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In breast cancer, cell-free DNA (cfDNA) has been proven to be a diagnostic and prognostic biomarker. However, there have been few studies on the origin and biological significance of cfDNA. In this study, we assessed the release pattern of cfDNA from breast cancer cell lines under different culture conditions and investigated the biological significance of cfDNA. The cfDNA concentration increased rapidly (6 h) after passage, decreased gradually, and was then maintained at a relatively stable level after 24 h. In addition, the cfDNA concentration did not correlate with the amount of apoptotic and necrotic cells. Interestingly, if more cells were in the G1 phase, more cfDNA was detected (p < 0.01) and the cfDNA concentration correlated positively with the percent of cells in the G1 phase (p < 0.05). We observed that cells could release cfDNA actively, but not exclusively, via exosomes. Furthermore, we showed that cfDNA could stimulate hormone receptor-positive breast cancer cell proliferation by activating the TLR9-NF-κB-cyclin D1 pathway. In conclusion, cfDNA is released from breast cancer mainly by active secretion, and cfDNA could stimulate proliferation of breast cancer cells.

PurposeNovel noninvasive biomarkers with high sensitivity and specificity for the diagnosis of breast cancer (BC) are urgently needed in clinics. The aim of this study was to explore whether miRNAs from the miR-106a–363 cluster can be detected in the circulation of BC patients and whether these miRNAs can serve as potential diagnostic biomarkers.MethodsThe expression of 12 miRNAs from the miR-106a–363 cluster was evaluated using qRT-PCR in 400 plasma samples (from 200 BC patients and 200 healthy controls (HCs)) and 406 serum samples (from 204 BC patients and 202 HCs) via a three-phase study. The identified miRNAs were further examined in tissues (32 paired breast tissues), plasma exosomes (from 32 BC patients and 32 HCs), and serum exosomes (from 32 BC patients and 32 HCs).ResultsUpregulated levels of four plasma miRNAs (miR-106a-3p, miR-106a-5p, miR-20b-5p, and miR-92a-2-5p) and four serum miRNAs (miR-106a-5p, miR-19b-3p, miR-20b-5p, and miR-92a-3p) were identified and validated in BC. A plasma 4-miRNA panel and a serum 4-miRNA panel were constructed to discriminate BC patients from HCs. The areas under the receiver-operating characteristic curves of the plasma panel were 0.880, 0.902, and 0.858, and those of the serum panel were 0.910, 0.974, and 0.949 for the training, testing, and external validation phases, respectively. Two overlapping miRNAs (miR-106a-5p and miR-20b-5p) were consistently upregulated in BC tissues. Except for the expression of the plasma-derived exosomal miR-20b-5p, the expression patterns of exosomal miRNAs were concordant between plasma and serum, indicating the potential use of exosomal miRNAs as biomarkers.ConclusionWe identified four plasma miRNAs and four serum miRNAs from the miR-106a–363 cluster as promising novel biomarkers for the diagnosis of BC.Electronic supplementary materialThe online version of this article (10.1007/s10549-018-4757-3) contains supplementary material, which is available to authorized users.

Background: Breast cancer stem cells (BCSCs) play an essential role in facilitating breast cancer relapse and metastasis. The underlying mechanism, however, remains incompletely understood. In the current study, we investigated the clinical significance, biological function and mechanism of a long noncoding RNA CCAT1 (LncCCAT1) in BCSCs.Methods: Firstly, lncRNAs expression in poorly differentiated breast cancer tissues and BCSCs were measured by lncRNA microarray and confirmed in breast cancer tissues and cell lines. The functional roles and mechanisms of LncCCAT1 were further investigated by gain and loss of function assays in vitro and in vivo.Results: LncCCAT1 is markedly upregulated in breast cancer tissues BCSCs and is correlated with poor outcomes in breast cancer patients. Overexpression of LncCCAT1 contributes to the proliferation, stemness, migration and invasion capacities of BCSCs. Mechanistic investigation suggests that LncCCAT1 can interact with miR-204/211, miR-148a/152 and Annexin A2(ANXA2), then upregulate T-cell factor 4 (TCF4) or promote translocation of β-catenin to the nucleus where it activates TCF4, leading to the activation of wingless/integrated (Wnt) signaling. Furthermore, TCF4 can also bind to the promoter of LncCCAT1 to promote LncCCAT1 transcription, thus forming a positive feedback regulatory circuit of LncCCAT1-TCF4-LncCCAT1 in BCSCs.Conclusions: LncCCAT1 plays an important role in breast cancer progression and may serve as a novel target for breast cancer diagnosis and therapy.