Transcriptomic profiles of tumor-associated neutrophils reveal prominent roles in enhancing angiogenesis in liver tumorigenesis in zebrafish

Abstract

We have previously demonstrated the pro-tumoral role of neutrophils using a kras-induced zebrafish hepatocarcinogenesis model. To further illustrate the molecular basis of the pro-tumoral role, Tumor-associated neutrophils (TANs) were isolated by fluorescence-activated cell sorting (FACS) and transcriptomic analyses were carried out by RNA-Seq. Differentially expressed gene profiles of TANs from larvae, male and female livers indicate great variations during liver tumorigenesis, but the common responsive canonical pathways included an immune pathway (Acute Phase Response Signaling), a liver metabolism-related pathway (LXR/RXR Activation) and Thrombin Signaling. Consistent with the pro-tumoral role of TANs, gene module analysis identified a consistent down-regulation of Cytotoxicity module, which may allow continued proliferation of malignant cells. Gene Set Enrichment Analysis indicated up-regulation of several genes promoting angiogenesis. Consistent with this, we found decreased density of blood vessels accompanied with decreased oncogenic liver sizes in neutrophil-depleted larvae. Collectively, our study has indicated some molecular mechanisms of the pro-tumoral roles of TANs in hepatocarcinogenesis, including weakened immune clearance against tumor cells and enhanced function in angiogenesis.

Neutrophil Diversity in Health and Disease

“…In view of several species-specific differences that might have a profound impact on the phenotypic and functional plasticity of neutrophils, human and mouse studies are separately discussed, highlighting similarities and differences between current findings in the two species. There is emerging evidence of heterogeneous populations of neutrophils in other organisms, such as the rhesus macaque [10], zebrafish [11,12], and horse [13], but these are beyond the scope of our discussion.…”

Inflammatory Responses during Tumour Initiation: From Zebrafish Transgenic Models of Cancer to Evidence from Mouse and Man

“…Further anti-tumour roles of neutrophils may include triggering apoptosis via activation of TRAIL [102] and promoting the activity of anti-tumour cytotoxic T lymphocytes [103]. In zebrafish, tumours also exhibit high levels of infiltrating neutrophils, which promote metastasis and express genes involved in angiogenesis and immunosuppression [104][105][106][107]. Anti-tumour neutrophil responses are yet to be described within zebrafish cancer models.…”

Neutrophil: A New Player in Metastatic Cancers

“…In addition, Bv8 is an important mediator of neutrophil-dependent angiogenesis, and blocking Bv8 function can inhibit angiogenesis and tumor growth (60,61). Recently, transcriptomic analyses demonstrated that pro-angiogenic genes including vegfa, itgb1, il1b, mmp14, and mmp9 as well as genes encoding other cell adhesion molecules, such as ilgals1 and igals3bp, are upregulated in TANs (62), further confirming a prominent role of neutrophils in promoting tumor angiogenesis.…”