New targeted therapies for 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.

The Hippo pathway as a drug target in gastric cancer

The Hippo tumor suppressor pathway is critical for balancing cellular differentiation and proliferation in response to cell-cell contact, mechanical signals and diffusible signals such as lysophosphatidic acid. Hippo pathway signaling is frequently dysregulated in gastric cancer (GC), as well as many other kinds of solid tumors, contributing to multiple aspects of malignant progression including unchecked cell division and metastasis. Considering the importance of this Hippo pathway in cancer, its pharmacological disruption may be of huge benefit in the fight against this disease. In this review, we summarize the components of the Hippo pathway, its crosstalk with other major oncogenic signaling pathways, common mechanisms of its dysregulation, as well as potential therapeutic approaches of targeting this pathway for cancer treatment, specifically in a GC context.

Establishment and Characterization of a Nude Mouse Model of Subcutaneously Implanted Tumors and Abdominal Metastasis in Gastric Cancer

A mouse gastric cancer model is an important tool for studying the mechanisms of gastric cancer. To establish subcutaneously implanted tumors, MKN-45 cell suspensions and tumor tissues were implanted into the middle of the right armpit of nude mice. To generate an abdominal metastasis model, MKN-45 cell suspensions and tumor tissue homogenates were implanted into the middle of the lower abdomen. We measured the weights of the nude mice and the longest dimension, shortest dimension, thickness, and volume of the tumor. We also analyzed the rate of tumor formation, the time required for tumor formation, and the number and size of abdominal tumors in the mice. The rates of formation of the subcutaneously implanted tumors were 100%, 0%, and 100% in the nude mice inoculated with 2 × 10⁷ cells/mL or 1 × 10⁷ cells/mL of the MKN-45 cell suspension or the tumor tissue homogenate (2 × 10⁷ cells/mL), respectively. The rates of metastatic abdominal tumor formation were 100%, 50%, and 75% in mice inoculated with 5 × 10⁷ cells/mL or 1 × 10⁷ cells/mL of the tumor tissue homogenate or the MKN-45 cell suspension (5 × 10⁷ cells/mL), respectively. We derived tumor tissues and tumor tissue homogenates from nude mice prior to establishing the subcutaneous model of implanted tumors and the abdominal metastasis model of gastric cancer, respectively.

Clinical Significance of MET Gene Copy Number in Patients with Curatively Resected Gastric Cancer

The present study analyzed the prognostic impact of MET gene copy number in patients with curatively resected gastric cancer who received a combination regimen of cisplatin and S-1. The MET gene copy number was analyzed by use of quantitative real-time polymerase chain reaction. From January 2006 to July 2010, 70 tumor samples from 74 patients enrolled in a pilot study were analyzed. According to a cutoff MET gene copy number of ≥2 copies, a high MET gene copy number was observed in 38 patients (54.3%). The characteristics of the 2 groups divided according to MET gene copy number were similar. With a median follow-up duration of 26.4 months (range, 2.6-73.2 months), the estimated 3-year relapse-free survival and overall survival rates were 54.3% and 77.4%, respectively. No significant association was observed between the MET gene copy number and survival in a multivariate analysis. The MET gene copy number investigated in this study was not found to be associated with prognosis in patients with curatively resected gastric cancer.

Patient-Derived Gastric Carcinoma Xenograft Mouse Models Faithfully Represent Human Tumor Molecular Diversity

Patient-derived cancer xenografts (PDCX) generally represent more reliable models of human disease in which to evaluate a potential drugs preclinical efficacy. However to date, only a few patient-derived gastric cancer xenograft (PDGCX) models have been reported. In this study, we aimed to establish additional PDGCX models and to evaluate whether these models accurately reflected the histological and genetic diversities of the corresponding patient tumors. By engrafting fresh patient gastric cancer (GC) tissues into immune-compromised mice (SCID and/or nude mice), thirty two PDGCX models were established. Histological features were assessed by a qualified pathologist based on H&E staining. Genomic comparison was performed for several biomarkers including ERBB1, ERBB2, ERBB3, FGFR2, MET and PTEN. These biomarkers were profiled to assess gene copy number by fluorescent in situ hybridization (FISH) and/or protein expression by immunohistochemistry (IHC). All 32 PDGCX models retained the histological features of the corresponding human tumors. Furthermore, among the 32 models, 78% (25/32) highly expressed ERBB1 (EGFR), 22% (7/32) were ERBB2 (HER2) positive, 78% (25/32) showed ERBB3 (HER3) high expression, 66% (21/32) lost PTEN expression, 3% (1/32) harbored FGFR2 amplification, 41% (13/32) were positive for MET expression and 16% (5/32) were MET gene amplified. Between the PDGCX models and their parental tumors, a high degree of similarity was observed for FGFR2 and MET gene amplification, and also for ERBB2 status (agreement rate = 94~100%; kappa value = 0.81~1). Protein expression of PTEN and MET also showed moderate agreement (agreement rate = 78%; kappa value = 0.46~0.56), while ERBB1 and ERBB3 expression showed slight agreement (agreement rate = 59~75%; kappa value = 0.18~0.19). ERBB2 positivity, FGFR2 or MET gene amplification was all maintained until passage 12 in mice. The stability of the molecular profiles observed across subsequent passages within the individual models provides confidence in the utility and translational significance of these models for in vivo testing of personalized therapies.

c-Met targeting in advanced gastric cancer: An open challenge

Despite significant improvements in systemic chemotherapy over the last two decades, the prognosis of patients with advanced gastric and gastroesophageal junction adenocarcinoma (GC) remains poor. Because of molecular heterogeneity, it is essential to classify tumors based on the underlying oncogenic pathways and to develop targeted therapies acting on individual tumors. High-quality research and advances in technology have contributed to the elucidation of molecular pathways underlying disease progression and have stimulated many clinical studies testing target therapies in an advanced disease setting. In particular, strong preclinical evidence for the aberrant activation of the HGF/c-Met signaling pathways in GC cancers exists. This review will cover the c-Met pathway, the mechanisms of c-Met activation and the different strategies of its inhibition. Next, we will focus on the current state of the art in the clinical evaluation of c-Met-targeted therapies and the description of ongoing randomized trials with the idea that in this disease, high quality translational research to identify and validate biomarkers is a priority task.

Expression profiling of receptor tyrosine kinases in high-grade neuroendocrine carcinoma of the lung: a comparative analysis with adenocarcinoma and squamous cell carcinoma

Background

As the comprehensive genomic analysis of small cell lung cancer (SCLC) progresses, novel treatments for this disease need to be explored. With attention to the direct connection between the receptor tyrosine kinases (RTKs) of tumor cells and the pharmacological effects of specific inhibitors, we systematically assessed the RTK expressions of high-grade neuroendocrine carcinomas of the lung [HGNECs, including SCLC and large cell neuroendocrine carcinoma (LCNEC)].

Patients and methods

Fifty-one LCNEC and 61 SCLC patients who underwent surgical resection were enrolled in this research. As a control group, 202 patients with adenocarcinomas (ADCs) and 122 patients with squamous cell carcinomas (SQCCs) were also analyzed. All the tumors were stained with antibodies for 10 RTKs: c-Kit, EGFR, IGF1R, KDR, ERBB2, FGFR1, c-Met, ALK, RET, and ROS1.

Results

The LCNEC and SCLC patients exhibited similar clinicopathological characteristics. The IHC scores for each RTK were almost equivalent between the LCNEC and SCLC groups, but they were significantly different from those of the ADC or SQCC groups. In particular, c-Kit was the only RTK that was remarkably expressed in both LCNECs and SCLCs. On the other hand, about 20 % of the HGNEC tumors exhibited strongly positive RTK expression, and this rate was similar to those for the ADC and SQCC tumors. Intriguingly, strongly positive RTKs were almost mutually exclusive in individual tumors.

Conclusions

Compared with ADC or SQCC, LCNEC and SCLC had similar expression profiles for the major RTKs. The exclusive c-Kit positivity observed among HGNECs suggests that c-Kit might be a distinctive RTK in HGNEC.

Electronic supplementary material

The online version of this article (doi:10.1007/s00432-015-1989-z) contains supplementary material, which is available to authorized users.

Circulating miR-18a in plasma contributes to cancer detection and monitoring in patients with gastric cancer

BACKGROUND

Recently, circulating microRNAs have been reported to be stably detectable in plasma/serum and to function as potent non-invasive biomarkers in various cancers. We hypothesized that miR-18a could contribute to a novel plasma biomarker in patients with gastric cancer (GC).

METHODS

We focused on miR-18a, which is a component of miR-17-92 cluster and has been reported as highly expressed in GC tissues. The study involved three steps: (1) confirmation of the higher miR-18a expression in primary GC tissues and GC cell lines than in normal gastric tissues and a fibroblast cell line; (2) evaluation of the plasma miR-18a assay using quantitative RT-PCR by comparing 104 GC patients and 65 healthy volunteers; (3) evaluation of monitoring tumor dynamics by the plasma miR-18a assay.

RESULTS

(1) The miR-18a expressions were significantly higher in GC tissues than in normal gastric tissues (P = 0.0286) and higher in all examined GC cell lines than in the fibroblast cell line. (2) The plasma miR-18a concentrations were significantly higher in GC patients than in healthy controls (P < 0.0001). The value of the area under the receiver-operating characteristic curve was 0.8059. (3) The plasma miR-18a levels were significantly reduced in postoperative samples compared to in preoperative samples (P = 0.0002). In an miR-18a overexpressing cell line, the miR-18a concentration of cultured medium increased in both cell number and time-course dependent manners, suggesting microRNA might be released from cancer cells into the surrounding environment.

CONCLUSIONS

Circulating miR-18a could be a useful biomarker for screening GC and monitoring tumor dynamics.

Th17 cell expansion in gastric cancer may contribute to cancer development and metastasis

Th0 cells differentiate into Th1 or Th2 depending on multiple transcription factors acting on specific time points to regulate gene expression. Th17 cells, a subset of IL-17-producing T cells distinct from Th1 or Th2 cells has been described as key players in inflammation and autoimmune diseases as well as cancer development. In the present study, 66 patients with gastric cancer were included; the expression level of Th1- and Th17-related IFN-γ, IL-17, T-bet, RORγt in gastric cancer tissues and peripheral blood mononuclear cell (PBMC) were detected, analyzed the relationship between Th17 or Th1 infiltration and metastasis and explored the possible mechanism. Our results showed that IL-17 and RORγt expression were significantly increased in gastric cancer tissues and PBMC, especially, in metastasis patients; plasma IL-17 also increased; furthermore, the mRNA and protein levels of IL-1β, IL-21 and TGF-β were up-regulated. All the data indicated that Th17 was infiltrated the cancer tissue; IL-1β, IL-21 and TGF-β were also involved in gastric cancer development by promoting Th17 cell generation. From the above data, we speculated that Th17 cell expansion in gastric cancer may contribute to cancer development and metastasis.

Targeting receptor tyrosine kinases in gastric cancer

Molecularly targeted therapeutic agents are constantly being developed and have been shown to be effective in various clinical trials. One group of representative targeted oncogenic kinases, the receptor tyrosine kinases (RTKs), has been associated with gastric cancer development. Trastuzumab, an inhibitor of ERBB2, has been approved for the treatment of gastric cancer, although other receptor tyrosine kinases, such as epidermal growth factor receptor, vascular endothelial growth factor, platelet-derived growth factor receptor, c-Met, IGF-1R and fibroblast growth factor receptor 2, are also activated in gastric cancer. The promising results of the trastuzumab clinical trial for gastric cancer resulted in the approval of trastuzumab-based therapy as a first-line treatment for human epidermal growth factor receptor 2-positive patients. On the other hand, the trial examining bevacizumab in combination with conventional chemotherapy did not meet its primary goal of increasing the overall survival time of gastric cancer patients; however, a significantly higher response rate and a longer progression-free survival were observed in the bevacizumab arm of the trial. Other clinical trials, especially phase III trials that have tested drugs targeting RTKs, such as cetuximab, panitumumab, gefitinib, erlotinib, figitumumab, sorafenib, sunitinib and lapatinib, have shown that these drugs have modest effects against gastric cancer. This review summarizes the recent results from the clinical trials of molecularly targeted drugs and suggests that further improvements in the treatment of advanced gastric cancer can be achieved through the combination of conventional drugs with the new molecularly targeted therapies.

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

Background:

Gastric cancer (GC) is a leading cause of cancer deaths worldwide. Since the approval of trastuzumab, targeted therapies are emerging as promising treatment options for the disease. This study aimed to explore the molecular segmentation of several known therapeutics targets, human epidermal growth factor receptor 2 (HER2), MET and fibroblast growth factor receptor 2 (FGFR2), within GC using clinically approved or investigational kits and scoring criteria. Knowledge of how these markers are segmented in the same cohort of GC patients could improve future clinical trial designs.

Methods:

Using immunohistochemistry (IHC) and FISH methods, overexpression and amplification of HER2, FGFR2 and MET were profiled in a cohort of Chinese GC samples. The correlations between anti-tumour sensitivity and the molecular segments of HER2, MET and FGFR2 alterations were further tested in a panel of GC cell lines and the patient-derived GC xenograft (PDGCX) model using the targeted inhibitors.

Results:

Of 172 GC patients, positivity for HER2, MET and FGFR2 alternations was found in 23 (13.4%), 21 (12.2%) and 9 (5.2%) patients, respectively. Positivity for MET was found in 3 of 23 HER2-positive GC patients. Co-positivity for FGFR2 and MET was found in 1 GC patient, and amplification of the two genes was found in different tumour cells. Our study in a panel of GC cell lines showed that in most cell lines, amplification or high expression of a particular molecular marker was mutually exclusive and in vitro sensitivity to the targeted agents lapatinib, PD173074 and crizotinib was only observed in cell lines with the corresponding high expression of the drugs' target protein. SGC031, an MET-positive PDGCX mouse model, responded to crizotinib but not to lapatinib or PD173074.

Conclusions:

Human epidermal growth factor receptor 2, MET and FGFR2 oncogenic driver alterations (gene amplification and overexpression) occur in three largely distinct molecular segments in GC. A significant proportion of HER2-negative patients may potentially benefit from MET- or FGFR2-targeted therapies.

Prognostic significance of MET amplification and expression in gastric cancer: a systematic review with meta-analysis

BACKGROUND AND AIMS

MET, the hepatocyte growth factor receptor, is a receptor tyrosine kinase overexpressed and activated in a subset of gastric cancer. Several studies investigated the relationship between MET amplification and expression with the clinical outcome in patients with gastric cancer, but yielded conflicting results. We performed a systematic review and meta-analysis to determine the influence of MET amplification and expression on prognosis in gastric cancer.

METHODS

MEDLINE and EMBASE were searched for studies that explored the association between MET amplification and expression with survival in patients with gastric cancer up to 1 April, 2013. Data of individual hazard ratios (HRs) and 95% confidence intervals (CIs) for meta-analyses were extracted from the publications and combined in pooled HRs.

RESULTS

Fourteen studies involving 2,258 patients with gastric cancer were included. It was suggested that MET overexpression had an unfavorable impact on survival of patients with gastric cancer, with HRs (95% CIs) of 2.57 (95% CI: 1.97-3.35) overall, 2.82 (95% CI: 1.86-4.27) among studies using amplification for measure scale of MET and 2.42 (95% CI: 1.66-3.54) for expression. The magnitude of association was reduced whereas remained statistically significant in high quality studies or in larger sample size studies and corresponding HRs were 2.18(1.76, 2.70) and 2.35(1.93, 2.87), respectively, without significant heterogeneity.

CONCLUSION

The findings from present study indicated that higher MET gene amplification and expression in gastric cancer was an indicator of poor prognosis.

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.

FOXO6 promotes gastric cancer cell tumorigenicity via upregulation of C-myc

The aberrant regulation of many related genes is involved in the development and progression of gastric carcinoma. In the present study, we show that mRNA and protein levels of FOXO6 are upregulated in gastric cancer tissues. Forced overexpression of FOXO6 promotes gastric cancer cell proliferation, while knockdown of FOXO6 expression inhibits proliferation. We show that ectopic FOXO6 expression induces the expression of C-myc. Furthermore, we found that FOXO6 physically interacts with the transcription factor hepatic nuclear factor 4 (HNF4) in gastric cancer cells. FOXO6 induces C-myc expression by associating to HNF4 and mediating histone acetylation, and the dissociation of HDAC3 from the promoter of the C-myc gene. Therefore, our results suggest a previously unknown FOXO6/HNF4/C-myc molecular network controlling gastric cancer development.

IL-26 promotes the proliferation and survival of human gastric cancer cells by regulating the balance of STAT1 and STAT3 activation

Interleukin-26 (IL-26) is one of the cytokines secreted by Th17 cells whose role in human tumors remains unknown. Here, we investigated the expression and potential role of IL-26 in human gastric cancer (GC). The expression of IL-26 and related molecules such as IL-20R1, STAT1 and STAT3 was examined by real-time PCR and immunohistochemisty. The effects of IL-26 on cell proliferation and cisplatin-induced apoptosis were analyzed by BrdU cooperation assay and PI-Annexin V co-staining, respectively. Lentiviral mediated siRNA was used to explore its mechanism of action, and IL-26 related signaling was analyzed by western blotting. Human GC tissues showed increased levels of IL-26 and its related molecules and activation of STAT3 signaling, whereas STAT1 activation did not differ significantly between GC and normal gastric tissues. Moreover, IL-26 was primarily produced by Th17 and NK cells. IL-26 promoted the proliferation and survival of MKN45 and SGC-7901 gastric cancer cells in a dose-dependent manner. Furthermore, IL-20R2 and IL-10R1, which are two essential receptors for IL-26 signaling, were expressed in both cell lines. IL-26 activated STAT1 and STAT3 signaling; however, the upregulation of the expression of Bcl-2, Bcl-xl and c-myc indicated that the effect of IL-26 is mediated by STAT3 activation. Knockdown of STAT1 and STAT3 expression suggested that the proliferative and anti-apoptotic effects of IL-26 are mediated by the modulation of STAT1/STAT3 activation. In summary, elevated levels of IL-26 in human GC promote proliferation and survival by modulating STAT1/STAT3 signaling.

Inhibitory effects of curcumin on gastric cancer cells: a proteomic study of molecular targets

Curcumin, a natural anticancer agent, has been shown to inhibit cell growth in a number of tumor cell lines and animal models. We examined the inhibition of curcumin on cell viability and its induction of apoptosis using different gastric cancer cell lines (BGC-823, MKN-45 and SCG-7901). 3-(4,5-dimethyl-thiazol-2-yl)-2-5-diphenyltetrazolium-bromide (MTT) assay showed that curcumin inhibited cell growth in a dose- (1, 5, 10 and 30 μM) and time- (24, 48, 72 and 96 h) dependent manner; analysis of Annexin V binding showed that curcumin induced apoptosis at the dose of 10 and 30 μM when the cells were treated for 24 and 48 h. As cancers are caused by dysregulation of various proteins, we investigated target proteins associated with curcumin by two-dimensional gel electrophoresis (2-DE) and MALDI-TOF-TOF mass spectrometer. BGC-823 cells were treated with 30 μM curcumin for 24 h and total protein was extracted for the 2-DE. In the first dimension of the 2-DE, protein samples (800 μg) were applied to immobilized pH gradient (IPG) strips (24 cm, pH 3-10, NL) and the isoelectric focusing (IEF) was performed using a step-wise voltage ramp; the second dimension was performed using 12.5% SDS-PAGE gel at 1 W constant power per gel. In total, 75 proteins showed significant changes over 1.5-fold in curcumin-treated cells compared to control cells (Student's t-test, p<0.05). Among them, 33 proteins were upregulated and 42 proteins downregulated by curcumin as determined by spot densitometry. 52 proteins with significant mascot scores were identified and implicated in cancer development and progression. Their biological function included cell proliferation, cycle and apoptosis (20%), metabolism (16%), nucleic acid processing (15%), cytoskeleton organization and movement (11%), signal transduction (11%), protein folding, proteolysis and translation (20%), and immune response (2%). Furthermore, protein-protein interacting analysis demonstrated the interaction networks affected by curcumin in gastric cancer cells. These data provide some clues for explaining the anticancer mechanisms of curcumin and explore more potent molecular targets of the drug expected to be helpful for the development of new drugs.

Frequent gene amplification predicts poor prognosis in gastric cancer

Gastric cancer is one of the most common malignancies worldwide. However, genetic alterations leading to this disease are largely unknown. Gene amplification is one of the most frequent genetic alterations, which is believed to play a major role in the development and progression of gastric cancer. In the present study, we identified three frequently amplified genes from 30 candidate genes using real-time quantitative PCR method, including ERBB4, C-MET and CD44, and further explored their association with clinicopathological characteristics and poor survival in a cohort of gastric cancers. Our data showed amplification of these genes was significantly associated with certain clinicopathological characteristics, particularly tumor differentiation and cancer-related death. More importantly, amplification of these genes was significantly related to worse survival, suggesting that these amplified genes may be significant predictors of poor prognosis and potential therapeutic targets in gastric cancer. Targeting these genes may thus provide new possibilities in the treatment of gastric cancer.