PDGF-A promoter and enhancer elements provide efficient and selective antineoplastic gene therapy in multiple cancer types

Abstract

Development of antineoplastic gene therapies is impaired by a paucity of transcription control elements with efficient, cancer cellspecific activity. We investigated the utility of promoter (AChP) and 5 0 -distal enhancer (ACE66) elements from the platelet-derived growth factor-A (PDGF-A) gene, which are hyperactive in many human cancers. Efficacy of these elements was tested in multiple tumor cell lines, both in cell culture and as tumor explants in athymic nude mice. Plasmid and viral vectors were constructed with the AChP promoter alone or in fusion with three copies of the ACE66 enhancer for expression of the prototype suicide gene, thymidine kinase (TK). ACE/AChP and AChP cassettes elicited ganciclovir (GCV)-induced cytotoxicity in multiple tumor cell lines. The ACE enhancer element also exhibited synergism with placental and liver-specific promoter elements. An adenovirus containing the AChP-TK cassette produced striking increases in GCV sensitivity in cultured tumor cell lines, as well as GCV-induced regression of U87 MG glioblastoma explants in vivo. TK expression was distributed throughout tumors receiving the therapeutic virus, whereas TdT-mediated dUTP nick end labeling (TUNEL) analysis revealed numerous regions undergoing apoptosis. Vascularization and reticulin fiber networks were less pronounced in virus-GCV-treated tumors, suggesting that both primary and stromal cell types may have been targeted. These studies provide proof-of-principle for utility of the PDGF-A promoter and ACE66 enhancer in antineoplastic gene therapy for a diverse group of human cancers.

MicroRNA-375 inhibits oral squamous cell carcinoma cell migration and invasion by targeting platelet-derived growth factor-A

“…Emerging evidence implicates PDGF-A as a potential prognostic marker, independent of the traditional pathologic parameters (19,20). The promoter of this gene is a potential target for an efficient and selective antineoplastic gene therapy in multiple cancer types, including breast cancer and osteosarcoma (21,22); however, the biological functions of PDGF-A in OSCC remain to be determined. Identifying the association between miR-375 and PDGF-A, which is essential for tumor progression, may provide novel therapeutic targets.…”