Targeting gene-virotherapy of cancer and its prosperity

Mechanism of action and treatment of type I interferon in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) caused by HBV, HCV infection, and other factors is one of the most common malignancies in the world. Although, percutaneous treatments such as surgery, ethanol injection, radiofrequency ablation, and transcatheter treatments such as arterial chemoembolization are useful for local tumor control, they are not sufficient to improve the prognosis of patients with HCC. External interferon agents that induce interferon-related genes or type I interferon in combination with other drugs can reduce the recurrence rate and improve survival in HCC patients after surgery. Therefore, in this review, we focus on recent advances in the mechanism of action of type I interferons, emerging therapies, and potential therapeutic strategies for the treatment of HCC using IFNs.

The role of oncolytic virotherapy and viral oncogenes in the cancer stem cells: a review of virus in cancer stem cells

Cancer Stem Cells (CSCs) are the main "seeds" for the initiation, growth, metastasis, and recurrence of tumors. According to many studies, several viral infections, including the human papillomaviruses, hepatitis B virus, Epstein-Barr virus, and hepatitis C virus, promote the aggressiveness of cancer by encouraging the development of CSC features. Therefore, a better method for the targeted elimination of CSCs and knowledge of their regulatory mechanisms in human carcinogenesis may lead to the development of a future tool for the management and treatment of cancer. Oncolytic viruses (OVs), which include the herpes virus, adenovirus, vaccinia, and reovirus, are also a new class of cancer therapeutics that have favorable properties such as selective replication in tumor cells, delivery of numerous eukaryotic transgene payloads, induction of immunogenic cell death and promotion of antitumor immunity, as well as a tolerable safety profile that essentially differs from that of other cancer therapeutics. The effects of viral infection on the development of CSCs and the suppression of CSCs by OV therapy were examined in this paper. The purpose of this review is to investigate the dual role of viruses in CSCs (oncolytic virotherapy and viral oncogenes).

Infectious Recombinant Senecavirus A Expressing p16INK4A Protein

Senecavirus A (SVA) is an oncolytic RNA virus, and it is the ideal oncolytic virus that can be genetically engineered for editing. However, there has not been much exploration into creating SVA viruses that carry antitumor genes to increase their oncolytic potential. The construction of SVA viruses carrying antitumor genes that enhance oncolytic potential has not been fully explored. In this study, a recombinant SVA-CH-01-2015 virus (p15A-SVA-clone) expressing the human p16^INK4A protein, also known as cell cycle-dependent protein kinase inhibitor 2A (CDKN2A), was successfully rescued and characterized. The recombinant virus, called SVA-p16, exhibited similar viral replication kinetics to the parent virus, was genetically stable, and demonstrated enhanced antitumor effects in Ishikawa cells. Additionally, another recombinant SVA virus carrying a reporter gene (iLOV), SVA-iLOV, was constructed and identified using the same construction method as an auxiliary validation. Collectively, this study successfully created a new recombinant virus, SVA-p16, that showed increased antitumor effects and could serve as a model for further exploring the antitumor potential of SVA as an oncolytic virus.

Combination of oncolytic adenovirus targeting SATB1 and docetaxel for the treatment of castration-resistant prostate cancer

Background: Oncolytic viral therapy is a new strategy for tumor eradication which combines the advantages of viral therapy and gene therapy. Silencing SATB1 exhibits strong inhibitory effect on the growth of prostate cancer. Docetaxel (DTX) is the gold standard for chemotherapy of prostate cancer, but its side effects decrease the life quality of patients. Therefore, it is urgent to develop combination therapy to increase its anti-tumor effect.

Methods: Oncolytic adenovirus targeting SATB1 was constructed and named ZD55-SATB1. Human prostatic cancer cells DU145 and PC-3 and human prostatic stromal cells WPMY-1 were treated with ZD55-SATB1 or/and DTX. In vitro cell proliferation, migration, invasion, apoptosis were detected. In addition, PC-3 cells were injected subcutaneously into nude mice, which were treated with ZD55-SATB1 or/and DTX. Tumor growth was monitored in vivo.

Results: ZD55-SATB1 combined with DTX inhibited proliferation, migration and invasion of DU145 and PC-3 cells, while promoted apoptosis of DU145 and PC-3 cells more efficiently than monotherapy. ZD55-SATB1 had no cytotoxicity on WPMY-1 cells. In animal models, the combined treatment of ZD55-SATB1+DTX and endocrine therapy effectively inhibited the growth of xenograft tumor, accompanied by increased expression of caspase-3 and caspase-8, and decrease expression of Bcl-2 and angiogenesis marker CD31 compared to other treatment groups.

Conclusion: The combination of oncolytic adenovirus ZD55-SATB1 and chemotherapy provides a novel approach to effective therapy of prostate cancer.

A Triple-Regulated Oncolytic Adenovirus Carrying MicroRNA-143 Exhibits Potent Antitumor Efficacy in Colorectal Cancer

The cancer-targeting gene virotherapy might be a useful strategy for the treatment of cancer, because it could combine the advantages of both gene therapy and virotherapy. This study aimed to construct a triple-regulated oncolytic adenovirus, Ad-RGD-Survivin-ZD55-miR-143, carrying the therapeutic gene miR-143 and evaluate its possible antitumor effect in colorectal cancer. We observed that miR-143 was lowly expressed in patients with colorectal cancer. The upregulation of miR-143 could inhibit cell proliferation and induce cell apoptosis by targeting KRAS in colorectal cancer cells. Then, Ad-RGD-Survivin-ZD55-miR-143 was successfully constructed in this study. Cells infected with Ad-RGD-Survivin-ZD55-miR-143 could inhibit cell proliferation, suppress cell migration and invasion, arrest cells at the G1 phase, and induce cellular apoptosis. At the same time, Ad-RGD-Survivin-ZD55-miR-143 decreased the expression of PARP-1 and KRAS protein in vitro. In a HCT116 xenograft model, intratumoral injection of Ad-RGD-Survivin-ZD55-miR-143 resulted in reduced tumor growth. Furthermore, Ad-RGD-Survivin-ZD55-miR-143 induced apoptosis and decreased the expression level of KRAS in HCT116 xenograft cells. Our results suggested that Ad-RGD-Survivin-ZD55-miR-143 produced a strong antitumor effect by targeting KRAS and that this strategy could broaden the therapeutic options for treating colorectal cancer.

Fighting Cancer with Viruses: Oncolytic Virus Therapy in China

As part of oncolytic virotherapy to treat cancer, oncolytic viruses (OVs) can selectively infect tumor cells to promote oncolysis of cancer cells, local immunological reactions, and systemic antitumor immunity with minimal toxicity to normal tissues. The immunostimulatory properties of OVs provide enormous benefits for the treatment of cancer. A variety of OVs, including genetically engineered and natural viruses, have shown promise in preclinical models and clinical studies. In 2005, the China Food and Drug Administration approved its first OV drug, Oncorine (H101), for treatment of advanced head and neck cancer. To explore new treatment strategies, >200 recombinant or natural OVs are undergoing in-depth investigation in China, and >250 oncolytic virotherapy-related reports from the OV community in China have been published in the past 5 years. These studies investigated a variety of exogenous genes and combination therapeutic strategies to enhance the treatment effects of OVs. To date, five clinical trials covering four OV agents (Oncorine, OrienX010, KH901, and H103) are ongoing, and additional OV agents are awaiting approval for clinical trials in China. Overall, this research emphasizes that combination therapy, especially tumor immunotherapy coupled with effective system administration strategies, can promote the development of oncolytic virotherapies. This article focuses on studies that were carried out in China in order to give an overview of the past, present, and future of oncolytic virotherapy in China.

Anti-colorectal cancer effects of anti-p21Ras scFv delivered by the recombinant adenovirus KGHV500 and cytokine-induced killer cells

BACKGROUND

Colorectal cancer (CRC) is the most common type of gastrointestinal cancer. CRC gene therapy mediated by adenovirus holds great promise for the treatment of malignancies. However, intravenous delivery of adenovirus exhibits limited anti-tumor activity in vivo when used alone.

METHODS

In this study, the antitumor activity of the recombinant adenovirus KGHV500 was assessed with the MTT, TUNEL, Matrigel invasion and cell migration assays. To enhance the intravenous delivery of KGHV500 in vivo, cytokine-induced killer (CIK) cells were used as a second vector to carry KGHV500. We explored whether CIK cells could carry the recombinant adenovirus KGHV500 containing the anti-p21Ras single chain fragment variable antibody (scFv) gene into tumors and enhance antitumor potency.

RESULTS

Our results showed that KGHV500 exhibited significant antitumor activity in vitro. In the nude mouse SW480 tumor xenograft model, the combination of CIK cells with KGHV500 could induce higher antitumor activity against colorectal cancer in vivo than that induced by either CIK or KGHV500 alone. After seven days of treatment, adenovirus and scFv were detected in tumor tissue but were not detected in normal tissues by immunohistochemistry. Therefore, KGHV500 replicates in tumors and successfully expresses anti-p21Ras scFv in a colorectal cancer xenograft model.

CONCLUSIONS

Our study provides a novel strategy for the treatment of colorectal cancer by combining CIK cells with the recombinant adenovirus KGHV500 which carried anti-p21 Ras scFv.

A conditionally replicating adenovirus expressing IL-24 acts synergistically with temozolomide to enhance apoptosis in melanoma cells in vitro

Malignant melanoma is characterized by suppressed apoptosis in tumor cells and high levels of invasion. Temozolomide (TMZ) is one of the most effective single chemotherapeutic agents for patients with malignant melanoma, but resistance develops quickly and frequently. Therapeutic cytokines such as interleukin-24 (IL-24) and conditionally replicating adenoviruses have exhibited promising results as complementary therapies. Thus, the present study hypothesized that a conditionally replicating adenovirus expressing IL-24 combined with TMZ may exhibit increased antitumor activity compared with either treatment alone in melanoma A375 and M14 cell lines in vitro. The present study constructed an E1B-55 gene-deleted conditionally replicating adenovirus expressing the IL-24 gene (ZD55-IL-24). IL-24 was expressed at high levels in melanoma cells infected with ZD55-IL-24 in the presence of TMZ. The combination of ZD55-IL-24 + TMZ induced higher protein expression levels of the proapoptotic proteins B-cell lymphoma-2 (Bcl-2)-like protein 4 and phosphorylated protein, γ-H2A histone family member X (γ-H2AX), and reduced the levels of the antiapoptotic proteins Bcl-2, myeloid cell leukemia-1and nuclear factor-κB compared with either treatment individually. A dose-dependent increase in the cytopathic effects for the combination of ZD55-IL-24 and TMZ was also observed. The data of the present study suggest that the ZD55-IL-24 + TMZ combination induced increased levels of apoptosis, possibly by triggering DNA damage, in melanoma cells in vitro compared with either treatment alone. These findings suggest that this strategy may be a promising approach for the treatment of patients with malignant melanoma.

Marine Lectins DlFBL and HddSBL Fused with Soluble Coxsackie-Adenovirus Receptor Facilitate Adenovirus Infection in Cancer Cells BUT Have Different Effects on Cell Survival

Cancer development and progression are usually associated with glycosylation change, providing prognostic and diagnostic biomarkers, as well as therapeutic targets, for various cancers. In this work, Dicentrarchus labrax fucose binding lectin (DlFBL) and Haliotis discus discus sialic acid binding lectin (HddSBL) were genetically fused with soluble coxsackie-adenovirus receptor (sCAR), and produced through a bacterial expression system. Results showed that recombinant sCAR-DlFBL not only facilitated adenovirus Ad-EGFP infection in K562/ADR and U87MG cells, but also enhanced the cytotoxicity of adenovirus harboring gene encoding Pinellia pedatisecta agglutinin (PPA) or DlFBL (Ad-PPA or Ad-DlFBL) on U87MG cells through inducing apoptosis. Recombinant sCAR-HddSBL facilitated Ad-EGFP infection, but dramatically counteracted the cytotoxicity of both Ad-PPA and Ad-DlFBL in U87MG cells. Further analysis revealed that sCAR-HddSBL, but not sCAR-DlFBL, significantly upregulated transcription factor E2F1 levels in U87MG cells, which might be responsible for the adverse effect of sCAR-HddSBL on Ad-PPA and Ad-DlFBL. Taken together, our data suggested that sCAR-DlFBL could be further developed to redirect therapeutic adenoviruses to infect cancer cells such as U87MG, and the sCAR-lectin fusion proteins for adenoviral retargeting should be carefully examined for possible survival signaling induced by lectins, such as HddSBL.

Regenerative effect of hOPG gene-modified autologous PDLs in combination with cell transplantation on periodontal defection in beagle dogs

This study evaluated the ability of human osteoprotegerin gene-modified autologous periodontal ligament cells (PDLCs) in combination with cell transplantation to promote periodontal regeneration in beagle dogs. Adenovirus Ad5-hOPG-EGFP-transfected PDLCs and BME-10X collagen membranes were fabricated and used for periodontal repair. Buccal periodontal defects (mesiodistal width × depth: 5 × 5 mm) were created on the second, third, and fourth mandibular premolars in six normal beagle dogs, and the defects were histologically and histomorphometrically assessed for periodontal regeneration in the following four groups: (1) hOPG-PDLCs + BME-10X, (2) mock-PDLCs + BME-10X, (3) PDLCs + BME-10X, and (4) BME-10X. The radiographic and histological results suggested that hOPG-PDLCs significantly promoted periodontal defect repair. This study demonstrates the potential of hOPG-modified PDLCs for periodontal tissue regeneration.

CD47-retargeted oncolytic adenovirus armed with melanoma differentiation-associated gene-7/interleukin-24 suppresses in vivo leukemia cell growth

Our previous studies have suggested that harboring a soluble coxsackie-adenovirus receptor-ligand (sCAR-ligand) fusion protein expression cassette in the viral genome may provide a universal method to redirect oncolytic adenoviruses to various membrane receptors on cancer cells resisting to serotype 5 adenovirus infection. We report here a novel oncolytic adenovirus vector redirected to CD47+ leukemia cells though carrying a sCAR-4N1 expression cassette in the viral genome, forming Ad.4N1, in which 4N1 represents the C-terminal CD47-binding domain of thrombospondin-1. The infection and cytotoxicity of Ad.4N1 in leukemia cells were determined to be mediated by the 4N1-CD47 interaction. Ad.4N1 was further engineered to harbor a gene encoding melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24), forming Ad.4N1-IL24, which replicated dramatically faster than Ad.4N1, and elicited significantly enhanced antileukemia effect in vitro and in a HL60/Luc xenograft mouse model. Our data suggest that Ad.4N1 could act as a novel oncolytic adenovirus vector for CD47+ leukemia targeting gene transfer, and Ad.4N1 harboring anticancer genes may provide novel antileukemia agents.

Enhanced antitumor effect of combining TRAIL and MnSOD mediated by CEA-controlled oncolytic adenovirus in lung cancer

Lung cancer, especially adenocarcinoma, is one of the leading causes of death in the world. Carcinoembryonic antigen (CEA), a superb non-small-cell lung cancer marker candidate, showed a beneficial effect in cancer therapy with oncolytic adenovirus in recent studies. Cancer-targeting dual gene-virotherapy delivers two therapeutic genes, linked by a connexon, in the replication-deficient vector instead of one gene so that they can work in common. In this study, we constructed a tumor-specific oncolytic adenovirus, CD55-TRAIL-IETD-MnSOD. The virus has the fusion protein complementary DNAs for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and for manganese superoxide dismutase (MnSOD) complementary DNA linked through a 4-amino acid caspase-8 cleavage site (IETD), and uses a CEA promoter to control virus E1A express. This is the first work to use a CEA promoter-regulated oncolytic adenovirus carrying two therapeutic genes for cancer research. Its targeting and anticancer capacity was evaluated by in vitro and in vivo experiments. The results indicated that CD55-TRAIL-IETD-MnSOD caused more cell apoptosis than CD55-TRAIL or CD55-MnSOD alone, or their combination in vitro, with low cytotoxicity of normal cells. In the A549 tumor xenograft model in nude mice, data showed that CD55-TRAIL-IETD-MnSOD could effectively suppress tumor growth than single gene groups, with no histological damage in liver, spleen or kidney tissues. Thus, the CEA-regulated dual-gene oncolytic virus CD55-TRAIL-IETD-MnSOD may be a novel potential therapy for lung cancer.

Targeting gene-virus-mediated manganese superoxide dismutase effectively suppresses tumor growth in hepatocellular carcinoma in vitro and in vivo

Although the treatment methods for hepatocellular carcinoma (HCC) have made a great progress on patient survival rate and life quality, the HCC recurrence still is very high. To explore the novel effective anticancer strategies for HCC, the Cancer Targeting Gene-Viro-Therapy (CTGVT) strategy was applied through oncolytic virus-delivery antitumor gene. In this article, the dual-regulated oncolytic adenovirus Ad-AFP-E1A-E1B(Δ55kDa)-Mn-SOD (briefly named AD55-Mn-SOD) was constructed using a liver cancer-specific α-fetoprotein (AFP) promoter to control replication-essential E1A gene and deliver the novel tumor suppression gene Manganese superoxide dismutase (Mn-SOD). The results indicated that the constructed AD55-Mn-SOD exerted tumor-specific features, and induced dramatic cytotoxicity in HCC cells in vitro and suppress the HCC xenografted growth in nude mice. Moreover, the anticancer mechanism of AD55-Mn-SOD is due to the activation of caspase apoptotic pathway. These data suggested that AD55-Mn-SOD could become a potential anticancer agent for liver cancer.

Oncolytic virus carrying shRNA targeting SATB1 inhibits prostate cancer growth and metastasis

Recent studies suggest that SATB1 is a promising therapeutic target for prostate cancer. To develop novel SATB1-based therapeutic agents for prostate cancer, in this study, we aimed to construct ZD55-SATB1, an oncolytic adenovirus ZD55 carrying shRNA targeting SATB1, and investigate its effects on the inhibition of prostate cancer growth and metastasis. ZD55-SATB1 was constructed and used to infect human prostate cancer cell lines DU145 and LNCaP. The inhibitory effect of ZD55-SATB1 on SATB1 expression was evaluated by reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. The cytotoxicity of ZD55-SATB1 was detected by MTT assay. Cell invasion was detected by Matrigel invasion assay. The in vivo antitumor activities of ZD55-SATB1 were evaluated in xenograft mouse model. We found that ZD55-SATB1 selectively replicated and significantly reduced SATB1 expression in DU145 and LNCaP cells. ZD55-SATB1 effectively inhibited the viability and invasion of DU145 and LNCaP cells in vitro and inhibited prostate cancer growth and metastasis in xenograft nude mice. In conclusion, replicative oncolytic adenovirus armed with SATB1 shRNA exhibits effective antitumor effect in human prostate cancer. Our study provides the basis for the development of ZD55-SATB1 for the treatment of prostate cancer.

Gene therapy targeting hepatocellular carcinoma by a dual-regulated oncolytic adenovirus harboring the focal adhesion kinase shRNA

Cancer targeting gene-viro-therapy (CTGVT) approach has become a hotspot and a trend in the field of cancer biotherapy and oncolytic adenovirus is an ideal vector to carry the targeting genes. In this study, we used human telomerase reverse transcriptase (hTERT) promoter to control the adenovirus early region 1a (E1A) and the human α-fetoprotein (AFP) promoter integrated with hypoxia response element (HRE) to control the adenovirus early region 1b (E1B). Then the novel double-regulated adenovirus Ad-hTERT-HREAF (named SG505) was engineered. The short-hairpin RNA against focal adhesion kinase (FAK) was inserted into SG505 and thus forming Ad-hTERT-HREAF-shRNA (called SG505‑siFAK). Then various oncolytic adenoviruses were examined to verify whether they could suppress liver cancer cells selectively and efficiently both in vitro and in vivo. Both replicative and replication-defective adenoviruses carrying FAK-shRNA significantly inhibited the expression of FAK in Hep3B and SMMC-7721 cell lines and efficiently suppressed the growth of liver cancer cell lines with minor effect to normal cells. Furthermore, the recombined oncolytic adenoviruses, SG505-siFAK, SG505-EGFP and SG505 were able to selectively propagate in AFP-positive liver cancer cells in vitro and the SG505-siFAK efficiently suppressed the expression of FAK. SG505-siFAK showed the most potent tumor inhibition capability among the three recombined adenovirus with IC50 levels of 0.092±0.009 and 0.424±0.414 pfu/cell in the Hep3B and HepG2 cell line, respectively. Animal experiment further confirmed that SG505-siFAK achieved the most significant tumor inhibition of Hep3B liver cancer xenografted growth by intratumoral injection comparing to the intravenous injection among the three recombined viruses. Immunohistochemical results indicated that FAK expression was downregulated significantly in the tumors treated with SG505-siFAK. The dual-regulated oncolytic adenovirus SG505-siFAK was proven to inhibit the growth of liver cancer cells selectively and efficiently, therefore SG505-siFAK could be a potential agent for future clinical trials of hepatocellular carcinoma.

RGD-modifided oncolytic adenovirus exhibited potent cytotoxic effect on CAR-negative bladder cancer-initiating cells

Cancer-initiating cell (CIC) is critical in cancer development, maintenance and recurrence. The reverse expression pattern of coxsackie and adenovirus receptor (CAR) and α_ν integrin in bladder cancer decreases the infection efficiency of adenovirus. We constructed Arg-Gly-Asp (RGD)-modified oncolytic adenovirus, carrying EGFP or TNF-related apoptosis-inducing ligand (TRAIL) gene (Onco^Ad.RGD-hTERT-EGFP/TRAIL), and applied them to CAR-negative bladder cancer T24 cells and cancer-initiating T24 sphere cells. Onco^Ad.RGD-hTERT-EGFP had enhanced infection ability and cytotoxic effect on T24 cells and T24 sphere cells, but little cytoxicity on normal urothelial SV-HUC-1 cells compared with the unmodified virus Onco^Ad.hTERT-EGFP. Notably, Onco^Ad.RGD-hTERT-TRAIL induced apoptosis in T24 cells and T24 sphere cells. Furthermore, it completely inhibited xenograft initiation established by the oncolytic adenovirus-pretreated T24 sphere cells, and significantly suppressed tumor growth by intratumoral injection. These results provided a promising therapeutic strategy for CAR-negative bladder cancer through targeting CICs.

Oncolytic adenovirus-mediated short hairpin RNA targeting MYCN gene induces apoptosis by upregulating RKIP in neuroblastoma

The amplification of MYCN is a typical characteristic of aggressive neuroblastomas, whereas acquired mutations of p53 lead to refractory and relapsed cases. We had previously examined the applicability of the replication-competent oncolytic adenovirus, ZD55-shMYCN, to deliver a short hairpin RNA targeting MYCN gene for p53-null and MYCN-amplified neuroblastoma cell line LA1-55N. Our data have shown that ZD55-shMYCN has an additive tumor growth inhibitory response through shRNA-mediated MYCN knockdown and ZD55-mediated cancer cell lysis. In this regard, ZD55-shMYCN can downregulate MYCN and perform anticancer effects, thereby acquiring significance in the administration of MYCN-amplified and p53-null neuroblastomas. Hence, we further investigated the anticancer properties of ZD55-shMYCN in neuroblastomas. Our data showed that ZD55-shMYCN induced G2/M arrest via decreasing the levels of cyclin D1 and cyclin B1 irrespective of p53 status. ZD55-shMYCN effectively induced apoptosis in neuroblastomas through activation of caspase-3 and enhancing PARP cleavage. Furthermore, ZD55-shMYCN could downregulate phosphoinositide 3-kinase and pAkt and upregulate RKIP levels. Similarly, pro-apoptosis was revealed by the histopathologic examination of paraffin-embedded section of resected tumors of mice xenograft. In vitro and in vivo studies, we elucidate the apoptosis properties and mechanisms of action of ZD55-shMYCN, which provide a promising approach for further clinical development.

Targeting cancer stem cells with oncolytic virus

Cancer stem cells (CSCs) represent a distinct subpopulation of cancer cells which are shown to be relatively resistant to conventional anticancer therapies and have been correlated to disease recurrence. Oncolytic viruses utilize methods of cell killing that differ from traditional therapies and thus are able to elude the typical mechanisms that CSCs use to resist current chemotherapies and radiotherapies. Moreover, genetically engineered oncolytic viruses may further augment the oncolytic effects. Here we review the recent data regarding the ability of several oncolytic viruses to eradicate CSCs.

Enhanced antitumor efficacy of a novel oncolytic adenovirus combined with temozolomide in the treatment of melanoma in vivo

PURPOSE

The aim of this study was to investigate the effect of Ki67-ZD55-IL-24 with temozolomide (TMZ) against melanoma in mice.

METHODS

Seventy-eight mice with subcutaneous injection of A375 cells (2 × 10(6)) into the right flank were randomized to receive phosphate buffered saline (PBS), Ki67-ZD55, Ki67-ZD55-IL-24, TMZ, TMZ + Ki67-ZD55, and TMZ + Ki67-ZD55-IL-24. Six mice were killed in each group 10 days after intervention for detecting IL-24 mRNA and protein expression. The remaining mice were monitored to draw the body weight change curve and tumor growth curve, and killed 30 days after intervention. Tumors were excised and weighted. The morphology of tumor tissues was determined by hematoxylin and eosin (HE) staining, and the apoptosis index and rate of apoptotic cells were determined by TUNEL assay and AnnexinV-FITC/PI double staining, respectively.

RESULTS

The Ki67-ZD55-IL-24-treated group generated much more reactive oxygen species than the untreated group. There was no significant difference in IL-24 expression between Ki67-ZD55-IL-24 and TMZ + Ki67-ZD55-IL-24 groups. Immunohistochemical analysis and Western blot revealed that both the Ki67-ZD55 and Ki67-ZD55-IL-24 could significantly reduce the expression of MGMT. Toxicity assessments demonstrated that mice in the three groups that received TMZ exhibited significant body weight loss following treatment. HE staining showed that TMZ + Ki67-ZD55-IL-24 group had much fewer karyokinesis in the tumors, compared with other groups. The apoptosis index of tumor tissues and the rate of apoptotic cells were significantly higher in TMZ + Ki67-ZD55-IL-24 group than in other groups (all P < 0.05).

CONCLUSIONS

These findings indicate this novel strategy holds promising potentials for treatment of malignant melanoma.

Potent anti-tumour activity of a novel conditionally replicating adenovirus for melanoma via inhibition of migration and invasion

Background:

Conditionally replicating adenoviruses (CRAds) represent a novel class of oncological therapeutic agents. One strategy to ensure tumour targeting is to place the essential viral genes under the control of tumour-specific promoters. Ki67 has been selected as a cancer gene therapy target, as it is expressed in most malignant cells but is barely detectable in most normal cells. This study aimed to investigate the effects of a Ki67 promoter-controlled CRAd (Ki67-ZD55-IL-24) on the proliferation and apoptosis of melanoma cells.

Methods:

Melanoma cells were independently treated with Ki67-ZD55-IL-24, ZD55-IL-24, Ki67-ZD55, and ZD55-EGFP. The cytotoxic potential of each treatment was assessed using cell viability measurements. Cell migration and invasion were assayed using cell migration and invasion assays. Apoptosis was assayed using the annexin V-FITC assay, western blotting, reverse transcriptase PCR (RT–PCR), haematoxylin and eosin (H&E) staining, and the TUNEL assay.

Results:

Our results showed that Ki67-ZD55-IL-24 had significantly enhanced anti-tumour activity as it more effectively induced apoptosis in melanoma cells than the other agents. Ki67-ZD55-IL-24 also caused the most significant inhibition of cell migration and invasion of melanoma cells. Furthermore, apoptosis was induced more effectively in melanoma xenografts in nude mice.

Conclusions:

This strategy holds promising potential for the further development of an effective approach to treat malignant melanoma.

CD123 targeting oncolytic adenoviruses suppress acute myeloid leukemia cell proliferation in vitro and in vivo

We report here a novel strategy to redirect oncolytic adenoviruses to CD123 by carry a soluble coxsackie-adenovirus receptor (sCAR)-IL3 expression cassette in the viral genome to form Ad.IL3, which sustainably infected acute myeloid leukemia (AML) cells through CD123. Ad.IL3 was further engineered to harbor gene encoding manganese superoxide dismutase (MnSOD) or mannose-binding plant lectin Pinellia pedatisecta agglutinin (PPA), forming Ad.IL3-MnSOD and Ad.IL3-PPA. As compared with Ad.IL3 or Ad.sp-E1A control, Ad.IL3-MnSOD and Ad.IL3-PPA significantly suppressed in vitro proliferation of HL60 and KG-1 cells. Elevated apoptosis was detected in HL60 and KG-1 cells treated with either Ad.IL3-MnSOD or Ad.IL3-PPA. The caspase-9–caspase-7 pathway was determined to be activated by Ad.IL3-MnSOD as well as by Ad.IL3-PPA in HL60 cells. In an HL60/Luc xenograft nonobese diabetic/severe-combined immunodeficiency mice model, Ad.IL3-MnSOD and Ad.IL3-PPA suppressed cancer cell growth as compared with Ad.IL3. A significant difference of cancer cell burden was detected between Ad.IL3 and Ad.IL3-PPA groups at day 9 after treatment. Furthermore, Ad.IL3-MnSOD significantly prolonged mouse survival as compared with Ad.sp-E1A. These findings demonstrated that Ad.IL3-gene could serve as a novel agent for AML therapy. Harboring sCAR-ligand expression cassette in the viral genome may provide a universal method to redirect oncolytic adenoviruses to various membrane receptors on cancer cells resisting serotype 5 adenovirus infection.

An oncolytic adenovirus enhances antiangiogenic and antitumoral effects of a replication-deficient adenovirus encoding endostatin by rescuing its selective replication in nasopharyngeal carcinoma cells

A replication-deficient adenovirus (Ad) encoding secreted human endostatin (Ad-Endo) has been demonstrated to have promising antiangiogenic and antitumoral effects. The E1B55k-deleted Ad H101 can selectively lyse cancer cells. In this study, we explored the antitumor effects and cross-interactions of Ad-Endo and H101 on nasopharyngeal carcinoma (NPC). The results showed that H101 dramatically promoted endostatin expression by Ad-Endo via rescuing Ad-Endo replication in NPC cells, and the expressed endostatin proteins significantly inhibited the proliferation of human umbilical vein endothelial cells. E1A and E1B19k products are required for the rescuing of H101 to Ad-Endo replication in CNE-1 and CNE-2 cells, but not in C666-1 cells. On the other hand, Ad-Endo enhanced the cytotoxicity of H101 by enhancing Ad replication in NPC cells. The combination of H101 and Ad-Endo significantly inhibited CNE-2 xenografts growth through the increased endostatin expression and Ad replication. These findings indicate that the combination of Ad-Endo gene therapy and oncolytic Ad therapeutics could be promising in comprehensive treatment of NPC.

Antitumor efficacy of a recombinant adenovirus encoding endostatin combined with an E1B55KD-deficient adenovirus in gastric cancer cells

Background

Gene therapy using a recombinant adenovirus (Ad) encoding secretory human endostatin (Ad-Endo) has been demonstrated to be a promising antiangiogenesis and antitumor strategy of in animal models and clinical trials. The E1B55KD-deficient Ad dl1520 was also found to replicate selectively in and destroy cancer cells. In this study, we aimed to investigate the antitumor effects of antiangiogenic agent Ad-Endo combined with the oncolytic Ad dl1520 on gastric cancer (GC) in vitro and in vivo and determine the mechanisms of these effects.

Methods

The Ad DNA copy number was determined by real-time PCR, and gene expression was assessed by ELISA, Western blotting or immunohistochemistry. The anti-proliferation effect (cytotoxicity) of Ad was assessed using the colorimetry-based MTT cell viability assay. The antitumor effects were evaluated in BALB/c nude mice carrying SGC-7901 GC xenografts. The microvessel density and Ad replication in tumor tissue were evaluated by checking the expression of CD34 and hexon proteins, respectively.

Results

dl1520 replicated selectively in GC cells harboring an abnormal p53 pathway, including p53 mutation and the loss of p14^ARF expression, but did not in normal epithelial cells. In cultured GC cells, dl1520 rescued Ad-Endo replication, and dramatically promoted endostatin expression by Ad-Endo in a dose- and time-dependent manner. In turn, the addition of Ad-Endo enhanced the inhibitory effect of dl1520 on the proliferation of GC cells. The transgenic expression of Ad5 E1A and E1B19K simulated the rescue effect of dl1520 supporting Ad-Endo replication in GC cells. In the nude mouse xenograft model, the combined treatment with dl1520 and Ad-Endo significantly inhibited tumor angiogenesis and the growth of GC xenografts through the increased endostatin expression and oncolytic effects.

Conclusions

Ad-Endo combined with dl1520 has more antitumor efficacy against GC than Ad-Endo or dl1520 alone. These findings indicate that the combination of Ad-mediated antiangiogenic gene therapy and oncolytic Ad therapeutics could be one of promising comprehensive treatment strategies for GC.

Tumor suppressor in lung cancer-1 (TSLC1) mediated by dual-regulated oncolytic adenovirus exerts specific antitumor actions in a mouse model

AIM

The tumor suppressor in lung cancer-1 (TSLC1) is a candidate tumor suppressor of lung cancer, and frequently inactivated in primary non-small cell lung cancer (NSCLC). In this study, we investigated the effects of TSLC1 mediated by a dual-regulated oncolytic adenovirus on lung cancer, and the mechanisms underlying the antitumor actions.

METHODS

The recombinant virus Ad·sp-E1A(Δ24)-TSLC1 was constructed by inserting the TSLC1 gene into the dual-regulated Ad·sp-E1A(Δ24) vector, which contained the survivin promoter and a 24 bp deletion within E1A. The antitumor effects of Ad·sp-E1A(Δ24)-TSLC1 were evaluated in NCI-H460, A549, and H1299 lung cancer cell lines and the normal fibroblast cell line MRC-5, as well as in A549 xenograft model in nude mice. Cell viability was assessed using MTT assay. The expression of TSLC1 and activation of the caspase signaling pathway were detected by Western blot analyses. The tumor tissues from the xenograft models were examined using H&E staining, IHC, TUNEL, and TEM analyses.

RESULTS

Infection of A549 lung cancer cells with Ad·sp-E1A(Δ24)-TSLC1 induced high level expression of TSLC1. Furthermore, the Ad·sp-E1A(Δ24)-TSLC1 virus dose-dependently suppressed the viability of NCI-H460, A549, and H1299 lung cancer cells, and did not affect MRC-5 normal fibroblast cells. Infection of NCI-H460, A549, and H1299 lung cancer cells with Ad·sp-E1A(Δ24)-TSLC1 induced apoptosis, and increased activation of caspase-8, caspase-3 and PARP. In A549 xenograft model in nude mice, intratumoral injection of Ad·sp-E1A(Δ24)-TSLC1 significantly suppressed the tumor volume, and increased the survival rate (from less than 15% to 87.5% at d 60). Histological studies showed that injection of Ad·sp-E1A(Δ24)-TSLC1 caused tumor cell apoptosis and virus particle propagation in tumor tissues.

CONCLUSION

The oncolytic adenovirus Ad·sp-E1A(Δ24)-TSLC1 exhibits specific antitumor effects, and is a promising agent for the treatment of lung cancer.

A dual-regulated oncolytic adenovirus expressing interleukin-24 sensitizes melanoma cells to temozolomide via the induction of apoptosis

Malignant melanoma is one of the most lethal and aggressive human malignancies. Suppressed apoptosis and extraordinary invasiveness are the distinctive features that contribute to malignant melanoma. The alkylating agent temozolomide (TMZ) is one of the most effective single chemotherapeutic agents for patients with malignant melanoma, but resistance develops quickly and with high frequency. We constructed a dual-regulated oncolytic adenovirus expressing interleukin 24 (IL-24) gene (Ki67-ZD55-IL-24) by utilizing the Ki67 promoter to replace the native viral promoter of E1A gene. We investigated whether a combination of Ki67-ZD55-IL-24-mediated gene virotherapy and chemotherapy using TMZ produces increased cytotoxicity against human melanoma cells via the induction of apoptosis. Our data indicate that this novel strategy thus holds promising potentials for further developing an effective approach to treat malignant melanoma.

Construction of a novel oncolytic adenoviral vector and its biological characteristics

In this study, we aimed to construct an effective and safe oncolytic adenoviral vector for cancer treatment with gene therapy. First, the promoter of the catalytic subunit of human telomerase (hTERTp), adenovirus early region 1a gene (E1A) and thymidine kinase gene of human herpes virus type 1 (HSV-1-TK) were amplified by using PCR from genomic DNA of 293A cells and wild-type HSV-1 (wHSV-1). These specially-prepared elements were inserted into an adenoviral shuttle vector in the opposite and the same directions of left inverted terminal repeat (L-ITR), respectively, to construct pENTR-E1A-IRES-TK-hTERTp (pEITH) and pENTR-hTERTp-E1A-IRES-TK (pHEIT). LR reaction between adenoviral shuttle vectors (pEITH and pHEIT) and the backbone vector DEST was carried out to establish adenoviral expression vectors pAd-E1A-IRES-TK-hTERTp (pAd-EITH) and pAd-hTERTp-E1A-IRES-TK (pAd-HEIT). Recombinant adenovirus Ad-EITH and Ad-HEIT were produced by transfecting 293A cells and purified for the subsequent studies of titer measurement, replication capability with and without acyclovir (ACV) and antitumor ability with and without ganciclovir (GCV) to evaluate the biological characteristics. Adenoviral shuttle vectors pEITH and pHEIT and expression vectors pAd-EITH and pAd-HEIT were successfully constructed, and recombinant adenoviruses Ad-EITH and Ad-HEIT with high titer were produced. The results of replication and cytotoxicity assays showed that Ad-EITH and Ad-HEIT replicated in the hTERTp (+) human nasopharyngeal carcinoma cell line CNE and expressed the TK gene effectively leading to the death of tumor cells. In addition, there were still some Ad-HEIT particles replicating in the hTERTp (-) human osteosarcoma U-2OS cells and human lung HFL-1 fibroblasts compared to Ad-EITH which was hardly able to replicate in U-2OS and HFL-1 cells. In addition, we also observed an interesting phenomenon, that the replication of Ad-EITH could be inhibited by antiviral drug ACV on account of the expression of HSV-1-TK gene making Ad-EITH sensitive to ACV. In conclusion, a novel oncolytic adenoviral vector Ad-EITH was produced which can be used for cancer-specific and efficient viral replication, and its safety is potentially improved as replication can be inhibited by ACV in vitro.

Treatment of pancreatic cancer using an oncolytic virus harboring the lipocalin-2 gene

BACKGROUND

The 5-year survival rate for patients with pancreatic cancer is <5%, and it is always resistant to the current chemoradiotherapy. Therefore, new, effective agents for the treatment of pancreatic cancer are urgently needed. The promising strategy of cancer-targeting gene virotherapy (CTGVT) has demonstrated great anticancer potential. The objective of the current study was to determine whether 1 CTGVT approach, oncolytic virus (OV)-harboring lipocalin-2, is capable of treating pancreatic cancer.

METHODS

Tissue microarrays were constructed to detect the expression of lipocalin-2 in 60 specimens of pancreatic adenocarcinoma. The clinical significance of lipocalin-2 was investigated in an analysis of correlations between lipocalin-2 expression and matched clinical characteristics. A lipocalin-2-expressing OV, ZD55-lipocalin-2, was constructed by deleting the adenoviral protein E1B55kD. The antitumor efficacy and mechanisms of the OV were investigated in pancreatic cancer cells with v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations in vitro and in vivo.

RESULTS

Lipocalin-2 expression was correlated with a good prognosis in patients with pancreatic adenocarcinoma. ZD55-lipocalin-2 dramatically inhibited the growth of pancreatic cancer in vitro and in vivo by inducing cytolysis and caspase-dependent apoptosis.

CONCLUSIONS

Higher lipocalin-2 expression predicted a better prognosis in patients with pancreatic cancer. The results indicated that ZD55-lipocalin-2, which specifically expressed higher levels of lipocalin-2 in tumor cells, may serve as a potent anticancer drug for pancreatic cancer therapy, especially for patients who have pancreatic adenocarcinoma with KRAS mutations.

Conditionally replicating adenoviruses carrying mda-7/IL-24 for cancer therapy

BACKGROUND

Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) suppresses growth and induces apoptosis in a broad range of human cancers without significant cytotoxicity to normal cells. Conditionally replicating adenoviruses (CRAds) not only have the ability to destroy cancer cells but may also be potential vectors for the expression of therapeutic genes.

METHODS

This review provides an overview of specifications for a novel anti-tumor approach CRAds carrying IL-24, and discusses recent progress in this field.

RESULTS

Studies in multiple laboratories report that CRAds carrying IL-24 selectively induced apoptosis in some cancer cells, and enhanced selective toxicity to cancer cells when combined with chemotherapeutic agents.

CONCLUSION

CRAds carrying IL-24 may prove a novel and effective approach for the treatment of cancers.

Targeting Gene-Viro-Therapy with AFP driving Apoptin gene shows potent antitumor effect in hepatocarcinoma

Background

Gene therapy and viral therapy are used for cancer therapy for many years, but the results are less than satisfactory. Our aim was to construct a new recombinant adenovirus which is more efficient to kill hepatocarcinoma cells but more safe to normal cells.

Methods

By using the Cancer Targeting Gene-Viro-Therapy strategy, Apoptin, a promising cancer therapeutic gene was inserted into the double-regulated oncolytic adenovirus AD55 in which E1A gene was driven by alpha fetoprotein promoter along with a 55 kDa deletion in E1B gene to form AD55-Apoptin. The anti-tumor effects and safety were examined by western blotting, virus yield assay, real time polymerase chain reaction, 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay, Hoechst33342 staining, Fluorescence-activated cell sorting, xenograft tumor model, Immunohistochemical assay, liver function analysis and Terminal deoxynucleotidyl transferase mediated dUTP Nick End Labeling assay.

Results

The recombinant virus AD55-Apoptin has more significant antitumor effect for hepatocelluar carcinoma cell lines (in vitro) than that of AD55 and even ONYX-015 but no or little impair on normal cell lines. Furthermore, it also shows an obvious in vivo antitumor effect on the Huh-7 liver carcinoma xenograft in nude mice with bigger beginning tumor volume till about 425 mm3 but has no any damage on the function of liver. The induction of apoptosis is involved in AD55-Apoptin induced antitumor effects.

Conclusion

The AD55-Apoptin can be a potential anti-hepatoma agent with remarkable antitumor efficacy as well as higher safety in cancer targeting gene-viro-therapy system.

Selective killing of lung cancer cells using carcinoembryonic antigen promoter and double suicide genes, thymidine kinase and cytosine deaminase (pCEA-TK/CD)

The application of gene therapy in cancer treatment is limited by non-specific targeting. In the present study, we constructed a recombinant plasmid, containing a carcinoembryonic antigen (CEA) promoter and double suicide genes thymidine kinase (TK) and cytosine deaminase (CD), henceforth referred to as pCEA-TK/CD. Our results showed that the CEA promoter can specifically drive target gene expression in CEA-positive lung cancer cells. In the presence of prodrugs 5-flucytosine and ganciclovir, pCEA-TK/CD transfection decreased inhibitory concentration 50 and increased apoptosis and cyclomorphosis. Our result suggests that gene therapy using pCEA-TK/CD may be a promising new approach for treating lung cancer.

Oncolytic bluetongue viruses: promise, progress, and perspectives

Humans are sero-negative toward bluetongue viruses (BTVs) since BTVs do not infect normal human cells. Infection and selective degradation of several human cancer cell lines but not normal ones by five US BTV serotypes have been investigated. We determined the susceptibilities of many normal and human cancer cells to BTV infections and made comparative kinetic analyses of their cytopathic effects, survival rates, ultra-structural changes, cellular apoptosis and necrosis, cell cycle arrest, cytokine profiles, viral genome, mRNAs, and progeny titers. The wild-type US BTVs, without any genetic modifications, could preferentially infect and degrade several types of human cancer cells but not normal cells. Their selective and preferential BTV-degradation of human cancer cells is viral dose–dependent, leading to effective viral replication, and induced apoptosis. Xenograft tumors in mice were substantially reduced by a single intratumoral BTV injection in initial in vivo experiments. Thus, wild-type BTVs, without genetic modifications, have oncolytic potentials. They represent an attractive, next generation of oncolytic viral approach for potential human cancer therapy combined with current anti-cancer agents and irradiation.

Combining conditionally replicating adenovirus-mediated gene therapy with chemotherapy: a novel antitumor approach

Despite significant improvements in diagnosis and innovations in the therapy of specific cancers, effective treatment of neoplastic diseases still presents major challenges. Recent studies have shown that conditionally replicating adenoviruses (CRAds) not only have the ability to destroy cancer cells but may also be potential vectors for the expression of therapeutic genes. Several studies in animal models have demonstrated that the combination of CRAds-mediated gene therapy and chemotherapy has greater therapeutic benefit than either treatment modality alone. In this review, an overview of specifications for a novel antitumor approach combining CRAd-gene therapy and chemotherapy is provided and recent progress in this field is discussed.

A novel approach to overcome temozolomide resistance in glioma and melanoma: Inactivation of MGMT by gene therapy

Malignant glioma is the most common primary brain tumor. Malignant melanoma is the most malignant of skin tumor. The two malignancies are poorly responsive to conventional treatment regimens such as chemotherapy. Temozolomide (TMZ) is a DNA-alkylating agent used for the treatment of glioma, astrocytoma, and melanoma. Resistance to alkylating agents such as TMZ correlates with increased expression of DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). Several studies in animal models have demonstrated that decreasing MGMT level with gene therapy could overcome TMZ resistance and enhance tumor cell death. In the present review, we provide an overview of recent advances in this field.

5/35 fiber-modified conditionally replicative adenovirus armed with p53 shows increased tumor-suppressing capacity to breast cancer cells

Conditionally replicative adenoviruses (CRAds) are widely used for cancer biotherapy and show a significant growth-suppressing effect on many types of cancer. However, it was reported that breast cancer was highly resistant to the infection of traditionally used adenovirus of serotype 5 (Ad5)-based CRAds. Although partial substitution of the fiber protein of replication-deficient Ad5 with that of adenovirus of serotype 35 (Ad35) facilitated infection of breast cancer cells by adenoviral vectors, it is still unknown whether this modification can improve CRAds in their tumor-eliminating capacity. We generated a 5/35 fiber-modified CRAd with a p53 cDNA construct and investigated whether this alteration in fiber region can make CRAds suppress the growth of breast cancer more effectively. Our data reinforced the proposal that 5/35-modified fiber conferred higher adenovirus infectivity for breast cancer cells than natural Ad5 fiber. Interestingly, 5/35 fiber-modified CRAd replicated more efficiently in breast cancer cells than Ad5-based CRAd. We also found 5/35 fiber-modified CRAd mediated higher expression of p53 in breast cancer cells. In vitro, 5/35 fiber-modified CRAd eliminated breast cancer cells more efficiently. Growth of xenograft tumors in nude mice was also significantly retarded by 5/35 fiber-modified CRAd. The 5/35 fiber-modified CRAd suppressed the growth of breast cancer cells more effectively than Ad5-based CRAd, both in vitro and in vivo. Thus CRAd with 5/35 hybrid fiber may be a promising vector for breast cancer treatment.

Targeting Gene-ViroTherapy for prostate cancer by DD3-driven oncolytic virus-harboring interleukin-24 gene

Prostate cancer (PCa) is the second leading cause of cancer-related deaths in Western male population. Previous studies have demonstrated that differential display code 3 (DD3 or DD3(PCA3)) is one of the most PCa-specific genes; therefore, it has been used as a clinical diagnostic marker for PCa. In this study, we constructed an oncolytic adenovirus Ad.DD3-E1A by using the minimal DD3 promoter to replace the native viral promoter of E1A gene. In addition, Ad.DD3-E1A was armed with therapeutic gene IL-24 to enhance its antitumor activity. The resulting adenovirus, Ad.DD3-E1A-IL-24, demonstrated PCa specificity and excellent antitumor effect. Further analyses on its antitumor mechanism revealed that it has the capacity to induce apoptosis in PCa cells and inhibit angiogenesis. These results suggest that Ad.DD3-E1A-IL-24 is a promising antitumor agent that may be able to be used in the future as a treatment for PCa.

Viral-based gene delivery and regulated gene expression for targeted cancer therapy

IMPORTANCE OF THE FIELD

Cancer is both a major health concern and a care-cost issue in the US and the rest of the world. It is estimated that there will be a total of 1,479,350 new cancer cases and 562,340 cancer deaths in 2009 within the US alone. One of the major obstacles in cancer therapy is the ability to target specifically cancer cells. Most existing chemotherapies and other routine therapies (such as radiation therapy and hormonal manipulation) use indiscriminate approaches in which both cancer cells and non-cancerous surrounding cells are treated equally by the toxic treatment. As a result, either the cancer cell escapes the toxic dosage necessary for cell death and consequently resumes replication, or an adequate lethal dose that kills the cancer cell also causes the cancer patient to perish. Owing to this dilemma, cancer- or organ/tissue-specific targeting is greatly desired for effective cancer treatment and the reduction of side effect cytotoxicity within the patient.

AREAS COVERED IN THIS REVIEW

In this review, the strategies of targeted cancer therapy are discussed, with an emphasis on viral-based gene delivery and regulated gene expression.

WHAT THE READER WILL GAIN

Numerous approaches and updates in this field are presented for several common cancer types.

TAKE HOME MESSAGE

A summary of existing challenges and future directions is also included.

Potent antitumor effect of interleukin-24 gene in the survivin promoter and retinoblastoma double-regulated oncolytic adenovirus

Interleukin (IL)-24 is an excellent therapeutic gene for cancer therapy. In this work, IL-24 was inserted into Ad.sp-E1A(Delta24), an oncolytic adenovirus with a 24-bp deletion in the E1A gene, which was driven by the survivin promoter to form Ad.sp-E1A(Delta24)-IL-24. Ad.sp-E1A(Delta24)-IL-24 has an excellent antitumor effect in vitro for human nasopharyngeal, liver, lung, and cervical carcinoma cell lines but does no or little damage to normal cell lines L-02 and WI38. Furthermore, it achieved nearly complete inhibition (although not elimination) of NCI-H460 lung carcinoma growth in nude mice. The antitumor efficacy of Ad.sp-E1A(Delta24)-IL-24 on NCI-H460 cells was clearly mediated by apoptosis, because it induced caspase-3 and poly(ADP-ribose) polymerase cleavage. This is the first report of Ad.sp-E1A(Delta24)-IL-24 with such an excellent, broad, and specific antitumor effect in vitro and nearly complete inhibition of lung tumor growth in vivo.

PTD4-apoptin protein therapy inhibits tumor growth in vivo

Apoptin protein harbors tumor-selective cell death activity, which makes it a potential anticancer therapy candidate. This study reports an apoptin therapy approach based on protein transduction domain 4 (PTD4)-mediated transduction of recombinant apoptin protein. In vitro, the PTD4-apoptin fusion protein is located in the nucleus and induces cell death in, e.g., human hepatocarcinoma HepG2 cells. In normal human L-02 hepatocytes, PTD4-apoptin protein retained mainly cytoplasmic and did not induce detectable levels of cell death, illustrating that the PTD4 domain does not affect apoptin's tumor-selective characteristics. In vivo, liver, cervix and gastric carcinoma xenografts treated with PTD4-apoptin protein for 6 days via the tumor epidermis exhibited a significant tumor growth inhibition because of apoptin-mediated cell death. In addition, treatment of human hepatocarcinoma xenografts during 3 weeks showed that PTD4-apoptin protein has significant anticancer activity, whereas control treatment with PTD4-enhanced green fluorescence protein or saline did not. Cell death and disruption of the tumor integrity were apparent in the PTD4-apoptin transduced xenografted tumors. As important, although PTD4-apoptin protein could be detected in the epidermal tissue covering the subcutaneous tumor tissue and in several organs, such as liver and brain, of the treated mice, no tissue disruption or signs of cell death could be detected. Our in vivo data reveal that apoptin protein delivery constitutes a novel powerful and safe anticancer therapy.

Significant antitumor activity of oncolytic adenovirus expressing human interferon-beta for hepatocellular carcinoma

BACKGROUND

Human interferon-beta (IFN-beta) has been widely used in gene therapy for its antitumor activity but its therapeutic effect is limited. The conditionally replicative adenovirus ONYX-015 (a E1B-55-kDa-deleted adenovirus) targets well to tumor cells, but is not potent enough to cause significant tumor regression. To solve these problems, a tumor-selective replicating adenovirus expressing IFN-beta was constructed in this study.

METHODS

The oncolytic adenoviruses were generated by homologous recombination in packaging cells. The expression of the IFN-beta protein was detected by enzyme-linked immunosorbent assay (ELISA). The antitumor efficacy of ZD55-IFN-beta was evaluated in cell lines and human hepatocellular carcinoma xenografts in nude mice.

RESULTS

ZD55-IFN-beta can express much more IFN-beta than Ad-IFN-beta because of the replication of the ZD55 vector. Our data showed that ZD55-IFN-beta could exert a strong cytopathic effect on tumor cells (about 100-fold higher than Ad-IFN-beta or ONYX-015). Moreover, no obvious cytotoxic or apoptotic effects were detected in normal cells infected with ZD55-IFN-beta.

CONCLUSIONS

The antitumor efficacy of IFN-beta could be significantly improved due to the increased gene expression level from the tumor-selective replicating vector. The oncolytic adenovirus expressing IFN-beta may provide a novel approach for cancer gene therapy.

Oncolytic virotherapy: molecular targets in tumor-selective replication and carrier cell-mediated delivery of oncolytic viruses

Tremendous advances have been made in developing oncolytic viruses (OVs) in the last few years. By taking advantage of current knowledge in cancer biology and virology, specific OVs have been genetically engineered to target specific molecules or signal transduction pathways in cancer cells in order to achieve efficient and selective replication. The viral infection and amplification eventually induce cancer cells into cell death pathways and elicit host antitumor immune responses to further help eliminate cancer cells. Specifically targeted molecules or signaling pathways (such as RB/E2F/p16, p53, IFN, PKR, EGFR, Ras, Wnt, anti-apoptosis or hypoxia) in cancer cells or tumor microenvironment have been studied and dissected with a variety of OVs such as adenovirus, herpes simplex virus, poxvirus, vesicular stomatitis virus, measles virus, Newcastle disease virus, influenza virus and reovirus, setting the molecular basis for further improvements in the near future. Another exciting new area of research has been the harnessing of naturally tumor-homing cells as carrier cells (or cellular vehicles) to deliver OVs to tumors. The trafficking of these tumor-homing cells (stem cells, immune cells and cancer cells), which support proliferation of the viruses, is mediated by specific chemokines and cell adhesion molecules and we are just beginning to understand the roles of these molecules. Finally, we will highlight some avenues deserving further study in order to achieve the ultimate goals of utilizing various OVs for effective cancer treatment.

Augmented transgene expression in transformed cells using a parvoviral hybrid vector

Autonomous parvoviruses possess an intrinsic oncotropism based on viral genetic elements controlling gene expression and genome replication. We constructed a hybrid vector consisting of the H1 parvovirus-derived expression cassette comprising the p4 promoter, the ns1 gene and the p38 promoter flanked by the adeno-associated viruses 2 (AAV2) inverted terminal repeats and packaged into AAV2 capsids. Gene transduction using this vector could be stimulated by coinfection with adenovirus, by irradiation or treatment with genotoxic agents, similar to standard AAV2 vectors. However, the latter were in most cases less efficient in gene transduction than the hybrid vector. With the new vector, tumor cell-selective increase in transgene expression was observed in pairs of transformed and non-transformed cells, leading to selective killing of the transformed cells after expression of a prodrug-converting enzyme. Preferential gene expression in tumor versus normal liver tissue was also observed in vivo in a syngeneic rat model. Comparative transduction of a panel of different tumor cell lines with the H1 and the H1/AAV hybrid vector showed a preference of each vector for distinct cell types, probably reflecting the dependence of the viral tropism on capsid determinants.