Investigating the theragnostic potential of 131I-caerin peptide in thyroid cancer.

OBJECTIVE: Caerin is a new peptide with tumour toxicity and its uptake by tumour cells is independent of the sodium iodide symporter (NIS). Thyroid cancer is the most common cancers of endocrine malignancy. Radioiodine (131I)-refractory thyroid cancer is the most lethal subtype of the thyroid cancers and remains a clinical challenge. In the current study, we investigated the 131I radiolabeling efficiency of Caerin and the effects of Caerin, 131I-Caerin and free 131I on differentiated and undifferentiated human thyroid cancer cell lines (B-CPAP and CAL-62) in vitro. MATERIALS AND METHODS: Cell Counting Kit-8 was used to assess the cytotoxic effect of Caerin, 131I-Caerin and free 131I on B-CPAP and CAL-62 cells. Laser scanning confocal microscope was exploited to evaluate the uptake and internalization of Caerin by thyroid cancer cells. The Chloramine-T method was used to label the peptide with 131I. And the stability and water partition coefficient (Log P) of 131I-Caerin were studied. RESULTS: Our results demonstrated that Caerin and 131I-Caerin could be accumulated by B-CPAP and CAL-62 cells, resulting in killing of the thyroid cancer cells in vitro. The efficacy of 131I-Caerin is much higher than 131I, especially to undifferentiated CAL-62 cells. The results prove the feasibility of radioiodination of the 131I-Caerin via the Chloramine-T method. Moreover, the result indicate the hydrophobic 131I-Caerin was stable in 72 hours. CONCLUSION: Iodine-131-Caerin can inhibit the cell viability of thyroid cancer and hold certain promise as a theragnostic tool for human thyroid cancers.