TLR4 and neoplasm: LPS has been detected in six common solid tumors, including breast, melanoma, etc.[19] LPS can promote tumor growth, migration, and invasion by inducing toll‐like receptor 4 (TLR4) activation,[20] inhibit the anti‐tumor function of immune cells, and aggravating the malignant evolution of tumors.[21] A survey of patients with pancreatic ductal adenocarcinoma (PDAC) found that serum LPS content was significantly positively correlated with the expression of tumor programmed cell death 1 ligand 1 (PD‐L1).