In the last years, a growing body of evidence supports the notion that tumors are organized in a hierarchy of heterogeneous cell populations with different biologic properties and that the capability to sustain tumor formation and growth exclusively resides in a small proportion of tumor cells, termed cancer stem cells (CSC). The existence of CSC was first proven in the context of acute myelogenous leukaemia, and subsequently verified in brain, breast, colon and prostate cancers. These studies have shown that CSC are responsible for tumor formation and progression and share with stem cells the key feature of self-renewal. Our aim was to identify and characterize CSC in different anaplastic thyroid cancer cell lines. For this purpose, we analysed the expression of stem cell markers, such as CD133, OCT4, c-KIT, THY-1, NANOG and GATA-4, in cultured ARO, KAT-4, KAT-18 and FRO cell lines, simultaneously with specific thyrocyte markers (TPO, thyroglobulin and CK-19), by flow cytometry and real time PCR. Only two cell lines, ARO and KAT-4, showed CSC positive for CD133 (44±12%) and OCT4 (30±15%) while the other CSC markers were absent in all the examined cell lines. Furthermore, CD133+ stem like cells sorted by specific magnetic beads (Miltenyi Biotec) (>90%), were analysed for their growing capabilities in basal conditions and without fetal bovine serum in the presence of specific stem cell growth factors (bFGF and EGF). Our data showed that CD133+ stem like cells were characterized by elevated proliferation, self-renewal features and by expression of stemness genes when compared with the CD133− cells. In conclusion, we report the identification of CSC population in ARO and KAT-4 anaplastic cell lines characterized by their CD133+/OCT4+ phenotype. The identification of tumorigenic thyroid CSC could provide new insights into the anaplastic thyroid tumorigenic process and possibly bear great therapeutic implications.
03 - 07 May 2008
European Society of Endocrinology