Efficacy of multiple administrations of a recombinant adenovirus expressing wild-type p53 in an immune-competent mouse tumor model

An Oncolytic Adenovirus Targeting Transforming Growth Factor β Inhibits Protumorigenic Signals and Produces Immune Activation: A Novel Approach to Enhance Anti-PD-1 and Anti-CTLA-4 Therapy

In an effort to develop a new therapy for cancer and to improve antiprogrammed death inhibitor-1 (anti-PD-1) and anticytotoxic T lymphocyte-associated protein (anti-CTLA-4) responses, we have created a telomerase reverse transcriptase promoter-regulated oncolytic adenovirus rAd.sT containing a soluble transforming growth factor receptor II fused with human IgG Fc fragment (sTGFβRIIFc) gene. Infection of breast and renal tumor cells with rAd.sT produced sTGFβRIIFc protein with dose-dependent cytotoxicity. In immunocompetent mouse 4T1 breast tumor model, intratumoral delivery of rAd.sT inhibited both tumor growth and lung metastases. rAd.sT downregulated the expression of several transforming growth factor β (TGFβ) target genes involved in tumor growth and metastases, inhibited Th2 cytokine expression, and induced Th1 cytokines and chemokines, and granzyme B and perforin expression. rAd.sT treatment also increased the percentage of CD8⁺ T lymphocytes, promoted the generation of CD4⁺ T memory cells, reduced regulatory T lymphocytes (Tregs), and reduced bone marrow-derived suppressor cells. Importantly, rAd.sT treatment increased the percentage of CD4⁺ T lymphocytes, and promoted differentiation and maturation of antigen-presenting dendritic cells in the spleen. In the immunocompetent mouse Renca renal tumor model, similar therapeutic effects and immune activation results were observed. In the 4T1 mammary tumor model, rAd.sT improved the inhibition of tumor growth and lung and liver metastases by anti-PD-1 and anti-CTLA-4 antibodies. Analysis of the human breast and kidney tumors showed that a significant number of tumor tissues expressed high levels of TGFβ and TGFβ-inducible genes. Therefore, rAd.sT could be a potential enhancer of anti-PD-1 and anti-CTLA-4 therapy for treating breast and kidney cancers.

Anti-tumor effect of adenoviral vector-mediated p53 gene transfer on the growth of canine osteosarcoma xenografts in nude mice

We evaluated the anti-tumor effect of adenoviral vector-mediated p53 gene therapy on the growth of canine osteosarcoma xenografts formed in nude mice. Nude mice were subcutaneously transplanted with cells of 2 P53 mutant canine osteosarcoma cell lines, POS and CHOS. The osteosarcoma xenografts were injected with either an adenoviral vector that expresses canine wild-type P53 (AxCA-cp53) or LacZ (AxCA-LacZ). Tumor growth was significantly inhibited in the xenografts injected with AxCA-cp53 in comparison to those injected with AxCA-LacZ or PBS during the observation period of 27 days. An increase of the amount of p21(WAF1/CDKN1A) mRNA, and the number of apoptotic cells was shown in the tumors injected with AxCA-cp53 in comparison to those injected with AxCA-LacZ or PBS. The present study revealed that the adenoviral vector-mediated p53 gene transfer had an anti-tumor effect in canine osteosarcoma xenografts formed in nude mice.

Electrogene therapy with p53 of murine sarcomas alone or combined with electrochemotherapy using cisplatin

The aim of our study was to evaluate feasibility and therapeutic potential of electrogene therapy with p53 alone or combined with electrochemotherapy using cisplatin on two murine sarcomas with different p53 status. Antitumor effectiveness of three consecutive electrogene treatments with p53 was more effective in wild-type LPB tumors than mutated SA-1 tumors, resulting in 21.4% of tumor cures in LPB tumors and 12.5% in SA-1 tumors. Pretreatment of tumors with electrogene therapy with p53 enhanced chemosensitivity of both tumor models treated by electrochemotherapy with cisplatin. After only one application of this treatment combination in the LPB tumor model, specific tumor growth delay was prolonged in the combined treatment group compared to electrogene therapy with p53 or electrochemotherapy with cisplatin alone, whereas in SA-1 tumors this treatment combination resulted in 31.6% of cured animals. Results of our study show that electrogene therapy with p53 alone or combined with electrochemotherapy is feasible and effective treatment of tumors. The combination of electrogene therapy and electrochemotherapy after only one application resulted in complete regression of tumors.

Adenovirus-mediated p53 tumor suppressor gene therapy of osteosarcoma

The clinical outcome for osteosarcoma (OS) remains discouraging despite efforts to optimize treatment using conventional modalities including surgery, radiotherapy and chemotherapy. Novel therapeutic approaches based on our expanding understanding of the mechanisms of tumor cell killing have the potential to alter this situation. Tumor suppressor gene therapy aims to restore the function of a tumor suppressor gene lost or functionally inactivated in cancer cells. One such molecule, the p53 tumor suppressor gene plays a critical role in safeguarding the integrity of the genome and preventing tumorigenesis. Introduction of wild-type (wt) p53 into transformed cells has been shown to be lethal for most cancer cells in vitro, but clinical trials of p53 gene replacement have had limited success. Analysis of these clinical trials highlighted the insufficient efficacy of current vectors and low proapoptotic activity of wt p53 as a single agent in vivo. In this review, a contemporary summarization of the current status of adenovirus-mediated p53 gene therapy of OS is presented. Advancement in our understanding of p53 tumor suppressor activity, the molecular biology of chemoresistant OS, and recent advances in tumor targeting with adenoviral vectors are also addressed. Based on these parameters, prospects for future investigations are proposed.

p21WAF1/CIP1 is more effective than p53 in growth suppression of mouse renal carcinoma cell line Renca in vitro and in vivo

PURPOSE

Although there are many controversial reports about the effect of p53 and p21(WAF1/CIP1) overexpression in different human tumor cells, the p53 gene is shown to be a more effective candidate for cancer gene therapy because of its more pronounced ability to induce apoptosis. In the present study, we present the effect of p53 and p21(WAF1/CIP1) overexpression on mouse renal carcinoma cells in vitro and in vivo.

METHODS

p53 and p21(WAF1/CIP1) genes were introduced into Renca cells using adenoviral vectors (Ad5CMV-p53 and Ad5CMV-p21). The induction of apoptosis was measured using Annexin V assay and DNA fragmentation analysis. The expression of proteins was examined using immunocytochemistry and Western blot methods. The ability of adenoviral vectors to inhibit tumorigenicity of Renca cells, as well as the growth of pre-established tumors was measured.

RESULTS

In vitro growth assays revealed higher growth suppression after Ad5CMV-p21 infection. Although both vectors induced apoptosis, Ad5CMV-p53 was slightly more efficient. In vivo studies in Balb/c mice, demonstrated that tumorigenicity was completely suppressed by Ad5CMV-p21. Besides this, Ad5CMV-p21 significantly inhibited the growth of established tumors, while Ad5CMV-p53 did not.

CONCLUSIONS

These data suggest that p21(WAF1/CIP1) is a more potent growth suppressor than p53 of mouse tumor cells Renca. The divergent responses of tumor cells to p21(WAF1/CIP1) overexpression could be due to various networks that differ between species.

Systemic genetic transfer of p21WAF-1 and GM-CSF utilizing of a novel oligopeptide-based EGF receptor targeting polyplex

Based on the fact that aberrant overexpression of some growth factor receptors was observed in a variety of human cancer cells, a novel nonviral gene delivery system GE7, which contains a 16-amino-acid ligand for identifying EGF receptor was constructed for tumor-targeted gene therapy. Intravenous administration of GE7 system revealed that it has the ability to target beta-galactosidase (beta-gal) reporter gene into murine hepatoma (Hepa) cells. Owing to the limited antitumor effects elicited by a single-gene transfer, recent efforts to treat malignancy using combined gene therapy have been accomplished with varying degrees of success. In this study, the human cyclin-dependent kinase inhibitor gene p21(WAF-1) and the murine cytokine gene granulocyte-macrophage colony-stimulating factor (GM-CSF) were used simultaneously for in vivo gene therapy through systemic injection of the EGF R targeted GE7/DNA complex into murine hepatoma-bearing mice. The results demonstrated that combined administration of p21(WAF-1) and GM-CSF could remarkably inhibit the growth of subcutaneously transplanted hepatoma Hepa cells, and significantly increase the survival rate of tumor-bearing mice. The activities of natural killer (NK) cells and specific cytotoxic T lymphocytes (CTL) were clearly enhanced after combined gene therapy. In vitro experiments showed that p21(WAF-1) gene transfer exhibited a suppressive function on the growth of Hepa cells and the expression of H-2K(b) and B7-1 molecules on Hepa cells increased significantly after combined genes delivery. All these results suggested that the GE7 system was able to target therapeutic genes efficiently to cancer cells, which showed high EGF R expression. The cotransfer of p21(WAF-1) and GM-CSF genes apparently inhibited the growth of tumors through (a) the arrest of tumor cell growth and (b) the enhancement of systemic antitumor immunity.

p53 alone or in combination with antisense cyclin D1 induces apoptosis and reduces tumor size in human melanoma

Melanoma incidence is growing at a faster rate than any other human malignancy. Wild-type (wt) p53 is important in both G(1) and G(2) cell cycle arrest, and cyclin D1 (CD1) is necessary for G(1)-->S progression in melanoma cells. We reported that an adenoviral vector containing wt p53 significantly reduced [(3)H]thymidine uptake in melanoma cells containing mutant but not wt p53. Subsequently we showed that CD1 decreased melanoma proliferation and increased apoptosis. We now extend these findings by evaluating the effect on preformed melanomas of (1) intratumoral therapy with wt p53 alone, (2) wt p53 in combination with antisense (AS) CD1, both short (< or =14 days) and longer term, and (3) doubling the dose or repeat doses of wt p53 or AS CD1. Two melanoma cells lines that metastasize in SCID mice (451 and 1205) were used, one containing a p53 mutation (451) and the other a normal p53 gene sequence (1205). Compared to injection with a control adenoviral vector containing beta-galactosidase (LacZ), intratumoral injection of wt p53 slowed the growth of tumors formed from 451 cells. Using 5 x 10(8) plaque forming units as our standard intratumoral dose, neither doubling the dose of LacZ, p53 or AS CD1, nor repeat doses of the vectors, was as effective as combined therapy with wt p53+AS CD1, which resulted in the shrinkage of all tumors treated and 4/7 (57%) tumors vanished. No tumors treated with wt p53 or AS CD1 alone vanished. Wt p53+AS CD1 treatment resulted in significantly more cells undergoing apoptosis compared to either therapy alone. In summary, combining the separately effective treatment vectors p53 and AS CD1 led to an enhanced growth-suppressive and apoptotic effect, supporting a role for combination gene therapy to treat human malignant melanoma.

A recombinant adenovirus expressing p7(Kip1) induces cell cycle arrest and apoptosis in human 786-0 renal carcinoma cells

PURPOSE

We evaluated the effects of the over expression of p27Kip1, a cyclin dependent kinase inhibitor and tumor suppressor protein, on the 786-0 human renal carcinoma cell line.

MATERIALS AND METHODS

The recombinant adenovirus Adp27Kip1 was evaluated for the induction of p27 protein expression in 786-0 renal carcinoma cells. Expression time and optimal vector concentration were determined. Growth curve studies, cell cycle analysis and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling were done to determine the effects of p27Kip1 on the cell cycle. Cyclin dependent protein kinase (Cdk) inhibitor (CDKI) activity assays were done to determine the expression/activities of Cdks and Western blot analysis was performed to determine the presence of CDKIs and other cell cycle regulator proteins. Nude mouse xenografts were established to demonstrate the in vivo efficacy of Adp27Kip1.

RESULTS

p27Kip1 protein expression was detected within 12 hours after Adp27Kip1 infection and it remained stable for at least 48 hours. Growth studies demonstrated that Adp27Kip1 infection resulted in the inhibition of proliferation by 3 days after infection and cell death was detected by day 5. Cell cycle analysis of DNA content indicated an accumulation of cells in the G1 phase of Adp27Kip1 infected cells and a corresponding decrease in S phase cells within 48 hours after infection. Cdk activity was determined, and Cdk2, Cdk4 and Cdc2 kinase activities were inhibited, consistent with p27Kip1 over expression. The levels of the CDKIs p16 and p18 were elevated 24 hours after Adp27Kip1 infection, while p21 levels remained unchanged. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling revealed that Adp27Kip1 infection but not infection by control virus induced detectable apoptosis within 24 hours. Adp27Kip1 significantly caused the reduction in the size of tumors of the renal cell carcinoma xenografts.

CONCLUSIONS

This study demonstrates the potential effectiveness of Adp27Kip1 as a vector for gene therapy studies of renal cell carcinoma.

Intra-arterial delivery of p53-containing adenoviral vector into experimental brain tumors

Human tumor xenografts established in athymic rat brains were used to determine the feasibility of intravascular delivery of tumor suppressor genes to brain tumors. Both tumor size and number were compared to characterize the effect of tumor burden on tumor transduction efficacy by a control LacZ-containing adenoviral vector. Experiments with tumors grown in vivo for either 3, 5, or 7 days demonstrated that 5-day-old tumors provided the best target for vector infection and transgene expression by this mode of administration. Intra-arterial mannitol facilitated transduction efficiency. Tumor burden did not seem to affect transduction, while tumor location appeared to be an important factor. Based on these results, intra-arterial infusion of a p53-containing adenoviral vector was carried out and resulted in significant retardation of brain tumor growth 3 days after administration. Effects at longer time points were not as significant. These findings indicate that intra-arterial administration of adenoviral vectors containing p53 is efficient and can result in changes in tumor size, but that long-term control of tumor growth may require multiple adenoviral treatments.

A rapid and easy method for production and selection of recombinant adenovirus genomes

Adenoviruses are used widely as vectors for gene therapy. Due to the large size of their genome there is a low frequency of unique restriction sites and many techniques have been described to construct recombinant viruses. Whatever the considered technique, the Escherichia coli strain BJ5183 is used to obtain recombinant adenovirus genomes in a plasmid, or to construct defective viral backbones which will be used to produce infectious viral particles by homologous recombination in HEK293 cells. Unfortunately BJ5183 bacteria do not produce a sufficient amount of plasmid DNA to allow for restriction analysis. Plasmids have to be transferred into another strain to detect the expected construction. It is reported now that the common E. coli strain, Top10F' can be used for the construction of recombinant adenovirus genomes. A plasmid carrying a kanamycin resistance gene and containing the two ends of the adenovirus genome was used. It permits modification by classical molecular biology techniques or homologous recombination at both ends of the genome. The remainder of the genome is introduced by homologous recombination in Top10F'. Several homologous recombination steps were successfully performed without the steps of extraction and introduction of plasmid DNA in another strain to check the plasmids obtained.

Combined adenovirus-mediated nitroreductase gene delivery and CB1954 treatment: a well-tolerated therapy for established solid tumors

Gene-directed enzyme prodrug therapy (GDEPT) is a refinement of cancer chemotherapy that generates a potent cell-killing drug specifically in tumor cells by enzymatic activation of an inert prodrug. We describe in vivo studies that evaluate the efficacy and safety of intratumoral (i.t.) injection of an adenovirus vector (CTL102) expressing Escherichia coli nitroreductase (NTR) combined with systemic prodrug (CB1954) treatment. A single i.t. injection of CTL102 (7.5 x 10(9) to -2 x 10(10) particles) followed by CB1954 treatment produced clear anti-tumor effects in subcutaneous (s.c.) xenograft models of four cancers that are likely candidates for GDEPT (i.e., primary liver, head and neck, colorectal and prostate). Virus dose-response studies (s.c. liver model) revealed a steep increase and subsequent rapid plateauing of both NTR gene delivery and anti-tumor efficacy. Evidence of minor virus spread (toxicity) was observed in a s.c. head and neck xenograft model. This was eliminated by passive immunization with neutralizing anti-Ad5 antibodies prior to virus injection without reducing the magnitude of the anti-tumor effect. Preexisting anti-Ad5 neutralizing antibodies may therefore be an advantage rather than an issue in the clinical use of this new therapy.

Pretreatment with protease is a useful experimental strategy for enhancing adenovirus-mediated cancer gene therapy

A key impediment to the development of effective virus-mediated gene therapy for cancer is the low level of gene transfer that occurs after the administration of recombinant viral vectors. Improving in vivo infection and transduction efficiency is an important goal for gene therapy. The limited distribution of gene delivery is particularly problematic when large vectors such as recombinant adenoviruses and retroviruses are used to mediate transgene delivery to solid tumors. To facilitate the spread of virus, we have investigated the potential of administering proteases prior to the intratumoral inoculation of recombinant replication deficient adenovirus. For these studies, we chose proteases that are active against collagen and the other extracellular matrix proteins found in primary brain tumor tissue, but are not widely expressed in normal brain. Various concentrations of a mixture of collagenase/dispase or trypsin were inoculated into xenografts of human glioblastoma multiforme-derived brain tumor cell lines U87, U251, and SF767. Subsequently, recombinant adenovirus encoding the beta-galactosidase gene was administered and tumor tissue was examined for evidence of virus infection. Both collagenase/dispase and trypsin enhanced virus infection, indicating that protease pretreatment may be a useful strategy for enhancing virus-mediated gene transduction for many in vivo applications.

Gene replacement strategies for treating non-small cell lung cancer

Fewer than 15% of the 170,000 patients who develop lung cancer each year will survive their disease, which shows the need for novel, more specific, and less toxic therapeutic strategies. Recent advances in molecular biology have made it possible to ascertain which genetic alterations contribute to the etiology of cancer. For example, the tumor-suppressor gene, p53, responsible for directing repair of damaged DNA or committing a cell to apoptosis, is mutated or otherwise altered in more than 50% of cancers, including 40% to 70% of non-small cell lung cancers. Many p53-deficient tumors have proven remarkably resistant to radiotherapy and chemotherapy. The preclinical and clinical studies of gene therapy reviewed in this article show (1) successful transfer and expression of a potentially therapeutic p53 gene construct in tumor cells, (2) observation of antitumor effects in vitro and in vivo, and (3) most critically, a lack of significant toxicity. The results of these studies indicate that gene replacement therapy is a feasible alternative therapy for cancer. In addition, these studies show that transfer of the p53 gene can induce radiation sensitization in previously radiation-resistant tumors, leading to the possibility of new therapeutic protocols combining gene replacement with radiation therapy.

Studying heterotrimeric G-protein-linked signal transduction using replication-deficient adenoviruses

Plasma membrane-spanning G-protein-linked receptors transduce approximately 60% of all extracellular stimuli in higher animals. Many G-protein-linked receptor pathways are yet to be elucidated, with the receptor, G-protein or effector system as yet unidentified. In addition, many fundamental issues pertaining to G-protein signalling remain unresolved, such as the factors governing the specificity of G-protein receptor coupling and the control of signal amplitude in response to G-protein activation. In order to address some of these issues, the use of replication-deficient adenoviruses as gene transfer vectors for investigations of G-protein signalling has been developed, facilitating dissection of G-protein-linked signal transduction pathways in an extensive range of cultured cells, as well as in vivo. The present review focuses on the versatility and utility of adenoviruses for the investigation of signalling by heterotrimeric G-proteins and explores some of the recent advances in adenoviral technology as they relate to the study of signal transduction.

FGF2-Targeted adenovirus encoding platelet-derived growth factor-B enhances de novo tissue formation

Gene therapy has yet to achieve reproducible clinical efficacy, due to inadequate gene delivery, inadequate gene expression, or dose-limiting toxicity. We have developed a gene therapy technology for tissue repair and regeneration that employs a structural matrix for DNA delivery. The matrix holds the DNA vector at the treatment site and provides a scaffolding for in-growth and accumulation of repair cells and efficient DNA transfection. We now report, for the first time, matrix-mediated delivery of targeted DNA vectors for soft tissue repair. A collagen matrix was used to deliver an adenoviral vector encoding platelet-derived growth factor-B (AdPDGF-B), resulting in efficient transgene expression in vitro and in vivo. Increases in the overall levels of expression and in the relative amounts of secreted PDGF-BB were achieved when AdPDGF-B was conjugated to fibroblast growth factor (FGF2) such that the virus was targeted for cellular uptake via FGF receptors. Matrix-mediated delivery of AdPDGF-B enhanced wound healing responses in vivo, and FGF2 targeting generated effects comparable to nontargeted vectors at significantly lower doses. Therefore, matrix-mediated delivery in combination with FGF2 targeting overcomes some of the safety and efficacy limitations of current gene therapy strategies and is an attractive therapeutic approach for tissue repair and regeneration.

Pre-existent adenovirus antibody inhibits systemic toxicity and antitumor activity of CN706 in the nude mouse LNCaP xenograft model: implications and proposals for human therapy

Pre-existent humoral antibody to adenovirus potentially confounds human clinical trials involving intravascular administration of adenovirus. Using the LNCaP prostate cancer xenograft model in BALB/c nu/nu mice and the prostate-specific attenuated replication-competent adenovirus (ARCATM) CN706, we developed an animal model that systematically controls both the dose of intravascularly administered adenovirus and the titer of the pre-existent anti-Ad5 antibody, and then measures the virus-induced toxicity as well as antitumor activity. We prepared hyperimmune sera to adenovirus in rabbits, passively injected the purified rabbit anti-Ad5 antibody into tumor-bearing mice, and established measurable humoral anti-Ad5 antibody titers. CN706 was intravenously injected into the tail vein of animals 24 hr after passive anti-Ad5 antibody administration. In the absence of pre-existent antibody, the lethal dose (LD100) for BALB/c nu/nu mice was 2.5x10(11) CN706 particles, whereas 1x10(11) CN706 particles was not lethal. However, in the presence of a 1:80 pre-existent titer of Ad5 neutralizing antibody (NAb), intravenous injection of 5x10(11) CN706 particles was no longer lethal. In addition, pre-existent antibody also prevented antitumor activity in a dose-dependent manner: 1x 10(11) CN706 particles prevented LNCaP xenograft tumor progression, but antitumor activity was eliminated by a pre-existent 1:80 NAb titer. These results led us to propose transient removal of pre-existent adenovirus antibody by immunoapheresis. An affinity column of cloned virus capsid proteins was constructed that was able to specifically remove adenovirus antibody from human clinical serum samples. A 5-min disposable immunoassay was also developed to monitor the level of pre-existent antibody in sera before and after immunoapheresis. Clinically, this approach may enable controlled clinical studies of intravenously administered adenovirus in patients with pre-existent anti-adenovirus antibody.

Adenovirus-p53-mediated gene therapy of anaplastic large cell lymphoma with t(2;5) in a nude mouse model

Adenovirus-p53-mediated apoptosis has been extensively evaluated in animal xenografts derived from human epithelial tumors and recently began testing in phase I clinical trials, but has not been evaluated for lymphoid malignancies. Cell lines derived from anaplastic large cell lymphoma (ALCL) carrying the t(2;5) translocation are efficiently transduced by adenoviral vector expressing p53 and undergo apoptosis. To test the in vivo efficiency of adenovirus-mediated-p53 expression and apoptosis induction, SUDHL-1 cells (derived from human ALCL) were injected subcutaneously into athymic nude mice. Cells from the xenograft had typical morphology of human ALCL by standard hematoxylin-eosin staining, CD5+, CD45+ and CD30+ immunophenotype, the t(2;5) translocation by PCR. Six tumors from an initial set of mice were evaluated for apoptosis by TUNEL and for necrosis by hematoxylin-eosin staining 48-72 h after injection with 1 x 108 p.f.u. of AdWTp53 (adenoviral vector expressing p53), of AdNull (adenoviral vector backbone) and PBS (mock), respectively. TUNEL staining was positive only in tumors injected with AdWTp53 and was mainly localized around the needle track. Differences of the means of the counts of the necrotic cells were statistically significant at P = 0.02 between AdWTp53 and mock and only borderline between AdWTp53 and AdNull. Twenty-three tumors from a separate set of mice were subsequently injected with AdWTp53, AdNull and PBS and evaluated for in vivo tumor response. Three total injections of viral vectors (1 x 108 p.f.u.) and PBS were given every 48-72 h. Only tumors injected with AdWTp53 showed tumor growth inhibition with a mean final tumor volume that was statistically significantly smaller than AdNull (P = 0.007) and mock (P = 0.002). Based on these results we foresee a potential application of adenovirus-mediated p53 apoptosis as gene therapy of lymphomas.

Effective repeat administration with adenovirus vectors to the muscle

Effective repeat administration of adenovirus vectors following intranasal or intravenous delivery is hindered by a strong neutralizing antibody response to the vector. Intramuscular administration of adenovirus vectors elicited a neutralizing antibody response that peaked between 14 and 21 days after infection. However, effective repeat intramuscular administration of adenovirus vectors was not hindered by the presence of neutralizing antibodies in the serum. Surprisingly, beta-galactosidase expression in the skeletal muscle of immunized mice was equivalent to that observed in control mice. As expected, these serum neutralizing antibodies effectively blocked repeat administration of adenovirus vectors when delivered via the intravenous route. These results were observed in both C57BL/6 and Balb/c mice and thus do not appear to be strain specific. Successful repeat administration of adenovirus vectors to skeletal muscle has significant implications for the use of adenovirus vectors clinically and for increasing the safety and efficacy of adenovirus vector gene delivery.

Involvement of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and p53 in neuronal apoptosis: evidence that GAPDH is upregulated by p53

We recently reported that cytosine arabinoside (AraC)-induced apoptosis of cerebellar neurons involves the overexpression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The present study was undertaken to investigate whether p53 and/or Bax overexpression participates in the AraC-induced apoptosis of cerebellar granule cells and, if so, the relationship between p53 induction and GAPDH overexpression in these cells. AraC-induced apoptosis of cerebellar granule cells was preceded by an increase in levels of p53 mRNA and protein detected between 1 and 8 hr after treatment. The mRNA level for a p53 target gene, Bax, was also increased. The increase in GAPDH mRNA lasted longer than that of either p53 or Bax, and the level of GAPDH protein in the particulate fraction increased after induction of GAPDH mRNA. The antisense oligonucleotide to p53 protected granule cells from AraC-induced chromatin condensation, internucleosomal cleavage, and apoptotic death. The inhibition of p53 expression by the p53 antisense oligonucleotide not only blocked the expression of Bax but also partially suppressed the increased GAPDH mRNA and protein levels. Conversely, the suppression of GAPDH expression and subsequent attenuation of apoptosis of granule cells by GAPDH antisense oligonucleotide did not influence the expression of p53 or Bax. Cerebellar granule cells prepared from p53 knock-out mice were resistant to AraC toxicity, and the p53 gene knock-out suppressed AraC-upregulated GAPDH expression. Moreover, infection of PC12 cells with an adenoviral vector containing p53 gene dramatically increased GAPDH expression and triggered cell apoptosis. These results suggest that AraC-induced apoptosis of cerebellar granule cells involves the expression of both GAPDH and p53 and that, similar to Bax, GAPDH is upregulated by p53 after exposure to the apoptotic insult.

Ovine adenovirus vectors overcome preexisting humoral immunity against human adenoviruses in vivo

Recombinant human adenoviruses (hAd) have become widely used as tools to achieve efficient gene transfer. However, successful application of hAd-derived vectors in clinical trials is limited due to immunological and potential safety problems inherent in their human origin. In this study, we describe a recombinant ovine adenovirus (OAV) as an alternative vector for gene transfer in vivo. In contrast to an hAd vector, the OAV vector was not neutralized by human sera. An OAV vector which contained the cDNA of the human alpha1-antitrypsin (hAAT) gene linked to the Rous sarcoma virus promoter was generated and administered systemically to mice. The level and duration of hAAT gene expression was similar to that achieved with an hAd counterpart in both immunocompetent and immunodeficient mice. However, the tissue distribution of the OAV vector differed from that observed for hAd vectors in that the liver was not the dominant target. Significantly, we demonstrated efficient gene transfer with the OAV vector into mice immunized with hAd vectors and vice versa. We also confirm that the immune response to a transgene product can prevent its functional expression following sequential application of a vector. Our results suggest a possible solution to endemic humoral immunity against currently used hAd vectors and should therefore have an impact on the design of improved gene therapy protocols utilizing adenovirus vectors.

Adenovirus-mediated p53 gene transfer in advanced non-small-cell lung cancer

BACKGROUND

Preclinical studies in animal models have demonstrated tumor regression following intratumoral administration of an adenovirus vector containing wild-type p53 complementary DNA (Ad-p53). Therefore, in a phase I clinical trial, we administered Ad-p53 to 28 patients with non-small-cell lung cancer (NSCLC) whose cancers had progressed on conventional treatments.

METHODS

Patients received up to six, monthly intratumoral injections of Ad-p53 by use of computed tomography-guided percutaneous fine-needle injection (23 patients) or bronchoscopy (five patients). The doses ranged from 10(6) plaque-forming units (PFU) to 10(11) PFU.

RESULTS

Polymerase chain reaction (PCR) analysis showed the presence of adenovirus vector DNA in 18 (86%) of 21 patients with evaluable posttreatment biopsy specimens; vector-specific p53 messenger RNA was detected by means of reverse transcription-PCR analysis in 12 (46%) of 26 patients. Apoptosis (programmed cell death) was demonstrated by increased terminal deoxynucleotide transferase-mediated biotin uridine triphosphate nick-end labeling (TUNEL) staining in posttreatment biopsy specimens from 11 patients. Vector-related toxicity was minimal (National Cancer Institute's Common Toxicity Criteria: grade 3 = one patient; grade 4 = no patients) in 84 courses of treatment, despite repeated injections (up to six) in 23 patients. Therapeutic activity in 25 evaluable patients included partial responses in two patients (8%) and disease stabilization (range, 2-14 months) in 16 patients (64%); the remaining seven patients (28%) exhibited disease progression.

CONCLUSIONS

Repeated intratumoral injections of Ad-p53 appear to be well tolerated, result in transgene expression of wild-type p53, and seem to mediate antitumor activity in a subset of patients with advanced NSCLC.