Microarray-based analysis of microRNA expression in breast cancer stem cells

Background

This study aimed to determine the miRNA profile in breast cancer stem cells (BCSCs) and to explore the functions of characteristic BCSC miRNAs.

Methods

We isolated ESA⁺CD44⁺CD24^-/low BCSCs from MCF-7 cells using fluorescence-activated cell sorting (FACS). A human breast cancer xenograft assay was performed to validate the stem cell properties of the isolated cells, and microarray analysis was performed to screen for BCSC-related miRNAs. These BCSC-related miRNAs were selected for bioinformatic analysis and target prediction using online software programs.

Results

The ESA⁺CD44⁺CD24^-/low cells had up to 100- to 1000-fold greater tumor-initiating capability than the MCF-7 cells. Tumors initiated from the ESA⁺CD44⁺CD24^-/low cells were included of luminal epithelial and myoepithelial cells, indicating stem cell properties. We also obtained miRNA profiles of ESA⁺CD44⁺CD24^-/low BCSCs. Most of the possible targets of potential tumorigenesis-related miRNAs were oncogenes, anti-oncogenes or regulatory genes.

Conclusions

We identified a subset of miRNAs that were differentially expressed in BCSCs, providing a starting point to explore the functions of these miRNAs. Evaluating characteristic BCSC miRNAs represents a new method for studying breast cancer-initiating cells and developing therapeutic strategies aimed at eradicating the tumorigenic subpopulation of cells in breast cancer.     

乳腺癌干细胞研究进展

乳腺癌干细胞与乳腺癌的放疗抵抗性和化疗耐受性有关,特定表面分子标志与不同乳腺癌分子分型相关.目前,针对乳腺癌干细胞的抑制剂正逐步进入临床试验研究并在临床上使用.乳腺癌干细胞同时也是转移的源泉,它和循环肿瘤细胞之间存在一些共同点.总之,探究乳腺癌干细胞的各种特性有利于开发其在临床的应用.     

Cord blood stem cells revert glioma stem cell EMT by down regulating transcriptional activation of Sox2 and Twist1

The dynamic nature of cancer stem cells that underlie metastasis or their ability to switch between different cellular identities, as in EMT and MET, has profound implications for cancer therapy. The functional relationship between molecules involved in cancer cell stemness and metastasis is not clear. In this regard, our studies on hGBM tissue grade IV specimens showed significant expression of Twist1 and Sox2, known mesenchymal and stemness related markers, respectively, indicating their association with glial tumor genesis and metastasis. The glioma stem cells obtained from CD133+ cells demonstrated increased expression of Twist1 and Sox2 accompanied by significant increase in the mesenchymal markers such as N-cadherin, vimentin and β-catenin. Our studies on glioma stem cells treatment with human umbilical cord blood derived- mesenchymal stem cells, showed down regulation of Twist1 and Sox2 proteins, apart from other mesenchymal stem cell markers. Based on the in vitro experiments and in vivo intracranial xenograft mouse model studies, we elucidated the potential therapeutic role of hUCBSC in suppressing glioma cancer stemness by the induction of MET.     

MicroRNA与乳腺癌干细胞

乳腺癌干细胞是导致乳腺癌复发、转移和耐药的根源之一。microRNA(miRNAs)是一类小分子非编码RNA,可与靶mRNA的3’UTR区域结合而导致该mRNA分子的翻译受到抑制,参与多种生物功能的调节。最近研究发现,miRNAs参与乳腺癌干细胞的分化、自我更新等生物学特性的调控。MiRNAs可以作为乳腺癌干细胞研究的一个新的切入点。本文就近年来该方面的研究进展做简要综述。     

Targeting breast cancer stem cells

The cancer stem cell (CSC) hypothesis postulates that tumors are maintained by a self‐renewing CSC population that is also capable of differentiating into non‐self‐renewing cell populations that constitute the bulk of the tumor. Although, the CSC hypothesis does not directly address the cell of origin of cancer, it is postulated that tissue‐resident stem or progenitor cells are the most common targets of transformation. Clinically, CSCs are predicted to mediate tumor recurrence after chemo‐ and radiation‐therapy due to the relative inability of these modalities to effectively target CSCs. If this is the case, then CSC must be efficiently targeted to achieve a true cure. Similarities between normal and malignant stem cells, at the levels of cell‐surface proteins, molecular pathways, cell cycle quiescence, and microRNA signaling present challenges in developing CSC‐specific therapeutics. Approaches to targeting CSCs include the development of agents targeting known stem cell regulatory pathways as well as unbiased high‐throughput siRNA or small molecule screening. Based on studies of pathways present in normal stem cells, recent work has identified potential “Achilles heals” of CSC, whereas unbiased screening provides opportunities to identify new pathways utilized by CSC as well as develop potential therapeutic agents. Here, we review both approaches and their potential to effectively target breast CSC.     

Forced expression of Sox21 inhibits Sox2 and induces apoptosis in human glioma cells

Numerous studies support a role for Sox2 to keep stem cells and progenitor cells in an immature and proliferative state. Coexpression of Sox2 and GFAP has been found in regions of the adult brain where neural stem cells are present and in human glioma cells. In our study, we have investigated the roles of Sox2 and its counteracting partner Sox21 in human glioma cells. We show for the first time that Sox21 is expressed in both primary glioblastoma and in human glioma cell lines. We found that coexpression of Sox2, GFAP and Sox21 was mutually exclusive with expression of fibronectin. Our result suggests that glioma consists of at least two different cell populations: Sox2⁺/GFAP⁺/Sox21⁺/FN^? and Sox2^?/GFAP^?/Sox21^?/FN⁺. Reduction of Sox2 expression by using siRNA against Sox2 or by overexpressing Sox21 using a tetracycline‐regulated expression system (Tet‐on) caused decreased GFAP expression and a reduction in cell number due to induction of apoptosis. We suggest that Sox21 can negatively regulate Sox2 in glioma. Our findings imply that Sox2 and Sox21 may be interesting targets for the development of novel glioma therapy.     

乳腺癌干细胞多药耐药基因的表达及意义

Objective:To approach the expressions of MDR1 and BCRP in breast cancer stem cells and differentiated cells.Methods:The breast cancer stem calls were separated from human breast cancer primary tissues and MCF-7 by flow cytometry.Then we measured the expressions of MDR1 and BCRP with different subset cells by Realtime-PCR.Results:Contrasted with breast cancer differentiated cells,the expressions of MDR1 and BCRP in breast cancer stem calls were higher (P＜0.01),and the proportion of stem cells rose after chemotherapy (P＜0.01).Conclusion:Contrasted with breast cancer differentiated cells,breast cancer stem cells have stronger ability of clrug-resistanca with higher level of multi-drug resistance genes,and it is one of key points for chemotherapy failure of breast cancer.     

Ansamycin antibiotics inhibit Akt activation and cyclin D expression in breast cancer cells that overexpress HER2

Ansamycin antibiotics, such as 17-allylaminogeldanamycin (17-AAG), bind to Hsp90 and regulate its function, resulting in the proteasomal degradation of a subset of signaling proteins that require Hsp90 for conformational maturation. HER2 is a very sensitive target of these drugs. Ansamycins cause RB-dependent G1 arrest that is associated with loss of D-cyclins via a PI3 kinase, Akt dependent pathway. Downregulation of D-cyclin was due, in part, to loss of Akt expression in response to drug. Moreover, in HER2 overexpressing breast cancer cells, 17-AAG caused rapid inhibition of Akt activity prior to any change in Akt protein. Ansamycins caused rapid degradation of HER2 and a concomitant loss in HER3 associated PI3 kinase activity. This led to a loss of Akt activity, dephosphorylation of Akt substrates, and loss of D-cyclin expression. Introduction into cells of a constitutively membrane bound form of PI3 kinase prevented the effects of the drug on Akt activity and D-cyclins. Thus, in breast cancer cells with high HER2, Akt activation by HER2/HER3 heterodimers is required for D-cyclin expression. In murine xenograft models, non-toxic doses of 17-AAG markedly reduced the expression of HER2 and phosphorylation of Akt and inhibited tumor growth. Thus, pharmacological inhibition of Akt activation is achievable with ansamycins and may be useful for the treatment of HER2 driven tumors.     

Cancer stem cells in breast cancer and metastasis

Independent studies have shown that in node negative breast cancer patients less than 71 years, the proliferation marker mitotic activity index (MAI) is the strongest, most well reproducible prognosticator and chemotherapy success predictor. The MAI overshadows the prognostic value of tubule formation, nuclear atypia and thereby grade. An often used crude mitotic impression is much less prognostic than the MAI; strict adherence to the MAI protocol is therefore important. The prognostic value of the MAI is age dependent: although patients with a MAI ≥ 10 always have a poor prognosis irrespective of age, a low MAI (<10) loses its favourable prognostic association in women >70 years. PPH3 counts are prognostically stronger than the MAI, and markers such as Cyclin-B and E2FR are promising, but must be validated. Compared with commercial prognostic gene expression signatures, the MAI is at least as strong prognostically, has far fewer false positive results and as such should be included as an independent feature in any node negative breast cancer pathology report.     

乳腺癌干细胞研究进展

肿瘤不仅是基因病,也可能是一种干细胞疾病。肿瘤干细胞的发现将对现有的肿瘤发病机制、诊断及治疗的认识产生重要影响,给传统治疗带来极大挑战。现综述目前乳腺癌干细胞的发现、分离、可能相关的信号分子机制、内分泌调控特征及临床应用前景。     

乳腺癌干细胞多药耐药基因的表达及意义

目的：探讨乳腺癌干细胞和乳腺癌分化细胞多药耐药基因MDR1、BCRP的表达和意义。方法：采用流式细胞分选技术从人乳腺癌原代组织和MCF-7细胞中分离出乳腺癌干细胞,实时PCR技术测定不同亚群细胞的MDR1和BCRP表达情况。结果：与乳腺癌分化细胞相比,乳腺癌干细胞MDR1和BCRP的表达明显增强（P〈0.01）,并且在化疗后干细胞比例也明显增加（P〈0.01）。结论：和乳腺癌分化细胞相比,乳腺癌干细胞能通过高表达多药耐药基因具有更强的化疗耐药能力,是乳腺癌化疗失败和复发的关键因素之一。     

乳腺干细胞和乳腺癌干细胞研究现状

<正>干细胞是机体内具有自我更新和多向分化潜能的细胞群体,并能通过分化产生特定组织的成熟细胞,理论上一个干细胞可以发育成为完整的生物个体或组织器官[1]。关于干细胞的概念,目前最广泛接受的是,干细胞是可以进行对称和非对称分裂的未分化的细胞群:分裂发生时,一个干细胞产生两个子细胞,一个与母细胞完全一致,具有母细胞同样的特征;另一个细胞可以分化形成不同的成熟细胞株。     

Hippo-TAZ 信号通路在乳腺癌及乳腺癌干细胞中的作用

Hippo 信号通路在调节器官生长、组织再生、肿瘤发生、发展中起重要作用,而含有 PDZ 结合模序转录共激活因子（TAZ）是其下游核心转录因子,参与整个信号通路的调控。近年来,研究者发现TAZ 过表达与乳腺癌的发生、发展、预后都有着密切的关系。探讨 Hippo 信号通路中 TAZ 与乳腺癌及乳腺癌干细胞的关系,可为乳腺癌诊断和治疗提供新的思路。     

Silencing NOTCH signaling causes growth arrest in both breast cancer stem cells and breast cancer cells

Background:

Breast cancer stem cells (BCSCs) are characterized by high aldehyde dehydrogenase (ALDH) enzyme activity and are refractory to current treatment modalities, show a higher risk for metastasis, and influence the epithelial to mesenchymal transition (EMT), leading to a shorter time to recurrence and death. In this study, we focused on examination of the mechanism of action of a small herbal molecule, psoralidin (Pso) that has been shown to effectively suppress the growth of BSCSs and breast cancer cells (BCCs), in breast cancer (BC) models.

Methods:

ALDH⁻ and ALDH⁺ BCCs were isolated from MDA-MB-231 cells, and the anticancer effects of Pso were measured using cell viability, apoptosis, colony formation, invasion, migration, mammosphere formation, immunofluorescence, and western blot analysis.

Results:

Psoralidin significantly downregulated NOTCH1 signaling, and this downregulation resulted in growth inhibition and induction of apoptosis in both ALDH⁻ and ALDH⁺ cells. Molecularly, Pso inhibited NOTCH1 signaling, which facilitated inhibition of EMT markers (β-catenin and vimentin) and upregulated E-cadherin expression, resulting in reduced migration and invasion of both ALDH⁻ and ALDH⁺ cells.

Conclusion:

Together, our results suggest that inhibition of NOTCH1 by Pso resulted in growth arrest and inhibition of EMT in BCSCs and BCCs. Psoralidin appears to be a novel agent that targets both BCSCs and BCCs.     

CCL2 mediates cross-talk between cancer cells and stromal fibroblasts that regulates breast cancer stem cells

Cancer stem cells (CSC) play critical roles in cancer initiation, progression, and therapeutic refractoriness. Although many studies have focused on the genes and pathways involved in stemness, characterization of the factors in the tumor microenvironment that regulate CSCs is lacking. In this study, we investigated the effects of stromal fibroblasts on breast cancer stem cells. We found that compared with normal fibroblasts, primary cancer-associated fibroblasts (CAF) and fibroblasts activated by cocultured breast cancer cells produce higher levels of chemokine (C-C motif) ligand 2 (CCL2), which stimulates the stem cell-specific, sphere-forming phenotype in breast cancer cells and CSC self-renewal. Increased CCL2 expression in activated fibroblasts required STAT3 activation by diverse breast cancer-secreted cytokines, and in turn, induced NOTCH1 expression and the CSC features in breast cancer cells, constituting a cancer-stroma-cancer signaling circuit. In a xenograft model of paired fibroblasts and breast cancer tumor cells, loss of CCL2 significantly inhibited tumorigenesis and NOTCH1 expression. In addition, upregulation of both NOTCH1 and CCL2 was associated with poor differentiation in primary breast cancers, further supporting the observation that NOTCH1 is regulated by CCL2. Our findings therefore suggest that CCL2 represents a potential therapeutic target that can block the cancer-host communication that prompts CSC-mediated disease progression.