Restoration of miR-299-3p promotes macrophage phagocytosis and suppresses malignant phenotypes in breast cancer carcinogenesis via dual-targeting CD47 and ABCE1.

Immunoevasion has been a severe obstacle for the clinical treatment of breast cancer (BC). CD47, known as an anti-phagocytic molecule, plays a key role in governing the evasion of tumor cells from immune surveillance by interacting with signal-regulated protein α (SIRPα) on macrophages. Here, we report for the first time that miR-299-3p is a direct regulator of CD47 with tumor suppressive effects both in vitro and in vivo. miRNA expression profiles and overall survival of BC cohorts from the Cancer Genome Atlas, METABRIC, or GSE19783 datasets showed that miR-299-3p is downregulated in BC tissues and that BC patients with low levels of miR-299-3p have poorer prognoses. Using dual-luciferase reporter, qRT-PCR, Western blot, and phagocytosis assays, we proved that restoration of miR-299-3p can suppress CD47 expression by directly targeting the predicted seed sequence "CCCACAU" in its 3'-UTR, leading to phagocytosis of BC cells by macrophages, whereas miR-299-3p inhibition or deletion reversed this effect. Additionally, Gene Ontology (GO) analysis and a variety of confirmatory experiments revealed that miR-299-3p was inversely correlated with cell proliferation, migration, and the cell cycle process. Mechanistically, miR-299-3p can also directly target ABCE1, an essential ribosome recycling factor, alleviating these malignant phenotypes of BC cells. In vivo BC xenografts based on nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice further proved that restoration of miR-299-3p resulted in a significant suppression of tumorigenesis and a promotion of macrophage activation and infiltration. Overall, our study suggested that miR-299-3p is a potent inhibitor of CD47 and ABCE1 to exhibit bifunctional BC-suppressing effects through immune activation conjugated with malignant behavior inhibition in breast carcinogenesis and thus can potentially serve as a novel therapeutic target for BC.

Chronic perfluorooctane sulfonate (PFOS) exposure induces hepatic steatosis in zebrafish.

Perfluorooctane sulfonate (PFOS), one persistent organic pollutant, has been widely detected in the environment, wildlife and human. Currently few studies have documented the effects of chronic PFOS exposure on lipid metabolism, especially in aquatic organisms. The underlying mechanisms of hepatotoxicity induced by chronic PFOS exposure are still largely unknown. The present study defined the effects of chronic exposure to low level of PFOS on lipid metabolism using zebrafish as a model system. Our findings revealed a severe hepatic steatosis in the liver of males treated with 0.5µM PFOS as evidenced by hepatosomatic index, histological assessment and liver lipid profiles. Quantitative PCR assay further indicated that PFOS significantly increase the transcriptional expression of nuclear receptors (nr1h3, rara, rxrgb, nr1l2) and the genes associated with fatty acid oxidation (acox1, acadm, cpt1a). In addition, chronic PFOS exposure significantly decreased liver ATP content and serum level of VLDL/LDL lipoprotein in males. Taken together, these findings suggest that chronic PFOS exposure induces hepatic steatosis in zebrafish via disturbing lipid biosynthesis, fatty acid ß-oxidation and excretion of VLDL/LDL lipoprotein, and also demonstrate the validity of using zebrafish as an alternative model for PFOS chronic toxicity screening.