Anaplastic Thyroid Cancer Cells Induce the Release of Mitochondrial Extracellular DNA Traps by Viable Neutrophils

Abstract

Neutrophils are key effector cells that orchestrate inflammatory responses in the tumor microenvironment. Although neutrophil extracellular DNA traps (NETs) entrap and kill pathogens, they also contribute to chronic inflammation and cancer progression. Thyroid cancer (TC) is the most frequently occurring cancer of the endocrine system, accounting for 70% of deaths due to endocrine tumors. Although anaplastic TC (ATC) is rare among TCs, it is highly lethal. We demonstrated in a recent study that tumor-infiltrating neutrophil density correlated with TC size. Moreover, TC-derived soluble mediators modulate the human neutrophil phenotype. Our study aimed to investigate the involvement of NETs in human TC. Highly purified neutrophils from healthy donors were primed in vitro with a papillary TC or ATC cell line conditioned medium (CM) or with a normal thyroid CM as control. NET release was quantified using a High-Content Imaging System. Neutrophil viability was assessed by flow cytometry. Fluorescence microscopy, flow cytometry, and PCR were performed to determine the mitochondrial origin of ATC-induced NETs. ATC CM–primed neutrophils were cocultured with ATC cells to determine the effects exerted by NETs on cell proliferation. ATC CM induce NET release, whereas papillary TC or normal thyroid CM did not. ATC CM–induced NET production occurred in a reactive oxygen species–dependent and cell death–independent manner and was associated with mitochondrial reactive oxygen species production; the NETs contained mitochondrial DNA. ATC CM–primed neutrophils promoted ATC cell proliferation in a NET-dependent manner.

In vivo evidence for extracellular DNA trap formation

“…The conversion to a mucoid phenotype coincided with a decline in susceptibility to NETs, raising the possibility that increased alginate production decreases interactions with NETs, or otherwise interferes with killing by NET-associated granule proteins 48 . 4,6,7,144,152 . If the source of infection/stimulation persists, the released mtDNA, having similarity to viral and bacterial DNA (enriched in unmethylated CpG motifs), acts as a danger signal and triggers cytokine production for a protective and regulated immune response 7,55 .…”

“…More recently, it was reported that anaplastic thyroid cancer (ATC) cells induce the release of mitochondrial extracellular DNA traps by viable neutrophils. ATC conditioned medium (CM)-primed neutrophils promoted ATC cell proliferation in a NET-dependent manner 144 . Furthermore, tumor cells have been demonstrated to produce IL-8, attracting myeloid-derived suppressor cells (MDSC) and activating granulocytic MDSC to extrude DNA nets 145 .…”

LPS-mediated neutrophil VEGF-A release is modulated by cannabinoid receptor activation

“…1 In the last decades this view has been challenged due to recent evidences indicating that neutrophils survival time is significantly longer than the lifespan usually reported (<1 d) 2 and they produce a variety of cytokines and chemokines, 3 lipid mediators, angiogenic factors, 4 and neutrophil extracellular traps. 5 There is now evidence that PMNs play a role in several chronic inflammatory disorders, 6 cardiovascular diseases, 7 asthma, 8,9 tumors, 4,10 sepsis, 11,12 and parasitic diseases. 13 To exert their functions, PMNs express a plethora of immunoreceptors, including TLRs 14 and endocannabinoids receptors.…”

Is There a Role for Basophils in Cancer?

“…Neutrophils from patients with myeloproliferative neoplasms associated with JAK2 V617F somatic mutation have an increase in NET formation and thrombosis and mice with knock-in of JAK2 V617F have an increased propensity for NET formation and thrombosis (166). Recently, we have demonstrated that anaplastic thyroid cancer cells can induce the release of mitochondrial DNA traps by viable neutrophils (167). Collectively, these studies indicate that NETs can sustain several aspects of tumor growth, the formation of metastasis, and promote cancer-associated thrombosis.…”

“…Activated human and mouse basophils release BETs ( 116 – 118 ). There is mounting evidence that extracellular DNA traps have multiple effects in cancer ( 160 ) favoring tumor growth ( 167 ), awakening dormant cancer cells ( 165 ), and promoting metastasis in mouse models and in humans ( 161 , 164 ). Further studies should evaluate the presence of BETs in experimental and human cancers and whether basophil extracellular traps modulate tumor growth and the formation of metastasis in vivo .…”