Generation of a syngeneic mouse model to study the intraperitoneal dissemination of ovarian cancer with in vivo luciferase imaging

Efficacy and safety of a third-generation oncolytic herpes virus G47Δ in models of human esophageal carcinoma

Treatment options are limited for esophageal carcinoma (EC). G47Δ, a triple-mutated, conditionally replicating herpes simplex virus type 1 (HSV-1), exhibits enhanced killing of tumor cells with high safety features. Here, we studied the efficacy of G47Δ using preclinical models of human EC. In vitro, G47Δ showed efficient cytopathic effects and replication capabilities in all eight human esophageal cancer cell lines tested. In athymic mice harboring subcutaneous tumors of human EC (KYSE180, TE8, and OE19), two intratumoral injections with G47Δ significantly inhibited the tumor growth. To mimic the clinical treatment situations, we established an orthotopic EC model using luciferase-expressing TE8 cells (TE8-luc). An intratumoral injection with G47Δ markedly inhibited the growth of orthotopic TE8-luc tumors in athymic mice. Furthermore, we evaluated the safety of applying G47Δ to the esophagus in mice. A/J mice inoculated intraesophageally or administered orally with G47Δ (10⁷ plaque-forming units [pfu]) survived for more than 2 months without remarkable symptoms, whereas the majority with wild-type HSV-1 (10⁶ pfu) deteriorated within 10 days. PCR analyses showed that the G47Δ DNA was confined to the esophagus after intraesophageal inoculation and was not detected in major organs after oral administration. Our results provide a rationale for the clinical use of G47Δ for treating EC.

Assessment of the immune landscapes of advanced ovarian cancer in an optimized in vivo model

BACKGROUND

Ovarian cancer (OC) is typically diagnosed late, associated with high rates of metastasis and the onset of ascites during late stage disease. Understanding the tumor microenvironment and how it impacts the efficacy of current treatments, including immunotherapies, needs effective in vivo models that are fully characterized. In particular, understanding the role of immune cells within the tumor and ascitic fluid could provide important insights into why OC fails to respond to immunotherapies. In this work, we comprehensively described the immune cell infiltrates in tumor nodules and the ascitic fluid within an optimized preclinical model of advanced ovarian cancer.

METHODS

Green Fluorescent Protein (GFP)-ID8 OC cells were injected intraperitoneally into C57BL/6 mice and the development of advanced stage OC monitored. Nine weeks after tumor injection, mice were sacrificed and tumor nodules analyzed to identify specific immune infiltrates by immunohistochemistry. Ascites, developed in tumor bearing mice over a 10-week period, was characterized by mass cytometry (CyTOF) to qualitatively and quantitatively assess the distribution of the immune cell subsets, and their relationship to ascites from ovarian cancer patients.

RESULTS

Tumor nodules in the peritoneal cavity proved to be enriched in T cells, antigen presenting cells and macrophages, demonstrating an active immune environment and cell-mediated immunity. Assessment of the immune landscape in the ascites showed the predominance of CD8+ , CD4+ , B- , and memory T cells, among others, and the coexistance of different immune cell types within the same tumor microenvironment.

CONCLUSIONS

We performed, for the first time, a multiparametric analysis of the ascitic fluid and specifically identify immune cell populations in the peritoneal cavity of mice with advanced OC. Data obtained highlights the impact of CytOF as a diagnostic tool for this malignancy, with the opportunity to concomitantly identify novel targets, and define personalized therapeutic options.

CD244+ polymorphonuclear myeloid‑derived suppressor cells reflect the status of peritoneal dissemination in a colon cancer mouse model

Despite the recent development of chemotherapeutic agents, the prognosis of colorectal cancer (CRC) patients with peritoneal dissemination (PD) remains poor. The tumor immune microenvironment (TIME) has drawn attention as a key contributing factor of tumor progression. Of TIME components, myeloid-derived suppressor cells (MDSCs) are considered to play a responsible role in the immunosuppressive characteristics of the TIME. MDSCs are classified into two major subsets: Monocytic MDSCs (M-MDSCs) and polymorphonuclear MDSCs (PMN-MDSCs). Therefore, we hypothesize that MDSCs would play important roles in the PD-relevant TIME and PD progression. To address this hypothesis, we established PD mouse models. As the PD nodules consisted scarcely of immune cells, we focused on the peritoneal cavity, but not PD nodule, to evaluate the PD-relevant TIME. As a result, intraperitoneal PMN-MDSCs were found to be substantially increased in association with PD progression. Based on these results, we phenotypically and functionally verified the usefulness of CD244 for identifying PMN-MDSCs. In addition, the concentrations of interleukin (IL)-6 and granulocyte-colony stimulating factor (G-CSF) were significantly increased in the peritoneal cavity, both of which were produced by the tumors and thought to contribute to the increases in the PMN-MDSCs. In vivo depletion of the PMN-MDSCs by anti-Ly6G monoclonal antibody (mAb) significantly inhibited the PD progression and reverted CD4⁺ and CD8⁺ T cells in the peritoneal cavity and the peripheral blood. Collectively, these results suggest that the targeted therapy for PMN-MDSCs would provide not only new therapeutic value but also a novel strategy to synergize with T-cell-based immunotherapy for CRC-derived PD.

Pretreatment with LCK inhibitors chemosensitizes cisplatin-resistant endometrioid ovarian tumors

Background

Ovarian cancer is the most fatal gynecologic malignancy in the United States. While chemotherapy is effective in the vast majority of ovarian cancer patients, recurrence and resistance to standard systemic therapy is nearly inevitable. We discovered that activation of the non-receptor tyrosine kinase Lymphocyte Cell-Specific Protein-Tyrosine Kinase (LCK) promoted cisplatin resistance. Here, we hypothesized that treating high grade, platinum resistant endometrioid cancer cells with an LCK inhibitor (LCKi) followed by co-treatment with cisplatin would lead to increased cisplatin efficacy. Our objective was to assess clinical outcomes associated with increased LCK expression, test our hypothesis of utilizing LCKi as pre-treatment followed by co-treatment with cisplatin in platinum resistant ovarian cancer in vitro, and evaluate our findings in vivo to assess LCKi applicability as a therapeutic agent.

Results

Kaplan-Meier (KM) plotter data indicated LCK expression is associated with significantly worse median progression-free survival (HR 3.19, p = 0.02), and a trend toward decreased overall survival in endometrioid ovarian tumors with elevated LCK expression (HR 2.45, p = 0.41). In vitro, cisplatin resistant ovarian endometrioid cells treated first with LCKi followed by combination LCKi-cisplatin treatment showed decreased cell viability and increased apoptosis. Immunoblot studies revealed LCKi led to increased expression of phosphorylated H2A histone family X (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma$$\end{document}γ-H2AX), a marker for DNA damage. In vivo results demonstrate treatment with LCKi followed by LCKi-cisplatin led to significantly slowed tumor growth.

Conclusions

We identified a strategy to therapeutically target cisplatin resistant endometrioid ovarian cancer leading to chemosensitization to platinum chemotherapy via treatment with LCKi followed by co-treatment with LCKi-cisplatin.

Use of Transabdominal Ultrasound for the detection of intra-peritoneal tumor engraftment and growth in mouse xenografts of epithelial ovarian cancer

OBJECTIVE

To evaluate intraperitoneal (IP) tumor engraftment, metastasis and growth in a pre-clinical murine epithelial ovarian cancer (EOC) model using both transabdominal ultrasound (TAUS) and bioluminescence in vivo imaging system (IVIS).

METHODS

Ten female C57Bl/6J mice at six weeks of age were included in this study. Five mice underwent IP injection of 5x106 ID8-luc cells (+ D- luciferin) and the remaining five mice underwent IP injection of ID8-VEGF cells. Monitoring of tumor growth and ascites was performed weekly starting at seven days post-injection until study endpoint. ID8-luc mice were monitored using both TAUS and IVIS, and ID8-VEGF mice underwent TAUS monitoring only. Individual tumor implant dimension and total tumor volume were calculated. Average luminescent intensity was calculated and reported per mouse abdomen. Tumor detection was confirmed by gross evaluation and histopathology. All data are presented as mean +/- standard deviation.

RESULTS

Overall, tumors were successfully detected in all ten mice using TAUS and IVIS, and tumor detection correlated with terminal endpoint histology/ H&E staining. For TAUS, the smallest confirmed tumor measurements were at seven days post-injection with mean long axis of 2.23mm and mean tumor volume of 4.17mm3. However, IVIS imaging was able to detect tumor growth at 14 days post-injection. Ascites formation was detected in mice at 21 days post-injection.

CONCLUSIONS

TAUS is highly discriminatory for monitoring EOC in pre-clinical murine model, allowing for detection of tumor dimension as small as 2 mm and as early as seven days post-injection compared to IVIS. In addition, TAUS provides relevant information for ascites development and detection of multiple small metastatic tumor implants. TAUS provides an accurate and reliable method to detect and monitor IP EOC growth in mouse xenografts.

Efficacy of a Third-Generation Oncolytic Herpes Virus G47Δ in Advanced Stage Models of Human Gastric Cancer

Advanced gastric cancer, especially scirrhous gastric cancer with peritoneal dissemination, remains refractory to conventional therapies. G47Δ, a third-generation oncolytic herpes simplex virus type 1, is an attractive novel therapeutic agent for solid cancer. In this study, we investigated the therapeutic potential of G47Δ for human gastric cancer. In vitro, G47Δ showed good cytopathic effects and replication capabilities in nine human gastric cancer cell lines tested. In vivo, intratumoral inoculations with G47Δ (2 × 10⁵ or 1 × 10⁶ plaque-forming units [PFU]) significantly inhibited the growth of subcutaneous tumors (MKN45, MKN74, and 44As3). To evaluate the efficacy of G47Δ for advanced-stage models of gastric cancer, we generated an orthotopic tumor model and peritoneal dissemination models of human scirrhous gastric cancer (MKN45-luc and 44As3Luc), which have features mimicking intractable scirrhous cancer patients. G47Δ (1 × 10⁶ PFU) was constantly efficacious whether administered intratumorally or intraperitoneally in the clinically relevant models. Notably, G47Δ injected intraperitoneally readily distributed to, and selectively replicated in, disseminated tumors. Furthermore, flow cytometric analyses of tumor-infiltrating cells in subcutaneous tumors revealed that intratumoral G47Δ injections markedly decreased M2 macrophages while increasing M1 macrophages and natural killer (NK) cells. These findings indicate the usefulness of G47Δ for treating human gastric cancer, including scirrhous gastric cancer and the ones in advanced stages.

Differentiation of Stem Cells from Human Exfoliated Deciduous Teeth into Retinal Photoreceptor-Like Cells and Their Sustainability In Vivo

Retinal degeneration is characterized by the progressive loss of photoreceptors, and stem cell therapy has become a promising strategy. Many studies have reported that mesenchymal stem cell transplantation can sustain retinal structure and prolong retinal functions based on two mechanisms. One is cell replacement, and the other is the paracrine action of stem cells. Cells from human exfoliated deciduous teeth (SHEDs) show characteristics typical of mesenchymal stem cells. They are derived from the neural crest and are a potential cellular source for neural regeneration in stem cell therapy. In this study, we explored the potential of SHEDs to be induced towards the retinal photoreceptor phenotype and to be sustainable in an animal model of retinal degeneration. A factor-cocktail protocol was used to induce SHEDs towards retinal photoreceptors for 24 days, and the characteristics of the induced cells were identified in terms of morphological changes, biomarker expression and subcellular distribution, and calcium influx. SHEDs were labeled with firefly luciferase for in vivo tracking by bioluminescent imaging and then transplanted into the subretinal space of mice. Our results showed that SHEDs successfully transdifferentiated into photoreceptor-like cells, which displayed neuron-like morphology, and expressed specific genes and proteins associated with retinal precursors, photoreceptor precursors, and mature photoreceptors. In addition, calcium influx was significantly greater in the retinal-induced than in noninduced SHEDs. In vivo tracking confirmed at least 2 weeks of good survival by bioluminescent imaging and 3 months of sustainability of SHEDs by histological analysis. We conclude that SHEDs have the potential to transdifferentiate into retinal photoreceptor-like cells in vitro and maintain good viability in vivo after transplantation into mice with a normal immune system. This demonstrates preliminary success in generating photoreceptor-like cells from SHEDs and applying SHEDs in treating retinal degeneration.

HSDL2 Promotes Bladder Cancer Growth In Vitro and In Vivo

Bladder cancer is a common malignant urinary tumor, and patients with bladder cancer have poor prognosis. Abnormal lipid metabolism in peroxisomes is involved in tumor progression. Hydroxysteroid dehydrogenase-like 2 (HSDL2) localized in peroxisomes regulates fatty acid synthesis. In the present study, we reported that HSDL2 was upregulated in two human bladder cancer cell lines 5637 and T24 compared to normal human urothelial cells. Furthermore, lentiviral-mediated HSDL2 knockdown inhibited the proliferation and colony formation while promoted the apoptosis of human bladder cancer T24 cells in vitro. In nude mice HSDL2 knockdown inhibited the growth of T24 derived xenografts in vivo. In conclusion, our results suggest that HSDL2 plays an oncogenic role in bladder cancer and might serve as a potential target for bladder cancer therapy.

Establishment of a novel method to evaluate peritoneal microdissemination and therapeutic effect using luciferase assay

Peritoneal dissemination is a major cause of recurrence in patients with malignant tumors in the peritoneal cavity. Effective anticancer agents and treatment protocols are necessary to improve outcomes in these patients. However, previous studies using mouse models of peritoneal dissemination have not detected any drug effect against peritoneal micrometastasis. Here we used the luciferase assay to evaluate peritoneal micrometastasis in living animals and established an accurate mouse model of early peritoneal microdissemination to evaluate tumorigenesis and drug efficacy. There was a positive correlation between luminescence intensity in in vivo luciferase assay and the extent of tumor dissemination evaluated by ex vivo luciferase assay and mesenteric weight. This model has advantages over previous models because optimal luciferin concentration without cell damage was validated and peritoneal microdissemination could be quantitatively evaluated. Therefore, it is a useful model to validate peritoneal micrometastasis formation and to evaluate drug efficacy without killing mice.

Gene therapy with SOCS1 for gastric cancer induces G2/M arrest and has an antitumour effect on peritoneal carcinomatosis

BACKGROUND

Suppressor of cytokine signaling1 (SOCS1) is a negative regulator of various cytokines. Recently, it was investigated as a therapeutic target in various cancers. However, the observed antitumour effects of SOCS1 cannot not be fully explained without taking inhibition of proliferation signalling into account. Our aim was to discover a new mechanism of antitumour effects of SOCS1 for gastric cancer (GC).

METHODS

We analysed the mechanism of antitumour effect of SOCS1 in vitro. In addition, we evaluated antitumour effect for GC using a xenograft peritoneal carcinomatosis mouse model in preclinical setting.

RESULTS

We confirmed that SOCS1 suppressed proliferation in four out of five GC cell lines. SOCS1 appeared to block proliferation by a new mechanism that involves cell cycle regulation at the G2/M checkpoint. We showed that SOCS1 influenced cell cycle-associated molecules through its interaction with ataxia telangiectasia and Rad3-related protein. The significant difference in therapeutic effects was noted in terms of the post-treatment weight and total photon count of the intra-abdominal tumours.

CONCLUSION

Forced expression of SOCS1 revealed a heretofore-unknown mechanism for regulating the cell cycle and may represent a novel therapeutic approach for the treatment of peritoneal carcinomatosis of GC.

Preservation of tumor-host immune interactions with luciferase-tagged imaging in a murine model of ovarian cancer

BACKGROUND

Ovarian cancer is immunogenic and residual tumor volume after surgery is known to be prognostic. Ovarian cancer often follows a recurring-remitting course and microscopic disease states may present ideal opportunities for immune therapies. We sought to establish the immune profile of a murine model of ovarian cancer that allows in vivo tumor imaging and the quantitation of microscopic disease.

RESULTS AND DISCUSSION

Baseline imaging and weight measurements were taken within 1 and 2 weeks after intraperitoneal tumor injection, respectively. Significantly higher photons per second from baseline imaging were first observed 5 weeks after tumor cell injection (p < 0.05) and continued to be significant through 8 weeks after injection (p < 0.01), whereas a significant increase in weight above baseline was not observed until day 56 (p < 0.0001). Expression of luc2 in ID8 cells did not alter the cellular immune microenvironment of the tumor. FOXP3+ T cells were more likely to be detected in the intraepithelial compartment and CD4+ T cells in the stroma as compared to CD3+ T cells, which were found equally in stroma and intraepithelial compartments.

CONCLUSIONS

Use of an intraperitoneal tumor expressing a codon-optimized firefly luciferase in an immunocompetent mouse model allows tumor quantitation in vivo and detection of microscopic tumor burdens. Expression of this foreign protein does not significantly effect tumor engraftment or the immune microenvironment of the ID8 cells in vivo and may allow novel immunotherapies to be assessed in a murine model for their translational potential to ovarian cancers in remission or minimal disease after primary cytoreductive surgery or chemotherapy.

METHODS

Mouse ovarian surface epithelial cells from C57BL6 mice transformed after serial passage in vitro were transduced with a lentiviral vector expressing a codon optimized firefly luciferase (luc2). Cell lines were selected and luc2 expression functionally confirmed in vitro. Cell lines were intraperitoneally (IP) implanted in albino C57BL/6/BrdCrHsd-Tyrc mice and albino B6(Cg)-Tyrc-2 J/J mice for serial imaging. D-luciferin substrate was injected IP and tumors were serially imaged in vivo using a Xenogen IVIS. Tumor take, weights, and luminescent intensities were measured. Immunohistochemistry was performed on tumors and assessed for immune infiltrates in stromal and intraepithelial compartments.

Indoleamine 2,3-dioxygenase promotes peritoneal metastasis of ovarian cancer by inducing an immunosuppressive environment

Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-catabolizing enzyme that has immunoregulatory functions. Our prior study showed that tumoral IDO overexpression is involved in disease progression and impaired patient survival in human ovarian cancer, although its mechanism remains unclear. The purpose of the present study is to clarify the role of IDO during the process of peritoneal dissemination of ovarian cancer. Indoleamine 2,3-dioxygenase cDNA was transfected into the murine ovarian carcinoma cell line OV2944-HM-1, establishing stable clones of IDO-overexpressing cells (HM-1-IDO). Then HM-1-IDO or control vector-transfected cells (HM-1-mock) were i.p. transplanted into syngeneic immunocompetent mice. The HM-1-IDO-transplanted mice showed significantly shortened survival compared with HM-1-mock-transplanted (control) mice. On days 11 and 14 following transplantation, the tumor weight of peritoneal dissemination and ascites volume were significantly increased in HM-1-IDO-transplanted mice compared with those of control mice. This tumor-progressive effect was coincident with significantly reduced numbers of CD8⁺ T cells and natural killer cells within tumors as well as increased levels of transforming growth factor-β and interleukin-10 in ascites. Finally, treatment with the IDO inhibitor 1-methyl-tryptophan significantly suppressed tumor dissemination and ascites with reduced transforming growth factor-β secretion. These findings showed that tumor-derived IDO promotes the peritoneal dissemination of ovarian cancer through suppression of tumor-infiltrating effector T cell and natural killer cell recruitment and reciprocal enhancement of immunosuppressive cytokines in ascites, creating an immunotolerogenic environment within the peritoneal cavity. Therefore, IDO may be a promising molecular target for the therapeutic strategy of ovarian cancer.

Recent technological advances in using mouse models to study ovarian cancer

Serous epithelial ovarian cancer (SEOC) is the most lethal gynecological cancer in the United States with disease recurrence being the major cause of morbidity and mortality. Despite recent advances in our understanding of the molecular mechanisms responsible for the development of SEOC, the survival rate for women with this disease has remained relatively unchanged in the last two decades. Preclinical mouse models of ovarian cancer, including xenograft, syngeneic, and genetically engineered mice, have been developed to provide a mechanism for studying the development and progression of SEOC. Such models strive to increase our understanding of the etiology and dissemination of ovarian cancer in order to overcome barriers to early detection and resistance to standard chemotherapy. Although there is not a single model that is most suitable for studying ovarian cancer, improvements have led to current models that more closely mimic human disease in their genotype and phenotype. Other advances in the field, such as live animal imaging techniques, allow effective monitoring of the microenvironment and therapeutic efficacy. New and improved preclinical mouse models, combined with technological advances to study such models, will undoubtedly render success of future human clinical trials for patients with SEOC.

Intraperitoneal administration of novel doxorubicin loaded polymeric delivery systems against peritoneal carcinomatosis: experimental study in a murine model of ovarian cancer

OBJECTIVE

Peritoneal spread is an adverse outcome in ovarian cancer. Despite clinical efficiency, intraperitoneal (i.p.) chemotherapy after cytoreductive surgery is associated with high systemic and local toxicity. Two polymer-drug delivery systems (P-HYD1-DOX and P-HYD2-DOX) were developed for i.p. administration by conjugating doxorubicin (DOX) to a poly(l-Lysine citramide) polymer carrier with a hydrazone-based degradable spacer. The aim of this study was to assess the antitumoral efficacy of these two conjugates in a xenograft model of human ovarian carcinomatosis.

METHODS

Peritoneal carcinomatosis was generated in athymic mice by i.p. injection of SKOV3-Luc cells. Free DOX, P-HYD1-DOX and P-HYD2-DOX solutions were administered i.p. at the same dose of 10 mg/kg (DOX eq.). For each treatment, tumor load and therapeutic efficacy were compared to untreated mice and assessed by bioluminescence imaging and survival rates. Toxicity profiles in each group and biodistribution of P-HYD2-DOX after i.p. administration were also determined.

RESULTS

P-HYD-1-DOX and P-HYD-2-DOX demonstrated significant antitumoral efficacy against peritoneal carcinomatosis. Compared to untreated group, P-HYD1-DOX improved median survival times from 58 to 105 days. For P-HYD2-DOX, median survival was not reached after a follow-up of 120 days. Bioluminescence showed high efficacy of P-HYD-2-DOX compared to free DOX but the difference was not significant. Biodistribution study confirmed that free and active DOX were successively released from P-HYD2-DOX in vivo. P-HYD-DOX conjugates were well tolerated by mice after i.p. injection.

CONCLUSION

P-HYD-DOX conjugates demonstrated significant activity against peritoneal carcinomatosis in a xenograft model of ovarian carcinomatosis and their ability to release active DOX in i.p. deposits and tumor. These features are of clinical interest for i.p. administration in the treatment of ovarian peritoneal carcinomatosis after cytoreductive surgery.

Evaluation of an intraperitoneal ovarian cancer syngeneic mouse model using 18F-FDG MicroPET imaging

OBJECTIVES

The objective of this study was to evaluate the syngeneic immunocompetent mouse model by using the micro-positron emission tomography with 2-[fluorine-18]-fluoro-2-deoxy-d-glucose (F-FDG microPET) imaging of ovarian tumor growth.

METHODS

ID8 ovarian carcinoma cells derived from C57BL/6 mice were intraperitoneally injected into female C57BL/6 mice. Mice were injected with F-FDG (7.4 MBq, intravenous injection), and microPET images were obtained 40 minutes later. Micro-computed tomographic images were also obtained immediately after microPET images for anatomical reference. F-FDG microPET images were acquired at baseline and at 4, 8, 10, and 11 weeks after tumor cell injection. The maximum standardized uptake value (SUVmax) in each time point was obtained from the images and compared to follow the tumor growth.

RESULTS

Physiological uptake of F-FDG was intensely found in the bladder and heart and frequently in the gastrointestinal tract. Diffused uptake of F-FDG was observed in the peritoneal cavity of all tumor-bearing mice at 4 weeks, and high focal uptakes were developed in the peritoneal cavity at 8 to 11 weeks. High focal uptakes increased over time, correlating with a progressive increase in the SUVmax of F-FDG. At 11 weeks, the SUVmax value was significantly increased (1.49 ± 0.10 at 11 weeks vs 0.29 ± 0.03 at baseline, P < 0.01). Tumors in the gut and peritoneum were confirmed by anatomical and histopathological examination.

CONCLUSIONS

Our results demonstrate that the peritoneal tumor growth in the syngeneic ovarian cancer model can be detected by the F-FDG microPET imaging.

Intraperitoneal photodynamic therapy mediated by a fullerene in a mouse model of abdominal dissemination of colon adenocarcinoma

Functionalized fullerenes represent a new class of photosensitizer (PS) that is being investigated for photodynamic therapy (PDT) of various diseases, including cancer. We tested the hypothesis that fullerenes could be used to mediate PDT of intraperitoneal (IP) carcinomatosis in a mouse model. In humans this form of cancer responds poorly to standard treatment and manifests as a thin covering of tumor nodules on intestines and on other abdominal organs. We used a colon adenocarcinoma cell line (CT26) stably expressing luciferase to allow monitoring of IP tumor burden in BALB/c mice by noninvasive real-time optical imaging using a sensitive low-light camera. IP injection of a preparation of N-methylpyrrolidinium-fullerene formulated in Cremophor-EL micelles, followed by white-light illumination delivered through the peritoneal wall (after creation of a skin flap), produced a statistically significant reduction in bioluminescence and a survival advantage in mice.

FROM THE CLINICAL EDITOR

This team of investigators report on functionalized fullerenes, to be used as photosensitizer for photodynamic therapy and demonstrate the efficacy of this method in an intraperitoneal carcinomatosis mouse model.

Development of a syngeneic mouse model of epithelial ovarian cancer

BACKGROUND

Most cases of ovarian cancer are epithelial in origin and diagnosed at advanced stage when the cancer is widely disseminated in the peritoneal cavity. The objective of this study was to establish an immunocompetent syngeneic mouse model of disseminated epithelial ovarian cancer (EOC) to facilitate laboratory-based studies of ovarian tumor biology and preclinical therapeutic strategies.

METHODS

Individual lines of TgMISIIR-TAg transgenic mice were phenotypically characterized and backcrossed to inbred C57BL/6 mice. In addition to a previously described line of EOC-prone mice, two lines (TgMISIIR-TAg-Low) were isolated that express the oncogenic transgene, but have little or no susceptibility to tumor development. Independent murine ovarian carcinoma (MOVCAR) cell lines were established from the ascites of tumor-bearing C57BL/6 TgMISIIR-TAg transgenic mice, characterized and tested for engraftment in the following recipient mice: 1) severe immunocompromised immunodeficient (SCID), 2) wild type C57BL/6, 3) oophorectomized tumor-prone C57BL/6 TgMISIIR-TAg transgenic and 4) non-tumor prone C57BL/6 TgMISIIR-TAg-Low transgenic. Lastly, MOVCAR cells transduced with a luciferase reporter were implanted in TgMISIIR-TAg-Low mice and in vivo tumor growth monitored by non-invasive optical imaging.

RESULTS

Engraftment of MOVCAR cells by i.p. injection resulted in the development of disseminated peritoneal carcinomatosis in SCID, but not wild type C57BL/6 mice. Oophorectomized tumor-prone TgMISIIR-TAg mice developed peritoneal carcinomas with high frequency, rendering them unsuitable as allograft recipients. Orthotopic or pseudo-orthotopic implantation of MOVCAR cells in TgMISIIR-TAg-Low mice resulted in the development of disseminated peritoneal tumors, frequently accompanied by the production of malignant ascites. Tumors arising in the engrafted mice bore histopathological resemblance to human high-grade serous EOC and exhibited a similar pattern of peritoneal disease spread.

CONCLUSIONS

A syngeneic mouse model of human EOC was created by pseudo-orthotopic and orthotopic implantation of MOVCAR cells in a susceptible inbred transgenic host. This immunocompetent syngeneic mouse model presents a flexible system that can be used to study the consequences of altered gene expression (e.g., by ectopic expression or RNA interference strategies) in an established MOVCAR tumor cell line within the ovarian tumor microenvironment and for the development and analysis of preclinical therapeutic agents including EOC vaccines and immunotherapeutic agents.