Serum samples and cell culture

The serum samples of PTC patients with ¹³¹I-avid and non-¹³¹I-avid lung metastases were collected from September 2010 to July 2014 at our department. The inclusion/exclusion criteria and the method to process the samples have been described before [17]. Total RNA from serum sample was extracted and purified using the miRNeasy Mini Kit (Qiagen, Valencia, CA) according to the manufacturer’s instructions. The study was approved by the Institutional Ethics Review Board of our hospital and informed consent was obtained from each patient.

Human PTC cell line CGTH-W3 (Institute of Biochemistry and Cell Biology, SIBS, CAS, Shanghai, China) and anaplastic thyroid carcinoma (ATC) cell line 8505C (Institute of Biochemistry and Cell Biology, SIBS, CAS, Shanghai, China) were cultured in RPMI-1640 (Gibco, Cat. # 11875–093) supplemented with 10 % fetal bovine serum (Gibco, Cat. # 16000–044). HEK 293 T (Institute of Biochemistry and Cell Biology, SIBS, CAS, Shanghai, China) was maintained in Deulbecco’s Modified Eagle medium (Gibco, Cat. # 10565–018) supplemented with 10 % fetal bovine serum (Gibco, Cat. # 16000–044). All the cells were incubated at 37 °C in a humidified chamber supplemented with 5 % CO₂. U0126 and SB203580 were obtained from Selleck Chemicals (Houston, TX, Cat. # S1102 and S1076). All-trans retinoic acid (RA) was obtained from Sigma-Aldrich (Cat. # R2625).