Gene expression analysis reveals high pluripotent status and metastatic ability of CD133 positive cells in primary papillary thyroid cancer

Objectives Stemness cells which escape from radiation ablation, might contribute to recurrence and metastasis. CD133 is recently proposed as a marker of cancer stem cell. This study aimed to evaluate pluripotent status and metastatic potency of CD133^pos and CD133^neg cells derived from resected primary Papillary thyroid cancer (PTC).

Methods PTC resected from patients were cultured in F12K containing 10% FBS and supplemented with hydrocortisone, TSH, Insulin and Glycyl-L-histidyl-L- Lysine acetate. Cells expressing CD133 were isolated with magnetic microbeads and total RNA were isolated and reverse transcribed for subsequent real-time quantitative PCR using the TagMan Probe system. CD133^pos and CD133^neg cell proliferation was measured by MTS assay. Invasion/migration experiment was performed using a dual chamber system. Cells were irradiated with γ-ray then CD133 population was measured to evaluate radioresistance.

Results Selected gene expression including regulators of ES cell self-renewal and pluripotency (Oct4, Sox2, nanog, Klf4, Lin28 and c-Myc), thyroid specific transcription factors (TTF-1 and Pax8) and thyroid specific genes (NIS, TPO, Tg, TSHR and Pendrin) were analyzed. CD133^pos cells represent ~5% of the whole population and are enriched to >70% as analyzed by flow cytometry. ES cell regulators are expressed significantly higher in CD133^pos cells than in CD133^neg cells including Oct4, nanog, Lin28 and Sox2. Thyroid specific gene expression was significantly higher in CD133^neg than in CD133^pos cells, including NIS, Tg, TPO and TSHR. CD133^pos cells showed more radioresistant, more proliferative and also more invasive than CD133^neg cells.

Conclusions CD133^pos cells within PTC have a great potential of contributing to the recurrence or distant metastasis of PTC