Moreover, elevated LPS result from gut microbiota imbalance has been implicated in the secretion of cathepsin K (CTSK), which further promotes CRC metastasis by stimulating M2 polarization of tumor-associated macrophages (TAMs) through the TLR4/mTOR pathway (Li R. et al., 2019). The gene discussed is CTSK; the disease is colorectal carcinoma.