Combination Therapy with Conditionally Replicating Adenovirus and Replication Defective Adenovirus

Oncolytic Adenovirus in Cancer Immunotherapy

Tumor-selective replicating "oncolytic" viruses are novel and promising tools for immunotherapy of cancer. However, despite their first success in clinical trials, previous experience suggests that currently used oncolytic virus monotherapies will not be effective enough to achieve complete tumor responses and long-term cure in a broad spectrum of cancers. Nevertheless, there are reasonable arguments that suggest advanced oncolytic viruses will play an essential role as enablers of multi-stage immunotherapies including established systemic immunotherapies. Oncolytic adenoviruses (oAds) display several features to meet this therapeutic need. oAds potently lyse infected tumor cells and induce a strong immunogenic cell death associated with tumor inflammation and induction of antitumor immune responses. Furthermore, established and versatile platforms of oAds exist, which are well suited for the incorporation of heterologous genes to optimally exploit and amplify the immunostimulatory effect of viral oncolysis. A considerable spectrum of functional genes has already been integrated in oAds to optimize particular aspects of immune stimulation including antigen presentation, T cell priming, engagement of additional effector functions, and interference with immunosuppression. These advanced concepts have the potential to play a promising future role as enablers of multi-stage immunotherapies involving adoptive cell transfer and systemic immunotherapies.

Mesenchymal Stromal Cells for Linked Delivery of Oncolytic and Apoptotic Adenoviruses to Non-small-cell Lung Cancers

Oncolytic adenoviruses (OAdV) represent a promising strategy for cancer therapy. Despite their activity in preclinical models, to date the clinical efficacy remains confined to minor responses after intratumor injection. To overcome these limitations, we developed an alternative approach using the combination of the OAdv ICOVIR15 with a replication incompetent adenoviral vector carrying the suicide gene of inducible Caspase 9 (Ad.iC9), both of which are delivered by mesenchymal stromal cells (MSCs). We hypothesized that coinfection with ICOVIR15 and Ad.iC9 would allow MSCs to replicate both vectors and deliver two distinct types of antitumor therapy to the tumor, amplifying the cytotoxic effects of the two viruses, in a non-small-cell lung cancer (NSCLC) model. We showed that MSCs can replicate and release both vectors, enabling significant transduction of the iC9 gene in tumor cells. In the in vivo model using human NSCLC xenografts, MSCs homed to lung tumors where they released both viruses. The activation of iC9 by the chemical inducer of dimerization (CID) significantly enhanced the antitumor activity of the ICOVIR15, increasing the tumor control and translating into improved overall survival of tumor-bearing mice. These data support the use of this innovative approach for the treatment of NSCLC.

Dissecting the roles of E1A and E1B in adenoviral replication and RCAd-enhanced RDAd transduction efficacy on tumor cells

Oncolytic viruses have recently received widespread attention for their potential in innovative cancer therapy. Many telomerase promoter-regulated oncolytic adenoviral vectors retain E1A and E1B. However, the functions of E1A and E1B proteins in the oncolytic role of replication-competent adenovirus (RCAd) and RCAd enhanced transduction of replication defective adenoviruses (RDAd) have not been addressed well. In this study, we constructed viruses expressing E1A alone, E1A plus E1B-19 kDa, and E1A plus E1B-19 kDa/55 kDa. We then tested their roles in oncolysis and replication of RCAd as well as their roles in RCAd enhanced transfection rate and transgene expression of RDAd in various cancer cells in vitro and in xenografted human NCI-H460 tumors in nude mice. We demonstrated that RCAds expressing E1A alone and plus E1B-19 kDa exhibited an obvious ability in replication and oncolytic effects as well as enhanced RDAd replication and transgene expression, with the former showed more effective oncolysis, while the latter exhibited superior viral replication and transgene promotion activity. However, RCAd expressing both E1A and E1B-19 kDa/55 kDa was clearly worst in all these abilities. The effects of E1A and E1B observed through using RCAd were further validated by using plasmids expressing E1A alone, E1A plus E1B-19 kDa, and E1A plus E1B-19 kDa/55 kDa proteins. Our study provided evidence that E1A was essential for inducing replication and oncolytic effects of RCAd as well as RCAd enhanced RDAd transduction, and expression of E1B-19 kDa other than E1B-55 kDa could promote these effects. E1B-55 kDa is not necessary for the oncolytic effects of adenoviruses and somehow inhibits RCAd-mediated RDAd replication and transgene expression.

Combination of autophagy inducer rapamycin and oncolytic adenovirus improves antitumor effect in cancer cells

Background

Combination of oncolytic adenoviruses (Ads) and chemotherapy drugs has shown promising therapeutic results and is considered as a potential approach for cancer therapy. We previously have shown that autophagy may generate decomposed cellular molecules that can be used as nutrition to support virus replication in cancer cells. In this study, we evaluated a unique combination of the novel oncolytic Ad-cycE with rapamycin, an autophagy inducer and first-line chemotherapeutic drug.

Methods

The combination of oncolytic Ad-cycE and the autophagy inducer rapamycin was assessed for enhanced antitumor effect. We also evaluated the combined effects of rapamycin and Ad-cycE on cancer cell viability. The interaction between Ad-cycE and rapamycin was analyzed with Calcusyn (Biosoft, Ferguson, MO).

Results

We show that rapamycin induces autophagy, enhances Ad E1A expression and increases Ad oncolytic replication. Combination of rapamycin and Ad-cycE elicits stronger cytotoxicity than single treatment alone. The analyzed data indicates that the Ad-cycE and rapamycin combination has a significantly synergistic antitumor effect.

Conclusions

Our study provides a new insight into vector development and demonstrates the novel roles of autophagy in adenovirus replication. The combination of autophagy-induced chemotherapy and oncolytic virotherapy may be a new approach to improve future cancer treatment.

Enhanced cancer cell killing by truncated E2F-1 used in combination with oncolytic adenovirus

Adenovirus-mediated gene transfer into a tumor mass can be improved by combining it with conditionally-replicating adenovirus (CRAd) when both vectors co-infect the same cancer cell. We investigated the efficiency of enhancing transgene expression and effectiveness of cancer killing of two advenoviruses (Ads), one expressing E2F-1 (AdE2F-1) and another expressing a truncated form of E2F-1 that lacks the transactivation domain (AdE2Ftr), when combined with oncolytic Adhz60. We found that AdE2F-1 with Adhz60 actually decreased E2F-1 expression and viral replication through a mechanism apparently involving repression of the cyclin-E promoter and decreased expression of early and late structural proteins necessary for viral replication. In contrast, AdE2Ftr with Adhz60 resulted in increased E2Ftr expression, AdE2Ftr replication, and cancer cell death both in vitro and in vivo. These results indicate that AdE2Ftr coupled with a CRAd enhances AdE2Ftr-mediated cancer cell death.

Histone deacetylase inhibitors enhance the apoptotic activity of insulin-like growth factor binding protein-3 by blocking PKC-induced IGFBP-3 degradation

Overexpression of insulin-like growth factor binding protein (IGFBP)-3 induces apoptosis of cancer cells. However, preexisting resistance to IGFBP-3 could limit its antitumor activities. This study characterizes the efficacy and mechanism of the combination of recombinant IGFBP-3 (rIGFBP-3) and HDAC inhibitors to overcome IGFBP-3 resistance in a subset of non-small cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC) cells. The effects of the combination of rIGFBP-3 and a number of HDAC inhibitors on cell proliferation and apoptosis were assessed in vitro and in vivo by using the MTT assay, a flow cytometry-based TUNEL assay, Western blot analyses and the NSCLC xenograft tumor model. Combined treatment with HDAC inhibitors and rIGFBP-3 had synergistic antiproliferative effects accompanied by increased apoptosis rates in a subset of NSCLC and HNSCC cell lines in vitro. Moreover, combined treatment with depsipeptide and rIGFBP-3 completely suppressed tumor growth and increased the apoptosis rate in vivo in H1299 NSCLC xenografts. Evidence suggests that HDAC inhibitors increased the half-life of rIGFBP-3 protein by blocking protein kinase C (PKC)-mediated phosphorylation and degradation of rIGFBP-3. In addition, combined treatment of IGFBP-3 with an HDAC inhibitor facilitates apoptosis through upregulation of rIGFBP-3 stability and Akt signaling inhibition. The ability of HDAC inhibitors to decrease PKC activation may enhance apoptotic activities of rIGFBP-3 in NSCLC cells in vitro and in vivo. These results indicated that combined treatment with HDAC inhibitor and rIGFBP-3 could be an effective treatment strategy for NSCLC and HNSCC with highly activated PKC.

Antiangiogenic antitumor activities of IGFBP-3 are mediated by IGF-independent suppression of Erk1/2 activation and Egr-1-mediated transcriptional events

Most antiangiogenic therapies currently being evaluated in clinical trials target the vascular endothelial growth factor pathway; however, the tumor vasculature can acquire resistance to vascular endothelial growth factor-targeted therapy by shifting to other angiogenesis mechanisms. Insulin-like growth factor binding protein-3 (IGFBP-3) has been reported to suppress tumor growth and angiogenesis by both IGF-dependent and IGF-independent mechanisms; however, understanding of its IGF-independent mechanisms is limited. We observed that IGFBP-3 blocked tumor angiogenesis and growth in non-small cell lung cancer and head and neck squamous cell carcinoma. Conditioned media from an IGFBP-3-treated non-small cell lung cancer cell line displayed a significantly decreased capacity to induce HUVEC proliferation and aortic sprouting. In cancer cells, IGFBP-3 directly interacted with Erk1/2, leading to inactivation of Erk1/2 and Elk-1, and suppressed transcription of early growth response protein 1 and its target genes, basic fibroblast growth factor and platelet-derived growth factor. These data suggest that IGF-independent Erk1/2 inactivation and decreased IGFBP-3-induced Egr-1 expression block the autocrine and paracrine loops of angiogenic factors in vascular endothelial and cancer cells. Together, these findings provide a molecular framework of IGFBP-3's IGF-independent antiangiogenic antitumor activities. Future studies are needed for development of IGFBP-3 as a new line of antiangiogengic cancer drug.

Identification of PEG10 and TSG101 as carcinogenesis, progression, and poor-prognosis related biomarkers for gallbladder adenocarcinoma

PEG10 is a transcriptional factor while TSG101 is involved in numerous cellular processes, including apoptotic resistance. Overexpression of PEG10 and TSG101 were observed in a variety of human cancers. However, their expression and clinical significance in gallbladder cancer (GBC) have not yet been identified. To understand the tumor biology of GBC at the molecular level, we examined PEG10 and TSG101 expression in 108 adenocarcinomas, 15 gallbladder polyps, 35 chronic cholecystitis tissues, and 46 peritumoral tissues by using immunohistochemistry. Overexpression of PEG10 and TSG101 was detected in gallbladder adenocarcinoma (48.1% and 47.2%, respectively). Conversely, there was less expression detected in the peritumoral tissues (19.6%), adenomatous polyps (13.3%), and gallbladder epithelium with chronic cholecystitis (5.1%) (p < 0.01, p < 0.05, and p < 0.01, respectively). Notably, the benign lesions with positive PEG10 and/or TSG101 expression showed moderately or severely atypical hyperplasia in gallbladder epithelium. The overexpression of PEG10 and TSG101 was significantly associated with differentiation, tumor mass, lymph node metastasis and invasion of adenocarcinoma. Univariate Kaplan-Meier analysis showed that overexpression of PEG10 (p = 0.041) and TSG101 (p = 0.025) was closely associated with decreased overall survival. Multivariate Cox regression analysis revealed that positive expression of PEG10 (p = 0.036) or TSG101 (p = 0.022) is a predictor of poor prognosis in gallbladder adenocarcinoma. Our study suggested that overexpression of PEG10 and TSG101 might be closely related to the carcinogenesis, progression, clinical biological behaviors, and prognosis of gallbladder adenocarcinoma.

Analysis of adenovirus trans-complementation-mediated gene expression controlled by melanoma-specific TETP promoter in vitro

BACKGROUND

Human adenoviruses (Ads) have substantial potential for clinical applications in cancer patients. Conditionally replicating adenoviruses (CRAds) include oncolytic adenoviruses in which expression of the immediate early viral transactivator protein E1A is controlled by a cancer cell-selective promoter. To enhance efficacy, CRAds are further armed to contain therapeutic genes. Due to size constraints of the capsid geometry, the capacity for packaging transgenes into Ads is, however, limited. To overcome this limitation, the employment of E1A-deleted replication-deficient viruses carrying therapeutic genes in combination with replication-competent CRAd vectors expressing E1A in trans has been proposed. Most trans-complementing studies involved transgene expressions from strong ubiquitous promoters, and thereby relied entirely on the cancer cell specificity of the CRAd vector.

RESULTS

Here we tested the trans-complementation of a CRAd and a replication-deficient transgene vector containing the same cancer cell-selective promoter. Hereto, we generated two new vectors expressing IL-2 and CD40L from a bicistronic expression cassette under the control of the melanoma/melanocyte-specific tyrosinase enhancer tyrosinase promoter (TETP), which we previously described for the melanoma-specific CRAd vector AdDeltaEP-TETP. These vectors gave rise to tightly controlled melanoma-specific transgene expression levels, which were only 5 to 40-fold lower than those from vectors controlled by the nonselective CMV promoter. Reporter analyses using Ad-CMV-eGFP in combination with AdDeltaEP-TETP revealed a high level of trans-complementation in melanoma cells (up to about 30-fold), but not in non-melanoma cells, unlike the AdCMV-eGFP/wtAd5 binary vector system, which was equally efficient in melanoma and non-melanoma cells. Similar findings were obtained when replacing the transgene vector AdCMV-eGFP with AdCMV-IL-2 or AdCMV-CD40L. However, the combination of the novel AdTETP-CD40L/IL-2 vector with AdDeltaEP-TETP or wtAd5 gave reproducible moderate 3-fold enhancements of IL-2 by trans-complementation only.

CONCLUSIONS

The cancer cell-selective TETP tested here did not give the expected enforceable transgene expression typically achieved in the Ad trans-complementing system. Reasons for this could include virus-mediated down regulation of limiting transcription factors, and/or competition for such factors by different promoters. Whether this finding is unique to the particular promoter system tested here, or also occurs with other promoters warrants further investigations.

Enhanced pancreatic cancer gene therapy by combination of adenoviral vector expressing c-erb-B2 (Her-2/neu)-targeted immunotoxin with a replication-competent adenovirus or etoposide

Pancreatic cancer is the fourth leading cause of cancer-related death in the United States, and even under optimal therapy these patients face a poor prognosis. Here we report a novel gene therapy-based strategy to battle this disease. We show that the majority of pancreatic tumors overexpress c-erb-B2, which therefore might serve as a target for novel therapies. On the basis of these findings, we developed an adenoviral vector [Ad-e23(scFv)-PE40] encoding a c-erb-B2 (Her-2/neu)-targeted immunotoxin. To improve viral gene delivery we coinfected the therapeutic adenovirus with a replication-competent adenovirus (RCAd) at low doses that enhanced the transduction efficiency of the former virus. In addition, we show that target gene expression can be enhanced by adding etoposide (VP16) at nontherapeutic doses. To investigate the therapeutic efficacy of our approach we established a mouse model for advanced pancreatic cancer disease by intraperitoneal injection of pancreatic cancer cell lines, resulting in multifocal peritoneal xenograft tumors. Administration of Ad-e23(scFv)-PE40 in combination with RCAd and VP16 significantly inhibited tumor growth in mice, with no apparent systemic toxicity. In this study we show that c-erb-B2 might be an effective molecular target in the treatment of pancreatic tumors and that coadministration of a therapeutic c-erb-B2-targeted, non-replication-competent adenovirus with an RCAd and VP16 could be a powerful approach to effectively deliver therapeutic genes to tumors. As demonstrated, this strategy can be employed to effectively treat pancreatic cancer in particular, but may be modified to treat other types of cancer as well.

hTERT-promoter-dependent oncolytic adenovirus enhances the transduction and therapeutic efficacy of replication-defective adenovirus vectors in pancreatic cancer cells

Adenovirus-mediated gene therapy shows promise for cancer therapy, but transgene expression of replication-defective adenovirus may be low and transient in clinical settings. Recent reports have shown that the use of a conditionally replication-competent adenovirus (CRAd) enhanced the gene transduction of a replication-defective adenovirus vector. The control of tumor-stromal interactions has also been determined to be important in cancer therapy. In this study, we investigated the effect of the human telomerase reverse transcriptase (hTERT)-CRAd, Ad5/3hTERTE1, which possesses the tumor-specific hTERT promoter with the chimeric fiber 5/3, on the transgene expression and therapeutic efficacy of a replication-defective adenovirus vector expressing NK4 under the control of the CMV promoter, Ad-NK4. In addition, we established a new strategy to target both cancer cells and cancer-stromal interactions. Human pancreatic cancer cells were infected with Ad-NK4 and either Ad5/3hTERTE1 (CRAd-combination group) or Ad5/3hTERTLuc (control-combination group). In the CRAd-combination group, Ad-NK4-delivered transgene expression was increased, leading to an enhanced inhibitory effect on the invasion of cancer cells. In in vivo experiments, NK4 expression within tumors and its inhibitory effect on tumor growth, angiogenesis, and metastasis were enhanced in the CRAd-combination group. These results suggest that hTERT-CRAd enhances the transgene expression and therapeutic efficacies of Ad-NK4, possibly through the in-trans replication of Ad-NK4 induced by adenovirus E1 derived from co-infected hTERT-CRAd. This approach may be a promising combination therapy against advanced pancreatic cancer.

Conditionally replicating adenovirus improves gene replication efficiency and anticancer effect of E1-deleted adenovirus carrying TRAIL in head and neck squamous cell carcinoma

To overcome the low efficiency of gene therapy, we combined a conditionally replicating adenovirus (CRAd) and an adenoviral vector with a therapeutic gene. CRAd has an oncolytic activity in cancer cells with abnormal Rb activity and helps the replication of therapeutic genes incorporated in the E1-deleted adenovirus. We investigated the anticancer effect of a combination of CRAd and adenovirus carrying tumor necrosis factor-related apoptosis inducing ligand (ad-TRAIL). We expected to see increased gene expression in cancer cells as well as an antitumor effect. With the combined application of CRAd and ad-luciferase in head and neck cancer cell lines, we observed considerably increased luciferase activity that was 10- to 50-fold greater than with ad-luciferase alone. The combination of CRAd and ad-TRAIL showed significant suppression of growth in cell lines and increased the sub-G(1) portion of cells 30-fold compared to any single treatment. The expression of TRAIL was highly amplified by the combined treatment and was accompanied by expression of molecules related to apoptosis. In a xenograft animal model, mice treated with CRAd and ad-TRAIL showed complete regression of established tumors, whereas mice treated with CRAd or ad-TRAIL alone did not. In conclusion, this combined strategy using CRAd and adenovirus carrying a therapeutic gene increased the gene transfer rate and enhanced antitumor effects. We expect that this combination strategy could be extended to a multitarget cancer gene therapy by combining multiple adenoviruses and CRAd.

Therapy of head and neck squamous cell carcinoma with replicative adenovirus expressing tissue inhibitor of metalloproteinase-2 and chemoradiation

Recent studies have demonstrated the efficacy of targeted therapy combined with radiotherapy in head and neck squamous cell carcinoma (HNSCC). We hypothesized that a combination treatment including a replicating adenovirus armed with tissue inhibitor of metalloproteinase-2 (TIMP-2), radiation and Cisplatin will augment treatment response and reduce tumor growth in vivo of HNSCC xenografts. Both single-agent (TIMP-2 virus, radiation and Cisplatin) and the combination therapies were evaluated in vitro and in vivo. The efficacy of both single-agent and combination therapies in vivo was determined by monitoring tumor growth and immunohistochemistry. Treatment with replicative Ad-TIMP-2 virus and radiation decreased cell viability in vitro and resulted in an additional antiangiogenic response in vivo. Tumor response rates to treatment with replicative Ad-TIMP-2, radiation, Cisplatin or combination therapies ranged from limited inhibition of tumor growth of the single-agent therapy to a statistically significant additive antitumor response with the combination therapies. Replicative Ad-TIMP-2+radiation+Cisplatin in the SCC1 nude mice demonstrated the greatest response rates in tumor growth and angiogenesis. Combination of Ad-TIMP-2 gene therapy with radiation and the triple treatment group resulted in an augmented therapeutic response. This is the first report of the potential benefits of combining radiation and MMP inhibitor treatment.

E1A, E1B double-restricted replicative adenovirus at low dose greatly augments tumor-specific suicide gene therapy for gallbladder cancer

Combination therapy with replicative oncolytic viruses is a recent topic in innovative cancer therapy, but few studies have examined the efficacy of oncolytic adenovirus plus replication-deficient adenovirus carrying a suicide gene. We aim to evaluate whether an E1A, E1B double-restricted oncolytic adenovirus, AxdAdB-3, can improve the efficacy for gallbladder cancers (GBCs) of the replication-deficient adenovirus-based herpes simplex virus thymidine kinase (HSVtk)/ganciclovir (GCV) therapy directed by the carcinoembryonic antigen (CEA) promoter. Cytopathic effects of AxdAdB-3 plus AxCEAprTK (an adenovirus expressing HSVtk directed by CEA promoter) or AxCAHSVtk (an adenovirus expressing HSVtk directed by a nonspecific CAG promoter) with GCV administration were examined in several GBC lines and normal cells. Efficacy in vivo was tested in severe combined immunodeficiency disease mice with GBC xenografts. Addition of AxdAdB-3 (1 multiplicity of infection, MOI) significantly enhanced the cytopathic effects of AxCEAprTK (10 MOI)/GCV on GBC cells. The augmented effect was attributable to the replication of the AxCEAprTK and also to the enhanced CEA promoter activity, which was presumably transactivated by E1A. In normal cells, AxdAdB-3 (20 MOI) plus AxCEAprTK (200 MOI)/GCV was not cytopathic, whereas AxdAdB-3 (1 MOI) plus AxCAHSVtk (10 MOI)/GCV was significantly toxic. Low-dose AxdAdB-3 (2 x 10(7) PFU, plaque-forming unit) plus AxCEAprTK (2 x 10(8) PFU)/GCV significantly suppressed the growth of GBC xenografts as compared with either AxdAdB-3 (2 x 10(7) PFU)/GCV or AxCEAprTK (2 x 10(9) PFU)/GCV alone. E1A, E1B double-restricted replicating adenovirus at low dose significantly augmented the efficacy of CEA promoter-directed HSVtk/GCV therapy without obvious toxicity to normal cells, suggesting a potential use of this combination for treating GBC and other CEA-producing malignancies.

Treatment of hepatocellular carcinoma by AdAFPep/rep, AdAFPep/p53, and 5-fluorouracil in mice

Although conditionally replicable adenovirus (CRAd) has been used in the clinical treatment of hepatocellular carcinoma (HCC), it suffers from the inherent drawback of having relatively low antitumor activity. Here, we have sought to overcome this drawback. First, we combined CRAd (AdAFPep/Rep) driven by alpha-fetoprotein enhancer/promoter (AFPep) with a replication-incompetent adenovirus carrying a p53 transgene that is also driven by AFPep. The synergism of this combination produced a significantly improved tumoricidal effect on the human HCC cell line Hep3B, which has a relatively short doubling time in comparison with other human HCC cell lines, through the transactivation of p53 by early region 1A transcribed by AdAFPep/Rep. This synergistic interaction was augmented by the addition of a subtumoricidal dose (0.5 microg/mL) of 5-fluorouracil (5-FU), which enhanced p53 expression and facilitated the release of virions from tumor cells. When relatively large (10-mm-diameter) Hep3B tumors grown in nude mice were injected with the two viruses in combination, they showed significantly impaired growth in comparison with those treated with each virus separately. The growth suppression effect of the virus combination was enhanced by a low dose (600 microg) of 5-FU. Survival of the tumor-bearing mice treated with these three agents was significantly longer than that of control mice. Moreover, the tumor completely disappeared with the repeated injection of these agents.

CONCLUSION

This combination strategy holds promise for the treatment of relatively large and rapidly growing HCCs that may be encountered clinically.

Evaluation of twenty-one human adenovirus types and one infectivity-enhanced adenovirus for the treatment of malignant melanoma

Advanced melanoma is associated with poor prognosis warranting the development of new therapeutics, such as oncolytic adenoviruses for immunovirotherapy. Since this approach critically depends on efficient transduction of targeted tumor cells, we screened a panel of 22 different adenovirus types for their internalization efficiency in melanoma cells. We demonstrated that the virions of Ad35, Ad38, and Ad3 have significantly higher internalization efficiency in melanoma cells than Ad5, so far the only adenovirus type used in clinical trials for melanoma. Therefore, we developed a conditionally replication-competent Ad5-based vector with the Ad35 fiber shaft and knob domains (Ad5/35) and compared its therapeutic efficacy with the homologous vector carrying the native Ad5 fiber. To further enhance virotherapy, we combined the oncolytic adenovirus vectors with intratumoral expression of measles virus fusogenic membrane glycoproteins H and F (MV-H/F) and dacarbazine chemotherapy. In a human melanoma xenograft model, established from a short-term culture of primary melanoma cells, we demonstrated that the Ad5/35-based therapy had a significantly greater anti-neoplastic effect than the homologous Ad5-based therapy. Furthermore, the combination of virotherapy, intratumoral expression of MV-H/F, and chemotherapy was clearly superior to single- or double-agent therapy. In conclusion, Ad35-based vectors are promising for the treatment of melanoma.

Comparison of herpes simplex virus- and conditionally replicative adenovirus-based vectors for glioblastoma treatment

In this study we compared side-by-side the anti-neoplastic activity of the oncolytic herpes simplex virus-1 (HSV-1) vector G47Delta with that of a conditionally replicative adenoviral vector for the treatment of glioblastoma. We analyzed the transduction efficiency of permanent glioblastoma cell lines and short-term cultures of glioblastoma cells with HSV.Luc and four adenovirus type 5 (Ad5)-based vectors that differed only in their fiber gene (Ad5.Luc, AdlucRGD, and the fiber chimeric vectors Ad5/3.Luc and Ad5/35.Luc). In the tested short-term cultures of glioblastoma cells the vectors Ad5/35.Luc and HSV.Luc had an equal transduction efficiency which was approximately 70% higher than that of Ad5.Luc. In a subcutaneous xenograft glioblastoma model in nude mice we observed a significantly higher local tumor control with the G47Delta vector compared to the conditionally replicative Ad5/35 adenovirus. We confirmed in glioblastoma that the intratumoral expression of measles virus fusogenic membrane glycoproteins (FMG) encoded by replication-defective Ad5/35 or HSV-1 amplicon vectors synergistically enhances chemotherapy with temozolomide. The anti-neoplastic effect was superior when the replication-defective FMG encoding vectors were trans-complemented for replication with the respective oncolytic vector. This approach was necessary due to packaging constraints of adenovirus. At day 100, of 6 treated animals 1 was alive that received the Ad5/35- and 3 that received the HSV-1-based triple therapy. In an intracranial glioblastoma xenograft model we demonstrated the applicability of this strategy. Due to the higher oncolytic efficacy and packaging capacity of the HSV-1 vectors compared to adenovirus, these vectors are promising for the treatment of glioblastoma.

Evaluation of twenty human adenoviral types and one infectivity-enhanced adenovirus for the therapy of soft tissue sarcoma

The clinical course of sarcoma warrants the development of new therapeutic options, such as gene therapy. However, the lack of coxsackievirus-adenovirus receptor (CAR) on sarcoma cells limits the efficacy of adenovirus type 5 (Ad5)-based gene therapy. In this study we evaluated 20 different adenoviral types and 1 Ad5 vector with RGD-containing fiber for their internalization efficiency in sarcoma cells. We demonstrated that adenovirus types 35, 3, 7, 11, 9, and 22 and Ad5lucRGD virions (ranked in descending order) have significantly higher internalization efficiency in the tested sarcoma cells when compared with Ad5. On the basis of these results we developed a conditionally replication-competent adenoviral vector, Ad5Delta24.Ki.COX, and compared its oncolytic efficacy with that of Ad5/35Delta24.Ki.COX, an Ad5-based vector with the Ad35 fiber shaft and knob domains. Because both vectors differed only in the fiber, we were able to assess whether the adenoviral type with the most efficient internalization resulted also in enhanced treatment efficacy. We evaluated the antineoplastic activity of the oncolytic adenoviral vectors alone or in combination with the expression of measles virus fusogenic membrane glycoproteins and/or ifosfamide. The findings of our xenograft model were as follows: animals that received Ad5/35-based therapy had significantly smaller tumors than animals treated with the homologous Ad5-based vectors. In addition, we demonstrated that the combination of virotherapy, intratumoral expression of fusogenic membrane glycoproteins, and ifosfamide was clearly superior compared with treatment with individual components alone or as combinations of two components. In conclusion, Ad35-based vectors are promising for the treatment of sarcoma.

Gene therapy for lung cancer

Lung cancer patients suffer a 15% overall survival despite advances in chemotherapy, radiation therapy, and surgery due to the usual finding of advanced disease at diagnosis. Attempts to improve survival in advanced disease using various combinations of chemotherapy have demonstrated that no regimen is superior, suggesting a therapeutic plateau and the need for novel, more specific, and less toxic therapeutic strategies. Techniques have been developed that allow transfer of functional genes into mammalian cells, such as those that block activated tumor-promoting oncogenes and/or those that replace inactivated tumor-suppressing or apoptosis-promoting genes. This article will discuss the therapeutic implications of these molecular changes associated with bronchogenic carcinomas, and will then review the status of gene therapies for treatment of lung cancer.

Radioprotective effect of heat shock protein 25 on submandibular glands of rats

Irradiation (IR) is a fundamental treatment modality for head and neck malignancies. However, a significant drawback of IR treatment is irreversible damage of salivary gland in the IR field. In the present study, we investigated whether heat shock protein (HSP) 25 could be used as a radioprotective molecule for radiation-induced salivary gland damage in rats. HSP25 as well as inducible HSP70 (HSP70i) that were delivered to the salivary gland via an adenoviral vector significantly ameliorated radiation-induced salivary fluid loss. Radiation-induced apoptosis, caspase-3 activation, and poly(ADP-ribose) polymerase cleavage in acinar cells, granular convoluted cells, and intercalated ductal cells were also inhibited by HSP25 or HSP70i transfer. The alteration of salivary contents, including amylase, protein, Ca+, Cl-, and Na+, was also attenuated by HSP25 transfer. Histological analysis revealed almost no radiation-induced damage in salivary gland when HSP25 was transferred. Aquaporin 5 expression in salivary gland was inhibited by radiation; and HSP25 transfer to salivary gland prevented this alteration. The protective effect of HSP70i on radiation-induced salivary gland damage was less or delayed than that of HSP25. These results indicate that HSP25 is a good candidate molecule to protect salivary gland from the toxicity of IR.

Enhanced killing of pancreatic cancer cells by expression of fusogenic membrane glycoproteins in combination with chemotherapy

Pancreatic cancer has a poor prognosis with an annual mortality rate close to the annual incidence rate. We evaluated whether the expression of measles virus fusogenic membrane glycoproteins (FMG) H and F will enhance chemotherapy. Using Chou-Talalay analysis, we showed in vitro in pancreatic cancer cells that the expression of FMG often synergistically enhances clinically relevant chemotherapy. Furthermore, cell fusion in combination with chemotherapy resulted in strongly enhanced Annexin V binding, an early marker for apoptosis, when compared with single treatment. We showed in an i.p. and s.c. pancreatic xenograft model that the administration of a replication-defective adenoviral vector Ad.H/F encoding tumor-restricted FMG in combination with gemcitabine significantly enhanced treatment outcome when compared with treatment with each compound individually. To improve tumor transduction efficiency, the Ad.H/F vector was also transcomplemented with an oncolytic replication-restricted adenovirus (Ad.COX*MK), resulting in significantly improved treatment efficacy. We assessed treatment efficacy by survival analysis or measuring growth, respectively. In the i.p. model, on day 120, three of eight animals treated with this novel triple therapy consisting of Ad.H/F, gemcitabine, and Ad.COX*MK were alive and tumor free. Treatment with Ad.H/F and Ad.COX*MK resulted in one long-term survivor. In all other treatment groups, there were no long-term survivors. The significantly improved therapeutic outcome of animals receiving the triple therapy was attributed to multiple factors, including most likely improved FMG expression throughout the tumor and enhanced sensitivity of the tumor cells to gemcitabine by adenoviral gene products but also FMG expression. Qualitatively similar results were obtained in a s.c. pancreatic xenograft model.

Adenovirus expressing shRNA to IGF-1R enhances the chemosensitivity of lung cancer cell lines by blocking IGF-1 pathway

RNA interference is a phenomenon whereby small double-stranded RNA knocks down the expression of a sequence-specific gene. Double-stranded siRNA transfection, as currently used, is considered to have transient and low transfection efficiency. We constructed an adenoviral vector-based short hair-pin(sh)RNA system to overcome the limitations of the genetic blockade of IGF-1R, one of most important cancer therapy targets. We constructed three different IGF-1R specific shRNAs (612, 801, and 3425) and generated three ad-shIGF-1Rs using BD Adeno-X expression system. We assessed the effect of ad-shIGF-1R on signal transduction, induction of apoptosis, and in vitro tumorigenicity of lung cancer cell lines. Western blot and FACS assays demonstrated that endogenous IGF-1R expression was efficiently suppressed after transduction of lung cancer cell lines with the three different ad-shIGF-1Rs. IGF-1R blockade by ad-shIGF-1R inhibited ligand induced phosphorylation of pAkt and pErk, and ad-shIGF-1R effectively blocked the in vitro tumorigenicity of lung cancer cell lines. Moreover, the transduction of a human lung cancer cell line with ad-IGF-1R(3425) enhanced chemosensitivity to anticancer drugs. We conclude that the adenoviral vector-based approach to the RNA interference of IGF-1R induced effective IGF-1R silencing in lung cancer cell lines as manifested by effective blocking of the downstream pathway of IGF-1R and by an antitumor effect. We believe that this system can be usefully applied to other cancer targets.

Gene therapy for lung cancer

Lung cancer patients suffer a 15% overall survival despite advances in chemotherapy, radiation therapy, and surgery. This unacceptably low survival rate is due to the usual finding of advanced disease at diagnosis. However, multimodality strategies using conventional therapies only minimally improve survival rates even in early stages of lung cancer. Attempts to improve survival in advanced disease using various combinations of platinum-based chemotherapy have demonstrated that no regimen is superior, suggesting a therapeutic plateau and the need for novel, more specific, and less toxic therapeutic strategies. Over the past three decades, the genetic etiology of cancer has been gradually delineated, albeit not yet completely. Understanding the molecular events that occur during the multistep process of bronchogenic carcinogenesis may make these tasks more surmountable. During these same three decades, techniques have been developed which allow transfer of functional genes into mammalian cells. For example, blockade of activated tumor-promoting oncogenes or replacement of inactivated tumor-suppressing or apoptosis-promoting genes can be achieved by gene therapy. This article will discuss the therapeutic implications of these molecular changes associated with bronchogenic carcinomas and will then review the status of gene therapies for treatment of lung cancer.

INSULIN‐LIKE GROWTH FACTOR‐I RECEPTOR AS A CANDIDATE FOR A NOVEL MOLECULAR TARGET IN GASTROINTESTINAL CANCERS

Abnormal activation of growth factor receptors and their signal pathways are required for neoplastic transformation and tumor progression. The concept of targeting specific tumorigenic receptors has been validated by successful clinical application of multiple new drugs, such as those acting against HER2/neu, epidermal growth factor receptor 1, and c‐Kit. In this review, we focus on the next promising therapeutic molecular target of insulin‐like growth factor (IGF)‐I receptor (IGF‐Ir). The IGF/IGF‐Ir system is an important modifier of cancer cell proliferation, survival, growth, and treatment sensitivity in a number of neoplastic diseases, including human gastrointestinal carcinomas. Preclinical studies demonstrated that downregulation of IGF‐Ir signals reversed the neoplastic phenotype and sensitized cells to antitumor treatments. We summarize a variety of ways to disrupt IGF‐Ir function. Then, we introduce our strategy of adenoviruses expressing dominant negative of IGF‐Ir (IGF‐Ir/dn) against gastrointestinal cancers, including stomach, colon, and pancreas. IGF‐Ir/dn suppresses tumorigenicity both in vitro and in vivo and increases stressor‐induced apoptosis. IGF‐Ir/dn expression upregulates chemotherapy‐induced apoptosis and these combination therapies with chemotherapy are very effective against tumors in mice. Some drugs blocking IGF‐Ir function are now entering clinical trial, thus IGF‐Ir might be a candidate for a therapeutic target in several gastrointestinal malignancies.

Multiple bronchioloalveolar carcinomas in acromegaly: a potential role of insulin-like growth factor I in carcinogenesis

The molecular pathogenesis of lung cancer, especially multiple and synchronous bronchioloalveolar carcinomas (BACs), is still unknown. Here, we report two cases of multiple BACs associated with acromegaly, and discuss about the possible relationship between these two pathological condition. The first patient was a 52-year-old female with a history of Hardy's surgery for pituitary growth hormone cell adenoma 2 years earlier. The second patient was a 57-year-old female with acromegaly and obstructive sleep apnea syndrome. Both patients were non-smokers and showed a high serum level of insulin-like growth factor I (IGF-I) at the time of admission, even though the level of growth hormone had decreased. High-resolution computed tomography (HRCT) revealed multiple small nodules with pure ground-glass opacity (GGO) in both lungs of the first patient and a small nodule with pure GGO in the right lung of the second one. Partial resection for these tumors were performed under video-assisted thoracoscopic surgery. Resected lung specimens of the first case revealed one papillary adenocarcinoma, seven BACs, and 11 atypical adenomatous hyperplasias (AAHs). The second case showed two foci of BACs. Immunohistochemically, all BACs were strongly positive for IGF-IR which is a specific receptor for IGF-I, and all AAHs were also weakly positive for IGF-IR. Since IGF-I is known as a potent growth factor for normal as well as cancerous cells, it might play an important role for tumorigenesis and/or tumor progression of BACs through its interaction with and/or upregulation of IGF-IR. In addition, much attention should be paid to detect lung lesions in acromegaly with high serum level of IGF-I.

Synergy between expression of fusogenic membrane proteins, chemotherapy and facultative virotherapy in colorectal cancer

Using Chou-Talalay median effect analysis, we demonstrated in permanent and short-term cultures of colorectal cancer cells that the expression of measles virus fusogenic membrane glycoproteins (FMGs) in combination with chemotherapy often causes over most of the cytotoxic dose range synergistic cell killing. In this combined treatment, we observed strongly enhanced annexin V binding and caspase-3/7 activity when compared to single-agent treatment. Furthermore, we showed increased expression of heat-shock protein (Hsp)70 and Hsp90alpha, but not of Hsp60. In a subcutaneous HT-29 colorectal xenograft model, we demonstrated that the administration of a replication-defective adenoviral or herpes simplex virus (HSV) amplicon vector (Ad.H/F or HSV.H/F) encoding tumor-restricted FMG in combination with FOLFOX significantly enhanced treatment outcome when compared to treatment with each compound individually. To increase the fraction of tumor cells expressing the FMG, we trans-complemented the Ad.H/F and HSV.H/F vector with the respective oncolytic replication-restricted adenovirus Ad.COXDeltaMK or HSV-1 G47Delta vector. At the end of the observation period (day 100), eight out of 10 animals that received G47Delta, HSV.H/F and FOLFOX were alive and tumor free. Administration of the analogous adenovirus-based regimen resulted in four out of 10 long-term survivors. We demonstrated that the expression of FMG in combination with chemotherapy can significantly enhance treatment outcome, which is further enhanced by combination with trans-complementing oncolytic vectors.

Combination therapy of androgen-independent prostate cancer using a prostate restricted replicative adenovirus and a replication-defective adenovirus encoding human endostatin-angiostatin fusion gene

Although prostate-restricted replicative adenovirus has exhibited significant antitumor efficacy in preclinical studies, it is necessary to develop more potent adenoviruses for prostate cancer gene therapy. We evaluated the synergistic killing effect of prostate-restricted replicative adenovirus and AdEndoAngio, a replication-defective adenovirus expressing the endostatin-angiostatin fusion protein (EndoAngio). When coadministered with AdEndoAngio, prostate-restricted replicative adenovirus significantly elevated EndoAngio expression, suggesting that AdEndoAngio coreplicates with prostate-restricted replicative adenovirus. Conditioned medium from prostate cancer cells infected by prostate-restricted replicative adenovirus plus AdEndoAngio inhibited the growth, tubular network formation, and migration of human umbilical vein endothelial cells better than conditioned medium from prostate cancer cells infected by AdEndoAngio alone. Furthermore, in vivo animal studies showed that the coadministration of prostate-restricted replicative adenovirus plus AdEndoAngio resulted in the complete regression of seven out of eight treated androgen-independent CWR22rv tumors, with a tumor nodule maintaining a small size for 14 weeks. The residual single tumor exhibited extreme pathologic features together with more endostatin-reactive antibody-labeled tumor cells and fewer CD31-reactive antibody-labeled capillaries than the AdEndoAngio-treated tumors. These results show that combination therapy using prostate-restricted replicative adenovirus together with antiangiogenic therapy has more potent antitumor effects and advantages than single prostate-restricted replicative adenovirus and deserves more extensive investigation.

Degradation of fibrillar collagen in a human melanoma xenograft improves the efficacy of an oncolytic herpes simplex virus vector

Oncolytic viral therapy provides a promising approach to treat certain human malignancies. These vectors improve on replication-deficient vectors by increasing the viral load within tumors through preferential viral replication within tumor cells. However, the inability to efficiently propagate throughout the entire tumor and infect cells distant from the injection site has limited the capacity of oncolytic viruses to achieve consistent therapeutic responses. Here we show that the spread of the oncolytic herpes simplex virus (HSV) vector MGH2 within the human melanoma Mu89 is limited by the fibrillar collagen in the extracellular matrix. This limitation seems to be size specific as nanoparticles of equivalent size to the virus distribute within tumors to the same extent whereas smaller particles distribute more widely. Due to limited viral penetration, tumor cells in inaccessible regions continue to grow, remaining out of the range of viral infection, and tumor eradication cannot be achieved. Matrix modification with bacterial collagenase coinjection results in a significant improvement in the initial range of viral distribution within the tumor. This results in an extended range of infected tumor cells and improved virus propagation, ultimately leading to enhanced therapeutic outcome. Thus, fibrillar collagen can be a formidable barrier to viral distribution and matrix-modifying treatments can significantly enhance the therapeutic response.

Selective intratumoral amplification of an antiangiogenic vector by an oncolytic virus produces enhanced antivascular and anti-tumor efficacy

The development of effective cancer therapy will require the simultaneous targeting of multiple steps in tumor development. We have previously described an antiangiogenic gene therapy vector, Ad Flk1-Fc, which expresses a soluble VEGF receptor capable of inhibiting tumor angiogenesis and growth. We have also described an oncolytic virus, dl922/947, whose replication and subsequent cytotoxicity are restricted to cancer cells with a loss of the G1-S cell cycle checkpoint. Here we have optimized methods for combining these therapies, yielding significantly greater anti-tumor effects than the respective monotherapies. In cultured tumor lines, co-infection with both Ad Flk1-Fc and dl922/947 allowed replication and repackaging of the replication-deficient Ad Flk1-Fc and enhanced soluble VEGF receptor expression. Similar repackaging and increased gene expression were demonstrated in vivo using bioluminescence imaging studies. Finally, coadministration of these therapeutic viral therapies in vivo produced significantly enhanced anti-tumor effects in colon HCT 116 and prostate PC-3 xenografts in mice. This increased therapeutic benefit correlated with replication of Ad Flk1-Fc viral genomes, increased intratumoral levels of Flk1-Fc protein, and decreased microvessel density, consistent with enhanced antiangiogenic activity.

In vivo Imaging of Adenovirus Transduction and Enhanced Therapeutic Efficacy of Combination Therapy with Conditionally Replicating Adenovirus and Adenovirus-p27

Gene therapy is hampered by poor gene transfer to the tumor mass. We previously proposed a combination adenoviral gene therapy containing a conditionally replicating adenovirus (CRAD) expressing mutant E1 (delta24RGD) and a replication-defective E1-deleted adenovirus to enhance the efficiency of gene transfer. Mutant E1 expressed by delta24RGD enables the replication of replication-defective adenoviruses in tumors when cancer cells are co-infected with both viruses. In this study, gene transfer rates in xenografts tumors were monitored by bioluminescence in cells infected with the replication-defective adenovirus-luciferase (ad-luc). Tumor masses treated with CRAD + ad-luc showed dramatically stronger and more prolonged luciferase expression than ad-luc-treated tumors and this expression spread through the entire tumor mass without significant systemic spread. Transduction with CRAD + replication-defective adenovirus-p27 increased the expression of p27 by 24-fold versus transduction with ad-p27 alone. Treatment of a lung cancer cell line and of established lung cancer xenografts with CRAD + adenovirus-p27 also induced stronger growth suppression than treatment with either virus alone. These findings confirm the selective replication of E1-deleted adenovirus containing a therapeutic gene due to the presence of mutant E1 produced by delta24RGD in tumors. Moreover, this replication increased the therapeutic gene transfer rate and enhanced its antitumor effects.

An oncolytic conditionally replicating adenovirus for hormone-dependent and hormone-independent prostate cancer

The use of conditionally replicating adenoviruses offers an attractive complementary treatment strategy for localized prostate cancer. We have produced a replicating adenovirus, Ad[I/PPT-E1A], where E1A gene expression is controlled by a recombinant regulatory sequence designated PPT. The PPT sequence comprises a PSA enhancer, a PSMA enhancer and a T-cell receptor gamma-chain alternate reading frame protein promoter, and it is shielded from transcriptional interference from adenoviral backbone sequences by an H19 insulator. Ad[I/PPT-E1A] yields prostate-specific E1A protein expression, viral replication and cytolysis in vitro. Furthermore, Ad[I/PPT-E1A] considerably regresses the growth of subcutaneous LNCaP prostate cancer tumors in nude mice. Importantly, the viral replication and cytolytic effect of Ad[I/PPT-E1A] are independent of the testosterone levels in the prostate cancer cells. This may be beneficial in a clinical setting since many prostate cancer patients are treated with androgen withdrawal. In conclusion, Ad[I/PPT-E1A] may prove to be useful in the treatment of localized prostate cancer.