LGR5 and breast cancer: Accumulating data has demonstrated that the silencing of Lgr5 influences the functional and molecular outcome of colorectal cancer cells, breast cancer cells, cervical cancer and ovarian cancer [25, 43, 46–47]; for example, previous reports indicated that knocking down endogenous Lgr5 in cultured colorectal cancer cell lines reduced their proliferation, migration, invasion, growth rates and colony formation capability.