1138 - Circular RNA NCAPG promotes breast cancer metastasis through acting as the sponge of miR-200s

Background

Metastatic breast cancer remains incurable. Tumor-associated macrophages (TAMs) represent major component of the tumor microenvironment that supports breast cancer metastasis. Circular RNAs are new class of endogenous noncoding RNAs. They uniquely have a covalently closed loop structure, making them stable and ideal candidate biomarkers. We identified a circular RNA and explored first how it played a dual role in epithelial to mesenchymal transition (EMT) and macrophage recruitment.

Methods

We first analyzed TCGA database about whether mesenchymal tumors could be more likely to recruit TAMs. ELISA assay was performed for determining expression level of chemokines (CSF-1, CCL2, CCL5, C5a, VEGFA, IL-34) after cell line MCF-7 finishing EMT. Next, we predicted microRNAs which could regulate CSF-1 expression and inhibit EMT. Circular RNA was identified via comparing expression levels between mesenchymal-like and epithelial-like cells using circRNA microarrays. The specific mechanisms were explored via series of molecular biology assays in vitro and in vivo.

Results

Correlation analysis of relationship between EMT score and expression of all classical chemokines that could recruit macrophage revealed a positive association (r2>0.3, P < 0.05) among 1079 breast cancer cases. Increased expression level of CSF-1 was found the most significant after EMT. miR-200b and miR-200c that inhibiting breast cancer EMT were confirmed targeting 3’UTR of CSF-1 mRNA and decreasing migration of TAMs. Circular RNA NCAPG was found highly expressed in mesenchymal-like cells and could promote breast cancer metastasis in vitro and in vivo. Poor clinical outcome was found in circNCAPG overexpression group among 141 breast cancer cases. CircNCAPG was proven to be located in cytoplasm and found could sponge of miR-200b and miR-200c. Expression level of CSF-1 and ZEB-1 (also targeted by miR-200s and regulating key process of EMT) was found decreasing significantly after knocking down circNCAPG both in vitro and in vivo, leading to breast cancer metastasis inhibition.

Conclusions

Mesenchymal tumors have the ability to recruit more TAMs. A new molecule: circNCAPG participates in this process via acting as the sponge of miR-200s and regulates CSF-1 and ZEB-1 expression.

Editorial acknowledgement

This research was supported by National Program on Key Research Project (No. 2016YFC0905900), Medical Training Programme Foundation for the Talents by Jiangsu Provincial Department of health (No.17 [2016]), The 333 Talent Project of Jiangsu Province, top-level (No.4 [2016]), the National key clinical specialist construction Programs of China (No.544 [2013]), Major Program of Natural Science Foundation of Jiangsu Province (No. BL2014090), Natural Science Foundation of Jiangsu Province (No. BK20151579), A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD, JX10231802). This study was also funded by the National Natural Science Foundation of China (grant number 81602551), the Key Research Program for the Social Development of Jiangsu Province, China (BE2015718) and the National Natural Science Foundation of China (No. 81602551).

Clinical trial identification

Legal entity responsible for the study

Jiangsu Province Hospital.

Funding

This research was supported by National Program on Key Research Project (No. 2016YFC0905900), Medical Training Programme Foundation for the Talents by Jiangsu Provincial Department of health (No.17 [2016]), The 333 Talent Project of Jiangsu Province, top-level (No.4 [2016]), the National key clinical specialist construction Programs of China (No.544 [2013]), Major Program of Natural Science Foundation of Jiangsu Province (No. BL2014090), Natural Science Foundation of Jiangsu Province (No. BK20151579), A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD, JX10231802). This study was also funded by the National Natural Science Foundation of China (grant number 81602551), the Key Research Program for the Social Development of Jiangsu Province, China (BE2015718) and the National Natural Science Foundation of China (No. 81602551).

Disclosure

All authors have declared no conflicts of interest.