Effect of dose-rate and irradiation geometry on the biological response of normal cells and cancer cells under radiotherapeutic conditions.

Biological efficacy of radiation depends on its energy, dose, dose rate, and on the type of cell irradiated. Changes in the radiation-energy spectrum due to passage through absorbing and scattering media affect the variability of biological responses of the cells. We investigated the impact of photon-radiation dose rate on the biological response of both normal and cancer cells in culture exposed to radiation in various positions (relative to the axis of the radiation beam) and depth of the absorbing medium (water). Human cancer cells (A549 and HCT116) as well as normal human cells (BEAS-2B) were placed in a water phantom at different medium depths (3 cm, 15 cm) and exposed to 6-MV photon radiation delivered at a beam rate of either 100 or 600 MU/min (Monitor Units per minute). The applied dose was 5 Gy. Cells were exposed in the axis and four cm outside the radiation field. Radiation-induced genetic changes were estimated as frequency of micro-nucleated and apopototic-like cells, by use of a cytokinesis-block micronucleus test. A smaller dose rate induced more severe cytogenetic damage (formation of micro-nucleated and apoptotic cells) than a higher dose rate, both in normal and in cancer cells. More micro-nucleated and apoptotic cells were formed at larger depth than at smaller depth. This holds true for both the normal and the two types of cancer cell investigated. The extent of cytogenetic damage arising in cells placed outside the irradiation field is independent of positioning depth and dose rate. Exposure of cells to smaller dose rates and larger depths in water medium resulted in a better ratio of cytogenetic damage to cancer cells irradiated in the beam axis vs damage to normal cells exposed outside the radiation field.

Therapeutic antitumor potential of endoglin-based DNA vaccine combined with immunomodulatory agents.

Therapy targeting tumor blood vessels ought to inhibit tumor growth. However, tumors become refractory to antiangiogenic drugs. Therefore, therapeutic solutions should be sought to address cellular resistance to antiangiogenic therapy. In this regard, reversal of the proangiogenic and immunosuppressive phenotype of cancer cells, and the shift of the tumor microenvironment towards more antiangiogenic and immune-stimulating phenotype may hold some promise. In our study, we sought to validate the effects of a combination therapy aimed at reducing tumor blood vessels, coupled with the abrogation of the immunosuppressive state. To achieve this, we developed an oral DNA vaccine against endoglin. This antigen was carried by an attenuated Salmonella Typhimurium and applied before or after tumor cell inoculation into immunocompetent mice. Our results show that this DNA vaccine effectively inhibited tumor growth, in both the prophylactic and therapeutic settings. It also activated both specific and nonspecific immune responses in immunized mice. Activated cytotoxic T-lymphocytes were directed specifically against endothelial and tumor cells overexpressing endoglin. The DNA vaccine inhibited angiogenesis but did not affect wound healing. In combination with interleukin-12-mediated gene therapy, or with cyclophosphamide administration, the DNA vaccine resulted in reduced microvessel density and lowered the level of Treg lymphocytes in the experimental tumors. This effectively inhibited tumor growth and prolonged survival of the treated animals. Polarization of tumor milieu, from proangiogenic and immunosuppressive, towards an immunostimulatory and antiangiogenic profile represents a promising avenue in anticancer therapy.

A new cholesterol derivative suitable for transfecting certain type of cells in the presence of 10% serum.

We developed a new cationic lipid suitable for use as a DNA carrier in the presence of 10% sera. The novel compound (abbreviated as Arg-Chol) contains cholesterol and a dipeptide consisting of glycine and sterically protected arginine. The efficiency of reporter gene transfection using liposomes based on this new reagent was compared with that of liposomes made with other cationic derivatives of cholesterol. Lipoplexes formulated with the newly synthesized lipid mediate in vitro transfection of B16(F10) murine melanoma cells in the presence of 10% sera more efficiently than in other cell lines and compared with other cholesterol derivatives studied.

Combined therapy of B16(F10) murine melanoma using E. coli cytosine deaminase gene and murine interleukin-4 gene.

This paper summarizes preliminary results of combining suicide gene strategy (E. coli cytosine deaminase gene--CD) with immunotherapy (murine interleukin-4 gene) for treatment of experimental B16(F10) melanomas implanted into C57Bl/6 mice. The best therapeutic results, inhibition of tumor growth and prolonged survival time of treated vs. control mice, were obtained when plasmid expression vectors containing therapeutic genes were transferred into mice via DDAB/DOPE cationic liposome carrier on the third or fourth day following inoculation of mice with cancer cells. Extension of survival time has been noted in the case of two-gene therapy (as compared with one-gene therapy) of tumors which originated from cells transfected in vitro with CD gene and which were subsequently injected in vivo with IL-4-secreting cells. However, no improvement of therapeutic effect was obtained in case of mice treated with a combination of two genes transferred intratumorally with DDAB/DOPE cationic liposomes as compared to mice treated with a single gene only.

The use of cationic liposomes DC-CHOL/DOPE and DDAB/DOPE for direct transfer of Escherichia coli cytosine deaminase gene into growing melanoma tumors.

An attempt was made to use simple cationic liposomes DC-Chol/DOPE and DDAB/DOPE (DC-Chol is 3 beta (N(N',N-dimethylaminoethane) carbamoyl) cholesterol, DDAB is dimethyldioctadecyl ammonium bromide and DOPE is dioleoylphosphatidylethanolamine) for transfer of Escherichia coli cytosine deaminase 'suicide' gene under the control of tissue-specific tyrosinase gene promoter directly into the murine melanoma B16(F10) tumor. Several repeated intratumoral injections of DNA-liposome complexes followed by intraperitoneal administrations of 5-fluorocytosine, which is converted to 5-fluorouracil, caused strong retardation of murine melanoma B16(F10) tumor growth and, in some cases, rejection of the pre-established tumor. The inhibition of tumor growth expressed as the increased survival of mice is better seen in the case of using DNA-DDAB/DOPE complexes as compared to DNA-DC-Chol/DOPE ones. It seems that the observed therapeutic effect appears to result from several factors: 5-fluorouracil generation by transfected cells, liposome toxicity (DDAB is more toxic than DC-Chol and hence more tumor cells are killed), increased transfection efficiency of surviving cancer cells (in this case DDAB is a better transfection agent than DC-Chol) and, finally, the bystander effect which causes destruction of cells untransfected with CD gene by easily diffusible 5-fluorouracil.

On the strategy of using nonviral carriers in cancer gene therapy.

Effectiveness and mode of therapeutic gene delivery in vivo as well as biological safety of such transfer must be improved before widespread application of gene therapy in the clinic becomes possible. Most research has so far focused on recombinant viral delivery systems. Clinical future seems to belong, however, to nonviral delivery systems. Such systems feature DNA complexed to lipid, protein, peptide or polymeric carriers with ligands allowing in vivo tissue targeting by the complex and nuclear translocation of the exogene. Nonviral gene carrier systems are discussed together with strategies of destroying cancer cells.

Introduction of murine Il-4 gene into B16(F10) melanoma tumors by direct gene transfer with DNA-liposome complexes.

Il-4 is a highly pleiotropic cytokine which induces cytotoxic activity when present at the tumor site. Death of tumor cells probably depends on the appearance of an inflammatory infiltrate composed of eosinophils and macrophages. Regression of established tumor masses has been readily observed upon direct intratumor implantation of cells which constitutively produce high amounts of Il-4. We now report a similar potent anti-tumor effect achieved via direct gene transfer, i.e. by injecting Il-4 DNA complexed with cationic liposomes into B16(F10) melanoma tumor in vivo.

Inhibition of Na(+)-glucose cotransport in kidney cortical cells by cadmium and copper: protection by zinc.

Properties of the inhibition of Na(+)-glucose cotransport by Cd2+ in mouse kidney cortical cells have been determined. In no case was any inhibition observed before 3 hr. The extent of inhibition was dependent upon both the concentration of Cd2+ and the length of exposure. Kinetic studies showed that metallothionein mRNA induction by Cd2+ was initiated within 1 hr after incubation with Cd2+ began and peaked by 3-6 hr. Metallothionein protein increased more slowly, beginning at 3 hr and continuing for at least 9 hr. The protein had both Cd2+ and Zn2+ bound to it throughout this period. Nevertheless, a pool of nonmetallothionein Cd2+ appeared after 3 hr, coinciding with the onset of inhibition of Na(+)-glucose cotransport, and increased over the next 9 hr. Pretreatment of cells with Zn2+ protected them from the effects of Cd2+ on Na(+)-glucose cotransport. It delayed the onset of inhibition of transport as well as the extent of inhibition. Detailed analysis of the distribution of Cd2+ and Zn2+ in the soluble fraction of these cells showed that the concentration of non-metallothionein bound Cd2+ was not suppressed by the presence of Zn-metallothionein after the onset of exposure to Cd2+. Incubation of cells with larger concentration of Zn2+ and Cu2+ also inhibited Na(+)-glucose cotransport.

Isolation and characterization of a recombinant heat shock protein of Aspergillus fumigatus.

BACKGROUND: Aspergillus fumigatus, a common environmental fungus, is responsible for a number of lung disorders, including allergy and infection, in human beings. For immunodiagnosis of these diseases, standardized, pure, and relevant antigens are not currently available. METHODS: A complementary DNA library of A. fumigatus was constructed with messenger RNA isolated from 96-hour-old culture of the organism. Fusion proteins expressed with the cDNA were characterized and evaluated. RESULTS: One of the clones, which reacted with both rabbit anti-A. fumigatus serum and a pool of sera from patients with allergic bronchopulmonary aspergillosis, expressed a 65 kd protein of A. fumigatus. The recombinant protein reacted with immunoglobulin E and immunoglobulin G antibodies in the sera from patients with allergic bronchopulmonary aspergillosis. The deduced amino acid sequence of the partially sequenced complementary DNA of the clone is homologous with the hsp 90 family of heat shock proteins in human beings and other organisms. CONCLUSION: The immunodominant nature and the homology to human heat shock proteins suggest a possible role for this protein in protective immunity and autoimmunity.