K-sam, an amplified gene in stomach cancer, is a member of the heparin-binding growth factor receptor genes

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.

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.

Preclinical characterization of bemarituzumab, an anti-FGFR2b antibody for the treatment of cancer

Bemarituzumab (FPA144) is a first-in-class, humanized, afucosylated immunoglobulin G1 monoclonal antibody (mAb) directed against fibroblast growth factor receptor 2b (FGFR2b) with two mechanisms of action against FGFR2b-overexpressing tumors: inhibition of FGFR2b signaling and enhanced antibody-dependent cell-mediated cytotoxicity (ADCC). Bemarituzumab is being developed as a cancer therapeutic, and we summarize here the key nonclinical data that supported moving it into clinical trials. Bemarituzumab displayed sub-nanomolar cross-species affinity for FGFR2b receptors, with >20-fold enhanced binding affinity to human Fc gamma receptor IIIa compared with the fucosylated version. In vitro, bemarituzumab induced potent ADCC against FGFR2b-expressing tumor cells, and inhibited FGFR2 phosphorylation and proliferation of SNU-16 gastric cancer cells in a concentration-dependent manner. In vivo, bemarituzumab inhibited tumor growth through inhibition of the FGFR2b pathway and/or ADCC in mouse models. Bemarituzumab demonstrated enhanced anti-tumor activity in combination with chemotherapy, and due to bemarituzumab-induced natural killer cell-dependent increase in programmed death-ligand 1, also resulted in enhanced anti-tumor activity when combined with an anti-programmed death-1 antibody. Repeat-dose toxicity studies established the highest non-severely-toxic dose at 1 and 100 mg/kg in rats and cynomolgus monkeys, respectively. In pharmacokinetic (PK) studies, bemarituzumab exposure increase was greater than dose-proportional, with the linear clearance in the expected dose range for a mAb. The PK data in cynomolgus monkeys were used to project bemarituzumab linear PK in humans, which were consistent with the observed human Phase 1 data. These key nonclinical studies facilitated the successful advancement of bemarituzumab into the clinic.

SHP2 as a Potential Therapeutic Target in Diffuse-Type Gastric Carcinoma Addicted to Receptor Tyrosine Kinase Signaling

Simple Summary

Diffuse-type gastric carcinoma (DGC) is characterized by rapid infiltrative growth associated with massive stroma and frequent peritoneal dissemination, which leads to poor patient outcomes. In this study, we found that the oncogenic tyrosine phosphatase SHP2 is tyrosine-phosphorylated downstream of the amplified receptor tyrosine kinases (RTKs) Met and fibroblast growth factor receptor 2 (FGFR2) in DGC cell lines. SHP2 knockdown or pharmacological inhibition selectively suppressed the growth of DGC addicted to amplified Met and FGFR2. Moreover, targeting SHP2 abrogated malignant phenotypes, including peritoneal dissemination, of Met-addicted DGC and could overcome acquired resistance to Met inhibitors. Our findings suggest that SHP2 is a potential target for the treatment of DGC addicted to amplified RTK signaling.

Abstract

Diffuse-type gastric carcinoma (DGC) exhibits aggressive progression associated with rapid infiltrative growth, massive fibrosis, and peritoneal dissemination. Gene amplification of Met and fibroblast growth factor receptor 2 (FGFR2) receptor tyrosine kinases (RTKs) has been observed in DGC. However, the signaling pathways that promote DGC progression downstream of these RTKs remain to be fully elucidated. We previously identified an oncogenic tyrosine phosphatase, SHP2, using phospho-proteomic analysis of DGC cells with Met gene amplification. In this study, we characterized SHP2 in the progression of DGC and assessed the therapeutic potential of targeting SHP2. Although SHP2 was expressed in all gastric carcinoma cell lines examined, its tyrosine phosphorylation preferentially occurred in several DGC cell lines with Met or FGFR2 gene amplification. Met or FGFR inhibitor treatment or knockdown markedly reduced SHP2 tyrosine phosphorylation. Knockdown or pharmacological inhibition of SHP2 selectively suppressed the growth of DGC cells addicted to Met or FGFR2, even when they acquired resistance to Met inhibitors. Moreover, SHP2 knockdown or pharmacological inhibition blocked the migration and invasion of Met-addicted DGC cells in vitro and their peritoneal dissemination in a mouse xenograft model. These results indicate that SHP2 is a critical regulator of the malignant progression of RTK-addicted DGC and may be a therapeutic target.

Fibroblast Growth Factor Receptors (FGFRs) and Noncanonical Partners in Cancer Signaling

Increasing evidence indicates that success of targeted therapies in the treatment of cancer is context-dependent and is influenced by a complex crosstalk between signaling pathways and between cell types in the tumor. The Fibroblast Growth Factor (FGF)/FGF receptor (FGFR) signaling axis highlights the importance of such context-dependent signaling in cancer. Aberrant FGFR signaling has been characterized in almost all cancer types, most commonly non-small cell lung cancer (NSCLC), breast cancer, glioblastoma, prostate cancer and gastrointestinal cancer. This occurs primarily through amplification and over-expression of FGFR1 and FGFR2 resulting in ligand-independent activation. Mutations and translocations of FGFR1-4 are also identified in cancer. Canonical FGF-FGFR signaling is tightly regulated by ligand-receptor combinations as well as direct interactions with the FGFR coreceptors heparan sulfate proteoglycans (HSPGs) and Klotho. Noncanonical FGFR signaling partners have been implicated in differential regulation of FGFR signaling. FGFR directly interacts with cell adhesion molecules (CAMs) and extracellular matrix (ECM) proteins, contributing to invasive and migratory properties of cancer cells, whereas interactions with other receptor tyrosine kinases (RTKs) regulate angiogenic, resistance to therapy, and metastatic potential of cancer cells. The diversity in FGFR signaling partners supports a role for FGFR signaling in cancer, independent of genetic aberration.

What Are the Potential Roles of Nuclear Perlecan and Other Heparan Sulphate Proteoglycans in the Normal and Malignant Phenotype

The recent discovery of nuclear and perinuclear perlecan in annulus fibrosus and nucleus pulposus cells and its known matrix stabilizing properties in tissues introduces the possibility that perlecan may also have intracellular stabilizing or regulatory roles through interactions with nuclear envelope or cytoskeletal proteins or roles in nucleosomal-chromatin organization that may regulate transcriptional factors and modulate gene expression. The nucleus is a mechano-sensor organelle, and sophisticated dynamic mechanoresponsive cytoskeletal and nuclear envelope components support and protect the nucleus, allowing it to perceive and respond to mechano-stimulation. This review speculates on the potential roles of perlecan in the nucleus based on what is already known about nuclear heparan sulphate proteoglycans. Perlecan is frequently found in the nuclei of tumour cells; however, its specific role in these diseased tissues is largely unknown. The aim of this review is to highlight probable roles for this intriguing interactive regulatory proteoglycan in the nucleus of normal and malignant cell types.

PLEKHA5 regulates the survival and peritoneal dissemination of diffuse-type gastric carcinoma cells with Met gene amplification

Met gene amplification has been found in a subset of malignant carcinomas, including diffuse-type gastric carcinoma (DGC), which has a poor prognosis owing to rapid infiltrative invasion and frequent peritoneal dissemination. Met is considered a promising therapeutic target for DGC. However, DGC cells with Met gene amplification eventually acquire resistance to Met inhibitors. Therefore, identification of alternate targets that mediate Met signaling and confer malignant phenotypes is critical. In this study, we conducted a phosphoproteomic analysis of DGC cells possessing Met gene amplification and identified Pleckstrin Homology Domain Containing A5 (PLEKHA5) as a protein that is tyrosine-phosphorylated downstream of Met. Knockdown of PLEKHA5 selectively suppressed the growth of DGC cells with Met gene amplification by inducing apoptosis, even though they had acquired resistance to Met inhibitors. Moreover, PLEKHA5 silencing abrogated the malignant phenotypes of Met-addicted DGC cells, including peritoneal dissemination in vivo. Mechanistically, PLEKHA5 knockdown dysregulates glycolytic metabolism, leading to activation of the JNK pathway that promotes apoptosis. These results indicate that PLEKHA5 is a novel downstream effector of amplified Met and is required for the malignant progression of Met-addicted DGC.

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.

Crosstalk Between Cancer Associated Fibroblasts and Cancer Cells in Scirrhous Type Gastric Cancer

Gastric cancer (GC) is the third leading cause among all cancer deaths globally. Although the treatment outcome of GC has improved, the survival of patients with GC at stages III and IV remains unsatisfactory. Among several types of GC, scirrhous type GC (SGC) shows highly aggressive growth and invasive activity, leading to frequent peritoneal metastasis. SGC is well known to accompany abundant stromal cells that compose the tumor microenvironment (TME) along with the produced extracellular matrix (ECM) and secreted factors. One of the main stromal components is cancer associated fibroblast (CAF). In the SGC microenvironment, CAFs are a source of various secreted factors, including fibroblast growth factors (FGFs), which mediate prominent tumor-stimulating activity. In turn, cancer cells also secrete numerous factors, which can activate and educate CAFs. Current findings suggest that cancer cells and stromal cells communicate interactively via the soluble factors, the ECM, and likely also by exosomes. In this review, we focus on the soluble factors mediating communication between cancer cells and CAFs in SGC, and consider how they are related to the modulation of TME and the high rate of peritoneal metastasis. At last, we discuss the perspectives on targeting these communication pathways for improved future treatment.

Application of "Tissueoid Cell Culture System" Using a Silicate Fiber Scaffold for Cancer Research

BACKGROUND

We developed a 3-dimensional (3D) culture system using a high-purity silica fiber scaffold of unwoven sheets called CellbedTM.

METHODS

We used adherent colon and esophagogastric junction adenocarcinoma cells, tongue squamous cell carcinoma (SqCC) cells, and nonadherent gastric cancer cells. These cells were subjected to staining with various substances and observed by electron microscopy. To evaluate the effects of extracellular matrix in carcinoma tissues, SqCC cells were cultured in Cellbed coated with collagens I, III, and IV.

RESULTS

Especially well-differentiated carcinoma cells cultured in this 3D system showed their own unique characteristics: luminal formation in adenocarcinoma cells and cell stratification and keratinization in SqCC cells. Scanning electron microscopy revealed the proliferation of cancer cells with cytoplasm entwined in Cellbed. Intercellular desmosomes in squamous epithelia were detected by transmission electron microscopy of vertical cross sections. SqCC cells cultured in Cellbed coated with collagen IV showed enhanced invasive and proliferative abilities.

CONCLUSION

Because the morphology of cancer cells cultured in this 3D culture system is similar to that in living organisms, we called the system a "tissueoid cell culture system." Coating with collagen IV enables the modification of cell-matrix interactions as well as recapitulation of the in vivo microenvironment.

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.

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.

Diffuse Gastric Cancer: A Summary of Analogous Contributing Factors for Its Molecular Pathogenicity

Gastric cancer is the third leading cause of cancer-related deaths and ranks as the fifth most common cancer worldwide. Incidence and mortality differ depending on the geographical region and gastric cancer ranks first in East Asian countries. Although genetic factors, gastric environment, and Helicobacter pylori infection have been associated with the pathogenicity and development of intestinal-type gastric cancer that follows the Correa’s cascade, the pathogenicity of diffuse-type gastric cancer remains mostly unknown and undefined. However, genetic abnormalities in the cell adherence factors, such as E-cadherin and cellular activities that cause impaired cell integrity and physiology, have been documented as contributing factors. In recent years, H. pylori infection has been also associated with the development of diffuse-type gastric cancer. Therefore, in this report, we discuss the host factors as well as the bacterial factors that have been reported as associated factors contributing to the development of diffuse-type gastric cancer.

Generation of high-affinity, internalizing anti-FGFR2 single-chain variable antibody fragment fused with Fc for targeting gastrointestinal cancers

Fibroblast growth factor receptors (FGFRs) are promising targets for antibody-based cancer therapies, as their substantial overexpression has been found in various tumor cells. Aberrant activation of FGF receptor 2 (FGFR2) signaling through overexpression of FGFR2 and/or its ligands, mutations, or receptor amplification has been reported in multiple cancer types, including gastric, colorectal, endometrial, ovarian, breast and lung cancer. In this paper, we describe application of the phage display technology to produce a panel of high affinity single chain variable antibody fragments (scFvs) against the extracellular ligand-binding domain of FGFR2 (ECD_FGFR2). The binders were selected from the human single chain variable fragment scFv phage display libraries Tomlinson I + J and showed high specificity and binding affinity towards human FGFR2 with nanomolar K_D values. To improve the affinity of the best binder selected, scFvF7, we reformatted it to a bivalent diabody format, or fused it with the Fc region (scFvF7-Fc). The scFvF7-Fc antibody construct presented the highest affinity for FGFR2, with a K_D of 0.76 nM, and was selectively internalized into cancer cells overexpressing FGFR2, Snu-16 and NCI-H716. Finally, we prepared a conjugate of scFvF7-Fc with the cytotoxic drug monomethyl-auristatin E (MMAE) and evaluated its cytotoxicity. The conjugate delivered MMAE selectively to FGFR2-positive tumor cells. These results indicate that scFvF7-Fc-vcMMAE is a highly potent molecule for the treatment of cancers with FGFR2 overexpression.

Prognostic relevance of FGFR2 expression in stage II/III gastric cancer with curative resection and S-1 chemotherapy

Curative gastrectomy and adjuvant chemotherapy using S-1 is a standard treatment for stage II/III gastric cancer in Japan. The purpose of the present study was to evaluate the prognostic relevance of fibroblast growth factor receptor (FGFR)2 expression in patients with stage II/III gastric cancer that underwent postoperative adjuvant chemotherapy with S-1. Formalin-fixed paraffin-embedded surgical specimens were retrospectively examined in 167 patients with stage II/III gastric cancer that underwent curative gastrectomy followed by adjuvant S1 chemotherapy. FGFR2 expression was measured using immunohistochemistry (IHC) staining. The IHC results for FGFR2 were as follows: Grade 1+, 32; grade 2+, 80; grade 3+, 55 patients. The FGFR2 expression level was not significantly associated with relapse-free or overall survival rates. However, in the diffuse type, the FGFR2 expression level tended to be negatively correlated with relapse-free survival. In particular, the proportion of patients who recurred >5 years following surgery was significantly larger in the FGFR2 grade 3+ group than in the grade 1+, 2+ group (4/22 vs. 1/35; P=0.047). The recurrent sites of long-term failure were mostly peritoneum among the diffuse type. To the best of our knowledge, the present study indicated for the first time that FGFR2 could predict long-term failure of adjuvant S-1 chemotherapy in curative advanced gastric cancer. There was no interaction between FGFR2 expression and patient survival outcomes in stage II/III gastric cancer. Patients with FGFR2 3+ in stage II/III gastric cancer should carefully be followed-up for >5 years after surgery.

IKKε and TBK1 expression in gastric cancer

Inhibitor of kappa B kinase epsilon (IKKε) and TANK-binding kinase 1 (TBK1) are non-canonical IKKs. IKKε and TBK1 share the kinase domain and are similar in their ability to activate the nuclear factor-kappa B signaling pathway. IKKε and TBK1 are overexpressed through multiple mechanisms in various human cancers. However, the expression of IKKε and TBK1 in gastric cancer and their role in prognosis have not been studied.

To investigate overexpression of the IKKε and TBK1 proteins in gastric cancer and their relationship with clinicopathologic factors, we performed immunohistochemical staining using a tissue microarray. Tissue microarray samples were obtained from 1,107 gastric cancer patients who underwent R0 gastrectomy with extensive lymph node dissection and adjuvant chemotherapy.

We identified expression of IKKε in 150 (13.6%) and TBK1 in 38 (3.4%) gastric cancers. Furthermore, co-expression of IKKε and TBK1 was identified in 1.5% of cases. Co-expression of IKKε and TBK1 was associated with differentiated intestinal histology and earlier T stage. In a multivariate binary logistic regression model, intestinal histologic type by Lauren classification and early AJCC stage were significant predictors for expression of IKKε and TBK1 proteins in gastric cancer. Changes in IKKε and TBK1 expression may be involved in the development of intestinal-type gastric cancer. The overexpression of IKKε and TBK1 should be considered in selected patients with intestinal-type gastric cancer.

In conclusion, this is the first large-scale study investigating the relationships between expression of IKKε and TBK1 and clinicopathologic features of gastric cancer. The role of IKKε and TBK1 in intestinal-type gastric cancer pathogenesis should be elucidated by further investigation.

Different clinical significance of FGFR1-4 expression between diffuse-type and intestinal-type gastric cancer

Background

Receptor tyrosine kinases promote tumor progression in many cancers, although oncologic activation differs between diffuse-type gastric cancer (DGC) and intestinal-type gastric cancer (IGC). Fibroblast growth factor receptor (FGFR) is one RTK, and we previously reported the clinical significance of FGFR1, 2, 3, and 4 in gastric cancer. The aim of the present study was to reevaluate the clinical significance of FGFR1–4 expression separately in DGC and IGC.

Methods

Tumor samples, including 109 DGCs and 100 IGCs, were obtained from patients who underwent gastrectomy between 2003 and 2007 in our institution. The expression levels of FGFR1, 2, 3, and 4 were measured in the tumors by immunohistochemical analysis.

Results

In DGC, high expression of FGFR1, FGFR2, or FGFR4 was significantly associated with the depth of invasion, lymph-node metastasis, pathological stage, and distant metastasis or recurrent disease. Patients with high expression of FGFR1, FGFR2, or FGFR4 had significantly poorer disease-specific survival (DSS) (p = 0.009, p = 0.001, and p = 0.023, respectively). In IGC, only FGFR4 expression was significantly associated with factors relative to tumor progression and with shorter DSS (p = 0.012).

Conclusion

In conclusion, high FGFR4 expression correlated with tumor progression and survival in both DGC and IGC, whereas high expression of FGFR1 and 2 correlated with tumor progression and survival in only DGC.

Molecular heterogeneity in the novel fusion gene APIP-FGFR2: Diversity of genomic breakpoints in gastric cancer with high-level amplifications at 11p13 and 10q26

Several novel fusion transcripts were identified by next-generation sequencing in gastric cancer; however, the breakpoint junctions have yet to be characterized. The present study characterized a plethora of APIP-FGFR2 genomic breakpoints in the SNU-16 gastric cancer cell line, which harbored homogeneously staining regions (hsrs) and double minute chromosomes. Oligonucleotide microarrays revealed high-level amplifications at chromosomes 8q24.1 (0.8 Mb region), 10q26 (1.1 Mb) and 11p13 (1.1 Mb). These amplicons contained MYC and PVT1 at chromosome 8q24.1, BRWD2, FGFR2 and ATE1 at chromosome 10q26, and 24 genes, including APIP, CD44, RAG1 and RAG2, at chromosome 11p13. Based on these findings, reverse transcription-polymerase chain reaction (PCR) was performed using various candidate gene primers to detect possible fusion transcripts, and several products using primer sets for the APIP and FGFR2 genes were detected. Eventually, three in-frame and two out-of-frame fusion transcripts were detected. Notably, PCR analysis of the entire genomic DNA detected three distinct genomic junctions. The breakpoints were within intron 5 of APIP, which contained three distinct breakpoints, and introns 5, 7 and 9 of FGFR2. Fluorescence in situ hybridization showed several fusion signals within hsrs using two short probes (~10-kb segments of a bacterial artificial chromosome clone) containing exons 2–5 of APIP or exons 11–13 of FGFR2. Although, for any given fusion, a multiplicity of transcripts is thought to be created by alternative splicing of one rearranged allele, the results of the present study suggested that genomic fusions of APIP and FGFR2 are generated in hsrs with a diversity of breakpoints that are then faithfully transcribed.

Gastrointestinal organoids: How they gut it out

The gastrointestinal tract is characterized by a self-renewing epithelium fueled by adult stem cells residing at the bottom of the intestinal crypt and gastric glands. Their activity and proliferation is strongly dependent on complex signaling pathways involving other crypt/gland cells as well as surrounding stromal cells. In recent years organoids are becoming increasingly popular as a new and powerful tool to study developmental or other biological processes. Organoids retain morphological and molecular patterns of the tissue they are derived from, are self-organizing, relatively simple to handle and accessible to genetic engineering. This review focuses on the developmental processes and signaling molecules involved in epithelial homeostasis and how a profound knowledge of these mechanisms allowed the establishment of a three dimensional organoid culture derived from adult gastrointestinal stem cells.

Molecular alterations in gastric cancer with special reference to the early-onset subtype

Currently, gastric cancer (GC) is one of the most frequently diagnosed neoplasms, with a global burden of 723000 deaths in 2012. It is the third leading cause of cancer-related death worldwide. There are numerous possible factors that stimulate the pro-carcinogenic activity of important genes. These factors include genetic susceptibility expressed in a single-nucleotide polymorphism, various acquired mutations (chromosomal instability, microsatellite instability, somatic gene mutations, epigenetic alterations) and environmental circumstances (e.g., Helicobcter pylori infection, EBV infection, diet, and smoking). Most of the aforementioned pathways overlap, and authors agree that a clear-cut pathway for GC may not exist. Thus, the categorization of carcinogenic events is complicated. Lately, it has been claimed that research on early-onset gastric carcinoma (EOGC) and hereditary GC may contribute towards unravelling some part of the mystery of the GC molecular pattern because young patients are less exposed to environmental carcinogens and because carcinogenesis in this setting may be more dependent on genetic factors. The comparison of various aspects that differ and coexist in EOGCs and conventional GCs might enable scientists to: distinguish which features in the pathway of gastric carcinogenesis are modifiable, discover specific GC markers and identify a specific target. This review provides a summary of the data published thus far concerning the molecular characteristics of GC and highlights the outstanding features of EOGC.

Fibroblast growth factors, old kids on the new block

The fibroblast growth factors (FGFs) are a family of cell intrinsic regulatory peptides that control a broad spectrum of cellular activities. The family includes canonic FGFs that elicit their activities by activating the FGF receptor (FGFR) tyrosine kinase and non-canonic members that elicit their activities intracellularly and via FGFR-independent mechanisms. The FGF signaling axis is highly complex due to the existence of multiple isoforms of both ligands and receptors, as well as cofactors that include the chemically heterogeneous heparan sulfate (HS) cofactors, and in the case of endocrine FGFs, the Klotho coreceptors. Resident FGF signaling controls embryonic development, maintains tissue homeostasis, promotes wound healing and tissue regeneration, and regulates functions of multiple organs. However, ectopic or aberrant FGF signaling is a culprit for various diseases, including congenital birth defects, metabolic disorder, and cancer. The molecular mechanisms by which the specificity of FGF signaling is achieved remain incompletely understood. Since its application as a druggable target has been gradually recognized by pharmaceutical companies and translational researchers, understanding the determinants of FGF signaling specificity has become even more important in order to get into the position to selectively suppress a particular pathway without affecting others to minimize side effects.

Evaluation of Fibroblast Growth Factor Receptor 2 Expression, Heterogeneity and Clinical Significance in Gastric Cancer

BACKGROUND

We aimed to evaluate the protein and mRNA expression of fibroblast growth factor receptor 2 (FGFR2) by immunohistochemistry (IHC) and mRNA in situ hybridization (ISH), respectively, and to assess the heterogeneity of FGFR2 expression in gastric cancer (GC).

METHODS

A tissue microarray containing 362 surgically resected GC tissues and 135 matched metastatic lymph nodes was evaluated using FGFR2b IHC and FGFR2 ISH. FGFR2 fluorescence ISH was also performed in 188 cases.

RESULTS

All FGFR2-amplified cases (5 of 188) showed FGFR2b protein and FGFR2 mRNA overexpression (p < 0.001), and FGFR2 amplification was not identified in FGFR2b IHC- and FGFR2 mRNA ISH-negative cases. Kaplan-Meier survival analysis revealed that FGFR2b protein and FGFR2 mRNA overexpression was significantly associated with a poor overall survival (p < 0.001 and p = 0.012, respectively), and multivariate analyses showed that FGFR2 mRNA overexpression was an independent biomarker of a poor overall survival. Intratumoral heterogeneity of FGFR2b protein and FGFR2 mRNA overexpression was observed in 5 of 9 (55.5%) and 18 of 21 (85.7%) cases, respectively. Discordant FGFR2b and FGFR2 expression results between primary and matched metastatic lymph nodes were observed in 5 of 9 (55.5%) and 4 of 14 (28.6%) cases, respectively.

CONCLUSIONS

Intratumoral heterogeneity and discordant FGFR2b expression in primary tumors and metastatic lymph nodes are common in GC.

Pazopanib, a novel multitargeted kinase inhibitor, shows potent in vitro antitumor activity in gastric cancer cell lines with FGFR2 amplification

Pazopanib is an orally bioavailable, ATP-competitive, multitargeted tyrosine kinase inhibitor mainly targeting VEGFR2 and PDGFR tyrosine kinases, but the biologic sequences of pazopanib activities beyond antiangiogenesis are poorly defined. We used a panel of 38 gastric cancer cell lines to test the efficacy of pazopanib. In a growth inhibition assay, genomic changes indicated that pazopanib had differential effects on cell growth. Treatment of the KATO-III, OCUM-2M, SNU-16, and HSC-39 gastric cancer cell lines harboring FGFR2 amplification with pazopanib resulted in marked decreases of cell survival with IC50 in ranges of 0.1 to 2.0 μmol/L, whereas the same treatment of those cell lines without FGFR2 amplification had no growth-inhibitory effects. In the ectopic FGFR2-expressing model, treatment with the indicated concentrations of pazopanib significantly inhibited cell growth and colony formation by FGFR2-expressing NIH 3T3 cells with wild-type (WT) FGFR2 and mutant FGFR2 (S252W). Pazopanib also selectively suppressed constitutive FGFR2 signaling and phosphorylation of downstream effectors. In cell-cycle analysis, FGFR2-amplified cells underwent cell-cycle arrest at the G1-S phase after pazopanib treatment, whereas there were no significant effects on cell-cycle progression in cells without FGFR2 amplification treated with pazopanib. In addition, pazopanib increased a substantial fraction of sub-G1 only in FGFR2-amplified cells. These findings show that the activation of FGFR2 signaling by amplification may be a critical mediator of cell proliferation in a small subset of gastric cancer patients and that pazopanib may provide genotype-correlated clinical benefits beyond the setting of highly vascular tumors.

Prognostic significance of the co-overexpression of fibroblast growth factor receptors 1, 2 and 4 in gastric cancer

The overexpression of fibroblast growth factor receptor (FGFR) 2 is an established prognostic factor and treatment target in gastric cancer. However, the roles of other FGFRs have not been fully elucidated. In this study, we investigated the correlations of the expression of FGFR1-4 with clinicopathological characteristics and outcomes in gastric cancer. Tumor samples were obtained from 222 patients with gastric adenocarcinoma who underwent gastrectomy between 2003 and 2007. The expression of each FGFR was measured in the tumors by immunohistochemical analysis. The overexpression of FGFR1, FGFR2 or FGFR4 was found to be significantly associated with tumor progression, including depth of invasion, lymph node metastasis, pathological stage and distant metastasis or recurrent disease. Patients exhibiting overexpression of FGFR1, FGFR2 or FGFR4 had a significantly poorer disease-specific survival (DSS; P<0.001, P=0.008 and P<0.001, respectively). Moreover, the co-overexpression of all three FGFRs was significantly associated with a poorer DSS compared to the expression of none or only one of the FGFRs (P<0.001 and P=0.001, respectively) and it was found to be an independent prognostic factor (HR=1.71, 95% CI: 1.02-2.85, P=0.041). In conclusion, high expression of FGFR1, FGFR2 or FGFR4 was associated with tumor progression and poor survival in patients with gastric cancer. Similar to FGFR2, FGFR1 and FGFR4 may be considered as prognostic factors and treatment targets in gastric cancer.

Palifermin for the protection and regeneration of epithelial tissues following injury: new findings in basic research and pre-clinical models

Keratinocyte growth factor (KGF) is a paracrine-acting epithelial mitogen produced by cells of mesenchymal origin, that plays an important role in protecting and repairing epithelial tissues. Pre-clinical data initially demonstrated that a recombinant truncated KGF (palifermin) could reduce gastrointestinal injury and mortality resulting from a variety of toxic exposures. Furthermore, the use of palifermin in patients with hematological malignancies reduced the incidence and duration of severe oral mucositis experienced after intensive chemoradiotherapy. Based upon these findings, as well as the observation that KGF receptors are expressed in many, if not all, epithelial tissues, pre-clinical studies have been conducted to determine the efficacy of palifermin in protecting different epithelial tissues from toxic injury in an attempt to model various clinical situations in which it might prove to be of benefit in limiting tissue damage. In this article, we review these studies to provide the pre-clinical background for clinical trials that are described in the accompanying article and the rationale for additional clinical applications of palifermin.

Saracatinib impairs the peritoneal dissemination of diffuse-type gastric carcinoma cells resistant to Met and fibroblast growth factor receptor inhibitors

Diffuse-type gastric carcinomas (DGC) exhibit more aggressive progression and poorer prognosis than intestinal-type and other gastric carcinomas. To identify potential therapeutic targets, we examined protein tyrosine phosphorylation in a panel of DGC and other gastric cancer cell lines. Protein tyrosine phosphorylation was significantly enhanced or altered in DGC cell lines compared with that in other gastric cancer cell lines. Affinity purification and mass spectrometry analysis of tyrosine-phosphorylated proteins identified Met as a protein that is preferentially expressed and phosphorylated in DGC cell lines. Unexpectedly, Met inhibitors blocked cell growth, Met downstream signaling and peritoneal dissemination in vivo in only a subset of cell lines that exhibited remarkable overexpression of Met. Likewise, only cell lines with overexpression of fibroblast growth factor receptor 2 (FGFR2) or phosphorylation of FRS2 were sensitive to an FGFR2 inhibitor. A Src inhibitor saracatinib impaired growth in cell lines that are insensitive to both Met and FGFR2 inhibitors. Saracatinib also effectively impaired peritoneal dissemination of Met-independent and FGFR2-independent SGC cells. Moreover, DGC cell lines exhibited nearly mutually exclusive susceptibility to Met, FGFR and Src inhibitors. These results suggest that DGC have distinct sensitivities to molecular target drugs and that targeting Src is beneficial in the treatment of DGC insensitive to Met and FGFR inhibition.

Tumour cell responses to new fibroblast growth factor receptor tyrosine kinase inhibitors and identification of a gatekeeper mutation in FGFR3 as a mechanism of acquired resistance

Fibroblast growth factor receptors (FGFRs) can act as driving oncoproteins in certain cancers, making them attractive drug targets. Here we have characterized tumour cell responses to two new inhibitors of FGFR1-3, AZ12908010 and the clinical candidate AZD4547, making comparisons with the well-characterized FGFR inhibitor PD173074. In a panel of 16 human tumour cell lines, the anti-proliferative activity of AZ12908010 or AZD4547 was strongly linked to the presence of deregulated FGFR signalling, indicating that addiction to deregulated FGFRs provides a therapeutic opportunity for selective intervention. Acquired resistance to targeted tyrosine kinase inhibitors is a growing problem in the clinic but has not yet been explored for FGFR inhibitors. To assess how FGFR-dependent tumour cells adapt to long-term FGFR inhibition, we generated a derivative of the KMS-11 myeloma cell line (FGFR(Y373C)) with acquired resistance to AZ12908010 (KMS-11R cells). Basal phosphorylated FGFR and FGFR-dependent downstream signalling were constitutively elevated and refractory to drug in KMS-11R cells. Sequencing of FGFR3 in KMS-11R cells revealed the presence of a heterozygous mutation at the gatekeeper residue, encoding FGFR3(V555M); consistent with this, KMS-11R cells were cross-resistant to AZD4547 and PD173074. These results define the selectivity and efficacy of two new FGFR inhibitors and identify a secondary gatekeeper mutation as a mechanism of acquired resistance to FGFR inhibitors that should be anticipated as clinical evaluation proceeds.

Grb2 controls phosphorylation of FGFR2 by inhibiting receptor kinase and Shp2 phosphatase activity

Constitutive receptor tyrosine kinase phosphorylation requires regulation of kinase and phosphatase activity to prevent aberrant signal transduction. A dynamic mechanism is described here in which the adaptor protein, growth factor receptor-bound protein 2 (Grb2), controls fibroblast growth factor receptor 2 (FGFR2) signaling by regulating receptor kinase and SH2 domain-containing protein tyrosine phosphatase 2 (Shp2) phosphatase activity in the absence of extracellular stimulation. FGFR2 cycles between its kinase-active, partially phosphorylated, nonsignaling state and its Shp2-dephosphorylated state. Concurrently, Shp2 cycles between its FGFR2-phosphorylated and dephosphorylated forms. Both reciprocal activities of FGFR2 and Shp2 were inhibited by binding of Grb2 to the receptor. Phosphorylation of Grb2 by FGFR2 abrogated its binding to the receptor, resulting in up-regulation of both FGFR2's kinase and Shp2's phosphatase activity. Dephosphorylation of Grb2 by Shp2 rescued the FGFR2-Grb2 complex. This cycling of enzymatic activity results in a homeostatic, signaling-incompetent state. Growth factor binding perturbs this background cycling, promoting increased FGFR2 phosphorylation and kinase activity, Grb2 dissociation, and downstream signaling. Grb2 therefore exerts constitutive control over the mutually dependent activities of FGFR2 and Shp2.

Molecular targeted therapies in advanced gastric cancer: does tumor histology matter?

It is increasingly recognized that gastric cancer is a heterogeneous disease which may be divided into subgroups based on histological, anatomical, epidemiological and molecular classifications. Distinct molecular drivers and tumor biology, and thus different treatment targets and predictive biomarkers, may be implicated in each subtype. However, there is little evidence in the literature regarding the correlation among these different classifications, and particularly the molecular aberrations present in each subtype. In this review, we approach advanced gastric cancer (AGC) by presenting aberrant molecular pathways and their potential therapeutic targets in gastric cancer according to histological and anatomical classification, dividing gastric cancer into proximal nondiffuse, distal nondiffuse and diffuse disease. Several pathways are involved predominantly, although not exclusively, in different subtypes. This may help to explain the disappointing results of many published AGC trials in which study populations were heterogeneous regardless of clinicopathological characteristics of the primary tumor. Histological and anatomical classification may provide insights into tumor biology and facilitate selection of an enriched patient population for targeted agents in future studies and in the clinic. However, some molecular pathways implicated in gastric cancer have not been studied in correlation with histological or anatomical subtypes. Further studies are necessary to confirm the suggestion that such classification may predict tumor biology and facilitate selection of an enriched patient population for targeted agents in future studies and in the clinic.

Fibroblast growth factor receptor 2 gene amplification status and its clinicopathologic significance in gastric carcinoma

Fibroblast growth factor receptor 2 is a member of receptor tyrosine kinase family, and fibroblast growth factor receptor 2 gene amplification or missense mutation has been observed in various human cancers, including gastric carcinoma. Recent studies have shown that anti-fibroblast growth factor receptor 2 agents inhibit tumor progression in various human cancers, such as endometrial carcinoma and gastric carcinoma, which remains one of the most frequent causes of cancer-related death worldwide. We considered that knowledge of the status of fibroblast growth factor receptor 2 gene amplification in gastric carcinoma might aid in targeted cancer therapy. In this study, fibroblast growth factor receptor 2 amplification status was evaluated by fluorescence in situ hybridization in 313 surgically resected gastric carcinoma tissues, and the results were validated by quantitative real-time polymerase chain reaction. In addition, potential associations between clinicopathologic parameters and the presence of fibroblast growth factor receptor 2 amplification were investigated, and survival analysis was performed. Of the 313 cases, 14 (4.5%) showed fibroblast growth factor receptor 2 amplification by fluorescence in situ hybridization. Fibroblast growth factor receptor 2 amplification was found to be associated with a higher pT stage (P = .023), higher pN stage (P = .038), and distant metastasis (P = .009) and to be significantly associated with lower cancer-specific survival by univariate analysis (P = .012). Gastric carcinoma with fibroblast growth factor receptor 2 amplification was found to be associated with advanced disease and a poor prognosis. We believe that the determination of fibroblast growth factor receptor 2 amplification status could allow the identification of a subset of cancers sensitive to targeted fibroblast growth factor receptor 2 inhibitor-based therapy.

FGFR2 isoforms support epithelial-stromal interactions in thyroid cancer progression

Alternate splicing yields two distinct isoforms of the fibroblast growth factor (FGF) receptor FGFR2-IIIb and FGFR2-IIIc varying their extracellular structure in human thyroid cancer, in which FGFR expression is commonly dysregulated. In this study, we characterized the function of these variants in modulating thyroid cancer behavior. Enforced expression of either FGFR2-IIIb or FGFR2-IIIc in thyroid epithelial cancer cells reduced expression of fibronectin, MAGE-A3 and MMP9, while increasing p21 and enhancing Rb dephosphorylation. Consistent with these tumor-suppressive properties, FGFR2-IIIb and FGFR2-IIIc each diminished invasive behavior in vitro and reduced tumor growth and metastasis in vivo. Notably, these effects contrasted with those produced by expression of these FGFR isoforms in fibroblasts, in which they both stimulated cell growth. Moreover, in xenograft tumors generated by coimplantation of epithelial and fibroblast cells expressing that same isoform, there was no significant effect on tumor progression. Conversely, FGFR2-IIIb expression in epithelial cells yielded higher FGF4/FGF7 expression that, in the presence of FGFR2-IIIc-expressing fibroblasts, enhanced tumor progression. Together, our findings highlight the importance of cellular context in assigning growth properties to growth factor receptor isoforms. More specifically, they show how alternative splicing of FGFR2 yields heteroisoforms critical to the growth-promoting actions of FGFs that exert distinct epithelial-stromal effects in thyroid cancer.

FGFR2 gene amplification and clinicopathological features in gastric cancer

Background:

Frequency of FGFR2 amplification, its clinicopathological features, and the results of high-throughput screening assays in a large cohort of gastric clinical samples remain largely unclear.

Methods:

Drug sensitivity to a fibroblast growth factor receptor (FGFR) inhibitor was evaluated in vitro. The gene amplification of the FGFRs in formalin-fixed, paraffin-embedded (FFPE) gastric cancer tissues was determined by a real-time PCR-based copy number assay and fluorescence in situ hybridisation (FISH).

Results:

FGFR2 amplification confers hypersensitivity to FGFR inhibitor in gastric cancer cell lines. The copy number assay revealed that 4.1% (11 out of 267) of the gastric cancers harboured FGFR2 amplification. No amplification of the three other family members (FGFR1, 3 and 4) was detected. A FISH analysis was performed on 7 cases among 11 FGFR2-amplified cases and showed that 6 of these 7 cases were highly amplified, while the remaining 1 had a relatively low grade of amplification. Although the difference was not significant, patients with FGFR2 amplification tended to exhibit a shorter overall survival period.

Conclusion:

FGFR2 amplification was observed in 4.1% of gastric cancers and our established PCR-based copy number assay could be a powerful tool for detecting FGFR2 amplification using FFPE samples. Our results strongly encourage the development of FGFR-targeted therapy for gastric cancers with FGFR2 amplification.

Analysis of DNA copy number aberrations by multiple ligation-dependent probe amplification on 50 intestinal type gastric cancers

BACKGROUND AND OBJECTIVES

The molecular genetic alterations leading to gastric malignancy are largely unknown. This study aimed to unravel the genomic DNA copy number aberrations (CNAs) profile during gastric tumorigenesis.

METHODS

In this study, we performed genomic profiling in a set of 50 intestinal type gastric carcinomas by a PCR-based relative quantification method, multiple ligation-dependent probe amplification (MLPA) with 112 cancer-related gene loci selected throughout each human chromosome as probes of MLPA assay.

RESULTS

Numerous chromosomal DNA CNAs, including gains of 3p22, 4q25, 8q24, 11p13, and 20q13, and losses of 1p36 and 9p21, were identified by MLPA assay as recurrent DNA CNAs in gastric cancer. Moreover, we found the median numbers of gains, losses, and total CNAs were significantly higher in lymph node metastasis positive patients than in cases without metastasis. And gain of 11p13 and losses of 9p21.3, 11q13.3, 17q25.3, and 22q11.23 were associated with lymph node metastasis (P < 0.05). Finally, two major groups, including G1 + 2 with a large number of CNAs and G3 + 4 with a small number of CNAs, can be successfully distinguished by hierarchical cluster analysis.

CONCLUSIONS

Our results proved MLPA is a reliable and efficient method to evaluate DNA copy number changes in gastric cancers.

Cancer-stromal interactions in scirrhous gastric carcinoma

Fibroblasts play an important role in the progression, growth and spread of gastric cancers. Cancer-stroma interactions have been especially evident in the scirrhous type of gastric carcinoma. Fibroblasts are associated with the cancer progression at the primary and metastatic site. The proliferative and invasive ability of scirrhous gastric cancer cells are closely associated with the growth factors produced by organ-specific fibroblasts. Fibroblasts are therefore a key determinant in the malignant progression of gastric cancer and represent an important target for cancer therapies.

A review of in vitro and in vivo models of oesophageal and gastric cancer

IMPORTANCE OF THE FIELD

Oesophageal and gastric cancers are leading causes of cancer-related mortality. In the era of targeted therapy and individualized treatment strategies, novel treatments for upper-gastrointestinal cancers are only just emerging compared to significant advances in other solid tumour types such as colorectal, breast and lung cancers. Clinical trials are investigating the value of established targeted agents for the treatment of oesophageal and gastric malignancies; however none are used in routine clinical practice.

AREAS COVERED IN THIS REVIEW

In this review we have looked at current in vitro and in vivo models of oesophageal and gastric cancers which may improve our understanding of the biology of these tumours and lead to the development of new preventative, diagnostic and therapeutic approaches.

WHAT THE READER WILL GAIN

We discuss the limitations of our current models and the challenges associated with research into these cancers.

TAKE HOME MESSAGE

The lack of appropriate models for drug development in oesophageal and gastric cancers has hindered the progress of targeted therapy in this field.

Krüppel-like factor 12 plays a significant role in poorly differentiated gastric cancer progression

Gastric cancer is the second common malignant neoplasia in Japan, and its poorly differentiated form is a deadly disease. To identify novel candidate oncogenes contributing to its genesis, we examined copy-number alterations in 50 primary poorly differentiated gastric cancers using an array-based comparative genomic hybridization (array-CGH). Many genetic changes were identified, including a novel amplification of the 13q22 locus. Several genes are located in this locus, and selective knockdown of one for the Krüppel-like factor 12 (KLF12) induced significant growth-arrest in the HGC27 gastric cancer cell line. Microarray analysis also demonstrated that genes associated with cell proliferation were mostly changed by KLF12 knockdown. To explore the oncogenic function of KLF12, we introduced a full length of human KLF12 cDNA into NIH3T3 and AZ-521 cell lines and found that overexpression significantly enhanced their invasive potential. In clinical samples, KLF12 mRNA in cancer tissue was increased in 11 of 28 cases (39%) when compared with normal gastric epithelium. Clinicopathological analysis further demonstrated a significant correlation between KLF12mRNA levels and tumor size (p = 0.038). These data suggest that the KLF12 gene plays an important role in poorly differentiated gastric cancer progression and is a potential target of therapeutic measures.

Epstein-Barr virus-associated epithelial and mesenchymal neoplasms

Epstein-Barr virus (EBV) is a ubiquitous human pathogen that usually maintains a harmonious relationship with its host. Rarely, this host-virus balance is perturbed, causing a diverse group of malignancies in both immunocompetent and immunosuppressed patients. In addition to its role in hematologic malignancies (Burkitt lymphoma, subsets of Hodgkin and T-cell lymphomas, posttransplant lymphomas), EBV has been implicated in both epithelial (undifferentiated nasopharyngeal carcinoma, a subset of gastric adenocarcinomas) and mesenchymal (EBV-associated smooth muscle tumor, inflammatory pseudotumor-like follicular dendritic cell tumor) neoplasms. This review will focus on EBV-associated epithelial and mesenchymal neoplasms.

Cytogenetic and molecular aspects of gastric cancer: clinical implications

Gastric cancer is of major importance world-wide being the second most common cause of cancer-related death in the world. According to Lauren's histological classification gastric cancer is divided in two groups, the better differentiated intestinal carcinomas and the poorly differentiated diffuse-type cancers. The genetic changes underlying the initiation and progression of gastric cancer are not well defined. Gastric carcinogenesis is a multistep process involving a number of genetic and epigenetic factors. Although it has been proposed that different genetic pathways exist for differentiated and undifferentiated carcinomas, the two histological subtypes of gastric cancer share some common genetic alterations. Currently, tumor histology and pathologic stage are the major prognostic variables used in the clinical practice for gastric cancer patients. However, it is known that tumors with similar morphology may differ in biological aggressiveness, prognosis and response to treatment. Molecular genetic analysis of gastric cancer revealed a number of associations of certain genetic changes with pathological features, tumor biological behavior and prognosis of gastric cancer patients, suggesting that these genetic abnormalities might play an important role in gastric tumorigenesis. Increasing evidence suggests that the molecular genetic changes could be helpful in the clinical setting, contributing to prognosis and management of patients. Regarding epigenetic events in gastric tumorigenesis, a number of methylating markers have been proposed for risk assessment, prognostic evaluation and as therapeutic targets. However, further research is required in order to systematically investigate the genetic changes in gastric cancer estimating also their usefulness in the clinical practice. A good understanding of the genetic changes underlying gastric carcinogenesis may provide new perspectives for prognosis and screening of high risk individuals. Some of the genetic alterations could definitely improve tumor classification and management of gastric cancer patients. Also, based on molecular data identified in gastric cancer novel therapeutics might help to improve the treatment of this disease.

Ovarian dysgerminoma and Apert syndrome

Apert syndrome is an autosomal dominant disorder that results from gain-of-function mutations in the FGFR2 gene. FGFR2 also has been shown to be amplified in stomach and breast cancers. We report the case of a 13-year-old female with Apert syndrome who developed an ovarian dysgerminoma. The FGFR2 exon 7 sequencing showed the classical Apert syndrome c.758C > G transversion (p.Pro253Arg). The genomic analyses of the tumor cells showed low level gains and losses of several chromosomes. This is the second report of the association of Apert syndrome with cancer. Our observation raises the hypothesis of a role for FGFR2 mutations in tumorigenesis.

Transforming properties of TC-1 in human breast cancer: interaction with FGFR2 and beta-catenin signaling pathways

Breast cancer development is associated with gene amplification and over expression that is believed to have a causative role in oncogenesis. Previous studies have demonstrated that over expression of TC-1(C8orf4) mRNA occurs in approximately 50% of breast cancer cell lines and primary tumor specimens. Here, we show that TC-1 has transforming properties in human mammary epithelial (HME) cells and its expression is mechanistically linked to FGFR signaling cascades. In vitro experiments demonstrate that TC-1 over expression mediates both anchorage-independent and growth factor-independent proliferation of HME cells. TC-1 was down regulated by the FGFR inhibitor PD173074 in the breast cancer cell line SUM-52 that also has an FGFR2 gene amplification and over expression. Furthermore, forced expression of FGFR2 in HME cells increased the level of expression of endogenous TC-1 mRNA. TC-1 has been implicated as a modulator of Wnt/beta-catenin signaling in 293 cells and in gastric cancer cells. However, while we did find increased expression of a subset of beta-catenin target genes in TC-1 over expressing cells, we did not find an association of TC-1 with global expression of beta-catenin target genes in our cells. Taken together, our data suggest that TC-1 over expression is transforming and may link with the FGFR pathway in a subset of breast cancer.

AZD2171 shows potent antitumor activity against gastric cancer over-expressing fibroblast growth factor receptor 2/keratinocyte growth factor receptor

PURPOSE

AZD2171 is an oral, highly potent, and selective vascular endothelial growth factor signaling inhibitor that inhibits all vascular endothelial growth factor receptor tyrosine kinases. The purpose of this study was to investigate the activity of AZD2171 in gastric cancer.

EXPERIMENTAL DESIGN

We examined the antitumor effect of AZD2171 on the eight gastric cancer cell lines in vitro and in vivo.

RESULTS

AZD2171 directly inhibited the growth of two gastric cancer cell lines (KATO-III and OCUM2M), with an IC(50) of 0.15 and 0.37 micromol/L, respectively, more potently than the epidermal growth factor receptor tyrosine kinase inhibitor gefitinib. Reverse transcription-PCR experiments and immunoblotting revealed that sensitive cell lines dominantly expressed COOH terminus-truncated fibroblast growth factor receptor 2 (FGFR2) splicing variants that were constitutively phosphorylated and spontaneously dimerized. AZD2171 completely inhibited the phosphorylation of FGFR2 and downstream signaling proteins (FRS2, AKT, and mitogen-activated protein kinase) in sensitive cell lines at a 10-fold lower concentration (0.1 micromol/L) than in the other cell lines. An in vitro kinase assay showed that AZD2171 inhibited kinase activity of immunoprecipitated FGFR2 with submicromolar K(i) values ( approximately 0.05 micromol/L). Finally, we assessed the antitumor activity of AZD2171 in human gastric tumor xenograft models in mice. Oral administration of AZD2171 (1.5 or 6 mg/kg/d) significantly and dose-dependently inhibited tumor growth in mice bearing KATO-III and OCUM2M tumor xenografts.

CONCLUSIONS

AZD2171 exerted potent antitumor activity against gastric cancer xenografts overexpressing FGFR2. The results of these preclinical studies indicate that AZD2171 may provide clinical benefit in patients with certain types of gastric cancer.

Epigenetically controlled fibroblast growth factor receptor 2 signaling imposes on the RAS/BRAF/mitogen-activated protein kinase pathway to modulate thyroid cancer progression

Fibroblast growth factor (FGF) signals play fundamental roles in development and tumorigenesis. Thyroid cancer is an example of a tumor with nonoverlapping genetic mutations that up-regulate mitogen-activated protein kinase (MAPK). Here, we show that FGF receptor 1 (FGFR1), which is expressed mainly in neoplastic thyroid cells, propagates MAPK activation and promotes tumor progression. In contrast, FGFR2 is down-regulated in neoplastic thyroid cells through DNA promoter methylation. Reexpression of FGFR2 competes with FGFR1 for the immediate substrate FGFR substrate 2 to impede signaling upstream of the BRAF/MAPK pathway. These data unmask an epigenetically controlled FGFR2 signal that imposes precisely on the intragenically modified BRAF/MAPK pathway to modulate thyroid cancer behavior.

Deciphering the underlying genetic and epigenetic events leading to gastric carcinogenesis

Gastric cancer is a common aggressive malignancy. Although its incidence shows considerable variation among different countries, gastric cancer is still a major health problem worldwide. The causes of stomach cancer are not completely understood. What is clear is that gastric cancer is a multi-stage process involving genetic and epigenetic factors. This review is an in-depth study of the known genetic and epigenetic processes in the development of this tumor, and delineates possible approaches in gene and epigenetic therapy.