Effect of sunitinib on the proliferation and survival of FRTL-5 cells / 대한내과학회지

ABSTRACT

BACKGROUND/AIMS: Hypothyroidism has been reported in 36~85% of patients treated with sunitinib for renal cell carcinoma or gastrointestinal stromal tumor. However, the mechanism behind this hypothyroidism is unclear. This study evaluated the effects of sunitinib, a multi-target tyrosine kinase inhibitor, on the survival and proliferation of thyrocytes using FRTL-5 rat thyroid cells. METHODS: We examined the effect of sunitinib on cell proliferation in the presence and absence of thyroid stimulating hormone (TSH) in a colorimetric assay. Effects on the cell cycle were evaluated by flow cytometry, and on apoptosis using an annexin V apoptosis assay kit and by immunoblotting for caspase-3. Immunoblotting was also used to evaluate changes in the levels of intracellular proteins associated with the G1-S phase of the cell cycle. RESULTS: Sunitinib suppressed the proliferation of FRTL-5 cells in a dose- and time-dependent manner. This suppressive effect was enhanced by the presence of TSH (1 mU/mL). Sunitinib was subsequently shown, in flow cytometric analyses, to arrest the cell cycle at the G1-S phase. Furthermore, it induced apoptosis at a high concentration (15 micrometer) by activating caspase-3. G1-S phase arrest was associated with the induction of p27(kip1) and p21(cip1), whose expression is suppressed by TSH under control conditions. Sunitinib also decreased intracellular levels of cyclin D1 and cyclin-dependent kinase 2 in FRTL-5 cells. CONCLUSIONS: Sunitinib induced apoptosis in and suppressed the proliferation of FRTL-5 cells. Its suppression of proliferation was further enhanced by the presence of TSH. Sunitinib arrested the cell cycle in the G1-S phase by inducing the expression of p27(kip1)/p21(cip1), which are suppressed by TSH under normal conditions. Collectively, these findings suggest that sunitinib may interfere with TSH signaling pathways in normal thyrocytes.