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Side Population Analysis in Clear Cell Renal Cell Carcinoma

ABSTRACT: Cancer stem cells have an important role in tumour biology. While their identity in haematological malignancies is clearly defined, stem cell identity remains elusive in some solid tumours. Clear cell renal cell carcinoma (ccRCC) represents the most common form of kidney cancer, but the identity or existence of ccRCC stem cells remains unknown. We aimed to discern their existence using the widely utilised side population approach in ccRCC cell lines. In all cells tested, a well-defined side population was identified, and cell-based assays suggested stem-like properties. However, limiting dilution assays revealed comparable tumour initiating abilities and tumour histology of side and non-side populations, and single cell RNA-sequencing revealed minimal differences between these populations. The results indicate that the side population approach is not sufficient for cancer stem cell discovery in ccRCC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE188635 | GEO | 2021/11/22

REPOSITORIES: GEO

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Project description:The recent identification of cancer stem cells (CSCs) in multiple human cancers provides a new inroad to understanding tumorigenesis at the cellular level. CSCs are defined by their characteristics of self-renewal, multipotentiality, and tumor initiation upon transplantation. By testing for these defining characteristics, we provide evidence for the existence of CSCs in a transgenic mouse model of glioma, S100Ã-verbB;Trp53. In this glioma model, CSCs are enriched in the side-population (SP) cells. These SP cells have enhanced tumor-initiating capacity, self-renewal, and multipotentiality compared to non-SP cells from the same tumors. Furthermore, gene expression analysis comparing FACS-sorted cancer SP cells to non-SP cancer cells and normal neural SP cells identified 45 candidate genes that are differentially expressed in glioma stem cells. We validated the expression of two genes from this list (S100a4 and S100a6) in primary mouse gliomas and human glioma samples. Analyses of xenografted human GBM (glioblatoma multiforme) cell lines and primary human glioma tissues show that S100A4 and S100A6 are expressed in a small subset of cancer cells and that their abundance is positively correlated to tumor grade. In conclusion, this study shows that CSCs exist in a mouse glioma model, suggesting that this model can be used to study the molecular and cellular characteristics of CSCs in vivo and to further test the cancer stem cell hypothesis. Experiment Overall Design: This study features two factors, injected cell origin (either tumorsphere or neurosphere) and FACS cell population (either side population or non-side population cells). There were two different tumorspheres, labeled 3447 and 4346 that were isolated from brain tumors in S100beta-verbB;p53-/- or S100beta-verbB;p53+/- mice. The tumorspheres were injected separately into the brains of NOD.Cg-Prkdc<scid>Il2rg<tm1Wjl>/SzJ mice to generate biological triplicates of each primary tumor. Tumorspheres were isolated and cultured before FACS sorting to obtain side population and non-side population cells. As a control, untransformed neurospheres from three independent S100beta-verbB;p53-/- or S100beta-verbB;p53+/- mice were isolated, cultured, and FACS sorted to obtain side population and non-side population cells. Side population and non-side population cells cultured from three mice injected with the 3447 cultured tumorspheres were assayed for gene expression (six samples). Side-population stem cells cultured from three mice injected with the 4346 cultured tumorspheres were assayed for gene expression (three samples). Side-population and non-side population cells cultured from three mice injected with the neurospheres were assayed for gene expression (six samples).

Project description:Tumours contain heterogeneous cell populations. A population enriched in tumour-initiating potential has been identified in soft-tissue sarcoma (STS) by the isolation of side population (SP) cells. In this study, we compared the gene expression profiles of SP and non-SP cells in STS and identified Hedgehog (Hh) and Notch pathways as potential candidates for the targeting of SP cells. Upon verification of the activation of these pathways in SP cells, using primary tumor xenografts in NOD-SCID mice as our experimental model, we used the Hh blocker Triparanol and the Notch blocker DAPT to demonstrate that the suppression of these pathways effectively depleted the abundance of SP cells, reduced tumour growth, and inhibited the tumour-initiating potential of the treated sarcoma cells upon secondary transplantation. The data provide additional evidence that SP cells act as tumour initiating cells and points to Hh and Notch pathways as enticing targets for developing potential cancer therapies. We used microarrays to detail the difference in gene expressions between the side population cells in soft-tissue sarcoma in comparison to the bulk non-side-population cells. To examine whether certain pathways may be differentially regulated in SP cells versus non-SP cells, which represent the bulk of tumour cells, we compared the gene expression profiles of SP and non-SP cells in four primary STS tumours each from different patient. Upon surgical excision, these tumours were dissociated mechanically and enzymatically into individual cells. Via Hoechst dye staining and flow-cytometry, these primary tumour cells were sorted into distinct side population and non-side population fractions. Total RNA is extracted from an equal number of SP and NSP cell from each primary tumour. cDNA from each sample was generated from the isolated total RNA and hybridized onto Affymetrix Human Genome EukGE-WS2v4 gene chips against the same reference cDNA library. After initial processing of the raw data, using the Genespring® GX software, the expression of SP cells from each tumour was normalized against the expression of the corresponding non-SP cells. A gene list was constructed by selecting genes that were regulated in the same direction (SP vs. NSP) in all sample pairs with a fold change greater than 1.25. This list was examined using Genespring® GX significant pathway function to identify differentially regulated pathways.

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Side Population Analysis in Clear Cell Renal Cell Carcinoma

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