Intratracheal injection of adenovirus containing the human MnSOD transgene protects athymic nude mice from irradiation-induced organizing alveolitis

PURPOSE

A dose and volume limiting factor in radiation treatment of thoracic cancer is the development of fibrosis in normal lung. The goal of the present study was to determine whether expression prior to irradiation of a transgene for human manganese superoxide dismutase (MnSOD) or human copper/zinc superoxide dismutase (Cu/ZnSOD) protects against irradiation-induced lung damage in mice.

METHODS AND MATERIALS

Athymic Nude (Nu/J) mice were intratracheally injected with 10(9) plaque-forming units (PFU) of a replication-incompetent mutant adenovirus construct containing the gene for either human MnSOD, human copper/zinc superoxide dismutase (Cu/ZnSOD) or LacZ. Four days later the mice were irradiated to the pulmonary cavity to doses of 850, 900, or 950 cGy. To demonstrate adenoviral infection, nested reverse transcriptase-polymerase chain reaction (RT-PCR) was carried out with primers specific for either human MnSOD or Cu/ZnSOD transgene on freshly explanted lung, trachea, or alveolar type II cells, and immunohistochemistry was used to measure LacZ expression. RNA was extracted on day 0, 1, 4, or 7 after 850 cGy of irradiation from lungs of mice that had previously received adenovirus or had no treatment. Slot blot analysis was performed to quantitate RNA expression for IL-1, tumor necrosis factor (TNF)-alpha, TGF-beta, MnSOD, or Cu/ZnSOD. Lung tissue was explanted and tested for biochemical activity of MnSOD or Cu/ZnSOD after adenovirus injection. Other mice were sacrificed 132 days after irradiation, lungs excised, frozen in OCT, (polyvinyl alcohol, polyethylene glycol mixture) sectioned, H&E stained, and evaluated for percent of the lung demonstrating organizing alveolitis.

RESULTS

Mice injected intratracheally with adenovirus containing the gene for human MnSOD had significantly reduced chronic lung irradiation damage following 950 cGy, compared to control mice or mice injected with adenovirus containing the gene for human Cu/ZnSOD or LacZ. Immunohistochemistry for LacZ protein in adenovirus LacZ (Ad-LacZ)-injected mice demonstrated expression of LacZ in both the upper and lower airway. Nested RT-PCR showed lung expression of MnSOD and Cu/ZnSOD for at least 11 days following infection with each respective adenovirus construct. Nested RT-PCR using primers specific for human MnSOD demonstrated increased expression of the human MnSOD transgene in the trachea and alveolar type II cells 4 days after virus injection on the day of irradiation. At this time point, increased biochemical activity of MnSOD and Cu/ZnSOD respectively, was detected in lungs from these two adenovirus groups, compared to each other or to control or adenovirus LacZ mice. Slot blot analysis of RNA from lungs of mice in each group following 850 cGy irradiation demonstrated decreased expression of mRNA for interleukin-I (IL-1), TNF-alpha, and transforming growth factor-beta (TGF-beta) in the MnSOD adenovirus-injected mice, compared to irradiated control, LacZ, or Cu/ZnSOD adenovirus-injected, irradiated mice. Mice receiving adenovirus MnSOD showed decreased organizing alveolitis at 132 days in all three dose groups, compared to irradiated control or Ad-LacZ, or Ad-Cu/ZnSOD mice.

CONCLUSIONS

Overexpression of MnSOD in the lungs of mice prior to irradiation prevents irradiation-induced acute and chronic damage quantitated as decreased levels of mRNA for IL-1, TNF-alpha, and TGF-beta in the days immediately following irradiation, and decrease in the percent of lung demonstrating fibrosis or organizing alveolitis at 132 days. These data provide a rational basis for development of gene therapy as a method of protection of the normal lung from acute and chronic sequelae of ionizing irradiation.

Redox gene therapy protects human IB-3 lung epithelial cells against ionizing radiation-induced apoptosis

Toxicity to nontumor-derived tissue has proven to be a significant obstacle in achieving therapeutic levels of gamma irradiation in the treatment of cancer. The formation of reactive oxygen species (ROS) such as superoxide radicals (O2-) following irradiation is thought to be a major determinant of cellular damage. To this end, we describe the generation of two recombinant adenoviral vectors expressing the radical-scavenging enzymes MnSOD and CuZnSOD to test therapeutic strategies of radioprotection. Using a human lung epithelial cell line (IB-3), we have demonstrated that infections with both Ad.CMVMnSOD or Ad.CMVCuZnSOD significantly increase both the levels of SOD protein and enzymatic activity as compared to control cells. This increase in SOD expression reduced the level of apoptosis at 72 hr post-irradiation by 50% as compared to mock- or Ad.CMVLacZ-infected cells. Such studies provide the foundation for radioprotective gene therapies in the treatment of cancer.

Induction of serum amyloid A inflammatory response genes in irradiated bone marrow cells

The molecular mechanisms underlying radiation-induced defects in the bone marrow which may contribute to the development of radiation-induced hematopoietic disorders such as aplastic anemia and leukemia are not known. Persistent changes in gene expression were examined after exposure of cells of a murine bone marrow stromal cell line to ionizing radiation. Analysis of mRNA transcript levels by differential display led to the identification of a band, C122, which increased in abundance 1 week after exposure. Northern blot hybridization verified these results and revealed a 12-fold increase in abundance of this message for up to 3 weeks after irradiation in vitro. DNA sequence analysis identified clone C122 as murine serum amyloid A 3 (Saa3), a member of the Saa family of acute-phase or inflammatory response genes. Saa message levels were then examined in vivo in the bone marrow of mice exposed to total-body irradiation. Semi-quantitative reverse transcription-polymerase chain reaction revealed a 15-20-fold increase in Saa3 message levels in the bone marrow of irradiated mice from 3 days to 2 weeks after exposure. Saa3 message levels continued to be 2-3-fold above control for up to 28 weeks in vivo. Two additional members of the murine Saa gene family, Saa1 and Saa2, were also detected in irradiated bone marrow. The expression of SAA1 and SAA2 was also detected in irradiated cells of human bone marrow stromal cell lines in vitro. These results suggest that SAA genes are involved in the radiation response in the bone marrow, but their role in the recovery of the marrow after irradiation or in the development of radiation-induced hematopoietic disorders remains to be established. Additionally, the persistent radiation-induced increase in expression suggests the potential utility of using SAA3 transcript levels as a molecular marker of past radiation exposure.

Evaluation of laminin peptide fragments labeled with indium-111 for the potential imaging of malignant tumors

The laminin peptide fragments GYIGSR-NH2 and CDPGYIGSR-NH2 are known to bind to a 67-kDa laminin receptor. This receptors is understood to be expressed at higher than normal levels in malignant tumor cells, particularly those of breast and colon carcinomas. Peptides DTPA-GYIGSR-NH2 (1), DTPA-(GYIGSR-NH2)2 (2), DTPA-CDPGYIGSR-NH2 (3), DTPA-(CDPGYIGSR-NH2)2 (4), and negative control DTPA-GAGAGA-NH2 (5) were prepared by solid-phase peptide synthesis. All five DTPA-conjugated peptides were subsequently radiolabeled with 111In and their tissue distribution evaluated in mice bearing C3H tumors. 111In-3 and 111In-4 showed the highest specific tumor localization. These preliminary data support further study of radiolabeled petide fragments for the potential detection of malignant tumors of the breast and other organs.

Effect of radiation on interstitial fluid pressure and oxygenation in a human tumor xenograft

Elevated interstitial fluid pressure (IFP) is a pathophysiological characteristic of most human and experimental tumors and may be responsible, in part, for the poor distribution of blood-borne therapeutic agents and low blood flow rate in tumors. Recent data in cervical carcinomas in patients suggest that fractionated radiation can lower tumor IFP and increase oxygen partial pressure (pO (2)) in some patients. The goals of this study were to find the minimum dose of radiation required to modulate IFP and pO(2) and to determine the time course of IFP changes due to radiation in a preclinical model. Xenografts of the LS174T human colon adenocarcinoma were grown in the right flank of nude (BALB/c) mice. IFP and pO(2) were measured before and 24 h after graded doses of irradiation. The mean +/- SD initial IFP in untreated tumors was 12.9 +/- 0.5 mm Hg (n=109), and the range was 3.0 to 40.3 mm Hg. The mean +/- SD and median initial pO(2) were 20.2 +/- 2.4 and 11.9 mm Hg, respectively (n=37). IFP and pO(2) were independent of tumor size. Fractionated radiation lowered IFP by 2.5 mm Hg when the total dose was 10 or 15 Gy (P<0.05), but IFP did not change in the controls or the 5-Gy radiation group (P>0.05). Irradiation increased the proportion of tumors at higher oxygen tensions when compared to control tumors. The IFP and tumor volumes were followed for up to 10 days after a single dose of 10, 20, or 30 Gy of irradiation. IFP decreased for all treatment groups. The decrease was most significant for the group receiving 30 Gy. On day five following irradiation, the IFP had decreased by 35%. The changes in IFP and pO(2) occurred before any macroscopic changes in tumor volume could be observed. The radiation-induced decrease in IFP could be, in part, responsible for the increased uptake of monoclonal antibodies following single or fractionated radiation that has been reported in the literature.

Stromal cell involvement in leukemogenesis and carcinogenesis

There is increasing evidence that the supportive cells (stromal cells) in nearly all organs containing cellular self-renewal systems are involved in carcinogenesis. One body of evidence specific to irradiation leukemogenesis documents the role of irradiated murine stromal cells in the cell biologic changes associated with evolution of leukemia in cocultivated, nonirradiated stem cells. Stem cell phenotypic changes that have been documented include upregulation of cell surface c-fms, downregulation of growth requirement for obligatory growth factors, and the appearance of novel transcripts detected by differential display. A second body of evidence documents the potential role of stromal cells functioning as biologic tumor promoters through their release of reactive oxygen species (ROS), and production of altered adhesion molecules or growth factors during the chronic response to chemical or physical carcinogens. These molecular biologic mechanisms, potentially operative in stromal cells, can block apoptosis and induce DNA strand breaks in closely associated self-renewing stem cells. In an in vivo model of irradiation effects on lung stromal cells, we have irradiated the lungs of control C57BL/6J mice or other mice with orthotopic Lewis lung tumors and shown that TGF-beta release is increased following irradiation. The TGF-beta increase by irradiation may specifically be inhibited by administering an inhalation plasmid liposome mixture containing a transgene for human manganese superoxide dismutase prior to irradiation. An appreciation of the role of stromal cells in leukemogenesis and carcinogenesis may also be very relevant to the design of new therapeutic strategies for treatment of cancer, particularly since current strategies focus on eradication of stem cell transformants and do not rigorously address the persistence of surviving stromal cells.

Role of bone marrow stromal cells in irradiation leukemogenesis

The role of bone marrow stromal cells of the hematopoietic microenvironment in ionizing-irradiation leukemogenesis is a focus of current investigation. Evidence from recent in vitro and in vivo experiments suggests that damage by slowly proliferating cells of the hematopoietic microenvironment contributes to the sustained survival of irradiation-damaged hematopoietic progenitor cells/stem cells and can contribute to the selection and proliferation of a malignant clone. The molecular mechanism of the interaction of irradiated stromal cells with attached hematopoietic cells has been difficult to evaluate. Irradiated bone marrow stromal cell line D2XRII demonstrated altered patterns of fibronectin splicing and increased expression of several transcriptional splice variants of macrophage-colony-stimulating factor. Differential display has revealed specific radiation-induced gene transcripts which persist after irradiation of stromal cells in vitro or in vivo. In recent experiments, we demonstrated that irradiation of mouse bone marrow stromal cell line D2XRII induces release of significant levels of transforming growth factor (TGF)-beta into the tissue culture medium despite the lack of a detectable increase in TGF-beta mRNA. Since TGF-beta is known to induce reactive oxygen species (ROS), we tested how a target hematopoietic cell line, responsive to ROS by up-regulation of a transgene for an antioxidant protein, responded to cocultivation with irradiated bone marrow stromal cells. Bone marrow stromal cell line GPIa/GBL, derived from long-term bone marrow culture of a C57BL/6J-GPIa mouse, was irradiated in vitro and then cocultured with the interleukin (IL)-3-dependent hematopoietic progenitor cell line 32D cl 3, or with each of several subclonal lines expressing a transgene for human manganese superoxide dismutase (MnSOD). Cobblestone island formation, as a measure of adherence and proliferation by 32D-MnSOD clones in the presence or absence of IL-3, was increased with irradiated compared to control GPIa cells. Furthermore, using a fluorescent dye which detects ROS, hematopoietic cells cocultivated with irradiated stromal cells demonstrated higher levels of intracellular ROS than cells cocultivated and forming cobblestone islands on nonirradiated stromal cells. Since ROS are known to induce mutations in hot spots in the p53 gene, it appears worthwhile to investigate a potential mechanism for irradiated stromal cell induction of hematopoietic stem cell transformation through ROS-induced mutations. The present cell culture and molecular biology techniques provide new methods to analyze the effects of irradiated stromal cells on closely attached hematopoietic stem cells during irradiation leukemogenesis.

Dosimetric consequences of 10B(n, alpha)7Li reaction occurring at the cellular membrane

PURPOSE

Microdosimetric expectations of Boron contents are extracted from a CRAY-Monte Carlo simulation of the nuclear reaction 10B(n, alpha)7Li as it occurs on a boronated membrane of a model cell and as the reaction fragments (alpha and Li) traverse into the cellular nucleus.

METHODS AND MATERIALS

The present microdosimetry calculation is based upon the assumption that the therapeutic advantage of boron neutron capture therapy (BNCT), while depending upon the RBE and LET of the reaction particles, is equally dependent on the boron carrier preferential localization to tumor tissue, and the boron selectivity to cancerous cells and its specificity within subcellular compartments. In particular, boron fixes to cell membrane as it ought to, using monoclonal antibodies. The present Monte Carlo simulation computes stochastic expectations of alpha/Li energy depositions to the nucleus in a uniformly boronated membrane shell of a spherical cell. Differential energy gain was deduced from the stochastic energy depositions in events of neutron reactions with membrane boron compared against those with natural elements (O, H, N) in the cell.

RESULTS

Microdosimetry data are presented in terms of specific energy (keV/micron3) and lineal energy (keV/micron) functions of the nucleus-to-cell volume ratios (NCVR). When folded with the geometric boron content and accounting for background reaction energies, the distributions yield effective energy gain to the cell nucleus per neutron capture event. Boron amount required to yield these energy gains are found to be of the order of picograms of boron per gram of cell mass.

CONCLUSION

The boron content as inferred by the present Monte Carlo microdosimetry compares well with that deliverable by present pharmacokinetic means, but are orders of magnitude (mu-grams) less than those deduced previously from anthropomorphic macrodosimetry.

A novel method for the non-chromatographic purification of technetium-99m-labeled monoclonal antibodies: a study with B72.3 monoclonal antibody

A cleaning resin has been developed for the non-chromatographic purification of 99mTc-labeled monoclonal antibodies (MAbs). The resin used is a modified form of thiopropylsepharose 6B resin, in which its sulfhydryl groups have been tinylated with stannous chloride. The method requires only simple stirring of the radiolabeling reaction mixture with this tinylated resin and subsequent separation of it from the resin by filtration to obtain a 99mTc-labeled MAb of radiopharmaceutical purity. The method provides an alternative to chromatographic purification of the radiolabeled MAb (i.e. gel filtration or anion exchange chromatography) which has been used in other 99mTc-MAb preparations. For comparison studies, we labeled the B72.3 MAb with NeoRx's diamide dimercaptide chelate radiolabeling kit, split the reaction mixture into two equal portions and then purified one portion with anion exchange chromatography (NeoRx's chosen method) while the other portion was purified with our cleaning resin. Comparison of HPLC chromatograms, percent 99mTc-bound to MAb, biodistribution and scintigraphic results show that our cleaning resin methodology provides a 99mTc-labeled MAb of essentially equal purity and utility as does the established, chromatographic one.

186Rhenium-HNK1 monoclonal antibody targets human small cell lung cancer cells in athymic nude mice: rapid screening model for therapy

A model is described by which in vivo tumor-MOAB interactions may be investigated. The method is rapid and may aid in the selection of appropriate MOABS from a panel of MOABS for individualized patient treatment. Groups of athymic nude mice were injected intravenously with small cell lung cancer line SHP-77 cells which are trapped primarily in the lungs. Twenty-four hours post tumor cell inoculation, 186Rhenium tagged HNK1 MOAB (CD57) was injected intravenously. Controls which received no tumor cells were injected with unbound 186Re or radioactive MOAB. Biodistribution studies at 24 hours following MOAB injection showed significantly more radioactivity in lungs of mice inoculated with both SHP-77 cells and 186Re MOAB than did lungs of controls.

A new method of technetium-99m labeling of monoclonal antibodies through sugar residues. A study with TAG-72 specific CC-49 antibody

We have developed a very efficient labeling technique for monoclonal antibodies with technetium-99m. Oxidation of sugar residues on the IgG class of antibodies leads to the generation of aldehyde groups which are further reacted with two newly developed hydrazide compounds. This methodology introduces sulfhydryl groups on the antibody through sugar residues which can be labeled with technetium-99m. We have studied the TAG-72 specific second generation antibody CC-49. The specific activity of the labeled antibody was high without loss of its immunoreactivity.

A technique to prepare boronated B72.3 monoclonal antibody for boron neutron capture therapy

B72.3 monoclonal antibody has been successfully boronated using mercaptoundecahydro-closo-dodecaborate (boron cage compound). The reagent was incorporated by first reacting the lysine residues of the antibody with m-maleimidobenzoyl succinimide ester (MBS), followed by Michael addition to the maleimido group by the mercapto boron cage compound to form a physiologically stable thioether linkage. Boron content of the antibody was determined by atomic absorption spectroscopy. For biodistribution studies, boronated antibody was radioiodinated with idogen. 125I-labeled and boronated B72.3 monoclonal antibody demonstrated clear tumor localization when administered via tail vein injections to athymic nude mice bearing LS174-T tumor xenografts. Boronated antibody was calculated to deliver 10(6) boron atoms per tumor cell. Although this falls short of the specific boron content originally proposed as necessary for boron neutron capture therapy (BNCT), recent calculations suggest that far fewer atoms of 10B per tumor cell would be necessary to effect successful BNCT when the boron is targeted to the tumor cell membrane.

Radiosensitization and hypoxic cell toxicity of NLA-1 and NLA-2, two new bioreductive compounds

Two new bioreductive compounds, 9-[3-(2-nitro-1-imidazolyl)propylamino]acridine hydrochloride (NLA-1) and 9-[2-(2-nitro-1-imidazolyl)ethylamino]acridine hydrochloride (NLA-2), have been prepared. They feature an acridine ring to intercalate with DNA, a 2-nitroimidazole ring as the radiosensitizing moiety and an amino functionality for increased DNA-binding and hydrophilicity. Time and concentration dependent cytotoxicity as well as radiosensitization efficacy of the two compounds under hypoxic or aerobic conditions were determined in vitro using V-79 cells and an MTT colorimetric or clonogenic assay. The isosensitization point (ISP), defined as that drug concentration which results in the same survival decrement upon exposure of hypoxic or oxygenated cells to a given radiation dose, has been determined for both compounds at 7.5 Gy and the values are significantly lower than the ISPs of 5-[3-(2-nitro-1-imidazolyl)propyl]phenanthridinium bromide, 2-(2-nitro-1-imidazolyl)ethylamine or misonidazole (MISO). NLA-1 and NLA-2 are potent hypoxic cytotoxins and on a concentration basis, more potent than MISO as radiosensitizers in vitro. The sensitization enhancement ratios were significantly increased when 1 h drug preincubation under hypoxia at 37 degrees C was applied, before irradiation at room temperature.

Effects of tyrosinase activity on the cytotoxicity of 4-S-cysteaminylphenol and N-acetyl-4-S-cysteaminylphenol in melanoma cells

The rationale for melanoma specific antitumor agents containing phenolic amines is based in part upon the ability of the enzyme tyrosinase to oxidize these prodrugs to toxic intermediates. Two phenolic amine compounds, N-acetyl-4-S-cysteaminylphenol (N-Ac-4-S-CAP) and 4-S-cysteaminylphenol (4-S-CAP), demonstrated growth inhibitory activity with a variety of melanoma cell lines and were essentially non-toxic to non-melanoma cell lines. Theophylline, an inhibitor of cyclic nucleotide phosphodiesterase, increased in situ tyrosinase activity and enhanced the antimelanoma effects of 4-S-CAP and N-Ac-4-S-CAP in pigmented melanoma cell lines. Phenylthiourea, a specific inhibitor of tyrosinase activity, partially blocked the growth inhibitory activity of N-Ac-4-S-CAP in human pigmented melanoma cells. Buthionine sulfoximine, an inhibitor of the synthesis of the cellular antioxidant glutathione, potentiated the growth inhibitory activity of N-Ac-4-S-CAP in pigmented melanoma cells.

Radiotoxicity of 17 alpha-[125I]iodovinyl-11 beta-methoxyestradiol in MCF-7 human breast cancer cells

Therapeutic strategies for human breast cancer using 125I-labeled steroid hormones are clinically attractive in light of the estrogen dependence of many human breast cancers and the favorable microdosimetry resulting from 125I decay. We determined the uptake specific estrogen receptor binding and radiotoxicity of 17 alpha-[125I]iodovinyl-11 beta-methoxyestradiol (125IVME2) in vitro using cultured MCF-7 human breast carcinoma cells. 125IVME2 rapidly enters MCF-7 cells and reaches a plateau in the presence of competing 10(-7) M 17 beta-estradiol. In the absence of competitor, uptake is substantially greater before reaching a plateau. Efflux of 125IVME2 from cells incubated in the absence of estradiol decreases to levels corresponding to specific binding. Under equilibrium conditions and in the absence of competitor, 125IVME2 binds to both specific and nonspecific sites but, in the presence of excess 17 beta-estradiol, the observed binding is nonspecific. 125IVME2 is cytotoxic to exponentially growing MCF-7 cells and produces a survival curve typical of those observed for [125I]iododeoxyuridine and 16 alpha-[125I]iodoestradiol.