Microencapsulated, CYP2B1-transfected cells activating ifosfamide at the site of the tumor: the magic bullets of the 21st century.

BACKGROUND: Conventional chemotherapy of pancreatic carcinoma is only marginally effective. This is in part due to the severity of side effects following systemic administration of the cytostatic drug. The aim was to create a therapeutic tool allowing the targeting of the conversion site of a cytotoxic prodrug to the site of the tumor. This was realized by transfection of the CYP2B1 gene, the major ifosfamide-converting P450 enzyme, in cells with subsequent microencapsulation and administration of these microcapsules to or into the tumor. The enzyme activity (resorufin assay) remained stable for weeks in vitro and in vivo within the microencapsulated CYP2B1-expressing cells. We demonstrated a significant antitumor effect of the intratumorally injected capsules against xenotransplanted human pancreatic carcinomas in the nude mouse. Angiographic experiments in the pig confirmed the feasibility of an intraarterial placement of the capsules into the pancreas. A clinical protocol was established and approved. PATIENTS, MATERIAL AND METHODS: L293 cells were transfected with the CYP2B1 gene, microencapsulated (diameter 0.7 mm) under GCP conditions and packed sterile. Patients with confirmed inoperable adenocarcinoma of the pancreas underwent angiography, and capsules were injected into a vessel leading into the tumor. The patients were monitored for 48 h to exclude allergic reactions or pancreatitis. A day later, ifosfamide was administered for three consecutive days to be repeated on days 21-23. The patients were followed up for 5 months. RESULTS: A total of 17 patients were enrolled. The patients tolerated the procedure without any complications. No allergic reactions or pancreatitis were encountered. Chemotherapy was uneventful. All patients had stable disease, and two patients a partial remission. The median survival was 44 weeks which compared favorably with that of a historical control group (22 weeks). CONCLUSIONS: The intraarterial administration of microcapsules for targeted chemotherapy was well tolerated. Control of local tumor growth was achieved.

Combined therapy of experimental pancreatic cancer with CYP2B1 producing cells: low-dose ifosfamide and local tumor irradiation.

Local therapy of pancreatic cancer with microencapsulated CYP2B1-producing cells and ifosfamide showed an effect both on the primary tumor and on distant metastatases. This possibly represents a consequence of the activation of immune response. Other studies have demonstrated that local tumor irradiation leads to the activation of the intratumoral lymphocyte infiltration. The aim of our study was to investigate the efficacy of the combined therapy with low-dose irradiation, ifosfamide and CYP2B1-producing cells. Syngenic pancreatic cancer was induced in 38 Lewis-rats by subcutaneous inoculation of 1 x 10(6) (DSL6A) tumor cells. Microencapsulated CYP2B1-producing cells were injected peritumorally 10--12 weeks after tumor implantation. Animals were randomized to the following groups: 1) control (NaCl, 1 ml i.p.), 2) ifosfamide (50 mg/kg, i.p., (3x/week), 3) local irradiation with 5 Gy and 4) ifosfamide plus irradiation. The tumor growth was monitored for 3 weeks. The tumor infiltration with CD4+, CD8+, NK-cells, microvessel density and proliferation rates were investigated by immunohistochemistry. Cytokine plasma level for TNF-alpha were measured by ELISA. Seven of 9 animals in the group of combined therapy showed an objective response to the therapy. The therapy with ifosfamide or radiation alone showed 5 and 3 responders, respectively. The mean tumor volume was significantly reduced after combined ifosfamide plus radiation therapy in the first week, whereas monotherapy with ifosfamide or radiation significantly decreased tumor growth earliest after 2 and 3 weeks, respectively. The high plasma level of TNF-alpha in the control group was significantly reduced after combined ifosfamide/irradiation treatment. The lymphocyte infiltration and tumor proliferation were not significantly different between the groups. Microvascular density was significantly increased after ifosfamide and ifosfamide plus irradiation therapy. The combination of ifosfamide/CYP2B1-producing cells and irradiation showed an earlier therapeutical effect on the growth of rat pancreatic cancer than the irradiation or ifosfamide alone. There was no evidence of late activation of lymphocyte infiltration and PCNA-positive tumor cells.

Encapsulated cells producing retroviral vectors for in vivo gene transfer.

BACKGROUND: Because gene therapy of the future will primarily take an in vivo approach, a number of problems associated with its current implementation exist. Currently, repeated delivery of a vector in vivo is necessary to ensure adequate transfer of the therapeutic gene. This may lead to the development of an immune response against the vector, thus interfering with gene delivery. To circumvent this problem, retroviral vector packaging cells that permanently produce recombinant retroviral vector particles have been encapsulated. METHODS: Vector (pBAG)-producing amphotropic cells were encapsulated in beads composed of polymerized cellulose sulphate. These capsules were analysed in vitro for expression of the vector construct using X-gal staining, as well as for the release of particles by performing RT-PCR from culture supernatant. Infectivity studies were performed in vitro and in vivo. The latter was assayed using histological sections of the microcapsule and the surrounding area stained for beta-galactosidase activity and by RT-PCR. RESULTS: In culture, the virus-producing cells inside the capsules remained viable and released virus into the culture medium for at least 6 weeks. To test whether these capsules, upon implantation into mice, also release vector virions that infect the surrounding cells, two different models were used. In the first, capsules were implanted in the fat pad of the mammary gland of Balb/c mice. The capsules were well tolerated for at least 6 weeks and a self-limiting inflammatory reaction without any other gross immune response was observed during this period. Furthermore, the virus-producing cells remained viable. In the second model, SCID mice were immunologically reconstituted by subcutaneous implantation of thymus lobes from MHC-identical Balb/c newborn mice and gene transfer into lymphoid cells was achieved by retroviral vectors released by co-implanted capsules. CONCLUSION: The implantation of such capsules containing cells that continually produce retroviral vector particles may be of use for in vivo gene therapy strategies. The data presented demonstrate the feasibility of the concept.

Intra-arterial instillation of microencapsulated, Ifosfamide-activating cells in the pig pancreas for chemotherapeutic targeting.

BACKGROUND: The therapeutic efficacy of intratumoral instillation of genetically engineered, CYP2B1-expressing, microencapsulated cells in combination with ifosfamide had been previously demonstrated in xenografted human pancreatic ductal carcinomas [Gene Ther 1998;5:1070-1078]. Prior to a clinical study, the feasibility of an intra-arterial application of microencapsulated cells to the pancreas and its consequences to the organ had to be evaluated. MATERIAL AND METHODS: Microencapsulated, CYP2B1-producing cells were instilled both in vivo (transfemoral angiographical access) and in vitro (perfusion model) in the splenic lobe of the pig pancreas. In vivo, animals were monitored clinically for 7 days, then treated with ifosfamide and sacrificed. In vitro, ifosfamide was administered intra-arterially. RESULTS: In all animals, 100 microcapsules could be instilled safely via the femoral route without clinical, biochemical or histological signs of pancreatitis. Histological examination revealed partial obstruction of small arteries by the capsules, without causing any parenchymal damage. In vitro, instillation reduced blood flow by half. Ifosfamide, also in combination with the capsules, did not add any damage to the pancreas. CONCLUSION: Intra-arterial instillation of microencapsulated cells to the pig pancreas is feasible and safe. Neither pancreatitis, foreign body reactions nor circulatory disturbances were observed. Clinical application of this genetically enhanced chemotherapeutic method seems possible.