of individual VEGF- and HGF-blocking DARPin^® molecules. Combination therapy studies showed potentiation of the antitumor activity of chemotherapy and immunotherapy agents, including an anti-PD1 antibody.

Materials and Methods

Potency of MP0250 was assessed in cellular models and in a variety of xenograft models as monotherapy or in combination with standard-of-care drugs.

Conclusions

Dual inhibition of VEGF and HGF by MP0250 produced powerful single agent and combination antitumor activity. This, together with increasing understanding of the role of the HGF/cMET pathway in resistance to VEGF (and other agents), supports testing of MP0250 in the clinic.

Phase I dose-escalation study of the c-Met tyrosine kinase inhibitor SAR125844 in Asian patients with advanced solid tumors, including patients with MET-amplified gastric cancer

SAR125844 is a potent and selective inhibitor of the c-Met kinase receptor. This was an open-label, phase I, multicenter, dose-escalation, and dose-expansion trial of SAR125844 in Asian patients with solid tumors, a subgroup of whom had gastric cancer and MET amplification (NCT01657214). SAR125844 was administered by intravenous infusion (260-570 mg/m2) on days 1, 8, 15, and 22 of each 28-day cycle. Objectives were to determine the maximum tolerated dose (MTD) and to evaluate SAR125844 safety and pharmacokinetic profile. Antitumor activity was also assessed. Of 38 patients enrolled (median age 64.0 years), 22 had gastric cancer, including 14 with MET amplification. In the dose-escalation cohort (N = 19; unselected population, including three patients with MET-amplification [two with gastric cancer and one with lung cancer]), the MTD was not reached, and the recommended dose was established at 570 mg/m2. Most frequent treatment-emergent adverse events (AEs) were nausea (36.8%), vomiting (34.2%), decreased appetite (28.9%), and fatigue or asthenia, constipation, and abdominal pains (each 21.1%); none appeared to be dose-dependent. Grade ≥ 3 AEs were observed in 39.5% of patients and considered drug-related in 7.9%. SAR125844 exposure increased slightly more than expected by dose proportionality; dose had no significant effect on clearance. No objective responses were observed in the dose-escalation cohort, with seven patients (three gastric cancer, two colorectal cancer, one breast cancer, and one with cancer of unknown primary origin) having stable disease. Modest antitumor activity was observed at 570 mg/m2 in the dose-expansion cohort, comprising patients with MET-amplified tumors (N = 19). Two gastric cancer patients had partial responses, seven patients had stable disease (six gastric cancer and one kidney cancer), and 10 patients had progressive disease. Single-agent SAR125844 administered up to 570 mg/m2 has acceptable tolerability and modest antitumor activity in patients with MET-amplified gastric cancer.

Challenges and future of biomarker tests in the era of precision oncology: Can we rely on immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH) to select the optimal patients for matched therapy?

Molecular techniques have improved our understanding of the pathogenesis of cancer development. These techniques have also fueled the rational development of targeted drugs for patient populations stratified by their genetic characteristics. These novel methods have changed the classic paradigm of diagnostic pathology; among them are IHC, FISH, polymerase chain reaction (PCR) and microarray technology. IHC and FISH detection methods for human epidermal growth factor receptor-2 (HER2), epidermal growth factor receptor (EGFR) and programmed death ligand-1 (PD-L1) were recently approved by the Food and Drug Administration (FDA) as routine clinical practice for cancer patients. Here, we discuss general challenges related to the predictive power of these molecular biomarkers for targeted therapy in cancer medicine. We will also discuss the prospects of utilizing new biomarkers for fibroblast growth factor receptor (FGFR) and hepatocyte growth factor receptor (cMET/MET) targeted therapies for developing new and robust predictive biomarkers in oncology.

Oesophageal cancer

Oesophageal cancer is the sixth most common cause of cancer-related death worldwide and is therefore a major global health challenge. The two major subtypes of oesophageal cancer are oesophageal squamous cell carcinoma (OSCC) and oesophageal adenocarcinoma (OAC), which are epidemiologically and biologically distinct. OSCC accounts for 90% of all cases of oesophageal cancer globally and is highly prevalent in the East, East Africa and South America. OAC is more common in developed countries than in developing countries. Preneoplastic lesions are identifiable for both OSCC and OAC; these are frequently amenable to endoscopic ablative therapies. Most patients with oesophageal cancer require extensive treatment, including chemotherapy, chemoradiotherapy and/or surgical resection. Patients with advanced or metastatic oesophageal cancer are treated with palliative chemotherapy; those who are human epidermal growth factor receptor 2 (HER2)-positive may also benefit from trastuzumab treatment. Immuno-oncology therapies have also shown promising early results in OSCC and OAC. In this Primer, we review state-of-the-art knowledge on the biology and treatment of oesophageal cancer, including screening, endoscopic ablative therapies and emerging molecular targets, and we discuss best practices in chemotherapy, chemoradiotherapy, surgery and the maintenance of patient quality of life.

Personalised Treatment in Gastric Cancer: Myth or Reality?

Despite recent diagnostic and therapeutic advances, the survival of patients with gastric cancer is still poor. The majority of patients are diagnosed with advanced disease and chemotherapy represents the only possible therapeutic approach. However, chemotherapy seems to have reached an efficacy plateau in this setting. Gastric cancer is a complex and heterogeneous disease because it emerges from multiple interactions of genetic, environmental and host factors. A better understanding of its molecular characteristics may lead to an improvement of outcomes. The recent molecular classification by The Cancer Genome Atlas project divides gastric cancer into four subtypes that could be taken into consideration in future clinical trials with targeted agents. So far trastuzumab, a monoclonal antibody addressing the HER2 receptor, is the only targeted agent approved in the first-line setting, but only in patients overexpressing HER2. Negative data have been obtained in first-line therapy when antiangiogenics, anti-EGFR or anti-MET monoclonal antibodies have been studied in randomised controlled trials. Ramucirumab, a monoclonal antibody binding to VEGFR2, is the only antiangiogenic agent currently recommended in patients progressing after first-line treatment. In this review, we discuss whether personalised therapy may have a role in gastric cancer.

Insights into next developments in advanced gastric cancer

PURPOSE OF REVIEW

The purpose of the review is to delineate novel approaches for biology-based treatment in advanced gastric cancer. We reviewed the latest translational and clinical research articles and congress presentations.

RECENT FINDINGS

A new molecular classification of gastric cancer based on histology, genetic and proteomic alterations has evolved. It provides a roadmap for development of new drugs and combinations and for patient stratification. Anti-HER2 treatment, which is an effective strategy in metastatic gastric cancer, is now also being studied in the perioperative setting. However, resistance mechanisms in advanced disease are poorly understood and optimal patient selection remains challenging. Targeting angiogenesis is an emerging concept in the management of advanced gastric cancer, and ramucirumab has prolonged survival in the second line either as a monotherapy or in combination with paclitaxel. Biomarkers for selecting patients who benefit from ramucirumab are still lacking. Immune checkpoint blockade and inhibition of cancer stemness targets are other emerging directions for the medical treatment of gastric cancer. Large-scale international studies are ongoing.

SUMMARY

Promising biology-based treatment strategies are evolving. But tumor heterogeneity which is an inherent feature of gastric cancer challenges the development of molecularly targeted and personalized treatment strategies.

Targeting MET in cancer therapy

MET encodes a receptor tyrosine kinase c-MET for hepatocyte growth factor (HGF). The specific combination of c-MET and HGF activates downstream signaling pathways to trigger cell migration, proliferation, and angiogenesis. MET exon 14 alterations and MET gene amplification play a critical role in the origin of cancer. Several monoclonal antibodies and small-molecule inhibitors of c-MET have been evaluated in clinical trials. In patients with advanced non-small cell lung cancer, cabozantinib and crizotinib showed clear efficacy with a generally tolerable adverse events profile. In gastrointestinal cancers, most phase III trials of MET inhibitors showed negative results. In hepatocellular carcinoma, based on the encouraging results of some phase II studies, a series of phase III trials are currently recruiting patients to access the efficacy and safety of MET inhibitors.

Gastric adenocarcinoma

Gastric cancers, with gastric adenocarcinoma (GAC) as the most common histological type, impose a considerable global health burden. Although the screening strategies for early detection have been shown to be successful in Japan and South Korea, they are either not implemented or not feasible in most of the world, leading to late diagnosis in most patients. Helicobacter pylori infection contributes to the development of many endemic GACs, and pre-emptive eradication or early treatment of this bacterial infection might provide effective primary prevention. GACs are phenotypically and genotypically heterogeneous. Localized (clinical stage I) GAC is best treated either endoscopically or with limited surgical resection, but clinical stage II or stage III tumours require multidisciplinary adjunctive approaches in addition to surgery. Although GAC is highly treatable in its early stages, advanced (clinical stage IV) GAC has a median survival of just ∼9-10 months. However, detailed molecular and immune profiling of GAC is yielding promise; early studies with immune checkpoint inhibitors suggest that GAC is amenable to immune modulation. Molecular studies have yielded a vast quantity of new information for potential exploitation. Nevertheless, advances against GACs have lagged compared with other tumours of similar incidence, and more research is necessary to overcome the obstacles to prolong survival.

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.

Preclinical development of a humanized neutralizing antibody targeting HGF

Hepatocyte growth factor (HGF) and its receptor, cMET, play critical roles in cell proliferation, angiogenesis and invasion in a wide variety of cancers. We therefore examined the anti-tumor activity of the humanized monoclonal anti-HGF antibody, YYB-101, in nude mice bearing human glioblastoma xenografts as a single agent or in combination with temozolomide. HGF neutralization, The extracellular signal-related kinases 1 and 2 (ERK1/2) phosphorylation, and HGF-induced scattering were assessed in HGF-expressing cell lines treated with YYB-101. To support clinical development, we also evaluated the preclinical pharmacokinetics and toxicokinetics in cynomolgus monkeys, and human and cynomolgus monkey tissue was stained with YYB-101 to test tissue cross-reactivity. We found that YYB-101 inhibited cMET activation in vitro and suppressed tumor growth in the orthotopic mouse model of human glioblastoma. Combination treatment with YYB-101 and temozolomide decreased tumor growth and increased overall survival compared with the effects of either agent alone. Five cancer-related genes (TMEM119, FST, RSPO3, ROS1 and NBL1) were overexpressed in YYB-101-treated mice that showed tumor regrowth. In the tissue cross-reactivity assay, critical cross-reactivity was not observed. The terminal elimination half-life was 21.7 days. Taken together, the in vitro and in vivo data demonstrated the anti-tumor efficacy of YYB-101, which appeared to be mediated by blocking the HGF/cMET interaction. The preclinical pharmacokinetics, toxicokinetics and tissue cross-reactivity data support the clinical development of YYB-101 for advanced cancer.

Establishment of patient-derived gastric cancer xenografts: a useful tool for preclinical evaluation of targeted therapies involving alterations in HER-2, MET and FGFR2 signaling pathways

BACKGROUND

Targeted therapies are emerging treatment options for gastric cancer (GC). Patient-derived tumor xenograft(PDX) models of GC closely retain the features of the original clinical cancer, offering a powerful tool for preclinical drug efficacy testing. This study aimed to establish PDX GC models, and explore therapeutics targeting Her2, MET(cMet), and FGFR2, which may assist doctor to select the proper target therapy for selected patients.

METHODS

GC tissues from 32 patients were collected and implanted into immuno-deficient mice. Using immunohistochemistry(IHC) and fluorescent in-situ hybridization (FISH), protein levels and/or gene amplification of Her2, cMet and FGFR2 in those tissues were assessed. Finally, anti-tumor efficacy was tested in the PDX models using targeted inhibitors.

RESULTS

A total of 9 passable PDX models were successfully established from 32 gastric cancer xenograft donors, consisting of HER2,cMet and FGFR2 alterations with percentages of 4(12.5%), 8(25.0%) and 1(3.1%) respectively. Crizotinib and AZD4547 exerted marked antitumor effects exclusively in PDX models with cMet (G30,G31) and FGFR2(G03) amplification. Interestingly, synergistic antitumor activity was observed in G03 (FGFR2-amplifed and cMet non-amplified but IHC [2+]) with simultaneous treatment with Crizotinib and ADZ4547 at day 30 post-treatment. Further in vitro biochemistry study showed a synergistic inhibition of the MAPK/ERK pathway. HER2,cMet and FGFR2 alterations were found in 17 (10.4%), 32(19.6%) and 6(3.7%) in a group of 163 GC patients, and cMet gene amplification or protein overexpression(IHC 3+) was associated with poor prognosis.

CONCLUSIONS

These PDX GC models provide an ideal platform for drug screening and evaluation. GC patients with positive cMet or FGFR2 gene amplification may potentially benefit from cMet or FGFR2 targeted therapies or combined targeted therapy.

89Zr-DFO-AMG102 Immuno-PET to Determine Local Hepatocyte Growth Factor Protein Levels in Tumors for Enhanced Patient Selection

The hepatocyte growth factor (HGF) binding antibody rilotumumab (AMG102) was modified for use as a ⁸⁹Zr-based immuno-PET imaging agent to noninvasively determine the local levels of HGF protein in tumors. Because recent clinical trials of HGF-targeting therapies have been largely unsuccessful in several different cancers (e.g., gastric, brain, lung), we have synthesized and validated ⁸⁹Zr-DFO-AMG102 as a companion diagnostic for improved identification and selection of patients having high local levels of HGF in tumors. To date, patient selection has not been performed using the local levels of HGF protein in tumors. Methods: The chelator p-SCN-Bn-DFO was conjugated to AMG102, radiolabeling with ⁸⁹Zr was performed in high radiochemical yields and purity (>99%), and binding affinity of the modified antibody was confirmed using an enzyme-linked immunosorbent assay (ELISA)-type binding assay. PET imaging, biodistribution, autoradiography and immunohistochemistry, and ex vivo HGF ELISA experiments were performed on murine xenografts of U87MG (HGF-positive, MET-positive) and MKN45 (HGF-negative, MET-positive) and 4 patient-derived xenografts (MET-positive, HGF unknown). Results: Tumor uptake of ⁸⁹Zr-DFO-AMG102 at 120 h after injection in U87MG xenografts (HGF-positive) was high (36.8 ± 7.8 percentage injected dose per gram [%ID/g]), whereas uptake in MKN45 xenografts (HGF-negative) was 5.0 ± 1.3 %ID/g and a control of nonspecific human IgG ⁸⁹Zr-DFO-IgG in U87MG tumors was 11.5 ± 3.3 %ID/g, demonstrating selective uptake in HGF-positive tumors. Similar experiments performed in 4 different gastric cancer patient-derived xenograft models showed low uptake of ⁸⁹Zr-DFO-AMG102 (∼4-7 %ID/g), which corresponded with low HGF levels in these tumors (ex vivo ELISA). Autoradiography, immunohistochemical staining, and HGF ELISA assays confirmed that elevated levels of HGF protein were present only in U87MG tumors and that ⁸⁹Zr-DFO-AMG102 uptake was closely correlated with HGF protein levels in tumors. Conclusion: The new immuno-PET imaging agent ⁸⁹Zr-DFO-AMG102 was successfully synthesized, radiolabeled, and validated in vitro and in vivo to selectively accumulate in tumors with high local levels of HGF protein. These results suggest that ⁸⁹Zr-DFO-AMG102 would be a valuable companion diagnostic tool for the noninvasive selection of patients with elevated local concentrations of HGF in tumors for planning any HGF-targeted therapy, with the potential to improve clinical outcomes.

Chemotherapy for advanced gastric cancer: future perspective in Japan

Differences in clinical outcomes between advanced gastric cancer (AGC) in Asia and that in other regions have been discussed for a long time, although no major significant differences in molecular profiles have been reported. The anti-human epidermal growth factor receptor 2 antibody trastuzumab and the anti-vascular endothelial growth factor receptor 2 monoclonal antibody ramucirumab were both approved as a treatment for AGC on the basis of global phase 3 trials including Japan. In recent years, others new agents for treatment of AGC have been investigated in global or Asian studies. Randomized phase 2 trials in Japan showed a higher response rate to S-1 plus leucovorin and oxaliplatin than to standard S-1 plus cisplatin, which is the rationale for an ongoing phase 3 trial in Asia (SOLAR trial). A recent global phase 1 trial of the anti-programmed cell death 1 monoclonal antibody pembrolizumab showed similar efficacy results in Asian patients and non-Asian patients, which led to large global phase 2 and phase 3 studies. Although the perspective of treatment of AGC in the near future depends on the results of ongoing large clinical trials, individualized choice of treatment based on more detailed molecular information will become important.

[Novel pharmaceutical treatment approaches for gastric cancer]

This review article delineates novel approaches for the pharmaceutical treatment of gastric cancer. A newly developed molecular classification of gastric cancer based on histology, genetic, epigenetic and proteomic characteristics has evolved. It provides a road map for development of new drugs and combinations as well as for patient stratification in clinical research and it is expected to be introduced into clinical practice in the near future. Anti-HER2 targeted treatment is a validated strategy for treatment of metastatic gastric cancer and is now also being studied in the perioperative setting to increase response rates and ultimately survival in patients undergoing curative surgery; however, the resistance mechanisms of HER2-targeted treatment are poorly understood and optimal patient selection remains challenging. Targeting angiogenesis is a novel concept in the management of advanced gastric cancer. Ramucirumab is an antibody against vascular endothelial growth factor receptor 2 (VEGFR2) and prolongs survival in second-line treatment as a monotherapy and also in combination with paclitaxel; however, biomarkers for selection of patients who particularly benefit from antiangiogenic treatment are still lacking. Immune checkpoint blockade and inhibition of cancer stem cell targets are two emerging principles for the medicinal treatment of gastric cancer. Large-scale international studies for evaluation of these treatment approaches are ongoing. In summary, promising biology-based treatment strategies are evolving; however, tumor heterogeneity, which is an inherent feature of gastric cancer is a particular challenge for the development of targeted medications and a personalized treatment.

Global chemotherapy development for gastric cancer

To combat the dismal mortality rates from metastatic gastric adenocarcinoma (GAC), new drugs and treatment strategies are needed. Today, metastatic GAC is predominantly treated by empiric chemotherapy. Combination of two cytotoxic agents has become commonplace in North America, Europe, and Asia. Human epidermal growth factor 2 (HER2) overexpression (protein or gene copy numbers) has resulted in the addition of trastuzumab in the first-line chemotherapy combination in patients whose tumor is HER2 positive. The addition of trastuzumab in this select population has provided a modest survival advantage. In this review we trace the global development of systemic therapy in patients with metastatic GAC and ponder what lies in the future.

Targeted therapies for advanced and metastatic adenocarcinoma of the gastroesophageal junction: is there something new?

Despite improvements in systemic chemotherapy (CT), the prognosis of metastatic adenocarcinoma of the gastroesophageal junction remains poor. Over the years, new targeting agents have become available and were tested, with or without CT, in first or subsequent lines of therapy. The epidermal growth factor receptor family was targeted with monoclonal antibodies (MoAbs) (trastuzumab, cetuximab, panitumumab) and tyrosin kinase inhibitors (TKIs) (lapatinib, erlotinib, gefitinib). Only trastuzumab, in combination with cisplatin and fluoropyrimidines, significantly improved overall survival (OS) in first-line therapy (13.8 vs. 11.1 months). Angiogenesis also was targeted with MoAbs (bevacizumab and ramucirumab); ramucirumab, a vascular endothelial growth factor-receptor 2 antagonist, enhanced OS in two phase III studies in the first (9.6 vs. 7.4 months) and subsequent lines of treatment (5.2 vs. 3.8 months), while the bevacizumab study was negative. TKIs (sunitinib, sorafenib, regorafenib, apatinib) were tested in this setting in phase II studies in the second/third line, only showing modest antitumor activity. The hepatocyte growth factor receptor (MET) was targeted in untreated patients in a phase III trial with MoAb rilotumumab, with or without CT, but the study was stopped because of mortality excess in the rilotumumab arm. Mammalian target of rapamycin (MTOR) pathway inhibition with everolimus was tested in pretreated patients in a placebo-controlled phase III trial who failed to improve OS (5.4 vs. 4.3 months). In conclusion, considering the modest survival gain obtained overall, the high cost of these therapies and the quality of life issue must be primarily considered in treating these patients.

MET tyrosine kinase receptor expression and amplification as prognostic biomarkers of survival in gastroesophageal adenocarcinoma

BACKGROUND

MET gene amplification and Met protein overexpression may be associated with a poor prognosis. The MET/Met status is typically determined with fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC), respectively. Targeted proteomics uses mass spectrometry–based selected reaction monitoring (SRM) to accurately quantitate Met expression. FISH, IHC, and SRM analyses were compared to characterize the prognostic value of MET/Met in gastroesophageal adenocarcinoma (GEC).

METHODS

Samples from 447 GEC patients were analyzed for MET gene amplification (FISH) and Met protein expression (IHC and SRM). Cox proportional hazards models and Kaplan‐Meier estimates were applied to explore relations between Met, overall survival (OS), and clinical/pathological characteristics. Spearman's rank coefficient was used to assess the correlation between parameters.

RESULTS

Patients with MET‐amplified tumors had worse OS when: the MET/centromere enumeration probe for chromosome 7 FISH ratio was ≥ 2 (hazard ratio [HR], 3.13; 95% confidence interval [CI], 1.84‐5.33), the MET gene copy number was ≥5 (HR, 2.51; 95% CI, 1.45‐4.34), or ≥ 10% of the cells had ≥15 copies (HR, 4.28; 95% CI, 2.18‐8.39). Similar observations were made with Met protein overexpression by IHC (≥1 + intensity in ≥ 25% of the tumor cell membrane: HR, 1.39; 95% CI, 1.04‐1.86) or SRM (≥400 amol/μg: HR, 1.76; 95% CI, 1.06‐2.90). A significant correlation was observed between MET FISH/Met IHC, MET FISH/Met SRM, and Met IHC/Met SRM; only MET FISH and Met SRM were independent negative prognostic biomarkers in multivariate analyses.

CONCLUSIONS

MET amplification and overexpression, assessed by multiple methods, were associated with a worse prognosis in univariate analyses. However, only MET amplification by FISH and Met expression by SRM were independent prognostic biomarkers. Compared with IHC, SRM may provide an added benefit for informed decisions about Met‐targeted therapy. Cancer 2017;123:1061–70. © 2016 American Cancer Society.

In a large study, MET gene amplification, Met protein overexpression, or both, as assessed by various assays, are associated with a poor prognosis in univariate analyses. However, only MET amplification by fluorescence in situ hybridization and Met expression by selected reaction monitoring mass spectrometry are independent prognostic biomarkers; compared with immunohistochemistry, selected reaction monitoring may provide an added benefit for informed decisions about Met‐targeted therapy.

Acquired METD1228V Mutation and Resistance to MET Inhibition in Lung Cancer

Amplified and/or mutated MET can act as both a primary oncogenic driver and as a promoter of tyrosine kinase inhibitor (TKI) resistance in non-small cell lung cancer (NSCLC). However, the landscape of MET-specific targeting agents remains underdeveloped, and understanding of mechanisms of resistance to MET TKIs is limited. Here, we present a case of a patient with lung adenocarcinoma harboring both a mutation in EGFR and an amplification of MET, who after progression on erlotinib responded dramatically to combined MET and EGFR inhibition with savolitinib and osimertinib. When resistance developed to this combination, a new MET kinase domain mutation, D1228V, was detected. Our in vitro findings demonstrate that METD1228V induces resistance to type I MET TKIs through impaired drug binding, while sensitivity to type II MET TKIs is maintained. Based on these findings, the patient was treated with erlotinib combined with cabozantinib, a type II MET inhibitor, and exhibited a response.

SIGNIFICANCE

With several structurally distinct MET inhibitors undergoing development for treatment of NSCLC, it is critical to identify mechanism-based therapies for drug resistance. We demonstrate that an acquired METD1228V mutation mediates resistance to type I, but not type II, MET inhibitors, having therapeutic implications for the clinical use of sequential MET inhibitors. Cancer Discov; 6(12); 1334-41. ©2016 AACR.See related commentary by Trusolino, p. 1306This article is highlighted in the In This Issue feature, p. 1293.

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.