Exosome-mediated transfer of miR-222 is sufficient to increase tumor malignancy in melanoma

Abstract

BackgroundGrowing evidence is showing that metastatic cell populations are able to transfer their characteristics to less malignant cells. Exosomes (EXOs) are membrane vesicles of endocytic origin able to convey their cargo of mRNAs, microRNAs (miRs), proteins and lipids from donors to proximal as well as distant acceptor cells. Our previous results indicated that miR-221&222 are key factors for melanoma development and dissemination. The aim of this study was to verify whether the tumorigenic properties associated with miR-222 overexpression can be also propagated by miR-222-containing EXOs.MethodsEXOs were isolated by UltraCentrifugation or Exoquick-TC® methods. Preparations of melanoma-derived vesicles were characterized by using the Nanosight™ technology and the expression of exosome markers analyzed by western blot. The expression levels of endogenous and exosomal miRNAs were examined by real time PCR. Confocal microscopy was used to evaluate transfer and uptake of microvesicles from donor to recipient cells. The functional significance of exosomal miR-222 was estimated by analyzing the vessel-like process formation, as well as cell cycle rates, invasive and chemotactic capabilities.ResultsBesides microvesicle marker characterization, we evidenced that miR-222 exosomal expression mostly reflected its abundance in the cells of origin, correctly paralleled by repression of its target genes, such as p27Kip1, and induction of the PI3K/AKT pathway, thus confirming its functional implication in cancer. The possible differential significance of PI3K/AKT blockade was assessed by using the BKM120 inhibitor in miR-222-transduced cell lines. In addition, in vitro cultures showed that vesicles released by miR-222-overexpressing cells were able to transfer miR-222-dependent malignancy when taken-up by recipient primary melanomas. Results were confirmed by antagomiR-221&222 treatments and by functional observations after internalization of EXOs devoid of these miRs.ConclusionAll together these data, besides generally confirming the role of miR-222 in melanoma tumorigenesis, supported its responsibility in the exosome-associated melanoma properties, thus further indicating this miR as potential diagnostic and prognostic biomarker and its abrogation as a future therapeutic option.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-0811-2) contains supplementary material, which is available to authorized users.

Identification of urinary exosomal noncoding RNAs as novel biomarkers in chronic kidney disease

“…Similarly, expression of miR-31 was reported to be down-regulated in polycystic kidney disease (Pandey et al 2008), whereas in exosomes from CKD patients we found it to be significantly increased. Also, miR-222 has been demonstrated to be upregulated in exosomes from melanoma cells, promoting Identification of urinary exosomal noncoding RNAs www.rnajournal.org 145 tumorigenesis by activating the PI3K/AKT pathway (Felicetti et al 2016). MiR-877 is significantly down-regulated in blood and renal cell carcinoma (RCC) tissues and is considered a potential biomarker for RCC diagnosis (Shi et al 2016).…”

Exosomes as a novel pathway for regulating development and diseases of the skin (Review)

“…miRNA, single-chain and non-coding RNA with a length of 18-25 nt, regulate gene expression at the post-transcriptional level (45). miRNA interact with mRNA and have been indicated to degrade target mRNA or inhibit target mRNA translation (7). A single miRNA may regulate several target mRNA, and multiple miRNA may also bind to one target mRNA (46).…”

“…Previous studies have indicated that miRNA are also closely related to melanoma (7,(78)(79)(80). For instance, melanoma cells secrete exosomes carrying miR-222 to promote tumorigenesis by activating the phosphoinositide 3-kinase/AKT pathway (7).…”

“…For instance, melanoma cells secrete exosomes carrying miR-222 to promote tumorigenesis by activating the phosphoinositide 3-kinase/AKT pathway (7). The expression level of miRNA-125b was downregulated in serum exosomes of patients with melanoma compared with the levels in healthy individuals.…”

“…The development and function of the skin are affected by multiple factors, including environmental factors and hormones (5). Recently, exosome studies have indicated that some exosomes are involved in the physiological and pathological processes of the skin (6,7). Such findings have provided a novel perspective for the understanding of the molecular mechanisms involved in these processes.…”