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The TLR2 pathway is required for self-renewal of mammary cancer initiating cells

ABSTRACT: In the past few years, mammary cancer initiating cells (CICs) have been identified in mouse and human as a subpopulation of tumor cells that selectively posses tumor initiation and self-renewal capacity and the ability to give rise to bulk populations of non-tumorigenic cancer cells progeny through differentiation. They could also be responsible for tumor progression, metastasis, resistance to therapy and recurrence. Thus, the understanding of the pathways regulating CIC self-renewal, differentiation and tumorigenicity represents an important task in the development of effective anticancer therapies. To detect the set of genes associated to CIC in our mouse breast cancer model we analysed three prototypic situations: TUBO cells grown in DMEM under adherent conditions (called TDA in GSE26517 and epithelial bulk in GSE21451), TUBO cells grown in mammosphere medium under adherent conditions (called TMA in GSE26517), TUBO cells grown in mammosphere medium under low-attachment conditions (called mammospheres p1 in GSE21451), i.e. the conditions used to support the formation of mammospheres. This analysis led to the identification of growth factors and immune system-related genes, including toll-like receptor 2 (TLR2). The inhibition of TLR2 signaling pathway strongly impaired mammosphere generation, demonstrating the involvement of TLR2 in CSC self-renewal.

ORGANISM(S): Mus musculus

PROVIDER: GSE26527 | GEO | 2013/11/30

SECONDARY ACCESSION(S): PRJNA136643

REPOSITORIES: GEO

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Project description:In the past few years, mammary cancer initiating cells (CICs) have been identified in mouse and human as a subpopulation of tumor cells that selectively posses tumor initiation and self-renewal capacity and the ability to give rise to bulk populations of non-tumorigenic cancer cells progeny through differentiation. They could also be responsible for tumor progression, metastasis, resistance to therapy and recurrence. Thus, the understanding of the pathways regulating CIC self-renewal, differentiation and tumorigenicity represents an important task in the development of effective anticancer therapies. To detect the set of genes associated to CIC in our mouse breast cancer model we analysed three prototypic situations: TUBO cells grown in DMEM under adherent conditions (called TDA in GSE26517 and epithelial bulk in GSE21451), TUBO cells grown in mammosphere medium under adherent conditions (called TMA in GSE26517), TUBO cells grown in mammosphere medium under low-attachment conditions (called mammospheres p1 in GSE21451), i.e. the conditions used to support the formation of mammospheres. This analysis led to the identification of growth factors and immune system-related genes, including toll-like receptor 2 (TLR2). The inhibition of TLR2 signaling pathway strongly impaired mammosphere generation, demonstrating the involvement of TLR2 in CSC self-renewal. We profiled on MouseWG?6 v2.0 Illumina beadchips two independent experiments: ADHERENT (GSE26517) made by the comparison between TDA and TMA and SOSPENSION (part of GSE21451) made by the comparison between epithelial bulk and mammospheres p1. Mammosphere medium contains epidermal growth factor (EGF), insulin and basic fibroblast growth factor (bFGF) that may influence transcript expression in a way not necessarily related to the assembly of mammospheres. Therefore, following normalization and removal of those transcripts not expressed and not changing, we used the Integrative Correlation coefficient (IC, Parmigiani et al. Clin Cancer Res 2004, 10:2922–2927) as filter to remove genes only associate to growth factors present in the mammosphere medium under adherent growth conditions, i.e IC > 0.1. Differential gene expression was then assessed by regularized t?test (Smyth GK. Stat Appl Genet Mol Biol 2004, 3:Article3) comparing mammospheres p1 with respect to epithelial bulk, using an uncorrected p-value ? 0.05, together with an absolute log2 fold change threshold ?1.

Project description:The efficacy of cancer treatments have improved constantly in the last decade. However, therapeutic resistance and the lack of curative treatments in metastatic disease, raises the question if conventional anticancer therapies target the right cells. Indeed, these treatments might miss cancer stem cells (CSCs), which might also represent a more chemoresistant and radioresistant subpopulation within cancer. In this view using vaccines in tertiary prevention of cancer, i.e. residual disease treatment, might be particularly effective if vaccine-elicited immune response is directed against CSC oncoantigens (OAs) M-bM-^@M-^T proteins required for the neoplastic process M-bM-^@M-^T the chance that the tumour will evade the vaccine should be reduced. An important task to devise effective CSC preventive vaccines is therefore the identification of CSC OAs. In this experiment we used a cell line (TuBo) derived by the mouse breast cancer model BALB-neuT and its CSC subpupolation, enriched by mean of mammosphere formation. Integrating data derived by gene and exon-level transcription profiling of the above experiments with public available normal and tumor datasets we identified two new breast cancer CSC OAs: TMPRSS4 and xCT. Both genes are linked to invasion, migration and metastasis. Furthermore, we observed that alternative splicing events discriminating TuBo cells, grown in adherent medium, with respect of TuBo mammospheres, produced growing in no-adherent medium, are very limited. We detect only one clear splcing event characterizing the beta-isoform of Rabgap1l gene. This SuperSeries is composed of the SubSeries listed below. The adherent TuBo epithelial cells were generated from a mammary carcinoma arising in a BALB/c mouse female transgenic for the activated rat ErbB2 oncogene (BALB-neuT) and were cultured in DMEM supplemented with 20% FCS. Single TuBo cells were plated in ultra low attachment flasks in serum-free DMEM-F12 medium supplemented with bFGF, EGF and insulin. Nonadherent spherical clusters of cells, named mammospheres, were collected by gentle centrifugation after 7 days and dissociated enzymatically and mechanically, using trypsin and pipetting, respectively.

Project description:The efficacy of cancer treatments have improved constantly in the last decade. However, therapeutic resistance and the lack of curative treatments in metastatic disease, raises the question if conventional anticancer therapies target the right cells. Indeed, these treatments might miss cancer stem cells (CSCs), which might also represent a more chemoresistant and radioresistant subpopulation within cancer. In this view using vaccines in tertiary prevention of cancer, i.e. residual disease treatment, might be particularly effective if vaccine-elicited immune response is directed against CSC oncoantigens (OAs) — proteins required for the neoplastic process — the chance that the tumour will evade the vaccine should be reduced. An important task to devise effective CSC preventive vaccines is therefore the identification of CSC OAs. We used gene-level transcription profiling of TuBo epithelial cell and three mammosphere passages (P1, P2 and P3). This analysis allowed the identification of two new breast cancer CSC OAs: TMPRSS4 and xCT. Both genes are linked to invasion, migration and metastasis. These results were achieved integrating data derived by the analysis of transcription profile of CSCs derived by BALB-neuT mouse breast cancer model with meta-analyses of seven large independent breast tumour data sets. TuBo cell line (E) was compared to passage 1 (P1), 2 (P2) and 3 (P3) mammospheres (three independent experiments for each experimental condition). Transcription profiling was done using MouseWG-6 v2.0 Illumina beadchips. After normalization and removal of non significant probes (i.e. those not expressed and those not changing) differential expression between epithelial and mammospheres, was assessed using regularized t-test comparing each mammosphere passage with respect to TuBo cells using a FDR ≤ 0.05 together with an |log2(fold-change)|≥1. The union of the three sets of differentially expressed transcripts produced a total of 495 transcripts.

Project description:Tumorigenic breast cancer cells characterized by CD44 expression and low or undetectable CD24 levels (CD44+/CD24-/low) may be resistant to chemotherapy and therefore responsible for cancer relapse. Paired breast cancer core biopsies before and after neoadjuvant chemotherapy or lapatinib were obtained and as single cell suspensions stained using antibodies against CD24, CD44, and lineage markers, and then analyzed by flow cytometry. Mammosphere (MS) formation in culture was compared before and after treatment. Global gene expression differences between cancer cells bearing CD44+/CD24-/low cells and all other sorted cells, and between cancer MS and the primary bulk invasive cancers were analyzed. We report that CD44+/CD24-/low tumorigenic breast cancer cells were intrinsically chemoresistant - chemotherapy led to increased CD44+/CD24-/low cells, increased self-renewal capacity on MS assays, and enhanced tumorigeneicity in immunocompromised SCID/Beige mice. Conversely, in patients with HER2 overexpressing tumors, the EGFR/HER2 tyrosine kinase inhibitor, lapatinib decreased CD44+/CD24-/low cells, with the majority of these patients after conventional therapy achieving pathologic complete response, a validated surrogate marker for long-term survival. Gene transcription pathways that underlie chemoresistant, MS-forming CD44+/CD24-/low cells involve genes belonging to stem cell self-renewal, Wnt signaling, and early development pathways. Experiment Overall Design: Cells from human breast tumors were grown as mammospheres (MS). Experiment Overall Design: Isolated single cell suspensions from primary breast cancers were plated onto non-adherent (polyhema-coated) plastic, counted with a hematocytometer, and 20,000 cells were then seeded into a 6-well ultra-low attachment plate supplemented with 2mL MEGM, with the addition of 2 mL of freshly unfrozen MEGM every 3-4 days. Gene expression profiles were taken of both MS and primary bulk tumors and compared with each other.

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The TLR2 pathway is required for self-renewal of mammary cancer initiating cells

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