Serine Protease Inhibitors Enhance Neutrophil Survival

According to the Centers for Disease Control (CDC), cancer is the second leading cause of death in the U.S., with 9.6% of all adults being diagnosed throughout their lifetime. Many of those diagnosed are given low survival rates due to late diagnosis or tumor resistance to chemotherapy. Cancer cells create a pro-inflammatory tumor microenvironment (TME) that supports tumor growth. Neutrophils, key components of this TME, are shown to survive in the TME of some cancers longer than in circulation. Neutrophils produce serine proteases (NSPs), such as cathepsin G (CatG), neutrophil elastase (NE), and proteinase 3 (PR3), which are associated with apoptosis. These can be exploited by tumors to allow for increased neutrophil survival and aid in tumor progression. This study explores the impact of inhibiting NSPs with neutrophil serine protease inhibitors such as tosyl phenylalanyl chloromethyl ketone (TPCK), phenylmethylsulfonyl fluoride (PMSF), and Cathepsin G Inhibitor (CTGI) in a serum-free environment mimicking the TME. We used two neutrophil cell line models (MPRO – mouse and HL-60 – human). Neutrophil proliferation/survival was determined through a WST assay. We observed that increasing NSP inhibitor concentrations enhances cell survival in both MPRO and HL-60 cells, indicating that NSPs and their inhibitors could be a pathway utilized by cancer cells to influence neutrophil phenotype in the TME. This data suggests that targeting NSPs and their inhibitors may offer a promising strategy to disrupt tumor progression.