MON-532 Characterization of the Angiogenic Factor SFRP2 in Papillary Thyroid Carcinoma

Abstract

Over the last decade, there has been an average annual increase of 3.1% in thyroid cancer diagnosis in the U.S. Papillary thyroid carcinoma (PTC) accounts for 80% of all thyroid cancer diagnoses. However, few molecular markers exist to identify clinically aggressive phenotypes. The angiogenic factor, secreted frizzled-related protein 2 (SFRP2), is associated with a poor prognosis in several malignancies including breast cancer and melanoma. The role of SFRP2 in PTC has yet to be investigated. The aims of this study were to determine the differential expression of SFRP2 in PTC, benign thyroid adenomas, normal thyroid tissue (from patients without cancer), and normal adjacent tissue (NAT) (non-cancerous tissue from patients with PTC) and investigate the role of SFRP2 in tumor development in two PTC cell lines, PTC classical variant (PTC-CV) and PTC follicular variant (PTC-FV), upon treatment with a humanized anti-SFRP2 monoclonal antibody (hSFRP2 mAb). Immunohistochemistry (IHC) was performed using human tissue protein microarrays including 226 PTC, 79 benign adenomas, 112 NAT, and 30 normal thyroid tissue samples. In-vitro proliferation and apoptosis experiments were performed on MDA-T41 (PTC-CV) and MDA-T68 (PTC-FV) cell lines by treating with hSFRP2 mAb, Xolair IgG control, and a vehicle control. SFRP2 expression was significantly higher in PTC compared with benign adenomas and normal thyroid (mean expression scores 9, 6, and 1, respectively; p<0.05). SFRP2 expression was significantly higher in NAT than normal thyroid (mean expression score 4 and 0, respectively, p<0.05). Apoptotic rates were increased by 40% and 62% in the PTC-CV hSFRP2 mAb treatment group compared with the Xolair and vehicle treatment groups, respectively (p<0.05). Apoptotic rates were increased by 126% and 59% in the PTC-FV hSFRP2 mAb treatment group compared with the Xolair and vehicle treatment groups, respectively (p<0.05). Treatment with hSFRP2 mAb had no significant effect on proliferation in either cell line. In conclusion, SFRP2 expression is significantly higher in PTC than in benign adenomas and normal thyroid tissue. SFRP2 expression in NAT is significantly higher than in normal thyroid tissue and not significantly different from benign adenomas. SFRP2 expression in nonmalignant tissue adjacent to PTC could be due to expression in the tumor microenvironment. Treatment with a novel hSFPR2 mAb increases apoptotic rates in two different PTC cell lines. These data suggest that SFPR2 is involved in tumorigenesis of PTC.