Gene therapy for human colorectal cancer cell lines with recombinant adenovirus 5 based on loss of the insulin-like growth factor 2 imprinting.

The recombinant oncolytic adenovirus is a novel anticancer agent to replicate selectively in colon cancer cell lines. Loss of imprinting (LOI) of insulin-like growth factor 2 (IGF2) gene is an epigenetic abnormality phenomenon. We utilized the IGF2 LOI in gene therapy for the malignant tumor cell lines. We investigated the tumoricidal effects of IGF2 LOI on four cell lines by oncolytic adenovirus, and constructed novel adenovirus vectors Ad312-E1A and Ad312-EGFP. The expression of E1A was monitored by real-time PCR and western blot analysis. The viability and apoptosis of colorectal cells infected with Ad312-E1A were tested by CCK-8 and flow cytometry. In addition, we established a colorectal cancer model in nude mice. The results showed that HCT-8 and HT-29 with IGF2 LOI were infected with Ad312-EGFP and then produced the EGFP. Nevertheless, SW480 and GES-1, which were IGF2 MOI, did not produce the EGFP. The Ad312-E1A obviously reduced the cell viability and induced apoptosis in HCT-8 and HT-29 in vitro, and successfully suppressed tumor growth in HT-29 xenografts in nude mice. In summary, the conditionally replicative adenovirus with loss of IGF2 imprinting system has a positive effect on gene therapy.