Circular RNA circBCBM1 promotes breast cancer brain metastasis by modulating miR-125a/BRD4 axis

Circular RNAs (circRNAs) play critical roles in tumorigenesis and the progression of various cancers. We previously identified a novel upregulated circRNA, circBCBM1 (hsa_circ_0001944), in the context of breast cancer brain metastasis. However, the potential biological function and molecular mechanism of circBCBM1 in breast cancer brain metastasis remain largely unknown. In this study, we confirmed that circBCBM1 was a stable and cytoplasmic circRNA. Functionally, circBCBM1 promoted the proliferation and migration of 231-BR cells in vitro and growth and brain metastasis in vivo. Mechanistically, circBCBM1 acted as an endogenous miR-125a sponge to inhibit miR-125a activity, resulting in the upregulation of BRD4 (bromodomain containing 4) and subsequent upregulation of MMP9 (matrix metallopeptidase 9) through Sonic hedgehog (SHH) signaling pathway. Importantly, circBCBM1 was markedly upregulated in the breast cancer brain metastasis cells and clinical tissue and plasma samples; besides, circBCBM1 overexpression in primary cancerous tissues was associated with shorter brain metastasis-free survival (BMFS) of breast cancer patients. These findings indicate that circBCBM1 is involved in breast cancer brain metastasis via circBCBM1/miR-125a/BRD4 axis. CircBCBM1 may serve as a novel diagnostic and prognostic biomarker and potential therapeutic target for breast cancer brain metastasis.     

FOXO3a inhibits the EMT and metastasis of breast cancer by regulating TWIST-1 mediated miR-10b/CADM2 axis

BackgroundBreast cancer is the most common malignancy and has been considered as a leading cause of cancer death in women. Exploring the mechanism of breast cancer metastasis is extremely important for seeking novel therapeutic strategies and improving prognosis.MethodsClinical specimens and pathological characteristics were collected for evaluating the expression of forkhead box class O 3a (FOXO3a) and twist-related protein 1 (TWIST-1) in breast cancer tissues. CCK-8 assay was used to analyze cell proliferation. Cell invasion and migration were assessed by transwell assays. The expression of FOXO3a, TWIST-1, miR-10b, CADM2, FAK, phosphor-AKT and the epithelial-mesenchymal transition (EMT)-related protein (N-cadherin, E-cadherin and vimentin) were analyzed by RT-qPCR, immunohistochemical staining, immunofluorescence assay or western blot, respectively. Xenograft mouse models were used to analyze the role of the FOXO3a in breast cancer.ResultsFOXO3a was down-regulated and TWIST-1 was up-regulated in breast cancer tissues. Overexpression of FOXO3a or knockdown of TWIST-1 suppressed the proliferation, invasion, migration and EMT of breast cancer cells. Overexpression of TWIST-1 could reverse the effect of FOXO3a on the proliferation, invasion, migration and EMT of breast cancer. Moreover, FOXO3a suppressed the growth and metastasis of breast cancer by targeting TWIST1 in vivo.ConclusionFOXO3a inhibited the EMT and metastasis of breast cancer via TWIST-1/miR-10b/CADM2 axis.     

Knockdown of KDM1A suppresses tumour migration and invasion by epigenetically regulating the TIMP1/MMP9 pathway in papillary thyroid cancer

Epigenetic dysregulation plays an important role in cancer. Histone demethylation is a well‐known mechanism of epigenetic regulation that promotes or inhibits tumourigenesis in various malignant tumours. However, the pathogenic role of histone demethylation modifiers in papillary thyroid cancer (PTC), which has a high incidence of early lymphatic metastasis, is largely unknown. Here, we detected the expression of common histone demethylation modifiers and found that the histone H3 lysine 4 (H3K4) and H3 lysine 9 (H3K9) demethylase KDM1A (or lysine demethylase 1A) is frequently overexpressed in PTC tissues and cell lines. High KDM1A expression correlated positively with age <55 years and lymph node metastasis in patients with PTC. Moreover, KDM1A was required for PTC cell migration and invasion. KDM1A knockdown inhibited the migration and invasive abilities of PTC cells both in vitro and in vivo. We also identified tissue inhibitor of metalloproteinase 1 (TIMP1) as a key KDM1A target gene. KDM1A activated matrix metalloproteinase 9 (MMP9) through epigenetic repression of TIMP1 expression by demethylating H3K4me2 at the TIMP1 promoter region. Rescue experiments clarified these findings. Altogether, we have uncovered a new mechanism of KDM1A repression of TIMP1 in PTC and suggest that KDM1A may be a promising therapeutic target in PTC.     

S14 protein in breast cancer cells: direct evidence of regulation by SREBP-1c, superinduction with progestin, and effects on cell growth

Most breast cancers exhibit brisk lipogenesis, and require it for growth. S14 is a lipogenesis-related nuclear protein that is overexpressed in most breast cancers. Sterol response element-binding protein-1c (SREBP-1c) is required for induction of lipogenesis-related genes, including S14 and fatty acid synthase (FAS), in hepatocytes, and correlation of SREBP-1c and FAS expression suggested that SREBP-1c drives lipogenesis in tumors as well. We directly tested the hypothesis that SREBP-1c drives S14 expression and mediates lipogenic effects of progestin in T47D breast cancer cells. Dominant-negative SREBP-1c inhibited induction of S14 and FAS mRNAs by progestin, while active SREBP-1c induced without hormone and superinduced in its presence. Changes in S14 mRNA were reflected in protein levels. A lag time and lack of progestin response elements indicated that S14 and FAS gene activation by progestin is indirect. Knockdown of S14 reduced, whereas overexpression stimulated, T47D cell growth, while nonlipogenic MCF10a mammary epithelial cells were not growth-inhibited. These data directly demonstrate that SREBP-1c drives S14 gene expression in breast cancer cells, and progestin magnifies that effect via an indirect mechanism. This supports the prediction, based on S14 gene amplification and overexpression in breast tumors, that S14 augments breast cancer cell growth and survival.     

CD44 cross-linking induces integrin-mediated adhesion and transendothelial migration in breast cancer cell line by up-regulation of LFA-1 (alpha L beta2) and VLA-4 (alpha4beta1)

CD44, a widely expressed cell surface glycoprotein, plays a major role in cell-cell adhesion, cell-substrate interaction, lymphocyte homing, and tumor metastasis. For tumor metastasis to occur through the blood vessel and lymphatic vessel pathway, the tumor cells must first adhere to endothelial cells. Recent studies have shown that high expression of CD44 in certain types of tumors is associated with the hematogenic spread of cancer cells. However, the functional relevance of CD44 to tumor cell metastasis remains unknown. In this study, we investigated the mechanisms of CD44 cross-linking-induced adhesion and transendothelial migration of tumor cells using MDA-MB-435S breast cancer cell line. Breast cancer cells were found to express high levels of CD44. Using flow cytometric analysis and immunofluorescence staining, we demonstrated that cross-linking of CD44 resulted in a marked induction of the expression of lymphocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4) by exocytosis. These results were also observed with the Hs578T breast cancer cell line. Furthermore, LFA-1- and VLA-4-mediated adhesion and transendothelial cancer cell migration were also studied. Anti-LFA-1 mAb or anti-VLA-4 mAb alone had no effect on adhesion or transendothelial cancer cell migration, but were able to inhibit both of these functions when added together. This shows that CD44 cross-linking induces LFA-1 and VLA-4 expression in MDA-MB-435S cells and increases integrin-mediated adhesion to endothelial cells, resulting in the transendothelial migration of breast cancer cells. These observations provide direct evidence of a new function for CD44 that is involved in the induction of LFA-1 and VLA-4 expression by exocytosis in MDA-MB-435S cells. Because these induced integrins promote tumor cell migration into the target tissue, it may be possible to suppress this by pharmacological means, and thus potentially cause a reduction in invasive capability and metastasis.     

Epigenetic regulator KDM4A activates Notch1-NICD-dependent signaling to drive tumorigenesis and metastasis in breast cancer

BackgroundAltered epigenetic reprogramming and events contribute to breast cancer (Bca) progression and metastasis. How the epigenetic histone demethylases modulate breast cancer progression remains poorly defined. We aimed to elucidate the biological roles of KDM4A in driving Notch1 activation and Bca progression.MethodsThe KDM4A expression in Bca specimens was analyzed using quantitative PCR and immunohistochemical assays. The biological roles of KDM4A were evaluated using wound-healing assays and an in vivo metastasis model. The Chromatin Immunoprecipitation (ChIP)-qPCR assay was used to determine the role of KDM4A in Notch1 regulation.ResultsHere, we screened that targeting KDM4A could induce notable cell growth suppression. KDM4A is required for the growth and progression of Bca cells. High KDM4A enhances tumor migration abilities and in vivo lung metastasis. Bioinformatic analysis suggested that KDM4A was highly expressed in tumors and high KDM4A correlates with poor survival outcomes. KDM4A activates Notch1 expressions via directly binding to the promoters and demethylating H3K9me3 modifications. KDM4A inhibition reduces expressions of a list of Notch1 downstream targets, and ectopic expressions of ICN1 could restore the corresponding levels. KDM4A relies on Notch1 signaling to maintain cell growth, migration and self-renewal capacities. Lastly, we divided a panel of cell lines into KDM4A^high and KDM4A^low groups. Targeting Notch1 using specific LY3039478 could efficiently suppress cell growth and colony formation abilities of KDM4A^high Bca.ConclusionTaken together, KDM4A could drive Bca progression via triggering the activation of Notch1 pathway by decreasing H3K9me3 levels, highlighting a promising therapeutic target for Bca.