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

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.

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.

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.

Iodine-131-Caerin can inhibit the cell viability of thyroid cancer and hold certain promise as a theragnostic tool for human thyroid cancers.