OB glue paste technique for establishing nude mouse human gastric cancer orthotopic transplantation models

Towards an optimal model for gastric cancer peritoneal metastasis: current challenges and future directions

Peritoneal metastasis is a challenging aspect of clinical practice for gastric cancer. Animal models are crucial in understanding molecular mechanisms, assessing drug efficacy, and conducting clinical intervention studies, including those related to gastric cancer peritoneal metastasis. Unlike other xenograft models, peritoneal metastasis models should not only present tumor growth at the transplant site, but also recapitulate tumor cell metastasis in the abdominal cavity. Developing a reliable model of gastric cancer peritoneal metastasis involves several technical aspects, such as the selection of model animals, source of xenograft tumors, technology of transplantation, and dynamic monitoring of the tumor progression. To date, challenges remain in developing a reliable model that can completely recapitulate peritoneal metastasis. Thus, this review aims to summarize the techniques and strategies used to establish animal models of gastric cancer peritoneal metastasis, providing a reference for future model establishment.

An orthotopic mouse model of gastric cancer invasion and metastasis

Gastric cancer is a leading cause of cancer death worldwide, with advanced stage being correlated to the level of tumour invasion and metastasis. Current research is heavily focused on the identification and development of efficacious therapeutics targeting these fundamental hallmarks of cancer, however there are currently no animal models that mimic the invasive phenotypes observed in humans. To address this we have developed an orthotopic mouse model whereby gastric cancer cell lines are tagged with luciferase and injected into the subserosal layer of the stomach. This allows for the monitoring of primary tumour growth and metastasis in real-time as well as quantitation of the degree of tumour invasion through the stomach wall by immunohistochemistry. We have three models based on the degree of invasion and metastasis that are cell line specific: The AGS cells develop into invasive tumours by 4-weeks with no evidence of metastases, MKN45 cells are moderately metastatic with minimal invasion till week 2 and MKN28 cells are highly metastatic and fully invasive by week 1. These models have utility as a tool for testing the efficacy of anti-tumour, anti-invasive and anti-metastatic therapies in the setting of gastric cancer, which currently has poor treatment options.

3-bromopyruvate and sodium citrate target glycolysis, suppress survivin, and induce mitochondrial-mediated apoptosis in gastric cancer cells and inhibit gastric orthotopic transplantation tumor growth

Glycolysis is the primary method utilized by cancer cells to produce the energy (adenosine triphosphate, ATP) required for cell proliferation. Therefore, inhibition of glycolysis may inhibit tumor growth. We previously found that both 3-bromopyruvate (3-BrPA) and sodium citrate (SCT) can inhibit glycolysis in vitro; however, the underlying inhibitory mechanisms remain unclear. In the present study, we used a human gastric cancer cell line (SGC-7901) and an orthotopic transplantation tumor model in nude mice to explore the specific mechanisms of 3-BrPA and SCT. We found that both 3-BrPA and SCT effectively suppressed cancer cell proliferation, arrested the cell cycle, induced apoptosis, and decreased the production of lactate and ATP. 3-BrPA significantly reduced the glycolytic enzyme hexokinase activity, while SCT selectively inhibited phosphofructokinase-1 activity. Furthermore, 3-BrPA and SCT upregulated the expression of pro-apoptotic proteins (Bax, cytochrome c, and cleaved caspase-3) and downregulated the expression of anti-apoptotic proteins (Bcl-2 and survivin). Finally, our animal model of gastric cancer indicated that intraperitoneal injection of 3-BrPA and SCT suppressed orthotopic transplantation tumor growth and induced tumor apoptosis. Taken together, these results suggest that 3-BrPA and SCT selectively suppress glycolytic enzymes, decrease ATP production, induce mitochondrial-mediated apoptosis, downregulate survivin, and inhibit tumor growth. Moreover, an intraperitoneal injection is an effective form of administration of 3-BrPA and SCT.

Bioresponsive antisense DNA gold nanobeacons as a hybrid in vivo theranostics platform for the inhibition of cancer cells and metastasis

Gold nanobeacons can be used as a powerful tool for cancer theranostics. Here, we proposed a nanomaterial platform based on gold nanobeacons to detect, target and inhibit the expression of a mutant Kras gene in an in vivo murine gastric cancer model. The conjugation of fluorescently-labeled antisense DNA hairpin oligonucleotides to the surface of gold nanoparticles enables using their localized surface plasmon resonance properties to directly track the delivery to the primary gastric tumor and to lung metastatic sites. The fluorescently labeled nanobeacons reports on the interaction with the target as the fluorescent Cy3 signal is quenched by the gold nanoparticle and only emit light following conjugation to the Kras target owing to reorganization and opening of the nanobeacons, thus increasing the distance between the dye and the quencher. The systemic administration of the anti-Kras nanobeacons resulted in approximately 60% tumor size reduction and a 90% reduction in tumor vascularization. More important, the inhibition of the Kras gene expression in gastric tumors prevents the occurrence of metastasis to lung (80% reduction), increasing mice survival in more than 85%. Our developed platform can be easily adjusted to hybridize with any specific target and provide facile diagnosis and treatment for neoplastic diseases.

Role of RNA-interference-induced zinc finger protein 139 suppression in gastric cancer cell sensitivity to chemotherapeutic agents

Zinc finger proteins (ZNFs) are a class of proteins widely distributed in the human genome, which have been found to play a role in the regulation of gene transcription and the occurrence and development of gastric cancer (GC). ZNF139 was found to be associated with GC in our previous experiments. The present study aimed to analyse the differences in ZNF139 protein expression in SGC7901 GC cells and in situ grafted GC tumors in nude mice prior to and following RNA interference inhibition, and to investigate the mechanisms underlying ZNF139 involvement in the occurrence, development and chemosensitivity of GC. A ZNF139-targeted small interfering (si)RNA plasmid was constructed and transfected into the cancer cells and in situ grafted tumors. The MTT assay was used to investigate the alterations in chemosensitivity prior to and following transfection of siRNA-ZNF139. The two-dimensional difference gel electrophoresis and liquid chromatography-mass spectrometry techniques were used to identify the different protein points prior to and following siRNA-ZNF139 transfection. Western blot analysis was performed to confirm the identified proteins. In the siRNA-ZNF139 group, the growth of the cancer cells and in situ grafted tumors significantly decreased. However, the post-interference chemosensitivity to 5-fluorouracil, cisplatin and mitomycin C significantly increased. In the in vivo and in vitro experiments, the expression of pyridoxal kinase (PDXK) was upregulated, whereas the expression levels of annexin A2 (ANXA2) and fascin were downregulated following transfection. Western blot analysis confirmed the results for PDXK, ANXA2 and fascin by proteomics. Therefore, ZNF139 may participate in the occurrence, development and chemosensitivity of GC by promoting the expression of ANXA2 and fascin, while inhibiting the expression of PDXK.

Animal models of gastrointestinal inflammation and cancer

Inflammation and cancer are the two major disorders in the gastrointestinal tract. They are causally related in their pathogenesis. It is important to study animal models' causal relationship and, in particular, to discover new therapeutic agents for such diseases. There are several criteria for these models in order to make them useful in better understanding the etiology and treatment of the said diseases in humans. In this regard, animal models should be similar as possible to human diseases and also be easy to produce and reproducible and also economic to allow a continuous replication in different laboratories. In this review, we summarize the various animal models for inflammatory and cancerous disorders in the upper and lower gastrointestinal tract. Experimental approaches are as simple as by giving a single oral dose of alcohol or other noxious agents or by injections of multiple dosages of ulcer inducing agents or by parenteral administration or in drinking water of carcinogens or by modifying the genetic makeups of animals to produce relatively long-term pathological changes in particular organs. With these methods they could induce consistent inflammatory responses or tumorigenesis in the gastrointestinal mucosa. These animal models are widely used in laboratories in understanding the pathogenesis as well as the mechanisms of action for therapeutic agents in the treatment of gastrointestinal inflammation and cancer.

Co-transduction of ribosomal protein L23 enhances the therapeutic efficacy of adenoviral-mediated p53 gene transfer in human gastric cancer

Induction of murine double minute 2 (MDM2) expression is thought to be a determinant of resistance to p53 gene therapy for cancer. Previous studies have revealed that ribosomal protein L23 (RPL23) inhibits MDM2-mediated p53 degradation through direct binding to MDM2. In addition, ectopically expressed RPL23 was reported to interact with MDM2 in both the nucleus and cytoplasm, by which RPL23 indirectly inhibited MDM2-p53 binding. Based on the known molecular properties of the RPL23 protein, it was speculated that co-transduction of RPL23 may protect wild‑type p53 protein from MDM2-mediated inactivation and, thus, improve the effect of delivering therapeutic exogenous p53. To test this hypothesis, we constructed a bicistronic adenoviral vector expressing both the RPL23 and p53 genes (Ad-RPL23/p53) and compared its tumor-suppressor activity in human gastric cancer with that of a single gene vector for p53 (Ad-p53). In the in vivo and in vitro experiments, we observed that treatment with Ad-RPL23/p53 resulted in a stronger antitumor response compared to that obtained using Ad-p53. Moreover, the antitumor response of the bicistronic adenovirus was obtained not only in MGC803 cells (endogenous mutant p53) but also in MKN45 cells (endogenous wild‑type p53) which were initially resistant to p53 gene transfer, indicating that co-transduction of RPL23 also expanded the utility of p53 gene therapy. Furthermore, in an orthotopic nude mouse model of human gastric cancer, we found that the survival benefit was greater after Ad-RPL23/p53 treatment than after Ad-p53. Taken together, the data presented here demonstrate that co-transduction of RPL23 enhances the therapeutic efficacy of adenoviral-mediated p53 gene transfer in models of human gastric cancer and support the use of this strategy for cancer treatment.

A true orthotopic gastric cancer murine model using electrocoagulation

BACKGROUND

Orthotopic mouse models of human gastric cancer represent an important in vivo tool for testing chemotherapeutic agents and for studying intraluminal factors. Currently, orthotopic mouse models of gastric cancer require an operative procedure involving either injection or implantation of tumor cells in stomach layers. The resultant tumor does not grow from the stomach's mucosal surface, so it does not mimic the human disease process.

STUDY DESIGN

A low-dose gastric mucosal coagulation was done transorally in the body of stomach using a specially designed polyethylene catheter in 16 female severe combined immunodeficient mice. This was followed by the instillation of SNU-16 human gastric cancer tumor cells (1 × 10(6) cells). Five mice each were euthanized at 1 and 2 months, and 6 mice were euthanized at 3 months. Three control mice underwent electrocoagulation alone and 3 mice underwent cell line instillation alone.

RESULTS

Tumors were detected in 11 of 16 experimental mice, but not in the control mice. Tumors were noted in mice at 1 month. Over time, there was an increase in tumor growth and metastasis to lymph nodes and surrounding organs. Histopathologic evaluation showed that the tumors grew from the gastric mucosa.

CONCLUSIONS

Our model is easy to create and overcomes the limitations of the existing models, as the tumor arises from the stomach's mucosal layer and mimics the human disease in terms of morphology and biologic behavior. This is the first report of a true orthotopic gastric cancer murine model. This model opens new doors for additional studies that were not possible earlier.

Characterization of gastric cancer models from different cell lines orthotopically constructed using improved implantation techniques

AIM: To develop orthotopic gastric cancer mouse models from different cell lines and characterize the tumor features to assist further in preclinical trials and clinical treatment strategies.

METHODS: Human gastric cancer SGC-7901 and BGC-823 cell suspensions were injected subcutaneously into nude mice to develop solid tumors, and tumor tissue pieces were then implanted under the serous coat of the stomach. An autopsy was performed on all animals of the SGC-7901 and BGC-823 models to observe the primary tumor growth and metastases using pathological and immunohistochemical methods.

RESULTS: Both models showed large tumors in situ resulting in pressure and infiltration of the adjacent organs. The gastric cavity became smaller, along with stenosis of the cardia or pylorus. There were biological and statistical differences between the two models. The metastasis rate in involved organs (lymph nodes, kidney, spleen, testis) was significantly higher in the BGC-823 model compared to the SGC-7901 model (P < 0.05 or P < 0.01). The median survival of the BGC-823 model was shorter than that of SGC-7901 (23 d vs 84 d, P < 0.05). Histopathologically, the primary tumor and metastatic lesions of the two models showed obvious atypia and mucus in the cytoplasm. Compared with the SGC-7901 model, BGC-823 appeared more poorly differentiated (absence of adenoid structure), had a smaller volume, and richer capillary structure. Immunohistochemical staining revealed cytokeratin 20 and epithelial membrane antigen expression was positive in the SGC-7901 tumors, while negative in BGC-823 ones.

CONCLUSION: Models using the SGC-7901 and BGC-823 cell lines were established which could function in gastric cancer research on carcinogenesis mechanism and drug discovery. The two models showed different tumor behavior and the latter was more malignant than the former.

Serial observations on an orthotopic gastric cancer model constructed using improved implantation technique

AIM: To establish a gastric cancer nude-mouse model with improved orthotopic implantation and investigate its biological characteristics at different time points.

METHODS: Human gastric cancer SGC-7901 cell suspensions were injected subcutaneously into a nude mouse to develop solid tumors, and the tumor tissue pieces were implanted under the serous coat. The nude mice were then euthanized in group every two weeks to observe the primary tumor growth and metastases.

RESULTS: Within 2-4 wk, there were no obvious changes about the primary tumor in stomach. At the sixth week, the primary tumor began to grow fast, resulting in incrassation of the gastric wall and stenosis of the gastric cavity, and metastases into the liver and lymph nodes were detected. The tumor, which compressed the adjacent organs, gradually became bigger and bigger followed by stenosis or vanishment of the gastric cavity from 8 to 12 wk. There were massive metastases, and the rate of metastasis was 58% in lymph nodes, 78% in liver, 39% in kidney, and 81% in peritoneum or septum.

CONCLUSION: A gastric cancer model is established, which can simulate the clinical tumor behavior and provide experimental carrier for clinical trials of gastric cancer treatment.