Reovirus was noted to be a potential cancer therapeutic when studies suggested it reproduces well in certain cancer cell lines. It replicates specifically in cells that have an activated Ras pathway (a cellular signaling pathway that is involved in cell growth and differentiation). Reovirus replicates in and eventually kills Ras-activated tumour cells and as cell death occurs, progeny virus particles are free to infect surrounding cancer cells. This cycle of infection, replication and cell death is believed to be repeated until all tumour cells carrying an activated Ras pathway are destroyed.