MTOR and plasma cell myeloma: In gastric cancer cells, ovarian cancer and multiple myeloma, AMPK pathway is activated via phosphorylating at Thr172 and subsequently inactivates mTOR with dephosphorylation at Ser2448 and its downstream targets including p70S6K (dephosphorylation at Thr389), 4E-BP1 (dephosphorylation at Thr37/46) and p-rS6 (dephosphorylation at Thr37/46) after tigecycline treatment, thereby inducing cell autophagy or overcoming chemoresistance [23,39,40].