GPER-induced signaling is essential for the survival of breast cancer stem cells.
ABSTRACT: G protein-coupled estrogen receptor-1 (GPER), a member of the G protein-coupled receptor (GPCR) superfamily, mediates estrogen-induced proliferation of normal and malignant breast epithelial cells. However, its role in breast cancer stem cells (BCSCs) remains unclear. Here we showed greater expression of GPER in BCSCs than non-BCSCs of three patient-derived xenografts of ER- /PR+ breast cancers. GPER silencing reduced stemness features of BCSCs as reflected by reduced mammosphere forming capacity in vitro, and tumor growth in vivo with decreased BCSC populations. Comparative phosphoproteomics revealed greater GPER-mediated PKA/BAD signaling in BCSCs. Activation of GPER by its ligands, including tamoxifen (TMX), induced phosphorylation of PKA and BAD-Ser118 to sustain BCSC characteristics. Transfection with a dominant-negative mutant BAD (Ser118Ala) led to reduced cell survival. Taken together, GPER and its downstream signaling play a key role in maintaining the stemness of BCSCs, suggesting that GPER is a potential therapeutic target for eradicating BCSCs.
Project description:Cancer stem cells (CSCs) are considered the roots of cancer metastasis and recurrence (CSCs), due in part to their self-renewal and therapy resistance properties. However, the underlying mechanisms for the regulation of CSC stemness are poorly understood. Recently, increasing evidence shows that long non-coding RNAs (lncRNAs) are critical regulators for cancer cell function in various malignancies including breast cancer, but how lncRNAs regulate the function of breast cancer stem cells (BCSCs) remains to be determined. Herein, using lncRNA/mRNA microarray assays, a novel lncRNA (named lnc030) is identified, which is highly expressed in BCSCs in vitro and in vivo, as a pivotal regulator in maintaining BCSC stemness and promoting tumorigenesis. Mechanistically, lnc030 cooperates with poly(rC) binding protein 2(PCBP2) to stabilize squalene epoxidase (SQLE) mRNA, resulting in an increase of cholesterol synthesis. The increased cholesterol in turn actives PI3K/Akt signaling, which governs BCSC stemness. In summary, these findings demonstrate that a new, lnc030-based mechanism for regulating cholesterol synthesis and stemness properties of BCSCs. The lnc030-SQLE-cholesterol synthesis pathway may serve as an effective therapeutic target for BCSC elimination and breast cancer treatment.
Project description:Breast cancers are thought to be organized hierarchically with a small number of breast cancer stem cells (BCSCs) able to regrow a tumor while their progeny lack this ability. Recently, several groups reported enrichment for BCSCs when breast cancers were subjected to classic anticancer treatment. However, the underlying mechanisms leading to this enrichment are incompletely understood. Using non-BCSCs sorted from patient samples, we found that ionizing radiation reprogrammed differentiated breast cancer cells into induced BCSCs (iBCSCs). iBCSCs showed increased mammosphere formation, increased tumorigenicity, and expressed the same stemness-related genes as BCSCs from nonirradiated samples. Reprogramming occurred in a polyploid subpopulation of cells, coincided with re-expression of the transcription factors Oct4, sex determining region Y-box 2, Nanog, and Klf4, and could be partially prevented by Notch inhibition. We conclude that radiation may induce a BCSC phenotype in differentiated breast cancer cells and that this mechanism contributes to increased BCSC numbers seen after classic anticancer treatment.
Project description:Cancer stem cells (CSCs) are critical for cancer progression and chemoresistance. How lipid metabolism regulates CSCs and chemoresistance remains elusive. Here, we demonstrate that JAK/STAT3 regulates lipid metabolism, which promotes breast CSCs (BCSCs) and cancer chemoresistance. Inhibiting JAK/STAT3 blocks BCSC self-renewal and expression of diverse lipid metabolic genes, including carnitine palmitoyltransferase 1B (CPT1B), which encodes the critical enzyme for fatty acid ?-oxidation (FAO). Moreover, mammary-adipocyte-derived leptin upregulates STAT3-induced CPT1B expression and FAO activity in BCSCs. Human breast-cancer-derived data suggest that the STAT3-CPT1B-FAO pathway promotes cancer cell stemness and chemoresistance. Blocking FAO and/or leptin re-sensitizes them to chemotherapy and inhibits BCSCs in mouse breast tumors in vivo. We identify a critical pathway for BCSC maintenance and breast cancer chemoresistance.
Project description:Triple negative breast cancer (TNBC), an aggressive subtype of breast cancer, display poor prognosis and exhibit resistance to conventional therapies, partly due to an enrichment in breast cancer stem cells (BCSCs). Here, we investigated the role of the cyclooxygenase-2 (COX-2), a downstream target of TGF?, in regulating BCSCs in TNBC. Bioinformatics analysis revealed that COX-2 is highly expressed in TNBC and that its expression correlated with poor survival outcome in basal subtype of breast cancer. We also found TGF?-mediated COX-2 expression to be Smad3-dependent and to be required for BCSC self-renewal and expansion in TNBCs. Knocking down COX-2 expression strikingly blocked TGF?-induced tumorsphere formation and TGF?-induced enrichment of the two stem-like cell populations, CD24lowCD44high and ALDH+ BCSCs. Blocking COX-2 activity, using a pharmacological inhibitor also prevented TGF?-induced BCSC self-renewal. Moreover, we found COX-2 to be required for TGF?-induced expression of mesenchymal and basal breast cancer markers. In particular, we found that TGF?-induced expression of fibronectin plays a central role in TGF?-mediated breast cancer stemness. Together, our results describe a novel role for COX-2 in mediating the TGF? effects on BCSC properties and imply that targeting the COX-2 pathway may prove useful for the treatment of TNBC by eliminating BCSCs.
Project description:Background:It has been widely reported that breast cancer aggressiveness may be driven by breast cancer stem cells (BCSCs). BCSCs display stemness properties that include self-renewal, tumourigenicity and pluripotency. The regulation of gene expression may have important roles in BCSC stemness and aggressiveness. Thus, the aim of this study was to examine the stemness and aggressiveness gene expression profile of BCSCs compared to MCF-7 and MDA-MB-231 breast cancer cells. Methods:Human ALDH1+ BCSCs were grown in serum-free Dulbecco's Modified Eagle Medium (DMEM)/F12, while MCF-7 and MDA-MB-231 were cultured in DMEM supplemented with 10% foetal bovine serum under standard conditions. Total RNA was extracted using the Tripure Isolation Reagent. The relative mRNA expressions of OCT4, ALDH1A1 and CD44 associated with stemness as well as TGF-?1, T?R1, ER?1 and MnSOD associated with aggressiveness in BCSCs and MCF-7 cells were determined using the quantitative real-time PCR (qRT-PCR). Results:The mRNA expressions of OCT4 (5.19-fold ± 0.338; P = 0.001), ALDH1A1 (3.67-fold ± 0.523; P = 0.006), CD44 (2.65-fold ± 0.307; P = 0.006), TGF-?1 (22.89-fold ± 6.840; P = 0.015), T?R1 (3.74-fold ± 1.446; P = 0.045) and MnSOD (4.6-fold ± 1.096; P = 0.014) were higher in BCSCs than in MCF-7 but were almost similar to MDA-MB-231 cells. In contrast, the ER?1 expression of BCSCs (0.97-fold ± 0.080; P = 0.392) was similar to MCF-7 cells, indicating that BSCSs are oestrogen-dependent breast cancer cells. Conclusion:The oestrogen-dependent BCSCs express stemness and aggressiveness genes at a higher level compared to oestrogen-dependent MCF-7 but are almost similar to oestrogen-independent MDA-MB-231 cells.
Project description:Breast cancer patients often suffer from disease relapse and metastasis due to the presence of breast cancer stem-like cells (BCSCs). Numerous studies have reported that high levels of inflammatory factors, including tumor necrosis factor alpha (TNF-?), promote BCSCs. However, the mechanism by which TNF-? promotes BCSCs is unclear. In this study, we demonstrate that TNF-? up-regulates TAZ, a transcriptional co-activator promoting BCSC self-renewal capacity in human breast cancer cell lines. Depletion of TAZ abrogated the increase in BCSCs mediated by TNF-?. TAZ is induced by TNF-? through the non-canonical NF-?B pathway, and our findings suggest that TAZ plays a crucial role in inflammatory factor-promoted breast cancer stemness and could serve as a promising therapeutic target.
Project description:Breast cancer stem cells (BCSCs) are the minor population of breast cancer (BC) cells that exhibit several phenotypes such as migration, invasion, self-renewal, and chemotherapy as well as radiotherapy resistance. Recently, BCSCs have been more considerable due to their capacity for recurrence of tumors after treatment. Recognition of signaling pathways and molecular mechanisms involved in stemness phenotypes of BCSCs could be effective for discovering novel treatment strategies to target BCSCs. This review introduces BCSC markers, their roles in stemness phenotypes, and the dysregulated signaling pathways involved in BCSCs such as mitogen-activated protein (MAP) kinase, PI3K/Akt/nuclear factor kappa B (NF?B), TGF-?, hedgehog (Hh), Notch, Wnt/?-catenin, and Hippo pathway. In addition, this review presents recently discovered molecular mechanisms implicated in chemotherapy and radiotherapy resistance, migration, metastasis, and angiogenesis of BCSCs. Finally, we reviewed the role of microRNAs (miRNAs) in BCSCs as well as several other therapeutic strategies such as herbal medicine, biological agents, anti-inflammatory drugs, monoclonal antibodies, nanoparticles, and microRNAs, which have been more considerable in the last decades.
Project description:BACKGROUND: Breast cancer stem cells (BCSCs) are the source of breast tumors. Compared with other cancer cells, cancer stem cells show high resistance to both chemotherapy and radiotherapy. Targeting of BCSCs is thus a potentially promising and effective strategy for breast cancer treatment. Differentiation therapy represents one type of cancer stem-cell-targeting therapy, aimed at attacking the stemness of cancer stem cells, thus reducing their chemo- and radioresistance. In a previous study, we showed that down-regulation of CD44 sensitized BCSCs to the anti-tumor agent doxorubicin. This study aimed to determine if CD44 knockdown caused BCSCs to differentiate into breast cancer non-stem cells (non-BCSCs). METHODS: We isolated a breast cancer cell population (CD44+CD24- cells) from primary cultures of malignant breast tumors. These cells were sorted into four sub-populations based on their expression of CD44 and CD24 surface markers. CD44 knockdown in the BCSC population was achieved using small hairpin RNA lentivirus particles. The differentiated status of CD44 knock-down BCSCs was evaluated on the basis of changes in CD44+CD24- phenotype, tumorigenesis in NOD/SCID mice, and gene expression in relation to renewal status, metastasis, and cell cycle in comparison with BCSCs and non-BCSCs. RESULTS: Knockdown of CD44 caused BCSCs to differentiate into non-BCSCs with lower tumorigenic potential, and altered the cell cycle and expression profiles of some stem cell-related genes, making them more similar to those seen in non-BCSCs. CONCLUSIONS: Knockdown of CD44 is an effective strategy for attacking the stemness of BCSCs, resulting in a loss of stemness and an increase in susceptibility to chemotherapy or radiation. The results of this study highlight a potential new strategy for breast cancer treatment through the targeting of BCSCs.
Project description:PURPOSE:Breast cancer stem cells (BCSCs) contribute to the initiation, development, and recurrence of breast carcinomas. ?1,4-Galactosyltransferase V (B4GalT5), which catalyzes the addition of galactose to GlcNAc?1-4Man of N-glycans, is involved in embryogenesis. However, its role in the modulation of BCSCs remains unknown. Materials and Methods:The relationship between B4GalT5 and breast cancer stemness was investigated by online clinical databases and immunohistochemistry analysis. Mammosphere formation, fluorescence-activated cell sorting (FACS), and in-vivo assays were used to evaluate B4GalT5 expression in BCSCs and its effect on BCSCs. B4GalT5 regulation of Wnt/?-catenin signaling was examined by immunofluorescence and Ricinus communis agglutinin I pull-down assays. Cell surface biotinylation and FACS assays were performed to assess the association of cell surface B4GalT5 and BCSCs. RESULTS:B4GalT5, but not other B4GalTs, was highly correlated with BCSC markers and poor prognosis. B4GalT5 significantly increased the stem cell marker aldehyde dehydrogenase 1A1 (ALDH1A1) and promoted the production of CD44+CD24-/low cells and the formation of mammospheres. Furthermore, B4GalT5 overexpression resulted in dramatic tumor growth in vivo. Mechanistically, B4GalT5 modified and protected Frizzled-1 from degradation via the lysosomal pathway, promoting Wnt/?-catenin signaling which was hyperactivated in BCSCs. B4GalT5, located on the surface of a small subset of breast carcinoma cells, was not responsible for the stemness of BCSCs. CONCLUSION:B4GalT5 modulates the stemness of breast cancer through glycosylation modification to stabilize Frizzled-1 and activate Wnt/?-catenin signaling independent of its cell surface location. Our studies highlight a previously unknown role of B4GalT5 in regulating the stemness of breast cancer and provide a potential drug target for anticancer drug development.
Project description:BACKGROUND:Long noncoding RNAs (lncRNAs) are emerging as crucial contributors to the development of breast cancer and are involved in the stemness regulation of breast cancer stem cells (BCSCs). LncRNAs are closely associated with the prognosis of breast cancer patients. It is critical to identify BCSC-related lncRNAs with prognostic value in breast cancer. METHODS:A co-expression network of BCSC-related mRNAs-lncRNAs from The Cancer Genome Atlas (TCGA) was constructed. Univariate and multivariate Cox proportional hazards analyses were used to identify a stemness risk model with prognostic value. Kaplan-Meier analysis, univariate and multivariate Cox regression analyses and receiver operating characteristic (ROC) curve analysis were performed to validate the risk model. Principal component analysis (PCA) and Gene Set Enrichment Analysis (GSEA) functional annotation were conducted to analyze the risk model. RESULTS:In this study, BCSC-related lncRNAs in breast cancer were identified. We evaluated the prognostic value of these BCSC-related lncRNAs and eventually obtained a prognostic risk model consisting of 12 BCSC-related lncRNAs (Z68871.1, LINC00578, AC097639.1, AP003119.3, AP001207.3, LINC00668, AL122010.1, AC245297.3, LINC01871, AP000851.2, AC022509.2 and SEMA3B-AS1). The risk model was further verified as a novel independent prognostic factor for breast cancer patients based on the calculated risk score. Moreover, based on the risk model, the low- risk and high-risk groups displayed different stemness statuses. CONCLUSIONS:These findings suggested that the 12 BCSC-related lncRNA signature might be a promising prognostic factor for breast cancer and can promote the management of BCSC-related therapy in clinical practice.