技术资料

Little is known about the origin of basal-like breast cancers,an aggressive disease that is highly similar to BRCA1-mutant breast cancers. p63 family proteins that are structurally related to the p53 suppressor protein are known to function in stem cell regulation and stratified epithelia development in multiple tissues,and p63 expression may be a marker of basal-like breast cancers. Here we report that ΔNp63 isoforms of p63 are transcriptional targets for positive regulation by BRCA1. Our analyses of breast cancer tissue microarrays and BRCA1-modulated breast cancer cell lines do not support earlier reports that p63 is a marker of basal-like or BRCA1 mutant cancers. Nevertheless,we found that BRCA1 interacts with the specific p63 isoform ΔNp63γ along with transcription factor isoforms AP-2α and AP-2γ. BRCA1 required ΔNp63γ and AP-2γ to localize to an intronic enhancer region within the p63 gene to upregulate transcription of the ΔNp63 isoforms. In mammary stem/progenitor cells,siRNA-mediated knockdown of ΔNp63 expression resulted in genomic instability,increased cell proliferation,loss of DNA damage checkpoint control,and impaired growth control. Together,our findings establish that transcriptional upregulation of ΔNp63 proteins is critical for BRCA1 suppressor function and that defects in BRCA1-ΔNp63 signaling are key events in the pathogenesis of basal-like breast cancer. View Publication

Mammary cancer stem cells (MaCSCs) have been identified as a rare population of cells capable of self-renewal to drive mammary tumorigenesis and metastasis. Nevertheless,relatively little is known about the intracellular signaling pathways regulating self-renewal and metastatic activities of MaCSCs in vivo. Using a recently developed breast cancer mouse model with focal adhesion kinase (FAK) deletion in mammary tumor cells (MFCKO-MT mice),here we present evidence suggesting a compensatory function of Pyk2,a FAK-related kinase,in the regulation of MaCSCs and metastasis in these mice. Increased expression of Pyk2 was found selectively in pulmonary metastatic nodules of MFCKO-MT mice,and its inhibition significantly reduced mammary tumor development and metastasis in these mice. Consistent with the idea of metastasis driven by MaCSCs,we detected selective up-regulation of Pyk2 in MaCSCs,but not bulk mammary tumor cells,of primary tumors developed in MFCKO-MT mice. We further showed that inhibition of Pyk2 in FAK-null MaCSCs significantly decreased their tumorsphere formation and migration in vitro as well as self-renewal,tumorigenicity,and metastatic activity in vivo. Last,we identified PI3K/Akt signaling as a major mediator of FAK regulation of MaCSCs as well as a target for the compensatory function of Pyk2 in FAK-null MaCSCs. Together,these results further advance our understanding of FAK and its related tyrosine kinase Pyk2 in regulation of MaCSCs in breast cancer and suggest that pharmaceutically targeting these kinases may hold promise as a novel treatment for the disease by targeting and eradicating MaCSCs. View Publication

We have used in vitro and mouse xenograft models to examine the interaction between breast cancer stem cells (CSC) and bone marrow-derived mesenchymal stem cells (MSC). We show that both of these cell populations are organized in a cellular hierarchy in which primitive aldehyde dehydrogenase expressing mesenchymal cells regulate breast CSCs through cytokine loops involving IL6 and CXCL7. In NOD/SCID mice,labeled MSCs introduced into the tibia traffic to sites of growing breast tumor xenografts where they accelerated tumor growth by increasing the breast CSC population. With immunochemistry,we identified MSC-CSC niches in these tumor xenografts as well as in frozen sections from primary human breast cancers. Bone marrow-derived MSCs may accelerate human breast tumor growth by generating cytokine networks that regulate the CSC population. View Publication

OBJECTIVE: The aim of this narrative review was to evaluate the role of cancer stem cells (CSCs) and sex steroids in the pathophysiology of human breast cancer. METHODS: A key-word search was performed using the Scopus database. Preference was given to studies using human cells and tissues. RESULTS: Long-term estrogen-progestin hormone therapy is known to increase breast cancer risk,although the mechanisms are poorly understood. In the last few years,it has become clear that many human breast cancers contain CSCs,which may be responsible for much of the tumor's malignant behavior. Very recently,the impact of estrogen,progesterone,and progestins on breast CSCs and their progeny has been studied and clarified. Most breast CSCs are estrogen receptor negative and progesterone receptor negative,although some intermediary progenitor forms have hormone receptors,especially progesterone receptor. Most mature human breast cancer cellsare estrogen receptor positive and can thus be stimulated by estrogen. Breast CSCs usually elaborate CD44+,CD24j/low and/or ALDEFLUOR+ cell markers and are lineage markers negative. One of the main roles of progesterone and progestin seems to be on certain breast cancer stem intermediate forms,inducing them to revert back to a more primitive breast CSC form. CONCLUSIONS: As the pathophysiology of human breast CSC is clarified,it is probable that this will lead to novel,effective breast cancer treatments and,perhaps,new breast cancer preventive agents. This research may also lead to safer hormone therapy regimens. View Publication

Transplantation studies have demonstrated the existence of mammary progenitor cells with the ability to self-renew and regenerate a functional mammary gland. Although these progenitors are the likely targets for oncogenic transformation,correlating progenitor populations with certain oncogenic stimuli has been difficult. Cyclin D1 is required for lobuloalveolar development during pregnancy and lactation as well as MMTV-ErbB2- but not MMTV-Wnt1-mediated tumorigenesis. Using a kinase-deficient cyclin D1 mouse,we identified two functional mammary progenitor cell populations,one of which is the target of MMTV-ErbB2. Moreover,cyclin D1 activity is required for the self-renewal and differentiation of mammary progenitors because its abrogation leads to a failure to maintain the mammary epithelial regenerative potential and also results in defects in luminal lineage differentiation. View Publication

The molecular mechanisms governing breast tumor cellular self-renewal contribute to breast cancer progression and therapeutic resistance. The ErbB2 oncogene is overexpressed in approximately 30% of human breast cancers. c-Jun,the first cellular proto-oncogene,is overexpressed in human breast cancer. However,the role of endogenous c-Jun in mammary tumor progression is unknown. Herein,transgenic mice expressing the mammary gland-targeted ErbB2 oncogene were crossed with c-jun(f/f) transgenic mice to determine the role of endogenous c-Jun in mammary tumor invasion and stem cell function. The excision of c-jun by Cre recombinase reduced cellular migration,invasion,and mammosphere formation of ErbB2-induced mammary tumors. Proteomic analysis identified a subset of secreted proteins (stem cell factor (SCF) and CCL5) induced by ErbB2 expression that were dependent upon endogenous c-Jun expression. SCF and CCL5 were identified as transcriptionally induced by c-Jun. CCL5 rescued the c-Jun-deficient breast tumor cellular invasion phenotype. SCF rescued the c-Jun-deficient mammosphere production. Endogenous c-Jun thus contributes to ErbB2-induced mammary tumor cell invasion and self-renewal. View Publication

Human breast tumors contain a breast cancer stem cell (BCSC) population with properties reminiscent of normal stem cells. We found 37 microRNAs that were differentially expressed between human BCSCs and nontumorigenic cancer cells. Three clusters,miR-200c-141,miR-200b-200a-429,and miR-183-96-182 were downregulated in human BCSCs,normal human and murine mammary stem/progenitor cells,and embryonal carcinoma cells. Expression of BMI1,a known regulator of stem cell self-renewal,was modulated by miR-200c. miR-200c inhibited the clonal expansion of breast cancer cells and suppressed the growth of embryonal carcinoma cells in vitro. Most importantly,miR-200c strongly suppressed the ability of normal mammary stem cells to form mammary ducts and tumor formation driven by human BCSCs in vivo. The coordinated downregulation of three microRNA clusters and the similar functional regulation of clonal expansion by miR-200c provide a molecular link that connects BCSCs with normal stem cells. View Publication

Proliferation in the nonpregnant human breast is highest in the luteal phase of the menstrual cycle when serum progesterone levels are high,and exposure to progesterone analogues in hormone replacement therapy is known to elevate breast cancer risk,yet the proliferative effects of progesterone in the human breast are poorly understood. In a model of normal human breast,we have shown that progesterone increased incorporation of 5-bromo-2'-deoxyuridine and increased cell numbers by activation of pathways involved in DNA replication licensing,including E2F transcription factors,chromatin licensing and DNA replication factor 1 (Cdt1),and the minichromosome maintenance proteins and by increased expression of proteins involved in kinetochore formation including Ras-related nuclear protein (Ran) and regulation of chromosome condensation 1 (RCC1). Progenitor cells competent to give rise to both myoepithelial and luminal epithelial cells were increased by progesterone,showing that progesterone influences epithelial cell lineage differentiation. Therefore,we have demonstrated that progesterone augments proliferation of normal human breast cells by both activating DNA replication licensing and kinetochore formation and increasing bipotent progenitor numbers. View Publication

PURPOSE: The existence of tumor-initiating cells in breast cancer has profound implications for cancer therapy. In this study,we investigated the sensitivity of tumor-initiating cells isolated from human epidermal growth factor receptor type 2 (HER2)-overexpressing carcinoma cell lines to trastuzumab,a compound used for the targeted therapy of breast cancer. EXPERIMENTAL DESIGN: Spheres were analyzed by indirect immunofluorescence for HER2 cell surface expression and by real-time PCR for HER2 mRNA expression in the presence or absence of the Notch1 signaling inhibitor (GSI) or Notch1 small interfering RNA. Xenografts of HER2-overexpressing breast tumor cells were treated with trastuzumab or doxorubicin. The sphere-forming efficiency (SFE) and serial transplantability of tumors were assessed. RESULTS: In HER2-overexpressing carcinoma cell lines,cells with tumor-initiating cell properties presented increased HER2 levels compared with the bulk cell population without modification in HER2 gene amplification. HER2 levels were controlled by Notch1 signaling,as shown by the reduction of HER2 cell surface expression and lower SFE following gamma-secretase inhibition or Notch1 specific silencing. We also show that trastuzumab was able to effectively target tumor-initiating cells of HER2-positive carcinoma cell lines,as indicated by the significant decrease in SFE and the loss of serial transplantability,following treatment of HER2-overexpressing xenotransplants. CONCLUSIONS: Here,we provide evidence for the therapeutic efficacy of trastuzumab in debulking and in targeting tumor-initiating cells of HER2-overexpressing tumors. We also propose that Notch signaling regulates HER2 expression,thereby representing a critical survival pathway of tumor-initiating cells. View Publication