Personalizing therapies for gastric cancer: Molecular mechanisms and novel targeted therapies

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.

Abnormal activation of RFC3, A YAP1/TEAD downstream target, promotes gastric cancer progression

BACKGROUND

Gastric cancer (GC) is a malignant tumor with a high mortality rate, and thus, it is necessary to explore molecular mechanisms underlying its progression. While replication factor C subunit 3 (RFC3) has been demonstrated to function as an oncogene in many cancers, its role in GC remains unclear.

METHODS

Tumor tissues were collected from clinical GC patients, and the expression of RFC3 was analyzed. NCI-N87 and HGC-27 cells were infected with lentivirus sh-RFC3 to knock down RFC3 expression. RFC3 expression levels were determined, in addition to cell biological behaviors both in vitro and in vivo. The relationship between RFC3 and the YAP1/TEAD signaling pathway was detected by dual luciferase reporter assay.

RESULTS

RFC3 was upregulated in GC tumor tissues. RFC3 knockdown inhibited cell proliferation, promoted cell apoptosis of GC cells, and suppressed cell migration and invasion. Moreover, depleted RFC3 suppressed tumor growth and metastasis in vivo. Mechanistically, the YAP1/TEAD axis activated RFC3 expression transcriptionally by binding to the RFC3 promoter.

CONCLUSIONS

RFC3 was transcriptional activated by the YAP1/TEAD signaling pathway, thus promoting GC progression. RFC3 may be a promising therapeutic target for GC.

Differential Long Non-Coding RNA Expression Analysis in Chronic Non-Atrophic Gastritis, Gastric Mucosal Intraepithelial Neoplasia, and Gastric Cancer Tissues

Gastric cancer (GC) has a high incidence worldwide, and when detected, the majority of patients have already progressed to advanced stages. Long non-coding RNAs (lncRNAs) have a wide range of biological functions and affect tumor occurrence and development. However, the potential role of lncRNAs in GC diagnosis remains unclear. We selected five high-quality samples from each group of chronic non-atrophic gastritis, gastric mucosal intraepithelial neoplasia, and GC tissues for analysis. RNA-seq was used to screen the differentially expressed lncRNAs, and we identified 666 differentially expressed lncRNAs between the chronic non-atrophic gastritis and GC groups, 13 differentially expressed lncRNAs between the gastric mucosal intraepithelial neoplasia and GC groups, and 507 differentially expressed lncRNAs between the chronic non-atrophic gastritis and gastric mucosal intraepithelial neoplasia groups. We also identified six lncRNAs (lncRNA H19, LINC00895, lnc-SRGAP2C-16, lnc-HLA-C-2, lnc-APOC1-1, and lnc-B3GALT2-1) which not only differentially expressed between the chronic non-atrophic gastritis and GC groups, but also differentially expressed between the gastric mucosal intraepithelial neoplasia and GC groups. Furthermore, RT-qPCR was used to verify the differentially co-expressed lncRNAs. LncSEA was used to conduct a functional analysis of differentially expressed lncRNAs. We also predicted the target mRNAs of the differentially expressed lncRNAs through bioinformatics analysis and analyzed targeting correlations between three differentially co-expressed lncRNAs and mRNAs (lncRNA H19, LINC00895, and lnc-SRGAP2C-16). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases were used to explore the functions of target mRNAs of differentially expressed lncRNAs. In conclusion, our study provides a novel perspective on the potential functions of differentially expressed lncRNAs in GC occurrence and development, indicating that the differentially expressed lncRNAs might be new biomarkers for early GC diagnosis.

CD133+/CD166+ human gastric adenocarcinoma cells present the properties of neoplastic stem cells and emerge more malignant features

AIMS

The recurrence and metastasis of gastric cancer has always been an important factor affecting the prognosis of gastric cancer. Cancer stem cells can promote the recurrence and growth of gastric cancer. The identification and isolation of gastric cancer stem cells contribute to the origin, progress and treatment strategy of gastric cancer. The aim of this study was to identify and isolate gastric cancer stem cells, and provide targets for the treatment of gastric cancer.

METHODS

Magnetic-activated cell sorting was used to isolate CD133+/CD166+ cell populations from human gastric adenocarcinoma cell lines (BGC-823 and SGC-7901). Sphere formation, cell proliferation, resistance to chemotherapy, colony formation, migration invasion and tumorigenicity in vivo of these cell populations were evaluated. Moreover, RT-qPCR and Western blot were used to investigate the expression level of the stem cell markers Nanog, Sox2, Oct-4, and c-Myc.

RESULTS

CD133+/CD166+ cell subpopulations presented more malignant features than CD133-/CD166-, CD133-/CD166+, CD133+/CD166- cell populations and parental cells. Moreover, the mRNA and protein expression level of Oct-4 and c-Myc were higher in CD133+/CD166+ cells than in parental cells or other cell populations.

CONCLUSION

The CD133+/CD166+ populations of human gastric cancer cell lines BGC-823 and SGC-7901 have cancer stem cell characteristics.

Role of Immunotherapy in Advanced Gastroesophageal Cancer

PURPOSE OF REVIEW

Immunotherapy and tumor microenvironment have been at the forefront of cancer research over the past several decades. Here, we will review the role of immunotherapy in advanced gastroesophageal cancers including targeted antibodies, immunomodulating agents, vaccines, oncolytic virus therapy, and adoptive immunotherapy, and discuss the future direction for immunotherapy in this population.

RECENT FINDINGS

Targeted antibodies are already standard-of-care. An anti-PD-1 monoclonal antibody is currently FDA approved for second-line treatment of locally advanced or metastatic ESCC, as well as beyond second-line treatment of advanced G/GEJ cancers, and recent data suggests it may be considered in first-line treatment of advanced G/GEJ cancers. Combination therapies such as immunotherapy plus chemotherapy and/or radiotherapy, vaccines, oncolytic viral therapy, and adoptive immunotherapy in varying combinations are currently under active investigation. Several trials are ongoing and are hoped to reach more efficacious and individualized treatment options in advanced gastroesophageal cancer, where novel treatment options are desperately needed.

Wireless Power Transfer Techniques for Implantable Medical Devices: A Review

Wireless power transfer (WPT) systems have become increasingly suitable solutions for the electrical powering of advanced multifunctional micro-electronic devices such as those found in current biomedical implants. The design and implementation of high power transfer efficiency WPT systems are, however, challenging. The size of the WPT system, the separation distance between the outside environment and location of the implanted medical device inside the body, the operating frequency and tissue safety due to power dissipation are key parameters to consider in the design of WPT systems. This article provides a systematic review of the wide range of WPT systems that have been investigated over the last two decades to improve overall system performance. The various strategies implemented to transfer wireless power in implantable medical devices (IMDs) were reviewed, which includes capacitive coupling, inductive coupling, magnetic resonance coupling and, more recently, acoustic and optical powering methods. The strengths and limitations of all these techniques are benchmarked against each other and particular emphasis is placed on comparing the implanted receiver size, the WPT distance, power transfer efficiency and tissue safety presented by the resulting systems. Necessary improvements and trends of each WPT techniques are also indicated per specific IMD.

Wireless Power Transfer for Implanted Medical Application: A Review

With ever-increasing concerns on health and environmental safety, there is a fast-growing interest in new technologies for medical devices and applications. Particularly, wireless power transfer (WPT) technology provides reliable and convenient power charging for implant medical devices without additional surgery. For those WPT medical systems, the width of the human body restricts the charging distance, while the specific absorption rate (SAR) standard limits the intensity of the electromagnetic field. In order to develop a high-efficient charging strategy for medical implants, the key factors of transmission distance, coil structure, resonant frequency, etc. are paid special attention. In this paper, a comprehensive overview of near-field WPT technologies in medical devices is presented and discussed. Also, future development is discussed for the prediction of different devices when embedded in various locations of the human body. Moreover, the key issues including power transfer efficiency and output power are addressed and analyzed. All concerning characteristics of WPT links for medical usage are elaborated and discussed. Thus, this review provides an in-depth investigation and the whole map for WPT technologies applied in medical applications.

Verteporfin targeting YAP1/TAZ-TEAD transcriptional activity inhibits the tumorigenic properties of gastric cancer stem cells

Gastric carcinomas (GC) are heterogeneous tumors, composed of a subpopulation of cluster of differentiation-44 (CD44)+ tumorigenic and chemoresistant cancer stem cells (CSC). YAP1 and TAZ oncoproteins (Y/T) interact with TEA domain family member 1 (TEAD) transcription factors to promote cell survival and proliferation in multiple tissues. Their activity and role in GC remain unclear. This work aimed to analyze Y/T-TEAD activity and molecular signature in gastric CSC, and to assess the effect of verteporfin, a Food and Drug Administration-approved drug preventing Y/T-TEAD interaction, on gastric CSC tumorigenic properties. Y/T-TEAD molecular signature was investigated using bioinformatical (KmPlot database), transcriptomic and immunostaining analyses in patient-derived GC and cell lines. Verteporfin effects on Y/T-TEAD transcriptional activity, CSC proliferation and tumorigenic properties were evaluated using in vitro tumorsphere assays and mouse models of patient-derived GC xenografts. High expressions of YAP1, TAZ, TEAD1, TEAD4 and their target genes were associated with low overall survival in nonmetastatic human GC patients (n = 444). This Y/T-TEAD molecular signature was enriched in CD44+ patient-derived GC cells and in cells resistant to conventional chemotherapy. Verteporfin treatment inhibited Y/T-TEAD transcriptional activity, cell proliferation and CD44 expression, and decreased the pool of tumorsphere-forming CD44⁺ /aldehyde dehydrogenase (ALDH)^high gastric CSC. Finally, verteporfin treatment inhibited GC tumor growth in vivo; the residual tumor cells exhibited reduced expressions of CD44 and ALDH1, and more importantly, they were unable to initiate new tumorspheres in vitro. All these data demonstrate that Y/T-TEAD activity controls gastric CSC tumorigenic properties. The repositioning of verteporfin targeting YAP1/TAZ-TEAD activity could be a promising CSC-based strategy for the treatment of GC.

Human epidermal growth factor receptor 2-, epidermal growth factor receptor-, and mesenchymal epithelial transition factor-positive sites of gastric cancer using surgical samples

BACKGROUND

Receptor tyrosine kinases (RTKs) play critical roles in gastric cancer (GC) progression and are potential targets for novel molecular-targeted agents or photo-immunotherapies. During patient selection, targeted biopsy is the first step. However, heterogeneous expression of RTKs based on the macroscopic appearance in GC has not been extensively addressed. Accordingly, in this study, we evaluated differences in RTK expression associated with macroscopic appearance in GC.

METHODS

In total, 375 consecutive patients who had undergone gastrectomy at the National Cancer Center Hospital East and who had histologically proven adenocarcinoma, available archived tumor sample, and no history of chemotherapy were enrolled in this study. For these cases, tissue microarray (TMA) samples were examined using immunohistochemistry (IHC). Based on the results of IHC, cases were selected for detailed examination. We re-evaluated IHC scores in more than three tumor blocks per case and comparatively evaluated differences in IHC expression in RTKs between the mucosal portion (MuP) and invasive portion (InP).

RESULTS

Human epidermal growth factor receptor 2 (HER2)-, epidermal growth factor receptor (EGFR)-, and mesenchymal epithelial transition factor (c-MET)-positive rates were 6, 9, and 20%, respectively. Twenty-two cases were then analyzed to assess differences in IHC expression levels in the same lesion. Concordance rates of positive staining of HER2, EGFR, and MET between MuP and whole tumor were 100, 40, and 56% and those with InP were 46, 100, and 56%.

CONCLUSIONS

To avoid underestimating expression status, biopsies must be taken from MuP for HER2, InP for EGFR, and both proportions for c-MET.

What Will We Expect From Novel Therapies to Esophageal and Gastric Malignancies?

Esophageal cancer and gastric cancer are aggressive diseases for which treatment approaches are facing a new era. Some molecular pathways, such as VEGF, EGFR, fibroblast growth factor receptor, PIK3CA, and PARP-1, have been studied, and novel targeted drugs are presumed to be developed in the near future. From The Cancer Genome Atlas report, 80% of Epstein-Barr virus tumors and 42% of tumors with microsatellite instability have PIK3CA mutations, suggesting that this pathway could be reevaluated as a possible target for new systemic treatment of gastric cancer. Notably, higher PARP-1 expression can be found in gastric cancer, which might be related to more advanced disease and worse prognosis. In addition, PD-L1 expression, high microsatellite instability, and mismatch repair deficiency can be found in gastric cancer, thus suggesting that immunotherapy may also play a role in those patients. We discuss trends related to the potential of novel therapies for patients with esophageal and gastric cancers in the near future.

Associations between CA19-9 and CA125 levels and human epidermal growth factor receptor 2 overexpression in patients with gastric cancer

The aim of the present study was to investigate the association between serum carbohydrate antigen (CA)19-9 and CA125 levels, and human epidermal growth factor receptor 2 (HER2) expression in patients with gastric cancer, as well as to identify any correlation between them and the risk of recurrence and metastasis. A total of 256 patients were enrolled in the present study, and 219 patients were followed-up to investigate recurrence and metastasis of gastric cancer. Immunohistochemistry was used to detect HER-2 in gastric adenocarcinoma and paracancerous tissues. The positive rate of CA19-9 and CA125 in stages III/IV was higher compared with that in stages I/II. The positive rate of HER2 in distinct stages of gastric cancer was not statistically different. Serum CA19-9 and CA125 were not associated with the positive expression of HER2. The recurrence and metastasis of CA19-9, CA125 and HER2-positive gastric cancer were increased compared with those experienced by CA19-9, CA125 and HER2-negative patients. Age, stage and preoperative tumor markers were associated with 3-year prognosis of gastric cancer. HER2 [odds ratio (OR)=2.55] and CA19-9 (OR=1.22) were independent prognostic factors in patients with gastric cancer. CA19-9, CA125 and HER2 may be used to predict the recurrence or metastasis of gastric cancer. The combined detection may be able to improve the sensitivity and efficiency of predicting the recurrence or metastasis of gastric cancer. Preoperative positive serum for CA19-9 and CA125 were associated with poor prognosis in patients with gastric cancer. CA19-9 and HER2 were independent prognostic factors of gastric cancer.

Gastric Cancer in Southern Europe: High-Risk Disease

Gastric cancer is an aggressive disease. Several risk factors are involved in gastric cancer pathogenesis, likely Helicobacter pylori (H. pylori) infection, genetic factors in hereditary syndromes, lifestyle, and diet. However, well-implemented screening strategies are lacking in most countries, including those in Southern Europe. Nevertheless, gastric cancer outcomes are better in some Southern European countries than in others, likely because of the incidence and distribution of different histologic types. Robotic surgery has been gaining favor as a treatment of early-stage disease, and the need for perioperative chemotherapy or adjuvant chemoradiotherapy (CRT) for locally advanced disease has been debated. In the metastatic setting, trastuzumab in combination with chemotherapy has helped to extend survival compared with chemotherapy alone for HER2-positive disease. This article will describe how gastric cancer is assessed and treated in Southern Europe in an attempt to correlate these approaches from a global perspective.

Characterization of Biomarkers of Tumorigenic and Chemoresistant Cancer Stem Cells in Human Gastric Carcinoma

Purpose: Gastric carcinomas are heterogeneous, and the current therapy remains essentially based on surgery with conventional chemotherapy and radiotherapy. This study aimed to characterize biomarkers allowing the detection of cancer stem cells (CSC) in human gastric carcinoma of different histologic types.Experimental Design: The primary tumors from 37 patients with intestinal- or diffuse-type noncardia gastric carcinoma were studied, and patient-derived tumor xenograft (PDX) models in immunodeficient mice were developed. The expressions of 10 putative cell surface markers of CSCs, as well as aldehyde dehydrogenase (ALDH) activity, were studied, and the tumorigenic properties of cells were evaluated by in vitro tumorsphere assays and in vivo xenografts by limiting dilution assays.Results: We found that a subpopulation of gastric carcinoma cells expressing EPCAM, CD133, CD166, CD44, and a high ALDH activity presented the properties to generate new heterogeneous tumorspheres in vitro and tumors in vivo CD44 and CD166 were coexpressed, representing 6.1% to 37.5% of the cells; ALDH activity was detected in 1.6% to 15.4% of the cells; and the ALDH⁺ cells represented a core within the CD44⁺/CD166⁺ subpopulation that contained the highest frequency of tumorigenic CSCs in vivo The ALDH⁺ cells possessed drug efflux properties and were more resistant to standard chemotherapy than the ALDH^- cells, a process that was partially reversed by verapamil treatment.Conclusions: CD44 and ALDH are the most specific biomarkers to detect and isolate tumorigenic and chemoresistant gastric CSCs in noncardia gastric carcinomas independently of the histologic classification of the tumor. Clin Cancer Res; 23(6); 1586-97. ©2016 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.

Current advances in targeted therapies for metastatic gastric cancer: improving patient care

In this article, we review the literature on the current advances in targeted therapies for metastatic gastric cancer aimed at improving patient care. We conclude that the key to guiding targeted therapy is individual biomarkers, which are not completely elucidated. HER2 overexpression is the only predictive biomarker currently in use. Furthermore, it is necessary to understand that gastric tumors are heterogeneous; therefore, is impossible to evaluate a novel biological compound without evaluating personal biomarkers. The selection of patients who are able to receive each treatment is paramount for improving advanced gastric cancer survival and reducing unnecessary costs.

Genomic and epigenomic heterogeneity in molecular subtypes of gastric cancer

Gastric cancer is a complex disease that is affected by multiple genetic and environmental factors. For the precise diagnosis and effective treatment of gastric cancer, the heterogeneity of the disease must be simplified; one way to achieve this is by dividing the disease into subgroups. Toward this effort, recent advances in high-throughput sequencing technology have revealed four molecular subtypes of gastric cancer, which are classified as Epstein-Barr virus-positive, microsatellite instability, genomically stable, and chromosomal instability subtypes. We anticipate that this molecular subtyping will help to extend our knowledge for basic research purposes and will be valuable for clinical use. Here, we review the genomic and epigenomic heterogeneity of the four molecular subtypes of gastric cancer. We also describe a mutational meta-analysis and a reanalysis of DNA methylation that were performed using previously reported gastric cancer datasets.

Correlation between apparent diffusion coefficients and HER2 status in gastric cancers: pilot study

Background

To evaluate whether apparent diffusion coefficient (ADC) value of gastric cancer obtained from diffusion weighted imaging (DWI) correlates with the HER2 status.

Methods

Forty-five patients, who had been diagnosed with gastric cancer through biopsy, were enrolled in this IRB-approved study. Each patient underwent a DWI (b values: 0 and 1,000 sec/mm²) prior to surgery (curative gastrectomy or palliative resection). Postoperative microscopic findings, HER2 status by immunohistochemical analysis and fluorescence in situ hybridization (FISH) were obtained. HER2 status was compared among gastric cancers with various histopathological features using the chi square test. The ADC values of gastric cancers with positive and negative HER2 were compared using the student t test.

Results

A weak yet significant correlation was observed between the mean ADC values and HER2 status (r = 0.312, P = 0.037) and scores (r = 0.419, P = 0.004). The mean ADC value of HER2-positive gastric cancers was significantly higher than those of HER2-negative tumors (1.211 vs. 0.984 mm²/s, P = 0.020). The minimal ADC value of HER2-positive gastric cancers was significantly higher than those of HER2-negative tumors (1.105 vs. 0.905 × 10⁻³ mm²/s, P = 0.036).

Conclusions

In this pilot study, we have demonstrated that the ADC values of gastric cancer correlate with the HER2 status. Future research is warranted to see if DWI can predict HER2 status and help in tailoring therapy for gastric cancer.

Clinicopathological significance of cytoplasmic transducer of ErbB2. 1 expression in gastric cancer

The aim of the present study was to investigate the expression of transducer of ErbB2. 1 (TOB1) in gastric carcinoma and to clarify the association between TOB1 expression and the clinical significance of this expression in patients with gastric carcinoma. Western blot analysis was performed to confirm the expression of TOB1 in gastric cancer. Immunohistochemistry (IHC) was performed on a tissue microarray containing 90 pairs of primary gastric cancer and adjacent normal tissue samples. TOB1 expression was evaluated separately with cytoplasmic and nuclear staining. Western blot analysis revealed significantly lower expression levels of TOB1 in gastric cancer tissues than those in adjacent normal tissues in 91.7% of cases. This was confirmed by IHC, which revealed decreased cytoplasmic TOB1 expression in cancer tissues compared with those of normal tissue samples in 84.4% of cases. The IHC data also revealed low cytoplasmic expression of TOB1 in 67.8% of human gastric cancer samples. Nuclear TOB1 expression exhibited no significant association with specific pathological features. However, a significant association was identified between cytoplasmic expression levels of TOB1 and clinicopathological characteristics, including the depth of invasion (P=0.017), differentiation grade (P=0.034) and tumor-node-metastasis stage (P<0.000). In conclusion, cytoplasmic TOB1 expression was suggested to be significant in angiogenesis and cell differentiation in gastric cancer tissues and may be used as a potential prognostic marker.

Multimodality management of resectable gastric cancer: A review

Adenocarcinoma of the stomach carries a poor prognosis and is the second most common cause of cancer death worldwide. It is recommended that surgical resection with a D1 or a modified D2 gastrectomy (with at least 15 lymph nodes removed for examination) be performed in the United States, though D2 lymphadenectomies should be performed at experienced centers. A D2 lymphadenectomy is the recommended procedure in Asia. Although surgical resection is considered the definitive treatment, rates of recurrences are high, necessitating the need for neoadjuvant or adjuvant therapy. This review article aims to outline and summarize some of the pivotal trials that have defined optimal treatment options for non-metastatic non-cardia gastric cancer. Some of the most notable trials include the INT-0116 trial, which established a benefit in concurrent chemoradiation and adjuvant chemotherapy. This was again confirmed in the ARTIST trial, especially in patients with nodal involvement. Later, the Medical Research Council Adjuvant Gastric Infusional Chemotherapy trial provided evidence for the use of perioperative chemotherapy. Targeted agents such as ramucirumab and trastuzumab are also being investigated for use in locally advanced gastric cancers after demonstrating a benefit in the metastatic setting. Given the poor response rate of this difficult disease to various treatment modalities, numerous studies are currently ongoing in an attempt to define a more effective therapy, some of which are briefly introduced in this review as well.

Molecular targeting to treat gastric cancer

Trastuzumab that targets human epidermal growth factor receptor 2 (HER2) protein is the only approved molecular targeting agent for treating gastric cancer in Japan and the outcomes have been favorable. However, trastuzumab is effective for only 10% to 20% of the population with gastric cancer that expresses HER2 protein. Molecular targeting therapy with bevacizumab against vascular endothelial growth factors (VEGF) and with cetuximab and panitumumab against the epidermal growth factors pathway that have been approved for treating colorectal cancer are not considered effective for treating gastric cancer according to several clinical trials. However, ramucirumab that targets VEGF receptor-2 prolonged overall survival in a large phase III clinical trial and it might be an effective molecular targeting therapy for gastric cancer. The significance of molecular targeting therapy for gastric cancer remains controversial. A large-scale randomized clinical trial of novel molecular targeting agents with which to treat gastric cancer is needed.

Application of wireless power transmission systems in wireless capsule endoscopy: an overview

Wireless capsule endoscopy (WCE) is a promising technology for direct diagnosis of the entire small bowel to detect lethal diseases, including cancer and obscure gastrointestinal bleeding (OGIB). To improve the quality of diagnosis, some vital specifications of WCE such as image resolution, frame rate and working time need to be improved. Additionally, future multi-functioning robotic capsule endoscopy (RCE) units may utilize advanced features such as active system control over capsule motion, drug delivery systems, semi-surgical tools and biopsy. However, the inclusion of the above advanced features demands additional power that make conventional power source methods impractical. In this regards, wireless power transmission (WPT) system has received attention among researchers to overcome this problem. Systematic reviews on techniques of using WPT for WCE are limited, especially when involving the recent technological advancements. This paper aims to fill that gap by providing a systematic review with emphasis on the aspects related to the amount of transmitted power, the power transmission efficiency, the system stability and patient safety. It is noted that, thus far the development of WPT system for this WCE application is still in initial stage and there is room for improvements, especially involving system efficiency, stability, and the patient safety aspects.