Current status of targeted therapies in advanced gastric cancer

Advances in targeted therapy for human epidermal growth factor receptor 2 positive in advanced gastric cancer

Emerging therapeutic methods represented by targeted therapy are effective supplements to traditional first-line chemoradiotherapy resistance. Human epidermal growth factor receptor 2 (HER2) is one of the most important targets in targeted therapy for gastric cancer. Trastuzumab combined with chemotherapy has been used as the first-line treatment for advanced gastric cancer. The safety and efficacy of pertuzumab and margetuximab in the treatment of gastric cancer have been verified. However, monoclonal antibodies, due to their large molecular weight, inability to penetrate the blood-brain barrier, and drug resistance, lead to decreased therapeutic efficacy, so it is necessary to explore the efficacy of other HER2-targeting therapies in gastric cancer. Small-molecule tyrosine kinase inhibitors, such as lapatinib and pyrrotinib, have the advantages of small molecular weight, penetrating the blood-brain barrier and high oral bioavailability, and are expected to become the drugs of choice for perioperative treatment and neoadjuvant therapy of gastric cancer after validation by large-scale clinical trials in the future. Antibo-drug conjugate, such as T-DM1 and T-DXd, can overcome the resistance of monoclonal antibodies despite their different mechanisms of tumor killing, and are a supplement for the treatment of patients who have failed the treatment of monoclonal antibodies such as trastuzumab. Therefore, after more detailed stratification of gastric cancer patients, various gastric cancer drugs targeting HER2 are expected to play a more significant role.

SLC39A10 promotes malignant phenotypes of gastric cancer cells by activating the CK2-mediated MAPK/ERK and PI3K/AKT pathways

Solute carrier family 39 member 10 (SLC39A10) belongs to a subfamily of zinc transporters and plays a key role in B-cell development. Previous studies have reported that its upregulation promotes breast cancer metastasis by enhancing the influx of zinc ions (Zn2+); however, its role in gastric cancer remains totally unclear. Here, we found that SLC39A10 expression was frequently increased in gastric adenocarcinomas and that SLC39A10 upregulation was strongly associated with poor patient outcomes; in addition, we identified SLC39A10 as a direct target of c-Myc. Functional studies showed that ectopic expression of SLC39A10 in gastric cancer cells dramatically enhanced the proliferation, colony formation, invasiveness abilities of these gastric cancer cells and tumorigenic potential in nude mice. Conversely, SLC39A10 knockdown inhibited gastric cancer cell proliferation and colony formation. Mechanistically, SLC39A10 exerted its carcinogenic effects by increasing Zn2+ availability and subsequently enhancing the enzyme activity of CK2 (casein kinase 2). As a result, the MAPK/ERK and PI3K/AKT pathways, two major downstream effectors of CK2, were activated, while c-Myc, a downstream target of these two pathways, formed a vicious feedback loop with SLC39A10 to drive the malignant progression of gastric cancer. Taken together, our data demonstrate that SLC39A10 is a functional oncogene in gastric cancer and suggest that targeting CK2 is an alternative therapeutic strategy for gastric cancer patients with high SLC39A10 expression.

A comprehensive update on early gastric cancer: defining terms, etiology, and alarming risk factors

INTRODUCTION

Early gastric cancer (EGC) is a well-defined gastric malignancy that is limited to the mucosa or submucosa, irrespective of lymph node metastasis. At an early stage, gastric cancer often does not cause symptoms until it becomes advanced, and it is a heterogeneous disease and usually encountered in its late stages.

AREA COVERED

This comprehensive review will provide a novel insight into the evaluation of EGC epidemiology, defining terms, extensive etiology and risk factors, and timely diagnosis since prevention is an essential approach for controlling this cancer and reducing its morbidity and mortality.

EXPERT OPINION

The causative manner of EGC is complex and multifactorial. In recent years, researchers have made significant contributions to understanding the etiology and pathogenesis of EGC, and standardization in the evaluation of disease activity. Though the incidence of this cancer is steadily declining in some advanced societies owing to appropriate interventions, there remains a serious threat to health in developing nations. Early detection of resectable gastric cancer is crucial for better patient outcomes.

The promising role of monoclonal antibodies for gastric cancer treatment

Gastric cancer (GC) is the second leading cause of cancer-related death world-wide. Despite improvements in prevention, early detection and various therapeutic options, the prognosis is still poor. GC is often diagnosed at an advanced stage with survivals less than 1 year. Chemotherapy as the mainstay of treatment in advanced stage is not of notable advantages, underlining the need for novel more effective therapeutic options. Based on current knowledge of molecular and cellular mechanisms, a number of novel biologic approaches such as monoclonal antibodies have been recently introduced for cancer treatment that mainly affect the immune system or target signaling pathways playing role in cancer and metastasis development. In this review, various monoclonal antibodies for GC therapy were explained.

HER2 Heterogeneity in Gastric Cancer: A Comparative Study, Using Two Commercial Antibodies

BACKGROUND

Although amplification of the gene encoding human epidermal growth factor receptor 2 (HER2) is used as an indicator for response to trastuzumab, the reported response rate is low, and few patients with gastric cancer (GC) benefit from this individualized therapy. The aim of this study was to examine the expression of c-erbB-2 oncoprotein (HER2), in GC samples, using two commercial immunohistochemical (IHC) antibodies, and to validate the results by checking HER2 gene amplification by fluorescence in situ hybridization (FISH).

METHODS

We assessed the IHC expression of HER2 using the polyclonal antibody from Dako and CB11 clone from Leica, in 93 consecutive cases of GC samples. In all of the cases, FISH analysis was also performed using the BOND-MAX platform.

RESULTS

No significant difference was observed between the two HER2 antibodies. Of the 93 cases, 22.58% demonstrated at least focal and 1+ HER2 positivity. Seven cases (7.53%) exhibited 3+ expression, and another 7 carcinomas (7.53%) were equivocal (2+). HER2 amplification was seen in 11 cases (11.83%), 10 of which were differentiated adenocarcinomas. In 5 of the cases, 2-5 sections were examined, which proved the extremely high intratumorally/intraglandular heterogeneity. FISH heterogeneity was higher in cases with only 2+ positivity on IHC assessment, compared with those showing at least one small focus of 3+ overexpression. HER2 amplification proved to be an independent negative prognostic factor.

CONCLUSIONS

Due to the highly heterogeneous aspect of GC, at least 3-4 slides should be assessed by IHC, before considering a tumor to be HER2-negative. In cases with small 3+ foci representing less than 5% of tumor and in equivocal (2+) cases, FISH analysis remains the gold standard method.

Regional Hyperthermia Combined with Chemotherapy in Advanced Gastric Cancer

Introduction

This study aims to investigate the potential effects of regional hyperthermia combined with chemotherapy (RHCT) as a treatment strategy for advanced gastric cancer (AGC).

Method

118 AGC patients were randomly divided into treatment plans with chemotherapy (CT) alone or with RHCT. The prognostic value of clinicopathologic characteristics was assessed in terms of overall survival of AGC patients.

Results

The disease control rate was determined to be 70.9% and 46.0% for the RHCT and CT group, respectively (P = 0.006). The median survival was determined to be 23.5 months for the RHCT group and 14.0 months for the CT group (P = 0.010). The 3-year survival rate for the RHCT group was 11.4% and 0% for the CT group (P = 0.018). No difference in grade 3 or 4 adverse events was observed between the two groups (P > 0.05). Multivariate analysis showed that hyperthermia, disease stage, Glasgow prognostic score, and abdominal metastasis were closely associated with the prognosis of these AGC patients.

Conclusion

The study suggests that combination treatment with RHCT for AGC has clinical potential for both short- and long-term curative effects without compromising toxicity.

Membranous or Cytoplasmic HER2 Expression in Colorectal Carcinoma: Evaluation of Prognostic Value Using Both IHC & BDISH

BACKGROUND

Human epidermal growth factor recptor-2 (HER2) was identified as a driver gene in several types of cancers with both prognostic and predictive value. However, the molecular association of HER2 gene mutation with HER2 gene amplification and/or protein expression in cancer tissues has not been clearly defined. Moreover, there is little information available on HER2 status role in tumor progression and metastasis in colorectal carcinoma (CRC) compared to other solid tumors. The aim of this study was to evaluate both HER2 amplification and protein expression profiles using immunohistochemistry (IHC) and bright-field dual in situ hybridization (BDISH) techniques, respectively.

PATIENTS AND METHODS

Tissue microarray (TMA) was constructed to accommodate a total of 243 CRC formalin-fixed paraffin embedded (FFPE) samples of consent patients and stained by IHC and BDISH methods. The expression patterns of HER2 protein status were evaluated and correlated to HER2 gene amplification status and then assessed for its prognostic value.

RESULTS

The expression profile of 58% samples showed cytoplasmic expression patterns of different categories. Interestingly, only 1% showed strong (+3) membranous expression pattern of HER2 with perfect match with their corresponding gene amplification status (>2). However, the cytoplasmic HER2 protein status did not show significant correlation with most clinicopathological features and survival outcomes except with age (p = 0.04) and tumor size (p = 0.03).

CONCLUSION

We demonstrated that the membranous HER2 gene/protein status is infrequent, while the main fraction of HER2 overexpression was cytoplasmic and lacking prognostic value. This cytoplasmic HER2 overexpression was induced through a gene-amplification independent pathway, making the HER2 gene status evaluation approach in those cases not worthy. Further investigations about the molecular pathways of the cytoplasmic HER2 protein in CRC and its associations with survival outcomes are required to allow either a breakthrough in CRC management; or to confirm the hypothesis of a marginal role in CRC onset and progression.

Clinical significance of overexpression of NRG1 and its receptors, HER3 and HER4, in gastric cancer patients

BACKGROUND

Neuregulin 1 (NRG1), a ligand for human epidermal growth factor (HER) 3 and HER4, can activates cell signaling pathways to promote carcinogenesis and metastasis.

METHODS

To investigate the clinicopathologic significance of NRG1 and its receptors, immunohistochemistry was performed for NRG1, HER3, and HER4 in 502 consecutive gastric cancers (GCs). Furthermore, HER2, microsatellite instability (MSI), and Epstein-Barr virus (EBV) status were investigated. NRG1 gene copy number (GCN) was determined by dual-color fluorescence in situ hybridization (FISH) in 388 available GCs.

RESULTS

NRG1 overexpression was observed in 141 (28.1%) GCs and closely correlated with HER3 (P = 0.034) and HER4 (P < 0.001) expression. NRG1 overexpression was significantly associated with aggressive features, including infiltrative tumor growth, lymphovascular, and neural invasion, high pathologic stage, and poor prognosis (all P < 0.05), but not associated with EBV, MSI, or HER2 status. Multivariate analysis identified NRG1 overexpression as an independent prognostic factor for survival (P = 0.040). HER3 and HER4 expressions were observed in 157 (31.3%) and 277 (55.2%), respectively. In contrast to NRG1, expression of these proteins was not associated with survival. NRG1 GCN gain (GCN ≥ 2.5) was detected in 14.7% patients, including two cases of amplification, and was moderately correlated with NRG1 overexpression (κ, 0.459; P < 0.001).

CONCLUSIONS

Although our results indicate a lack of prognostic significance of HER3 and HER4 overexpression in GC, overexpression of their ligand, NRG1, was associated with aggressive clinical features and represented an independent unfavorable prognostic factor. Therefore, NRG1 is a potential prognostic and therapeutic biomarker in GC patients.

Role of Rac1 Pathway in Epithelial-to-Mesenchymal Transition and Cancer Stem-like Cell Phenotypes in Gastric Adenocarcinoma

Rac1, a Rho GTPase family member, is dysregulated in a variety of tumor types including gastric adenocarcinoma, but little is known about its role in cancer stem-like cells (CSCs). Therefore, Rac1 activity and inhibition were examined in gastric adenocarcinoma cells and mouse xenograft models for epithelial-to-mesenchymal transition (EMT) and CSC phenotypes. Rac1 activity was significantly higher in spheroid-forming or CD44⁺ gastric adenocarcinoma CSCs compared with unselected cells. Rac1 inhibition using Rac1 shRNA or a Rac1 inhibitor (NSC23766) decreased expression of the self-renewal transcription factor, Sox-2, decreased spheroid formation by 78%-81%, and prevented tumor initiation in immunodeficient mice. Gastric adenocarcinoma CSCs had increased expression of the EMT transcription factor Slug, 4.4- to 8.3-fold greater migration, and 4.2- to 12.6-fold greater invasion than unselected cells, and these increases could be blocked completely with Rac1 inhibition. Gastric adenocarcinoma spheroid cells were resistant to 5-fluorouracil and cisplatin chemotherapy, and this chemotherapy resistance could be reversed with Rac1 shRNA or NSC23766. The PI3K/Akt pathway may be upstream of Rac1, and JNK may be downstream of Rac1. In the MKN-45 xenograft model, cisplatin inhibited tumor growth by 50%, Rac1 inhibition by 35%, and the combination by 77%. Higher Rac1 activity, in clinical specimens from gastric adenocarcinoma patients who underwent potentially curative surgery, correlated with significantly worse survival (P = 0.017). In conclusion, Rac1 promotes the EMT program in gastric adenocarcinoma and the acquisition of a CSC state. Rac1 inhibition in gastric adenocarcinoma cells blocks EMT and CSC phenotypes, and thus may prevent metastasis and augment chemotherapy.Implications: In gastric adenocarcinoma, therapeutic targeting of the Rac1 pathway may prevent or reverse EMT and CSC phenotypes that drive tumor progression, metastasis, and chemotherapy resistance. Mol Cancer Res; 15(8); 1106-16. ©2017 AACR.

An epidermal growth factor receptor exon 19 mutation in a mucin-producing gastric cancer sample from a Chinese patient

OBJECTIVE

To determine whether a subgroup of gastric cancer patients might benefit from epidermal growth factor receptor-tyrosine kinase inhibitors.

METHODS

A total of 103 gastric cancer samples were collected for this study. High-resolution melting and deoxyribonucleic acid sequencing were used to detect epidermal growth factor receptor mutations in exons 19 and 21.

RESULTS

Polymerase chain reaction-high-resolution melting was successfully performed on all 103 samples. Aberrant melting curves were found in only one sample. Sanger sequencing revealed a 15 bp deletion (c.2235_2249del; p.Glu746_Ala750del) in epidermal growth factor receptor exon 19. The sample was from a male patient, and the pathological diagnosis was a mucin-producing gastric cancer with lymph node metastasis. To date, this is the first report on epidermal growth factor receptor exon 19 mutation in gastric cancer.

CONCLUSIONS

An epidermal growth factor receptor mutation in exon 19 was identified in mucin-producing gastric cancer sample from a male patient. This mutation indicates that the small subgroup of patients with mucin-producing gastric cancer might benefit from epidermal growth factor receptor-tyrosine kinase inhibitors.

Chemotherapy Resistance in Diffuse-Type Gastric Adenocarcinoma Is Mediated by RhoA Activation in Cancer Stem-Like Cells

PURPOSE

The Lauren diffuse type of gastric adenocarcinoma (DGA), as opposed to the intestinal type (IGA), often harbors mutations in RHOA, but little is known about the role of RhoA in DGA.

EXPERIMENTAL DESIGN

We examined RhoA activity and RhoA pathway inhibition in DGA cell lines and in two mouse xenograft models. RhoA activity was also assessed in patient tumor samples.

RESULTS

RhoA activity was higher in DGA compared with IGA cell lines and was further increased when grown as spheroids to enrich for cancer stem-like cells (CSCs) or when sorted using the gastric CSC marker CD44. RhoA shRNA or the RhoA inhibitor Rhosin decreased expression of the stem cell transcription factor, Sox2, and decreased spheroid formation by 78% to 81%. DGA spheroid cells had 3- to 5-fold greater migration and invasion than monolayer cells, and this activity was Rho-dependent. Diffuse GA spheroid cells were resistant in a cytotoxicity assay to 5-fluorouracil and cisplatin chemotherapy, and this resistance could be reversed with RhoA pathway inhibition. In two xenograft models, cisplatin inhibited tumor growth by 40% to 50%, RhoA inhibition by 32% to 60%, and the combination by 77% to 83%. In 288 patient tumors, increased RhoA activity correlated with worse overall survival in DGA patients (P = 0.017) but not in IGA patients (P = 0.612).

CONCLUSIONS

RhoA signaling promotes CSC phenotypes in DGA cells. Increased RhoA activity is correlated with worse overall survival in DGA patients, and RhoA inhibition can reverse chemotherapy resistance in DGA CSC and in tumor xenografts. Thus, the RhoA pathway is a promising new target in DGA patients.

Celastrol inhibits gastric cancer growth by induction of apoptosis and autophagy

Recently, the interest in natural products for the treatment of cancer is increasing because they are the pre-screened candidates. In the present study, we demonstrate the therapeutic effect of celastrol, a triterpene extracted from the root bark of Chinese medicine on gastric cancer. The proliferation of AGS and YCC-2 cells were most sensitively decreased in six kinds of gastric cancer cell lines after the treatment with celastrol. Celastrol inhibited the cell migration and increased G1 arrest in cell-cycle populations in both cell lines. The treatment with celastrol significantly induced autophagy and apoptosis and increased the expression of autophagy and apoptosis-related proteins. We also found an increase in phosphorylated AMPK following a decrease in all phosphorylated forms of AKT, mTOR and S6K after the treatment with celastrol. Moreover, gastric tumor burdens were reduced in a dose-dependent manner by celastrol administration in a xenografted mice model. Taken together, celastrol distinctly inhibits the gastric cancer cell proliferation and induces autophagy and apoptosis. [BMB Reports 2014; 47(12): 697-702]

Serum HER2 extracellular domain as a potential alternative for tissue HER2 status in metastatic gastric cancer patients

AIM

We investigated whether serum concentrations of the HER2 extracellular domain (ECD) can be used as an alternative to test tissue HER2 status in metastatic gastric cancer.

MATERIALS & METHODS

A total of 133 cases of metastatic gastric cancer were included in present study. Serum HER2 ECD was measured by chemiluminescence immunoassay (CLIA). Receiver operating characteristic curve analysis was used to determine optimal serum HER2 ECD concentrations for differentiation between positive and negative HER2 status.

RESULTS

The median level of serum HER2 ECD was 9.6 ng/ml in metastatic gastric cancer patients. There was a significant relationship between serum and tissue levels of HER2 protein (p < 0.001). Area under the curve for serum HER2 ECD was 0.771 (95% CI: 0.682-0.860).

CONCLUSION

Levels of serum HER2 ECD are highly correlated with tissue HER2 status in metastatic gastric cancer. Serum HER2 ECD assay can be considered as a potential alternative for tissue HER2 status.

Targeting Notch signaling by γ-secretase inhibitor I enhances the cytotoxic effect of 5-FU in gastric cancer

Current medication for gastric cancer patients has a low success rate and the patients develop rapid tolerance to these drugs. Therefore, the development of new regimens is desired. In this study, we determined that Notch-signaling-related genes were overexpressed and activated in gastric cancer patients and gastric cancer cell lines. According to recent studies, γ-secretase inhibitors (GSIs), which function as Notch signaling inhibitors, could be used as therapeutic drugs in cancer. We demonstrated that GSI I (cbz-IL-CHO) is the most effective GSI in gastric cancer cells. We also determined the cell survival signaling-related proteins that were affected by GSI I. The levels of phosphorylated AKT were significantly decreased upon GSI I treatment, and constitutively activated myristoylated AKT completely blocked GSI I-induced apoptosis and cell survival, suggesting that inhibition of AKT signaling is critical for GSI I-mediated effects in gastric cancer cells. In order to maximize the effects and safety of GSI I, a combination treatment with GSI I and 5-FU was performed. Inhibition of gastric cancer cell proliferation with the combination treatment was significantly better than that with the single treatment. All phosphorylated forms of AKT, p44/42, JNK, and p38 were drastically changed by the combination treatment. Orthotopically transplanted gastric tumor burdens in mice were reduced using the combined treatment. The outcomes of this study clearly demonstrated the therapeutic potential of GSI I in gastric cancer, as well as the greater efficacy of the combined treatment of GSI I with 5-FU. Therefore, we suggest that further clinical trials examining the potential of combined GSI I and 5-FU treatment in gastric cancer patients be undertaken.

Essential role of Her3 in two signaling transduction patterns: Her2/Her3 and MET/Her3 in proliferation of human gastric cancer

Various receptor tyrosine kinase (RTK) pathways were verified in many cancers including gastric cancer (GC), We sought to investigate the expression of RTKs including Her2, Her3, and Met and their transduction patterns in human GC. Over-expression of Her2, Her3, and c-Met in human GC was verified by immunohistochemistry leading to constitutive activation of RTK signaling pathways. Combined RTKs expression was valuable indicators for poor prognosis of GC patients. Using ErbB2 specific inhibitor Lapatinib and c-Met specific inhibitor PHA-665752, we further demonstrated that this constitutive activation of RTK signaling is necessary for the survival of GC cells. However, various RTK pattern: Her3/Her2 and Met/Her3 were verified in the transduction growth stimulus from outside via both AKT and MAPK signaling. Moreover, the essential roles of Her3 in both two heterodimers were obtained which showed significantly attenuated growth effect due to Her3 knockdown both in vitro and in vivo. In conclusion, various molecular transduction patterns: Her2/Her3 and Met/Her3 were verified in human GC, and Her3 could serve as a potential target in GC treatment.

Clinical management of advanced gastric cancer: the role of new molecular drugs

Gastric cancer is the fourth most common malignant neoplasm and the second leading cause of death for cancer in Western countries with more than 20000 new cases yearly diagnosed in the United States. Surgery represents the main approach for this disease but, notwithstanding the advances in surgical techniques, we observed a minimal improvement in terms of overall survival with a significant increasing of relapsing disease rates. Despite the development of new drugs has significantly improved the effectiveness of chemotherapy, the prognosis of patients with unresectable or metastatic gastric adenocarcinoma remains poor. Recently, several molecular target agents have been investigated; in particular, trastuzumab represents the first target molecule showing improvements in overall survival in human epithelial growth factor 2-positive gastric cancer patients. New molecules targeting vascular epithelial growth factor, mammalian target of rapamycin, and anti hepatocyte growth factor-c-Met pathway are also under investigation, with interesting results. Anyway, it seems necessary to select more accurately the population to treat with new agents by the identification of new biomarkers in order to optimize the results. In this paper we review the actual "scenario" of targeted treatments, also focusing on the new agents in development for gastric cancer and gastro-esophageal carcinoma, discussing their efficacy and potential applications in clinical practice.

The impact of Helicobacter pylori on EGF, EGF receptor, and the c-erb-B2 expression

PURPOSE

Increased expression of epidermal growth factor (EGF), its receptor (EGFR), and c-erb-B2 protein, which is homological with the EGF receptor, in gastric mucosa, may play a role in gastric carcinogenesis. We assessed if the infection and eradication of Helicobacter pylori (H. pylori) affects the gastric expression of growth factors and serum gastrin concentrations.

PATIENTS/METHODS

We examined immunohistochemically gastric EGF and both receptors' expression in: gastric cancer (GC; n=29), chronic gastritis with H. pylori infection (GHp+; n=40) before and after eradication and in patients without H. pylori infection (GHp-; n=42).

RESULTS

Before the eradication therapy, gastric mucosal EGF and both receptor's expressions in GHp+ patients were increased compared to GHp- (p<0.05), but were similar to GC. After eradication, EGF and the receptor's expression significantly decreased in the gastric body. Both EGFR and c-erb-B2 expression in the antrum were still higher than in GHp- (p<0.05), and remained comparable to GC.

CONCLUSIONS

In patients with H. pylori infection the gastric mucosal EGF, EGFR, and c-erb-B2 expressions are similar to those observed in gastric cancer. The persistence of the antral expression of receptors after eradication, at a level comparable to the gastric cancer group, suggests their eventual role in the progression of changes initiated by H. pylori toward carcinogenesis.

The role of HER3 in gastric cancer

Gastric cancer is the second leading cause of cancer mortality in the world. HER family tyrosine kinases play a critical role in the development of gastric cancer. The HER family of receptor tyrosine kinases includes EGF receptor (EGFR), HER2, HER3, and HER4. Targeted drugs antineoplastic therapies such as EGFR tyrosine kinase inhibitors have application with confrontation of gastric cancer. However, less attention has been paid to the oncogenic functions of HER3 essepecially in the gastric cancer due to its lack of intrinsic kinase activity. Recent work, however, has placed the role of HER3 in gastric cancer in the spotlight as a key signaling hub in several contexts. First, HER3 overexpression may be associated with poor prognosis and unfavorable survival mediated by PI3K/AKT signaling pathway. Second, a large amount of direct evidence has emerged the benefit of anti-HER3 agents in combination with EGFR tyrosine kinase inhibitors as well as anti-HER2 agents in gastric cancer. Furthermore, we can further elucidate the relationship between HER3 and MET inhibitors in gastric cancer that the development of resistance to MET inhibitors may result from the overexpression of HER3. This review focuses on the current achievements of the relationship between HER3 and gastric cancer in vivo and in vitro, the development of HER3 molecule-targeted therapy, additionally, the challenge which we will meet in the future.

CD44 expression denotes a subpopulation of gastric cancer cells in which Hedgehog signaling promotes chemotherapy resistance

PURPOSE

Gastric cancers may harbor a subset of cells with cancer stem cell (CSC) properties, including chemotherapy resistance, and CD44 is a gastric CSC marker. The Hedgehog (HH) pathway is a key developmental pathway that can be subverted by CSCs during tumorigenesis. Here, we examine the role of HH signaling in CD44(+) gastric cancer cells.

EXPERIMENTAL DESIGN

Gastric cancer cell lines, tumor xenografts, and patient tumors were examined.

RESULTS

Gastric cancer cell lines AGS, MKN-45, and NCI-N87 grown as spheroids or sorted for CD44(+) were found to have upregulation of HH pathway proteins. HH inhibition using Smoothened (Smo) shRNA or vismodegib (VIS) decreased spheroid formation and colony formation. CD44(+) cells, compared with unselected cells, were also resistant to 5-fluorouracil and cisplatin chemotherapy, and this resistance was reversed in vitro and in xenografts with Smo shRNA or VIS. CD44(+) cells also had significantly more migration, invasion, and anchorage-independent growth, and these properties could all be blocked with HH inhibition. Clinical tumor samples from a phase II trial of chemotherapy with or without VIS for advanced gastric cancer were analyzed for CD44 expression. In the chemotherapy alone group, high CD44 expression was associated with decreased survival, whereas in the chemotherapy plus VIS group, high CD44 expression was associated with improved survival.

CONCLUSIONS

HH signaling maintains CSC phenotypes and malignant transformation phenotypes in CD44(+) gastric cancer cells, and HH inhibition can reverse chemotherapy resistance in CD44(+) cells. Gastric cancer is a heterogeneous disease, and the strategy of combining chemotherapy with HH inhibition may only be effective in tumors with high CD44 levels.

Prognostic role of lemur tyrosine kinase 3 in postoperative gastric cancer

The treatment of gastric cancer has been unsatisfactory thus far; therefore, novel targets and treatment strategies are urgently required. Lemur tyrosine kinase (LMTK)3 is an estrogen receptor-α (ERα) modulator with a central role in endocrine resistance in breast cancer. Moreover, the expression and polymorphisms of LMTK3 are correlated with the prognosis of breast cancer patients. Since estrogen receptor (ER) is also expressed and plays a role in gastric cancer, we herein investigated the expression of the LMTK3 protein in 83 gastric cancer patients by tissue microarray and analyzed the correlation between LMTK3 expression and the prognosis of gastric cancer. Our results demonstrated that LMTK3 was more frequently expressed in gastric cancer tissues compared to non-cancerous mucosa (79.5 vs. 45.8%, respectively; P=0.000). The LMTK3 expression was significantly correlated with the depth of invasion (P=0.002) and disease stage (P=0.035). The Kaplan-Meier analysis revealed that the postoperative survival of the LMTK3-negative group was superior to that of the LMTK3-positive group (P=0.043). Moreover, the multivariate analysis identified LMTK3 expression as an independent prognostic factor for patients with gastric cancer (P=0.019). These findings suggested that the expression of LMTK3 may be a negative prognostic factor in patients with gastric cancer. Moreover, targeting LMTK3 is a potential strategy for the treatment of gastric cancer, although the biological functions of LMTK3 in gastric cancer require further investigation.

Expression of the EGF family in gastric cancer: downregulation of HER4 and its activating ligand NRG4

Gastric cancer is a major cause of cancer-related deaths in both men and women. The epidermal growth factor receptors are EGFR, HER2, HER3 and HER4. Of the four epidermal growth factor receptors, EGFR and HER2 are well-known oncogenes involved in gastric cancer. Little, however, is known about the role played by HER3 and HER4 in this disease. We obtained paired samples from the tumor and the adjacent normal tissue from the same patient undergoing surgery for gastric cancer. Using RT-qPCR, we quantified the mRNA expression of the four receptors including the HER4 splicing isoforms and all the ligands activating these receptors. Using immunohistochemistry, the protein expression of HER4 was also quantified. We found that HER2 mRNA expression was upregulated in the tumor tissue compared to the matched normal tissue (p = 0.0520). All ligands with affinity for EGFR were upregulated, whereas the expression of EGFR was unchanged. Interestingly, we found the mRNA expression of HER4 (p = 0.0002) and its ligand NRG4 (p = 0.0009) to be downregulated in the tumor tissue compared to the matched normal tissue. HER4 downregulation was demonstrated for all the alternatively spliced isoforms of this receptor. These results support the involvement of EGFR and HER2 in gastric cancer and suggest an interesting association of reduced HER4 expression with development of gastric cancer.

Her3 is associated with poor survival of gastric adenocarcinoma: Her3 promotes proliferation, survival and migration of human gastric cancer mediated by PI3K/AKT signaling pathway

ErbB3 (Her3) is a membrane-bound protein which can form heterodimers with other EGF receptor family members with kinase activity. Previous reports identified Her3 as a significant predictor of poor survival in human gastric cancer (GC), but its mechanism has remained unclear. We sought to investigate the mechanism of Her3 in GC and its association with clinical characteristics. Her3 was detected by both real-time PCR and immunohistochemistry (IHC) in 161 GC patients, and its related downstream signaling PI3K/AKT activity and clinical characteristics were accessed by statistical analysis. Her3 siRNA was used in both in vitro and in vivo assay to investigate the mechanism. Her3 expression was significantly increased in human GC compared with adjacent normal gastric tissues as observed by both real-time PCR and IHC. Her3 expression was associated with downstream AKT activation and increased tumor size, metastasis and poor survival in GC patients. Knockdown of Her3 in human GC cell line can inhibit cell proliferation and tumor growth both in vitro and in vivo by inactivation of AKT. Her3 knockdown had no observed impact on Her2 expression or activity. G2/M arrest was investigated due to decreased CyclinB1 and p27(kip1) at T157. Increased apoptosis occurred in Her3 silenced GC cell treated with cisplatin due to decreased BAD at S112. Moreover, Her3 silence can inhibit cell migration in vitro and metastasis in vivo by down-regulating MMPs via PI3K/AKT signaling. Her3 is a new prognostic factor associated with tumor growth and metastasis via PI3K/AKT signaling.

Fibroblast growth factor receptor 2: a therapeutic target in gastric cancer

Gastric cancer remains a leading cause of cancer-related death in the world. FGF receptor 2 (FGFR2) is preferentially amplified and overexpressed in the diffuse type of gastric cancer. This review evaluates the expression and function of FGFR2 in gastric cancer, and analyzes the use of its inhibitors for gastric cancer therapy. This review also discusses the limitations of FGFR2-based therapy, and envisages future developments toward the clinical applications of FGFR2.

Proliferin-related protein overexpression in SGC‑7901 gastric cancer cells inhibits in vitro cell growth and tumorigenesis in nude mice

As reported in the literature, the worldwide 5-year overall survival rate for patients with gastric cancer receiving surgical treatment in the progressive stage is less than 25%. Therefore, there is an urgent need for the development of novel therapeutic strategies. Our preliminary studies demonstrated that proliferin-related protein (PRP) inhibits the proliferation of TM3 Leydig testicular cells. To evaluate whether PRP has antitumor effects in vitro and in vivo, we stably expressed PRP in SGC-7901 gastric carcinoma cells. PRP inhibited the proliferation and cell cycle progression of SCG-7901 cells, as determined by cell growth and cell cycle assays. Transwell experiments demonstrated that PRP inhibited the cell migration and invasion of SCG-7901 cells. Western blotting demonstrated that PRP-overexpressing cells had upregulated matrix metalloproteinase 9 (MMP-9) and downregulated tissue inhibitor of metalloproteinases-1 (TIMP-1). In a xenograft tumor formation assay using nude mice, tumors formed by PRP-overexpressing cells had significantly lower weights than those formed by control cells, and the tumor inhibitory rate reached 71.9%. We demonstrated for the first time that PRP inhibits gastric carcinoma cell proliferation, motility, and tumorigenicity in vivo, suggesting that PRP may become an important target for the development of gastric cancer gene therapy.

Superior antitumor activity of nanoparticle albumin-bound paclitaxel in experimental gastric cancer

Gastric cancer is the second common cause of cancer related death worldwide and lacks highly effective treatment for advanced disease. Nab-paclitaxel is a novel microtubule-inhibitory cytotoxic agent that has not been tested in gastric cancer as of yet. In this study, human gastric cancer cell lines AGS, NCI-N87 and SNU16 were studied. Nab-paclitaxel inhibited cell proliferation with an IC50 of 5 nM in SNU16, 23 nM in AGS and 49 nM in NCI-N87 cells after 72-hour treatment, which was lower than that of oxaliplatin (1.05 μM to 1.51 μM) and epirubicin (0.12 μM to 0.25 μM). Nab-paclitaxel treatment increased expression of the mitotic-spindle associated phospho-stathmin irrespective of the baseline total or phosphorylated stathmin level, and induced mitotic cell death as confirmed through increased expression of cleaved-PARP and caspase-3. After a two-week nab-paclitaxel, oxaliplatin or epirubicin treatment, the average in vivo local tumor growth inhibition rate was 77, 17.2 and 21.4 percent, respectively (p = 0.002). Effects of therapy on tumoral proliferative and apoptotic indices corresponded with tumor growth inhibition data, while expression of phospho-stathmin also increased in tissues. There was an increase in median animal survival after nab-paclitaxel treatment (93 days) compared to controls (31 days, p = 0.0007), oxaliplatin (40 days, p = 0.0007) or to docetaxel therapy (81 days, p = 0.0416). The strong antitumor activity of nab-paclitaxel in experimental gastric cancer supports such microtubule-inhibitory strategy for clinical application. Nab-paclitaxel benefits were observed independent from phosphorylated stathmin expression at baseline, putting into question the consideration of nab-paclitaxel use in gastric cancer based on this putative biomarker.

Activation of abl family kinases in solid tumors

Although c-Abl and Arg non-receptor tyrosine kinases are well known for driving leukemia development, their role in solid tumors has not been appreciated until recently. Accumulating evidence now indicates that c-Abl and/or Arg are activated in some solid tumor cell lines via unique mechanisms that do not involve gene mutation/translocation, and c-Abl/Arg activation promotes matrix degradation, invasion, proliferation, tumorigenesis, and/or metastasis, depending on the tumor type. However, some data suggest that c-Abl also may suppress invasion, proliferation, and tumorigenesis in certain cell contexts. Thus, c-Abl/Arg may serve as molecular switches that suppress proliferation and invasion in response to some stimuli (e.g., ephrins) or when inactive/regulated, or as promote invasion and proliferation in response to other signals (e.g., activated growth factor receptors, loss of inhibitor expression), which induce sustained activation. Clearly, more data are required to determine the extent and prevalence of c-Abl/Arg activation in primary tumors and during progression, and additional animal studies are needed to substantiate in vitro findings. Furthermore, c-Abl/Arg inhibitors have been used in numerous solid tumor clinical trials; however, none of these trials were restricted to patients whose tumors expressed highly activated c-Abl/Arg (targeted trial). Targeted trials are critical for determining whether c-Abl/Arg inhibitors can be effective treatment options for patients whose tumors are driven by c-Abl/Arg.

Establishing a peritoneal dissemination xenograft mouse model for survival outcome assessment of experimental gastric cancer

BACKGROUND

Peritoneal dissemination of gastric cancer is a common reason for unresectability, a frequent recurrence mechanism, and a common cause for death. The present study was performed to test peritoneal dissemination gastric cancer xenografts mouse models that would support survival outcome analyses.

MATERIALS AND METHODS

Human gastric cancer cell lines AGS, NCI-N87, and SNU-16 were intraperitoneally injected into nude mice and severe combined immunodeficiency (SCID) mice. The peritoneal tumor formation and mouse survival were compared among different groups. Mice were treated with oxaliplatin (5 mg/kg) and NVP-BEZ235 (10 mg/kg).

RESULTS

The formation rate of peritoneal cancer after intraperitoneal injection of 5 × 10(6) SNU16, NCI-N87, and AGS cells was 2/8, 6/8, and 0/8 in nude mice, and 6/6, 6/6, and 0/6 in SCID mice, respectively. Median animal survival with peritoneal dissemination was 74 d for NCI-N87 cells (10 × 10(6)), 95 d for SNU16 cells (10 × 10(6)), 78 d for SNU16 cells (20 × 10(6)), and 44 d for SNU16 cells (40 × 10(6)). In a therapeutic experiment with 40 × 10(6) SNU16 cells, animal survival was significantly improved by oxaliplatin treatment compared with the control group (58.5 d versus 45 d, P < 0.001), but not by NVP-BEZ235 (48 d versus 45 d, P = 0.249) treatment. In the accompanying subcutaneous SNU16 mouse model, relative tumor volume compared with controls was not significantly decreased by oxaliplatin treatment (P = 0.151) but by NVP-BEZ235 therapy (P = 0.008).

CONCLUSIONS

Peritoneal gastric cancer xenografts were successfully established after intraperitoneal injection NCI-N87 and SNU16 cells. These findings provide a useful survival outcome assessment model for experimental gastric cancer research.

Advances in Targeting HER3 as an Anticancer Therapy

HER3 (ErbB3) is a unique member of the human epidermal growth factor receptor (EGFR) family (ErbB family). It functions only through dimerization with other members of the ErbB family and modulates activity and sensitivity to targeted cancer therapies. This paper briefly describes the mechanism of HER3 in signal transduction and its potential role in acquired resistance to EGFR- and HER2-targeted therapies. We also consider recent developments in HER3-targeting therapeutics and their combination with inhibitors of other ErbB members in clinical applications.

p21-activated kinases and gastrointestinal cancer

p21-activated kinases (PAKs) were initially identified as effector proteins downstream from GTPases of the Rho family. To date, six members of the PAK family have been discovered in mammalian cells. PAKs play important roles in growth factor signalling, cytoskeletal remodelling, gene transcription, cell proliferation and oncogenic transformation. A large body of research has demonstrated that PAKs are up-regulated in several human cancers, and that their overexpression is linked to tumour progression and resistance to therapy. Structural and biochemical studies have revealed the mechanisms involved in PAK signalling, and opened the way to the development of PAK-targeted therapies for cancer treatment. Here we summarise recent findings from biological and clinical research on the role of PAKs in gastrointestinal cancer, and discuss the current status of PAK-targeted anticancer therapies.

Brain-only metastatic breast cancer is a distinct clinical entity characterised by favourable median overall survival time and a high rate of long-term survivors

BACKGROUND

The clinical course of breast cancer patients with brain metastases (BM) as only metastatic site (brain-only metastatic breast cancer (BO-MBC)) has been insufficiently explored.

METHODS

All breast cancer patients with BM treated at our institution between 1990 and 2011 were identified. For each patient, full information on follow-up and administered therapies was mandatory for inclusion. Oestrogen receptor, progesterone receptor and Her2 status were determined according to standard protocols. Statistical analyses including computation of survival probabilities was performed.

RESULTS

In total, 222 female patients (26% luminal; 47% Her2; 27% triple negative) with BM of MBC were included in this study. In all, 38/222 (17%) BM patients did not develop extracranial metastases (ECM) during their disease course and were classified as BO-MBC. Brain-only-MBC was not associated with breast cancer subtype or number of BM. The median overall survival of BO-MBC patients was 11 months (range 0-69) and was significantly longer than in patients with BM and ECM (6 months, range 0-104; P=0.007). In all, 7/38 (18%) BO-MBC patients had long-term survival of >3 years after diagnosis of BM and long-term survival was significantly more common in BO-MBC patients as compared with BM patients with ECM (P<0.001).

CONCLUSIONS

Brain-only metastatic behaviour occurs in around 17% of breast cancer with BM and is not associated with breast cancer subtype. Exploitation of all multimodal treatment options is warranted in BO-MBC patients, as these patients have favourable prognosis and long-term survival is not uncommon.