Peritumoral injection of adenovirus vector expressing NK4 combined with gemcitabine treatment suppresses growth and metastasis of human pancreatic cancer cells implanted orthotopically in nude mice and prolongs survival

Beyond cancer cells: Targeting the tumor microenvironment with gene therapy and armed oncolytic virus

Cancer gene therapies are usually designed either to express wild-type copies of tumor suppressor genes or to exploit tumor-associated phenotypic changes to endow selective cytotoxicity. However, these approaches become less relevant to cancers that contain many independent mutations, and the situation is made more complex by our increased understanding of clonal evolution of tumors, meaning that different metastases and even regions of the same tumor mass have distinct mutational and phenotypic profiles. In contrast, the relatively genetically stable tumor microenvironment (TME) therefore provides an appealing therapeutic target, particularly since it plays an essential role in promoting cancer growth, immune tolerance, and acquired resistance to many therapies. Recently, a variety of different TME-targeted gene therapy and armed oncolytic strategies have been explored, with particular success observed in strategies targeting the cancer stroma, reducing tumor vasculature, and repolarizing the immunosuppressive microenvironment. Herein, we review the progress of these TME-targeting approaches and try to highlight those showing the greatest promise.

Effects of human placenta-derived mesenchymal stem cells with NK4 gene expression on glioblastoma multiforme cell lines

Poor prognosis and low survival are commonly seen in patients with glioblastoma multiforme (GBM). Due to the specific nature of solid tumors such as GBM, delivery of therapeutic agents to the tumor sites is difficult. So, one of the major challenges in the treatment of these tumors is a selection of appropriate method for drug delivery. Mesenchymal stem cells (MSCs) have a unique characteristic in migration toward the tumor tissue. In this regard, the present study examined the antitumor effects of manipulating human placenta-derived mesenchymal stem cells (PDMSCs) with NK4 expression (PDMSC-NK4) on GBM cells. After separation and characterization of PDMSCs, these cells were transduced with NK4 which was known as the antagonist of hepatocyte growth factor (HGF). The results indicated that engineered PDMSCs preferably migrate into GBM cells by transwell coculture system. In addition, the proliferation of the GBM cells significantly reduced after coculture with these cells. In fact, manipulated PDMSCs inhibited growth of tumor cells by induction of apoptosis. Our findings suggested that besides having antitumor effects, PDMSCs can also be applied as an ideal cellular vehicle to target the glioblastoma multiforme.

Tumor angiogenesis and anti-angiogenic gene therapy for cancer

When Folkman first suggested a theory about the association between angiogenesis and tumor growth in 1971, the hypothesis of targeting angiogenesis to treat cancer was formed. Since then, various studies conducted across the world have additionally confirmed the theory of Folkman, and numerous efforts have been made to explore the possibilities of curing cancer by targeting angiogenesis. Among them, anti-angiogenic gene therapy has received attention due to its apparent advantages. Although specific problems remain prior to cancer being fully curable using anti-angiogenic gene therapy, several methods have been explored, and progress has been made in pre-clinical and clinical settings over previous decades. The present review aimed to provide up-to-date information concerning tumor angiogenesis and gene delivery systems in anti-angiogenic gene therapy, with a focus on recent developments in the study and application of the most commonly studied and newly identified anti-angiogenic candidates for anti-angiogenesis gene therapy, including interleukin-12, angiostatin, endostatin, tumstatin, anti-angiogenic metargidin peptide and endoglin silencing.

Mesenchymal stem cell-based NK4 gene therapy in nude mice bearing gastric cancer xenografts

Mesenchymal stem cells (MSCs) have been recognized as promising delivery vehicles for gene therapy of tumors. Gastric cancer is the third leading cause of worldwide cancer mortality, and novel treatment modalities are urgently needed. NK4 is an antagonist of hepatocyte growth factor receptors (Met) which are often aberrantly activated in gastric cancer and thus represent a useful candidate for targeted therapies. This study investigated MSC-delivered NK4 gene therapy in nude mice bearing gastric cancer xenografts. MSCs were transduced with lentiviral vectors carrying NK4 complementary DNA or enhanced green fluorescent protein (GFP). Such transduction did not change the phenotype of MSCs. Gastric cancer xenografts were established in BALB/C nude mice, and the mice were treated with phosphate-buffered saline (PBS), MSCs-GFP, Lenti-NK4, or MSCs-NK4. The tropism of MSCs toward gastric cancer cells was determined by an in vitro migration assay using MKN45 cells, GES-1 cells and human fibroblasts and their presence in tumor xenografts. Tumor growth, tumor cell apoptosis and intratumoral microvessel density of tumor tissue were measured in nude mice bearing gastric cancer xenografts treated with PBS, MSCs-GFP, Lenti-NK4, or MSCs-NK4 via tail vein injection. The results showed that MSCs migrated preferably to gastric cancer cells in vitro. Systemic MSCs-NK4 injection significantly suppressed the growth of gastric cancer xenografts. MSCs-NK4 migrated and accumulated in tumor tissues after systemic injection. The microvessel density of tumor xenografts was decreased, and tumor cellular apoptosis was significantly induced in the mice treated with MSCs-NK4 compared to control mice. These findings demonstrate that MSC-based NK4 gene therapy can obviously inhibit the growth of gastric cancer xenografts, and MSCs are a better vehicle for NK4 gene therapy than lentiviral vectors. Further studies are warranted to explore the efficacy and safety of the MSC-based NK4 gene therapy in animals and cancer patients.

Gene therapy in pancreatic cancer

Pancreatic cancer (PC) is a highly lethal disease and notoriously difficult to treat. Only a small proportion of PC patients are eligible for surgical resection, whilst conventional chemoradiotherapy only has a modest effect with substantial toxicity. Gene therapy has become a new widely investigated therapeutic approach for PC. This article reviews the basic rationale, gene delivery methods, therapeutic targets and developments of laboratory research and clinical trials in gene therapy of PC by searching the literature published in English using the PubMed database and analyzing clinical trials registered on the Gene Therapy Clinical Trials Worldwide website (http://www. wiley.co.uk/genmed/ clinical). Viral vectors are main gene delivery tools in gene therapy of cancer, and especially, oncolytic virus shows brighter prospect due to its tumor-targeting property. Efficient therapeutic targets for gene therapy include tumor suppressor gene p53, mutant oncogene K-ras, anti-angiogenesis gene VEGFR, suicide gene HSK-TK, cytosine deaminase and cytochrome p450, multiple cytokine genes and so on. Combining different targets or combination strategies with traditional chemoradiotherapy may be a more effective approach to improve the efficacy of cancer gene therapy. Cancer gene therapy is not yet applied in clinical practice, but basic and clinical studies have demonstrated its safety and clinical benefits. Gene therapy will be a new and promising field for the treatment of PC.

Current knowledge on pancreatic cancer

Pancreatic cancer is the fourth leading cause of cancer death with a median survival of 6 months and a dismal 5-year survival rate of 3-5%. The development and progression of pancreatic cancer are caused by the activation of oncogenes, the inactivation of tumor suppressor genes, and the deregulation of many signaling pathways. Therefore, the strategies targeting these molecules as well as their downstream signaling could be promising for the prevention and treatment of pancreatic cancer. However, although targeted therapies for pancreatic cancer have yielded encouraging results in vitro and in animal models, these findings have not been translated into improved outcomes in clinical trials. This failure is due to an incomplete understanding of the biology of pancreatic cancer and to the selection of poorly efficient or imperfectly targeted agents. In this review, we will critically present the current knowledge regarding the molecular, biochemical, clinical, and therapeutic aspects of pancreatic cancer.

Significance of combination therapy of zoledronic acid and gemcitabine on pancreatic cancer

In the present study, we examined the cytotoxic effects of combination therapy with zoledronic acid (ZOL) and gemcitabine (GEM) on pancreatic cancer cells in vitro and in vivo. Four human pancreatic cancer cell lines were treated with ZOL, GEM or a combination of both, and the effects of the respective drug regimens on cell proliferation, invasion and matrix metalloproteinase (MMP) expression were examined. A pancreatic cancer cell line was also intrasplenically or orthotopically implanted into athymic mice and the effects of these drugs on tumor metastasis and growth in vivo were evaluated by histological and immunohistochemical analyses. Combination treatment with low doses of ZOL and GEM efficiently inhibited the proliferation (P < 0.001) and invasion (P < 0.001) of pancreatic cancer cells in vitro. Western blotting assay revealed that MMP-2 and MMP-9 expression levels were decreased after ZOL treatment. In vivo, combined treatment significantly inhibited tumor growth (P < 0.05) and the development of liver metastasis (P < 0.05). These data revealed that ZOL and GEM, when used in combination, have significant antitumor, anti-metastatic and anti-angiogenic effects on pancreatic cancer cells. The present study is the first to report the significance of the combination treatment of ZOL and GEM in pancreatic cancer using an in vivo model. These data are promising for the future application of this drug regimen in patients with pancreatic cancer.

Pancreatic cancer: gene therapy approaches and gene delivery systems

IMPORTANCE OF THE FIELD

Due to the absence of early diagnosis, the highly invasive and metastatic features and the lack of effective therapeutic modalities, the prognosis of patients with pancreatic cancer is poor. Gene therapy is currently regarded as a potential and promising therapeutic modality for pancreatic cancer.

AREAS COVERED IN THIS REVIEW

This article summarizes an update of gene therapy approaches and reviews the latest progress in gene delivery systems that have been tested on pancreatic cancer.

WHAT THE READER WILL GAIN

The treatment effectiveness of gene combination therapy is better than that of the regulation of single-gene or single gene therapy approaches. Naked DNA is limited because of degradation by intracellular and extracellular nucleases. Virus vectors show high transfection efficiency but are limited due to immunogenicity, inflammatory response and potential carcinogenicity. Non-viral vectors, such as cationic polymers or inorganic nanoparticles, show an important feature that they can be easily modified, and the progress of materials science will provide more and better non-viral vectors, accordingly improving the efficiency and safety of gene therapy, which will make them the most promising vectors for pancreatic cancer.

Up-regulation of integrin beta3 in radioresistant pancreatic cancer impairs adenovirus-mediated gene therapy

Adenovirus-mediated gene therapy is a promising approach for the treatment of pancreatic cancer. We previously reported that radiation enhanced adenovirus-mediated gene expression in pancreatic cancer, suggesting that adenoviral gene therapy might be more effective in radioresistant pancreatic cancer cells. In the present study, we compared the transduction efficiency of adenovirus-delivered genes in radiosensitive and radioresistant cells, and investigated the underlying mechanisms. We used an adenovirus expressing the hepatocyte growth factor antagonist, NK4 (Ad-NK4), as a representative gene therapy. We established two radioresistant human pancreatic cancer cell lines using fractionated irradiation. Radiosensitive and radioresistant pancreatic cancer cells were infected with Ad-NK4, and NK4 levels in the cells were measured. In order to investigate the mechanisms responsible for the differences in the transduction efficiency between these cells, we measured expression of the genes mediating adenovirus infection and endocytosis. The results revealed that NK4 levels in radioresistant cells were significantly lower (P < 0.01) than those in radiosensitive cells, although there were no significant differences in adenovirus uptake between radiosensitive cells and radioresistant cells. Integrin beta3 was up-regulated and the Coxsackie virus and adenovirus receptor was down-regulated in radioresistant cells, and inhibition of integrin beta3 promoted adenovirus gene transfer. These results suggest that inhibition of integrin beta3 in radioresistant pancreatic cancer cells could enhance adenovirus-mediated gene therapy.

Systemic NK4 gene therapy inhibits tumor growth and metastasis of melanoma and lung carcinoma in syngeneic mouse tumor models

Hepatocyte growth factor (HGF) promotes malignant development of cancer cells by enhancing invasion and metastasis. NK4, a competitive antagonist for HGF, is a bifunctional molecule that acts as a HGF antagonist and angiogenesis inhibitor. Although successful tumor inhibition by NK4 gene expression in tumor models has been demonstrated, the effects of systemic NK4 gene introduction are yet to be addressed. Here we show that systemic administration of a replication-defective adenovirus expressing NK4 (Ad.NK4) inhibits tumor growth and lung metastasis of B16F10 melanoma and Lewis lung carcinoma in syngeneic mice. Single tail-vein injection of Ad.NK4 achieved therapeutic levels of NK4 in the circulation and in multiple organs. Despite NK4 expression that was highest in the liver, toxicity in the liver was minimal. Ad.NK4-mediated growth inhibition was associated with decreased blood vessel density and increased apoptosis in tumor tissues, which suggests that NK4 suppressed tumor growth as an angiogenesis inhibitor. Metastasis of B16F10 melanoma and Lewis lung carcinoma cells to the lung was potently inhibited by systemic Ad.NK4-administration. Our results demonstrated that the adenovirus-mediated induction of high levels of circulating NK4 significantly inhibited in vivo tumor growth and distant metastasis without obvious side effects. NK4 gene therapy is thus a safe and promising strategy for the treatment of cancer patients, and further validation in clinical trials is needed.

Pancreatic cancer: molecular pathogenesis and new therapeutic targets

Patients with pancreatic cancer normally present with advanced disease that is lethal and notoriously difficult to treat. Survival has not improved dramatically despite routine use of chemotherapy and radiotherapy; this situation signifies an urgent need for novel therapeutic approaches. Over the past decade, a large number of studies have been published that aimed to target the molecular abnormalities implicated in pancreatic tumor growth, invasion, metastasis, angiogenesis and resistance to apoptosis. This research is of particular importance, as data suggest that a large number of genetic alterations affect only a few major signaling pathways and processes involved in pancreatic tumorigenesis. Although laboratory results of targeted therapies have been impressive, until now only erlotinib, an epidermal growth factor receptor tyrosine kinase inhibitor, has demonstrated modest survival benefit in combination with gemcitabine in a phase III clinical trial. Whilst the failures of targeted therapies in the clinical setting are discouraging, lessons have been learnt and new therapeutic targets that hold promise for the future management of the disease are continuously emerging. This Review describes some of the important developments and targeted agents for pancreatic cancer that have been tested in clinical trials.

Chemotherapeutic agents potentiate adenoviral gene therapy for pancreatic cancer

Adenovirus-mediated gene therapy combined with chemotherapeutic agents is expected to represent a new approach for treating pancreatic cancer. However, there have been no reports of definitive effects of chemotherapeutic agents on adenovirus-mediated gene therapies. In the present study, we investigated the effects of chemotherapeutic agents on the transduction efficiency of an adenovirus-based gene therapy. Adenovirus (Ad-NK4) expressing NK4, which acts as a hepatocyte growth factor antagonist, was used as a representative gene therapy. Pancreatic cancer cells infected with Ad-NK4 were treated with chemotherapeutic agents (5-fluorouracil [5FU], cisplatin or etoposide), and the NK4 levels in their culture media were measured. To examine the effects of chemotherapeutic agents in vivo, Ad-NK4 was administered to subcutaneous tumors in mice after treatment with the agents, and the tumor NK4 levels were measured. The NK4 levels in culture media from cells treated with 5FU, cisplatin and etoposide were 5.2-fold (P = 0.026), 6-fold (P < 0.001) and 4.3-fold (P < 0.001) higher than those of untreated cells, respectively. The chemotherapeutic agents also increased Ad-NK4 uptake. The NK4 levels in tumors treated with 5FU, cisplatin and etoposide were 5.4-fold (P = 0.006), 11.8-fold (P < 0.001) and 4.9-fold (P = 0.017) higher than those in untreated tumors, respectively. The present findings suggest that chemotherapeutic agents significantly improve the efficiency of adenovirus-mediated gene transfer in pancreatic cancer. Furthermore, they will contribute to decreases in the adenovirus doses required for gene transfer, thereby controlling the side-effects of adenovirus infection in normal tissues.

Hepatocyte growth factor and Met in tumor biology and therapeutic approach with NK4

Hepatocyte growth factor (HGF) and Met/HGF receptor tyrosine kinase play a role in the progression to invasive and metastatic cancers. A variety of cancer cells secrete molecules that enhance HGF expression in stromal fibroblasts, while fibroblast-derived HGF, in turn, is a potent stimulator of the invasion of cancer cells. In addition to the ligand-dependent activation, Met receptor activation is negatively regulated by cell-cell contact and Ser985 phosphorylation in the juxtamembrane of Met. The loss of intercellular junctions may facilitate an escape from the cell-cell contact-dependent suppression of Met-signaling. Significance of juxtamembrane mutations found in human cancers is assumed to be a loss-of-function in the negative regulation of Met. In attempts to block the malignant behavior of cancers, NK4 was isolated as a competitive antagonist against HGF-Met signaling. Independently on its HGF-antagonist action, NK4 inhibited angiogenesis induced by vascular endothelial cell growth factor and basic fibroblast growth factor, as well as HGF. In experimental models of distinct types of cancers, NK4 inhibited Met activation and this was associated with inhibition of tumor invasion and metastasis. NK4 inhibited tumor angiogenesis, thereby suppressing angiogenesis-dependent tumor growth. Cancer treatment with NK4 suppresses malignant tumors to be "static" in both tumor growth and spreading.

Single-agent and combination therapeutic strategies to inhibit hepatocyte growth factor/MET signaling in cancer

Receptor tyrosine kinases are often aberrantly activated in human malignancies and contribute to cancer development and progression. Specific receptor tyrosine kinase inhibitors have been shown to be clinically effective therapies in subsets of cancer patients with either hematologic or solid tumors. Activation of the hepatocyte growth factor (HGF)/MET signaling pathway has been found to play a critical role in oncogenesis, cancer metastasis, and drug resistance. These observations have led to the development of agents that can effectively inhibit HGF/MET signaling through direct inhibition of the receptor (anti-MET antibodies), through inactivation of its ligand HGF (AMG102, L2G7), by interfering with HGF binding to MET (NK4), or by inhibiting MET kinase activity (PHA-665752 and SU11274). Moreover, the combination of anti-MET therapeutic agents with either signal transduction inhibitors (ERBB family or mTOR inhibitors) or with cytotoxic chemotherapy has been evaluated in preclinical models. These studies provide insight into the rational development of combination therapeutic strategies that can be evaluated in clinical trials. This review will discuss different strategies of MET inhibition with a specific focus on combination therapeutic approaches.

Biological approaches to therapy of pancreatic cancer

Pancreatic cancer is a lethal disease and notoriously difficult to treat. Only a small proportion is curative by surgical resection, whilst standard chemotherapy for patients with advanced disease has only modest effect with substantial toxicity. Clearly there is a need for the continual development of novel therapeutic agents to improve the current situation. Improvement of our understanding of the disease has generated a large number of studies on biological approaches targeting the molecular abnormalities of pancreatic cancer, including gene therapy and signal transduction inhibition, antiangiogenic and matrix metalloproteinase inhibition, oncolytic viral therapy and immunotherapy. This article provides a review of these approaches, both investigated in the laboratories and in subsequent clinical trials.

Molecular signature and therapeutic perspective of the epithelial-to-mesenchymal transitions in epithelial cancers

The mechanisms involved in the epithelial to mesenchymal transition (EMT) are integrated in concert with master developmental and oncogenic pathways regulating in tumor growth, angiogenesis, metastasis, as well as the reprogrammation of specific gene repertoires ascribed to both epithelial and mesenchymal cells. Consequently, it is not unexpected that EMT has profound impacts on the neoplastic progression, patient survival, as well as the resistance of cancers to therapeutics (taxol, vincristine, oxaliplatin, EGF-R targeted therapy and radiotherapy), independent of the "classical" resistance mechanisms linked to genotoxic drugs. New therapeutic combinations using genotoxic agents and/or EMT signaling inhibitors are therefore expected to circumvent the chemotherapeutic resistance of cancers characterized by transient or sustained EMT signatures. Thus, targeting critical orchestrators at the convergence of several EMT pathways, such as the transcription pathways NF-kappaB, AKT/mTOR axis, MAPK, beta-catenin, PKC and the AP-1/SMAD factors provide a realistic strategy to control EMT and the progression of human epithelial cancers. Several inhibitors targeting these signaling platforms are already tested in preclinical and clinical oncology. In addition, upstream EMT signaling pathways induced by receptor and nonreceptor tyrosine kinases (e.g. EGF-R, IGF-R, VEGF-R, integrins/FAK, Src) and G-protein-coupled receptors (GPCR) constitute practical options under preclinical research, clinical trials or are currently used in the clinic for cancer treatment: e.g. small molecule inhibitors (Iressa: targeting selectively the EGF-R; CP-751,871, AMG479, NVP-AEW541, BMS-536924, PQIP, AG1024: IGF-R; AZD2171, ZD6474: VEGF-R; AZD0530, BMS-354825, SKI606: Src; BIM-46174: GPCR; rapamycin, CCI-779, RAD-001: mTOR) and humanized function blocking antibodies (Herceptin: ErbB2; Avastin: VEGF-A; Erbitux: EGF-R; Abegrin: alphavbeta3 integrins). We can assume that silencing RNA and adenovirus-based gene transfer of therapeutic miR and dominant interferring expression vectors targeting EMT pathways and signaling elements will bring additional ways for the treatment of epithelial cancers. Identification of the factors that initiate, modulate and effectuate EMT signatures and their underlying upstream oncogenic pathways should provide the basis of more efficient strategies to fight cancer progression as well as genetic and epigenetic forms of drug resistance. This goal can be accomplished using global screening of human clinical tumors by EMT-associated cDNA, proteome, miRome, and tissue arrays.

MetMAb, the one-armed 5D5 anti-c-Met antibody, inhibits orthotopic pancreatic tumor growth and improves survival

The hepatocyte growth factor (HGF) and its receptor, c-Met, have been implicated in driving proliferation, invasion, and poor prognosis in pancreatic cancer. Here, we investigated the expression of HGF and c-Met in primary pancreatic cancers and described in vitro and in vivo models in which MetMAb, a monovalent antibody against c-Met, was evaluated. First, expression of HGF and MET mRNA was analyzed in 59 primary pancreatic cancers and 51 normal samples, showing that both factors are highly expressed in pancreatic cancer. We next examined HGF responsiveness in pancreatic cancer lines to select lines that proliferate in response to HGF. Based on these studies, two lines were selected for further in vivo model development: BxPC-3 (c-Met(+), HGF(-)) and KP4 (c-Met(+), HGF(+)) cells. As BxPC-3 cells are responsive to exogenous HGF, s.c. tumor xenografts were grown in a paracrine manner with purified human HGF provided by osmotic pumps, wherein MetMAb treatment significantly inhibited tumor growth. KP4 cells are autocrine for HGF and c-Met, and MetMAb strongly inhibited s.c. tumor growth. To better model pancreatic cancer and to enable long-term survival studies, an orthotopic model of KP4 was established. MetMAb significantly inhibited orthotopic KP4 tumor growth in 4-week studies monitored by ultrasound and also improved survival in 90-day studies. MetMAb significantly reduced c-Met phosphorylation in orthotopic KP4 tumors with a concomitant decrease in Ki-67 staining. These data suggest that the HGF/c-Met axis plays an important role in the progression of pancreatic cancer and that targeting c-Met therein may have therapeutic value.

Myxoma virus is oncolytic for human pancreatic adenocarcinoma cells

BACKGROUND

Viral oncolytic therapy, which seeks to exploit the use of live viruses to treat cancer, has shown promise in the treatment of cancers resistant to conventional anticancer therapies. Among the most difficult to treat cancers is advanced pancreatic adenocarcinoma. Our study investigates the ability of a novel oncolytic agent, myxoma virus, to infect, productively replicate in, and kill human pancreatic cancer cells in vitro.

METHODS

The myxoma virus vMyxgfp was tested against a panel of human pancreatic adenocarcinoma cell lines. Infectivity, viral proliferation, and tumor cell kill were assessed.

RESULTS

Infection of tumor cells was assessed by expression of the marker gene enhanced green fluorescent protein (e-GFP). vMyxgfp had the ability to infect all pancreatic cancer cell lines tested. Killing of tumor cells varied among the 6 cell lines tested, ranging from >90% cell kill at 7 days for the most sensitive Panc-1 cells, to 39% in the most resistant cell line Capan-2. Sensitivity correlated to replication of virus, and was found to maximally exhibit a four-log increase in foci-forming units for the most sensitive Panc-1 cells within 72 h.

CONCLUSION

Our study demonstrates for the first time the ability of the myxoma virus to productively infect, replicate in, and lyse human pancreatic adenocarcinoma cells in vitro. These data encourage further investigation of this virus, which is pathogenic only in rabbits, for treatment of this nearly uniformly fatal cancer.

Radiation Enhances Adenoviral Gene Therapy in Pancreatic Cancer via Activation of Cytomegalovirus Promoter and Increased Adenovirus Uptake

Purpose: Adenovirus-mediated gene therapy combined with radiation is expected to be a new approach to treat pancreatic cancer. However, there are no reports of definitive effects of radiation on adenovirus-mediated gene therapies. In the present study, we investigated the effect of radiation on the transduction efficiency of an adenovirus-based gene therapy.

Experimental Design: We used adenovirus expressing NK4 (Ad-NK4), an antagonist for hepatocyte growth factor, as a representative gene therapy. Pancreatic cancer cells preinfected with Ad-NK4 were irradiated, and NK4 levels in culture media of these cells were measured. We investigated cytomegalovirus (CMV) promoter activity and uptake of adenovirus in these cells. To examine the effect of radiation in vivo, Ad-NK4 was given to irradiated subcutaneous tumors in nude mice, and NK4 levels in tumors were measured.

Results: NK4 levels in culture media of irradiated cells were 4.5-fold (P &lt; 0.01) higher than those of nonirradiated cells. Radiation enhanced activation of the CMV promoter and adenovirus uptake (P &lt; 0.01), leading to increased levels of NK4. We found that activation of p38 mitogen-activated protein kinase and up-regulation of dynamin 2 may be involved in the radiation-induced activation of the CMV promoter and adenovirus uptake, respectively. NK4 levels in irradiated tumors were 5.8-fold (P = 0.017) higher than those in nonirradiated tumors.

Conclusions: The present findings suggest that radiation significantly improves the efficiency of adenovirus-mediated gene transfer in pancreatic cancer and probably contributes to decreasing the dose of adenovirus required for gene transfer and controlling side effects of adenovirus infection in nonirradiated normal tissue.

Suppression of human colon tumor growth by adenoviral vector-mediated NK4 expression in an athymic mouse model

AIM: To investigate the suppressive effects of adenoviral vector-mediated expression of NK4, an antagonist of hepatocyte growth factor (HGF), on human colon cancer in an athymic mouse model to explore the possibility of applying NK4 to cancer gene therapy.

METHODS: A human colon tumor model was developed by subcutaneous implantation of tumor tissue formed by LS174T cells grown in athymic mice. Fifteen tumor-bearing mice were randomized into three groups (n = 5 in each group) at d 3 after tumor implantation and mice were injected intratumorally with phosphate-buffered saline (PBS) or with recombinant adenovirus expressing β-galactosidase (Ad-LacZ) or NK4 (rvAdCMV/NK4) at a 6-d interval for total 5 injections in each mouse. Tumor sizes were measured during treatment to draw a tumor growth curve. At d 26 after the first treatment, all animals were sacrificed and the tumors were removed to immunohistochemically examine proliferating cell nuclear antigen (PCNA), microvessel density (represented by CD31), and apoptotic cells. In a separate experiment, 15 additional athymic mice were employed to develop a tumor metastasis model by intraperitoneal injection (ip) of LS174T cells. These mice were randomized into 3 groups (n = 5 in each group) at d 1 after injection and were treated by ip injection of PBS, or Ad-LacZ, or rvAdCMV/NK4 at a 6-d interval for total two injections in each mouse. All animals were sacrificed at d 14 and the numbers and weights of disseminated tumors within the abdominal cavity were measured.

RESULTS: Growth of human colon tumors were significantly suppressed in the athymic mice treated with rvAdCMV/NK4 (2537.4 ± 892.3 mm³) compared to those treated by either PBS (5175.2 ± 1228.6 mm³) or Ad-LacZ (5578.8 ± 1955.7 mm³) (P < 0.05). The tumor growth inhibition rate was as high as 51%. Immunohistochemical staining revealed a similar PCNA labeling index (75.1% ± 11.2% in PBS group vs 72.8% ± 7.6% in Ad-LacZ group vs 69.3% ± 9.4% in rvAdCMV/NK4 group) in all groups, but significantly lower microvessel density (10.7 ± 2.4 in rvAdCMV/NK4 group vs 25.6 ± 3.8 in PBS group or 21.3 ± 3.5 in Ad-LacZ group, P < 0.05), and a markedly higher apoptotic index (7.3% ± 2.4% in rvAdCMV/NK4 group vs 2.6 ± 1.1% in PBS group or 2.1% ± 1.5% in Ad-LacZ group, P < 0.05) in the rvAdCMV/NK4 group compared to the two control groups. In the tumor metastasis model, the number and weight of disseminated tumors of mice treated with rvAdCMV/NK4 were much lower than those of the control groups (tumor number: 6.2 ± 3.3 in rvAdCMV/NK4 group vs 22.9 ± 7.6 in PBS group or 19.8 ± 8.5 in Ad-LacZ group, P < 0.05; tumor weight: 324 ± 176 mg in rvAdCMV/NK4 group vs 962 ± 382 mg in PBS group or 1116 ± 484 mg in Ad-LacZ group, P < 0.05).

CONCLUSION: The recombinant adenovirus, rvAdCMV/NK4, can attenuate the growth of colon cancer in vivo, probably by suppressing angiogenesis and inducing tumor cell apoptosis, but not by direct suppression of tumor cell proliferation. Moreover, rvAdCMV/NK4 may inhibit peritoneal dissemination of colon cancer cells in a murine tumor metastasis model. These findings indicate that NK4 gene transfer may be an effective tool for the treatment of colon cancer.

Pancreatic cancer: pathogenesis, prevention and treatment

Pancreatic cancer is the fourth leading cause of cancer death in the United States with a very low survival rate of 5 years. To better design new preventive and/or therapeutic strategies for the fight against pancreatic cancer, the knowledge of the pathogenesis of pancreatic cancer at the molecular level is very important. It has been known that the development and the progression of pancreatic cancer are caused by the activation of oncogenes, the inactivation of tumor suppressor genes, and the deregulation of many signaling pathways among which the EGFR, Akt, and NF-kappaB pathways appear to be most relevant. Therefore, the strategies targeting EGFR, Akt, NF-kappaB, and their downstream signaling could be promising for the prevention and/or treatment of pancreatic cancer. In this brief review, we will summarize the current knowledge regarding the pathogenesis, prevention, and treatment of pancreatic cancer.