[Show abstract][Hide abstract] ABSTRACT: Conventional cancer treatments often have little impact on the course of advanced pancreatic cancer. Although cancer gene therapy with adenoviruses is a promising developmental approach, the primary receptor is poorly expressed in pancreatic cancers which might compromise efficacy and thus targeting to other receptors could be beneficial. Extended stealth delivery, combination with standard chemotherapy or circumvention of host antiadenoviral immune response might improve efficacy further. In this work, capsid-modified adenoviruses were studied for transduction of cell lines and clinical normal and tumor tissue samples. The respective oncolytic viruses were tested for oncolytic activity in vitro and in vivo. Survival was studied in a peritoneally disseminated pancreas cancer model, with or without concurrent gemcitabine while silica implants were utilized for extended intraperitoneal virus delivery. Immunocompetent mice and Syrian hamsters were used to study the effect of silica mediated delivery on antiviral immune responses and subsequent in vivo gene delivery. Capsid modifications selectively enhanced gene transfer to malignant pancreatic cancer cell lines and clinical samples. The respective oncolytic viruses resulted in increased cell killing in vitro, which translated into a survival benefit in mice. Early proinfammatory cytokine responses and formation of antiviral neutralizing antibodies was partially avoided with silica implants. The implant also shielded the virus from pre-existing neutralizing antibodies, while increasing the pancreas/liver gene delivery ratio six-fold. In conclusion, capsid modified adenoviruses would be useful for testing in pancreatic cancer trials. Silica implants might increase the safety and efficacy of the approach.
International Journal of Cancer 07/2012; 131(1):253-63. DOI:10.1002/ijc.26370 · 5.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Despite promising preclinical results, the clinical benefits of cancer gene therapy have been modest heretofore. The main obstacle continues to be the level and persistence of gene delivery to sufficiently large areas of the tumor. One approach for overcoming this might entail extended local virus release. We studied the utility of silica gel monoliths for delivery of adenovirus to advanced orthotopic gastric and pancreatic cancer tumors. Initially, the biochemical properties of the silica-virus matrix were studied and nearly linear release as a function of time was detected. Virus stayed infective for weeks at +37 degrees C and months at +4 degrees C, which may facilitate storage and distribution. In vivo, extended release of functional replication deficient and also replication-competent, capsid-modified oncolytic viruses was seen. Treatment of mice with pancreatic cancer doubled their survival (P<0.001). Also, silica gel-based delivery slowed the development of antiadenovirus antibodies.
[Show abstract][Hide abstract] ABSTRACT: Amorphous, sol-gel derived SiO2 are known to biocompatible and bioresorbable materials. Bioresorbable materials have potential applications as implants or
injectable matrices in the controlled delivery of biologically active agents in the living tissue. Bioresorbable matrices
provide desirable properties, e.g., extra removal operations that have to be done with biostable matrices are avoided and
the release of large therapeutic molecules can be controlled by matrix degradation rather than by diffusion. New important
groups of drugs, such as biotechnically-produced peptides and proteins, are potential to be encapsulated in bioresorbable
SiO2, because they are typically larger in size and their direct oral administration without protecting matrix is difficult due
to digestion. The methods to achieve a wide range of SiO2 bioresorption rates (from days to months) are introduced in this study. This is done by a “conventional” alkoxy-based sol-gel
method at protein-friendly conditions by adjusting the precursor ratios, aging of the sol and by using different preparation
methods (casting, spray-drying and freeze-drying). The prepared morphologies include implantable monolithic sticks and injectable
microspheres. The importance of chemical structure is shown in comparison with the specific surface area and pore volume.
Journal of Sol-Gel Science and Technology 10/2005; 36(2):147-156. DOI:10.1007/s10971-005-5286-1 · 1.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sol–gel derived SiO2 have been shown to be biocompatible and bioresorbable and they have potential use in living tissue, e.g., in bone regeneration and controlled drug delivery. Bioresorbable SiO2 is a potential alternative for the controlled delivery of large biologically active agents, such as proteins and peptides. The aim was to prepare SiO2 matrices with varying bioresorption rate at protein-compatible conditions and to characterize the chemical features of the matrices. SiO2 was prepared in two morphologies, monoliths by casting and microparticles by spray drying. A model protein was encapsulated into the SiO2 matrices. Materials were carefully characterized with FTIR- and Raman spectroscopy, TGA-FTIR, solid state 29Si MAS NMR, SEM and matrix dissolution was measured in simulated physiological conditions. It is shown that both fast and slowly dissolving SiO2 matrices could be prepared at protein-compatible conditions. Fast-dissolving SiO2 microparticles contained a high proportion of Q3 and a low portion of Q4 indicating poor cross-linking of SiO2 species and an increased amount of hydrolysable terminal groups. Spectroscopic techniques and TGA-FTIR show that organic residues and moisture are left in the matrices. The amount of organic residues is larger in the fast-dissolving SiO2 matrices, but it does not significantly affect the bioresorption rate.
[Show abstract][Hide abstract] ABSTRACT: Silica gel is a solid, non-toxic 100 % biodegradable matrix suitable for delivery of small molecules and proteins as implant material in vivo. Here, silica gel was investigated as carrier of adenoviral vectors in controlled and localized gene delivery. Recombinant adenoviruses coding for beta-galactosidase (lacZ) were encapsulated in silica gel prepared from water and tetraethoxysilane by sol-gel method in molar ratio of 52.5:1. The sol-gel process was modified so that addition of adenoviruses was possible into the liquid sol. After the gel formation the adenoviruses became encapsulated inside solid gel structure. Monolithic buttons of adenovirus-loaded silica gels for in vitro tests were soaked in PBS, and incubated at +37 °C, 5 % CO2 or in RT, and cultured with human skin fibroblasts for different periods of time up to 32 days. Transduction of fibroblasts by adenoviruses released from silica gel was determined by X-gal staining. In parallel, adenoviruses were incubated in solution at +37 °C, and the virus titres in conditioned media were determined daily. In vivo experiments were carried out by implanting the adenovirus-loaded silica gel s.c. into the neck of mice. At time points of 3, 7, 14 and 21 days animals were sacrificed, tissue samples were collected and stainedby X-gal. At the same time points, blood samples were obtained and antibodies against adenovirus serotype 5 were determined.The titre of infective adenoviruses incubated in solution at +37 °C was reduced by 50% in 1.2 days and at 6 days no infective viruses could be detected. In comparison, adenoviruses released from silica gel were able to infect fibroblasts in culture even after 28 days at +37 °C, although the infectivity decreased slightly during storage. Adenoviruses released from silica gel kept at room temperature for 26 days showed no decrease in transduction capacity. Adenoviruses were also released from silica gel in vivo and beta-galactosidase positive cells were detected in tissue surrounding the implant and the number and area of transduced cells was larger compared to the positive controls injected subcutaneously with same adenoviral dose. Resorption of silica gel could be seen 14 days after implantation, and after 21 days the silica gel was entirely resorbed. Development of anti-adenovirus antibodies was delayed in mice implanted with the silica embedded adenoviruses, as compared to mice injected subcutaneously with adenovirus. Elevated levels of anti-adenovirus antibodies were detected in mice 7 days after dermal injection of adenovirus, whereas the levels in implanted mice were similar as in the negative controls. These results show, that silica gel can be used for targeted and effective adenoviral gene delivery to cells in vitro and in vivo with delayed host immune response to viral vector.