CCDC6 and thyroid gland papillary carcinoma: To further understand the role of CCDC6 in PP4c activity modulation we utilized a human CCDC6-null cell line, the thyroid papillary carcinoma TPC-1 cell line, that carries the RET/PTC1 oncogene and has lost by deletion the normal unrearranged CCDC6 allele [39].