The growth pattern and microvasculature of pancreatic tumours induced with cultured carcinoma cells

Pancreatic cancer is one of the most frustrating problems in gastroenterological surgery, since there is little we can do to improve the survival of patients with current treatment strategies. If one is to elucidate factors related to carcinogenesis, tumour biology, diagnostics and new treatment modalities of this malignant disease, then it is essential to develop a suitable animal model. In the present study we investigated rat pancreatic tumour growth after intrapancreatic injection of cultured pancreatic carcinoma cells (DSL-6A/C1), originally derived from an azaserine-induced tumour, as well as the features of tumour microcirculation using the microangiography technique. After intrapancreatic inoculation, tumours were detected in 64% of animals. A 1 cm3tumour volume was reached within 20 weeks after inoculation. The tumours were ductal adenocarcinomas. Larger tumours showed invasive growth and spreading into the surrounding tissues, mainly into spleen and peritoneum. Microangiography revealed that the pancreatic tumours had an irregular and scanty vessel network and there were avascular areas in the center of the tumour. The area between normal pancreas and the induced tumour had dense vascularization. Intrapancreatic tumour induction with cultured pancreatic carcinoma cells produced a solid and uniformly growing tumour in Lewis rats and it thus provides a possible model for pancreatic cancer studies. © 2000 Cancer Research Campaig

Microglia used as vehicles for both inducible thymidine kinase gene therapy and MRI contrast agents for glioma therapy

Microglia are phagocytic cells that are chemoattracted by brain tumors and can represent up to 70% of the tumor cell population. To get insight into gene therapy against glioma, we decided to take advantage of those microglia properties and to use those cells as vehicles to transport simultaneously a suicide gene (under the control of a heat-sensitive promoter) and contrast agents to localize them by magnetic resonance imaging before applying any therapeutic treatment. Thymidine kinase (TK) expression and its functionality after gancyclovir administration were investigated. After the heat shock (44°C and 20 min), TK was expressed in 50% of the cells. However, after gancyclovir treatment, 90% of the cells died by apoptosis, showing an important bystander effect. Then, the cells were incubated with new lanthanide contrast agents to check both their potential toxicity and their MR properties. Results indicate that the nanoparticles did not induce any cell toxicity and yield a hypersignal on MR images at 4.7 T. These in vitro experiments indicate that microglia are good candidates as vectors in gene therapy against brain tumors. Finally, microglia containing gadolinium-grafted nanoparticles were injected in the close vicinity of C6 tumor, in a mouse. The hyperintensive signal obtained on in vivo images as well as its retention time show the potential of the novel contrast agents for cellular imaging

Single Reporter for Targeted Multimodal in Vivo Imaging

We have developed a multifaceted highly specific reporter for multimodal in vivo imaging and applied it for detection of brain tumors. A metabolically biotinylated, membrane-bound form of Gaussia luciferase was synthesized, termed mbGluc-biotin. We engineered glioma cells to express this reporter and showed that brain tumor formation can be temporally imaged by bioluminescence following systemic administration of coelenterazine. Brain tumors expressing this reporter had high sensitivity for detection by magnetic resonance and fluorescence tomographic imaging upon injection of streptavidin conjugated to magnetic nanoparticles or fluorophore, respectively. Moreover, single photon emission computed tomography showed enhanced imaging of these tumors upon injection with streptavidin complexed to (111)In-DTPA-biotin. This work shows for the first time a single small reporter ( 40 kDa) which can be monitored with most available molecular imaging modalities and can be extended for single cell imaging using intravital microscopy, allowing real-time tracking of any cell expressing it in vivo