Table 1.

Summary of the included studies of NETs in CRC.

Study Design	Animal Models	Cell Type	Major Outcomes/Findings	Authors
Both in vivo and in vitro	Mouse	Human colon carcinoma cell line (HT-29), murine colon carcinoma	NET-associated protein CEACAM1 is an inducer of metastatic progression of CRC and blocking of NETs significantly reduce CRC cell adhesion, migration, and metastasis in murine model.	Rayes et al. [102]
Both in vivo and in vitro	Mouse	DKs-8 (WT allele) cells, DKO-1 (KRAS mutant) cells	Exosomes from KRAS mutant CRC increase IL-8 production and provoke NET formation. Released NETs increase CRC cells growth both in vivo and in vitro.	Shang et al. [82]
In vivo, in vitro, and ex vivo	Human and Mouse	Human hepatocellular carcinoma, human cell line HT29, and mice cell line MC38	NETs raised colorectal malignancy by enriching tumorous interleukin IL-8, which in turn induce more NET production by creating a positive loop along with advancing CRC-driven liver metastasis. Digestion of NETs by DNase I reduced liver metastasis.	Yang et al. [94]
Both in vivo and in vitro	Mouse	Human hepatoma cell line HepG2, murine colon carcinoma MC38	Neutrophil infiltration and NET formation reduced by adeno-associated virus (AAV) based DNase I gene therapy and reduced liver metastasis in a mouse model of CRC liver metastasis.	Xia et al. [101]
Both in vivo and in vitro	Mouse	Murine Lewis Lung carcinoma cell subline H59, Murine colon carcinoma cell line MC38	Primary colon cancer cells provoked NETs generation that prime adhesion of CTCs to the liver and degradation of NETs decreased CRC cell adhesion and spontaneous metastasis to the liver and lung.	Rayes et al. [96]
Both in vivo and ex vivo	Human and Mouse	Murine colorectal (MC38) cells, HCT116, Hepa1-6, and Huh7 cell lines	Patients undergoing curative resection with colorectal metastases to the liver showed an elevated level of NET formation. Increased citrullinated histones and circulating MPO-DNA levels were related to poor survival of CRC patients.	Yazdani et al. [98]
Ex vivo	Human	CRC cells	CD68+ mast cells expressed polyphosphates (PolyP) in colorectal adenomas and/or carcinomas and suggested that CD68+ PolyP expressing mast cells could be used as prognostic marker.	Arelaki et al. [85]
Ex vivo	Human	/	Systemic neutrophils isolated from the CRC patients showed higher levels of NETs producing ability than healthy controls in vitro. In vitro increased NET production is correlated with patients’ major complications than minor complications.	Richardson et al. [81]
Ex vivo	Human	/	Neutrophils isolated from patients undergoing resectional surgery for CRC showed lower NET forming ability in vitro than preoperative neutrophils.	Richardson et al. [103]
In vitro and Ex vivo	Human	Human acute myeloid leukemia (AML) cells, Caco-2 cells	Confirmed presence of NETs within the primary tumor sites of CRC and gradually dispersed to the tumor boundary, particularly to nearby metastatic lymph nodes.	Arelaki et al. [26]
In vivo, in vitro, and ex vivo	Human and Mouse	MC38 and Luciferase-expressing MC38 cells (MC38/Luc)	Increased postoperative NETs generation after curative liver resection of colorectal metastasis patients. NETs further fuel the metastasis condition and reduce more than 4-fold disease free survival.	Tohme et al. [25]