Zinc finger protein 703 (ZNF703), a member of the NET family of transcription factors, has recently emerged as an important player in the development of several types of cancers, though its role in papillary thyroid cancer (PTC) has not been characterized. We investigated the expression of ZNF703, its association with the most common genetic mutation in PTC, BRAF V600E, and its potential use as a therapeutic target. Real-time PCR, immunohistochemical staining, and western blot analysis of ZNF703 expression were performed for 36 cases of PTC and corresponding normal thyroid tissues. ZNF703 mRNA and protein expression was found to be significantly higher in PTC compared to normal thyroid tissues (P < 0.05). Furthermore, expression was associated with the tumor size, lymph node metastasis, and advanced disease stage. Immunohistochemical results showed that there was no correlation between ZNF703 protein levels and BRAF V600E mutation. The human PTC cell line K1, which has a BRAF V600E mutation, was selected for further investigation. Using small interfering RNA (siRNA), ZNF703 was shown to contribute to the proliferation, apoptosis, and invasion of K1 cells. ZNF703-siRNA downregulated E2F1 and MMP9 protein expression and enhanced the expression of p27 protein (P < 0.05), but had no effects on BRAF V600E protein levels. These results suggest that ZNF703 may be of potential use as a new marker for PTC prognosis and therapy that functions independent of BRAF V600E expression.
Keywords: Apoptosis; Invasion; Papillary thyroid cancer; Proliferation; ZNF703; siRNA.