Targeted radionuclide therapy using a Wnt-targeted replicating adenovirus encoding the Na/I symporter

Lipid-Peptide-mRNA Nanoparticles Augment Radioiodine Uptake in Anaplastic Thyroid Cancer

Restoring sodium iodide symporter (NIS) expression and function remains a major challenge for radioiodine therapy in anaplastic thyroid cancer (ATC). For more efficient delivery of messenger RNA (mRNA) to manipulate protein expression, a lipid-peptide-mRNA (LPm) nanoparticle (NP) is developed. The LPm NP is prepared by using amphiphilic peptides to assemble a peptide core and which is then coated with cationic lipids. An amphiphilic chimeric peptide, consisting of nine arginine and hydrophobic segments (6 histidine, C18 or cholesterol), is synthesized for adsorption of mRNA encoding NIS in RNase-free conditions. In vitro studies show that LP(R9H6) m NP is most efficient at delivering mRNA and can increase NIS expression in ATC cells by more than 10-fold. After intratumoral injection of NIS mRNA formulated in optimized LPm NP, NIS expression in subcutaneous ATC tumor tissue increases significantly in nude mice, resulting in more iodine 131 (¹³¹ I) accumulation in the tumor, thereby significantly inhibiting tumor growth. Overall, this work designs three arginine-rich peptide nanoparticles, contributing to the choice of liposome cores for gene delivery. LPm NP can serve as a promising adjunctive therapy for patients with ATC by restoring iodine affinity and enhancing the therapeutic efficacy of radioactive iodine.

Preclinical efficacy of the Wnt/β-catenin pathway inhibitor BC2059 for the treatment of desmoid tumors

Mutation in the CTNNB1 gene, leading to a deregulation of the WTN/β-catenin pathway, is a common feature of desmoid tumors (DTs). Many β-catenin inhibitors have recently been tested in clinical studies; however, BC2059 (also referred as Tegavivint), a selective inhibitor of nuclear β-catenin that works through binding TBL-1, is the only one being evaluated in a clinical study, specifically for treatment of desmoid tumor patients. Preclinical studies on BC2059 have shown activity in multiple myeloma, acute myeloid leukemia and osteosarcoma. Our preclinical studies provide data on the efficacy of BC2059 in desmoid cell lines, which could help provide insight regarding antitumor activity of this therapy in desmoid tumor patients. In vitro activity of BC2059 was evaluated using desmoid tumor cell lines. Ex vivo activity of BC2059 was assessed using an explant tissue culture model. Pharmacological inhibition of the nuclear β-catenin activity using BC2059 markedly inhibited cell viability, migration and invasion of mutated DT cells, but with lower effect on wild-type DTs. The decrease in cell viability of mutated DT cells caused by BC2059 was due to apoptosis. Treatment with BC2059 led to a reduction of β-catenin-associated TBL1 in all mutated DT cells, resulting in a reduction of nuclear β-catenin. mRNA and protein levels of AXIN2, a β-catenin target gene, were also found to be downregulated after BC2059 treatment. Taken together, our results demonstrate that nuclear β-catenin inhibition using BC2059 may be a novel therapeutic strategy for desmoid tumor treatment, especially in patients with CTNNB1 mutation.

Coating an adenovirus with functionalized gold nanoparticles favors uptake, intracellular trafficking and anti-cancer therapeutic efficacy

Adenoviral (Ad) vectors have proven to be important tools for gene and cell therapy, although some issues still need to be addressed, such as undesired interactions with blood components and off-target sequestration that ultimately hamper efficacy. In the past years, several organic and inorganic materials have been developed to reduce immunogenicity and improve biodistribution of Ad vectors. Here we investigated the influence of the functionalization of 14 nm PEGylated gold nanoparticles (AuNPs) with quaternary ammonium groups and an arginine-glycine-aspartic acid (RGD)-motif on the uptake and biodistribution of Ad vectors. We report the formation of Ad@AuNPs complexes that promote cell attachment and uptake, independently of the presence of the coxsackievirus and adenovirus receptor (CAR) and α_vβ₃ and α_vβ₅ integrins, significantly improving transduction without limiting Ad bioactivity. Besides, the presence of the RGD peptide favors tumor targeting and decreases Ad sequestration in the liver. Additionally, tumor delivery of a coated Ad vector expressing the human sodium iodide symporter (hNIS) by mesenchymal stem cells induces increased accumulation of radioactive iodine (¹³¹I) and tumor volume reduction compared to naked Ad-hNIS, highlighting the promising potential of our coating formulation in cancer gene therapy. STATEMENT OF SIGNIFICANCE: Modification of adenoviral vectors with lipids and polymers can reduce interactions with blood components and increase tumor accumulation; however, increased toxicity and reduced transduction efficiency were indicated. Coating with gold nanoparticles has proven to be a successful strategy for increasing the efficiency of transduction of receptor-defective cell lines. Here we explore the contribution of cell surface receptors on the mechanisms of entry of Ad vectors coated with gold nanoparticles in cell lines with varying degrees of resistance to infection. The enhancement of the anti-tumoral effect shown in this work provides new evidence for the potential of our formulation.

Utilization of nanotechnology in targeted radionuclide cancer therapy: monotherapy, combined therapy and radiosensitization

The rapid progress of nanomedicine field has a great influence on the different tumor therapeutic trends. It achieves a potential targeting of the therapeutic agent to the tumor site with neglectable exposure of the normal tissue. In nuclear medicine, nanocarriers have been employed for targeted delivery of therapeutic radioisotopes to the malignant tissues. This systemic radiotherapy is employed to overcome the external radiation therapy drawbacks. This review overviews studies concerned with investigation of different nanoparticles as promising carriers for targeted radiotherapy. It discusses the employment of different nanovehicles for achievement of the synergistic effect of targeted radiotherapy with other tumor therapeutic modalities such as hyperthermia and photodynamic therapy. Radiosensitization utilizing different nanosensitizer loaded nanoparticles has also been discussed briefly as one of the nanomedicine approach in radiotherapy.

Tumor microenvironment affects exogenous sodium/iodide symporter expression

For decades, sodium/iodide symporter NIS-mediated iodide uptake has played a crucial role in the radioactive ablation of thyroid cancer cells. NIS-based gene therapy has also become a promising tool for the treatment of tumors of extrathyroidal origin. But its applicability has been hampered by reduced expression of NIS, resulting in a moderated capacity to accumulate 131I and in inefficient ablation. Despite numerous preclinical enhancement strategies, the understanding of NIS expression within tumors remains limited. This study aims at a better understanding of the functional behavior of exogenous NIS expression in the context of malignant solid tumors that are characterized by rapid growth with an insufficient vasculature, leading to hypoxia and quiescence. Using subcutaneous HT29NIS and K7M2NIS tumors, we show that NIS-mediated uptake and NIS expression at the plasma membrane of cancer cells are impaired in the intratumoral regions. For a better understanding of the underlying molecular mechanisms induced by hypoxia and quiescence (separately and in combination), we performed experiments on HT29NIS cancer cells. Hypoxia and quiescence were both found to impair NIS-mediated uptake through mechanisms including NIS mis-localization. Modifications in the expression of proteins and metabolites involved in plasma membrane localization and in energy metabolism were found using untargeted proteomics and metabolomics approaches. In conclusion, our results provide evidence that hypoxia and quiescence impair NIS expression at the plasma membrane, and iodide uptake. Our study also shows that the tumor microenvironment is an important parameter for successful NIS-based cancer treatment.

Species D Adenoviruses as Oncolytic Viral Vectors

Oncolytic adenoviruses (Ad) have shown promising results in the therapeutic treatment of cancer. Ad type 5 (Ad5) is the most extensively utilized Ad type. However, several limitations exist to using Ad5 as an oncolytic virus, including high levels of anti-Ad5 neutralizing antibodies in the population, binding of the Ad5 hexon to blood coagulation factor X leading to liver sequestration and toxicity, and reduced expression of the primary receptor CAR on many tumors. Here, we use in vitro methods to explore the oncolytic potential of four alternative Ad types (Ad26, 28, 45, and 48) belonging to the species D Ad subgroup and developed replication-competent species D Ads expressing the human sodium iodide symporter protein (hNIS) for combination radiovirotherapy. We evaluated the species D Ad vectors transduction, replication, cytotoxicity, and gene expression in six different cancer cell lines. Species D Ads showed the greatest transduction and cytotoxic killing in the SKBR3 breast cancer cells, followed by 293, A549, and HepG2 cells, however the cytotoxicity was less than the wild type Ad5 virus. In contrast, species D Ads showed limited transduction and cytotoxicity in the Hela and SKOV3 cancer cell lines. These species D Ad vectors also successfully expressed the hNIS gene during infection leading to increased iodide uptake in multiple cancer cell lines. These results, the low seroprevalence of anti-species D antibodies, and the lack of binding to blood coagulation FX, support further exploration of species D Ads as alternative oncolytic adenoviruses against multiple types of cancer.

Preclinical SPECT and SPECT-CT in Oncology

Molecular imaging enables both spatial and temporal understanding of the complex biologic systems underlying carcinogenesis and malignant spread. Single-photon emission tomography (SPECT) is a versatile nuclear imaging-based technique with ideal properties to study these processes in vivo in small animal models, as well as to identify potential drug candidates and characterize their antitumor action and potential adverse effects. Small animal SPECT and SPECT-CT (single-photon emission tomography combined with computer tomography) systems continue to evolve, as do the numerous SPECT radiopharmaceutical agents, allowing unprecedented sensitivity and quantitative molecular imaging capabilities. Several of these advances, their specific applications in oncology as well as new areas of exploration are highlighted in this chapter.

Improving 131I Radioiodine Therapy By Hybrid Polymer-Grafted Gold Nanoparticles

BACKGROUND

Human trials combining external radiotherapy (RT) and metallic nanoparticles are currently underway in cancer patients. For internal RT, in which a radioisotope such as radioiodine is systemically administered into patients, there is also a need for enhancing treatment efficacy, decreasing radiation-induced side effects and overcoming radio-resistance. However, if strategies vectorising radioiodine through nanocarriers have been documented, sensitizing the neoplasm through the use of nanotherapeutics easily translatable to the clinic in combination with the standard systemic radioiodine treatment has not been assessed yet.

METHOD AND MATERIALS

The present study explored the potential of hybrid poly(methacrylic acid)-grafted gold nanoparticles to improve the performances of systemic 131I-mediated RT on cancer cells and in tumor-bearing mice. Such nanoparticles were chosen based on their ability previously described by our group to safely withstand irradiation doses while exhibiting good biocompatibility and enhanced cellular uptake.

RESULTS

In vitro clonogenic assays performed on melanoma and colorectal cancer cells showed that poly(methacrylic acid)-grafted gold nanoparticles (PMAA-AuNPs) could efficiently lead to a marked tumor cell mortality when combined to a low activity of radioiodine, which alone appeared to be essentially ineffective on tumor cells. In vivo, tumor enrichment with PMAA-AuNPs significantly enhanced the killing potential of a systemic radioiodine treatment.

CONCLUSION

This is the first report of a simple and reliable nanomedicine-based approach to reduce the dose of radioiodine required to reach curability. In addition, these results open up novel perspectives for using high-Z metallic NPs in additional molecular radiation therapy demonstrating heterogeneous dose distributions.

TGFB1-driven mesenchymal stem cell-mediated NIS gene transfer

Based on their excellent tumor-homing capacity, genetically engineered mesenchymal stem cells (MSCs) are under investigation as tumor-selective gene delivery vehicles. Transgenic expression of the sodium iodide symporter (NIS) in genetically engineered MSCs allows noninvasive tracking of MSC homing by imaging of functional NIS expression as well as therapeutic application of 131I. The use of tumor stroma-activated promoters can improve tumor-specific MSC-mediated transgene delivery. The essential role of transforming growth factor B1 (TGFB1) and the SMAD downstream target in the signaling between tumor and the surrounding stroma makes the biology of this pathway a potential option to better control NIS expression within the tumor milieu. Bone marrow-derived MSCs were stably transfected with a NIS-expressing plasmid driven by a synthetic SMAD-responsive promoter (SMAD-NIS-MSCs). Radioiodide uptake assays revealed a 4.9-fold increase in NIS-mediated perchlorate-sensitive iodide uptake in SMAD-NIS-MSCs after TGFB1 stimulation compared to unstimulated cells demonstrating the successful establishment of MSCs, which induce NIS expression in response to activation of TGFB1 signaling using a SMAD-responsive promoter. 123I-scintigraphy revealed significant tumor-specific radioiodide accumulation and thus NIS expression after systemic application of SMAD-NIS-MSCs into mice harboring subcutaneous tumors derived from the human hepatocellular carcinoma (HCC) cell line HuH7, which express TGFB1. 131I therapy in SMAD-NIS-MSCs-treated mice demonstrated a significant delay in tumor growth and prolonged survival. Making use of the tumoral TGFB1 signaling network in the context of MSC-mediated NIS gene delivery is a promising approach to foster tumor stroma-selectivity of NIS transgene expression and tailor NIS-based gene therapy to TGFB1-rich tumor environments.

External Beam Radiation Therapy Enhances Mesenchymal Stem Cell-Mediated Sodium-Iodide Symporter Gene Delivery

The tumor-homing properties of mesenchymal stem cells (MSC) have led to their development as delivery vehicles for the targeted delivery of therapeutic genes such as the sodium-iodide symporter (NIS) to solid tumors. External beam radiation therapy may represent an ideal setting for the application of engineered MSC-based gene therapy, as tumor irradiation may enhance MSC recruitment into irradiated tumors through the increased production of select factors linked to MSC migration. In the present study, the irradiation of human liver cancer cells (HuH7; 1-10 Gy) showed a strong dose-dependent increase in steady-state mRNA levels of CXCL8, CXCL12, FGF2, PDGFB, TGFB1, THBS1, and VEGF (0-48 h), which was verified for most factors at the protein level (after 48 h). Radiation effects on directed MSC migration were tested in vitro using a live cell tracking migration assay and supernatants from control and irradiated HuH7 cells. A robust increase in mean forward migration index, mean center of mass, and mean directionality of MSCs toward supernatants was seen from irradiated as compared to non-irradiated tumor cells. Transferability of this effect to other tumor sources was demonstrated using the human breast adenocarcinoma cell line (MDA-MB-231), which showed a similar behavior to radiation as seen with HuH7 cells in quantitative polymerase chain reaction and migration assay. To evaluate this in a more physiologic in vivo setting, subcutaneously growing HuH7 xenograft tumors were irradiated with 0, 2, or 5 Gy followed by CMV-NIS-MSC application 24 h later. Tumoral iodide uptake was monitored using ¹²³I-scintigraphy. The results showed increased tumor-specific dose-dependent accumulation of radioiodide in irradiated tumors. The results demonstrate that external beam radiation therapy enhances the migratory capacity of MSCs and may thus increase the therapeutic efficacy of MSC-mediated NIS radionuclide therapy.

Systemic tumor-targeted sodium iodide symporter (NIS) gene therapy of hepatocellular carcinoma mediated by B6 peptide polyplexes

BACKGROUND

Nonviral polymer-based gene transfer represents an adaptable system for tumor-targeted gene therapy because various design strategies of shuttle systems, together with the mechanistic concept of active tumor targeting, lead to improved gene delivery vectors resulting in higher tumor specificity, efficacy and safety.

METHODS

Using the sodium iodide symporter (NIS) as a theranostic gene, nonviral gene delivery vehicles based on linear polyethylenimine (LPEI), polyethylene glycol (PEG) and coupled to the synthetic peptide B6 (LPEI-PEG-B6), which specifically binds to tumor cells, were investigated in a hepatocellular carcinoma xenograft model for tumor selectivity and transduction efficiency.

RESULTS

In vitro incubation of three different tumor cell lines with LPEI-PEG-B6/NIS resulted in significant increase in iodide uptake activity compared to untargeted and empty vectors. After establishment of subcutaneous HuH7 tumors, NIS-conjugated nanoparticles were injected intravenously followed by analysis of radioiodide biodistribution using ¹²³ I-scintigraphy showing significant perchlorate-sensitive iodide accumulation in tumors of LPEI-PEG-B6/NIS-treated mice (8.0 ± 1.5% ID/g ¹²³ I; biological half-life of 4 h). After four cycles of repetitive polyplex/¹³¹ I applications, a significant delay of tumor growth was observed, which was associated with markedly improved survival in the therapy group.

CONCLUSIONS

These results clearly demonstrate that systemic in vivo NIS gene transfer using nanoparticle vectors coupled to B6 tumor targeting ligand is capable of inducing tumor-specific radioiodide uptake. This promising gene therapy approach opens the exciting prospect of NIS-mediated radionuclide therapy in metastatic cancer, together with the possibility of combining several targeting ligands to enhance selective therapeutic efficacy in a broad field of cancer types with various receptor expression profiles.

Oncolytic Viruses for Tumor Precision Imaging and Radiotherapy

In 2003 in China, Peng et al. invented the recombinant adenovirus expressing p53 (Gendicine) for clinical tumor virotherapy. This was the first clinically approved gene therapy and tumor virotherapy drug in the world. An oncolytic herpes simplex virus expressing granulocyte-macrophage colony-stimulating factor (Talimogene laherparepvec) was approved for melanoma treatment in the United States in 2015. Since then, oncolytic viruses have been attracting more and more attention in the field of oncology, and may become novel significant modalities of tumor precision imaging and radiotherapy after further improvement. Oncolytic viruses carrying reporter genes can replicate and express genes of interest selectively in tumor cells, thus improving in vivo noninvasive precision molecular imaging and radiotherapy. Here, the latest developments and molecular mechanisms of tumor imaging and radiotherapy using oncolytic viruses are reviewed, and perspectives are given for further research. Various types of tumors are discussed, and special attention is paid to gastrointestinal tumors.

The Sodium/Iodide Symporter (NIS): Molecular Physiology and Preclinical and Clinical Applications

Active iodide (I^-) transport in both the thyroid and some extrathyroidal tissues is mediated by the Na⁺/I^- symporter (NIS). In the thyroid, NIS-mediated I^- uptake plays a pivotal role in thyroid hormone (TH) biosynthesis. THs are key during embryonic and postembryonic development and critical for cell metabolism at all stages of life. The molecular characterization of NIS in 1996 and the use of radioactive I^- isotopes have led to significant advances in the diagnosis and treatment of thyroid cancer and provide the molecular basis for studies aimed at extending the use of radioiodide treatment in extrathyroidal malignancies. This review focuses on the most recent findings on I^- homeostasis and I^- transport deficiency-causing NIS mutations, as well as current knowledge of the structure/function properties of NIS and NIS regulatory mechanisms. We also discuss employing NIS as a reporter gene using viral vectors and stem cells in imaging, diagnostic, and therapeutic procedures.

EGFR-targeted nonviral NIS gene transfer for bioimaging and therapy of disseminated colon cancer metastases

Liver metastases present a serious problem in the therapy of advanced colorectal cancer (CRC), as more than 20% of patients have distant metastases at the time of diagnosis with less than 5% being cured. Consequently, new therapeutic approaches are of major need together with high-resolution imaging methods that allow highly specific detection of small metastases.

The unique combination of reporter and therapy gene function of the sodium iodide symporter (NIS) may represent a promising theranostic strategy for CRC liver metastases allowing non-invasive imaging of functional NIS expression and therapeutic application of ¹³¹I.

For targeted NIS gene transfer polymers containing linear polyethylenimine (LPEI), polyethylene glycol (PEG) and the epidermal growth factor receptor (EGFR)-specific ligand GE11 were complexed with human NIS DNA (LPEI-PEG-GE11/NIS). Tumor specificity and transduction efficiency were examined in high EGFR-expressing LS174T metastases by non-invasive imaging using ¹⁸F-tetrafluoroborate (¹⁸F-TFB) as novel NIS PET tracer. Mice that were injected with LPEI-PEG-GE11/NIS 48 h before ¹⁸F-TFB application showed high tumoral levels (4.8±0.6% of injected dose) of NIS-mediated radionuclide uptake in comparison to low levels detected in mice that received untargeted control polyplexes. Three cycles of intravenous injection of EGFR-targeted NIS polyplexes followed by therapeutic application of 55.5 MBq ¹³¹I resulted in marked delay in metastases spread, which was associated with improved animal survival.

In conclusion, these preclinical data confirm the enormous potential of EGFR-targeted synthetic polymers for systemic NIS gene delivery in an advanced multifocal CRC liver metastases model and open the exciting prospect of NIS-mediated radionuclide therapy in metastatic disease.

Positive radionuclide imaging of miRNA expression using RILES and the human sodium iodide symporter as reporter gene is feasible and supports a protective role of miRNA-23a in response to muscular atrophy

MicroRNAs (miRNAs) are key players in many biological processes and are considered as an emerging class of pharmacology drugs for diagnosis and therapy. However to fully exploit the therapeutic potential of miRNAs, it is becoming crucial to monitor their expression pattern using medical imaging modalities. Recently, we developed a method called RILES, for RNAi-Inducible Luciferase Expression System that relies on an engineered regulatable expression system to switch-ON the expression of the luciferase gene when a miRNA of interest is expressed in cells. Here we investigated whether replacing the luciferase reporter gene with the human sodium iodide symporter (hNIS) reporter gene will be also suited to monitor the expression of miRNAs in a clinical setting context. We provide evidence that radionuclide imaging of miRNA expression using hNIS is feasible although it is not as robust as when the luciferase reporter gene is used. However, under appropriate conditions, we monitored the expression of several miRNAs in cells, in the liver and in the tibialis anterior muscle of mice undergoing muscular atrophy. We demonstrated that radiotracer accumulation in transfected cells correlated with the induction of hNIS and with the expression of miRNAs detected by real time PCR. We established the kinetic of miRNA-23a expression in mice and demonstrated that this miRNA follows a biphasic expression pattern characterized by a loss of expression at a late time point of muscular atrophy. At autopsy, we found an opposite expression pattern between miRNA-23a and one of the main transcriptional target of this miRNA, APAF-1, and as downstream target, Caspase 9. Our results report the first positive monitoring of endogenously expressed miRNAs in a nuclear medicine imaging context and support the development of additional work to establish the potential therapeutic value of miRNA-23 to prevent the damaging effects of muscular atrophy.

Single-Photon Emission Computed Tomography for Preclinical Assessment of Thyroid Radioiodide Uptake Following Various Combinations of Preparative Measures

BACKGROUND

MicroSPECT/CT imaging was used to quantitatively evaluate how iodide uptake in the mouse thyroid is influenced by (i) route of iodine administration; (ii) injection of recombinant human thyrotropin (rhTSH); and (iii) low iodide diet (LID) in euthyroid and triiodothyronine (T3)-treated mice.

METHODS

Pertechnetate (^99mTcO₄^-) and ¹²³I thyroid uptake in euthyroid and T3-treated animals fed either a normal-iodine diet (NID) or an LID, treated or not with rhTSH, and radiotracer administered intravenously, subcutaneously, intraperitoneally or by gavage, were assessed using microSPECT/CT imaging. Western blotting was performed to measure sodium/iodide symporter expression levels in the thyroid.

RESULTS

Systemic administration of radioiodide resulted in a higher (2.35-fold in NID mice) accumulation of iodide in the thyroid than oral administration. Mice fed LID with systemic radioiodide administration showed a further two-fold increase in thyroid iodide uptake to yield a ∼5-fold increase in uptake compared to the standard NID/oral route. Although rhTSH injections stimulated thyroid activity in both euthyroid and T3-treated mice fed the NID, uptake levels for T3-treated mice remained low compared with those for the euthyroid mice. Combining LID and rhTSH in T3-treated mice resulted in a 2.8-fold higher uptake compared with NID/T3/rhTSH mice and helped restore thyroid activity to levels equivalent to those of euthyroid animals.

CONCLUSIONS

Systemic radioiodide administration results in higher thyroidal iodide levels than oral administration, particularly in LID-fed mice. These data highlight the importance of LID, both in euthyroid and T3-treated, rhTSH-injected mice. Extrapolated to human patients, and in the context of clinical guidelines for the preparation of differentiated thyroid cancer patients, our data indicate that LID can potentiate the efficacy of rhTSH treatment in T3-treated patients.

Sequence-defined cMET/HGFR-targeted Polymers as Gene Delivery Vehicles for the Theranostic Sodium Iodide Symporter (NIS) Gene

The sodium iodide symporter (NIS) as well-characterized theranostic gene represents an outstanding tool to target different cancer types allowing noninvasive imaging of functional NIS expression and therapeutic radioiodide application. Based on its overexpression on the surface of most cancer types, the cMET/hepatocyte growth factor receptor serves as ideal target for tumor-selective gene delivery. Sequence-defined polymers as nonviral gene delivery vehicles comprising polyethylene glycol (PEG) and cationic (oligoethanoamino) amide cores coupled with a cMET-binding peptide (cMBP2) were complexed with NIS-DNA and tested for receptor-specificity, transduction efficiency, and therapeutic efficacy in hepatocellular cancer cells HuH7. In vitro iodide uptake studies demonstrated high transduction efficiency and cMET-specificity of NIS-encoding polyplexes (cMBP2-PEG-Stp/NIS) compared to polyplexes without targeting ligand (Ala-PEG-Stp/NIS) and without coding DNA (cMBP2-PEG-Stp/Antisense-NIS). Tumor recruitment and vector biodistribution were investigated in vivo in a subcutaneous xenograft mouse model showing high tumor-selective iodide accumulation in cMBP2-PEG-Stp/NIS-treated mice (6.6 ± 1.6% ID/g (123)I, biological half-life 3 hours) by (123)I-scintigraphy. Therapy studies with three cycles of polyplexes and (131)I application resulted in significant delay in tumor growth and prolonged survival. These data demonstrate the enormous potential of cMET-targeted sequence-defined polymers combined with the unique theranostic function of NIS allowing for optimized transfection efficiency while eliminating toxicity.

The use of the NIS reporter gene for optimizing oncolytic virotherapy

Introduction: Oncolytic viruses are experimental cancer therapies being translated to the clinic. They are unique in their ability to amplify within the body, therefore requiring careful monitoring of viral replication and biodistribution. Traditional monitoring strategies fail to recapitulate the dynamic nature of oncolytic virotherapy. Consequently, clinically relevant, noninvasive, high resolution strategies are needed to effectively track virotherapy in real time.

Areas covered: The expression of the sodium iodide symporter (NIS) reporter gene is tightly coupled to viral genome replication and mediates radioisotope concentration, allowing noninvasive molecular nuclear imaging of active viral infection with high resolution. This provides insight into replication kinetics, biodistribution, the impact of vector design, administration, and dosing on therapeutic outcomes, and highlights the heterogeneity of spatial distribution and temporal evolution of infection. NIS-mediated imaging in clinical trials confirms the feasibility of this technology to noninvasively and longitudinally observe oncolytic virus infection, replication, and distribution.

Expert opinion: NIS-mediated imaging provides detailed functional and molecular information on the evolution of oncolytic virus infection in living animals. The use of NIS reporter gene imaging has rapidly advanced to provide unparalleled insight into the spatial and temporal context of oncolytic infection which will be integral to optimization of oncolytic treatment strategies.

Mesenchymal stem cell-mediated, tumor stroma-targeted radioiodine therapy of metastatic colon cancer using the sodium iodide symporter as theranostic gene

The tumor-homing property of mesenchymal stem cells (MSCs) allows targeted delivery of therapeutic genes into the tumor microenvironment. The application of sodium iodide symporter (NIS) as a theranostic gene allows noninvasive imaging of MSC biodistribution and transgene expression before therapeutic radioiodine application. We have previously shown that linking therapeutic transgene expression to induction of the chemokine CCL5/RANTES allows a more focused expression within primary tumors, as the adoptively transferred MSC develop carcinoma-associated fibroblast-like characteristics. Although RANTES/CCL5-NIS targeting has shown efficacy in the treatment of primary tumors, it was not clear if it would also be effective in controlling the growth of metastatic disease.

METHODS

To expand the potential range of tumor targets, we investigated the biodistribution and tumor recruitment of MSCs transfected with NIS under control of the RANTES/CCL5 promoter (RANTES-NIS-MSC) in a colon cancer liver metastasis mouse model established by intrasplenic injection of the human colon cancer cell line LS174t. RANTES-NIS-MSCs were injected intravenously, followed by (123)I scintigraphy, (124)I PET imaging, and (131)I therapy.

RESULTS

Results show robust MSC recruitment with RANTES/CCL5-promoter activation within the stroma of liver metastases as evidenced by tumor-selective iodide accumulation, immunohistochemistry, and real-time polymerase chain reaction. Therapeutic application of (131)I in RANTES-NIS-MSC-treated mice resulted in a significant delay in tumor growth and improved overall survival.

CONCLUSION

This novel gene therapy approach opens the prospect of NIS-mediated radionuclide therapy of metastatic cancer after MSC-mediated gene delivery.

Molecular imaging of oncolytic viral therapy

Oncolytic viruses have made their mark on the cancer world as a potential therapeutic option, with the possible advantages of reduced side effects and strengthened treatment efficacy due to higher tumor selectivity. Results have been so promising, that oncolytic viral treatments have now been approved for clinical trials in several countries. However, clinical studies may benefit from the ability to noninvasively and serially identify sites of viral targeting via molecular imaging in order to provide safety, efficacy, and toxicity information. Furthermore, molecular imaging of oncolytic viral therapy may provide a more sensitive and specific diagnostic technique to detect tumor origin and, more importantly, presence of metastases. Several strategies have been investigated for molecular imaging of viral replication broadly categorized into optical and deep tissue imaging, utilizing several reporter genes encoding for fluorescence proteins, conditional enzymes, and membrane protein and transporters. Various imaging methods facilitate molecular imaging, including computer tomography, magnetic resonance imaging, positron emission tomography, single photon emission CT, gamma-scintigraphy, and photoacoustic imaging. In addition, several molecular probes are used for medical imaging, which act as targeting moieties or signaling agents. This review will explore the preclinical and clinical use of in vivo molecular imaging of replication-competent oncolytic viral therapy.

Targeting the Wnt pathway in human cancers: therapeutic targeting with a focus on OMP-54F28

The Wnt signaling pathways are a group of signal transduction pathways that play an important role in cell fate specification, cell proliferation and cell migration. Aberrant signaling in these pathways has been implicated in the development and progression of multiple cancers by allowing increased proliferation, angiogenesis, survival and metastasis. Activation of the Wnt pathway also contributes to the tumorigenicity of cancer stem cells (CSCs). Therefore, inhibiting this pathway has been a recent focus of cancer research with multiple targetable candidates in development. OMP-54F28 is a fusion protein that combines the cysteine-rich domain of frizzled family receptor 8 (Fzd8) with the immunoglobulin Fc domain that competes with the native Fzd8 receptor for its ligands and antagonizes Wnt signaling. Preclinical models with OMP-54F28 have shown reduced tumor growth and decreased CSC frequency as a single agent and in combination with other chemotherapeutic agents. Due to these findings, a phase 1a study is nearing completion with OMP-54F28 in advanced solid tumors and 3 phase 1b studies have been opened with OMP-54F28 in combination with standard-of-care chemotherapy backbones in ovarian, pancreatic and hepatocellular cancers. This article will review the Wnt signaling pathway, preclinical data on OMP-54F28 and other Wnt pathway inhibitors and ongoing clinical trials.

Current Understanding on EGFR and Wnt/β-Catenin Signaling in Glioma and Their Possible Crosstalk

Glioblastoma multiformes (GBMs) are extensively heterogeneous at both cellular and molecular levels. Current therapeutic strategies include targeting of key signaling molecules using pharmacological inhibitors in combination with genotoxic agents such as temozolomide. In spite of all efforts, the prognosis of glioma patients remains dismal. Therefore, a proper understanding of individual molecular pathways responsible for the progression of GBM is necessary. The epidermal growth factor receptor (EGFR) pathway is probably the most significant signaling pathway clinically implicated in glioma. Not surprisingly, anti-EGFR therapies mostly prevail for therapeutic purposes. The Wnt/β-catenin pathway is well implicated in multiple tumors; however, its role in glioma has only recently started to emerge. We give a concise account of the current understanding of the role of both these pathways in glioma. Last, taking evidences from a limited literature, we outline a number of points where these pathways intersect each other and put forward the possibility of combinatorially targeting them for treatment of glioma.

Sodium iodide symporter (NIS) in extrathyroidal malignancies: focus on breast and urological cancer

Background

Expression and function of sodium iodide symporter (NIS) is requisite for efficient iodide transport in thyrocytes, and its presence in cancer cells allows the use of radioiodine as a diagnostic and therapeutic tool in thyroid neoplasia. Discovery of NIS expression in extrathyroidal tissues, including transformed cells, has opened a novel field of research regarding NIS-expressing extrathyroidal neoplasia. Indeed, expression of NIS may be used as a biomarker for diagnostic, prognostic, and therapeutic purposes. Moreover, stimulation of endogenous NIS expression may permit the radioiodine treatment of extrathyroidal lesions by concentrating this radioisotope.

Results

This review describes recent findings in NIS research in extrathyroidal malignancies, focusing on breast and urological cancer, emphasizing the most relevant developments that may have clinical impact.

Conclusions

Given the recent progress in the study of NIS regulation as molecular basis for new therapeutic approaches in extrathyroidal cancers, particular attention is given to studies regarding the relationship between NIS and clinical-pathological aspects of the tumors and the regulation of NIS expression in the experimental models.

⁹⁹mTcO₄--, auger-mediated thyroid stunning: dosimetric requirements and associated molecular events

Low-energy Auger and conversion electrons deposit their energy in a very small volume (a few nm³) around the site of emission. From a radiotoxicological point of view the effects of low-energy electrons on normal tissues are largely unknown, understudied, and generally assumed to be negligible. In this context, the discovery that the low-energy electron emitter, ^99mTc, can induce stunning on primary thyrocytes in vitro, at low absorbed doses, is intriguing. Extrapolated in vivo, this observation suggests that a radioisotope as commonly used in nuclear medicine as ^99mTc may significantly influence thyroid physiology. The aims of this study were to determine whether ^99mTc pertechnetate (^99mTcO₄⁻) is capable of inducing thyroid stunning in vivo, to evaluate the absorbed dose of ^99mTcO₄⁻ required to induce this stunning, and to analyze the biological events associated/concomitant with this effect. Our results show that ^99mTcO₄⁻–mediated thyroid stunning can be observed in vivo in mouse thyroid. The threshold of the absorbed dose in the thyroid required to obtain a significant stunning effect is in the range of 20 Gy. This effect is associated with a reduced level of functional Na/I symporter (NIS) protein, with no significant cell death. It is reversible within a few days. At the cellular and molecular levels, a decrease in NIS mRNA, the generation of double-strand DNA breaks, and the activation of the p53 pathway are observed. Low-energy electrons emitted by ^99mTc can, therefore, induce thyroid stunning in vivo in mice, if it is exposed to an absorbed dose of at least 20 Gy, a level unlikely to be encountered in clinical practice. Nevertheless this report presents an unexpected effect of low-energy electrons on a normal tissue in vivo, and provides a unique experimental setup to understand the fine molecular mechanisms involved in their biological effects.

Monitoring of biodistribution and persistence of conditionally replicative adenovirus in a murine model of ovarian cancer using capsid-incorporated mCherry and expression of human somatostatin receptor subtype 2 gene

A significant limiting factor to the human clinical application of conditionally replicative adenovirus (CRAd)-based virotherapy is the inability to noninvasively monitor these agents and their potential persistence. To address this issue, we proposed a novel imaging approach that combines transient expression of the human somatostatin receptor (SSTR) subtype 2 reporter gene with genetic labeling of the viral capsid with mCherry fluorescent protein. To test this dual modality system, we constructed the Ad5/3Δ24pIXcherry/SSTR CRAd and validated its capacity to generate fluorescent and nuclear signals in vitro and following intratumoral injection. Analysis of 64Cu-CB-TE2A-Y3-TATE biodistribution in mice revealed reduced uptake in tumors injected with the imaging CRAd relative to the replication-incompetent, Ad-expressing SSTR2 but significantly greater uptake compared to the negative CRAd control. Optical imaging demonstrated relative correlation of fluorescent signal with virus replication as determined by viral genome quantification in tumors. Positron emission tomography/computed tomography studies demonstrated that we can visualize radioactive uptake in tumors injected with imaging CRAd and the trend for greater uptake by standardized uptake value analysis compared to control CRAd. In the aggregate, the plasticity of our dual imaging approach should provide the technical basis for monitoring CRAd biodistribution and persistence in preclinical studies while offering potential utility for a range of clinical applications.

Stromal targeting of sodium iodide symporter using mesenchymal stem cells allows enhanced imaging and therapy of hepatocellular carcinoma

The tumor-homing property of mesenchymal stem cells (MSC) has lead to their use as delivery vehicles for therapeutic genes. The application of the sodium iodide symporter (NIS) as therapy gene allows noninvasive imaging of functional transgene expression by (123)I-scintigraphy or PET-imaging, as well as therapeutic application of (131)I or (188)Re. Based on the critical role of the chemokine RANTES (regulated on activation, normal T-cell expressed and presumably secreted)/CCL5 secreted by MSCs in the course of tumor stroma recruitment, use of the RANTES/CCL5 promoter should allow tumor stroma-targeted expression of NIS after MSC-mediated delivery. Using a human hepatocellular cancer (HCC) xenograft mouse model (Huh7), we investigated distribution and tumor recruitment of RANTES-NIS-engineered MSCs after systemic injection by gamma camera imaging. (123)I-scintigraphy revealed active MSC recruitment and CCL5 promoter activation in the tumor stroma of Huh7 xenografts (6.5% ID/g (123)I, biological half-life: 3.7 hr, tumor-absorbed dose: 44.3 mGy/MBq). In comparison, 7% ID/g (188)Re was accumulated in tumors with a biological half-life of 4.1 hr (tumor-absorbed dose: 128.7 mGy/MBq). Administration of a therapeutic dose of (131)I or (188)Re (55.5 MBq) in RANTES-NIS-MSC-treated mice resulted in a significant delay in tumor growth and improved survival without significant differences between (131)I and (188)Re. These data demonstrate successful stromal targeting of NIS in HCC tumors by selective recruitment of NIS-expressing MSCs and by use of the RANTES/CCL5 promoter. The resulting tumor-selective radionuclide accumulation was high enough for a therapeutic effect of (131)I and (188)Re opening the exciting prospect of NIS-mediated radionuclide therapy of metastatic cancer using genetically engineered MSCs as gene delivery vehicles.

Systemic image-guided liver cancer radiovirotherapy using dendrimer-coated adenovirus encoding the sodium iodide symporter as theranostic gene

Currently, major limitations for the clinical application of adenovirus-mediated gene therapy are high prevalence of neutralizing antibodies, widespread expression of the coxsackie-adenovirus receptor (CAR), and adenovirus sequestration by the liver. In the current study, we used the sodium iodide symporter (NIS) as a theranostic gene to investigate whether coating of adenovirus with synthetic dendrimers could be useful to overcome these hurdles in order to develop adenoviral vectors for combination of systemic oncolytic virotherapy and NIS-mediated radiotherapy.

METHODS

We coated replication-deficient (Ad5-CMV/NIS) (CMV is cytomegalovirus) and replication-selective (Ad5-E1/AFP-E3/NIS) adenovirus serotype 5 carrying the hNIS gene with poly(amidoamine) dendrimers generation 5 (PAMAM-G5) in order to investigate transduction efficacy and altered tropism of these coated virus particles by (123)I scintigraphy and to evaluate their therapeutic potential for systemic radiovirotherapy in a liver cancer xenograft mouse model.

RESULTS

After dendrimer coating, Ad5-CMV/NIS demonstrated partial protection from neutralizing antibodies and enhanced transduction efficacy in CAR-negative cells in vitro. In vivo (123)I scintigraphy of nude mice revealed significantly reduced levels of hepatic transgene expression after intravenous injection of dendrimer-coated Ad5-CMV/NIS (dcAd5-CMV/NIS). Evasion from liver accumulation resulted in significantly reduced liver toxicity and increased transduction efficiency of dcAd5-CMV/NIS in hepatoma xenografts. After PAMAM-G5 coating of the replication-selective Ad5-E1/AFP-E3/NIS, a significantly enhanced oncolytic effect was observed after intravenous application (virotherapy) that was further increased by additional treatment with a therapeutic dose of (131)I (radiovirotherapy) and was associated with markedly improved survival.

CONCLUSION

These results demonstrate efficient liver detargeting and tumor retargeting of adenoviral vectors after coating with synthetic dendrimers, thereby representing a promising innovative strategy for systemic NIS gene therapy. Moreover, our study-based on the function of NIS as a theranostic gene allowing the noninvasive imaging of NIS expression by (123)I scintigraphy-provides detailed characterization of in vivo vector biodistribution and localization, level, and duration of transgene expression, essential prerequisites for exact planning and monitoring of clinical gene therapy trials that aim to individualize the NIS gene therapy concept.

Adrenal gland infection by serotype 5 adenovirus requires coagulation factors

Recombinant, replication-deficient serotype 5 adenovirus infects the liver upon in vivo, systemic injection in rodents. This infection requires the binding of factor X to the capsid of this adenovirus. Another organ, the adrenal gland is also infected upon systemic administration of Ad, however, whether this infection is dependent on the cocksackie adenovirus receptor (CAR) or depends on the binding of factor X to the viral capsid remained to be determined. In the present work, we have used a pharmacological agent (warfarin) as well as recombinant adenoviruses lacking the binding site of Factor X to elucidate this mechanism in mice. We demonstrate that, as observed in the liver, adenovirus infection of the adrenal glands in vivo requires Factor X. Considering that the level of transduction of the adrenal glands is well-below that of the liver and that capsid-modified adenoviruses are unlikely to selectively infect the adrenal glands, we have used single-photon emission computed tomography (SPECT) imaging of gene expression to determine whether local virus administration (direct injection in the kidney) could increase gene transfer to the adrenal glands. We demonstrate that direct injection of the virus in the kidney increases gene transfer in the adrenal gland but liver transduction remains important. These observations strongly suggest that serotype 5 adenovirus uses a similar mechanism to infect liver and adrenal gland and that selective transgene expression in the latter is more likely to be achieved through transcriptional targeting.

Differential biodistribution of oncolytic poxvirus administered systemically in an autochthonous model of hepatocellular carcinoma

BACKGROUND

Preclinical studies have demonstrated that, unlike oncolytic adenoviruses, oncolytic vaccinia viruses can reach implanted tumors upon systemic injection. However, the biodistribution of this oncolytic agent in in situ autochthonous tumor models remains poorly characterized. In the present study, we assessed this biodistribution in a model of mouse hepatocellular carcinoma (HCC) obtained after injection of the carcinogen diethylnitrosamine (DEN).

METHODS

Twelve months after DEN administration, histology, quantitative reverse transcription-polymerase chain reaction, in situ hybridization and viral titration were used to characterize tumors, as well as to assess the viral load of the livers upon either intravenous or intraperitoineal injection.

RESULTS

The results obtained showed that the architecture of the liver was lost, with a noticeable absence of sinusoids, as well as the presence of steatosis and α-fetoprotein-positive HCC tumor nodules. Bioluminescence imaging and measures of the infective virus load demonstrated that intravenous injection of 10(8)  plaque-forming units of the recombinant vaccinia virus led to a predominant transduction of the liver, whereas intraperitoneal injection resulted in a lower level of liver transduction accompanied by an increased infection of the lungs, spleen, kidneys and bowels. Immunohistochemical analysis of liver sections of animals injected intravenously with the virus revealed a preferential localization of vaccinia-specific immunoreactivity in the tumors.

CONCLUSIONS

The findings of the present study emphasize the importance of the route of administration of the vector and highlight the relevance of systemic injection of oncolytic vaccinia virus in the context of hepatocellular carcinoma.

A vaccinia virus encoding the human sodium iodide symporter facilitates long-term image monitoring of virotherapy and targeted radiotherapy of pancreatic cancer

To assess therapeutic response and potential toxicity of oncolytic virotherapy, a noninvasive, deep-tissue imaging modality is needed. This study aimed to assess the feasibility, parameters, and determining factors of serial imaging and long-term monitoring of virotherapy and the therapeutic response of pancreatic cancer xenografts treated with a vaccinia virus carrying the human sodium iodide symporter GLV-1h153.

METHODS

Pancreatic cancer xenografts (PANC-1) in nude mice were treated systemically or intratumorally with GLV-1h153 and serially imaged using (124)I PET at 1, 2, 3, and 5 wk after viral injection. Signal intensity was compared with tumor therapeutic response and optical imaging, and tumors were histologically analyzed for morphology and the presence of virus. Autoradiography was performed using technetium-pertechnetate and γ-scintigraphy to assess determining factors for radiouptake in tumors. Finally, the enhanced therapeutic effect of combination therapy with GLV-1h153 and systemic radioiodine was assessed.

RESULTS

GLV-1h153 successfully facilitated serial long-term imaging of virotherapy, with PET signal intensity correlating to tumor response. GLV-1h153 colonization of tumors mediated radioiodine uptake at potentially therapeutic doses. Successful radiouptake required the presence of virus, adequate blood flow, and viable tissue, whereas loss of signal intensity was linked to tumor death and necrosis. Finally, combining systemically administered GLV-1h153 and (131)I led to enhanced tumor kill when compared with virus or (131)I alone (P < 0.01).

CONCLUSION

GLV-1h153 is a promising oncolytic agent for the treatment, long-term imaging, and monitoring of therapeutic response in a xenograft model of pancreatic cancer. GLV-1h153 provided insight into tumor biologic activity and facilitated enhanced tumor kill when combined with systemic targeted radiotherapy. These results warrant further investigation into parameters and potential synergistic effects of combination therapy.

Sodium iodide symporter (NIS)-mediated radiovirotherapy of hepatocellular cancer using a conditionally replicating adenovirus

In this study, we determined the in vitro and in vivo efficacy of sodium iodide symporter (NIS) gene transfer and the therapeutic potential of oncolytic virotherapy combined with radioiodine therapy using a conditionally replicating oncolytic adenovirus. For this purpose, we used a replication-selective adenovirus in which the E1a gene is driven by the mouse alpha-fetoprotein (AFP) promoter and the human NIS gene is inserted in the E3 region (Ad5-E1/AFP-E3/NIS). Human hepatocellular carcinoma cells (HuH7) infected with Ad5-E1/AFP-E3/NIS concentrated radioiodine at a level that was sufficiently high for a therapeutic effect in vitro. In vivo experiments demonstrated that 3 days after intratumoral (i.t.) injection of Ad5-E1/AFP-E3/NIS HuH7 xenograft tumors accumulated approximately 25% ID g(-1) (percentage of the injected dose per gram tumor tissue) (123)I as shown by (123)I gamma camera imaging. A single i.t. injection of Ad5-E1/AFP-E3/NIS (virotherapy) resulted in a significant reduction of tumor growth and prolonged survival, as compared with injection of saline. Combination of oncolytic virotherapy with radioiodine treatment (radiovirotherapy) led to an additional reduction of tumor growth that resulted in markedly improved survival as compared with virotherapy alone. In conclusion, local in vivo NIS gene transfer using a replication-selective oncolytic adenovirus is able to induce a significant therapeutic effect, which can be enhanced by additional (131)I application.

Imaging characteristics, tissue distribution, and spread of a novel oncolytic vaccinia virus carrying the human sodium iodide symporter

Introduction

Oncolytic viruses show promise for treating cancer. However, to assess therapy and potential toxicity, a noninvasive imaging modality is needed. This study aims to determine the in vivo biodistribution, and imaging and timing characteristics of a vaccinia virus, GLV-1h153, encoding the human sodium iodide symporter (hNIS.

Methods

GLV-1h153 was modified from GLV-1h68 to encode the hNIS gene. Timing of cellular uptake of radioiodide ¹³¹I in human pancreatic carcinoma cells PANC-1 was assessed using radiouptake assays. Viral biodistribution was determined in nude mice bearing PANC-1 xenografts, and infection in tumors confirmed histologically and optically via Green Fluorescent Protein (GFP) and bioluminescence. Timing characteristics of enhanced radiouptake in xenografts were assessed via ¹²⁴I-positron emission tomography (PET). Detection of systemic administration of virus was investigated with both ¹²⁴I-PET and 99m-technecium gamma-scintigraphy.

Results

GLV-1h153 successfully facilitated time-dependent intracellular uptake of ¹³¹I in PANC-1 cells with a maximum uptake at 24 hours postinfection (P<0.05). In vivo, biodistribution profiles revealed persistence of virus in tumors 5 weeks postinjection at 10⁹ plaque-forming unit (PFU)/gm tissue, with the virus mainly cleared from all other major organs. Tumor infection by GLV-1h153 was confirmed via optical imaging and histology. GLV-1h153 facilitated imaging virus replication in tumors via PET even at 8 hours post radiotracer injection, with a mean %ID/gm of 3.82±0.46 (P<0.05) 2 days after intratumoral administration of virus, confirmed via tissue radiouptake assays. One week post systemic administration, GLV-1h153-infected tumors were detected via ¹²⁴I-PET and 99m-technecium-scintigraphy.

Conclusion

GLV-1h153 is a promising oncolytic agent against pancreatic cancer with a promising biosafety profile. GLV-1h153 facilitated time-dependent hNIS-specific radiouptake in pancreatic cancer cells, facilitating detection by PET with both intratumoral and systemic administration. Therefore, GLV-1h153 is a promising candidate for the noninvasive imaging of virotherapy and warrants further study into longterm monitoring of virotherapy and potential radiocombination therapies with this treatment and imaging modality.

The sodium iodide symporter (NIS) as an imaging reporter for gene, viral, and cell-based therapies

Preclinical and clinical tomographic imaging systems increasingly are being utilized for non-invasive imaging of reporter gene products to reveal the distribution of molecular therapeutics within living subjects. Reporter gene and probe combinations can be employed to monitor vectors for gene, viral, and cell-based therapies. There are several reporter systems available; however, those employing radionuclides for positron emission tomography (PET) or singlephoton emission computed tomography (SPECT) offer the highest sensitivity and the greatest promise for deep tissue imaging in humans. Within the category of radionuclide reporters, the thyroidal sodium iodide symporter (NIS) has emerged as one of the most promising for preclinical and translational research. NIS has been incorporated into a remarkable variety of viral and non-viral vectors in which its functionality is conveniently determined by in vitro iodide uptake assays prior to live animal imaging. This review on the NIS reporter will focus on 1) differences between endogenous NIS and heterologously-expressed NIS, 2) qualitative or comparative use of NIS as an imaging reporter in preclinical and translational gene therapy, oncolytic viral therapy, and cell trafficking research, and 3) use of NIS as an absolute quantitative reporter.

The sodium iodide symporter (NIS): regulation and approaches to targeting for cancer therapeutics

Expression of the sodium iodide symporter (NIS) is required for efficient iodide uptake in thyroid and lactating breast. Since most differentiated thyroid cancer expresses NIS, β-emitting radioactive iodide is routinely utilized to target remnant thyroid cancer and metastasis after total thyroidectomy. Stimulation of NIS expression by high levels of thyroid-stimulating hormone is necessary to achieve radioiodide uptake into thyroid cancer that is sufficient for therapy. The majority of breast cancer also expresses NIS, but at a low level insufficient for radioiodine therapy. Retinoic acid is a potent NIS inducer in some breast cancer cells. NIS is also modestly expressed in some non-thyroidal tissues, including salivary glands, lacrimal glands and stomach. Selective induction of iodide uptake is required to target tumors with radioiodide. Iodide uptake in mammalian cells is dependent on the level of NIS gene expression, but also successful translocation of NIS to the cell membrane and correct insertion. The regulatory mechanisms of NIS expression and membrane insertion are regulated by signal transduction pathways that differ by tissue. Differential regulation of NIS confers selective induction of functional NIS in thyroid cancer cells, as well as some breast cancer cells, leading to more efficient radioiodide therapy for thyroid cancer and a new strategy for breast cancer therapy. The potential for systemic radioiodide treatment of a range of other cancers, that do not express endogenous NIS, has been demonstrated in models with tumor-selective introduction of exogenous NIS.

Drugging Wnt signalling in cancer

Aberrant regulation of the Wnt signalling pathway has emerged as a prevalent theme in cancer biology. This chapter summarizes the research that provides a proof of concept for inhibiting Wnt signalling in cancer, the potential means by which this could be achieved, and some recent advances towards this goal. A brief discussion of molecular diagnostics and possible safety concerns is also provided.

Normalisation to blood activity is required for the accurate quantification of Na/I symporter ectopic expression by SPECT/CT in individual subjects

The utilisation of the Na/I symporter (NIS) and associated radiotracers as a reporter system for imaging gene expression is now reaching the clinical setting in cancer gene therapy applications. However, a formal assessment of the methodology in terms of normalisation of the data still remains to be performed, particularly in the context of the assessment of activities in individual subjects in longitudinal studies. In this context, we administered to mice a recombinant, replication-incompetent adenovirus encoding rat NIS, or a human colorectal carcinoma cell line (HT29) encoding mouse NIS. We used (99m)Tc pertechnetate as a radiotracer for SPECT/CT imaging to determine the pattern of ectopic NIS expression in longitudinal kinetic studies. Some animals of the cohort were culled and NIS expression was measured by quantitative RT-PCR and immunohistochemistry. The radioactive content of some liver biopsies was also measured ex vivo. Our results show that in longitudinal studies involving datasets taken from individual mice, the presentation of non-normalised data (activity expressed as %ID/g or %ID/cc) leads to 'noisy', and sometimes incoherent, results. This variability is due to the fact that the blood pertechnetate concentration can vary up to three-fold from day to day. Normalisation of these data with blood activities corrects for these inconsistencies. We advocate that, blood pertechnetate activity should be determined and used to normalise the activity measured in the organ/region of interest that expresses NIS ectopically. Considering that NIS imaging has already reached the clinical setting in the context of cancer gene therapy, this normalisation may be essential in order to obtain accurate and predictive information in future longitudinal clinical studies in biotherapy.

SPECT/CT imaging of hNIS-expression after intravenous delivery of an oncolytic adenovirus and 131I

Oncolytic adenoviruses can be engineered for better tumor selectivity, gene delivery and be armed for imaging and concentrating radionuclides into tumors for synergistic oncolysis. We constructed Ad5/3-hTERT-hNIS where replication is controlled by hTERT-promoter. Ad5/3-hTERT-hNIS expresses hNIS for imaging of transgene expression and for treatment of infected tumors by radioiodine. Ad5/3-hTERT-hNIS efficiently killed prostate cancer cells and induced iodine uptake in vitro and in vivo after intratumoral virus administration. Survival of mice treated with intravenous Ad5/3-hTERT-hNIS significantly prolonged survival over mock or radioiodine only but the combination of virus with radioiodine was not more effective than virus alone. Temporal and spatial changes in hNIS-expression during therapy were detected with SPECT, demonstrating feasibility of evaluation of the combination therapy with hNIS-expressing adenoviruses and radioiodide.

In vivo positron emission tomography imaging using the sodium iodide symporter as a reporter gene

Information regarding the biodistribution and kinetics of spread of oncolytic viruses is crucial for safety considerations in the design of future, more efficient reagents. Although optical imaging can be used to gain this information in rodent models, imaging with radioactive isotopes presents the advantage of being directly applicable to humans, and preclinical imaging data can provide a basis for the design of clinical protocols. In this chapter, we describe the use of the Na/I symporter as a reporter gene, associated with (124)I-NaI as a radiotracer, to monitor the anatomical localization, as well as the propagation, of oncolytic viruses using dedicated, preclinical positron emission tomography scanners.

Oncolytic adenoviruses armed with thymidine kinase can be traced by PET imaging and show potent antitumoural effects by ganciclovir dosing

Replication-competent adenoviruses armed with thymidine kinase (TK) combine the concepts of virotherapy and suicide gene therapy. Moreover TK-activity can be detected by noninvasive positron emission-computed tomography (PET) imaging, what could potentially facilitate virus monitoring in vivo. Here, we report the generation of a novel oncolytic adenovirus that incorporates the Tat8-TK gene under the control of the Major Late Promoter in a highly selective backbone thus providing selectivity by targeting the retinoblastoma pathway. The selective oncolytic TK virus, termed ICOVIR5-TK-L, showed reduced potency compared to a non-selective counterpart. However the combination of ICOVIR5-TK-L with ganciclovir (GCV) induced a potent antitumoural effect similar to that of wild type adenovirus in a preclinical model of pancreatic cancer. Although the treatment with GCV provoked a reduction in the viral yield, both in vitro and in vivo, a two-cycle treatment of virus and GCV resulted in an enhanced antitumoral response that correlated with high TK-activity, based on microPET measurements. Thus, TK-expressing oncolytic adenoviruses can be traced by PET imaging providing real time information on the activity of the virus and its antitumoral potency can be optimized by GCV dosing.

Image-guided tumor-selective radioiodine therapy of liver cancer after systemic nonviral delivery of the sodium iodide symporter gene

We reported the induction of tumor-selective iodide uptake and therapeutic efficacy of (131)I in a hepatocellular carcinoma (HCC) xenograft mouse model, using novel polyplexes based on linear polyethylenimine (LPEI), shielded by polyethylene glycol (PEG), and coupled with the epidermal growth factor receptor-specific peptide GE11 (LPEI-PEG-GE11). The aim of the current study in the same HCC model was to evaluate the potential of biodegradable nanoparticle vectors based on pseudodendritic oligoamines (G2-HD-OEI) for systemic sodium iodide symporter (NIS) gene delivery and to compare efficiency and tumor specificity with LPEI-PEG-GE11. Transfection of HCC cells with NIS cDNA, using G2-HD-OEI, resulted in a 44-fold increase in iodide uptake in vitro as compared with a 22-fold increase using LPEI-PEG-GE11. After intravenous application of G2-HD-OEI/NIS HCC tumors accumulated 6-11% ID/g (123)I (percentage of the injected dose per gram tumor tissue) with an effective half-life of 10 hr (tumor-absorbed dose, 281 mGy/MBq) as measured by (123)I scintigraphic gamma camera or single-photon emission computed tomography computed tomography (SPECT CT) imaging, as compared with 6.5-9% ID/g with an effective half-life of only 6 hr (tumor-absorbed dose, 47 mGy/MBq) for LPEI-PEG-GE11. After only two cycles of G2-HD-OEI/NIS/(131)I application, a significant delay in tumor growth was observed with markedly improved survival. A similar degree of therapeutic efficacy had been observed after four cycles of LPEI-PEG-GE11/(131)I. These results clearly demonstrate that biodegradable nanoparticles based on OEI-grafted oligoamines show increased efficiency for systemic NIS gene transfer in an HCC model with similar tumor selectivity as compared with LPEI-PEG-GE11, and therefore represent a promising strategy for NIS-mediated radioiodine therapy of HCC.

Recent advances in oncolytic virus design

The cytolytic properties of viruses can be used to treat cancer. Replication of certain viruses is favoured in cancer cells, whereas others can be modified to obtain tumour specificity. This approach has evolved to become a new discipline called virotherapy. In addition, these replication-competent (oncolytic) viruses can be adapted as vectors for cancer gene therapy. The "armed" viruses show a double mechanism of action: direct destruction of cancer cells as a consequence of the lytic viral cycle, in combination with the effect of the therapeutic gene incorporated in the viral genome. Current trends in the field include strategies to increase the oncolytic potency of existing viruses; the evaluation of new candidates; the search for synergistic effects between different viruses and conventional therapies; and a rational approach to take advantage of the interplay between the viruses and the host immune system. This review summarises the most relevant achievements in recent years.

Sodium iodide symporter (NIS)-mediated radionuclide ((131)I, (188)Re) therapy of liver cancer after transcriptionally targeted intratumoral in vivo NIS gene delivery

We reported the therapeutic efficacy of (131)I in hepatocellular carcinoma (HCC) cells stably expressing the sodium iodide symporter (NIS) under the control of the tumor-specific α-fetoprotein (AFP) promoter. In the current study we investigated the efficacy of adenovirus-mediated in vivo NIS gene transfer followed by (131)I and (188)Re administration for the treatment of HCC xenografts. We used a replication-deficient adenovirus carrying the human NIS gene linked to the mouse AFP promoter (Ad5-AFP-NIS) for in vitro and in vivo NIS gene transfer. Functional NIS expression was confirmed by in vivo γ-camera imaging, followed by analysis of NIS protein and mRNA expression. Human HCC (HepG2) cells infected with Ad5-AFP-NIS concentrated 50% of the applied activity of (125)I, which was sufficiently high for a therapeutic effect in an in vitro clonogenic assay. Four days after intratumoral injection of Ad5-AFP-NIS (3×10(9) plaque-forming units) HepG2 xenografts accumulated 14.5% injected dose (ID)/g (123)I with an effective half-life of 13 hr (tumor-absorbed dose, 318 mGy/MBq (131)I). In comparison, 9.2% ID/g (188)Re was accumulated in tumors with an effective half-life of 12.8 hr (tumor-absorbed dose, 545 mGy/MBq). After adenovirus-mediated NIS gene transfer in HepG2 xenografts administration of a therapeutic dose of (131)I or (188)Re (55.5 MBq) resulted in a significant delay in tumor growth and improved survival without a significant difference between (188)Re and (131)I. In conclusion, a therapeutic effect of (131)I and (188)Re was demonstrated in HepG2 xenografts after tumor-specific adenovirus-mediated in vivo NIS gene transfer.

Image-guided, tumor stroma-targeted 131I therapy of hepatocellular cancer after systemic mesenchymal stem cell-mediated NIS gene delivery

Due to its dual role as reporter and therapy gene, the sodium iodide symporter (NIS) allows noninvasive imaging of functional NIS expression by (123)I-scintigraphy or (124)I-PET imaging before the application of a therapeutic dose of (131)I. NIS expression provides a novel mechanism for the evaluation of mesenchymal stem cells (MSCs) as gene delivery vehicles for tumor therapy. In the current study, we stably transfected bone marrow-derived CD34(-) MSCs with NIS cDNA (NIS-MSC), which revealed high levels of functional NIS protein expression. In mixed populations of NIS-MSCs and hepatocellular cancer (HCC) cells, clonogenic assays showed a 55% reduction of HCC cell survival after (131)I application. We then investigated body distribution of NIS-MSCs by (123)I-scintigraphy and (124)I-PET imaging following intravenous (i.v.) injection of NIS-MSCs in a HCC xenograft mouse model demonstrating active MSC recruitment into the tumor stroma which was confirmed by immunohistochemistry and ex vivo γ-counter analysis. Three cycles of systemic MSC-mediated NIS gene delivery followed by (131)I application resulted in a significant delay in tumor growth. Our results demonstrate tumor-specific accumulation and therapeutic efficacy of radioiodine after MSC-mediated NIS gene delivery in HCC tumors, opening the prospect of NIS-mediated radionuclide therapy of metastatic cancer using MSCs as gene delivery vehicles.

Epidermal growth factor receptor-targeted (131)I-therapy of liver cancer following systemic delivery of the sodium iodide symporter gene

We recently demonstrated tumor-selective iodide uptake and therapeutic efficacy of radioiodine in neuroblastoma tumors after systemic nonviral polyplex-mediated sodium iodide symporter (NIS) gene delivery. In the present study, we used novel polyplexes based on linear polyethylenimine (LPEI), polyethylene glycol (PEG), and the synthetic peptide GE11 as an epidermal growth factor receptor (EGFR)-specific ligand to target a NIS-expressing plasmid to hepatocellular carcinoma (HCC) (HuH7). Incubation of HuH7 cells with LPEI-PEG-GE11/NIS polyplexes resulted in a 22-fold increase in iodide uptake, which was confirmed in other cancer cell lines correlating well with EGFR expression levels. Using (123)I-scintigraphy and ex vivo γ-counting, HuH7 xenografts accumulated 6.5-9% injected dose per gram (ID/g) (123)I, resulting in a tumor-absorbed dose of 47 mGray/Megabecquerel (mGy/MBq) (131)Iodide ((131)I) after intravenous (i.v.) application of LPEI-PEG-GE11/NIS. No iodide uptake was observed in other tissues. After pretreatment with the EGFR-specific antibody cetuximab, tumoral iodide uptake was markedly reduced confirming the specificity of EGFR-targeted polyplexes. After three or four cycles of polyplex/(131)I application, a significant delay in tumor growth was observed associated with prolonged survival. These results demonstrate that systemic NIS gene transfer using polyplexes coupled with an EGFR-targeting ligand is capable of inducing tumor-specific iodide uptake, which represents a promising innovative strategy for systemic NIS gene therapy in metastatic cancers.

Review article: gene therapy, recent developments and future prospects in gastrointestinal oncology

BACKGROUND

Gene therapy consists of the introduction of genetic material into cells for a therapeutic purpose. A wide range of gene therapy vectors have been developed and used for applications in gastrointestinal oncology.

AIM

To review recent developments and published clinical trials concerning the application of gene therapy in the treatment of liver, colon and pancreatic cancers.

METHODS

Search of the literature published in English using the PubMed database.

RESULTS

A large variety of therapeutic genes are under investigation, such as tumour suppressor, suicide, antiangiogenesis, inflammatory cytokine and micro-RNA genes. Recent progress concerns new vectors, such as oncolytic viruses, and the synergy between viral gene therapy, chemotherapy and radiation therapy. As evidence of these basic developments, recently published phase I and II clinical trials, using both single agents and combination strategies, in adjuvant or advanced disease settings, have shown encouraging results and good safety records.

CONCLUSIONS

Cancer gene therapy is not yet indicated in clinical practice. However, basic and clinical advances have been reported and gene therapy is a promising, new therapeutic approach for the treatment of gastrointestinal tumours.

The biology of the sodium iodide symporter and its potential for targeted gene delivery

The sodium iodide symporter (NIS) is responsible for thyroidal, salivary, gastric, intestinal and mammary iodide uptake. It was first cloned from the rat in 1996 and shortly thereafter from human and mouse tissue. In the intervening years, we have learned a great deal about the biology of NIS. Detailed knowledge of its genomic structure, transcriptional and post-transcriptional regulation and pharmacological modulation has underpinned the selection of NIS as an exciting approach for targeted gene delivery. A number of in vitro and in vivo studies have demonstrated the potential of using NIS gene therapy as a means of delivering highly conformal radiation doses selectively to tumours. This strategy is particularly attractive because it can be used with both diagnostic (99mTc, 125I, 124I)) and therapeutic (131I, 186Re, 188Re, 211At) radioisotopes and it lends itself to incorporation with standard treatment modalities, such as radiotherapy or chemoradiotherapy. In this article, we review the biology of NIS and discuss its development for gene therapy.