Synergistic Antitumor Effect of Recombinant Adeno-Associated Virus-Mediated Pigment Epithelium-Derived Factor with Hyperthermia on Solid Tumor

Towards Clinical Implementation of Adeno-Associated Virus (AAV) Vectors for Cancer Gene Therapy: Current Status and Future Perspectives

Adeno-associated virus (AAV) vectors have gained tremendous attention as in vivo delivery systems in gene therapy for inherited monogenetic diseases. First market approvals, excellent safety data, availability of large-scale production protocols, and the possibility to tailor the vector towards optimized and cell-type specific gene transfer offers to move from (ultra) rare to common diseases. Cancer, a major health burden for which novel therapeutic options are urgently needed, represents such a target. We here provide an up-to-date overview of the strategies which are currently developed for the use of AAV vectors in cancer gene therapy and discuss the perspectives for the future translation of these pre-clinical approaches into the clinic.

Pigment epithelial-derived factor gene loaded novel COOH-PEG-PLGA-COOH nanoparticles promoted tumor suppression by systemic administration

Anti-angiogenesis has been proposed as an effective therapeutic strategy for cancer treatment. Pigment epithelium-derived factor (PEDF) is one of the most powerful endogenous anti-angiogenic reagents discovered to date and PEDF gene therapy has been recognized as a promising treatment option for various tumors. There is an urgent need to develop a safe and valid vector for its systemic delivery. Herein, a novel gene delivery system based on the newly synthesized copolymer COOH-PEG-PLGA-COOH (CPPC) was developed in this study, which was probably capable of overcoming the disadvantages of viral vectors and cationic lipids/polymers-based nonviral carriers. PEDF gene loaded CPPC nanoparticles (D-NPs) were fabricated by a modified double-emulsion water-in-oil-in-water (W/O/W) solvent evaporation method. D-NPs with uniform spherical shape had relatively high drug loading (~1.6%), probably because the introduced carboxyl group in poly (D,L-lactide-co-glycolide) terminal enhanced the interaction of copolymer with the PEDF gene complexes. An excellent in vitro antitumor effect was found in both C26 and A549 cells treated by D-NPs, in which PEDF levels were dramatically elevated due to the successful transfection of PEDF gene. D-NPs also showed a strong inhibitory effect on proliferation of human umbilical vein endothelial cells in vitro and inhibited the tumor-induced angiogenesis in vivo by an alginate-encapsulated tumor cell assay. Further in vivo antitumor investigation, carried out in a C26 subcutaneous tumor model by intravenous injection, demonstrated that D-NPs could achieve a significant antitumor activity with sharply reduced microvessel density and significantly promoted tumor cell apoptosis. Additionally, the in vitro hemolysis analysis and in vivo serological and biochemical analysis revealed that D-NPs had no obvious toxicity. All the data indicated that the novel CPPC nanoparticles were ideal vectors for the systemic delivery of PEDF gene and might be widely used as systemic gene vectors.

Mesenchymal Stem Cells Engineered to Secrete Pigment Epithelium-Derived Factor Inhibit Tumor Metastasis and the Formation of Malignant Ascites in a Murine Colorectal Peritoneal Carcinomatosis Model

The therapeutic effects of conventional treatments for advanced colorectal cancer with colorectal peritoneal carcinomatosis (CRPC) and malignant ascites are not very encouraging. Vascular endothelial growth factor-A/vascular permeability factors (VEGF-A/VPF) play key roles in the formation of malignant ascites. In previous work, we demonstrated that pigment epithelium-derived factor (PEDF) antagonized VEGF-A and could repress tumor growth and suppress metastasis in several cancer types. Thus, PEDF may be a therapeutic candidate for treating malignant ascites. Mesenchymal stem cells (MSCs) are promising tools for delivering therapeutic agents in cancer treatment. In the study, MSCs derived from bone marrow were efficiently engineered to secrete human PEDF by adenoviral transduction. Then, intraperitoneal Ad-PEDF-transduced MSCs were analyzed with respect to CRPC and malignant ascites in a CT26 CRPC model. MSCs engineered to secrete PEDF through adenoviral transduction significantly inhibited tumor metastasis and malignant ascites formation in CT26 CRPC mice. Antitumor mechanisms of MSCs-PEDF (MSCs transduced with Ad-PEDF: MOI 500) were associated with inhibiting tumor angiogenesis, inducing apoptosis, and restoring the VEGF-A/sFLT-1 ratio in ascites. Moreover, MSC-mediated Ad-PEDF delivery reduced production of adenovirus-neutralizing antibodies, prolonged PEDF expression, and induced MSCs-PEDF migration toward tumor cells. As a conclusion, MSCs engineered to secrete PEDF by adenoviral transduction may be a therapeutic approach for suppressing tumor metastasis and inhibiting malignant ascites production in CRPC.