Down-regulation of PPM 1 H in papillary thyroid cancer inhibits cancer cell proliferation and invasion

Recent studies have confirmed that aberrant expression of protein phosphatase 1H (PPM1H) plays multiple roles in various types of cancers, but a potential role in papillary thyroid cancer (PTC) has not been studied. This study aimed to explore the clinical characteristics of PPM1H in PTC and its roles in the proliferation and invasion of PTC cells. Down-regulation of PPM1H expression was frequently detected in primary PTC tumor tissues compared with those in non-tumor tissues, and it was significantly associated with tumor size (P = 0.048), lymph node metastasis (P = 0.016), and clinical stage (P = 0.033). Knockdown of PPM1H in SW579 cells, a human PTC cell line, decreased E-cadherin level, while increasing expression of Vimentin. After PPM1H inhibition, SW579 cells exhibited morphological change from an epithelial cobblestone phenotype to an elongated fibroblastic phenotype. Wound healing and transwell assays were used to analyze the migratory and invasive ability of cells, and it was found that SW579 cells had increased migratory and invasive ability after PPM1H knockdown. Furthermore, MTT and colony formation assays showed that down-regulation of PPM1H promoted cell proliferation (P<0.05). These results suggest that low expression of PPM1H is associated with increased cancer cell proliferation and invasion and that PPM1H may act as a tumor suppressor in PTC.