MIR503HG and cancer: MIR503HG is the host gene of miR503, and located on chromosome Xq26.3, which is a region enriched for genes associated with human reproduction.11 Originally, MIR503HG was identified to be involved in human endothelial cells and angiogenic processes.12 Soon afterwards, Muys et al13 found MIR503HG expression was increased in placenta, other reproductive tissues and 50% cancer cell lines.