Low-dose combretastatin A4 phosphate enhances the immune response of tumor hosts to experimental colon carcinoma.

PURPOSE: Although there is a need to enhance the therapeutic efficiency in cancer by combining immunotherapeutic procedures with other therapy, combination with chemotherapy is complicated due to immunosuppressive effects of most chemotherapeutic drugs. The purpose of this investigation was to study whether combining tumor cell immunization with the vascular targeting drug combretastatin A4 phosphate (CA4P) would enhance tumor retardation and/or affect the antitumor immune response. EXPERIMENTAL DESIGN: Rats with intrahepatic colon carcinoma were immunized weekly with IL-18/IFNgamma-transfected tumor cells, starting day 9, and were treated with a low-dose CA4P (2 mg/kg, 5 days a week starting day 7). The effect of CA4P was studied on tumor growth and on immune reactivity in vitro. RESULTS: Rats with preexisting tumor, immunized and treated with low-dose CA4P, had a significantly retarded tumor growth compared with rats receiving CA4P or immunization alone. Splenocytes from rats treated with this combination had a significantly enhanced antitumor immune response compared with splenocytes from control rats. Exposure of nonadherent splenocytes to CA4P in vitro did not enhance their proliferation. However, 3-hour pretreatment of adherent splenocytes with 0.3 microg/mL CA4P significantly enhanced proliferation and IFNgamma production of admixed nonadherent splenocytes, partly due to nitric oxide reduction. Combining the nitric oxide synthase inhibitor N-nitro-l-arginine methyl ester with CA4P and immunization further retarded tumor growth. CONCLUSION: Concomitant treatment of rats with progressively growing tumor with immunization and low-dose CA4P significantly enhances the therapeutic effect as compared with either treatment alone and results in an enhanced antitumor immune reactivity.

Neural progenitor cell lines inhibit rat tumor growth in vivo.

Current therapies for gliomas often fail to address their infiltrative nature. Conventional treatments leave behind small clusters of neoplastic cells, resulting in eventual tumor recurrence. In the present study, we have evaluated the antitumor activity of neural progenitor cells against gliomas when stereotactically injected into nucleus Caudatus of Fisher rats. We show that the rat neural progenitor cell lines HiB5 and ST14A, from embryonic hippocampus and striatum primordium, respectively, are able to prolong animal survival and, in 25% of the cases, completely inhibit the outgrowth of N29 glioma compared with control animals. Delayed tumor outgrowth was also seen when HiB5 cells were inoculated at the site of tumor growth 1 week after tumor inoculation or when a mixture of tumor cells and HiB5 cells were injected s.c. into Fisher rats. HiB5 cells were additionally coinoculated together with two alternative rat gliomas, N32 and N25. N32 was growth inhibited, but rats inoculated with N25 cells did not show a prolonged survival. To evaluate the possibility of the involvement of the immune system in the tumor outgrowth inhibition, we show that HiB5 cells do not evoke an immune response when injected into Fisher rats. Furthermore, the rat neural progenitor cells produce all transforming growth factor beta isotypes, which could explain the observed immunosuppressive nature of these cells. Hence, some neural progenitor cells have the ability to inhibit tumor outgrowth when implanted into rats. These results indicate the usefulness of neural stem cells as therapeutically effective cells for the treatment of intracranial tumors.

Angiogenesis, endothelial cell functions, and tumor cell growth in biodegradable and nonbiodegradable devices.

Development of tissue engineering creates multiple potentials for clinical treatment and scientific research. Biodegradable collagen matrices have been found to support simultaneous autotransplantation of hepatocytes after major liver resection. Dynamic angiogenesis in biodegradable devices (BDD) and nondegradable devices (NDD) transplanted into the renal subcapsule and subcutaneous tissue was measured by the distribution of radiolabeled red blood cells and serum albumin. The circulation, microvascular integrity, and capacities of endothelial cells (adhesion, proliferation, and migration) were investigated within 2 weeks after subcutaneous transplantation of both devices. Patterns of tumor cell growth in both devices were morphologically studied. After subcutaneous transplantation, significant angiogenesis was noted at 1 week in BDD implants and from 2 weeks and on in NDD implants, with an increase in implant blood and plasma volumes. Leakage index of radiolabeled albumin in NDD implants was significantly higher than in BDD implants, while the leakage index 2 weeks after BDD implant was similar to that in subcutaneous tissues. Adhesion, proliferation and migration rates of endothelial cells isolated from both devices were higher than from subcutaneous tissues. Endothelial proliferation and migration rates in BDD implants were significantly higher at 1 week, while in NDD at 2 weeks. Tumor cells migrated and grew on the top surface of NDD with a flattened shape, while growing within the BDD forming a round mass. Endothelial capacities, angiogenetic procedure, and biological and physical characteristics of the device contribute to patterns of tumor cell growth in the device. Biodegradable collagen matrix with three-dimensional structure is suitable for simultaneous transplantation with cells without prevascularization.

Posintro™-HBsAg, a modified ISCOM including HBsAg, induces strong cellular and humoral responses.

To improve the hepatitis B vaccines on the market new adjuvant systems have to substitute aluminium. In this study the hepatitis B surface antigen (HBsAg) was incorporated into a novel adjuvant system, the Posintro™, a modification of the traditional immune stimulatory complexes (ISCOMs). This new HBsAg vaccine formulation, Posintro™-HBsAg, was compared to two commercial hepatitis B vaccines including aluminium or monophosphoryl lipid A (MPL) and the two adjuvant systems MF59 and QS21 in their efficiency to prime both cellular and humoral immune responses. The Posintro™-HBsAg induced the strongest humoral response with high titers of HBsAg specific antibody, high number of antigen specific B-cells and a strong T helper 1 (Th1) antibody profile when compared to the other adjuvant formulations. The Posintro™-HBsAg was also a strong inducer of cellular immune responses with induction of delayed type hypersensitivity (DTH) reaction and CD4(+) T-cell proliferation. In addition, Posintro™-HBsAg was the only vaccine tested that also induced a strong cytotoxic T lymphocyte (CTL) response, with high levels of antigen specific CD8 T-cells secreting IFN-gamma mediating cytolytic activity. The results demonstrate that this novel experimental vaccine formulation, the Posintro™-HBsAg, is strongly immunogenic and can induce both class I and class II responses in experimental animals. This shows promise both for the protection against hepatitis B virus infection and as a potential therapeutic vaccine.

Chemokine-directed migration of tumor-inhibitory neural progenitor cells towards an intracranially growing glioma.

We have earlier shown that the rat neural progenitor cell line HiB5 is capable of suppressing intracranial growth of glioma cells in Fisher rats. Unlike some neural progenitor cells, HiB5 cells have not shown homing capacity towards glioma cells growing intracranially. In this study, we have genetically modified HiB5 progenitor cells to over-express the chemokine receptor CXCR3. We show that the introduced receptor is functionally responding to ligand stimulation with increased phosphorylation levels of ERK and SAPK/JNK and a transcriptional response of an AP-1 reporter system introduced into HIB5 cells. These transfected progenitor cells migrate in vitro in response to IP-10 and I-TAC. Further, we show an enhanced in vivo migration of the CXCR3 transfected HiB5 cells over the corpus callosum towards an IP-10 and I-TAC expressing glioma, as compared to wild type HiB5 cells. Our data indicate that it is possible to take advantage of chemokines natural capacity to initiate migratory responses, and to use this ability to enhance tumor-inhibitory neural progenitor cells to target an intracranially growing glioma.