Enrichment and Characterization of the Cancer Stem Cell (CSC) Fraction From PC3 Prostate Cancer Cell Line Cultures

Enrichment and characterization of the Cancer Stem Cell (CSC) fraction from PC3 prostate cancer cell line cultures

Roberto Portillo Lara¹ and Mario Moises Alvarez^1,2

(1) Centro de Biotecnologia-FEMSA at Tecnologico de Monterrey

Av. Eugenio Garza Sada 2501 sur. Monterrey, NL. Mexico

(2) Escuela de Biotecnologia y Salud at Tecnologico de Monterrey

Av. Morones Prieto 3000 pte. Monterrey, NL. Mexico

The main goal of my work is the characterization of cancer stem cells (CSCs) induced and isolated from the PC3 prostate cancer cell line.

The Cancer Stem Cell hypothesis postulates that the small fraction of cancerous stem –like cells (CSCs) present in solid tumors are responsible for the origin and propagation of the disease. A vast amount of experimental evidence supports this argument. In recent years several groups worldwide have achieved the isolation of CSCs from different types of solid cancers and leukemias. However the percentage in which these cells are present within tumorous tissue is extremely low. Moreover, the difficulty of purifying a single cell type from a tissue biopsy has led to the search for reliable models that allow the expansion and study of these particular cells. One of these approaches is the use of established cell lines. The identification of a subpopulation of cells, within a given cell line, expressing a phenotype similar to the one observed in CSCs isolated from patients samples has already been demonstrated previously. However the purification yields are extremely low and the establishment of a definitive cell culture protocol is still work in progress.

The isolation of cells expressing the CD44⁺/α2β1^hi/CD133⁺ phenotype (which corresponds to the one observed in CSCs obtained from biopsies) from a PC3 cell line cultured under standard conditions, yields a percentage of 0.1 positive events when analyzed via flow cytometry (this is consistent with the information available in the literature). With the implementation of a simple protocol, not previously reported, it is possible to increase this percentage up to 5 percent. In addition to this, we have conducted a protocol of gene expression profiling of PC3 cells cultured with the standard and the novel protocol through distinct points in time and at the end point of culture. This characterization was carried out using the nCounter NanoString system. This technology allows us to assess the levels of expression of a curated panel of 250 genes simultaneously. This type of characterization presents us with a rich panorama of the transcriptional level in these CSCs both at the end point of the experiment and through the process of induction. This information could provide a better understanding of the mechanisms of cell development that are key in CSC's propagation as well as point us to the identification of novel, highly specific therapeutic targets.