Tumor-associated macrophages promote cholangiocarcinoma progression via exosomal Circ_0020256

Shaoyi Chen,Dawei Zhang,Liangqi Cao,Shiying Li,Zuxiao Chen,Ping Xue,Zilong Wen,Yubin Chen,Haiyan Li,Zongyan Li

doi:10.1038/s41419-022-04534-0

Abstract

This study investigated the exosomal circular RNAs (CircRNAs) produced by tumor-associated macrophages and delivered into the microenvironment of cholangiocarcinoma cells in order to use them as molecular targets for clinical therapy. Tumor-associated M2 macrophages (TAMs) were induced from THP-1 cells and identified by flow cytometry. The TAM-secreted exosomes were isolated from conditioned medium and a CircRNA microarray assay was performed to identify CircRNAs that were uniquely expressed in the isolated exosomes. Circ_0020256 was especially identified based on having the highest differential expression level among all of the CircRNA candidates. In vitro and in vivo experiments were performed to assess the effects of TAMs, exosomes, and Circ_0020256 on the growth and migration of cholangiocarcinoma (CCA) cells. The induced TAMs promoted the proliferation, migration, and invasion of CCA cells and those effects were mediated by exosomes secreted by the TAMs. In CCA cells (RBE and HCCC-9810), Circ_0020256 significantly promoted cellular activity by interacting with its intra-cellular microRNA target, miR-432-5p. In contrast, overexpression of transcription factor E2F3 in CCA cells restored the CCA cellular activities that were inhibited by miR-432-5p. On the other hand, treatment with small interference RNA (siRNA) for Circ_0020256 inhibited CCA cell proliferation, migration, and invasion both in vitro and in vivo. In conclusion, Circ_0020256 in TAM-secreted exosomes promoted the proliferation, migration, and invasion of CCA cells, and that promotional activity was regulated via a Circ_0020256/miR-432-5p/E2F3 axis.

Highlights

Cholangiocarcinoma (CCA) is a common primary malignant tumor, and in recent years, its incidence has significantly increased worldwide [1]
Tumor-associated macrophages (TAMs) promoted the proliferation, migration, and invasion of CCA cells THP-1 cells, as a model of monocytes differentiating into macrophages, were used in our studies in order to illustrate the effects of TAMs on both the progression and metastasis of CCA
Results of cell expansion studies indicated that both types of CCA cells cultured in conditioned medium (CM) showed increased rates of proliferation when compared to CCA cells in control medium or CCA cells co-cultured with untreated THP-1 cells (Un-mac) (Fig. 1C)

Summary

Introduction

Cholangiocarcinoma (CCA) is a common primary malignant tumor, and in recent years, its incidence has significantly increased worldwide [1]. A high density of TAMs in surgically resected tumor tissues is predictive of both a high likelihood of CCA recurrence and a poor prognosis [7]. Another recent study showed that the recruitment of PD-L1 + TAMs contributed to CCA progression [8]. Together, these previous findings revealed that TAMs play important roles in CCA progression; the molecular mechanisms underlying the effects of TAMs have not yet been identified

Methods

Results

Conclusion