Two types of peritoneal dissemination of pancreatic cancer cells in a hamster model

Sugar-binding profiles of the mesothelial glycocalyx in frozen tissues of mice revealed by lectin staining

The mesothelium is a non-adhesive protective surface that lines the serosal cavities and organs within the body. The glycocalyx is a complex structure that coats the outer layer of the mesothelium. However, due to the limitations of conventional fixation techniques, studies on glycans are limited. In this study, lectin staining of frozen tissues was performed to investigate the diversity of glycans in the glycocalyx of mesothelial cells in mice. Datura stramonium lectin (DSL), which recognizes lactosamine and binds to Galectin-3 and -1, was broadly bound to the mesothelial cells of the visceral and parietal peritoneum but not to the pancreas, liver, intestine, or heart. Furthermore, human mesothelial cells in the omentum and parietal peritoneum were positive for DSL. Erythrina cristagalli lectin binding was specific to mesothelial cells in the parietal peritoneum, that is, the pleura, diaphragm, and peritoneum. Intriguingly, surface sialylation, the key element in reducing peritoneal dissemination and implantation, and promoting ascites formation by ovarian carcinoma cells, was much higher in the parietal peritoneum than in the omentum. These findings revealed slight differences in the glycans of mesothelial cells of different organs, which may be related to clinical diseases. These results also suggest that there may be differences in the functions of parietal and visceral mesothelial cells.

Modeling pancreatic cancer in mice for experimental therapeutics

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy that is characterized by early metastasis, low resectability, high recurrence, and therapy resistance. The experimental mouse models have played a central role in understanding the pathobiology of PDAC and in the preclinical evaluation of various therapeutic modalities. Different mouse models with targetable pathological hallmarks have been developed and employed to address the unique challenges associated with PDAC progression, metastasis, and stromal heterogeneity. Over the years, mouse models have evolved from simple cell line-based heterotopic and orthotopic xenografts in immunocompromised mice to more complex and realistic genetically engineered mouse models (GEMMs) involving multi-gene manipulations. The GEMMs, mostly driven by KRAS mutation(s), have been widely accepted for therapeutic optimization due to their high penetrance and ability to recapitulate the histological, molecular, and pathological hallmarks of human PDAC, including comparable precursor lesions, extensive metastasis, desmoplasia, perineural invasion, and immunosuppressive tumor microenvironment. Advanced GEMMs modified to express fluorescent proteins have allowed cell lineage tracing to provide novel insights and a new understanding about the origin and contribution of various cell types in PDAC pathobiology. The syngeneic mouse models, GEMMs, and target-specific transgenic mice have been extensively used to evaluate immunotherapies and study therapy-induced immune modulation in PDAC yielding meaningful results to guide various clinical trials. The emerging mouse models for parabiosis, hepatic metastasis, cachexia, and image-guided implantation, are increasingly appreciated for their high translational significance. In this article, we describe the contribution of various experimental mouse models to the current understanding of PDAC pathobiology and their utility in evaluating and optimizing therapeutic modalities for this lethal malignancy.

Molecular mediators of peritoneal metastasis in pancreatic cancer

Pancreatic cancer is the third leading cause of cancer death in the USA, and pancreatic ductal adenocarcinoma (PDA) constitutes 85% of pancreatic cancer diagnoses. PDA frequently metastasizes to the peritoneum, but effective treatment of peritoneal metastasis remains a clinical challenge. Despite this unmet need, understanding of the biological mechanisms that contribute to development and progression of PDA peritoneal metastasis is sparse. By contrast, a vast number of studies have investigated mechanisms of peritoneal metastasis in ovarian and gastric cancers. Here, we contrast similarities and differences between peritoneal metastasis in PDA as compared with those in gastric and ovarian cancer by outlining molecular mediators involved in each step of the peritoneal metastasis cascade. This review aims to provide mechanistic insights that could be translated into effective targeted therapies for patients with peritoneal metastasis from PDA.

Pathological Characterization of Ovarian Cancer Patients Who Underwent Debulking Surgery in Combination With Diaphragmatic Surgery: A Cross-Sectional Study

Despite exhaustive efforts to detect early-stage ovarian cancers, greater than two-thirds of patients are diagnosed at an advanced stage. Although diaphragmatic metastasis is not rare in advanced ovarian cancer patients and often precludes optimal cytoreductive surgery, little is known about the mechanisms and predictive factors of metastasis to the diaphragm. Thus, as an initial step toward investigating such factors, the present study was conducted to characterize the pathological status of ovarian cancer patients who underwent debulking surgery in combination with diaphragmatic surgery. This is a retrospective and cross-sectional study of patients who underwent debulking surgery in combination with diaphragmatic surgery at our institution between January 2005 and July 2015. Clinicopathological data were reviewed by board-certified gynecologists, pathologists, and cytopathologists. The rates of various pathological findings were investigated and compared by Fisher exact test between 2 groups: 1 group that was pathologically positive for diaphragmatic metastasis (group A) and another group that was pathologically negative for diaphragmatic metastasis (group B). Forty-six patients were included: 41 patients pathologically positive and 5 pathologically negative for diaphragmatic metastasis. The rates of metastasis to the lymph node (95.8% vs 20%, P = 0.001) and metastasis to the peritoneum except for the diaphragm (97.6% vs 60.0%, P = 0.028) were significantly increased in group A compared with group B. However, no significant differences between the 2 groups were found for rates of histological subtypes (high-grade serous or non-high-grade serous), the presence of ascites, the presence of malignant ascites, exposure of cancer cells on the ovarian surface, blood vascular invasion in the primary lesion, and lymphovascular invasion in the primary lesion. Our study demonstrated that metastasis to the lymph node and nondiaphragmatic metastasis to the peritoneum are significantly associated with metastasis to the diaphragmatic peritoneum, indicating that these factors may be pathological predictors of diaphragmatic metastasis in patients with ovarian cancer. However, as the data available are not sufficient to demonstrate the predictive power of these factors, a further comprehensive, large-scale study should be performed.

New pancreatic carcinoma model for studying oncolytic adenoviruses in the permissive Syrian hamster

Syrian hamster is a practical animal model for studying the systemic effects of oncolytic vectors derived from adenovirus serotype 5 (Ad5). Ad5 replicates well in Syrian hamster tissues, and Syrian hamster cell lines are available that are known to support Ad5 replication. In this study, we established four new Syrian hamster cell lines from transplantable pancreatic, renal, hepatic and lung tumors. The pancreatic cell line (SHPC6) and the renal cell line were highly permissive for Ad5 replication. The SHPC6 cell line formed disseminated intraperitoneal tumors when cells were injected into the peritoneal cavity. INGN 007, an oncolytic Ad5-based vector, completely reversed the growth of disseminated intraperitoneal SHPC6 tumor nodules following intraperitoneal injection of the vector, leading to 100% survival of the treated animals. SHPC6 cells also formed subcutaneous tumors, whose growth was suppressed by INGN 007 following intratumoral injection. INGN 007 replicated in both the intraperitoneal and subcutaneous SHPC6 tumors. Following intraperitoneal injection, INGN 007 did not replicate in the livers of hamsters with intraperitoneal SHPC6 tumors, and was not hepatotoxic. These studies suggest that the SHPC6 cell line may be useful as a model for disseminated pancreatic cancer, and that INGN 007 may be a safe and effective vector to treat these tumors.

Experimental pancreatic cancer model using PGHAM-1 cells: characteristics and experimental therapeutic trials

We developed short-term pancreatic cancer models in hamsters using PGHAM-1 cells and examined the utility of the models for research on metastasis and for therapeutic trials. With 3 PGHAM-1 models, including 1) primary pancreatic cancer and simultaneous liver metastasis by intrapancreatic transplantation, 2) liver metastasis alone by intrasplenic transplantation, 3) peritoneal dissemination by intraperitoneal transplantation, within 21 days after inoculation, we studied the specific characteristics of metastases and the effects of several antiangiogenic substances on primary and metastatic pancreatic tumors. Several experiments showed that vascular endotherial growth factor and anatomical characteristics were important factors for metastasis. In therapeutic experiments, the incidence, size, diameter, microvessel density, and apoptotic index of the tumors were preferably influenced by the antiangiogenic substances. In addition, PGHAM-1-Luc, which is luciferase-positive PGHAM-1 cell line, was newly developed and is expected to be a useful new animal model. These models would be suitable for the study of pathogenesis of pancreatic cancer and its metastasis and for preclinical trials of chemotherapeutic agents, such as antiangiogenic substances.

Possible role of milky spots in mesothelial transplantation

Milky spots are very small omental organs, in contact with peritoneal membrane, devoid of capsule and consisting of macrophages, lymphocytes and a few plasma cells supported by blood and lymphatic vessels. The exact role of these particular organs is still not clear, but they are similar to lymphatic structures and it is clear that they play a role in peritoneal infection and abdominal tumors. Peritoneal dialysis seems to activate the milky spots changing their morphology. The authors try to formulate some hypotheses on the role played by these little omental organs during autologous mesothelial transplant.

Adeno-associated viral vector-mediated expression of endostatin inhibits tumor growth and metastasis in an orthotropic pancreatic cancer model in hamsters

We examined the feasibility of using adeno-associated virus (AAV)-mediated systemic delivery of endostatin in gene therapy to treat metastasis of pancreatic cancer. We established an animal model of orthotopic metastatic pancreatic cancer in which the pancreatic cancer cell line PGHAM-1 was inoculated into the pancreas of Syrian golden hamsters. Transplanted cells proliferated rapidly and metastasized to the liver. An AAV vector expressing endostatin (5 x 10(10) particles) was injected intramuscularly into the left quadriceps or intravenously into the portal vein. These routes of vector administration were evaluated by comparing various parameters of tumor development. Intramuscular injection of the vector modestly increased the serum endostatin level. The numbers of metastases and the incidence of hemorrhagic ascites were decreased in the treated animals. In contrast, the serum concentration of endostatin was significantly increased after intraportal injection of the vector. The antitumor effects on all parameters (including the size and microvessel density of primary pancreatic tumors, the sizes and number of liver metastases, and the incidence of hemorrhagic ascites) were significant. These results suggest that systemic delivery of endostatin represents a potentially effective treatment for pancreatic cancer and liver metastases. The route of vector administration influences the efficacy of AAV-mediated endostatin expression. Intraportal injection of the AAV vector appears to be more effective as an antiangiogenic gene therapy for pancreatic cancer.

Effects of bile acids on proliferation and ultrastructural alteration of pancreatic cancer cell lines

AIM: Pancreatic cancer in the head is frequently accompanied by jaundice and high bile acid level in serum. This study focused on the direct effects of bile acids on proliferation and ultrastructural alteration of pancreatic cancer.

METHODS: Pancreatic cancer cell lines PANC-1, MIA PaCa-2 and PGHAM-1 were explored in this study. The cell lines were cultured in media supplemented with certain bile acids, CA, DCA, LCA, TCDC, TDCA and GCA. Their influence on cell growth was measured with MTT assay after 72 h of incubation. Cell cycles of PANC-1 cells in 40 μM of bile acids media were analyzed by flow cytometry. Ultrastructural alteration of PANC-1 cells induced by DCA was observed using scanning and transmission electron microscope (SEM and TEM).

RESULTS: At various concentrations of bile acids and incubation time, no enhanced effects of bile acids on cell proliferation were observed. Significant inhibitory effects were obtained in almost all media with bile acids. DCA and CA increased the percentage of G₀+G₁ phase cells, while GCA and TDCA elevated the S phase cell number. After 48 h of incubation in DCA medium, PANC-1 cells showed some structural damages such as loss of their microvilli and vacuolization of organelles in cytoplasm.

CONCLUSION: Bile acids can reduce proliferation of pancreatic cancer cells due to their direct cytotoxicity. This result implies that elevation of bile acids in jaundiced serum may inhibit pancreatic cancer progression.