Stomatin-like protein 2 is associated with the clinicopathological features of human papillary thyroid cancer and is regulated by TGF-β in thyroid cancer cells.

Papillary thyroid cancer (PTC) accounts for 80-90% of all cases of thyroid malignancies. Stomatin-like protein 2 (SLP-2) is a novel member of the stomatin superfamily and is found in several types of human tumors. However, whether it is expressed in human PTC is unknown. In the present study, we aimed to explore the diagnostic value of SLP-2 in patients with PTC and to investigate whether SLP-2 expression is regulated by transforming growth factor-β (TGF-β), a cytokine which plays an important role in PTC tumorigenesis. A total of 107 patients consisting of 99 cases of classical and 8 cases of follicular variant PTC was examined. The expression of SLP-2 mRNA and protein was examined by immunohistochemistry (IHC) and qPCR, respectively. We found that SLP-2 was overexpressed in human PTC. The expression of SLP-2 was significantly associated with clinicopathological features of the PTC cases. Particularly, increased SLP-2 expression was mainly correlated with primary tumors >1 cm in size, with late stage tumors and with metastatic lymph nodes. The expression of SLP-2 was correlated with the expression of Ki-67, a cell proliferation marker, in PTC tissues as detected by IHC. SLP-2 was upregulated by TGF-β1 in PTC cells as evaluated by western blotting. The present data revealed for the first time that patients with PTC exhibited SLP-2 overexpression that was associated with clinicopathological features. The correlation between SLP-2 expression and proliferation marker Ki-67 may be characteristic of PTC and may reflect PTC progression. SLP-2 was upregulated by TGF-β1, indicating a possible role of SLP-2 in PTC tumorigenesis. Our data suggest that SLP-2 may be considered as a useful diagnostic marker and therapeutic target for PTC.