Adenovirus-mediated gene transfer in the treatment of pancreatic cancer

Effects of HSV-TK+GFP/GCV suicide gene therapy system on mouse pancreatic cancer cells

AIM: To study in vitro therapeutic effect on mouse pancreatic cancer, as well as the bystander effect with HSV-TK suicide gene in combination with prodrug GCV.

METHODS: HSV-TK and GFP were inserted into pcDNA3.1 (+) to construct pcDNA3.1+/HSV-TK+GFP, and pcDNA3.1+/HSV-TK+GFP was transferred into mouse pancreatic cancer cell MPC by Lipofectin. We then added GCV to these gene-modified cells and studied the sensitivity of the cells to GCV as well as the bystander effect.

RESULTS: The gene modified pancreatic cancer cells MPC/HSV-TK+GFP were successfully developed. In vitro experiments showed that when the MPC/HSV-TK+GFP cells accounted for 10% of hybrid cells, the low concentration (20 mg/L) of GCV was about 50% of tumor cell killing. In vivo results showed that the low concentration of GCV killed the cells. And tumor growth of the mouse model was inhibited.

CONCLUSION: Our data demonstrate MPC/HSV-TK+GFP cells are sensitive to the treatment of GCV compared with unmodified tumor cells, and remarkable bystander effect is seen.

Molecular chemotherapy of pancreatic cancer using novel mutant bacterial cytosine deaminase gene

The combination of molecular chemotherapy with radiation therapy has the potential to become a powerful approach for treatment of pancreatic cancer. We have developed an adenoviral vector (AdbCD-D314A) encoding a mutant bacterial cytosine deaminase (bCD) gene, which converts the prodrug 5-fluorocytosine (5-FC) into the active drug 5-fluorouracil. The aim of this study was to investigate AdbCD-D314A/5-FC-mediated cytotoxicity in vitro and therapeutic efficacy in vivo alone and in combination with radiation against human pancreatic cancer cells and xenografts. AdbCD-D314A/5-FC-mediated cytotoxicity alone and in combination with radiation was analyzed using crystal violet inclusion and clonogenic survival assays. CD enzyme activity was determined by measuring conversion of [3H]5-FC to [3H]5-fluorouracil after adenoviral infection of pancreatic cancer cells in vitro and pancreatic tumor xenografts by TLC. S.c. pancreatic tumor xenografts were used to evaluate the therapeutic efficacy of AdbCD-D314A/5-FC molecular chemotherapy in combination with radiation therapy. AdbCD-D314A infection resulted in increased 5-FC-mediated pancreatic cancer cell killing that correlated with significantly enhanced CD enzyme activity compared with AdbCDwt encoding wild-type of bCD. Animal studies showed significant inhibition of growth of human pancreatic tumors treated with AdbCD-D314A/5-FC in comparison with AdbCDwt/5-FC. Also, a significantly greater inhibition of growth of Panc2.03 and MIA PaCA-2 tumor xenografts was produced by the combination of AdbCD-D314A/5-FC with radiation compared with either agent alone. The results indicate that the combination of AdbCD-D314A/5-FC molecular chemotherapy with radiation therapy significantly enhanced cytotoxicity of pancreatic cancer cells in vitro and increased therapeutic efficacy against human pancreatic tumor xenografts.

Selective tropism of liver stem cells to hepatocellular carcinoma in vivo

AIM: To investigate the selective tropism of liver stem cells to hepatocellular carcinoma (HCC) in an animal model and its feasibility as a vector to deliver therapeutic genes for targeted therapy of HCC.

METHODS: WB-F344, a kind of rat liver stem cell, was infected with recombinant virus to establish a cell line with stable, high-level expressing enhanced green fluorescent protein (EGFP). An animal model of HCC in Wistar rats was established by implanting HCC cells (CBRH7919) combined with an immunosuppressive drug. EGFP labeled liver stem cells were injected into caudal veins of the animals and distribution was observed at different time points after injection. SDF-1 and c-kit expression in non-tumor liver and tumor tissue were analysed by immunohistochemistry for the relationshiop between the expression and migration of liver stem cells. Furthermore, hepatic stem cells were injected via the portal vein, hepatic artery, caudal vein, or directly into the pericancerous liver tissue, respectively, and effects on migration, localization, and proliferation of the hepatic stem cells within the tumor tissue were observed and analyzed.

RESULTS: Recombinant adenovirus could deliver the EGFP gene to hepatic stem cells. A new stem cell line, named WB-EGFP, was established that stably expressed EGFP. WB-EGFP cells still showed selective tropism towards HCC and EGFP expression was stable in vivo. According to immunohistochemistry results, SDF-1 may not be related to the mechanisms of tropism of hepatic stem cells. Different application sites affected the distribution of liver stem cells. Injection via the portal vein was superior with regard to selective migration, localization, and proliferation of the hepatic stem cells within the tumor tissue.

CONCLUSION: Liver stem cells have the biological behavior of selective migration to HCC in vivo and they could localize and proliferate within HCC tissue stably expressing the target gene. Liver stem cells are a potential tool for a targeted gene therapy of HCC.

Effective antitumoral immune responses are not induced by cytosine deaminase suicide gene transfer in a syngeneic rat pancreatic carcinoma model

BACKGROUND

Experimental gene transfer can make tumors more immunogenic, leading to local regression and inducing immunological memory sufficient to permit resistance to a tumor rechallenge. However, this rarely had any significant impact on large established tumors.

METHODS

To analyze potential immunological effects, we used weakly immunogenic pancreatic carcinomas in syngeneic, immunocompetent Lewis rats and performed in situ adenoviral mediated cytosine deaminase (CD) gene transfer followed by administration of the prodrug, 5-fluorocytosine (5FC). In order to reflect the clinical situation, such treated tumors were surgically resected and animals were rechallenged with parental DSL6A pancreatic tumor cells. Tumor growth and cytotoxic activity of immune cells were determined.

RESULTS

CD/5FC treatment of the DSL6A cells revealed significant induction of apoptosis in vitro and slowed down tumor progression in syngeneic hosts. Furthermore, we observed neither significant change in tumor growth nor protective immunity in the rechallenged animals. Analysis of T lymphocytes showed no specific cytotoxic activity against DSL6A cells. There was only a trend towards a minor NK cell activation.

CONCLUSIONS

Albeit the present study failed to induce protective antitumor immunity, the initial finding of reduced tumor growth argues for the development of multimodal therapeutic options to overcome negative impacts of advanced malignant disease or chemotherapy-related anergy and immunosuppression.

Antisense Smo under the control of the PTCH1 promoter delivered by an adenoviral vector inhibits the growth of human pancreatic cancer

Hedgehog (Hh) signaling pathway is crucial in growth and patterning during embryonic development. Recent data have shown an association of its activation with cancer formation and maintenance. A ligand-dependent activation, where Hh components (SHH, PTCH1, Smo and GLi1) are aberrantly expressed with PTCH1 being a negative feedback regulator, is a newly identified mechanism for pancreatic carcinogenesis. In this study, we developed a cell-specific cytotoxic model for the treatment of human pancreatic cancer (HPC) in which expression of antisense Smo (SAS) was under the control of the PTCH1 promoter (ptch/p) delivered by an adenoviral vector (Ad-ptch/p-SAS). We observed that the cell-specific cytotoxicity in HPC cells depended on the expressions of inherent PTCH1, Smo and GLi1 in the target cells in which the Hh pathway was presumed to be activated. Fluorescence-activated cell sorting analysis indicated that the cell death was apoptosis. Western blot showed that Smo protein in the infected cells significantly decreased. Furthermore, an in vivo experiment demonstrated that such Hh activity-cell-specific cytotoxicity was achieved by daily intratumoral injection of Ad-ptch/p-SAS (10(9) plaque-forming unit) for 5 days. Our study suggests that targeting at the Hh signaling pathway may be an effective novel gene therapeutic strategy alone or in combination with other agents for the treatment of pancreatic cancer.

Adenoviral-mediated efficiency expression of enhanced green fluorescence protein in adult liver stem cells of rats

AIM: To investigate the feasibility of adenoviral-mediated exogenous gene expression in adult liver stem cells of rats and to establish a cell line that stably and efficiently express enhanced green fluorescence protein (EGFP).

METHODS: A pAd-CMV-EGFP vector under the control of CMV promoter was constructed by homologous recombination in E.coilBJ 5 183, and the recombinant virus was Packaged in HEK 293 cell line. Hepatic adult stem cells cultured in vitro were infected with recombinant adenovirus. Expression of EGFP was observed by fluorescent microscopy and infection efficiency was analyzed. Adult liver stem cells were further cultured to estabilish a cell line that stably and efficiently expressed EGFP through cloning culture and the biological characteristics of the cell line were observed and analyzed by fluorescence microscopy, immunocytochemistry and differentiation-inducing experiment.

RESULTS: Adenovirus vector of pAd-CMV-EGFP was constructed and high titer recombinant virus were produced successfully. EGFP, mediated by adenovirus, could be transfected into hepatic adult stem cells with a high efficiency (about 40-70%). After cloning culture, WB-EGFP cell line was established, and it could stably express EGFP in 8-9 generations. Furthermore, biological characteristics such as marker of stem cells, proliferation speed and differentiation capability had not been affected.

CONCLUSION: Target gene can be efficiently transfected into hepatic adult stem cells through adeno-vector system. EGFP can be stably and long-term expressed in transfected cells and their offspring. It can serve as a tracker in the research of stem cells.