PCK2 and neoplasm: Interestingly, mass cultures of shRNA-silenced PEPCK-M cells described here (sh1-PCK2 and sh2-PCK2) and grown as fat pad grafts in nude mice for several weeks, reverted to wild-type, shCtrl levels of PEPCK-M expression suggesting significant selective pressure in the tumor to favor cells with higher levels of PEPCK-M (Supplementary Figure 6).