In vivo transfer of bacterial marker genes results in differing levels of gene expression and tumor progression in immunocompetent and immunodeficient mice

Identification of a cancer stem-like population in the Lewis lung cancer cell line

OBJECTIVE

Although various human cancer stem cells (CSCs) have been defined, their applications are restricted to immunocompromised models. Developing a novel CSC model which could be used in immunocompetent or transgenic mice is essential for further understanding of the biomolecular characteristics of tumor stem cells. Therefore, in this study, we analyzed murine lung cancer cells for the presence of CSCs.

METHODS

Side population (SP) cells were isolated by fluorescence activated cell sorting, followed by serum-free medium (SFM) culture, using Lewis lung carcinoma cell (LLC) line. The self-renewal, differentiated progeny, chemosensitivity, and tumorigenic properties in SP and non-SP cells were investigated through in vitro culture and in vivo serial transplantation. Differential expression profiles of stem cell markers were examined by RT-PCR.

RESULTS

The SP cell fraction comprised 1.1% of the total LLC population. SP cells were available to grow in SFM, and had significantly enhanced capacity for cell proliferation and colony formation. They were also more resistant to cisplatin in comparison to non-SP cells, and displayed increased tumorigenic ability. Moreover, SP cells showed higher mRNA expression of Oct-4, ABCG2, and CD44.

CONCLUSION

We identified SP cells from a murine lung carcinoma, which possess well-known characteristics of CSCs. Our study established a useful model that should allow investigation of the biological features and pharmacosensitivity of lung CSCs, both in vitro and in syngeneic immunocompetent or transgenic/knockout mice.

Gene Therapy for Malignant Pleural Mesothelioma

Gene therapy for mesothelioma is currently in its adolescence. The expansion of knowledge regarding molecular aspects of mesothelioma carcinogenesis has facilitated the development of promising gene therapy modalities that target specific oncoproteins and mutant tumor suppressor genes. Although implementation of any of these gene therapy approaches as part of standard medical care for patients who have mesothelioma remains years in the future, the field is finally progressing toward more definitive phase II/III efficacy studies. Unfortunately, the marginal benefits garnered from standard anticancer treatments in mesothelioma argue strongly for continued participation in clinical studies of various experimental approaches, particularly gene therapy. These trials serve multiple purposes: to establish safety, determine proper dosing, evaluate for efficacy, and, in an iterative fashion, guide future avenues of laboratory investigation.

Intratumoral Poly-N-Acetyl Glucosamine-Based Polymer Matrix Provokes a Prolonged Local Inflammatory Response That, When Combined with IL-2, Induces Regression of Malignant Mesothelioma in a Murine Model

The authors have previously shown that cytokines delivered directly into malignant mesothelioma (MM) tumors can retard tumor growth and mediate tumor regression under certain conditions. In this report the authors compared the efficacy of serial intratumoral injections of three cytokines, GM-CSF, IL-12, and IL-2, to their sustained release using a single injection in a poly-N-acetyl glucosamine gel. IL-2 combined with the polymer gel gave optimal antitumor results when MM tumors were accessible as either subcutaneous deposits or as masses spread throughout the peritoneal cavity. The gel acted not only as a slow-release cytokine depot but also as a trigger for inflammation and recruited several immune cell types to the gel/tumor interface; when combined with IL-2 (but not with GM-CSF or IL-12), it acted as a selective reservoir for infiltrating CD8+ T cells. Hence, the IL-2/gel may provide a microenvironment that allows intratumoral T cells to proliferate and retain their cytolytic functions as they encounter their cognate antigens expressed by tumor cells.

Intraperitoneal gene delivery mediated by a novel cationic liposome in a peritoneal disseminated ovarian cancer model

We have previously synthesized a new cationic liposome that displays high efficiency and low toxicity, 3 beta[l-ornithinamide-carbamoyl] cholesterol (O-Chol), using solid-phase synthesis. In this study, O-Chol was applied to in vitro and in vivo models of ovarian cancer. Intraperitoneal gene delivery for peritoneal disseminated ovarian cancer in nude mice was achieved using a stable chloramphenicol acetyl transferase (CAT)-expressing ovarian cancer cell line (OV-CA-2774/CAT), which allowed us to quantify the exact tumor burden of organs. When luciferase and beta-galactosidase genes were used as reporter genes, O-Chol showed better efficiency than other commercial transfection reagents such as lipofectin, lipofectAMINE, DC-Chol, and FuGENE 6, both in vitro and in vivo. Moreover, the transfection efficiency of this new cationic lipid reagent remained high in serum-containing medium and under serum-free conditions. Furthermore, in vivo transfection with O-Chol showed high levels of gene expression specific to peritoneal tumor cells. Consequently, the O-Chol:DNA lipoplex appears to offer potential advantages over other commercial transfection reagents because of (1) its higher level of gene expression in vitro and in vivo; (2) its reduced susceptibility to serum inhibition; and (3) its highly selective transfection into tumor cells. These results suggest that the O-Chol:DNA lipoplex is a promising tool in gene therapy for patients with peritoneal disseminated ovarian cancer.

Induction of stable prenatal tolerance to beta-galactosidase by in utero gene transfer into preimmune sheep fetuses

The successful transduction of hematopoietic stem cells and long-term (28 months) transgene expression within the hematopoietic system following the direct injection of high-titer retroviral vectors into preimmune fetal sheep was previously demonstrated. The present studies extended these analyses for 40 months postinjection and evaluated whether the longevity of transgene expression in this model system was the result of induction of prenatal tolerance to the transgene product. The intraperitoneal injection of retroviral vectors into preimmune sheep fetuses transduces thymic epithelial cells thought to present antigen and thus define self during immune system development. To directly demonstrate induction of tolerance, postnatal sheep were boosted with purified beta-galactosidase and showed that the peripheral blood lymphocytes from in utero-transduced sheep exhibited significantly lower stimulation indices to transduced autologous cells than did control animals and that the in utero-transduced sheep had a reduced ability to mount an antibody response to the vector-encoded beta-galactosidase protein compared with control sheep. Collectively, our results provide evidence that the direct injection of retroviral vectors into preimmune sheep fetuses induces cellular and humoral tolerance to the vector/transgene products and provide an explanation for the duration and stability of transgene expression seen in this model. These results also suggest that even relatively low levels of gene transfer in utero may render the recipient tolerant to the exogenous gene and thus potentially permit the successful postnatal treatment of the recipient. (Blood. 2001;97:3417-3423)

Preclinical and therapeutic utility of HVJ liposomes as a gene transfer vector for hepatocellular carcinoma using herpes simplex virus thymidine kinase

Although gene therapy has been suggested to be a novel strategy to treat hepatocellular carcinoma (HCC), no study showing the clinical feasibility of vectors to treat HCC has been reported. In this preclinical study, we show evidence indicating that hemagglutinating virus of Japan (HVJ) liposomes are a feasible vector to treat HCC in a clinical setting using ganciclovir (GCV) and herpes simplex virus thymidine kinase (HSV-tk), which is driven by the cytomegalovirus immediate early enhancer/promoter (plasmid pcDNA3/HSV-tk). In in vitro experiments, almost complete tumor cell regression was achieved with the optimal GCV concentration (100 microg/mL) and more than 1/3 regression was seen even with a 20% transduction ratio using HuH7 HCC cells stably transformed by HSV-tk. HVJ liposomes showed a 19.7% (mean) transduction rate of the lacZ gene in a relatively large mass of more than 300 mm3 in vivo, which is a clinically detectable size, implanted into SCID mice. Moreover, a single HSV-tk injection of HVJ liposomes followed by GCV treatment inhibited tumor growth at least within a week, and repeat administration was more effective. Furthermore, subcutaneous injection of an HVJ liposomes vehicle induced no apparent inflammatory response in C3H/HeN mice, whereas lacZ gene transfection resulted in inflammatory pathology, suggesting a lower immunogenicity of the HVJ envelope protein than those of bacteria-derived plasmid DNA or the beta-galactosidase gene product. From these findings, we conclude that HVJ liposomes are a clinically safe and effective gene transfer vector to treat HCC.

Non-viral vectors in cancer gene therapy: principles and progress

This review focuses on the use of synthetic (non-viral) delivery systems for cancer gene therapy. Therapeutic strategies such as gene replacement/mutation correction, immune modulation and molecular therapy/'suicide' gene therapy type approaches potentially offer unique and novel ways of fighting cancer, some of which have already shown promise in early clinical trials. However, the specific and efficient delivery of the genetic material to remote tumors/metastases remains a challenge, which is being addressed using a variety of viral and non-viral systems. Each of these disparate systems has distinct advantages and disadvantages, which need to be taken into account when a specific therapeutic gene is being used. The review concentrates on particulate gene delivery systems, which are formed through non-covalent complexation of cationic carrier molecules (e.g. lipids or polymers) and the negatively charged plasmid DNA. Such systems tend to be comparatively less efficient than viral systems, but have the inherent advantage of flexibility and safety. The DNA-carrier complex acts as a protective package, and needs to be inert and stable while in circulation. Once the remote site has been reached the complex needs to efficiently transfect the targeted (tumor) cells. In order to improve overall transfection specificity and efficiency it is necessary to optimize intracellular trafficking of the DNA complex as well as the performance after systemic administration. Common principles and specific advantages or disadvantages of the individual synthetic gene delivery systems are discussed, and their interaction with tumor-specific and generic biological barriers are examined in order to identify potential strategies to overcome them.