The potential for gene therapy in pancreatic cancer

Progress in gene therapy for prostate cancer

Gene therapy has held promise to correct various disease processes. Prostate cancer represents the second leading cause of cancer death in American men. A number of clinical trials involving gene therapy for the treatment of prostate cancer have been reported. The ability to efficiently transduce tumors with effective levels of therapeutic genes has been identified as a fundamental barrier to effective cancer gene therapy. The approach utilizing gene therapy in prostate cancer patients at our institution attempts to address this deficiency. The sodium-iodide symporter (NIS) is responsible for the ability of the thyroid gland to transport and concentrate iodide. The characteristics of the NIS gene suggest that it could represent an ideal therapeutic gene for cancer therapy. Published results from Mayo Clinic researchers have indicated several important successes with the use of the NIS gene and prostate gene therapy. Studies have demonstrated that transfer of the human NIS gene into prostate cancer using adenovirus vectors in vitro and in vivo results in efficient uptake of radioactive iodine and significant tumor growth delay with prolongation of survival. Preclinical successes have culminated in the opening of a phase I trial for patients with advanced prostate disease which is currently accruing patients. Further study will reveal the clinical promise of NIS gene therapy in the treatment of prostate as well as other malignancies.

A probasin promoter, conditionally replicating adenovirus that expresses the sodium iodide symporter (NIS) for radiovirotherapy of prostate cancer

The sodium iodide symporter (NIS) directs the uptake and concentration of iodide in thyroid cells. We have extended the use of NIS-mediated radioiodine therapy to other types of cancer, we transferred and expressed the NIS gene into prostate, colon and breast cancer cells using adenoviral vectors. To improve vector efficiency we have developed a conditionally replicating adenovirus (CRAd) in which the E1a gene is driven by the prostate-specific promoter, Probasin and the cassette RSV promoter human NIScDNA-bGH polyA replaces the E3 region (CRAd Ad5PB_RSV-NIS). In vitro infection of the prostate cancer cell line LnCaP resulted in virus replication, cytolysis and release of infective viral particles. Conversely, the prostate cancer cell line PC-3 (androgen receptor negative) and the pancreatic cancer cell line Panc-1 were refractory to the viral cytopathic effect and did not support viral replication. Radioiodine uptake was readily measurable in LnCaP cells infected with Ad5PB_RSV-NIS 24 h post-infection, confirming NIS expression. In vivo, LnCaP tumor xenografts in nude-mice injected intratumorally with Ad5PB_RSV_NIS CRAd expressed NIS actively as evidenced by ⁹⁹Tc uptake and imaging. Administration of therapeutic ¹³¹I after virus injection significantly increased survival probability in mice carrying xenografted LnCaP tumors compared with virotherapy alone. These data indicate that Ad5PB_RSV_NIS replication is stringently restricted to androgen-positive prostate cancer cells and results in effective NIS expression and uptake of radioiodine. This construct may allow multimodal therapy, combining cytolytic virotherapy with radioiodine treatment, to be developed as a novel treatment for prostate cancer.

Construction of an MUC-1 promoter driven, conditionally replicating adenovirus that expresses the sodium iodide symporter for gene therapy of breast cancer

Introduction

The sodium iodide symporter (NIS) directs the uptake and concentration of iodide in thyroid cells. This in turn allows radioiodine imaging and therapy for thyroid cancer. To extend the use of NIS-mediated radioiodine therapy to other types of cancer, we successfully transferred and expressed the sodium-iodide symporter (NIS) gene in prostate, colon, and breast cancer cells both in vivo and in vitro by using non-replicating adenoviral vectors.

Methods

To improve virotherapy efficiency, we developed a conditionally replicating adenovirus (CRAd) in which the transcriptional cassette RSV promoter-human NIScDNA-bGH polyA was also inserted at the E3 region. The E1a gene is driven by the tumor-specific promoter MUC-1 in the CRAd Ad5AMUCH_RSV-NIS.

Results

In vitro infection of the MUC-1-positive breast cell line T47D resulted in virus replication, cytolysis, and release of infective viral particles. Conversely, the MUC-1-negative breast cancer cell line MDA-MB-231 was refractory to the viral cytopathic effect and did not support viral replication. The data indicate that Ad5AMUCH_RSV-NIS activity is stringently restricted to MUC-1-positive cancer cells. Radioiodine uptake was readily measurable in T47 cells infected with Ad5AMUCH_RSV-NIS 24 hours after infection, thus confirming NIS expression before viral-induced cell death.

Conclusions

This construct may allow multimodal therapy, combining virotherapy with radioiodine therapy to be developed as a novel treatment for breast and other MUC1-overexpressing cancers.

Suicide gene therapy with the yeast fusion gene cytosine deaminase/uracil phosphoribosyltransferase is not enough for pancreatic cancer

OBJECTIVES

Suicide gene therapy with FCY1 gene, encoding cytosine deaminase (CD), together with FUR1, encoding uracil phosphoribosyltransferase (UPRT), has been proposed for pancreatic cancer therapy in vivo. We ascertained whether gene therapy with FCY1-FUR1 is effective in killing pancreatic cancer cells after 5-fluorocytosine (5-FC) treatment.

METHODS

AsPC1, BxPC3, Capan1, MIA PaCa2, and Panc1 cell lines were transfected using 2 plasmid vectors expressing CD only (pRSV-CD) or the chimera CD-UPRT (pRSV-CD-UPRT). Control and pRSV-CD- or pRSV-CD-UPRT-transfected cell lines were treated with 0, 0.1, 0.5, 1, 5, and 10 mM of 5-FC for 1, 3, 6, 8, 10, and 13 days.

RESULTS

FCY1 alone did not confer sensitivity to 5-FC. The CD-UPRT-transfected BxPC3 and Panc1 were sensitive to very low 5-FC doses (0.1 mM). 5-Fluorocytosine-sensitive transfected cell lines rapidly converted 5-FC into 5-fluorouracil, whereas the 5-FC resistant cell lines had an impaired 5-FC conversion.

CONCLUSIONS

Suicide gene therapy with the FCY1 gene alone was ineffective in the treatment of pancreatic cancer in vitro. The pRSV-CD-UPRT construct conferred 5-FC sensitivity to some pancreatic cancer cell lines. Therefore, the application in vivo of suicide gene therapy with FCY1 alone or in combination with the FUR1 gene is probably destined to fail.

Current status of gene therapy for pancreatic cancer

Pancreatic adenocarcinoma remains a widespread and difficult disease to treat. Surgical resection offers the possibility of cure in a select few. However, most patients are not eligible, and conventional chemotherapy and radiation remain largely ineffective. Despite this, our understanding of the pathogenesis of the disease has advanced considerably over the past few decades. These findings provide the basis for the development of much needed new therapeutic modalities. Specifically, the application of new recombinant DNA technology and techniques to pancreatic cancer has yielded promising results. This paper reviews our current understanding of the molecular biology of pancreatic adenocarcinoma and its applications to the field of gene therapy.

Suicide gene therapy with HSV-TK in pancreatic cancer has no effect in vivo in a mouse model

AIM

To study in vivo whether pancreatic cancer tumour growth and metastasis can be modified by a gene construct with HSV-TK suicide gene and IL2 co-expression.

METHODS

Seventy-eight female SCID mice were i.p. inoculated with retrovirally transduced or control MIA PaCa 2, CAPAN-1 and PANC-1 cell lines. The animals were then randomly selected for saline or ganciclovir (GCV) treatment from the second week, for a total of two weeks.

RESULTS

Most inoculated mice developed tumour nodules and spleen metastases. The liver was colonized by control CAPAN-1 and MIA PaCa 2, but not by PANC-1. Tumours in transduced MIA PaCa 2 cell injected mice were smaller, and in transduced CAPAN-1 injected mice larger, than in control-inoculated mice. There were increased pancreatic and decreased spleen metastases from transduced CAPAN-1, and diminished liver involvement from transduced MIA PaCa 2. No differences were found between mice inoculated with transduced and control PANC-1 cell lines. GCV treatment had no effect on tumour's size or metastases.

CONCLUSIONS

The HSV-TK suicide gene does not confer GCV sensitivity to pancreatic cancer in this in vivo model. Different pancreatic cancer cell lines cause different growth and metastasis patterns after inoculation in SCID mice, possibly because of variations in their inherent characteristics. The different effects of our vector on cell growth and metastasis may be attributable to the effects of the immunostimulatory cytokine IL2.

Adenovirus-mediated gene transfer in the treatment of pancreatic cancer

INTRODUCTION

Suicide gene therapy is a new experimental form of cancer chemotherapy that is currently being evaluated in human trials.

AIM

To evaluate the killing effects of the cytosine deaminase (CD) gene mediated by an adenovirus vector on human pancreatic carcinoma in vitro and in vivo.

METHODOLOGY

The CD gene was cloned into pAdTrack-CMV-CD, pAdTrack-CMV-CD, and pAdEasy-1, which underwent recombination in bacteria BJ5183. The newly recombinant Ad-CD containing green fluorescent protein was propagated in 293 cells and purified by cesium chloride gradient centrifugation. The human pancreatic carcinoma cell line PaTu8988/SW1990 was infected with this virus, and then 5-fluorocytosine (5-FC) was added; XTT assay was used to estimate relative numbers of viable cells. An in vivo model of pancreatic cancer was established by injecting 1.0 x 10(7) PaTu8988/SW1990 cells subcutaneously in Balb/c nude mice. When tumors were palpable, Ad-CD was injected into each tumor, and 5-FC was administered. The positive clones were selected by endonuclease digestion of the combinations, and the concentration of viral liquids containing the CD gene was 2 x 10(11) pfu/mL.

RESULTS

It was found that significant cytotoxic activities were possessed by 5-FC for CD gene-transduced PaTu8988/SW1990 cells, but there was little effect on the nontransduced pancreatic carcinoma cells. The antitumor effect was observed in PaTu8988/SW1990 xenografts from nude mice with in situ CD gene transduction.

CONCLUSION

These results indicate that the CD gene mediated by adenovirus has a high level of infectivity and is efficient for gene therapy for pancreatic carcinoma.

Current approaches to novel therapeutics in pancreatic cancer

Pancreatic cancer is one of the most refractory neoplasms to medical treatment. Until now there has been only modest improvement in the treatment of this disease. Standards of care for combined-modality treatment of resectable as well as locally advanced, unresectable disease have not been uniformly accepted to date because of an equivocal or conflicting data. The inception of gemcitabine introduced the new era in the management of metastatic pancreatic cancer, however, new therapeutic approaches still need to be defined. The article discusses the current knowledge of the biology of this lethal disease, its impact on treatment options, and explores novel therapeutic modalities that are likely to improve outcomes and survival for patients in the future.

Expression of survivin, a novel inhibitor of apoptosis and cell cycle regulatory protein, in pancreatic adenocarcinoma

Survivin is unique for its expression in human malignancies but not in normal adult cells. It has been implicated in sensitisation to chemotherapy and as a prognostic marker in several common cancers. Immunohistochemistry for Survivin, P53 and BCL-2 expression as well as cell proliferative index (Ki-67) and apoptosis index (TUNEL) was conducted on 52 pancreatic and 12 ampullary adenocarcinomas. Survivin was detected in the cytoplasm of carcinoma cells in 46 (88%) of pancreatic tumours. P53 and BCL-2 were detected in 54% and 12% of pancreatic tumours, respectively. Proliferative index was 26.2+/-10.5% and apoptosis index was 1.38+/-0.69%. Prevalence of Survivin expression was significantly higher in P53-positive than in P53-negative cases (P=0.05) but was not associated with BCL-2 expression. Incrementally higher weighted scores of Survivin expression were associated with increased proliferative index (P=0.001). Furthermore, there was linear correlation between increased proliferative index and higher apoptosis index (P<0.001). Surprisingly, higher scores of Survivin expression were associated with increased apoptosis index (P=0.007). Survival characteristics were not influenced by Survivin, P53 or BCL-2 expression, apoptosis index or proliferative index. Ampullary carcinoma showed Survivin expression in 83% of cases. However, unlike pancreatic carcinoma, there was no correlation between Survivin and P53 expression or proliferative index. In conclusion, Survivin is expressed in the majority of pancreatic adenocarcinomas and correlates with both cellular proliferation and apoptosis. Molecular manipulation of Survivin expression may enhance chemotherapy and radiation therapy for pancreatic cancer.

Adenovirus-mediated wt-p16 reintroduction induces cell cycle arrest or apoptosis in pancreatic cancer

Pancreatic cancer has long carried poor prognosis. The development of new therapeutic approaches is particularly urgent. Inactivation of the tumor-suppressor gene p16(INK4a/CDKN2), a specific inhibitor of the cyclin-dependent kinases CDK4 and CDK6, is the most common genetic alteration in human pancreatic cancer, making it an ideal target for gene replacement. Here we transfected tumor cells using a recombinant adenovirus containing the wt-p16 cDNA (Ad5RSV-p16). The overexpression of p16 decreased cell proliferation in all four human pancreatic tumor cell lines (NP-9, NP-18, NP-29, and NP-31). However, G1 arrest and senescence were observed in only three. In contrast, the fourth (NP-18) showed a significant increase in apoptosis. This differential behavior may be related to the differences found in the expression level of E2F-1. Experiments on subcutaneous pancreatic xenografts demonstrated the effectiveness of p16 in the inhibition of pancreatic tumor growth in vivo. Taken together, our results indicate that approaches involving p16 replacement are promising in pancreatic cancer treatment.

Improved gene transfer efficiency to primary and established human pancreatic carcinoma target cells via epidermal growth factor receptor and integrin-targeted adenoviral vectors

In this study we analyzed two ways of retargeting of Ad-vectors to human pancreatic carcinoma with the aim of enhancing the gene transfer efficiency. First, we analyzed the expression of the epidermal growth factor receptor (EGFR) on primary, as well as established pancreatic carcinoma cells by flow cytometry which revealed high expression levels of EGFR on the surface of these cells. We showed that EGFR-retargeted entry pathway using a bispecific fusion protein formed by a recombinant soluble form of truncated Coxsackie and Adenovirus Receptor (sCAR) genetically fused with human EGF (sCAR-EGF) redirects them to the EGFR leading to an enhanced gene transfer efficiency to pancreatic carcinoma cells. Since flow cytometry revealed absence of CAR expression, but the presence of at least one of both alphav integrins on the pancreatic carcinoma cells, a second way of targeting was investigated using a genetically modified Ad vector which has an RGD (Arg-Gly-Asp)-containing peptide inserted into the HI-loop of the fiber knob. This RGD targeted Ad (AdlucRGD) revealed efficient CAR-independent infection by allowing binding to cellular integrins resulting in a dramatic enhancement of gene transfer. These findings have direct relevance for Ad-vector based gene therapy strategies for pancreatic carcinoma.

Adenovirus-mediated transfer of p53 and p16(INK4a) results in pancreatic cancer regression in vitro and in vivo

Pancreatic cancer has a very poor prognosis. Current chemotherapy and radiotherapy regimens are only moderately successful. The tumour suppressor genes p53 and p16(INK4a)encode cell cycle regulatory proteins that are important candidates for gene replacement therapy. Over 80% of pancreatic adenocarcinoma cases lack detectable p16 protein while over 60% contain mutated p53 protein. We used replication-deficient recombinant adenoviruses to reintroduce wild-type p16 and p53 into pancreatic cancer cells in vitro and into subcutaneous pancreatic tumours in an animal model to determine the effect on tumour growth. Significant growth inhibition was observed in all five human pancreatic cell lines with these viruses (P < 0.002) compared with similar control viruses expressing either luciferase or beta-galactosidase. G1 arrest was observed in all cell lines 72 h after infection with Adp16. Infection with Adp53 caused significant levels of apoptosis (P < 0.004). Apoptosis was also observed to a lesser degree (P < 0.03) with the Adp16 vector. Subcutaneous pancreatic tumours, generated in nu-nu mice demonstrated significant growth suppression following injection of Adp53, Adp16 and a combination of both Adp53 and Adp16 (P < 0.0001). These results show that transfer of wild-type p53 and p16 produces significant growth suppression of pancreatic cancer in vitro and in vivo.

Gene therapy for pancreatic cancer--current and prospective strategies

Pancreatic ductal adenocarcinoma is one of the most common causes of cancer death in the developed world. Long-term survival is currently only achieved through surgical resection. Most patients have locally advanced or metastatic disease at the time of diagnosis and are therefore not amenable to resection, whilst chemotherapy and radiotherapy are by and large ineffective. Gene therapy offers an alternative to current adjuvant strategies. With approximately two-thirds of all gene therapy trials worldwide directed at cancer, the gene therapy approaches that are currently being explored for pancreatic cancer are specifically examined. Gene delivery systems, genetic targets, and combined gene delivery with chemotherapy are discussed in the context of pancreatic cancer treatment.