In contrast, in thyroid cancer cell lines originating from papillary thyroid carcinoma (BcPAP and TPC1), only low levels of Prox1 mRNA were detectable while the corresponding protein was detected both by Western blot and immunofluorescent staining, even though at lower level than in the two FTC-derived cell lines. This evidence concerns the gene PROX1 and differentiated thyroid carcinoma.