BackgroundThe epithelial–mesenchymal transition (EMT) is crucial for the invasion and metastasis of breast cancer. However, how Notch signaling regulates the EMT process and invasion in breast cancer remains largely unknown.MethodsThe impact of Notch1 silencing by specific shRNAs on the EMT and invasion of human breast cancer MCF-7 and MDA-MB-231 cells as well as xenografts was tested by western blot, real-time polymerase chain reaction (RT-PCR), immunofluorescence, transwell, and immunohistochemistry assays. The effect of Slug silencing or upregulation on the EMT and invasion of breast cancer cells was analyzed, and the effect of Notch1 signaling on Slug expression was determined by the luciferase reporter assay.ResultsThe Notch1 intracellular domain (N1ICD) and Jagged1 were expressed in breast cancer cells. Notch1 silencing reversed the spontaneous EMT process and inhibited the migration and invasion of breast cancer cells and the growth of xenograft breast cancers. The expression of N1ICD was upregulated significantly by Jagged1-mediated Notch signaling activation. Moreover, Jagged1-mediated Notch signaling promoted the EMT process, migration, and invasion of breast cancer cells, which were abrogated by Notch silencing. Furthermore, the N1ICD positively regulated the Slug expression by inducing Slug promoter activation. Importantly, the knockdown of Slug weakened the invasion ability of breast cancer cells and reversed the Jagged1-induced EMT process with significantly decreased expression of vimentin and increased expression of E-cadherin. In addition, Slug overexpression restored the Notch1 knockdown-suppressed EMT process.ConclusionsOur novel data indicate that Notch signaling positively regulates the EMT, invasion, and growth of breast cancer cells by inducing Slug expression. The Notch1–Slug signaling axis may represent a potential therapeutic target for breast cancer therapy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-015-0295-3) contains supplementary material, which is available to authorized users.

Although cancer stem cells have been well characterized in numerous malignancies, the fundamental characteristics of this group of cells, however, have been challenged by some recent observations: cancer stem cells may not necessary to be rare within tumors; cancer stem cells and non-cancer stem cells may undergo reversible phenotypic changes; and the cancer stem cells phenotype can vary substantially between patients. Here the current status and progresses of cancer stem cells theory is illustrated and via providing a panoramic view of cancer therapy, we addressed the recent controversies regarding the feasibility of cancer stem cells targeted anti-cancer therapy.

Autocrine vascular endothelial growth factor (VEGF) can regulate the survival and progression of cancers through its various receptors. But the mechanisms and mediators for these functions are largely uncovered, especially in breast cancer. We examined the potential roles and mechanisms of VEGF/neuropilin-1 (NRP-1) axis in regulating the tumorigenesis and metastasis of breast cancer and found the expression of VEGF and NRP-1 correlated with aggressiveness of breast cancer. Knockdown of VEGF or NRP-1 inhibited the proliferation, migration and invasion, but enhanced the apoptosis of MDA-MB-231 cells. In contrast, induction of NRP-1 over-expression promoted the proliferation, migration and invasion of MCF-7 cells. VEGF or NRP-1 silencing attenuated the epithelial-mesenchymal transition (EMT) process and the activation of NF-κBp65, but enhanced GSK-3β expression in MDA-MB-231 cells while NRP-1 over-expression reversed the effects in MCF-7 cells. Treatment with hVEGF165 did not change the inhibition in NRP-1 silencing MDA-MB-231 cells, but enhanced the aggressiveness of NRP-1 over-expressing MCF-7 cells. In addition, VEGF-silencing inhibited the growth and metastasis of implanted MDA-MB-231 tumors in vivo. Our novel data suggest that the positive regulation of the VEGF/NRP-1 axis on the tumorigenesis and metastasis of breast cancer may be associated with enhancing the EMT process and the NF-κB and β-catenin signaling. Hence, the VEGF/NRP-1 axis may be a valuable target for design of therapies for intervention of breast cancer.

Thymoquinone (TQ, 2‐methyl‐5‐isopropyl‐1,4‐benzoquinone), a bioactive constituent extracted from the seeds of Nigella sativa, has been proved to exert anti‐tumor efficiency in various cancers. Autophagy is a self‐digestion phenomenon, and its role in tumor formation and progression remains controversial. In the present study, we investigated the effects of TQ on renal cell cancer (RCC) cell lines (786‐O and ACHN) using wound healing assay, transwell assay and western blot analysis. We found that TQ effectively inhibited the metastatic capacity of RCC cells in vitro, which was also verified in a xenograft model. Meanwhile, we observed LC3 puncta and detected the expression of LC3 in TQ‐treated RCC cells, and then found that autophagy was induced by TQ in 786‐O and ACHN cell lines. In addition, TQ inhibited the migration and invasion as well as the EMT in RCC cells in an autophagy‐dependent manner. To further explore the underlying mechanism, we detected the AMPK/mTOR signaling pathway. The results indicated that TQ inhibited the metastasis of RCC cells by inducing autophagy via AMPK/mTOR signaling pathway. In conclusion, our findings provide a novel therapeutic strategy that aims at TQ‐induced autophagy in RCC treatment.

Abstract. Krukenberg tumor is a rare metastastic tumor of the ovary, characterized by poor prognosis. In order to analyze the clinical characteristics and prognostic factors, we retrospectively investigated 128 patients who were diagnosed with Krukenberg tumor between January, 1990 and December, 2010. The median patient age was 48 years. The median overall survival (OS) of Krukenberg tumor for all patients was 16 months (95% CI: 15-19 months). The median OS among patients with Krukenberg tumors of gastric, colorectal, breast and other origins (including appendix, gallbladder, small intestine and unknown primary) was 11, 21.5, 31 and 19.5 months, respectively (P<0.0001). In the univariate analysis, synchronous metastasis, no chemotherapy, ovarian metastasis beyond the pelvis, ascites and no metastasectomy were identified as significant poor prognostic factors. The multivariate analysis suggested that synchronous metastasis (P=0.0080), pelvic invasion (P=0.0138), ascites (P<0.0001) and no metastasectomy (P=0.0060) were independent factors for predicting unfavorable OS. It was suggested that the prognosis of Krukenberg tumor is dismal and ovarian metastasectomy may prove beneficial. Adequate treatment planning is required for this group of patients. IntroductionKrukenberg tumor is a rare metastatic signet ring cell tumor of the ovary, accounting for 1-2% of all ovarian tumors. The stomach is the primary site in the majority of Krukenberg tumor cases, followed by carcinomas of the colon, appendix and breast, particularly invasive lobular carcinoma (1). The eponym was attributed to this tumor following the description of 5 cases by Friedrich Krukenberg (1871-1946) in 1896, who described it as being common among young women, presenting with ascites, an uneven knobby ovarian surface and lymphatic involvement (2). These tumors are characterised by uncertain pathogenesis, challenging etiological diagnosis and poorer prognosis compared with their primaries. Previously, any metastatic ovarian cancer was referred to as Krukenberg tumor; however, Novak and Gray (3) created new diagnostic criteria to eliminate any confusion. Accordingly, a mucin-secreting signet ring cell carcinoma in the dense fibroblastic stroma of the ovary is referred to as Krukenberg tumor. The diagnosis of Krukenberg tumor is currently based on the diagnostic criteria of the World Health Organization based on the pathological description by Serov and Scully (4). The presence of the following characteristics is required for diagnosis: Stromal involvement, mucin-producing neoplastic signet ring cells and ovarian stromal sarcomatoid proliferation.Krukenberg tumor is considered as a late-stage disease with poor prognosis and may account for 30-40% of metastatic cancers to the ovaries (5). The treatment approach to these metastatic ovarian tumors remains controversial. To date, treatment mainly consists of ovarian metastasectomy, chemotherapy or radiotherapy; however, the optimal treatment has not yet been established. As the biological behavior and clinical...

The chemokine (C-C motif) ligand 2 (CCL2) with its cognate receptor chemokine (C-C motif) receptor 2 (CCR2) plays important roles in tumor invasion and metastasis. However, the mechanisms and mediators for autocrine CCL2 and CCL2-CCR2 axis remain elusive in breast cancer. Here we examined the levels of CCL2 in 4 breast cancer cell lines along with 57 human breast cancer specimens and found them significantly increased with presence of 17β-estradiol (E2) in estrogen receptor (ER)-positive breast cancer cells, while anti-estrogen treatment weakened this enhancement. CCL2 expression positively correlated with Twist staining and aggressiveness of breast cancer. Estrogen exposure facilitated the proliferation, invasion and metastasis of hormone-dependent breast cancer and promoted angiogenesis via the increased secretion of CCL2 in vitro and in vivo, which could be suppressed by disruption of CCL2-CCR2 axis with CCR2 antagonist RS102895. Knockdown of Twist in MCF-7 cells significantly inhibited E2-induced CCL2 production, indicating an essential role of Twist in CCL2 regulation under estrogenic condition. Our data show the hormonal regulation on CCL2-CCR2 axis is associated with enhanced Twist expression via activation of ERα and PI3K/AKT/NF-κB signaling. Thus, CCL2-CCR2 axis may represent as a novel therapeutic target eagerly needed for hormone-dependent breast cancer.

Breast cancer is the most common malignancy in women. The Notch signaling pathway has been shown to be associated with the development and progression of many human cancers, including breast cancer, but the precise mechanism remains unknown. Here, the influence of Notch1 signaling in mammary epithelial cells was studied. We showed that Notch1 promotes proliferation in MCF7 and MCF10A cells. Transwell assay indicated that Notch1 overexpression promotes cell migration and the invasion of breast cancer cells. We showed that MCF7 and MCF10A cells overexpressing Notch1 acquired features of epithelial-mesenchymal transition (EMT) and displayed a cancer stem cell (CSC) phenotype. The expression levels of the epithelial markers E-cadherin and occludin were decreased, while the expression levels of the mesenchymal markers N-cadherin, vimentin and fibronectin were increased in cells overexpressing Notch1. We demonstrated that Notch1 induced phosphorylation of the signal transducer and activator of transcription 3 (STAT3) in breast cancer cells and increased the expression of p65 and interleukin (IL)-1β. Inhibition of STAT3 activity by JSI124 reduced the expression of p65 and IL-1. Treatment of MCF7-notch1 and MCF10A-notch1 cells with JSI124 also reduced the expression of N-cadherin, markers of epithelial mesenchymal transition and increased the expression of E-cadherin. Our results suggest that Notch1 promotes EMT and the CSC phenotype through induction of STAT3.

The recurrence and metastasis of breast cancer limit the effectiveness of clinical treatments, making them important issues for clinicians to address. Tumor-associated macrophages (TAMs) contribute to regulating the immune system. C-C motif chemokine ligand 5 (CCL5) is an inflammatory chemokine that promotes chemotaxis on cells involved in the immune/inflammatory response. Breast cancer cells that secrete CCL5 act on THP-1 cells, influencing the invasion and metastasis of tumors. However, knowledge remains limited regarding the mechanism underlying the effects of CCL5 on breast cancer cells and TAMs, as well as the mechanisms promoting the migration and invasion of breast cancer. The present study demonstrated that the positive expression of CCL5 was associated with lymph node status and tumor-node-metastasis stage. Treatment with ≥20 ng/ml CCL5 significantly promoted the migration and invasion of MCF-7 and MDA-MB-231 cells. CCL5-small interfering RNA intervention significantly decreased the migration and invasion of the two cell types. In vitro, THP-1 cells were successfully induced to become TAMs, which were then recruited via the chemotactic effects of CCL5. This process was achieved through the co-stimulation of phorbol-12-myristate-13- acetate, interleukin-4 (IL-4) and IL-13. The nuclear factor-κB (NF-κB) signaling pathway was activated to regulate EMT, as well as the migration and invasion process of MCF-7 cells, when co-cultured with TAMs. We also reported that blocking the expression of CCL5 in vivo may significantly inhibit the growth of human breast cancer xenografts. Therefore, targeting CCL5 may be considered as a novel therapeutic strategy for suppressing the invasion and metastasis of breast cancer.