Transforming Growth Factor-Beta 1 Induces Neutrophil Apoptosis in Colorectal Cancer Liver Metastases

Vessel co-option correlates with resistance against anti-angiogenic agents and chemotherapy in colorectal cancer liver metastasis (CRCLM). We previously identified higher intensity of neutrophils in the tumour microenvironment of vessel co-opting CRCLM lesions compared to their angiogenic counterparts. Herein, we demonstrated that over 50% of the neutrophils in vessel co-opting lesions are expressing pro-apoptotic markers including cleaved caspase-3 and poly (ADP-ribose) polymerase-1 (PARP-1). Our previous publications suggested upregulation of transforming growth factor-beta (TGFβ1) in the microenvironment of vessel co-option CRCLM. Therefore, we examined the effect of TGFβ1 on the expression of cleaved caspase-3 and PARP-1 in neutrophils in vitro. Significantly, we noticed the upregulation of pro-apoptotic markers upon exposure to TGFβ1. This finding might pave the way to determine the role of neutrophils in developing vessel co-option in CRCLM in the future.