Targeted therapies for gastric cancer: current status

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.

Noninvasive Evaluation of EGFR Expression of Digestive Tumors Using 99mTc-MAG3-Cet-F(ab ′ )2-Based SPECT/CT Imaging

Purpose. This study is aimed at investigating the feasibility of cetuximab (Cet) F(ab ${}^{\prime }$ )2 fragment- (Cet-F(ab ${}^{\prime }$ )2-) based single photon emission tomography/computed tomography (SPECT/CT) for assessing the epidermal growth factor receptor (EGFR) expression in digestive tumor mouse models. Methods. Cet-F(ab ${}^{\prime }$ )2 was synthesized using immunoglobulin G-degrading enzyme of Streptococcus pyogenes (IdeS) protease and purified with protein A beads. The product and its in vitro stability in normal saline and 1% bovine serum albumin were analyzed with sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The EGFR expression in the human colon tumor cell line HT29 and the human stomach tumor cell line MGC803 were verified using western blotting and immunocytochemistry. Cet-F(ab ${}^{\prime }$ )2 was conjugated with 5(6)-carboxytetramethylrhodamine succinimidyl ester to demonstrate its binding ability to the MGC803 and HT29 cells. Cet-F(ab ${}^{\prime }$ )2 was conjugated with NHS-MAG3 for 99mTc radiolabeling. The best imaging time was determined using a biodistribution assay at 1, 4, 16, and 24 h after injection of the 99mTc-MAG3-Cet-F(ab ${}^{\prime }$ )2 tracer. Furthermore, 99mTc-MAG3-Cet-F(ab ${}^{\prime }$ )2 SPECT/CT was performed on MGC803 and HT29 tumor-bearing nude mice. Results. HT29 cells had low EGFR expression while MGC803 cell exhibited the high EGFR expression. Cet-F(ab ${}^{\prime }$ )2 and intact cetuximab showed similar high binding ability to MGC803 cells but not to HT29 cells. Cet-F(ab ${}^{\prime }$ )2 and 99mTc-MAG3-Cet-F(ab ${}^{\prime }$ )2 showed excellent in vitro stability. The biodistribution assay showed that the target to nontarget ratio was the highest at 16 h ( $17.29\pm 5.72$ , $n=4$ ) after tracer injection. The 99mTc-MAG3-Cet-F(ab ${}^{\prime }$ )2-based SPECT/CT imaging revealed rapid and sustained tracer uptake in MGC803 tumors rather than in HT29 tumors with high image contrast, which was consistent with the results in vitro. Conclusion. SPECT/CT imaging using 99mTc-MAG3-Cet-F(ab ${}^{\prime }$ )2 enables the evaluation of the EGFR expression in murine EGFR-positive tumors, indicating the potential utility for noninvasive evaluation of the EGFR expression in tumors.

Long Noncoding RNAs: New Regulators of Resistance to Systemic Therapies for Gastric Cancer

Gastric cancer (GC) is the second leading cause of cancer mortality and the fourth most commonly diagnosed malignant disease, with approximately 951,000 new cases diagnosed and approximately 723,000 cases of mortality each year. The highest mortality rate of GC is in East Asia, and the lowest is in North America. A large number of studies have demonstrated that GC patients are characterized by higher morbidity, metastasis rates, and mortality and lower early diagnosis rates, radical resection rates, and 5-year survival rates. All cases of GC can be divided into two important stages, namely, early- and advanced-stage GC, and the stage mainly determines the treatment strategy for and the therapeutic effect in GC patients. Patients with early-stage GC undergo radical surgery followed by chemotherapy, and the 5-year survival rate can be as high as 90%. However, patients with advanced-stage GC cannot undergo radical surgery because they are at risk for metastasis; therefore, they can choose only radiotherapy or chemotherapy and have a poor prognosis. Based on the lack of specific clinical manifestations and detection methods, most GC patients (>70%) are diagnosed in the advanced stage; therefore, continued efforts toward developing treatments have been focused on advanced-stage GC patients and include molecular targeted therapy, immunotherapy, and small molecular therapy. Nevertheless, in recent years, accumulating evidence has indicated that small molecules, especially long noncoding RNAs (lncRNAs), are involved in the occurrence, development, and progression of GC, and their abundantly dysregulated expression has been identified in GC tissues and cell lines. Therefore, lncRNAs are considered easily detectable molecules and ideal biomarkers or target-specific agents for the future diagnosis or treatment of GC. In this review, we primarily discuss the status of GC, the role of lncRNAs in GC, and the emerging systemic treatments for GC.

Induction of apoptosis and G1 phase cell cycle arrest by Aster incisus in AGS gastric adenocarcinoma cells

In recent decades, various bioactive compounds from plants have been investigated for their potential use in the treatment of diseases in humans. Aster incisus extract (AIE) is the extract of a common plant that is mostly found in Asia. It has traditionally been used for medicinal purposes in South Korea. In this study, we evaluated the potential anticancer effects of a methanolic extract of Aster incisus in a normal human cell line (HaCaT keratinocytes) and in 4 different types of human cancer cell lines (A549, lung cancer; Hep3B, liver cancer; MDA‑MB‑231, breast cancer; and AGS, gastric cancer). The HaCaT, A549, Hep3B, MDA‑MB‑231 and AGS cells were treated with various concentrations of AIE and following treatment, cell survival was evaluated. Additional analyses, such as WST-1 assay, western blot analysis, DAPI staining, flow cytometry, immunofluorescence staining and wound healing assay were performed to elucidate the mechanisms and pathways involved in the cell death induced by AIE. Treatment with AIE induced morphological changes and considerably reduced the viability of the both normal and cancer cell lines. Further analysis of the AGS gastric cancer cells revealed that AIE led to the induction of apoptosis and a high accumulation of cells in the G1 cell phase following treatment with AIE in a dose-dependent manner. The results also revealed that AIE successfully suppressed the migration of the AIE-treated AGS cells. The results of western blot analysis indicated that AIE increased the expression of pro-apoptotic proteins, particularly Bid, Bad, Bak, cytochrome c, apoptosis inducing factor (AIF), cleaved caspase‑3, -8 and -9 and cleaved poly(ADP-ribose) polymerase (PARP). Additionally, AIE decreased the expression of the anti-apoptotic proteins, Bcl-2 and Bcl-xL. On the whole, the findings of this study demonstrate that AIE induces apoptosis through the activation of the caspase‑dependent pathway mediated by the mitochondrial pathway and by arresting the cell cycle in AGS cells.

Microsatellite Alterations and Protein Expression of 5 Major Tumor Suppressor Genes in Gastric Adenocarcinomas

PURPOSE: In gastric adenocarcinoma (GC), the major tumor suppressor genes (TSGs) such as p16, PTEN, Rb, E-cadherin, and p53, may play important roles in various regulatory pathways and in tumor suppression. This study evaluated the loss of heterozygosity (LOH) of microsatellite and protein expression of 5 TSGs and the results were examined for their correlation with clinicopathological factors. METHODS: LOH analysis was carried out using polymerase chain reactions with 15 polymorphic microsatellite markers of 5 chromosomes containing TSGs in 100 surgically resected tumors. Protein expression was evaluated by immunohistochemistry (IHC). RESULTS: LOH was detected in 83% of GCs. LOH of 9p21, 10q23, 13q14, 16q22, and 17p13 were detected in 26%, 31%, 24%, 22%, and 35% of cases, respectively. Protein expression of p16, PTEN, Rb, E-cadherin, and p53 were found to be 31%, 39%, 28%, 32%, and 46% of cases. Advanced GCs showed significantly higher rates of 17p13 LOH and p53 expression. 9p21 LOH and E-cadherin IHC were correlated with higher tumor grade. Lymph node metastasis was correlated with the LOH of 9p21, 16q22, and 17p13 and IHC of the Rb and p53. A higher stage was correlated with 10q23 and 17p13 in LOH and p53 for IHC. CONCLUSION: These results suggest that LOH and protein expression of various TSGs are important in carcinogenesis and tumor invasion. Additionally, LOH and IHC may be useful clinical indicators for determining the prognosis of patients with GCs. In particular, the 17p13 LOH and p53 for IHC can be applied as simple evaluations in the clinic.

Mebendazole, an antiparasitic drug, inhibits drug transporters expression in preclinical model of gastric peritoneal carcinomatosis

The present study aimed to investigate whether MBZ down-regulates drug transporter expression (ABCB1, ABCC1, SLC47A1). mRNA expression level of ABCB1, ABCC1 and SLC47A1 was evaluated by qPCR and protein expression levels MDR-1 was performed by western blotting in malignant ascites cells (AGP-01) treated with MBZ for 24h. The mRNA expression level of ABCB1 and ABCC1 significantly decreased at a 1.0μM of MBZ compared to negative control, while SLC47A1 extremely decreased at all tested concentrations of MBZ. Protein expression levels MDR-1 significantly decreased at a 1.0μM of MBZ compared to negative control. Therefore, our results showed MBZ may play an important role in inhibiting MDR gene expression in malignant ascites cells.

New bioactive peptide reduces the toxicity of chemotherapy drugs and increases drug sensitivity

Anticancer bioactive peptide (ACBP) is extracted from normal goat spleens and exhibits antitumor activity alone and in combination with low cisplatin doses to achieve antitumor efficacy similar to higher cisplatin doses via sustained medication modes. In the present study, we investigated whether elevated levels of induced or normal ACBP in MKN‑45 gastric cancer (GC) cells may reduce their toxicity to oxaliplatin (L‑OHP) in a dose‑dependent manner. The growth inhibition rate (IR), morphological changes and gene expression were examined in MKN‑45 GC cells. Compared with normal ACBP, induced ACBP alone significantly enhanced the anticancer activity of L‑OHP‑mediated apoptosis and reduced the amount and side‑effects of L‑OHP (P<0.05). The inhibition of cancer cell growth at high concentrations of induced ACBP and L‑OHP was significantly more effective than at low concentrations. In addition, for the first time, we examined the potential of a combination of induced ACBP and L‑OHP to increase L‑OHP sensitivity in human gastric carcinoma xenograft tumors. Nude mice were implanted with human gastric carcinoma MKN‑45 cells and treated with an intraperitoneal injection of 0.5 ml of normal saline, 30 µg/ml ACBP, 20 µg/ml L‑OHP or 30 µg/ml ACBP + 20 µg/ml L‑OHP [combination of anticancer bioactive peptide and oxaliplatin (A+L)] via the tail vein twice a week. In vivo short‑term intermittent use of induced ACBP alone significantly inhibited MKN‑45 tumor growth. The combination of induced ACBP and L‑OHP also significantly improved the quality of life of the nude mice and reduced the toxicity of L‑OHP. Based on flow cytometry and gene expression analyses, A+L significantly increased the proportion of cells in the G2/M phase (P<0.05) relative to ACBP or L‑OHP alone, and short‑term intraperitoneal injection of ACBP increased the sensitizing effect of L‑OHP. Collectively, these results suggest that high levels of induced ACBP in combination with L‑OHP via a short‑term intermittent medication mode could be a useful clinical therapeutic strategy for GC.

Expression of pRb, Ki67 and HER 2/neu in gastric carcinomas: Relation to different histopathological grades and stages

Gastric carcinoma is one of the aggressive malignancies with poor prognosis. The expression of pRb, Ki67, Her-2 in relation to tumor grade and stage in gastric carcinoma still needs more exploration. This study was performed aiming to study the immunohistochemical expression of altered retinoblastoma encoding protein (pRb), Ki67 and Her-2 in gastric carcinoma and to investigate their clinical and pathological significance. We studied tumor tissue specimens from 48 patients with gastric carcinoma. Paraffin sections were submitted for immunohistochemistry using pRb, Ki67 and Her-2. Statistical analysis was performed for clinical and pathological data of all studied cases. Altered pRb was expressed in 79% of the studied tumors, inversely correlated with tumor invasion and stage with no significant relation with tumor grade, age, and gender and tumor size. Ki67 LI was significantly associated with tumor grade and stage but not related to sex, age, tumor size, site, depth of invasion and lymph node metastasis. Her2 was expressed in 75% of studies tumors with significant association with tumor grade, the depth of invasion, lymph node metastasis and higher tumor stage. However, there was no significant association between Her-2 expression and gender, tumor site and size. In conclusion, altered pRb is frequently expressed in gastric carcinoma, inversely correlates with tumor invasion and tumor stage suggesting an early event in gastric carcinogenesis. Ki67 expression in gastric carcinoma is directly correlated with the tumor grade and depth of invasion. Her2 expression is significantly correlated with tumor grade, depth of invasion and stage.

Comparing the effects of endogenous and synthetic cannabinoid receptor agonists on survival of gastric cancer cells

AIMS

Anti-neoplastic activity induced by cannabinoids has been extensively documented for a number of cancer cell types; however, this topic has been explored in gastric cancer cells only in a limited number of approaches. Thus, the need of integrative and comparative studies still persists.

MATERIALS AND METHODS

In this study we tested and compared the effects of three different cannabinoid receptor agonists-anandamide (AEA), (R)-(+)-methanandamide (Meth-AEA) and CP 55,940 (CP)- on gastric cancer cell morphology, viability and death events in order to provide new insights to the use of these agents for therapeutic purposes.

KEY FINDINGS

The three agents tested exhibited similar concentration-dependent effects in the induction of changes in cell morphology and cell loss, as well as in the decrease of cell viability and DNA laddering in the human gastric adenocarcinoma cell line (AGS). Differences among the cannabinoids tested were mostly observed in the density of cells found in early and late apoptosis and necrosis, favoring AEA and CP as the more effective inducers of apoptotic mechanisms, and Meth-AEA as a more effective inducer of necrosis through transient and rapid apoptosis.

SIGNIFICANCE

Through a comparative approach, our results support and confirm the therapeutic potential that cannabinoid receptor agonists exert in gastric cancer cells and open possibilities to use cannabinoids as part of a new gastric cancer therapy.

The HER2 gene and HER2 protein status and chromosome 17 polysomy in gastric cancer cells in own material

BACKGROUND

The aims of the study were to assess the expression of HER2 protein, the amplification of the HER2 gene, and the occurrence of chromosome 17 polysomy in gastric cancer cells and to analyze the relation between the results of such a determination and the selected clinicopathologic parameters in patients treated for gastric cancer.

METHODS

Tissue samples of primary tumor from 83 consecutive patients who underwent gastric cancer resection were analyzed by immunohistochemical (IHC) analysis and fluorescence in situ hybridization (FISH).

RESULTS

A positive result of the IHC test, with a minimum score +, was obtained among 22.8% patients. The FISH test was carried out successfully among 58 patients, including 10.3% cases with a positive result, whereas the presence of chromosome 17 polysomy was confirmed among 13.8% patients. A statistically significant dependence was found between the presence of HER2 overexpression and: the lower stage of tumor infiltration, the higher grade of cancer differentiation, no mucinous component, and the intestinal type according to the Lauren classification. Statistically significant relation was found between chromosome 17 polysomy and the tumor location in the proximal part of the stomach, the performance of the palliative procedure, the presence of distant metastases, and a higher frequency of postoperative complications.

CONCLUSIONS

There is no complete coincidence in gastric cancer between the occurrence of the HER2 gene amplification and the HER2 receptor expression. The impact of the HER2 gene status and HER2 protein on prognosis in gastric cancer remains unclear. Chromosome 17 polysomy may be an important negative prognostic factor in gastric cancer.

Reciprocal expression of p-AMPKa and p-S6 is strongly associated with the prognosis of gastric cancer

Activation of AMP-activated protein kinase (AMPK) suppressed mammalian target of rapamycin (mTOR) pathway, resulting in impaired cancer cell proliferation. Two cohorts (50 and 1072 cases) of patients with resected gastric adenocarcinoma were enrolled in the study. Immunohistochemical staining for p-AMPKa, p-ACC, p-mTOR, p-S6, and p-4EBP1 was performed on the 50-patient cohort. Tissue microarray blocks containing samples from 1072 patients of Chinese ethnicity were used for the immunohistochemical detection of p-AMPKa and p-S6 levels. p-AMPK and p-ACC were frequently inactivated in both cohorts of gastric cancer samples, while p-mTOR, p-S6, and p-4EBP1 were frequently activated in the small cohort of gastric cancer. However, only levels of p-AMPKa and p-S6 were associated with the overall survival of gastric cancer patients. In the larger 1072-patient cohort, downregulation of p-AMPKa and upregulation of p-S6 were associated with tumor progression and were independent predictors of survival after resection of primary gastric cancer. Therefore, reciprocal expression of p-AMPKa and p-S6 may be promising prognostic biomarkers in patients with gastric cancer.

The anthelmintic drug mebendazole inhibits growth, migration and invasion in gastric cancer cell model

The present study aimed to investigate the effects of MBZ on a human malignant ascites cell line derived from a primary gastric cancer tumor. Our data reveal that MBZ showed high cytotoxicity in vitro, displaying an IC50 of 0.39 μM and 1.25 μM in ACP-02 and ACP-03, respectively. The association between MBZ and 5-FU increased slightly the cytotoxicity when compared to MBZ and 5-FU alone. Furthermore, MBZ disrupted the microtubule structure of AGP-01 cells and inhibited significantly the invasion and migration of these cells. Activity of active MMP-2 significantly decreased at all tested concentration of MBZ compared to negative control. These results support the indication of MBZ in combination with chemotherapeutic agents as a possible adjuvant therapy for the management/treatment of patients with advanced gastric cancer since MBZ is a drug of low cost with acceptable safety profile and reduced toxicity to normal cells. However, clinical trials must be performed in o to evaluate its efficacy in gastric cancer patients.

Cellular inhibitor of apoptosis protein 1 (cIAP1) stability contributes to YM155 resistance in human gastric cancer cells

YM155, which blocks the expression of survivin, a member of the inhibitor of apoptosis (IAP) family, induces cell death in a variety of cancer types, including prostate, bladder, breast, leukemia, and non-small lung cancer. However, the mechanism underlying gastric cancer susceptibility and resistance to YM155 is yet to be specified. Here, we demonstrate that cIAP1 stability dictates resistance to YM155 in human gastric cancer cells. Treatment of human gastric cancer cells with YM155 differentially induced cell death dependent on the stability of cIAP1 as well as survivin. Transfection with cIAP1 expression plasmids decreased cell sensitivity to YM155, whereas knockdown of endogenous cIAP1 using RNA interference enhanced sensitivity to YM155. In addition, double knockdown of survivin and cIAP1 significantly induced cell death in the YM155-resistant cell line, MKN45. We also showed that YM155 induced autoubiquitination and proteasome-dependent degradation of cIAP1. Surprisingly, survivin affected the stability of cIAP1 through binding, contributing to cell sensitivity to YM155. Thus, our findings reveal that YM155 sensitizes human gastric cancer cells to apoptotic cell death by degrading cIAP1, and furthermore, cIAP1 in gastric cancer cells may act as a PD marker for YM155 treatment.

Y-box binding protein 1 is correlated with lymph node metastasis in intestinal-type gastric cancer

AIMS

Y-box binding protein-1 (YB-1) is known to modulate gene transcription and protein translation, as well as cellular response to drug treatment. The aim of this study is to correlate YB-1 protein expression levels with clinicopathological parameters in intestinal-type gastric cancer tissue samples (as categorized by the Lauren classification) and substantiate the findings with in vitro experimentation.

METHODS AND RESULTS

Paraffin-embedded samples from 167 patients with intestinal-type gastric cancer were used for the construction of tissue microarrays (TMAs). TMA slides were immunostained and YB-1 immunoreactivity score was based on the weighted average intensity score. Univariate analysis revealed that YB-1 immunohistochemical expression was correlated significantly with lymph node status (P = 0.054, borderline significance) and perforation (P = 0.043). YB-1 expression was also found to be an independent predictor of lymph node spread by multivariate analysis. Furthermore, siRNA-mediated YB-1 gene knockdown in MKN7 gastric cancer cells (which is known to originate from an intestinal-type gastric cancer tissue) inhibited cell migration (P = 0.0002) and invasion in vitro (P = 0.0129) significantly.

CONCLUSION

YB-1 expression is associated with lymph node spread in intestinal-type gastric cancer and is a potential prognostic biomarker in this subtype of gastric cancer.

Evaluation of a novel functional single-nucleotide polymorphism (rs35010275 G>C) in MIR196A2 promoter region as a risk factor of gastric cancer in a Chinese population

Single-nucleotide polymorphisms (SNPs) in microRNAs (miRNAs) have been suggested to influence the occurrence and progression of cancer through altering the expression and biological function of miRNAs. The aim of this study was to investigate whether the potential functional SNPs in MIR196A2 promoter had effect on the susceptibility to gastric cancer (GC) in a Chinese population.We conducted a 2-stage case-control study (753 cases and 854 controls in testing set; 940 cases and 1061 controls in validation set) to evaluate the association between 2 potential functional SNPs in MIR196A2 promoter (rs12304647 A>C and rs35010275 G>C) and GC risk. The luciferase reporter assay and electrophoretic mobility shift assay were used to examine the functionality of the important polymorphism.We found that the rs35010275 C allele was significantly associated with the decreased risk of GC (adjusted odds ratio = 0.85, 95% confidence interval = 0.77-0.94) in the combined case-control studies. The miR-196a expression levels in GC tissues were significantly higher than that in corresponding adjacent normal tissues (P < 0.001). Besides, each allele of rs35010275 displayed completely opposite effects to influence the transcription activity of MIR196A2 promoter via recruiting different transcription factors or complexes.The functional rs35010275 G>C polymorphism in MIR196A2 promoter was significantly associated with miR-196a expression and influenced the genetic susceptibility to GC.

Pancreatic cancer

In recent years, it has become clear that the current standard therapeutic options for pancreatic cancer are not adequate and still do not meet the criteria to cure patients suffering from this lethal disease. Although research over the past decade has shown very interesting and promising new therapeutic options for these patients, only minor clinical success was achieved. Therefore, there is still an urgent need for new approaches that deal with early detection and new therapeutic options in pancreatic cancer. To provide optimal care for patients with pancreatic cancer, we need to understand better its complex molecular biology and thus to identify new target molecules that promote the proliferation and resistance to chemotherapy of pancreatic cancer cells. In spite of significant progress in curing cancers with chemotherapy, pancreatic cancer remains one of the most resistant solid tumour cancers and many studies suggest that drug-resistant cancer cells are the most aggressive with the highest relapse and metastatic rates. In this context, activated Notch signalling is strongly linked with chemoresistance and therefore reflects a rational new target to circumvent resistance to chemotherapy in pancreatic cancer. Here, we have focused our discussion on the latest research, current therapy options and recently identified target molecules such as Notch-2 and the heparin-binding growth factor midkine, which exhibit a wide range of cancer-relevant functions and therefore provide attractive new therapeutic target molecules, in terms of pancreatic cancer and other cancers also.

LINKED ARTICLES

This article is part of a themed section on Midkine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-4.

RAD51 potentiates synergistic effects of chemotherapy with PCI-24781 and cis-diamminedichloroplatinum on gastric cancer

AIM: To explore the efficacy of PCI-24781, a broad-spectrum, hydroxamic acid-derived histone deacetylase inhibitor, in the treatment of gastric cancer (GC).

METHODS: With or without treatment of PCI-24781 and/or cis-diamminedichloroplatinum (CDDP), GC cell lines were subjected to functional analysis, including cell growth, apoptosis and clonogenic assays. Chromatin immunoprecipitation and luciferase reporter assays were used to determine the interacting molecules and the activity of the enzyme. An in vivo study was carried out in GC xenograft mice. Cell culture-based assays were represented as mean ± SD. ANOVA tests were used to assess differences across groups. All pairwise comparisons between tumor weights among treatment groups were made using the Tukey-Kramer method for multiple comparison adjustment to control experimental-wise type I error rates. Significance was set at P < 0.05.

RESULTS: PCI-24781 significantly reduced the growth of the GC cells, enhanced cell apoptosis and suppressed clonogenicity, and these effects synergized with the effects of CDDP. PCI-24781 modulated the cell cycle and significantly reduced the expression of RAD51, which is related to homologous recombination. Depletion of RAD51 augmented the biological functions of PCI-24781, CDDP and the combination treatment, whereas overexpressing RAD51 had the opposite effects. Increased binding of the transcription suppressor E2F4 on the RAD51 promoter appeared to play a major role in these processes. Furthermore, significant suppression of tumor growth and weight in vivo was obtained following PCI-24781 treatment, which synergized with the anticancer effect of CDDP.

CONCLUSION: These data suggest that RAD51 potentiates the synergistic effects of chemotherapy with PCI-24781 and CDDP on GC.

LZTFL1 suppresses gastric cancer cell migration and invasion through regulating nuclear translocation of β-catenin

PURPOSE

Our previous work identified leucine zipper transcription factor-like 1 (LZTFL1) as a novel tumor suppressor gene, with its expression correlated with survival outcome in gastric cancer (GC) patients. This study focuses on the role of LZTFL1 in GC aggression and metastasis as well as its underlying molecular mechanisms.

METHOD

LZTFL1 immunohistochemical (IHC) staining on 311 paired normal/cancer tissue arrays were used to reconfirm the clinical significance of LZTFL1 expression. Transwell chamber assays were used to determine migration and invasive ability of GC cells. Gelatin zymography was employed to investigate the matrix metalloproteinases (MMPs) activity in tumor cells. Co-immunoprecipitation and Duolink in situ proximity ligation assay were used to analyze the interaction between LZTFL1 and β-catenin and the cellular localization of the interaction.

RESULT

IHC results indicated that patients with high LZTFL1 expression had a longer overall survival time (58 months, 95 % CI 28-128 months) than patients with low LZTFL1 expression (27 months, 95 % CI 23-35 months; p < 0.01). The expression level of LZTFL1 is associated with the degree of cell differentiation. LZTFL1 is necessary and sufficient to inhibit the expression of molecular markers associated with epithelial-mesenchymal transition (EMT) and cellular phenotypes associated with tumor cell EMT including the migration, invasion, and the expression and activities of MMPs of tumor cells. LZTFL1 binds β-catenin in the cytoplasm of the cell and inhibited its nuclear translocation.

CONCLUSION

LZTFL1 suppresses GC cell EMT by inhibiting β-catenin nuclear translocation. Re-expression of LZTFL1 in GC cells may be a potential therapeutic means to prevent GC metastasis.

Recent advances in oral anticancer agents for colon cancer

To provide therapeutic alternatives to intravenous colon chemotherapy major recent research is focusing on the development of oral chemotherapeutic agents with the intention to improve the quality of life of patients. Initially 5-fluorouracil was most commonly used for the treatment of colorectal cancer but currently oxaliplatin and irinotecan are also available. The majority of these new drugs are pyrimidines and their analogs. The rationale for using oral anticancer agents is discussed and new drugs, such as farnesyl protein transferase inhibitor S-1, rubitecan, ZD9331, MMI-166, eflornithine, sulindac, and oral camptothecin analogs, among others, are presented with the results of their preclinical and clinical developments. This article focuses on the advancement of clinical development and also discusses the relative merits and demerits of these agents. The accelerated approval of these agents by regulatory authorities is supported by survival benefit, response rate and time to progression.

Ten-year follow-up of a prospective trial for the targeted therapy of gastric cancer with the human monoclonal antibody PAT-SC1

The fully human monoclonal antibody PAT-SC1 is specific for an isoform of CD55 (decay-accelerating factor) designated CD55^PAT-SC1. This antigen is expressed in the majority (80%) of gastric cancers (GCs), and the antibody induces tumour cell-specific apoptosis in vitro as well as in vivo. PAT-SC1, therefore, has been deemed promising as a therapeutic agent. Here, we describe the results of an academic clinical study performed in a neoadjuvant setting with resectable GC patients. Patients undergoing treatment for GC between 1997 and 2001 were tested for CD55^PAT-SC1 expression. Fifty-one resectable patients that tested positively received a single administration of 20 mg PAT-SC1 48 h prior to surgery. They underwent standard surgery with either subtotal or total gastrectomy with bursectomy, omentectomy and a modified D2-lymphadenectomy, aimed at R0 resection. Primary endpoints of the present study were to evaluate side-effects of the PAT-SC1 antibody treatment and to evaluate histopathological effects such as tumour regression and induction of apoptosis. Long-term survival was a secondary endpoint. Administration of PAT-SC1 appeared safe with only reversible side-effects according to WHO grade I and II. Despite the low-dose of the antibody, 81.6% of the patients showed signs of increased apoptosis within the primary tumour and 60% showed signs of tumour cell regression. Comparison of the 10-year survival rates of the R0-resected CD55^PAT-SC1-positive patients treated with the PAT-SC1 antibody with a historical collective of R0-resected CD55^PAT-SC1-positive patients not treated with PAT-SC1 indicated a survival benefit in the treated patients. Furthermore, comparison of the patient survival of CD55^PAT-SC1-positive vs. CD55^PAT-SC1-negative groups suggested that CD55^PAT-SC1 antigen expression is an independent predictor of poor survival in a Cox regression analysis. Antibody PAT-SC1 may be a useful additive therapeutic agent in the treatment of patients with CD55^PAT-SC1-expressing GCs. In combination with radical standard surgery, PAT-SC1 given as an adjuvant or neoadjuvant immunotherapeutic agent induces apoptosis in tumour cells which may improve survival of these patients. Because of the human origin and its specific binding to the CD55^PAT-SC1 antigen, PAT-SC1 was well tolerated in this trial.

Therapeutic targets associated to E-cadherin dysfunction in gastric cancer

INTRODUCTION

Epithelial cadherin (E-cadherin) plays a key role in epithelial cell-cell adhesion, contributing to tissue differentiation and homeostasis. Throughout the past decades, research has shed light on the molecular mechanisms underlying E-cadherin's role in tumor progression, namely in invasion and metastization. Emerging evidence established E-cadherin as a tumor suppressor and suggests that targeting E-cadherin or downstream signaling molecules may constitute effective cancer therapeutics.

AREAS COVERED

This review aims to cover E-cadherin-mediated signaling during cancer development and progression and highlight putative therapeutic targets.

EXPERT OPINION

Reconstitution of E-cadherin expression or targeting of E-cadherin downstream molecules holds promise in cancer therapies. Considering the high frequency of CDH1 promoter hypermethylation as a second hit in malignant lesions from hereditary diffuse gastric cancer patients, histone deacetylase inhibitors are potential therapeutic agents in combination with conventional chemotherapy, specifically in initial tumor stages. Concerning E-cadherin-mediated signaling, we propose that HER receptors (as epidermal growth factor receptor) and Notch downstream targets are clinically relevant and should be considered in gastric cancer therapeutics and control.

Differential susceptibility of gastric cancer cells to TRAIL-induced apoptosis

Understanding the molecular basis of the differential sensitivity of cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis is required to predict therapeutic outcomes and to improve the effectiveness of TRAIL-based therapy. This study aimed to compare the responsiveness of gastric cancer cells to TRAIL treatment and to investigate the molecular basis of the differential TRAIL sensitivity of four gastric cancer cell lines. The TRAIL sensitivity of the four cell lines was ranked in the following order: SNU-16 ≈ SNU-620 > SNU-5 >> SNU-1. The level of Annexin V binding and the activation profile of caspase-3, -8 and -9 corroborated the differential TRAIL susceptibility of the cell lines. To determine the molecular basis of the differential sensitivity to TRAIL, we examined the expression of signaling components involved in TRAIL-mediated apoptosis. The mRNA level and surface expression of death receptor 4 (DR4) were significantly decreased in the SNU-1 cells compared to the other cell lines. Bid cleavage and X-linked inhibitor of apoptosis (XIAP) degradation were significantly increased in the SNU-16 and SNU-620 cells compared to the SNU-5 and SNU-1 cells, although Bid and XIAP were expressed at similar levels across the four cell lines. The expression and degradation of FLICE-inhibitory protein (FLIP) upon TRAIL treatment was independent of TRAIL sensitivity. In conclusion, the differential susceptibility of the four gastric cancer cells to TRAIL may be ascribed to the differential expression of DR4 and the proper augmentation of the death signal by the truncation of Bid and degradation of XIAP.

Nanovectorized radiotherapy: a new strategy to induce anti-tumor immunity

Recent experimental findings show that activation of the host immune system is required for the success of chemo- and radiotherapy. However, clinically apparent tumors have already developed multiple mechanisms to escape anti-tumor immunity. The fact that tumors are able to induce a state of tolerance and immunosuppression is a major obstacle in immunotherapy. Hence, there is an overwhelming need to develop new strategies that overcome this state of immune tolerance and induce an anti-tumor immune response both at primary and metastatic sites. Nanovectorized radiotherapy that combines ionizing radiation and nanodevices, is one strategy that could boost the quality and magnitude of an immune response in a predictable and designable fashion. The potential benefits of this emerging treatment may be based on the unique combination of immunostimulatory properties of nanoparticles with the ability of ionizing radiation to induce immunogenic tumor cell death. In this review, we will discuss available data and propose that the nanovectorized radiotherapy could be a powerful new strategy to induce anti-tumor immunity required for positive patient outcome.

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.

A conjugate of an anti-midkine single-chain variable fragment to doxorubicin inhibits tumor growth

Doxorubicin (DOX) was conjugated to a single-chain variable fragment (scFv) against human midkine (MK), and the conjugate (scFv-DOX) was used to target the chemotherapeutic agent to a mouse solid tumor model in which the tumor cells expressed high levels of human MK. The His-tagged recombinant scFv was expressed in bacteria, purified by metal affinity chromatography, and then conjugated to DOX using oxidative dextran (Dex) as a linker. The molecular formula of this immunoconjugate was scFv(Dex)_1.3(DOX)₂₀. In vitro apoptosis assays showed that the scFv-DOX conjugate was more cytotoxic against MK-transfected human adenocarcinoma cells (BGC823-MK) than untransfected cells (55.3 ± 2.4 vs 22.4 ± 3.8%) for three independent experiments. Nude mice bearing BGC823-MK solid tumors received scFv-DOX or equivalent doses of scFv + DOX for 2 weeks and tumor growth was more effectively inhibited by the scFv-DOX conjugate than by scFv + DOX (51.83% inhibition vs 40.81%). Histological analysis of the tumor tissues revealed that the highest levels of DOX accumulated in tumors from mice treated with scFv-DOX and this resulted in more extensive tumor cell death than in animals treated with the equivalent dose of scFv + DOX. These results show that the scFv-DOX conjugate effectively inhibited tumor growth in vivo and suggest that antigen-specific scFv may be competent drug-carriers.