Genomic profiling of tumor initiating prostatospheres

Abstract

BackgroundThe cancer stem cell (CSC) hypothesis proposes that a population of tumor cells bearing stem cell properties is responsible for the origin and maintenance of tumors. Normal and cancer stem cells possess the ability to grow in vitro as self-renewing spheres, but the molecular basis of this phenotype remains largely unknown. We intended to establish a comprehensive culture system to grow prostatospheres (PSs) from both cancer cell lines and patient tumors. We then used gene expression microarrays to gain insight on the molecular pathways that sustain the PS tumor initiating cell (TIC) phenotype.ResultsTraditional stem cell medium (SCM) supplemented with Knockout™SR (KO) allows the propagation of monoclonal PSs from cell lines and primary cells. PSs display gene expression and tumorigenicity hallmarks of TICs. Gene expression analysis defined a gene signature composed of 66 genes that characterize LNCaP and patient PSs. This set includes novel prostate TIC growth factors (NRP1, GDF1, JAG1), proteins implicated in cell adhesion and cytoskeletal maintenance, transcriptional regulators (MYCBP, MYBL1, ID1, ID3, FOS, ELF3, ELF4, KLF2, KLF5) and factors involved in protein biosynthesis and metabolism. Meta-analysis in Oncomine reveals that some of these genes correlate with prostate cancer status and/or progression. Reporter genes and inhibitors indicate that the Notch pathway contributes to prostatosphere growth.ConclusionsWe have developed a model for the culture of PSs, and provide a genomic profile that support CSCs identity. This signature identifies novel markers and pathways that are predicted to correlate with prostate cancer evolution.

Radioresistance and Cancer Stem Cells: Survival of the Fittest

“…The data derived from the Oncomine database suggest that this speculation is credible as the samples derived from prostate metastatic populations in a bulk tumor have an increase in these genes. Hence, this combined with previous data further supports that CSCs are more radioresistant than their nonmetastatic counterparts [10]. Additionally, CSCs with radioresistance properties are speculated to be responsible for the repopulation of cancer cells after radiotherapy, during which radioresistance genes play a central role, thus, contributing to patient relapse.…”

“…Previous studies in our laboratory show that prostatospheres derived from the immortalized LNCaP cell line and primary patient cell lines PCSC1, PCSC2, PCSC3 are representative of the CSC population and display the capacity to initiate tumors in vivo [10]. Using Ingenuity Pathway Analysis (IPA) software, we analyzed the genes significantly upregulated in prostatospheres to the total adherent cell population.…”

“…There are several methods used to enrich for the CSC population in total cancer cells, including flow cytometry based on cell surface marker gene expression of CD44, CD24, CD133, and α2β1 [8,9]. In addition, CSCs can be enriched for in cultures of serum free stem cell media in attachment independent systems, resulting in the development of 'spheres' [10][11][12][13].…”

Why are epididymal tumours so rare?

“…However, the formation in human epididymal cell culture of epithelial spheres, 8 a characteristic of 'cancer stem cells' or 'tumour initiating cells', 14 suggests that these cells do exist.…”

Inverse association of p16INK4a and p14ARF methylation of the CDKN2a locus in different Gleason scores of prostate cancer

“…Gleason score 7 tumours are heterogeneous with a more aggressive behaviour in carcinomas that are Gleason 7b ¼ 4 þ 3 compared with Gleason 7a ¼ 3 þ 4. 3,4 Although recent advances in the study of proteomics and highthroughput techniques have discovered many potential biomarkers for PCa, [5][6][7] there still remains a need for biomarkers to predict the outcomes of the tumour. [8][9][10] Therefore, we focused on epigenetic events such as aberrant promoter methylation to identify new markers predicting PCa aggressiveness.…”