STK11 and breast cancer: For example, the overexpression of phosphatidylinositol 3-kinase (PI3K) and protein kinase B (PKB), imbalance of the upstream negative regulator phosphatase and tensin homolog (PTEN), tuberous sclerosis complex 1/2 (TSC1/2), and liver kinase B1 (LKB1) can result in the overactivation of the mTOR signaling pathway, causing cell mutation and promoting a variety of malignant tumors, including prostatic cancer, breast cancer, and endometrial cancer [2–4].