PC PTC1 and PC E1A clones are PC Cl3 derivatives that were transformed with PTC1 and E1A oncogenes [23]. PTC1 is a papillary thyroid cancer- (PTC-) associated oncogene derived from a genomic rearrangement of the RET oncogene with the CDC61/H4 gene [24]. Here, RET is linked to thyroid gland papillary carcinoma.