The study investigates the effects of Torin1, a highly potent and selective ATP-competitive inhibitor of mTOR, on mammalian cells. Unlike rapamycin, which is known to inhibit both mTORC1 and mTORC2, Torin1 primarily targets mTORC1. The results show that Torin1 impairs cell growth and proliferation more effectively than rapamycin, and these effects are independent of mTORC2 inhibition. The enhanced inhibitory effects of Torin1 are attributed to its ability to suppress rapamycin-resistant functions of mTORC1, such as cap-dependent translation and suppression of autophagy. These functions are crucial for cell growth and proliferation and are mediated by mTORC1-dependent phosphorylation of 4E-BP1. The findings challenge the assumption that rapamycin completely inhibits mTORC1 and suggest that direct inhibitors of mTORC1 kinase activity may be more effective in inhibiting tumors that depend on mTORC1.The study investigates the effects of Torin1, a highly potent and selective ATP-competitive inhibitor of mTOR, on mammalian cells. Unlike rapamycin, which is known to inhibit both mTORC1 and mTORC2, Torin1 primarily targets mTORC1. The results show that Torin1 impairs cell growth and proliferation more effectively than rapamycin, and these effects are independent of mTORC2 inhibition. The enhanced inhibitory effects of Torin1 are attributed to its ability to suppress rapamycin-resistant functions of mTORC1, such as cap-dependent translation and suppression of autophagy. These functions are crucial for cell growth and proliferation and are mediated by mTORC1-dependent phosphorylation of 4E-BP1. The findings challenge the assumption that rapamycin completely inhibits mTORC1 and suggest that direct inhibitors of mTORC1 kinase activity may be more effective in inhibiting tumors that depend on mTORC1.