PTCH1 and breast cancer: However, a recent study reported that Tetraspanin-8 (TSPAN8), a tetraspanin family member upregulated in breast cancer stem cells (CSCs) and correlated with poor prognosis in breast cancer patients, interacted with Ptch1 and inhibited its polyubiquitination and turnover by recruiting a deubiquitinase Ataxin3 (ATXN3) [38].