Identification and Characterization of Tumour Initiating Cells From Gynaecological Malignancies

Bortolomai, Ileana (2011). Identification and Characterization of Tumour Initiating Cells From Gynaecological Malignancies. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f159

Abstract

In the first part of the study, I developed a model to study the CSC/TIC population of the A431 cell line based on the capability of these cells to form spheres in suspension.

Putative A431 CSC/TIC were characterized for ‘stemness’ properties such as self-renewal and clone forming capability, presence of a SP and ALDH enzymatic activity, putative stem cell marker expression and in vivo tumorigenicity. The results indicate that the growth of A431 cells, as spheres, was not sufficient by itself to define a stem like population, but it was essential for the emergence of a small population of tumour cells with CSC properties. Then, I investigated CSC/TIC in Epithelial Ovarian Cancer (EOC), with a focus on CD133 and CXCR4 molecules. In a wide range of primary EOC and ascites the expression of CD133 and CXCR4 was found restricted within two separate subpopulations of tumour cells.

Enrichment in mRNA levels of OCT4, NANOG and NESTIN was observed with good reproducibility in CXCR4 positive cells, whereas it was more variable in CD133 positive cells. Real Time analyses of ABC transporter expression showed there was a slight increase in CXCR4 positive cells while in CD133 positive cells this increase was much more evident, revealing a clear difference between CXCR4 and CD133 subpopulations in term of chemoresistance potential. Furthermore positive cells isolated from xenograft-derived ascites and sorted for CXCR4 and CD133 were not characterized by higher tumorigenic capacity.

In summary, no correlation between CD133 positivity and the ovarian cancer sternness phenotype was found. However detection of CD133 positive cells may be useful to predict the efficacy of specific cytotoxic therapy.

On the contrary, CXCR4 positive cells may identify those tumour cells which maintain a partially un-differentiated state (high levels of stem cell marker expression) and possibly responsible for tumour invasion and metastasis.