GSK484, an inhibitor of peptidyl arginine deiminase 4, increases the radiosensitivity of colorectal cancer and inhibits neutrophil extracellular traps

Abstract

IntroductionColorectal cancer (CRC) is the third most common malignancy and a major cause of cancer‐related deaths. Peptidyl arginine deiminase 4 (PAD4 or PADI4) is expressed in neutrophils that, when activated, can drive the formation of neutrophil extracellular traps (NETs). PAD4 has been found to be upregulated in CRC patients and to predict a poor prognosis. This study is aimed at exploring the role of PAD4 inhibitor (GSK484) in NET formation and radioresistance in CRC.MethodsReverse transcriptase quantitative polymerase chain reaction and western blotting were used to measure PAD4 expression in CRC tissues and cells. GSK484, an inhibitor of PAD4, was investigated in the following functional assays in vitro: western blotting, clonogenic survival, colony formation, TUNEL, flow cytometry and transwell assays. Nude mouse xenograft models were applied to evaluate the effect of GSK484 on tumor growth in CRC in vivo. The formation of NETs influenced by GSK484 was also investigated.ResultsWe showed upregulation of PAD4 mRNA and protein in CRC tissues and cells. High expression of PAD4 was related to a poor prognosis in CRC patients. GSK484 treatment promoted the radiosensitivity of CRC cells and induced cell death by promoting DNA double‐strand breaks. Rescue experiments further verified that GSK484 inhibited the effects of PAD4 overexpression in irradiated CRC cells. Moreover, GSK484 injection strengthened the radiosensitivity of CRC and inhibited NET formation in vivo.ConclusionsPAD4 inhibitor GSK484 promotes the radiosensitivity of CRC and inhibits NET formation in vivo and in vitro.

Regulation of neutrophil extracellular traps in cancer

“…In addition, in practical treatment, inhibitors with multiple effects at the same time can be selected. For example, in mouse tumor models, GSK484 can significantly enhance the therapeutic effect of PD‐1 antibody and cytotoxic T‐lymphocyte‐associated antigen 4 (CTLA‐4) antibody in addition to being an inhibitor of PAD4, one of the important substances in the formation of NETs 28,107 . PD‐1 and CTLA‐4 antibody inhibitors have shown great potential in melanoma and other cancers, and have good application prospects 108 .…”