MTOR and nonpapillary renal cell carcinoma: Furthermore, since the 786-0 cell line is known to contain a phosphatase and tensin homologue (PTEN) mutation (although rarely observed in ccRCC tissues),30 it would be of interest to examine how deficiency of PTEN and/or dysregulation of the phosphoinositide-3 kinase/AKT/mammalian target of rapamycin signalling pathway impacts QPRT expression.