Primary breast cancer stem-like cells metastasise to bone, switch phenotype and acquire a bone tropism signature.
ABSTRACT: BACKGROUND: Bone metastases represent a common and severe complication in breast cancer, and the involvement of cancer stem cells (CSCs) in the promotion of bone metastasis is currently under discussion. Here, we used a human-in-mice model to study bone metastasis formation due to primary breast CSCs-like colonisation. METHODS: Primary CD44?CD24? breast CSCs-like were transduced by a luciferase-lentiviral vector and injected through subcutaneous and intracardiac (IC) routes in non-obese/severe-combined immunodeficient (NOD/SCID) mice carrying subcutaneous human bone implants. The CSCs-like localisation was monitored by in vivo luciferase imaging. Bone metastatic CSCs-like were analysed through immunohistochemistry and flow cytometry, and gene expression analyses were performed by microarray techniques. RESULTS: Breast CSCs-like colonised the human-implanted bone, resulting in bone remodelling. Bone metastatic lesions were histologically apparent by tumour cell expression of epithelial markers and vimentin. The bone-isolated CSCs-like were CD44?CD24? and showed tumorigenic abilities after injection in secondary mice. CD44?CD24? CSCs-like displayed a distinct bone tropism signature that was enriched in genes that discriminate bone metastases of breast cancer from metastases at other organs. CONCLUSION: Breast CSCs-like promote bone metastasis and display a CSCs-like bone tropism signature. This signature has clinical prognostic relevance, because it efficiently discriminates osteotropic breast cancers from tumour metastases at other sites.
Project description:We investigated the role of breast cancer stem-like cells (CSCs-like), isolated from primary tumor, in promoting bone metastases in a human-in-mice model. Luciferase-transduced CD44+CD24- breast CSCs-like were injected through subcutaneous (SC) and intracardiac (IC) route in nonobese/severe combined immunodeficient (NOD/SCID) mice carrying subcutaneous human bone implants. The implanted bone was viable, active and human neo-vascularization was present. By in vivo luciferase imaging, we monitored tumor growth and detected bone-localized breast CSCs-like, both after SC and IC injection. Bone metastatic lesions were histologically evident, and tumor cells expressed epithelial markers and vimentin. Bone metastatic cells isolated from bone implants showed a CD44-CD24+ phenotype and re-created tumors and bone metastases after injection in secondary mice. A “bone tropism” expression signature was found to distinguish bone-colonizing cells from parental CSCs-like and to persist at subsequent passages also in the absence of surrounding bone tissue. The bone tropism signature displayed significant enrichment in genes discriminating bone metastases of breast cancer from metastases at other organs. Our results demonstrate the ability of breast CSCs-like to promote bone metastasis and provide a CSCs-like bone tropism signature, with potential prognostic value. Overall design: C10 breast cancer stem-like cells (CSCs-like) were derived as mammospheres from a lobular-infiltrating breast carcinoma (ER+, HER2-). Samples are organized in the following groups: (i) Breast CSCs-like (C10, duplicate); (ii) Luciferase-transduced CSCs-like (C10L, simplicate); (iii) Bone-isolated C10L metastatic cells (C10-bone, duplicate) and subsequently (iv) grown in vitro as spheroids (C10-CSC, simplicate) or (v) re-grown in subcutaneous implants (C10-SC, duplicate).
Project description:We investigated the role of breast cancer stem-like cells (CSCs-like), isolated from primary tumor, in promoting bone metastases in a human-in-mice model. Luciferase-transduced CD44+CD24- breast CSCs-like were injected through subcutaneous (SC) and intracardiac (IC) route in nonobese/severe combined immunodeficient (NOD/SCID) mice carrying subcutaneous human bone implants. The implanted bone was viable, active and human neo-vascularization was present. By in vivo luciferase imaging, we monitored tumor growth and detected bone-localized breast CSCs-like, both after SC and IC injection. Bone metastatic lesions were histologically evident, and tumor cells expressed epithelial markers and vimentin. Bone metastatic cells isolated from bone implants showed a CD44-CD24+ phenotype and re-created tumors and bone metastases after injection in secondary mice. A “bone tropism” expression signature was found to distinguish bone-colonizing cells from parental CSCs-like and to persist at subsequent passages also in the absence of surrounding bone tissue. The bone tropism signature displayed significant enrichment in genes discriminating bone metastases of breast cancer from metastases at other organs. Our results demonstrate the ability of breast CSCs-like to promote bone metastasis and provide a CSCs-like bone tropism signature, with potential prognostic value. C10 breast cancer stem-like cells (CSCs-like) were derived as mammospheres from a lobular-infiltrating breast carcinoma (ER+, HER2-). Samples are organized in the following groups: (i) Breast CSCs-like (C10, duplicate); (ii) Luciferase-transduced CSCs-like (C10L, simplicate); (iii) Bone-isolated C10L metastatic cells (C10-bone, duplicate) and subsequently (iv) grown in vitro as spheroids (C10-CSC, simplicate) or (v) re-grown in subcutaneous implants (C10-SC, duplicate).
Project description:CD44/CD24 and ALDH1 are widely used cancer stem cell (CSC) markers in breast cancer. However, their expression is not always consistent even in the same subtype of breast cancer. Systematic comparison of their functions is still lacking. We investigated the expression of CD44, CD24 and ALDH1 in different subtypes of breast cancer cells, and explored their relationship with cancer progression. We defined a parameter CD44/CD24 ratio to present the expression level of CD44 and CD24 and found that high CD44/CD24 ratio and ALDH1+ are both indicators for cancer malignancy, but play different functions during tumor progression. High CD44/CD24 ratio is more related to cell proliferation and tumorigenesis, which is confirmed by mammosphere formation and tumorigenesis in xenotransplanted mice. ALDH1+ is a stronger indicator for cell migration and tumor metastasis. Suppression of CD44 and ALDH1 by siRNA led to decreased tumorigenicity and cell migration capacity. The combination of high CD44/CD24 ratio and ALDH1+ would be a more reliable way to characterize CSCs. Moreover, both high CD44/CD24 ratio and ALDH1+ were conserved during metastasis, from the primary tumors to the circulating tumor cells (CTCs) and the distant metastases, suggesting the significant value of these CSC markers in assisting cancer detection, prognostic evaluation, and even cancer therapeutics.
Project description:Cancer stem cells (CSCs) have recently been identified in leukaemia and solid tumours; however, the role of CSCs in metastasis remains poorly understood. This dearth of knowledge about CSCs and metastasis is due largely to technical challenges associated with the use of primary human cancer cells in pre-clinical models of metastasis. Therefore, the objective of this study was to develop suitable pre-clinical model systems for studying stem-like cells in breast cancer metastasis, and to test the hypothesis that stem-like cells play a key role in metastatic behaviour. We assessed four different human breast cancer cell lines (MDA-MB-435, MDA-MB-231, MDA-MB-468, MCF-7) for expression of prospective CSC markers CD44/CD24 and CD133, and for functional activity of aldehyde dehydrogenase (ALDH), an enzyme involved in stem cell self-protection. We then used fluorescence-activated cell sorting and functional assays to characterize differences in malignant/metastatic behaviour in vitro (proliferation, colony-forming ability, adhesion, migration, invasion) and in vivo (tumorigenicity and metastasis). Sub-populations of cells demonstrating stem-cell-like characteristics (high expression of CSC markers and/or high ALDH) were identified in all cell lines except MCF-7. When isolated and compared to ALDH(low)CD44(low/-) cells, ALDH(hi)CD44(+)CD24(-) (MDA-MB-231) and ALDH(hi)CD44(+)CD133(+) (MDA-MB-468) cells demonstrated increased growth (P < 0.05), colony formation (P < 0.05), adhesion (P < 0.001), migration (P < 0.001) and invasion (P < 0.001). Furthermore, following tail vein or mammary fat pad injection of NOD/SCID/IL2gamma receptor null mice, ALDH(hi)CD44(+)CD24(-) and ALDH(hi)CD44(+)CD133(+) cells showed enhanced tumorigenicity and metastasis relative to ALDH(low)CD44(low/-) cells (P < 0.05). These novel results suggest that stem-like ALDH(hi)CD44(+)CD24(-) and ALDH(hi)CD44(+)CD133(+) cells may be important mediators of breast cancer metastasis.
Project description:Breast cancer is a leading cause of cancer death in women, with the majority of these deaths caused by metastasis to distant organs. The most common site of breast cancer metastasis is the bone, which has been shown to provide a rich microenvironment that supports the migration and growth of breast cancer cells. Additionally, growing evidence suggests that breast cancer cells that do successfully metastasize have a stem-like phenotype including high activity of aldehyde dehydrogenase (ALDH) and/or a CD44+CD24- phenotype. In the current study, we tested the hypothesis that these ALDHhiCD44+CD24- breast cancer cells interact with factors in the bone secondary organ microenvironment to facilitate metastasis. Specifically, we focused on bone-derived osteopontin and its ability to promote the migration and stem-like phenotype of breast cancer cells. Our results indicate that bone-derived osteopontin promotes the migration, tumorsphere-forming ability and colony-forming ability of whole population and ALDHhiCD44+CD24- breast cancer cells in bone marrow-conditioned media (an ex vivo representation of the bone microenvironment) (p?0.05). We also demonstrate that CD44 and RGD-dependent cell surface integrins facilitate this functional response to bone-derived osteopontin (p?0.05), potentially through activation of WNK-1 and PRAS40-related pathways. Our findings suggest that soluble bone-derived osteopontin enhances the ability of breast cancer cells to migrate to the bone and maintain a stem-like phenotype within the bone microenvironment, and this may contribute to the establishment and growth of bone metastases.
Project description:Cancer stem-like cells (CSCs) are a subpopulation of cancer cells responsible for tumor growth, and recent evidence suggests that CSCs also contribute to cancer metastasis. However, the heterogeneity of CSCs in metastasis capacities is still unclear in breast cancer. Here we show that among the CD24-/CD44+ breast CSCs, a subset expressing the variant isoform of CD44 (CD44v) displays significantly higher capacity of lung metastasis than that expressing the standard CD44 isoform CD44s. Increasing or reducing the CD44v/CD44s ratio of breast cancer cells by regulating the expression of epithelial splicing regulatory protein 1 (ESRP1) leads to promotion or suppression of lung metastasis without influencing cancer cell stemness. Directly suppressing CD44v expression significantly alleviates the metastasis burden in lungs. Mechanically, CD44v, but not CD44s, responds to osteopontin (OPN) in the lung environment to enhance cancer cell invasiveness and promote lung metastasis. In clinical samples expression of ESRP1 and CD44v, rather than CD44s or total CD44, positively correlates with distant metastasis. Overall, our data identify a subset of metastatic breast CSCs characterized by CD44v expression, and suggest that CD44v and ESRP1 might be better prognosis markers and therapeutic targets for breast cancer metastasis.
Project description:Accumulating evidence has demonstrated that breast cancers are initiated and develop from a small population of stem-like cells termed cancer stem cells (CSCs). These cells are hypothesized to mediate tumor metastasis and contribute to therapeutic resistance. However, the molecular regulatory networks responsible for maintaining CSCs in an undifferentiated state have yet to be elucidated. In this study, we used CSC markers to isolate pure breast CSCs fractions (ALDH+ and CD44+CD24- cell populations) and the mature luminal cells (CD49f-EpCAM+) from the MCF7 cell line. Proteomic analysis was performed on these samples and a total of 3304 proteins were identified. A label-free quantitative method was applied to analyze differentially expressed proteins. Using the criteria of greater than twofold changes and p value <0.05, 305, 322 and 98 proteins were identified as significantly different in three pairwise comparisons of ALDH+ versus CD44+CD24-, ALDH+ versus CD49f-EpCAM+ and CD44+CD24- versus CD49f-EpCAM+, respectively. Pathway analysis of differentially expressed proteins by Ingenuity Pathway Analysis (IPA) revealed potential molecular regulatory networks that may regulate CSCs. Selected differential proteins were validated by Western blot assay and immunohistochemical staining. The use of proteomics analysis may increase our understanding of the underlying molecular mechanisms of breast CSCs. This may be of importance in the future development of anti-CSC therapeutics.
Project description:Mechanisms for breast cancer metastasis remain unclear. Whether truncated glioma-associated oncogene homolog 1 (TGLI1), a transcription factor known to promote angiogenesis, migration and invasion, plays any role in metastasis of any tumor type has never been investigated. In this study, results of two mouse models of breast cancer metastasis showed that ectopic expression of TGLI1, but not GLI1, promoted preferential metastasis to the brain. Conversely, selective TGLI1 knockdown using antisense oligonucleotides led to decreased breast cancer brain metastasis (BCBM) in vivo. Immunohistochemical staining showed that TGLI1, but not GLI1, was increased in lymph node metastases compared to matched primary tumors, and that TGLI1 was expressed at higher levels in BCBM specimens compared to primary tumors. TGLI1 activation is associated with a shortened time to develop BCBM and enriched in HER2-enriched and triple-negative breast cancers. Radioresistant BCBM cell lines and specimens expressed higher levels of TGLI1, but not GLI1, than radiosensitive counterparts. Since cancer stem cells (CSCs) are radioresistant and metastasis-initiating cells, we examined TGLI1 for its involvement in breast CSCs and found TGLI1 to transcriptionally activate stemness genes CD44, Nanog, Sox2, and OCT4 leading to CSC renewal, and TGLI1 outcompetes with GLI1 for binding to target promoters. We next examined whether astrocyte-priming underlies TGLI1-mediated brain tropism and found that TGLI1-positive CSCs strongly activated and interacted with astrocytes in vitro and in vivo. These findings demonstrate, for the first time, that TGLI1 mediates breast cancer metastasis to the brain, in part, through promoting metastasis-initiating CSCs and activating astrocytes in BCBM microenvironment.
Project description:Triple negative breast cancer (TNBC) is known to contain a high percentage of CD44(+) /CD24(-/low) cancer stem cells (CSCs), corresponding with a poor prognosis despite systemic chemotherapy. Chloroquine (CQ), an antimalarial drug, is a lysotropic reagent which inhibits autophagy. CQ was identified as a potential CSC inhibitor through in silico gene expression signature analysis of the CD44(+) /CD24(-/low) CSC population. Autophagy plays a critical role in adaptation to stress conditions in cancer cells, and is related with drug resistance and CSC maintenance. Thus, the objectives of this study were to examine the potential enhanced efficacy arising from addition of CQ to standard chemotherapy (paclitaxel) in TNBC and to identify the mechanism by which CQ eliminates CSCs in TNBCs. Herein, we report that CQ sensitizes TNBC cells to paclitaxel through inhibition of autophagy and reduces the CD44(+) /CD24(-/low) CSC population in both preclinical and clinical settings. Also, we are the first to report a mechanism by which CQ regulates the CSCs in TNBC through inhibition of the Janus-activated kinase 2 (Jak2)-signal transducer and activator of transcription 3 signaling pathway by reducing the expression of Jak2 and DNA methyltransferase 1.
Project description:Despite significant improvement in survival rates of patients with breast cancer, prognosis of metastatic disease is still dismal. Cancer stem-like cells (CSC) are considered to play a role in metastatic progression of breast cancer; however, the exact pathologic role of CSCs is yet to be elucidated. In this report, we found that CSCs (CD24(-)/CD44(+)/ESA(+)) isolated from metastatic breast cell lines are significantly more metastatic than non-CSC populations in an organ-specific manner. The results of our microRNA (miRNA) profile analysis for these cells revealed that CSCs that are highly metastatic to bone and brain expressed significantly lower level of miR-7 and that this miRNA was capable of modulating one of the essential genes for induced pluripotent stem cell, KLF4. Interestingly, high expression of KLF4 was significantly and inversely correlated to brain but not bone metastasis-free survival of patients with breast cancer, and we indeed found that the expression of miR-7 significantly suppressed the ability of CSCs to metastasize to brain but not to bone in our animal model. We also examined the expression of miR-7 and KLF4 in brain-metastatic lesions and found that these genes were significantly down- or upregulated, respectively, in the tumor cells in brain. Furthermore, the results of our in vitro experiments indicate that miR-7 attenuates the abilities of invasion and self-renewal of CSCs by modulating KLF4 expression. These results suggest that miR-7 and KLF4 may serve as biomarkers or therapeutic targets for brain metastasis of breast cancer.