Expression of Pax8 is decreased and bortezomib does not increase the iodine uptake in thyroid carcinoma cells

Fundamental treatment for papillary thyroid carcinoma (PTC) involves total or subtotal thyroidectomy. Iodine-131 (131I) is routinely utilized to target remnant thyroid cancer and metastasis after thyroidectomy. The effectiveness of other therapeutic modalities remains unsatisfactory; thus, these patients have a poor prognosis. The manner in which the ability of 131I uptake can be improved is vital for their prognosis. Bortezomib has been used as a re-differentiation agent for the treatment of patients with multiple myeloma; however, little is reported about the role of bortezomib in thyroid cancer. To evaluate the therapeutic potential of bortezomib in a human PTC cell line, expression of paired-box 8 (Pax8) protein was determined using Western blot in PTC, normal thyroid, and anaplastic/undifferentiated thyroid carcinoma (ATC) cells. The expression of Pax8 protein in PTC cells pretreated with bortezomib was determined using the same method. Iodine uptake was determined using 131I radioactivity assay. The level of Pax8 protein in normal thyroid cells was significantly higher than in PTC (P < 0.05) and ATC cells (P < 0.05); its expression in PTC cells was also significantly higher than in ATC cells (P < 0.05). The PTC cells in the bortezomib-treated group showed a higher expression of Pax8 protein than the control group (P < 0.05). These findings indicate that bortezomib can increase the expression of Pax8, but does not significantly increase the iodine uptake of PTC cells.