Construction of an Oncolytic Adenovirus for Selective Replication in Breast Cancer Cells

Introduction & Aim: Targeted therapy of cancer using oncolytic viruses is a new advanced treatment. In this study we used microRNA-targeting strategy to generate a new adenovirus that selectively replicate in breast cancer cells but spare normal cells. MicroRNA-145 is reportedly down-regulated in breast tumor cell lines and malignant tissues but is frequent in normal cells. We constructed a miRNA-145- regulated oncolytic adenovirus. This study is the first effort for targeting oncolytic adenovirus to breast cancer cells using differential expression of miRNA in breast tumor and normal cells. Methods: A control adenovirus and an adenovirus carrying miR-145-5p targets in E1A gene (AD5-miR- 145-5pT) generated by Gateway technology. The MCF-7 human breast cancer cell line and the normal human mammary epithelial cells (HMEpC) were infected with AD5-control and AD5-miR145-5pT, and then the viral titers were measured 12, 24, 36 and 48 h post-infection using TCID50 assay. MTT assay was performed to compare the ability of adenoviruses for destroying MCF-7 cells. Results: Growth kinetic analysis of AD5-miR-145-5pT in MCF-7 cells and HMEpC showed that replication of the adenovirus was inhibited in HMEpC as normal breast cells, whereas the virus efficiently replicated in MCF-7 cells. Infectious titer of AD5-miR-145-5pT at 48 h post-infection in HMEpC was 1600fold lower than that of the AD5-control. MTT assay showed that ability of AD5-miR-145-5pT for destroying the MCF-7 cells is similar to AD5-control Conclusion: The use of differential expression pattern of miR-145 in breast cells is a good mechanism for targeting of adenovirus toward breast cancer cells