RAB5A in triple-negative breast cancer: a critical role in macrophage reshaping in an exosomal miR-21-dependent manner.

Breast cancer is the leading cause of cancer-related deaths in females, and triple-negative breast cancer (TNBC) is characterized as one of the main subtypes of breast cancer, with poor prognosis and limited treatments. Investigating the molecular basis or discovering relevant oncogenes will greatly help in developing effective targeted therapies. In this study, we ascertained that RAB5A depletion in TNBC cells suppresses the secretion of exosomes and blocks the polarization of macrophages toward an M2 phenotype. By scanning miRNAs associated with macrophage polarization, we identified that miR-21 was the pivotal component in tumor cell-derived exosomes and played a key role in RAB5A-mediated macrophage polarization. The enhanced expression of miR-21 in macrophages is able to potentiate the M2 polarization of macrophages in the presence of tumor cells. Pellino-1 (PELI1) was subsequently identified as the target of miR-21, and forced PELI1 expression partially abrogated the M2 polarization of macrophages induced by miR-21 overexpression. Macrophages stimulated with RAB5A-depleted TNBC cells (coculture, conditioned medium or exosomes) impaired their capability to promote the proliferation, migration, and invasion of tumor cells. In vivo xenograft experiments further confirmed that RAB5A knockdown TNBC cells exhibited reduced tumor formation and impaired tumor-associated macrophage recruitment. These studies shed light on the potential underlying mechanism of RAB5A-mediated macrophage polarization in an exosomal miR-21-dependent manner and provide an experimental basis for the development of RAB5A- or exosome-based tumor therapeutic strategies.

NAA20 recruits Rin2 and promotes triple-negative breast cancer progression by regulating Rab5A-mediated activation of EGFR signaling.

Triple-negative breast cancer (TNBC) is the most aggressive subtype with poor prognosis and high mortality. To improve the prognosis and survival of TNBC patients, it is necessary to explore new targets and signaling pathways to develop novel therapies for TNBC treatment. N-α-acetyltransferase 20 (NAA20) is one of the catalytic subunits of N-terminal acetyltransferase (NatB). It has been reported that NAA20 played a critical role in cancer progression. In this study, we found that NAA20 expression was markedly higher in TNBC tissues than in paracancerous normal tissues using The Cancer Genome Atlas (TCGA) analysis. This result was further confirmed by qRT-PCR and immunohistochemistry (IHC). Knockdown of NAA20 significantly inhibited TNBC cell viability by CCK8 and colony formation assays and cell migration and invasion by Transwell assays. Additionally, NAA20 knockdown decreased the expression of EGFR in TNBC cells. Upon stimulation with EGF and knockdown of NAA20, EGFR internalization and degradation were observed by confocal microscopy. The western blot results showed that NAA20 knockdown down-regulated PI3K, AKT, and mTOR phosphorylation. Next, we further explored the underlying molecular mechanisms of NAA20 by co-immunoprecipitation (Co-IP). The results suggested that there was an interacting relationship between NAA20 and Rab5A. Over-expression of NAA20 could potentiate the expression of Rab5A. Furthermore, the knockdown of Rab5A inhibited EGFR expression and the phosphorylation of downstream signaling targets. NAA20 over-expression offset the knockdown effect of Rab5A and activated EGFR signaling. Finally, we constructed a xenograft mouse model transfected TNBC cells to investigate the role of NAA20 in vivo. NAA20 knockdown markedly suppressed tumor growth and decreased tumor volume and weight. In conclusion, our study demonstrated that NAA20, a novel target of TNBC, could promote TNBC progression by regulating Rab5A-mediated activation of EGFR signaling.

Exosomal miR-655-3p inhibits growth, and invasion and macrophage M2 polarization through targeting CXCR4 in papillary thyroid carcinoma.

Papillary thyroid cancer (PTC) is an endocrine malignancy whose incidence has increased rapidly worldwide. Exosome-miR-655-3p was down-regulated in patients with PTC. However, the effect and molecular mechanism of exosome-miR-655-3p in PTC was indistinct until now. Our study found that exosome-miR-655-3p was decreased in serum of PTC patients. Overexpression of miR-655-3p with mimics significantly shrunk the cell viability, reduced the number of chemotactic and invasive PTC cells. Besides, the proportion of CD163 positive cells and the expression of markers of M2 subtype macrophages was markedly decreased when mononuclear macrophage THP-1 was cultured with exosomes of miR-655-3p mimics. Oppositely, the inhibitor of miR-655-3p exacerbated growth, chemotaxis and invasion of PTC cells, and enhanced the M2 subtype macrophages. Structurally, miR-655-3p could target the 3' untranslated region (3'UTR) of CXCR4 and restrict the expression of CXCR4. In Xenograft tumor experiment, upregulated exosome-miR-655-3p effectively inhibited the growth of tumor and reduced the expression of CXCR4, Ki67 and CD163 in vivo. In summary, exosomal miR-655-3p inhibited growth, invasion and macrophage M2 polarization through targeting CXCR4 in papillary thyroid carcinoma. Regulating exosome-miR-655-3p/CXCR4 may be a potential treatment strategy for PTC.