Dual-specificity kinase DYRK3 phosphorylates p62 at the Thr-269 residue and promotes melanoma progression.

Melanoma is a type of skin cancer that originates in melanin-producing melanocytes. It is considered a multifactorial disease caused by both genetic and environmental factors, such as UV radiation. Dual-specificity tyrosine-phosphorylation-regulated kinase (DYRK) phosphorylates many substrates involved in signaling pathways, cell survival, cell cycle control, differentiation, and neuronal development. However, little is known about the cellular function of DYRK3, one of the five members of the DYRK family. Interestingly, it was observed that the expression of DYRK3, as well as p62 (a multifunctional signaling protein), is highly enhanced in most melanoma cell lines. This study aimed to investigate whether DYRK3 interacts with p62, and how this affects melanoma progression, particularly in melanoma cell lines. We found that DYRK3 directly phosphorylates p62 at the Ser-207 and Thr-269 residue. Phosphorylation at Thr-269 of p62 by DYRK3 increased the interaction of p62 with tumor necrosis factor receptor-associated factor 6 (TRAF6), an already known activator of mammalian target of rapamycin complex 1 (mTORC1) in the mTOR-involved signaling pathways. Moreover, the phosphorylation of p62 at Thr-269 promoted the activation of mTORC1. We also found that DYRK3-mediated phosphorylation of p62 at Thr-269 enhanced the growth of melanoma cell lines and melanoma progression. Conversely, DYRK3 knockdown or blockade of p62-T269 phosphorylation inhibited melanoma growth, colony formation, and cell migration. In conclusion, we demonstrated that DYRK3 phosphorylates p62, positively modulating the p62-TRAF6-mTORC1 pathway in melanoma cells. This finding suggests that DYRK3 suppression may be a novel therapy for preventing melanoma progression by regulating the mTORC1 pathway.

CRISPR-mediated ablation of TP53 and EGFR mutations enhances gefitinib sensitivity and anti-tumor efficacy in lung cancer.

Multiple pathogenic single-nucleotide polymorphisms (SNPs) have been identified as contributing factors in the aggravation of cancer prognosis and emergence of drug resistance in various cancers. Here, we targeted mutated EGFR and TP53 oncogenes harboring single-nucleotide missense mutations (EGFR-T790M and TP53-R273H) that are associated with gefitinib resistance. Co-delivery of adenine base editor (ABE) and EGFR- and TP53-SNP specific single-guide RNA via adenovirus (Ad) resulted in precise correction of the oncogenic mutations with high accuracy and efficiency in vitro and in vivo. Importantly, compared with a control group treated only with gefitinib, an EGFR inhibitor, co-treatment with Ad/ABE targeting SNPs in TP53 and EGFR in combination with gefitinib increased drug sensitivity and suppressed abnormal tumor growth more efficiently. Taken together, these results indicate that ABE-mediated correction of dual oncogenic SNPs can be an effective strategy for the treatment of drug-resistant cancers.

ErbB3-Targeting Oncolytic Adenovirus Causes Potent Tumor Suppression by Induction of Apoptosis in Cancer Cells.

Cancer is a multifactorial and deadly disease. Despite major advancements in cancer therapy in the last two decades, cancer incidence is on the rise and disease prognosis still remains poor. Furthermore, molecular mechanisms of cancer invasiveness, metastasis, and drug resistance remain largely elusive. Targeted cancer therapy involving the silencing of specific cancer-enriched proteins by small interfering RNA (siRNA) offers a powerful tool. However, its application in clinic is limited by the short half-life of siRNA and warrants the development of efficient and stable siRNA delivery systems. Oncolytic adenovirus-mediated therapy offers an attractive alternative to the chemical drugs that often suffer from innate and acquired drug resistance. In continuation to our reports on the development of oncolytic adenovirus-mediated delivery of shRNA, we report here the replication-incompetent (dAd/shErbB3) and replication-competent (oAd/shErbB3) oncolytic adenovirus systems that caused efficient and persistent targeting of ErbB3. We demonstrate that the E1A coded by oAd/shErbB, in contrast to dAd/shErbB, caused downregulation of ErbB2 and ErbB3, yielding stronger downregulation of the ErbB3-oncogenic signaling axis in in vitro models of lung and breast cancer. These results were validated by in vivo antitumor efficacy of dAd/shErbB3 and oAd/shErbB3.

CRISPR-Cas12a with an oAd Induces Precise and Cancer-Specific Genomic Reprogramming of EGFR and Efficient Tumor Regression.

CRISPR-Cas12a represents a class 2/type V CRISPR RNA-guided endonuclease, holding promise as a precise genome-editing tool in vitro and in vivo. For efficient delivery of the CRISPR-Cas system into cancer, oncolytic adenovirus (oAd) has been recognized as a promising alternative vehicle to conventional cancer therapy, owing to its cancer specificity; however, to our knowledge, it has not been used for genome editing. In this study, we show that CRISPR-Cas12a mediated by oAd disrupts the oncogenic signaling pathway with excellent cancer specificity. The intratumoral delivery of a single oAd co-expressing a Cas12a and a CRISPR RNA (crRNA) targeting the epidermal growth factor receptor (EGFR) gene (oAd/Cas12a/crEGFR) induces efficient and precise editing of the targeted EGFR gene in a cancer-specific manner, without detectable off-target nuclease activity. Importantly, oAd/Cas12a/crEGFR elicits a potent antitumor effect via robust induction of apoptosis and inhibition of tumor cell proliferation, ultimately leading to complete tumor regression in a subset of treated mice. Collectively, in this study we show precise genomic reprogramming via a single oAd vector-mediated CRISPR-Cas system and the feasibility of such system as an alternative cancer therapy.

Selective disruption of an oncogenic mutant allele by CRISPR/Cas9 induces efficient tumor regression.

Approximately 15% of non-small cell lung cancer cases are associated with a mutation in the epidermal growth factor receptor (EGFR) gene, which plays a critical role in tumor progression. With the goal of treating mutated EGFR-mediated lung cancer, we demonstrate the use of clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR associated protein 9 (Cas9) system to discriminate between the oncogenic mutant and wild-type EGFR alleles and eliminate the carcinogenic mutant EGFR allele with high accuracy. We targeted an EGFR oncogene harboring a single-nucleotide missense mutation (CTG > CGG) that generates a protospacer-adjacent motif sequence recognized by the CRISPR/Cas9 derived from Streptococcus pyogenes. Co-delivery of Cas9 and an EGFR mutation-specific single-guide RNA via adenovirus resulted in precise disruption at the oncogenic mutation site with high specificity. Furthermore, this CRISPR/Cas9-mediated mutant allele disruption led to significantly enhanced cancer cell killing and reduced tumor size in a xenograft mouse model of human lung cancer. Taken together, these results indicate that targeting an oncogenic mutation using CRISPR/Cas9 offers a powerful surgical strategy to disrupt oncogenic mutations to treat cancers; similar strategies could be used to treat other mutation-associated diseases.

Potent antitumor effect of tumor microenvironment-targeted oncolytic adenovirus against desmoplastic pancreatic cancer.

Pancreatic cancer is a leading cause of cancer-related death. Desmoplastic pancreatic tumors exhibit excessive extracellular matrix (ECM) and are thus highly resistant to anticancer therapeutics, since the ECM restricts drug penetration and dispersion. Here, we designed and generated two hypoxia-responsive and cancer-specific hybrid promoters, H(mT)E and H(E)mT. Transgene expression driven by each hybrid promoter was markedly higher under hypoxic conditions than normoxic conditions. Moreover, H(E)mT-driven transgene expression was highly cancer-specific and was superior to that of H(mT)E-driven expression. A decorin-expressing oncolytic adenovirus (Ad; oH(E)mT-DCN) replicating under the control of the H(E)mT promoter induced more potent and highly cancer-specific cell death compared with its cognate control oncolytic Ad, which harbored the endogenous Ad E1A promoter. Moreover, oH(E)mT-DCN exhibited enhanced antitumor efficacy compared with both the clinically approved oncolytic Ad ONYX-015 and its cognate control oncolytic Ad lacking DCN. oH(E)mT-DCN treatment also attenuated the expression of major ECM components, such as collagen I/III, elastin and fibronectin and induced tumor cell apoptosis, leading to extensive viral dispersion within orthotopic pancreatic tumors and pancreatic cancer patient-derived tumor spheroids. Collectively, these findings demonstrate that oH(E)mT-DCN exhibits potent antitumor efficacy by degrading the ECM and inducing apoptosis in a multifunctional process. This process facilitates the dispersion and replication of oncolytic Ad, making it an attractive candidate for the treatment of aggressive and desmoplastic pancreatic cancer.

Identification and functional characterization of nuclear mortalin in human carcinogenesis.

The Hsp70 family protein mortalin is an essential chaperone that is frequently enriched in cancer cells and exists in various subcellular sites, including the mitochondrion, plasma membrane, endoplasmic reticulum, and cytosol. Although the molecular mechanisms underlying its multiple subcellular localizations are not yet clear, their functional significance has been revealed by several studies. In this study, we examined the nuclear fractions of human cells and found that the malignantly transformed cells have more mortalin than the normal cells. We then generated a mortalin mutant that lacked a mitochondrial targeting signal peptide. It was largely localized in the nucleus, and, hence, is called nuclear mortalin (mot-N). Functional characterization of mot-N revealed that it efficiently protects cancer cells against endogenous and exogenous oxidative stress. Furthermore, compared with the full-length mortalin overexpressing cancer cells, mot-N derivatives showed increased malignant properties, including higher proliferation rate, colony forming efficacy, motility, and tumor forming capacity both in in vitro and in vivo assays. We demonstrate that mot-N promotes carcinogenesis and cancer cell metastasis by inactivation of tumor suppressor protein p53 functions and by interaction and functional activation of telomerase and heterogeneous ribonucleoprotein K (hnRNP-K) proteins.

Tumor microenvironment-modulating oncolytic adenovirus combined with GSK-3ß inhibitor enhances antitumor immune response against bladder cancer.

Bladder cancer is a common type of cancer around the world, and the majority of patients are diagnosed with non-muscle-invasive bladder cancer (NMIBC). Although low-risk NMIBC has a good prognosis, the disease recurrence rate and development of treatment-refractory disease remain high in intermediate- to high-risk NMIBC patients. To address these challenges for the treatment of NMIBC, a novel combination therapy composed of an oncolytic adenovirus (oAd) co-expressing interleukin (IL)-12, granulocyte-macrophage colony-stimulating factor (GM-CSF), and relaxin (RLX; HY-oAd) and a clinical-stage glycogen synthase kinase (GSK)-3ß inhibitor (9-ING-41; elraglusib) was investigated in the present report. Our findings demonstrate that HY-oAd and 9-ING-41 combination therapy (HY-oAd+9-ING-41) exerted superior inhibition of tumor growth compared with respective monotherapy in a syngeneic NMIBC tumor model. HY-oAd+9-ING-41 induced high-level tumor extracellular matrix (ECM) degradation and a more potent antitumor immune response than the respective monotherapy. In detail, HY-oAd+9-ING-41 induced superior accumulation of intratumoral T cells, prevention of immune cell exhaustion, and induction of tumor-specific adaptive immune response compared to either monotherapy. Collectively, these results demonstrate that the combination of HY-oAd and 9-ING-41 may be a promising approach to elicit a potent antitumor immune response against bladder cancer.

Synergistic antitumor immune response mediated by paclitaxel-conjugated nanohybrid oncolytic adenovirus with dendritic cell therapy.

Dendritic cell (DC)-based vaccines have emerged as a promising strategy in cancer immunotherapy due to low toxicity. However, the therapeutic efficacy of DC as a monotherapy is insufficient due to highly immunosuppressive tumor environment. To address these limitations of DC as immunotherapeutic agent, we have developed a polymeric nanocomplex incorporating (1) oncolytic adenovirus (oAd) co-expressing interleukin (IL)-12 and granulocyte-macrophage colony-stimulating factor (GM-CSF) and (2) arginine-grafted bioreducible polymer with PEGylated paclitaxel (APP) to restore antitumor immune surveillance function in tumor milieu and potentiate immunostimulatory attributes of DC vaccine. Nanohybrid complex (oAd/APP) in combination with DC (oAd/APP+DC) induced superior expression level of antitumor cytokines (IL-12, GM-CSF, and interferon gamma) than either oAd/APP or DC monotherapy in tumor tissues, thus resulting in superior intratumoral infiltration of both endogenous and exogenous DCs. Furthermore, oAd/APP+DC treatment led superior migration of DC to secondary lymphoid organs, such as draining lymph nodes and spleen, in comparison with either monotherapy. Superior migration profile of DCs in oAd/APP+DC treatment group resulted in more prolific activation of tumor-specific T cells in these lymphoid organs and greater intratumoral infiltration of T cells. Additionally, oAd/APP+DC treatment led to lower subset of tumor infiltrating lymphocytes and splenocytes being immunosuppressive regulatory T cells than any other treatment groups. Collectively, oAd/APP+DC led to superior induction of antitumor immune response and amelioration of immunosuppressive tumor microenvironment to elicit potent tumor growth inhibition than either monotherapy.

MicroRNA-296 is enriched in cancer cells and downregulates p21WAF1 mRNA expression via interaction with its 3' untranslated region.

MicroRNAs (miRNAs) are a class of noncoding small RNAs that act as negative regulators of gene expression. To identify miRNAs that may regulate human cell immortalization and carcinogenesis, we performed comparative miRNA array profiling of human normal and SV40-T antigen immortalized cells. We found that miR-296 was upregulated in immortalized cells that also had activation of telomerase. By an independent experiment on genomic analysis of cancer cells we found that chromosome region (20q13.32), where miR-296 is located, was amplified in 28/36 cell lines, and most of these showed enriched miR-296 expression. Overexpression of miR-296 in human cancer cells, with and without telomerase activity, had no effect on their telomerase function. Instead, it suppressed p53 function that is frequently downregulated during human cell immortalization and carcinogenesis. By monitoring the activity of a luciferase reporter connected to p53 and p21(WAF1) (p21) untranslated regions (UTRs), we demonstrate that miR-296 interacts with the p21-3'UTR, and the Hu binding site of p21-3'UTR was identified as a potential miR-296 target site. We demonstrate for the first time that miR-296 is frequently upregulated during immortalization of human cells and contributes to carcinogenesis by downregulation of p53-p21(WAF1) pathway.

Oncolytic adenovirus as pancreatic cancer-targeted therapy: Where do we go from here?

Pancreatic cancer remains one of the deadliest cancers with extremely high mortality rate, and the number of cases is expected to steadily increase with time. Pancreatic cancer is refractory to conventional cancer treatment options, like chemotherapy and radiotherapy, and commercialized immunotherapeutics, owing to its immunosuppressive and desmoplastic phenotype. Due to these reasons, development of an innovative treatment option that can overcome these challenges posed by the pancreatic tumor microenvironment (TME) is in an urgent need. The present review aims to summarize the evolution of oncolytic adenovirus (oAd) engineering and usage as therapeutics (either monotherapy or combination therapy) over the last decade to overcome these hurdles to instigate a potent antitumor effect against desmoplastic and immunosuppressive pancreatic cancer.

Current clinical landscape of oncolytic viruses as novel cancer immunotherapeutic and recent preclinical advancements.

Oncolytic viruses (OVs) have been gaining attention in the pharmaceutical industry as a novel immunotherapeutic and therapeutic adjuvant due to their ability to induce and boost antitumor immunity through multiple mechanisms. First, intrinsic mechanisms of OVs that enable exploitation of the host immune system (e.g., evading immune detection) can nullify the immune escape mechanism of tumors. Second, many types of OVs have been shown to cause direct lysis of tumor cells, resulting in an induction of tumor-specific T cell response mediated by release of tumor-associated antigens and danger signal molecules. Third, armed OV-expressing immune stimulatory therapeutic genes could be highly expressed in tumor tissues to further improve antitumor immunity. Last, these OVs can inflame cold tumors and their microenvironment to be more immunologically favorable for other immunotherapeutics. Due to these unique characteristics, OVs have been tested as an adjuvant of choice in a variety of therapeutics. In light of these promising attributes of OVs in the immune-oncology field, the present review will examine OVs in clinical development and discuss various strategies that are being explored in preclinical stages for the next generation of OVs that are optimized for immunotherapy applications.

Challenges and progress toward tumor-targeted therapy by systemic delivery of polymer-complexed oncolytic adenoviruses.

Oncolytic adenovirus (oAd) elicits antitumor activity by preferential viral replication in cancer cells. However, poor systemic administrability or suboptimal intratumoral retainment of the virus remains a major challenge toward maximizing the antitumor activity of oAd in a clinical environment. To surmount these issues, a variety of non-immunogenic polymers has been used to modify the surface of oAds chemically or physically. Complexation of oAd with polymers can effectively evade the host immune response and reduces nonspecific liver sequestration. The tumor-specific delivery of these complexes can be further improved upon by inclusion of tumor-targeting moieties on the surface. Therefore, modification of the Ad surface using polymers is viewed as a potential strategy to enhance the delivery of Ad via systemic administration. This review aims to provide a comprehensive overview of polymer-complexed Ads, their progress, and future challenges in cancer treatment.

Why is Mortalin a Potential Therapeutic Target for Cancer?

Cancer is one of the leading causes of death worldwide, accounting for nearly 10 million deaths in 2020. Therefore, cancer therapy is a priority research field to explore the biology of the disease and identify novel targets for the development of better treatment strategies. Mortalin is a member of the heat shock 70 kDa protein family. It is enriched in several types of cancer and contributes to carcinogenesis in various ways, including inactivation of the tumor suppressor p53, deregulation of apoptosis, induction of epithelial-mesenchymal transition, and enhancement of cancer stemness. It has been studied extensively as a therapeutic target for cancer treatment, and several types of anti-mortalin molecules have been discovered that effectively suppress the tumor cell growth. In this review, we 1) provide a comprehensive sketch of the role of mortalin in tumor biology; 2) discuss various anti-mortalin molecules, including natural compounds, synthetic small molecules, peptides, antibodies, and nucleic acids, that have shown potential for cancer treatment in laboratory studies; and 3) provide future perspectives in cancer treatment.

Immunotherapy by mesenchymal stromal cell delivery of oncolytic viruses for treating metastatic tumors.

Oncolytic viruses (OVs) have emerged as a very promising anti-cancer therapeutic strategy in the past decades. However, despite their pre-clinical promise, many OV clinical evaluations for cancer therapy have highlighted the continued need for their improved delivery and targeting. Mesenchymal stromal cells (MSCs) have emerged as excellent candidate vehicles for the delivery of OVs due to their tumor-homing properties and low immunogenicity. MSCs can enhance OV delivery by protecting viruses from rapid clearance following administration and also by more efficiently targeting tumor sites, consequently augmenting the therapeutic potential of OVs. MSCs can function as "biological factories," enabling OV amplification within these cells to promote tumor lysis following MSC-OV arrival at the tumor site. MSC-OVs can promote enhanced safety profiles and therapeutic effects relative to OVs alone. In this review we explore the general characteristics of MSCs as delivery tools for cancer therapeutic agents. Furthermore, we discuss the potential of OVs as immune therapeutics and highlight some of the promising applications stemming from combining MSCs to achieve enhanced delivery and anti-tumor effectiveness of OVs at different pre-clinical and clinical stages. We further provide potential pitfalls of the MSC-OV platform and the strategies under development for enhancing the efficacy of these emerging therapeutics.

A pH- and Bioreducible Cationic Copolymer with Amino Acids and Piperazines for Adenovirus Delivery.

Adenoviruses (Ads) are attractive nonviral vectors and show great potential in cancer gene therapy. However, inherent properties of Ads, including immunogenicity, nonspecific toxicity, and coxsackie and adenovirus receptor (CAR)-dependent cell uptake, limit their clinical use. To surmount these issues, we developed a pH- and glutathione-responsive poly(ethylene glycol)-poly(ꞵ-aminoester)-polyethyleneimine (PPA) for conjugation with Ad. The pH sensitivity of the PPA copolymer was elegantly tuned by substitution with different amino acids (arginine, histidine, and tryptophan), piperazines (Pip1, Pip2, and Pip3), and guanidine residues in the backbone of the PPA conjugate. PPA copolymer was further functionalized with short-chain cross-linker succinimidyl 3-(2-pyridyldithio)propionate) (SPDP) to obtain PPA-SPDP for facile conjugation with Ad. The PPA-conjugated Ad (PPA-Ad) conjugate was obtained by reacting PPA-SPDP conjugate with thiolated Ad (Ad-SH). Ad-SH was prepared by reacting Ad with 2-iminothiolane. The size distribution and zeta potential results of PPA-Ad conjugate showed an increasing trend with an increase in copolymer dose. From in vitro test, it was found that the transduction efficiency of PPA-Ad conjugate in CAR-positive cells (A549 and H460 cells) was remarkably increased at the acidic pH condition (pH 6.2) when compared with PPA-Ad conjugate incubated under the physiological condition (pH 7.4). Interestingly, the increase in transduction efficiency was evidenced in CAR-negative cells (MDA-MB-231 and T24 cells). These results demonstrated that biocompatible and biodegradable PPA copolymers can efficiently cover the surface of Ad and can increase the transduction efficiency, and hence PPA copolymers can be a useful nanomaterial for viral vector delivery in cancer therapy.

Bioreducible polymer-mediated delivery of oncolytic adenovirus can attenuate antiviral immune response and concurrently enhance the induction of antitumor immune response to effectively prevent metastasis.

Oncolytic virotherapy is a highly promising and novel treatment modality for cancer. Several clinical trials with oncolytic viruses have illustrated that the potent antitumor efficacy of these viruses may rely on the efficient induction of antitumor immune response. In contrast, antiviral immune response is attributed to adverse side defects and diminishing therapeutic efficacy. In the present report, we generated a nanohybrid complex incorporating immune stimulatory oncolytic adenovirus (oAd) co-expressing decorin (DCN) and interleukin (IL)-12 with a bioreducible nanomaterial composed of PEI-Arg-mPEG-S-S-mPEG-Arg-PEI blocks (PAPS), ultimately aiming to modulate both antitumor and antiviral immune responses to be favorable toward oncolytic virotherapy. The transduction efficacy of the PAPS-incorporated nanohybrid vector (Ad/PAPS) was significantly higher than that of a complex using our previously reported polymer PPSA (Ad/PPSA) regardless of the cellular coxsackievirus and adenovirus receptor expression level of cancer cells. oAd complexed with PAPS (oAd/PAPS) also elicited a more potent cancer cell killing effect, antitumor efficacy, and metastasis inhibition than naked oAd or oAd complexed with PPSA (oAd/PPSA) through a higher level of therapeutic transgenes (DCN and IL-12), viral replication, and more efficient infiltration of T cells into tumor tissues. Notably, oAd/PAPS induced the highest level of antitumor immune response while the antiviral immune response was mediated at a significantly lower level than those of naked oAd. Adaptive immune response against the virus was also significantly attenuated in the oAd/PAPS group. oAd/PAPS treatment also led to the highest level of antitumor central memory T cells and the lowest level of immunosuppressive regulatory T cells in the spleen. Collectively, our findings illustrate that oAd/PAPS can simultaneously regulate both antitumor and antiviral immune responses to be more favorable to oncolytic virotherapy, leading to improved gene expression, viral replication, and growth inhibition of both primary and metastatic tumors.

Polymeric Systems for Cancer Immunotherapy: A Review.

Immunotherapy holds enormous promise to create a new outlook of cancer therapy by eliminating tumors via activation of the immune system. In immunotherapy, polymeric systems play a significant role in improving antitumor efficacy and safety profile. Polymeric systems possess many favorable properties, including magnificent biocompatibility and biodegradability, structural and component diversity, easy and controllable fabrication, and high loading capacity for immune-related substances. These properties allow polymeric systems to perform multiple functions in immunotherapy, such as immune stimulants, modifying and activating T cells, delivery system for immune cargos, or as an artificial antigen-presenting cell. Among diverse immunotherapies, immune checkpoint inhibitors, chimeric antigen receptor (CAR) T cell, and oncolytic virus recently have been dramatically investigated for their remarkable success in clinical trials. In this report, we review the monotherapy status of immune checkpoint inhibitors, CAR-T cell, and oncolytic virus, and their current combination strategies with diverse polymeric systems.

RGD peptide-modified adenovirus expressing hepatocyte growth factor and X-linked inhibitor of apoptosis improves islet transplantation.

BACKGROUND: Islet transplantation has the potential for treating type I diabetes; however, its widespread clinical application is limited by the massive apoptotic cell death and poor revascularization of transplanted islet grafts. METHODS: We constructed a surface-modified adenoviral vector with RGD (Arg-Gly-Asp) sequences encoding human X-linked inhibitor of apoptosis and hepatocyte growth factor (RGD-Adv-hHGF-hXIAP). In vitro transgene expression in human islets was determined by enzyme-liniked immunosorbent assay. RGD-Adv-hHGF-hXIAP-transduced human islets were transplanted under the kidney capsule of streptozotocin-induced diabetic NOD/SCID mice. The blood glucose levels of mice were measured weekly. The kidneys bearing islets were isolated at the end of the experiment and subjected to immunofluorescence staining. RESULTS: The transduction efficiency on human islets was significantly improved using RGD-modified adenovirus. HGF and XIAP gene expressions were dose-dependent after viral transduction. When exposed to a cocktail of inflammatory cytokines, RGD-Adv-hHGF-hXIAP-transduced human islets showed decreased caspase 3 activity and reduced apoptotic cell death. Prolonged normoglycemic control could be achieved by transplanting RGD-Adv-hHGF-hXIAP-transduced human islets. Immunofluorescence staining of kidney sections bearing RGD-Adv-hHGF-hXIAP-transduced islets was positive for insulin and von Willebrand factor (vWF) at 200 days after transplantation. CONCLUSIONS: These results indicated that ex vivo transduction of islets with RGD-Adv-hHGF-hXIAP decreased apoptotic islet cell death and improved islet revascularization, and eventually might improve the outcome of human islet transplantation.