Targeting the replication of adenovirus to p53-defective thyroid carcinoma with a p53-regulated Cre/loxP system

Expression of HIF-1α ODD domain fused canine caspase 3 by EGFR promoter-driven adenovirus vector induces cytotoxicity in canine breast tumor cells under hypoxia

Adenovirus (Ad) vectors are widely used in cancer gene therapies. However, compared to human patients, relatively limited information is available on gene transduction efficiency or cell-specific cytotoxicity in canine tumor cells transduced with Ad vectors. Since epidermal growth factor receptor (EGFR) is highly expressed on canine breast tumor cells, we sought to develop an Ad vector based on the RGD fiber-mutant adenovirus vector (AdRGD) that expresses canine caspase 3 under the control of EGFR promoter. The aims of this study were to achieve high transduction efficiency with transgene expression restricted to canine breast tumor cells. Using EGFR promoter-driven AdRGD, we were able to restrict transgene expression to canine breast tumor cells with no evidence of expression in normal cells. Canine breast tumor cells transduced with EGFR promoter-driven AdRGD carrying canine caspase 3 gene showed cytotoxic activity. We constructed a second AdRGD vector that expressed oxygen-dependent degradation (ODD)-caspase 3 under the control of the EGFR promoter; the fusion protein contains a core part of the ODD domain of hypoxia inducible factor-1 alpha (HIF-1α) fused to caspase 3. Transduction of canine breast tumor cells with EGFR promoter-driven AdRGD expressing ODD-caspase 3 induced a higher rate of cell death under hypoxic conditions compared with under normoxia. The results indicate that the EGFR promoter-driven AdRGD vectors will be of value for tumor-specific transgene expression and safe cancer gene therapy in dogs.

Genetic mutations in the treatment of anaplastic thyroid cancer: a systematic review

BACKGROUND

Anaplastic thyroid cancer (ATC) is a rare, lethal disease associated with a median survival of 6 months despite the best multidisciplinary care. Surgical resection is not curative in ATC patients, being often a palliative procedure. Multidisciplinary care may include surgery, loco-regional radiotherapy, and systemic therapy. Besides conventional chemotherapy, multi kinase-targeted inhibitors are emerging as novel therapeutic tools. The numerous molecular alteration detected in ATC are targets for these inhibitors. The aim of this review is to determine the prevalence of the major genetic alterations occurring in ATC and place the results in the context of the emerging kinase-targeted therapies.

METHODS

The study is based on published PubMed studies addressing the prevalence of BRAF, RAS, PTEN, PI3KCA and TP53 mutations and RET rearrangements in ATC.

RESULTS

21 articles dealing with 652 genetic analyses of the selected genes were used. The overall prevalence determined were the following: RET/PTC, 4%; BRAF, 23%; RAS, 60%; PTEN, 16%; PI3KCA, 24%; TP53, 48%. Genetic alterations are sometimes overlapping.

CONCLUSIONS

Mutations of BRAF, PTEN and PI3KCA genes are common in ATC, with RAS and TP53 being the most frequent. Given ATC genetic complexity, effective therapies may benefit from individualized therapeutic regimens in a multidisciplinary approach.

Anaplastic thyroid cancer: molecular pathogenesis and emerging therapies

Anaplastic thyroid cancer (ATC) is a rare malignancy. While external beam radiation therapy has improved locoregional control, the median survival of approximately 4 months has not changed in more than half a century due to uncontrolled systemic metastases. The objective of this study was to review the literature in order to identify potential new strategies for treating this highly lethal cancer. PubMed searches were the principal source of articles reviewed. The molecular pathogenesis of ATC includes mutations in BRAF, RAS, catenin (cadherin-associated protein), beta 1, PIK3CA, TP53, AXIN1, PTEN, and APC genes, and chromosomal abnormalities are common. Several microarray studies have identified genes and pathways preferentially affected, and dysregulated microRNA profiles differ from differentiated thyroid cancers. Numerous proteins involving transcription factors, signaling pathways, mitosis, proliferation, cell cycle, apoptosis, adhesion, migration, epigenetics, and protein degradation are affected. A variety of agents have been successful in controlling ATC cell growth both in vitro and in nude mice xenografts. While many of these new compounds are in cancer clinical trials, there are few studies being conducted in ATC. With the recent increased knowledge of the many critical genes and proteins affected in ATC, and the extensive array of targeted therapies being developed for cancer patients, there are new opportunities to design clinical trials based upon tumor molecular profiling and preclinical studies of potentially synergistic combinatorial novel therapies.

A novel role for thyroid hormone receptor beta in cellular radiosensitivity

Thyroid hormone receptors (THRs) widely govern cell growth, differentiation and metabolism acting in a ligand- and cofactor-dependent manner to modulate tissue-specific gene expression. Given a large variety of genes regulated by THRs and multiplicity of cellular processes potentially influenced by THRs, we addressed the role of THRB (thyroid hormone receptor beta) in cellular radiosensitivity. Wild-type and mutant THRB were overexpressed in several cell lines using an adenovirus-mediated gene delivery and their effects were examined after cell exposure to gamma-rays. Wild-type THRB decreased clonogenic survival of the cell lines with low levels of endogenous THRB, retarded their growth and synergized with radiation in decreasing proliferative potential and promoting cellular senescence. These changes were accompanied by the accumulation of p21 (CDKN1A, CIP1, WAF1) and p16 (CDKN2A, INK4a) inhibitors of cyclin-dependent kinases and by the decrease of Rb (retinoblastoma protein) phosphorylation. Mutant THRB produced a radioprotective effect, attenuated radiation-induced growth inhibition and cellular senescence. The results suggest that THRB may modulate cellular radiosensitivity and stress-induced senescence.

2-methoxyestradiol induces apoptosis in cultured human anaplastic thyroid carcinoma cells

Anaplastic thyroid carcinoma (ATC) is one of the most malignant tumors in humans, and currently there is no effective treatment. In the present study we investigated the effect of an endogenous estrogen metabolite, 2-methoxyestradiol (2-ME), on the growth of human ATC cells. 2-ME treatment had a strong growth inhibitory effect on five human ATC cell lines (HTh7, HTh 74, HTh83, C643, and SW1736), but showed no effect on one cell line (KAT-4). Cell cycle analysis of the growth-inhibited cells showed that 2-ME induced a G2/M-arrest, followed by an increased fraction of cells in sub-G1. Analysis of internucleosomal DNA laddering as well as DNA fragmentation in a terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) assay demonstrated a high number of cells undergoing apoptosis after 2-ME treatment. An increased activation of caspase-3 and caspase-8 by 2-ME was observed, and inhibition of caspase-3 decreased the apoptotic effect. Addition of 2-ME increased activity of p38 mitogen-activated protein kinase (MAPK) in the sensitive HTh7 as well as the refractory KAT-4 cells, however, activation of stress-activated protein kinase/c-jun aminoterminal kinase (SAPK/JNK) was seen only in the HTh7 cells. Inhibitors of p38 MAPK and SAPK/JNK significantly attenuated the 2-ME effect. Taken together, our data demonstrate an antiproliferative and apoptotic effect of 2-ME on ATC cells involving activation of MAPKs.

Relationship between thyroid peroxidase T cell epitope restriction and antibody recognition of the autoantibody immunodominant region in human leukocyte antigen DR3 transgenic mice

We investigated the relationship between thyroid peroxidase (TPO) antibody and T lymphocyte epitopes in TPO-adenovirus (TPO-Ad) immunized BALB/c mice and mice transgenic for the human class II molecule DR3 associated with human thyroid autoimmunity. TPO autoantibodies are largely restricted to an immunodominant region (IDR). BALB/c mice immunized with fewer (10(7) vs. 10(9)) TPO-Ad particles developed TPO antibodies with lower titers that displayed greater restriction to the IDR. However, as with higher-dose TPO-Ad immunization, T cell epitopes (assessed by splenocyte interferon-gamma response to TPO in vitro) were highly diverse and variable in different animals. In contrast, DR3 mice immunized the higher TPO-Ad dose (10(9) particles) had high TPO antibody levels that showed relative focus on the IDR. Moreover, T cell epitopes recognized by splenocytes from DR3 mice showed greater restriction than BALB/c mice. Antibody affinities for TPO were higher in DR3 than in BALB/c mice. The present study indicates that weak TPO-Ad immunization of BALB/c mice (with consequent low TPO antibody titers) is required for enhanced IDR focus yet is not associated with T cell epitopic restriction. Humanized DR3 transgenic mice, despite stronger TPO-Ad immunization, develop higher titer TPO antibodies that do focus on the autoantibody IDR with T cells that recognize a more limited range of TPO peptides. These data suggest a relationship between major histocompatibility complex class II molecules and the development of antibodies to the IDR, a feature of human thyroid autoimmunity.

Gene therapy for thyroid cancer

Thyroid carcinomas are suitable targets for gene therapy because they can be highly lethal on one hand, while being susceptible to specific tumour targeting on the other hand. Several gene therapy modalities have been evaluated so far in experimental models of thyroid cancer, including tumour suppressor gene replacement, oncogene inhibition, suicide gene therapy, immunotherapy, antiangiogenesis, and viral oncolysis. All of these strategies have shown promising results, but clinical studies are lacking. Based on the clinical experience achieved in a pilot study in patients with advanced thyroid cancer and on clinical results in other types of solid cancer, it is suggested that combined gene therapy approaches, as well as multimodality therapeutic regimens, including gene therapy and conventional treatments, should be pursued to achieve clinically significant results.

Gene therapy for thyroid cancer: current status and future prospects

Despite multimodality treatment for thyroid cancer, including surgical resection, radioiodine therapy, thyrotropin (TSH)-suppressive thyroxine treatment, and chemotherapy/radiotherapy, survival rates have not improved over the last decades. Therefore, development and evaluation of novel treatment strategies, including gene therapy, are urgently needed. A variety of gene therapy approaches have been evaluated for the treatment of follicular cell-derived and medullary thyroid cancer, including corrective gene therapy (p53 restoration, expression of a dominant negative RET mutant), cytoreductive gene therapy (suicide gene/prodrug strategy herpes simplex virus-thymidine kinase [HSV-tk]/ganciclovir, antiangiogenic therapy with endostatin) and immunomodulatory gene therapy (expression of interleukin (IL)-2 and IL-12). Furthermore, cloning of the sodium iodide symporter (NIS) gene has paved the way for the development of a novel cytoreductive gene therapy strategy based on NIS gene transfer followed by the application of radioiodine therapy ((131)I). NIS gene delivery into medullary and follicular cell-derived thyroid cancer cells has been shown to be capable of establishing or restoring radioiodine accumulation and might therefore represent an effective therapy for medullary and dedifferentiated thyroid tumors that lack iodide accumulating activity. The data summarized in this review article clearly demonstrate that the currently available strategies represent potentially curative novel therapeutic approaches for future gene therapy of thyroid cancer. The combination of different therapeutic genes has been demonstrated to be very useful to enhance therapeutic efficacy and seems to have a promising role at least as part of a multimodality approach for advanced thyroid cancer.

Thyroid cancer immuno-therapy with retroviral and adenoviral vectors expressing granulocyte macrophage colony stimulating factor and interleukin-12 in a rat model

BACKGROUND

Introduction of genes encoding immuno-stimulatory cytokine(s) into cancer cells is well known to enhance anti-tumour immunity.

AIM

The present studies were designed to evaluate the therapeutic efficacy of retroviral- and adenoviral-mediated delivery of IL-12 and/or granulocyte macrophage colony-stimulating factor (GM-CSF) genes for thyroid cancer in an immuno-competent rat model.

METHODS

A rat thyroid cancer cell line FRTL-Tc syngeneic to Fisher rat was used.

RESULTS

Expression of these exogenous cytokines did not affect in vitro cell growth. Subcutaneous injection of FRTL-Tc cells retrovirally transduced with IL-12 or GM-CSF genes formed significantly smaller tumours than that of the parental cells, but had little effect on growth of distant tumours, suggesting no vaccine effect. Similarly, injection of the cells infected with adenovirus expressing IL-12 or GM-CSF (AdIL-12 or AdGM-CSF) almost completely abolished tumourigenicity and injection of AdGM-CSF into pre-established tumours significantly inhibited growth of the tumours injected; neither, however, showed a systemic vaccine affect. On the other hand, injection of AdIL-12 into the pre-established tumours significantly inhibited growth of not only the tumours injected but also distant tumours, indicating induction of systemic anti-tumour immunity. Serum IL-12 was detectable only in this approach. There was neither a synergistic or additive effect of these two cytokines.

CONCLUSIONS

Our data demonstrate in a rat thyroid cancer model that only injection of AdIL-12 into the pre-established tumours elicited systemic anti-tumour immunity, but injection of AdGM-CSF or injection of the cells expressing IL-12 or GM-CSF elicited only local effect, indicating that in situdelivery of IL-12 gene with adenovirus appears most efficacious but may still require adjuvant modalities to enhance the anti-tumour effect.

Enhanced antitumor effect of combined replicative adenovirus and nonreplicative adenovirus expressing interleukin-12 in an immunocompetent mouse model

For cancer gene therapy, replicative adenovirus is a promising vector to overcome low infectivity and poor gene delivery of nonreplicative adenovirus in vivo, but its therapeutic efficacy is still unsatisfactory because of the limited spread of replicative virus in a solid tumor. Therefore, the combined therapy with other antitumor agents may be necessary. Nonreplicative adenovirus expressing a therapeutic gene may be a promising candidate because E1 proteins expressed by replicative adenovirus would render nonreplicative adenovirus replicative, augmenting a transgene expression. In this study, we first found that mouse hepatoma Hepa 1-6 cells were permissive for the replication and cytopathic effect of human adenovirus, which enabled us to examine the potential of combined replicative adenovirus and nonreplicative adenovirus expressing an immunostimulator in an immunocompetent mouse-syngeneic Hepa 1-6 tumor model. Nonreplicative adenovirus expressing interleukin-12 (AdIL-12) was used as a model. In vitro coinfection of two adenoviruses produced higher concentrations of IL-12 than infection of AdIL-12 alone in this cell line. In vivo experiments with Hepa 1-6 tumors in syngeneic immunocompetent C57BL/6 mice showed higher concentrations of serum IL-12 and greater therapeutic efficacy in the combination therapy than infection of either adenovirus. These data indicate that the combination of replicative adenovirus and nonreplicative adenovirus expressing an immunostimulator appears to be very efficacious for cancer gene therapy.

Insight into antibody responses induced by plasmid or adenoviral vectors encoding thyroid peroxidase, a major thyroid autoantigen

Plasmid and adenoviral vectors have been used to generate antibodies in mice that resemble human autoantibodies to the thyrotrophin receptor. No such studies, however, have been performed for thyroid peroxidase (TPO), the major autoantigen in human thyroiditis. We constructed plasmid and adenovirus vectors for in vivo expression of TPO. BALB/c mice were immunized directly by intramuscular injection of TPO-plasmid or TPO-adenovirus, as well as by subcutaneous injection of dendritic cells (DC) infected previously with TPO-adenovirus. Intramuscular TPO-adenovirus induced the highest, and TPO-plasmid the lowest, TPO antibody titres. Mice injected with TPO-transfected DC developed intermediate levels. Antibodies generated by all three approaches had similar affinities (Kd approximately 10(-9)M) and recognized TPO expressed on the cell-surface. Their epitopes were analysed in competition assays using monoclonal human autoantibodies that define the TPO immunodominant region (IDR) recognized by patients with thyroid autoimmune disease. Surprisingly, high titre antibodies generated using adenovirus interacted with diverse TPO epitopes largely outside the IDR, whereas low titre antibodies induced by DNA-plasmid recognized restricted epitopes in the IDR. This inverse relationship between antibody titre and restriction to the IDR is likely to be due to epitope spreading following strong antigenic stimulation provided by the adenovirus vector. However, TPO antibody epitope spreading does not occur in Hashimoto's thyroiditis, despite high autoantibody levels. Consequently, these data support the concept that in human thyroid autoimmunity, factors besides titre must play a role in shaping an autoantibody epitopic profile.

Dendritic cells infected with adenovirus expressing the thyrotrophin receptor induce Graves' hyperthyroidism in BALB/c mice

Dendritic cells (DCs) are the most potent antigen-presenting cells and a prerequisite for the initiation of primary immune response. This study was performed to investigate the contribution of DCs to the initiation of Graves' hyperthyroidism, an organ-specific autoimmune disease in which the thyrotrophin receptor (TSHR) is the major autoantigen. DCs were prepared from bone marrow precursor cells of BALB/c mice by culturing with granulocyte macrophage-colony stimulating factor and interleukin-4. Subcutaneous injections of DCs infected with recombinant adenovirus expressing the TSHR (but not beta-galactosidase) in syngeneic female mice induced Graves'-like hyperthyroidism (8 and 35% of mice after two and three injections, respectively) characterized by stimulating TSHR antibodies, elevated serum thyroxine levels and diffuse hyperplasitc goiter. TSHR antibodies determined by ELISA were of both IgG1 (Th2-type) and IgG2a (Th1-type) subclasses, and splenocytes from immunized mice secreted interferon-gamma (a Th1 cytokine), not interleukin-4 (a Th2 cytokine), in response to TSHR antigen. Surprisingly, IFN-gamma secretion, and induction of antibodies and disease were almost completely suppressed by co-administration of alum/pertussis toxin, a Th2-dominant adjuvant, whereas polyriboinosinic polyribocytidylic acid, a Th1-inducer, enhanced splenocyte secretion of IFN-gamma without changing disease incidence. These observations demonstrate that DCs efficiently present the TSHR to naive T cells to induce TSHR antibodies and Graves'-like hyperthyroidism in mice. In addition, our results challenge the previous concept of Th2 dominance in Graves' hyperthyroidism and provide support for the role of Th1 immune response in disease pathogenesis.

Receptor-independent augmentation of adenovirus-mediated gene transfer with chitosan in vitro

Recombinant adenovirus is one of the most widely used viral vectors for gene delivery. This study was designed to evaluate the ability of chitosan, a cationic, linear polysaccharide composed of beta(1,4) linked glucosamine partly containing N-acetyl-glucosamine, to enhance the in vitro infectivity of adenovirus to mammalian cells. Wild type and a fiber-mutant replication-defective recombinant adenoviruses expressing beta-galactosidase were used. In the latter, an RGD peptide, the binding site for alpha(v)beta3 and alpha(v)beta5 integrin, was introduced in the fiber knob enabling adenovirus receptor-independent viral infection. Enhanced effect of chitosan on the infectivity of both adenoviruses was observed in Chinese hamster ovary cells that do not express the receptor for adenovirus with beta-galactosidase activity assay and x-gal staining. These data indicate the receptor-independent mechanism(s) for this enhancement effect. In addition, we found that pH of the culture medium, and molecular mass and concentration of chitosan are also critical factors. Thus, the highest effect was obtained with 0.1-1 microg/ml of chitosan with molecular mass of 19K and 40K in the culture medium of pH 6.4; on the other hand, the effect was negligible with the higher chitosan concentrations (10 microg/ml or more), lower or higher molecular mass (11K and 110K) of chitosan, or at pH of 7.4. Studies using several cell lines with variable levels of adenoviral infectivity revealed that this enhanced effect is evident in the cells with poor infectivity to adenovirus. Since chitosan is biocompatible and inexpensive, these data indicate that chitosan may be a potential candidate for a non-viral vector to safely increase adenoviral infectivity to mammalian cells, particularly those with poor susceptibility to adenoviral infection.

p48 Overexpression enhances interferon-mediated expression and activity of double-stranded RNA-dependent protein kinase in human hepatoma cells

BACKGROUND/AIMS

Double-stranded RNA-dependent protein kinase (PKR) is a key factor involved in interferon (IFN)-induced antiviral actions. Since p48, together with signal transducers and activators of transcription 1 and 2 (STAT1 and STAT2), is an indispensable mediator in IFN-alpha signaling pathways, we investigated the effect of p48 gene transduction on PKR expression and its activity in HuH-7 human hepatoma cells.

METHODS

HuH-7 cells were infected or transfected with p48 gene expression adenoviral vector or plasmid vector, respectively, and incubated with or without IFN-alpha, then PKR expression and phosphorylation of alpha-subunit of eukaryotic protein synthesis initiation factor-2 (eIF2alpha) in the cells were examined. In addition, PKR activity inhibiting protein translation was determined by the decrease of chloramphenicol acetyltransferase (CAT) gene translation or alpha-fetoprotein secretion.

RESULTS

p48 overexpression itself could not stimulate PKR expression. However, p48 overexpression in combination with interferon-alpha treatment caused a marked increase in PKR expression and augmented the phosphorylation of eIF2alpha, by which the transfected CAT gene translation, as well as the endogenous alpha-fetoprotein synthesis, was blocked without affecting their mRNA levels.

CONCLUSIONS

These results suggest that p48 gene transduction may provide a strategy to enhance the IFN-mediated PKR expression and its activity in hepatocytes.

Efficient in vitro and in vivo excision of floxed sequences with a high-capacity adenoviral vector expressing Cre recombinase

Conditional gene expression or gene disruption using Cre/loxP- or FLP/frt-based recombination systems are valuable tools for studying gene function in development and disease. Recombinant adenoviral vectors expressing Cre recombinase have been suggested as an alternative for deletion of floxed sequences. To further improve this approach we generated a high-capacity adenoviral (HC-Ad) vector expressing Cre (HC-Adcre). In this vector all viral coding sequences are deleted resulting in decreased toxicity. In the present study HC-Adcre efficiently mediated recombination between two loxP sites located in the genome of a reporter cell line. When intravenously injected into ROSA26 reporter mice, a floxed sequence was excised in hepatocytes resulting in expression of the beta-gal reporter. Our data indicate that HC-Ad vectors expressing Cre effectively delete floxed sequences in vivo and have a significant potential as a tool for functional studies in mice.

A novel murine model of Graves' hyperthyroidism with intramuscular injection of adenovirus expressing the thyrotropin receptor

In this work we report a novel method to efficiently induce a murine model of Graves' hyperthyroidism. Inbred mice of different strains were immunized by i.m. injection with adenovirus expressing thyrotropin receptor (TSHR) or beta-galactosidase (1 x 10(11) particles/mouse, three times at 3-wk intervals) and followed up to 8 wk after the third immunization. Fifty-five percent of female and 33% of male BALB/c (H-2(d)) and 25% of female C57BL/6 (H-2(b)) mice developed Graves'-like hyperthyroidism with elevated serum thyroxine (T(4)) levels and positive anti-TSHR autoantibodies with thyroid-stimulating Ig (TSI) and TSH-binding inhibiting Ig (TBII) activities. In contrast, none of female CBA/J (H-2(k)), DBA/1J (H-2(q)), or SJL/J (H-2(s)) mice developed Graves' hyperthyroidism or anti-TSHR autoantibodies except SJL/J, which showed strong TBII activities. There was a significant positive correlation between TSI values and T(4) levels, but the correlations between T(4) and TBII and between TSI and TBII were very weak. TSI activities in sera from hyperthyroid mice measured with some chimeric TSH/lutropin receptors suggested that their epitope(s) on TSHR appeared similar to those in patients with Graves' disease. The thyroid glands from hyperthyroid mice displayed diffuse enlargement with hypertrophy and hypercellularity of follicular epithelia with occasional protrusion into the follicular lumen, characteristics of Graves' hyperthyroidism. Decreased amounts of colloid were also observed. However, there was no inflammatory cell infiltration. Furthermore, extraocular muscles from hyperthyroid mice were normal. Thus, the highly efficient means that we now report to induce Graves' hyperthyroidism in mice will be very useful for studying the pathogenesis of autoimmunity in Graves' disease.