HER2, MET and FGFR2 oncogenic driver alterations define distinct molecular segments for targeted therapies in gastric carcinoma

A phase II study of cabozantinib and pembrolizumab in advanced gastric/gastroesophageal adenocarcinomas resistant or refractory to immune checkpoint inhibitors

BACKGROUND

Most patients with metastatic gastroesophageal adenocarcinoma (mGEA) progress on immune checkpoint inhibitors (ICIs). Novel approaches to overcome resistance to ICI in mGEA are needed. Cabozantinib is a multi-tyrosine kinase inhibitor thought to enhance the immunomodulatory effects of ICI. This study evaluated the combination of cabozantinib and pembrolizumab in ICI refractory or resistant mGEA.

METHODS

Investigator-initiated, single-arm, single institution, and phase II study in patients with mGEA. Patients had progressed on ICI and/or had PD-L1 CPS score ≤10%. Cabozantinib dose was 40 mg p.o. daily on days 1-21 of a 21-day cycle, with pembrolizumab 200 mg i.v. on day 1. The primary endpoint was progression-free survival at 6 months (PFS-6).

RESULTS

Twenty-seven patients were enrolled. Median age 58 years (24-87), female (n = 14), ECOG 0/1 = 13/14, GC/GEJ = 16/11, and non-Hispanic White/Hispanic/Asian = 12/8/7. The primary endpoint was met. After a median follow-up of 31.4 months (range 3.3-42.5), PFS-6 was 22.2% (95% CI 9.0-39.0). The median PFS and OS are 2.3 months (95% CI 1.7-4.1) and 5.5 months (3.1-14.0), respectively. The most common mutations were TP53 (78.3%) and CDH1/PIK3CA/CTNNB1 (17.4% each). The most common grade (G) treatment-related adverse events (TRAE) were diarrhea (25.9%), fatigue (18.5%), hypertension, and muscle cramps (14.8% each). G3-4 TRAE were seen in n = 3 patients (hypertension, thromboembolic event, esophageal perforation; each n = 1). No G5 was observed.

CONCLUSIONS

The addition of cabozantinib to pembrolizumab shows clinical benefit in ICI-resistant or refractory mGEA with a tolerable safety profile. (ClinicalTrials.gov Identifier: NCT04164979. IRB Approved: UCI 18-124, University of California Irvine IRB#20195426.).

Targeted therapy for multiple gene mutations in multiple metastases of advanced gastric cancer: a case report

In China, gastric cancer is the second most common cause of cancer-related death, after lung cancer. At present, the morbidity and mortality rates of gastric cancer are increasing, and targeted therapy for gastric cancer has become a research hotspot. Herein, we report a patient with multiple metastases from advanced gastric cancer. After identifying MET gene amplification, initial treatment induced regression of the tumor. However, in later stages, due to the overexpression or mutation of HER-2, KRAS, TP53, and other genes, the targeted drug therapy became ineffective, and the disease progressed rapidly, leading to the death of the patient.

Futibatinib, an Irreversible FGFR1-4 Inhibitor for the Treatment of FGFR-Aberrant Tumors

Fibroblast growth factor receptors (FGFR) are emerging as an important therapeutic target for patients with advanced, refractory cancers. Most selective FGFR inhibitors under investigation show reversible binding, and their activity is limited by acquired drug resistance. This review summarizes the preclinical and clinical development of futibatinib, an irreversible FGFR1-4 inhibitor. Futibatinib stands out among FGFR inhibitors because of its covalent binding mechanism and low susceptibility to acquired resistance. Preclinical data indicated robust activity of futibatinib against acquired resistance mutations in the FGFR kinase domain. In early-phase studies, futibatinib showed activity in cholangiocarcinoma, and gastric, urothelial, breast, central nervous system, and head and neck cancers harboring various FGFR aberrations. Exploratory analyses indicated clinical benefit with futibatinib after prior FGFR inhibitor use. In a pivotal phase II trial, futibatinib demonstrated durable objective responses (42% objective response rate) and tolerability in previously treated patients with advanced intrahepatic cholangiocarcinoma harboring FGFR2 fusions or rearrangements. A manageable safety profile was observed across studies, and patient quality of life was maintained with futibatinib treatment in patients with cholangiocarcinoma. Hyperphosphatemia, the most common adverse event with futibatinib, was well managed and did not lead to treatment discontinuation. These data show clinically meaningful benefit with futibatinib in FGFR2-rearrangement-positive cholangiocarcinoma and provide support for further investigation of futibatinib across other indications. Future directions for this agent include elucidating mechanisms of resistance and exploration of combination therapy approaches.

Targeting FGFR2 Positive Gastroesophageal Cancer: Current and Clinical Developments

Despite recent advances in the systemic treatment of gastroesophageal cancers, prognosis remains poor. Comprehensive molecular analyses have characterized the genomic landscape of gastroesophageal cancer that has established therapeutic targets such as human epidermal growth factor receptor 2 (HER2), vascular endothelial growth factor receptor (VEGFR) and programmed death ligand 1 (PD-L1). The aberrant fibroblast growth factor receptor 2 (FGFR2) pathway is attractive for targetable therapy with FGFR inhibition based on preclinical data showing a pivotal role in the progression of gastric cancer (GC). FGFR2 amplification is the most common FGFR2 gene aberration in gastroesophageal cancer, and most associated with diffuse GC, which is often linked to poorer prognostic outcomes. There has been considerable progress with drug development focused on FGFR inhibition. At present, there is no approved FGFR inhibitor for FGFR2 positive gastroesophageal cancer. A selective FGFR2b monoclonal antibody bemarituzumab is currently being investigated in the first phase III randomized trial for patients with first line advanced GC, which may change the treatment paradigm for FGFR2b positive GC. The role of FGFR signalling, specifically FGFR2, is less established in oesophageal squamous cell cancer (ESCC) with a paucity of evidence for clinical benefit in these patients. Precision medicine is part of the wider approach in gastrointestinal cancers; however, it can be challenging due to heterogeneity and here circulating tumour DNA (ctDNA) for patient selection may have future clinical utility. In our review, we outline the FGFR pathway and focus on the developments and challenges of targeting FGFR2 driven gastroesophageal cancers.

Hepatocyte Growth Factor Enhances Antineoplastic Effect of 5-Fluorouracil by Increasing UPP1 Expression in HepG2 Cells

Aberrant activation of hepatocyte growth factor (HGF) and its receptor c-Met axis promotes tumor growth. Therefore, many clinical trials have been conducted. A phase 3 trial investigating a monoclonal antibody targeting HGF in combination with fluoropyrimidine-based chemotherapy had to be terminated prematurely; however, the reason behind the failure remains poorly defined. In this study, we investigated the influence of HGF on the antineoplastic effects of 5-fluorouracil (5-FU), a fluoropyrimidine, in HepG2 cells. HGF suppressed the proliferative activity of cells concomitantly treated with 5-FU more robustly as compared to that of cells treated with 5-FU alone, and markedly increased the expression of uridine phosphorylase 1 (UPP1). Intracellular concentration of 5-fluorouridine, an initial anabolite of 5-FU catalyzed by UPP1, was increased by HGF. Interestingly, erlotinib enhanced HGF-induced increase in UPP1 mRNA; in contrast, gefitinib suppressed it. Furthermore, erlotinib suppressed HGF-increased phosphorylation of the epidermal growth factor receptor at the Tyr1173 site involved in downregulation of extracellular signal-regulated kinase (Erk) activation, and enhanced the HGF-increased phosphorylation of Erk. Collectively, these findings suggest that inhibition of the HGF/c-Met axis diminishes the effects of fluoropyrimidine through downregulation of UPP1 expression. Therefore, extreme caution must be exercised in terms of patient safety while offering chemotherapy comprising fluoropyrimidine concomitantly with inhibitors of the HGF/c-Met axis.

Receptor Tyrosine Kinases Amplified in Diffuse-Type Gastric Carcinoma: Potential Targeted Therapies and Novel Downstream Effectors

Simple Summary

Diffuse-type gastric carcinoma (DGC) is an aggressive subtype of gastric carcinoma with an extremely poor prognosis due to frequent peritoneal metastasis and high probability of recurrence. Its pathogenesis is poorly understood, and consequently, no effective molecular targeted therapy is available. The importance of oncogenic receptor tyrosine kinase (RTK) signaling has been recently demonstrated in the malignant progression of DGC. In particular, RTK gene amplification appears to accelerate peritoneal metastasis. In this review, we provide an overview of RTK gene amplification in DGC and the potential of related targeted therapies.

Abstract

Gastric cancer (GC) is a major cause of cancer-related death worldwide. Patients with an aggressive subtype of GC, known as diffuse-type gastric carcinoma (DGC), have extremely poor prognoses. DGC is characterized by rapid infiltrative growth, massive desmoplastic stroma, frequent peritoneal metastasis, and high probability of recurrence. These clinical features and progression patterns of DGC substantially differ from those of other GC subtypes, suggesting the existence of specific oncogenic signals. The importance of gene amplification and the resulting aberrant activation of receptor tyrosine kinase (RTK) signaling in the malignant progression of DGC is becoming apparent. Here, we review the characteristics of RTK gene amplification in DGC and its importance in peritoneal metastasis. These insights may potentially lead to new targeted therapeutics.

Targeting MET amplification in Gastro-oesophageal (GO) malignancies and overcoming MET inhibitor resistance: challenges and opportunities

INTRODUCTION

MET, the hepatocyte growth factor receptor is amplified in 8% of gastroesophageal (GO) malignancies and associated with poor prognosis. Therapeutic targeting of MET amplification and MET mutations has the potential to improve outcomes for patients with GO cancers (GOC).

AREAS COVERED

The efficacy of MET inhibition (METi) in preclinical studies has yet to translate into meaningful improvements in the treatment paradigm for unselected GOC. MET amplification has been proposed as a superior modality for patient selection; however even if confirmed, frequency and duration of response to METi are limited by rapid activation of primary and secondary resistance pathways. These observations illustrate the challenges inherent in the application of precision oncology predicated on the theory of oncogenic addiction.

EXPERT OPINION

A standardized definition of MET positivity is critical to enhance patient selection. Early successes targeting the METex14 skipping mutation demonstrate the potent therapeutic effects of METi in a clearly molecularly defined cohort. There is robust preclinical rationale and early-phase data supporting exploitation of immune system interaction with MET. Pragmatic investigation of rational therapeutic combinations based on molecular profiling of both primary and metastatic disease sites with sequential circulating tumor DNA analysis can inform successful clinical development of METi agents in GOC.

Intra-tumoral FGFR2 Expression Predicts Prognosis and Chemotherapy Response in Advanced HER2-positive Gastric Cancer Patients

BACKGROUND/AIM

This study aimed to evaluate the relationship between clinical outcomes and intra-tumoral fibroblast growth factor receptor 2 (FGFR2) expression in human epidermal growth factor receptor 2 (HER2)-positive gastric cancer (GC) patients who had undergone HER2-targeted chemotherapy.

PATIENTS AND METHODS

A retrospective analysis was performed in 22 patients with HER2-positive GC, who had undergone systemic chemotherapy. We performed immunohistochemistry staining of FGFR2 expression using surgically resected specimens or biopsied samples and evaluated clinicopathological characteristic and overall survival (OS) in the FGFR2-negative and -positive GC groups.

RESULTS

A total of 8 and 14 patients were placed in the FGFR2-negative and -positive group, respectively. The median OS rates were 56.2 and 16.0 months in the FGFR2-negative and -positive groups, respectively. The FGFR2-negative group had a significantly better prognosis after HER2-targeted chemotherapy [p=0.027 (log-rank test)]. The univariate analysis revealed that performing gastrectomy, response to combination chemotherapy with trastuzumab, and FGFR2 positivity were significantly correlated with OS. In a multivariate analysis, the response to combination chemotherapy with trastuzumab (p=0.008) was significantly correlated with OS. In addition, the proportions of patients who showed CR or PR in response to chemotherapy were 87.5 and 42.9% in the FGFR2-negative and -positive groups, respectively (p=0.031).

CONCLUSION

HER2-positive GC patients, without overexpression of FGFR2, exhibited an improved prognosis and response rate to trastuzumab combination chemotherapy. Assessment of intra-tumoral FGFR2 expression could be helpful in predicting the prognosis and response to trastuzumab in HER2-positive GC patients.

Transferrin receptor 1 promotes the fibroblast growth factor receptor-mediated oncogenic potential of diffused-type gastric cancer

Diffuse-type gastric cancer (DGC) is a highly invasive subtype of gastric adenocarcinoma that frequently exhibits scattered peritoneal metastasis. Previous studies have shown that the genes of receptor tyrosine kinases (RTKs), such as fibroblast growth factor receptor 2 (FGFR2) or Met, are amplified in some DGC cell lines, leading to the constitutive activation of corresponding RTKs. In these cell lines, the survival of cancer cells appears to be dependent on the activation of RTKs. To gain novel insights into the downstream signaling pathways of RTKs specific to DGC, phosphotyrosine-containing proteins associated with activated FGFR2 were purified through two sequential rounds of immunoprecipitation from the lysates of two DGC cell lines. As a result, transferrin receptor 1 (TfR1) was identified as the binding partner of FGFR2. Biochemical analysis confirmed that TfR1 protein binds to FGFR2 and is phosphorylated at tyrosine 20 (Tyr20) in an FGFR2 kinase activity-dependent manner. The knockdown of TfR1 and treatment with an inhibitor of FGFR2 caused significant impairment in iron uptake and suppression of cellular proliferation in vitro. Moreover, the suppression of expression levels of TfR1 in the DGC cells significantly reduced their tumorigenicity and potency of peritoneal dissemination. It was indicated that TfR1, when phosphorylated by the binding partner FGFR2 in DGC cells, promotes proliferation and tumorigenicity of these cancer cells. These results suggest that the control of TfR1 function may serve as a therapeutic target in DGC with activated FGFR2.

The Relationship Between D-dimer and Prognosis in the Patients with Serum Alpha-Fetoprotein-Positive Gastric Cancer: A Retrospective Cohort Study

Background:

Alpha-fetoprotein-positive gastric cancer (AFPGC) is a subtype of gastric cancer that is rare in clinical practice and extremely malignant. Malignant tumors are often associated with hemorrhage, thrombosis, and even disseminated intravascular coagulation (DIC). The D-dimer test is used as a sensitive index in the diagnosis of DIC and fresh thrombosis in malignant tumors. Therefore, this study aims to investigate the relationship between D-dimer values and the clinical characteristics and prognosis of patients with serum AFPGC (AFP ⩾ 15 μg/L) patients.

Methods:

Overall, 120 healthy subjects and 120 AFP-negative gastric cancer (AFP < 15μg/L) patients from May 2017 to July 2018 at the Shanxi Cancer Hospital served as the control group in this retrospective cohort study. Additionally, 120 patients with pretreatment advanced serum AFP were chosen to analyze clinicopathologic features and factors that affect prognosis. The predictor was the D-dimer, and the outcome variable was overall survival (OS). Other variables included age, sex, tumor site, T-stage, distant metastasis, and preoperative serum tumor biomarkers. Differences in OS rate were analyzed by GraphPad Prism 9.2.0.332. The Cox regression model was used for univariate and multivariate analysis.

Results:

In comparison to AFP-negative gastric cancer, we discovered that D-dimer had a meaningfully higher presentation in patients with AFPGC (P < .001). Based on D-dimer median levels, the AFPGC patients were divided into two groups, including 39 patients with low D-dimer (<1000 ng/mL) and 81 patients with high D-dimer (⩾1000 ng/mL). The variables, including T-stage, distant metastasis, and expression of HER2, were associated with the value of D-dimer. The D-dimer levels were weakly related to the levels of tumor markers. The differences in AFPGC patients, with an OS rate of 30.76% for patients with low D-dimer (<1000) and 12.30% with high D-dimer (⩾1000; P = .0027), were statistically significant. Cox multivariate analysis of various parameters indicated that T-stage, distant metastasis, vascular embolism, level of D-dimer, and tumor biomarkers of AFP were independent risk factors for survival.

Conclusion:

Serum D-dimer levels may be a valuable indicator for predicting AFPGC metastasis and progression.

The beginning of the era of precision medicine for gastric cancer with fibroblast growth factor receptor 2 aberration

Despite recent advances in the systemic treatment of metastatic gastric cancer (GC), prognostic outcomes remain poor. Considerable research effort has been invested in characterizing the genomic landscape of GC and identifying potential therapeutic targets. FGFR2 is one of the most attractive targets because aberrations in this gene are frequently associated with GC, particularly the diffuse type in Lauren's classification, which confers an unfavorable prognosis. Based on the preclinical data, the FGFR2 signaling pathway plays a key role in the development and progression of GC, and several FGFR inhibitors have been clinically assessed. However, the lack of robust treatment efficacy has hampered precision medicine for patients with FGFR2-aberrant GC. Recently, the clinical benefits of the FGFR2-IIIb-selective monoclonal antibody bemarituzumab for FGFR2b-positive GC patients were shown in a randomized phase II FIGHT trial of bemarituzumab combined with the first-line chemotherapy. This trial demonstrates proof of concept, suggesting that FGFR2 is a relevant therapeutic target for patients with FGFR2b-positive GC and that bemarituzumab brings new hope for diffuse-type GC patients. In this review, we summarize the oncogenic roles of FGFR2 signaling and highlight the most recent advances in FGFR inhibitors based on the findings of pivotal clinical trials for patients with FGFR2-aberrant GC. Thus, the era of precision medicine for patients with FGFR2-aberrant GC will be opened.

Combination treatment with trastuzumab and crizotinib in metastatic gastric cancer harboring Her-2 amplification and c-MET amplification: A case report

RATIONALE

Metastatic gastric cancer patients with poor eastern cooperative oncology group performance status (PS) (≥3) were lack of effective anti-tumor strategies. They always lived with poor PS, severe and multiple symptoms, and usually resulted in extremely limited survival time. Herein, we reported a patient diagnosed with gastric cancer metastasized to multiple bones, along with lymphangitis carcinomatosa in lungs, harboring Her-2 and c-MET amplification with poor PS, positively responded to combinational therapy with trastuzumab and crizotinib.

PATIENT CONCERNS

The patient complained of persistent cough and fatigue for 2 months, otherwise, she denied smoking, alcohol history, or any other medical or family history.

DIAGNOSIS

With the biopsy results from gastroscopy, as well as computer tomography for chest and abdomen, the patient was diagnosed as gastric adenocarcinoma, with metastasis on lungs, left adrenal gland, retroperitoneal lymph nodes, and multiple bones.

INTERVENTIONS

Because of the poor PS (PS = 3), as well as Her-2 and c-MET amplification, the patient received combination treatment with trastuzumab and crizotinib as salvage strategy.

OUTCOMES

After 2 months' exposure of trastuzumab and crizotinib, symptoms including persistent cough, and chest distress were alleviated significantly. Simultaneously, chest computer tomography showed significant dissipation of lymphangitis carcinomatosa, as well as apparent reduction of pleural effusion. No adverse reactions including nausea, vomiting, diarrhea, or hypertension was observed during the following 2 months.

LESSONS

The present case suggested that combinational therapy with trastuzumab and crizotinib might be effective in metastatic gastric cancer patients harboring Her-2 and c-MET amplification, even with a poor PS. It was also implied that gene sequencing might be valuable, especially in patients with limited treatment strategies.

Harnessing biomarkers of response to improve therapy selection in esophago-gastric adenocarcinoma

Advanced esophago-gastric (OG) adenocarcinomas have a high mortality rate and new therapeutic options are urgently required. Despite recent advances in understanding the molecular characteristics of OG cancers, tumor heterogeneity poses a challenge in developing new therapeutics capable of improving patient outcomes. Consequently, chemotherapy remains the mainstay of systemic treatment, with the HER2 being the only predictive biomarker routinely targeted in clinical practice. Recent data indicate that immunotherapy will be incorporated into first-line chemotherapy, but further research is required to refine patient selection. This review will summarize the clinical strategies being evaluated to utilize our knowledge of predictive biomarkers with reference to novel therapeutics, and discuss the barriers to implementing precision oncology in OG adenocarcinoma.

Quantitation of ligand is critical for ligand-dependent MET signalling activation and determines MET-targeted therapeutic response in gastric cancer

BACKGROUND

Despite the promising preclinical antitumor activity of MET-targeting therapies, most clinical trials have failed. We introduced a new concept of quantitation of stroma-induced hepatocyte growth factor (HGF) to assess the actual MET signalling activity in gastric cancer (GC).

METHODS

We treated serially diluted HGF and conditioned media (CM) from cancer-associated fibroblasts (CAFs) on low MET-expressing cancer cells and investigated the phenotypical and signalling changes. Stromal proportion and MET expression in GC samples were assessed, and gene set enrichment analysis (GSEA) from the public database was performed. The antitumor effect of anti-MET treatment was examined, especially when cancer cells were activated in a ligand-dependent manner.

RESULTS

Relatively high doses of HGF or high-concentrated CM fully activated MET signalling cascades and promoted cell proliferation/invasion. High stromal proportion denoted worse patient survival in MET-positive GCs than in MET-negative ones. GSEA showed that the gene sets regarding proliferation, migration, and CAF as well as MET pathway signature were enriched in simultaneously MET- and HGF-positive samples. Sufficient ligand-dependent MET signalling activation increased the sensitivity to crizotinib.

CONCLUSIONS

We conclude that patients whose tumours have a high stromal proportion and at least low MET expression may benefit more from MET-targeted therapies.

Clinical difference between fibroblast growth factor receptor 2 subclass, type IIIb and type IIIc, in gastric cancer

Fibroblast growth factor receptor 2 (FGFR2) has two isoforms: IIIb type and IIIc type. Clinicopathologic significance of these two FGFR2 subtypes in gastric cancer remains to be known. This study aimed to clarify the clinicopathologic difference of FGFR2IIIb and/or FGFR2IIIc overexpression. A total of 562 patients who underwent gastrectomy was enrolled. The expressions of FGFR2IIIb and FGFR2IIIc were retrospectively examined by immunohistochemistry or fluorescence in situ hybridization (FISH) using the 562 gastric tumors. We evaluated the correlation between clinicopathologic features and FGFR2IIIb overexpression and/or FGFR2IIIc overexpression in gastric cancer. FGFR2IIIb overexpression was observed in 28 cases (4.9%), and FGFR2IIIc overexpression was observed in four cases (0.7%). All four FGFR2IIIc cases were also positive for FGFR2IIIb, but not in the same cancer cells. FGFR2IIIb and/or FGFR2IIIc overexpression was significantly correlated with lymph node metastasis and clinical stage. Both FGFR2IIIb and FGFR2IIIc were significantly associated with poor overall survival. A multivariate analysis showed that FGFR2IIIc expression was significantly correlated with overall survival. FISH analysis indicated that FGFR2 amplification was correlated with FGFR2IIIb and/or FGFR2IIIc overexpression. These findings suggested that gastric tumor overexpressed FGFR2IIIc and/or FGFR2IIIb at the frequency of 4.9%. FGFR2IIIc overexpression might be independent prognostic factor for patients with gastric cancer.

Cell-free tumour DNA analysis detects copy number alterations in gastro-oesophageal cancer patients

BACKGROUND

Analysis of cell-free tumour DNA, a liquid biopsy, is a promising biomarker for cancer. We have performed a proof-of principle study to test the applicability in the clinical setting, analysing copy number alterations (CNAs) in plasma and tumour tissue from 44 patients with gastro-oesophageal cancer.

METHODS

DNA was isolated from blood plasma and a tissue sample from each patient. Array-CGH was applied to the tissue DNA. The cell-free plasma DNA was sequenced by low-coverage whole-genome sequencing using a clinical pipeline for non-invasive prenatal testing. WISECONDOR and ichorCNA, two bioinformatic tools, were used to process the output data and were compared to each other.

RESULTS

Cancer-associated CNAs could be seen in 59% (26/44) of the tissue biopsies. In the plasma samples, a targeted approach analysing 61 regions of special interest in gastro-oesophageal cancer detected cancer-associated CNAs with a z-score >5 in 11 patients. Broadening the analysis to a whole-genome view, 17/44 patients (39%) had cancer-associated CNAs using WISECONDOR and 13 (30%) using ichorCNA. Of the 26 patients with tissue-verified cancer-associated CNAs, 14 (54%) had corresponding CNAs in plasma. Potentially clinically actionable amplifications overlapping the genes VEGFA, EGFR and FGFR2 were detected in the plasma from three patients.

CONCLUSIONS

We conclude that low-coverage whole-genome sequencing without prior knowledge of the tumour alterations could become a useful tool for cell-free tumour DNA analysis of total CNAs in plasma from patients with gastro-oesophageal cancer.

[Intratumoral heterogeneity of gastric cancer-impact on biomarker evaluation]

BACKGROUND

Gastric carcinomas often measure more than 5 cm at primary diagnosis. Predictive biomarker testing is usually carried out on tissue biopsies, which do not represent the entire tumor biology and intratumoral heterogeneity.

OBJECTIVES

The aim of this study was to explore gastric cancer's intratumoral heterogeneity and its impact on the evaluation of predictive and prognostic biomarkers.

MATERIALS AND METHODS

The study cohort consisted of approximately 500 patients with therapy-naive adenocarcinomas of the stomach or the esophagogastric junction. The following biomarkers were determined: HER2, MET, Ki67, PD-L1/PD‑1, VISTA, EBV-status, and PIK3CA.

RESULTS

All examined biomarkers were influenced by gastric cancer's intratumoral heterogeneity. Tissue biopsies might carry the risk of sampling errors, which may significantly hamper adequate tumor classification in a clinical setting.

CONCLUSIONS

Our findings unravel issues of tumor heterogeneity in gastric cancer. Biomarker diagnostics on tissue biopsies should be carried out on at least five biopsies of different tumor areas. If possible, biomarker diagnostics should be repeated on resection specimens. Tissue microarrays should no longer be used for research studies of gastric cancer.

SATB1-Mediated Upregulation of the Oncogenic Receptor Tyrosine Kinase HER3 Antagonizes MET Inhibition in Gastric Cancer Cells

MET-amplified gastric cancer cells are extremely sensitive to MET inhibition in vitro, whereas clinical efficacy of MET inhibitors is disappointing. The compensatory activation of other oncogenic growth factor receptors may serve as an underlying mechanism of resistance. In this study, we analyzed the role of HER receptors, in particular HER3 and its ligand heregulin, in this respect. This also included the chromatin-organizer protein SATB1, as an established regulator of HER expression in other tumor entities. In a panel of MET-amplified gastric carcinoma cell lines, cell growth under anchorage-dependent and independent conditions was studied upon inhibitor treatment or siRNA-mediated knockdown. Expression analyses were performed using RT-qPCR, FACS, and immunoblots. Signal transduction was monitored via antibody arrays and immunoblots. As expected, MET inhibition led to a growth arrest and inhibition of MAPK signaling. Strikingly, however, this was accompanied by a rapid and profound upregulation of the oncogenic receptor HER3. This finding was determined as functionally relevant, since HER3 activation by HRG led to partial MET inhibitor resistance, and MAPK/Akt signaling was even found enhanced upon HRG+MET inhibitor treatment compared to HRG alone. SATB1 was identified as mediator of HER3 upregulation. Concomitantly, SATB1 knockdown prevented upregulation of HER3, thus abrogating the HRG-promoted rescue from MET inhibition. Taken together, our results introduce the combined HER3/MET inhibition as strategy to overcome resistance towards MET inhibitors.

MET Inhibitors for the Treatment of Gastric Cancer: What's Their Potential?

Gastric cancer remains a disease with a dismal prognosis. Extensive efforts to find targetable disease drivers in gastric cancer were implemented to improve patient outcomes. Beyond anti-HER2 therapy, MET pathway seems to be culprit of cancer invasiveness with MET-overexpressing tumors having poorer prognosis. Tyrosine kinase inhibitors targeting the HGF/MET pathway were studied in MET-positive gastric cancer, but no substantial benefit was proven. Some patients responded in early phase trials but later developed resistance. Others failed to show any benefit at all. Etiologies of resistance may entail inappropriate patient selection with a lack of MET detection standardization, tumor alternative pathways, variable MET amplification, and genetic variation. Optimizing MET detection techniques and better understanding the MET pathway, as well as tumor bypass mechanisms, are an absolute need to devise means to overcome resistance using targeted therapy alone, or in combination with other synergistic agents to improve outcomes of patients with MET-positive GC.

Protein expression-based classification of gastric cancer by immunohistochemistry of tissue microarray

Recently, the Cancer Genome Atlas and Asian Cancer Research Group propose two new classifications system of gastric cancer by using multi-platforms of molecular analyses. However, these highly complicated and cost technologies have not yet been translated into full clinical utility. In addition, the clinicians are expected to gain more guidance of treatment for different molecular subtypes. In this study, we developed a panel of gastric cancer patients in population from Southern China using commercially accessible TMA and immunohistochemical technology. A cohort of 259 GC patients was classified into 4 subtypes on the basis of expression of mismatch repair proteins (PMS2, MLH1, MSH2, and MSH6), E-cadherin and p21 protein. We observed that the subtypes presented distinct prognosis. dMMR-like subtype was associated with the best prognosis, and E-cadherin-a subtype was associated with the worst prognosis. Patients with p21-High and p21-Ligh subtypes had intermediate overall survival. In multivariate analysis, the dMMR-like subtype remained an independent prediction power for overall survival in the model. We described a molecular classification of gastric cancers using clinically applicable assay. The biological relevance of the four subtypes was illustrated by significant differences in prognosis. Our molecular classification provided an effective and inexpensive screening tool for improving prognostic models. Nevertheless, our study should be considered preliminary and carries a limited predictive value as a single-center retrospective study.

Small-Molecule and CRISPR Screening Converge to Reveal Receptor Tyrosine Kinase Dependencies in Pediatric Rhabdoid Tumors

Cancer is often seen as a disease of mutations and chromosomal abnormalities. However, some cancers, including pediatric rhabdoid tumors (RTs), lack recurrent alterations targetable by current drugs and need alternative, informed therapeutic options. To nominate potential targets, we performed a high-throughput small-molecule screen complemented by a genome-scale CRISPR-Cas9 gene-knockout screen in a large number of RT and control cell lines. These approaches converged to reveal several receptor tyrosine kinases (RTKs) as therapeutic targets, with RTK inhibition effective in suppressing RT cell growth in vitro and against a xenograft model in vivo. RT cell lines highly express and activate (phosphorylate) different RTKs, creating dependency without mutation or amplification. Downstream of RTK signaling, we identified PTPN11, encoding the pro-growth signaling protein SHP2, as a shared dependency across all RT cell lines. This study demonstrates that large-scale perturbational screening can uncover vulnerabilities in cancers with "quiet" genomes.

A dual MET/AXL small-molecule inhibitor exerts efficacy against gastric carcinoma through killing cancer cells as well as modulating tumor microenvironment

The receptor tyrosine kinases MET and AXL have been implicated in tumorigenesis and aggressiveness of multiple malignancies. We performed this study to evaluate the antitumor impact of LY2801653, a dual MET and AXL inhibitor on gastric cancer and to elucidate the underlying mechanisms. In the present study, tissue microarrays containing gastric cancer tissues were stained with MET and AXL antibodies, which showed the prognostic values of MET and AXL. Administration of LY2801653 inhibited cell proliferation, migration, epithelial‐mesenchymal transition, induced apoptosis, and cell cycle arrest. Xenograft mouse models showed suppressed cell proliferation of tumors in high MET and AXL expression cells. LY2801653 also inhibited the growth of MET and AXL‐independent cells at higher but clinically relevant doses through decreased angiogenesis and M2 macrophages in the tumor microenvironment. In conclusion, our study provides evidence for MET and AXL as prognostic biomarkers and potential therapeutic targets in gastric cancer. The dual MET/AXL inhibitor LY2801653 represents a promising therapeutic strategy for the treatment of patients with gastric carcinoma.

Tumour angiogenesis and c-Met pathway activation - implications in breast cancer

Breast cancer is a heterogeneous disease with wide range of clinical behaviour. Tumour angiogenesis and metastasis have been considered as prognostic markers of the breast carcinoma, and c-Met, a transmembrane receptor tyrosine kinase has been implicated in both these processes of tumour progression. This study was conducted to elucidate c-Met and downstream signalling pathways in breast cancer and correlate with angiogenesis as assessed by microvessel density (MVD) and other prognostic parameters including lymph node metastases. Microvessel density (MVD) was assessed by endothelial cell (CD34) marker in breast cancers. c-Met was evaluated by immunohistochemistry for protein expression and by copy number assay for amplification at gene level. PCR array for gene expression related to c-Met, RAS-MAPK, PI3K-AKT and angiogenesis pathway was performed by real-time PCR. c-Met protein, copy number and mRNA expression did not differ significantly with the lymph node status or MVD. However, Her-2 overexpressing group showed c-Met protein overexpression and amplification. c-Met protein overexpression was also noted in the Luminal B subtype though no amplification was noted. Thus, the c-Met immunohistochemistry score and the c-MET copy numbers did not correlate with each other. c-Met downstream pathway genes (RAS-MAPK, PI3K-AKT and angiogenesis pathway) showed significant upregulation in Luminal B molecular subtype, lymph node-positive cases and cases with high MVD. The downstream signalling pathways (angiogenesis, RAS-MAPK and PI3K-AKT) were associated high MVD, lymph node metastases, and Her-2 and Luminal B subtype. Since inhibitors of these pathways are commercially available, these can be of therapeutic significance.

HGF/MET pathway aberrations as diagnostic, prognostic, and predictive biomarkers in human cancers

Cancer is a major cause of death worldwide. MET tyrosine kinase receptor [MET, c-MET, hepatocyte growth factor (HGF) receptor] pathway activation is associated with the appearance of several hallmarks of cancer. The HGF/MET pathway has emerged as an important actionable target across many solid tumors; therefore, biomarker discovery becomes essential in order to guide clinical intervention and patient stratification with the aim of moving towards personalized medicine. The focus of this review is on how the aberrant activation of the HGF/MET pathway in tumor tissue or the circulation can provide diagnostic and prognostic biomarkers and predictive biomarkers of drug response. Many meta-analyses have shown that aberrant activation of the MET pathway in tumor tissue, including MET gene overexpression, gene amplification, exon 14 skipping and other activating mutations, is almost invariably associated with shorter survival and poor prognosis. Most meta-analyses have been performed in non-small cell lung cancer (NSCLC), breast, head and neck cancers as well as colorectal, gastric, pancreatic and other gastrointestinal cancers. Furthermore, several studies have shown the predictive value of MET biomarkers in the identification of patients who gain the most benefit from HGF/MET targeted therapies administered as single or combination therapies. The highest predictive values have been observed for response to foretinib and savolitinib in renal cancer, as well as tivantinib in NSCLC and colorectal cancer. However, some studies, especially those based on MET expression, have failed to show much value in these stratifications. This may be rooted in lack of standardization of methodologies, in particular in scoring systems applied in immunohistochemistry determinations or absence of oncogenic addiction of cancer cells to the MET pathway, despite detection of overexpression. Measurements of amplification and mutation aberrations are less likely to suffer from these pitfalls. Increased levels of MET soluble ectodomain (sMET) in circulation have also been associated with poor prognosis; however, the evidence is not as strong as it is with tissue-based biomarkers. As a diagnostic biomarker, sMET has shown its value in distinguishing cancer patients from healthy individuals in prostate and bladder cancers and in melanoma. On the other hand, increased circulating HGF has also been presented as a valuable prognostic and diagnostic biomarker in many cancers; however, there is controversy on the predictive value of HGF as a biomarker. Other biomarkers such as circulating tumor DNA (ctDNA) and tumor HGF levels have also been briefly covered. In conclusion, HGF/MET aberrations can provide valuable diagnostic, prognostic and predictive biomarkers and represent vital assets for personalized cancer therapy.

Crizotinib-resistant MET mutations in gastric cancer patients are sensitive to type II tyrosine kinase inhibitors

Aim: Crizotinib has been used to counter MET amplification in different human malignancies. However, transient responses were observed in some patients with rapid acquisition of resistant mutations in MET. Materials & methods: MET mutations stably expressed Ba/F3 cell lines were used for IC₅₀ detection. Signaling pathway analysis was done using 293T cell line. Results: Four MET mutations conferred resistance to crizotinib with sustained activation of downstream signaling pathways of MET. On the other hand, the four MET mutations displayed different response to type II tyrosine kinase inhibitors with variable deterioration of the downstream signals. Conclusion: This study suggested that patients carrying MET V1092L, D1228G or Y1230H mutations could benefit from type II tyrosine kinase inhibitor treatment, but not patients with G1163R or D1228Y/N mutations.

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.

Neutralizing antibody to FGFR2 can act as a selective biomarker and potential therapeutic agent for gastric cancer with FGFR2 amplification

Fibroblast growth factor receptor 2 (FGFR2) amplification has been reported in 5-10% of gastric cancer (GC) and is associated with poor prognosis. In this study, we characterized the anti-tumor effect of PRO-007, a newly developed recombinant monoclonal antibody that targets FGFR2, in GC cell lines KATO III (with FGFR2 amplification) and NCI-N87 (without FGFR2 amplification). Validation was performed in parallel using two patient-derived tumor cells (PDCs) from patients with GC. Cell viability assays were performed using FGFR2-transfected NCI-N87 cells and FGFR2-knockdown KATO III cells that were generated using short hairpin RNA (shRNA). PRO-007 reduced KATO III cell viability (P = 0.0034) but not that of NCI-N87 cells (P = 0.3710). PRO-007 also significantly reduced KATO III cell invasiveness (P < 0.0001) but not NCI-N87 cell invasiveness (P = 0.8136). Immunoblot analysis showed that PRO-007 treatment decreased the levels of phosphorylated AKT and ERK. The FGFR2-inhibitory activity of PRO-007 was confirmed in genetically modified GC cell lines. Cell viability of FGFR2-overexpressing NCI-N87 cells was significantly decreased by PRO-007, while KATO III cells were significantly resistant to the treatment when FGFR2 was knocked down by FGFR2 shRNA transfection. Furthermore, PRO-007 had a synergistic effect with ramucirumab on the invasiveness of cancer cells with FGFR2 amplification. Consistent results were obtained using PDCs from patients with GC. Overall, these preclinical data support the further clinical development of PRO-007 as a potential therapeutic agent for patients with FGFR2-amplified GC.

Targeting the Oncogenic FGF-FGFR Axis in Gastric Carcinogenesis

Gastric cancer (GC) is one of the most wide-spread malignancies in the world. The oncogenic role of signaling of fibroblast growing factors (FGFs) and their receptors (FGFRs) in gastric tumorigenesis has been gradually elucidated by recent studies. The expression pattern and clinical correlations of FGF and FGFR family members have been comprehensively delineated. Among them, FGF18 and FGFR2 demonstrate the most prominent driving role in gastric tumorigenesis with gene amplification or somatic mutations and serve as prognostic biomarkers. FGF-FGFR promotes tumor progression by crosstalking with multiple oncogenic pathways and this provides a rational therapeutic strategy by co-targeting the crosstalks to achieve synergistic effects. In this review, we comprehensively summarize the pathogenic mechanisms of FGF-FGFR signaling in gastric adenocarcinoma together with the current targeted strategies in aberrant FGF-FGFR activated GC cases.

Systematic Review of Patient-Derived Xenograft Models for Preclinical Studies of Anti-Cancer Drugs in Solid Tumors

Patient-derived xenograft (PDX) models are used as powerful tools for understanding cancer biology in PDX clinical trials and co-clinical trials. In this systematic review, we focus on PDX clinical trials or co-clinical trials for drug development in solid tumors and summarize the utility of PDX models in the development of anti-cancer drugs, as well as the challenges involved in this approach, following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Recently, the assessment of drug efficacy by PDX clinical and co-clinical trials has become an important method. PDX clinical trials can be used for the development of anti-cancer drugs before clinical trials, with their efficacy assessed by the modified response evaluation criteria in solid tumors (mRECIST). A few dozen cases of PDX models have completed enrollment, and the efficacy of the drugs is assessed by 1 × 1 × 1 or 3 × 1 × 1 approaches in the PDX clinical trials. Furthermore, co-clinical trials can be used for personalized care or precision medicine with the evaluation of a new drug or a novel combination. Several PDX models from patients in clinical trials have been used to assess the efficacy of individual drugs or drug combinations in co-clinical trials.

Establishment of a New Scirrhous Gastric Cancer Cell Line with FGFR2 Overexpression, OCUM-14

BACKGROUND

The prognosis of scirrhous gastric carcinoma (SGC), which is characterized by rapid infiltration and proliferation of cancer cells accompanied by extensive stromal fibrosis, is extremely poor. In this study, we report the establishment of a unique SGC cell line from a gastric cancer patient in whom an autopsy was performed.

METHODS

A new SGC cell line, OCUM-14, was established from malignant ascites of a male patient with SGC. A postmortem autopsy was performed on the patient. Characterization of OCUM-14 cells was analyzed by microscopic examination, reverse transcription polymerase chain reaction, fluorescence in situ hybridization analysis, immunohistochemical examination, CCK-8 assay, and in vivo assay.

RESULTS

OCUM-14 cells grew singly or in clusters, and were floating and round-shaped. Most OCUM-14 cells had many microvilli on their surfaces. The doubling time was 43.1 h, and the subcutaneous inoculation of 1.0 × 10⁷ OCUM-14 cells into mice resulted in 50% tumor formation. mRNA expressions of fibroblast growth factor receptor 2 (FGFR2) and human epidermal growth factor receptor 2 (HER2) were observed in OCUM-14 cells. FGFR2, but not HER2, overexpression was found in OCUM-14 cells. The heterogeneous overexpression of FGFR2 was also found in both the primary tumor and metastatic lesions of the peritoneum, lymph node, bone marrow, and lung of the patient. The FGFR2 inhibitors AZD4547 and BGJ398 significantly decreased the growth of OCUM-14 cells, while paclitaxel and 5-fluorouracil significantly decreased the proliferation of OCUM-14 cells, but cisplatin did not.

CONCLUSION

A new gastric cancer cell line, OCUM-14, was established from SGC and showed FGFR2 overexpression. OCUM-14 might be useful for elucidating the characteristic mechanisms of SGC and clarifying the effect of FGFR2 inhibitors on SGC.

Augmentation of Nab-Paclitaxel Chemotherapy Response by Mechanistically Diverse Antiangiogenic Agents in Preclinical Gastric Cancer Models

Gastric adenocarcinoma (GAC) remains the third most common cause of cancer-related deaths worldwide. Systemic chemotherapy is commonly recommended as a fundamental treatment for metastatic GAC; however, standard treatment has not been established yet. Angiogenesis plays a crucial role in the progression and metastasis of GAC. We evaluated therapeutic benefits of mechanistically diverse antiangiogenic agents in combination with nab-paclitaxel, a next-generation taxane, in preclinical models of GAC. Murine survival studies were performed in peritoneal dissemination models, whereas tumor growth studies were performed in subcutaneous GAC cell-derived or patient-derived xenografts. The mechanistic evaluation involved IHC and Immunoblot analysis in tumor samples. Nab-paclitaxel increased animal survival that was further improved by the addition of antiangiogenic agents ramucirumab (or its murine version DC101), cabozantinib and nintedanib. Nab-paclitaxel combination with nintedanib was most effective in improving animal survival, always greater than 300% over control. In cell-derived subcutaneous xenografts, nab-paclitaxel reduced tumor growth while all three antiangiogenic agents enhanced this effect, with nintedanib demonstrating the greatest inhibition. Furthermore, in GAC patient-derived xenografts the combination of nab-paclitaxel and nintedanib reduced tumor growth over single agents alone. Tumor tissue analysis revealed that ramucirumab and cabozantinib only reduced tumor vasculature, whereas nintedanib in addition significantly reduced tumor cell proliferation and increased apoptosis. Effects of nab-paclitaxel, a promising chemotherapeutic agent for GAC, can be enhanced by new-generation antiangiogenic agents, especially nintedanib. The data suggest that nab-paclitaxel combinations with multitargeted antiangiogenic agents carry promising potential for improving clinical GAC therapy. Mol Cancer Ther; 17(11); 2353-64. ©2018 AACR.

The significance of scirrhous gastric cancer cell lines: the molecular characterization using cell lines and mouse models

Scirrhous gastric cancer (SGC) exhibits aggressiveness of the rapid infiltrating tumor cells with abundant fibroblasts. Experimental studies using SGC cell lines have obtained useful information about this cancer. Our literature search divulged a total of 18 SGC cell lines; two cell lines were established from primary SGC and the other lines were established from a metastatic lesion of SGC. Fibroblast growth factor receptor 2 (FGFR2) and transforming growth factor-beta receptor (TβR) are linked to the rapid development of SGC. Cross-talk between the cancer cells and cancer-associated fibroblasts (CAFs) has been shown to contribute to the progression of SGC. Chemokine (C-X-C motif) receptor 1 (CXCR1) from SGC cells might be associated with the abundant CAFs in cancer microenvironments. The in vivo models established using SGC cell lines are expected to serve as a useful tool for the development of drugs such as FGFR2 inhibitors, TβR inhibitors, and CXCR1 inhibitors, which might be promising as SGC treatments. However, the number of available SGC cell lines is insufficient for the clarification of the entire biologic behavior of SGC. Since the mechanisms responsible for the characteristic aggressiveness of SGC are not fully elucidated, the establishment of new SGC cell lines could help clarify the biological behavior of SGC and contribute to its treatment.

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.

E-Cadherin/ROS1 Inhibitor Synthetic Lethality in Breast Cancer

The cell adhesion glycoprotein E-cadherin (CDH1) is commonly inactivated in breast tumors. Precision medicine approaches that exploit this characteristic are not available. Using perturbation screens in breast tumor cells with CRISPR/Cas9-engineered CDH1 mutations, we identified synthetic lethality between E-cadherin deficiency and inhibition of the tyrosine kinase ROS1. Data from large-scale genetic screens in molecularly diverse breast tumor cell lines established that the E-cadherin/ROS1 synthetic lethality was not only robust in the face of considerable molecular heterogeneity but was also elicited with clinical ROS1 inhibitors, including foretinib and crizotinib. ROS1 inhibitors induced mitotic abnormalities and multinucleation in E-cadherin-defective cells, phenotypes associated with a defect in cytokinesis and aberrant p120 catenin phosphorylation and localization. In vivo, ROS1 inhibitors produced profound antitumor effects in multiple models of E-cadherin-defective breast cancer. These data therefore provide the preclinical rationale for assessing ROS1 inhibitors, such as the licensed drug crizotinib, in appropriately stratified patients.Significance: E-cadherin defects are common in breast cancer but are currently not targeted with a precision medicine approach. Our preclinical data indicate that licensed ROS1 inhibitors, including crizotinib, should be repurposed to target E-cadherin-defective breast cancers, thus providing the rationale for the assessment of these agents in molecularly stratified phase II clinical trials. Cancer Discov; 8(4); 498-515. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 371.

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.

The multiple paths towards MET receptor addiction in cancer

Targeted therapies against receptor tyrosine kinases (RTKs) are currently used with success on a small proportion of patients displaying clear oncogene activation. Lung cancers with a mutated EGFR provide a good illustration. The efficacy of targeted treatments relies on oncogene addiction, a situation in which the growth or survival of the cancer cells depends on a single deregulated oncogene. MET, a member of the RTK family, is a promising target because it displays many deregulations in a broad panel of cancers. Although clinical trials having evaluated MET inhibitors in large populations have yielded disappointing results, many recent case reports suggest that MET inhibition may be effective in a subset of patients with unambiguous MET activation and thus, most probably, oncogene addiction. Interestingly, preclinical studies have revealed a particularity of MET addiction: it can arise through several mechanisms, and the mechanism involved can differ according to the cancer type. The present review describes the different mechanisms of MET addiction and their consequences for diagnosis and therapeutic strategies. Although in each cancer type MET addiction affects a restricted number of patients, pooling of these patients across all cancer types yields a targetable population liable to benefit from addiction-targeting therapies.

Synergistic antitumor effects of cMet inhibitor in combination with anti-VEGF in colorectal cancer patient-derived xenograft models

cMet signaling pathway is involved in the resistance to anti-VEGF therapy and cMet overexpression is associated with tumor progression and poor prognosis. In this study, the expression of cMet in 146 Chinese colorectal cancer (CRC) patients was examined by immunohistochemistry staining. Our data demonstrated that cMet overexpression rate was 42.5% (62/146) and cMet overexpression was closely correlated with distant metastasis of CRC. Using CRC patient-derived xenograft (PDX) mouse models we investigated antitumor activity of a novel selective cMet inhibitor volitinib alone or in combination with anti-VEGF inhibitor apatinib in vivo. Our results showed that combination treatment significantly inhibited tumor growth in two PDX models. While volitinib treatment alone induced moderate improvement in tumor growth inhibition, combination treatment synergistically reduced microvessel density, suppressed proliferation, and increased apoptosis in PDX models. Further analysis showed synergistic inhibition of MAPK and PI3K/Akt pathways by volitinib and apatinib. Taken together, our data provide a rationale to targeting both cMet and VEGF in the treatment of cMet overexpressing CRC in clinical trials.

Effects of trastuzumab and afatinib on kinase activity in gastric cancer cell lines

The molecular mechanism of action of the HER2‐targeted antibody trastuzumab is only partially understood, and the direct effects of trastuzumab on the gastric cancer signaling network are unknown. In this study, we compared the molecular effect of trastuzumab and the HER kinase inhibitor afatinib on the receptor tyrosine kinase (RTK) network and the downstream‐acting intracellular kinases in gastric cancer cell lines. The molecular effects of trastuzumab and afatinib on the phosphorylation of 49 RTKs and 43 intracellular kinase phosphorylation sites were investigated in three gastric cancer cell lines (NCI‐N87, MKN1, and MKN7) using proteome profiling. To evaluate these effects, data were analyzed using mixed models and clustering. Moreover, proliferation assays were performed. Our comprehensive quantitative analysis of kinase activity in gastric cancer cell lines indicates that trastuzumab and afatinib selectively influenced the HER family RTKs. The effects of trastuzumab differed between cell lines, depending on the presence of activated HER2. The effects of trastuzumab monotherapy were not transduced to the intracellular kinase network. Afatinib alone or in combination with trastuzumab influenced HER kinases in all cell lines; that is, the effects of monotherapy and combination therapy were transduced to the intracellular kinase network. These results were confirmed by proliferation analysis. Additionally, the MET‐amplified cell line Hs746T was identified as afatinib nonresponder. The dependence of the effect of trastuzumab on the presence of activated HER2 might explain the clinical nonresponse of some patients who are routinely tested for HER2 expression and gene amplification in the clinic but not for HER2 activation. The consistent effects of afatinib on HER RTKs and downstream kinase activation suggest that afatinib might be an effective candidate in the future treatment of patients with gastric cancer irrespective of the presence of activated HER2. However, MET amplification should be taken into account as potential resistance factor.

Circulating tumor DNA profiling by next generation sequencing reveals heterogeneity of crizotinib resistance mechanisms in a gastric cancer patient with MET amplification

Crizotinib has been used to counter MET gene amplification in a number of different human malignancies. Transient response to crizotinib in MET-amplified gastric cancer has been reported, but the mechanisms of resistance are not well studied. Here, we reported a stage IV gastric cancer patient with high levels of MET amplification. The implementation of crizotinib treatment led to significant symptomatic improvement in the first 2 months, but was followed by rapid disease progression. Periodic mutation profiling of patient's circulating tumor DNA (ctDNA) by next generation sequencing (NGS) revealed a number of genetic alterations including re-occurrence of MET amplification, multiple secondary MET mutations, a dramatic increase of FGFR2 gene relative copy number as well as mutations in other downstream and bypassing elements, which may collectively related to the patient's cancer progression. Our results illustrate the complex and heterogeneous molecular mechanisms for crizotinib resistance in this patient, and demonstrate the great potential of ctDNA profiling for treatment decision-making and prognosis in clinical practice.

Prognostic impact of fibroblast growth factor receptor 2 gene amplification in patients receiving fluoropyrimidine and platinum chemotherapy for metastatic and locally advanced unresectable gastric cancers

Although Fibroblast growth factor receptor (FGFR) 2 gene amplification and its prognostic significance have been reported in resectable gastric cancers, information on these features remains limited in the metastatic setting. The presence of FGFR2 amplification was assessed in formalin-fixed, paraffin-embedded tissues using a quantitative PCR-based gene copy number assay with advanced gastric cancer cohorts. A total of 327 patients with tumor portion of ≥70% were analyzed for clinical features. Among these patients, 260 who received first-line fluoropyrimidine and platinum chemotherapy were analyzed for survival.Sixteen of 327 patients (4.9%) exhibited FGFR2 amplification. The amplification group showed associations with age <65 years, Borrmann type 4 disease, poor performance status, poorly differentiated histology, extra-abdominal lymph node metastases, and bone metastases. The median overall survival (OS) and progression-free survival (PFS) were found to be 12.7 and 5.8 months, respectively. In univariate analysis, PFS did not differ between amplification and no amplification groups (hazard ratio [HR]=1.34, 95% confidence interval [CI]: 0.78-2.31, p=0.290), although the OS was significantly shorter in the amplification group (HR=1.92, 95% CI: 1.13-3.26, p=0.015). However, multivariate analysis indicated that FGFR2 amplification was not an independent prognostic factor for OS (HR=1.42, 95% CI: 0.77-2.61, p=0.261).Although FGFR2 amplification is associated with poorer OS, it does not appear to be an independent prognostic predictor in patients with advanced gastric cancer treated with palliative fluoropyrimidine and platinum chemotherapy.

Receptor tyrosine kinase amplified gastric cancer: Clinicopathologic characteristics and proposed screening algorithm

Although targeted therapy for receptor tyrosine kinases (RTKs) of advanced gastric cancers (AGCs) has been in the spotlight, guidelines for the identification of RTK-amplified gastric cancers (RA-GCs) have not been established. In this study, we investigate clinicopathologic characteristics of RA-GCs and propose a screening algorithm for their identification. We performed immunohistochemistry (IHC) for MLH1, MSH2, PMS2, MSH6, key RTKs (EGFR, HER2, MET), and p53, in situ hybridization for Epstein-Barr virus encoding RNA, and silver in situ hybridization (SISH) for EGFR, HER2, and MET using tissue microarrays of 993 AGCs. On IHC, 157 (15.8%) 61, (6.15%), and 85 (8.56%) out of 993 cases scored 2+ or 3+ for EGFR, HER2, and MET, respectively. On SISH, 31.2% (49/157), 80.3% (49/61), and 30.6% (26/85) of 2+ or 3+ cases on IHC showed amplification of the corresponding genes. Of the 993 cases, 104 were classified as RA-GCs. RA-GC status correlated with older age (P < 0.001), differentiated histology (P = 0.001), intestinal or mixed type by Lauren classification (P < 0.001), lymphovascular invasion (P = 0.026), and mutant-pattern of p53 (P < 0.001). The cases were divided into four subgroups using two classification systems, putative molecular classification and histologic-molecular classification, based on Lauren classification, IHC, and SISH results. The histologic-molecular classification showed higher sensitivity for identification of RA-GCs and predicted patient prognosis better than the putative molecular classification. In conclusion, RA-GCs show unique clinicopathologic features. The proposed algorithm based on histologic-molecular classification can be applied to select candidates for genetic examination and targeted therapy.

Tailor-Making Fluorescent Hyaluronic Acid Microgels via Combining Microfluidics and Photoclick Chemistry for Sustained and Localized Delivery of Herceptin in Tumors

Antibody therapeutics, though representing a most used biomedicine, suffers from poor in vivo stability, rapid degradation, and frequent injections. Here, we report that fluorescent hyaluronic acid microgels (HMGs) tailor-made by combining microfluidics and "tetrazole-alkene" photoclick chemistry enable sustained and localized delivery of Herceptin in ovarian tumors. HMGs were obtained with a defined size (25-50 μm), narrow size distribution, high stability, and strong green fluorescence. Notably, HMGs exhibited a remarkably high loading of proteins such as Herceptin and IgG with a loading efficiency exceeding 90% at a theoretical protein-loading content of 30 wt %. In vitro protein release experiments revealed a sustained and hyaluronidase (HAase)-dependent release of Herceptin from HMGs, in which 80.6% of Herceptin was released at 1 U/mL HAase in 10 days. The released Herceptin maintained its secondary structure and antitumor activity. In vivo imaging results demonstrated obviously better tumoral retention for Cy5-labeled Herceptin-loaded HMGs following subcutaneous (sc) injection than for the free-protein counterpart. Interestingly, sc injection of the Herceptin-loaded HMGs into SKOV-3 human ovarian tumor-bearing nude mice at a dose of 30 mg Herceptin equiv/kg induced nearly complete tumor suppression, which was significantly more effective than the sc or systemic injection of free Herceptin. These tailor-made fluorescent HMGs appeared as a robust injectable platform for sustained and localized delivery of therapeutic proteins.

Prognostic significance of Daxx NCR (Nuclear/Cytoplasmic Ratio) in gastric cancer

In addition to regulating apoptosis via its interaction with the death domain of Fas receptor, death domain associated protein 6 (Daxx) is also known to be involved in transcriptional regulation, suggesting that the function of Daxx depends on its subcellular localization. In this study, we aimed to explore Daxx subcellular localization in gastric cancer (GC) cells and correlate the findings with clinical data in GC patients. Seventy pairs of tissue samples (GC and adjacent normal tissue) were analyzed immunohistochemically for Daxx expression and localization (nuclear and cytoplasmic). The Daxx Nuclear/Cytoplasmic ratio (Daxx NCR) values in tissue microarray data with 522 tumor samples were further analyzed. The defined Prior cohort (n = 277, treatment between 2006 and 2009) and Recent cohort (n = 245, treatment between 2010 and 2011) were then used to examine the relationship between Daxx NCR and clinical data. The Daxx NCR was found to be clinically informative and significantly higher in GC tissue. Using Daxx NCR (risk ratio = 2.0), both the Prior and Recent cohorts were divided into high‐ and low‐risk groups. Relative to the low‐risk group, the high‐risk patients had a shorter disease free survival (DFS) and overall survival (OS) in both cohorts. Importantly, postoperative chemotherapy was found having differential effect on high‐ and low‐risk patients. Such chemotherapy brought no survival benefit, (and could potentially be detrimental,) to high‐risk patients after surgery. Daxx NCR could be used as a prognosis factor in GC patients, and may help select the appropriate population to benefit from chemotherapy after surgery.

Profiling cancer-associated genetic alterations and molecular classification of cancer in Korean gastric cancer patients

Recently, the Cancer Genome Atlas (TCGA) Research Network and Asian Cancer Research Group provided a new classification of gastric cancer (GC) to aid the development of biomarkers for targeted therapy and predict prognosis. We studied associations between genetically aberrant profiles of cancer-related genes, environmental factors, and histopathological features in 107 paired gastric tumor-non-tumor tissue GC samples. 6.5% of our GC cases were classified as the EBV subtype, 17.8% as the MSI subtype, 43.0% as the CIN subtype, and 32.7% as the GS subtype. The distribution of four GC subgroups based on the TCGA and our dataset were similar. The MSI subtype showed a hyper-mutated status and the best prognosis among molecular subtype. However, molecular classification based on the four GC subtypes showed no significant survival differences in terms of overall survival (p= 0.548) or relapse-free survival (RFS, p=0.518). The P619fs*43 in ZBTB20 was limited to MSI group (n= 5/19, 26.3%), showing similar trends observed in TCGA dataset.

Genetic alterations of the RTK/RAS/MAPK and PI3K/AKT/mTOR pathways were detected in 34.6% of GC cases (37 individual cases). We also found two cases with likely pathogenic variants (NM_004360.4: c. 2494 G>A, p.V832M) in the CDH1 gene.

Here, we classified molecular subtypes of GC according to the TCGA system and provide a critical starting point for the design of more appropriate clinical trials based on a comprehensive analysis of genetic alterations in Korean GC patients.

The Therapeutic Potential of Targeting the HGF/cMET Axis in Ovarian Cancer

Survival rates for ovarian cancer have remained relatively stable for the past 2 decades despite advances in surgical techniques and cytotoxic chemotherapeutics, indicating a requirement for better therapies. One pathway currently proposed for targeting is the HGF/cMET pathway. Upregulated in a number of tumour types, cMET is a tyrosine kinase receptor expressed on epithelial cells. In ovarian cancer, it has been identified as highly expressed in the four major subtypes, with expression estimates ranging from 11 to 68 % of cases. HGF, the only known ligand for cMET, is found at high levels in both serum and ascites in women with ovarian cancer, and is proposed to induce both migration and metastasis. However, clinically validated biomarkers are not yet available for either HGF or cMET, preventing a clear understanding of the true rate of overexpression, or its correlation with prognosis. Despite this, a number of agents against HGF and cMET are currently being investigated in clinical trials for multiple tumour types, including ovarian. However, a lack of patient selection, biomarker usage, and post hoc analysis correlating response with expression has resulted in the majority of these trials showing little beneficial effect from these agents, indicating that additional research is required to determine their usefulness in patients with ovarian cancer.