Abstract 2818: Neutrophil extracellular traps regulate mitochondrial quality control in cancer cells to promote tumor growth
Authors: Tohme Samer , Yazdani Hamza , Simmons Richard L. , Tsung Allan , Bartlett David 
Published: August 2019

Introduction: Evidence is accumulating that neutrophil extracellular traps (NETs) are present within tumors and confer a worse outcome. The exact mechanisms of their role in tumor progression have been far from answered.

Methods: Preoperative serum and tumor tissue were obtained from colorectal cancer liver metastases (CCLM) patients. In vivo, subcutaneous and liver metastasis tumor models were done in WT and nu/nu mice. Hepatocellular and colon murine and human cancer cell lines were used. DNase injection or PAD4KO mice were used to suppress NETs. In vitro, human and mice neutrophils were isolated and stimulated with PMA to form NETs to treat multiple cancer cell lines and examine NETs effect on their bioenergetics.

Results:Tumors from CCLM patients showed increased NETs. Preoperative serum MPO-DNA, a NET marker, was found to be significantly elevated in CCLM patients compared to healthy controls. Patients with high MPO-DNA had significantly shorter overall and disease-free survival than patients with low MPO-DNA. The median disease-free survival was 5.8 times shorter (5.5vs.31 months, p&lt;0.001). In vivo, we compared the growth rates of tumors in the subcutaneous and liver metastases models in C57BL/6 WT and PAD4KO mice. Tumors grew slower and were significantly smaller in PAD4 KO mice. Similarly, human cancer cell lines HCT116 and Huh7, grew slower in DNAse-treated nu/nu mice. PAD4KO or DNAse treated tumors showed decreased proliferation and increased in apoptosis and oxidative stress. These tumors had decreased mitochondrial density and mitochondrial DNA and lesser degree of ATP production. There was also a significant decrease in mitochondrial biogenesis proteins PGC-1α, TFAM and NRF-1 in PAD4KO tumors. In vitro, cancer cells treated with NETs showed a significant upregulation in the mitochondrial biogenesis associated genes, increased mitochondrial density and increased ATP production compared to control. NETs significantly enhanced the percentage of cancer cells with reduced mitochondrial membrane potential and increased the oxygen consumption rate. Furthermore, NETs increased cancer cell’s expression of fission and fusion associated proteins DRP-1 and MFN-2 and expression of mitophagy-linked proteins, PINK1 and Parkin. All of which were decreased in PAD4KO tumors. Mechanistically, we demonstrated that neutrophil elastase (NE) released from NETs activates TLR-4 on cancer cells that in turn phosphorylates p38 and activates PGC-1α to upregulate mitochondrial biogenesis and tumor growth.

Conclusion:NETs actively recruited to the tumor microenvironment can alter the metabolic programming of cancer cells by upregulating biogenesis and maintain mitochondrial fission, fusion and mitophagy which result in increased tumor growth. NETs represent a promising therapeutic target to halt cancer progression.

Citation Format: Samer Tohme, Hamza Yazdani, Richard L. Simmons, Allan Tsung, David Bartlett. Neutrophil extracellular traps regulate mitochondrial quality control in cancer cells to promote tumor growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2818.