PDLIM5 identified by label-free quantitative proteomics as a potential novel biomarker of papillary thyroid carcinoma

In order to better understand the mechanisms underlying the development of papillary thyroid carcinoma (PTC), and to identify new potential biomarkers, high-resolution label-free mass spectrometry was performed on PTC tissues and adjacent normal thyroid tissues from six patients. In this process, 2788 proteins were identified, out of which 49 proteins presented significant differences between PTC tissues and adjacent normal thyroid tissues. Gene ontology revealed that the majority of these proteins are involved in the catalytic activity and binding. We selected three proteins with differential expressions: PDZ and LIM domain 5 (PDLIM5), PDLIM1 and ALDH1A1; Protein expressions were further verified by RT-PCR and western blot. Among these, expression of PDLIM5 and PDLIM1 was up-regulated, while that of ALDH1A1 was down-regulated in PTC tissues. Next, we confirmed their expression through quantitative dot blot (QDB) technique. We found that knockdown of PDLIM5 expression in the B-CPAP cell line could inhibit the migration, invasion and proliferation of PTC cells. In addition, PDLIM5 knockdown reduced Ras and Phospho-ERK1/2 expression. Thus, we suggested that PDLIM5 promotes PTC via activation of the Ras-ERK pathway. Our research provides new molecular insight into the function of PDLIM5, which may assist in studying the mechanism of PTC. In addition, PDLIM5 could be further explored as a potential candidate for PTC treatment.