| BackgroundThyroid carcinoma is the most common classical endocrine malignancy and its incidence is rising rapidly, the leading cause of thyroid carcinoma-related mortality is cancer metastasis, which can be artificially created by multi-steps, including cell adhesion to the extracellular matrix (ECM), ECM degradation and cell migration, invasion and macrometastasis. The special AT-rich sequence-binding protein1(SATB1) is a genome organizer protein which regulates the spatiotemporal expression of numerous genes that involved in T cellproliferation, development and differentiation. SATB1has recently attracted considerable attention in cancer research and its overexpression is a frequent event in various cancers, such as breast cancer, laryngeal cancer, gastric cancer and liver cancer.However, the role it plays in thyroid carcinoma has never been reported around the world. In this study, we first examed the expression pattern of SATB1in thyroid cancer tissues, and then studied the relationship between SATB1expression and the clinical features. We also researched the effect of SATB1on the metastasis process in thyroid cancer. Lastly, we discussed the underlying mechanisms by which SATB1promoted metastasis of thyroid cancer.MethodsTotally85thyroid carcinoma tissue specimens from patients who underwent open surgery in our hospital among June2009～December2012were involved in the research. SATB1was detected in the thyroid carcinoma tissues and their corresponding paracancerous tissues by RT-PCR and IHC methods. SATB1expression plasmid was constructed and transfected into SW-597cells using liposome, the transfection efficiency and the expression of mesenchymal marker Vimentin and epithelial marker E-cadherin were detected by qRT-PCR and Western blot. The expressions of Twist1, Snail1, MMP2, MMP9, IL-6and IL-8were detected by qRT-PCR. Cellular morphology change was assessed under an inverted microscope. Wound healing experiment and Transwell assay were carried out to study the role of SATB1on the migratory and invasive ability of SW-597cells. Western blotting examed the p-Akt level after SATB1overexpressed. LY294002and PBS (control) were added into SW-597cells after transfected with SATB1expression plasmid, then, the migratory and invasive ability of SW-597cells were estimated using Transwell assay.ResultsIHC analysis showed that SATB1protein predominantly expressed in the nucleus, no positive staining was detected in the cytoplasm. Low expressions of SATB1were detected in paracancerous tissues, however, the cancer tissues had more positive staining than their paracancerous tissues (68.2%,p<0.05). SATB1protein expression in thyroid carcinoma tissue was not correlated with the gender, age, tumor diameter and tumor numbers (p>0.05). In group with lymph node metastasis, group with Ⅲ、Ⅳ clinical stages, SATB1protein expression level was significantly higher than that in the nolymph node metastasis, I and II clinical stage group (p<0.05). A SATB1expression plasmid was transfected into SW-597cells successfully as determined by qRT-PCR (55times) and Western blotting, SATB1overexpression decreased the expression of E-cadherin by68.20±0.72%(p<0.05), however,it increased the expression of Vimentin by3.71±0.93times(p<0.05); After overexpression of SATB1, SW-597cells exhibited some morphological changes including junctional disruption and cell elongation. Wound healing experiment found an increased healing rate in SW-597cells transfected with SATB1by28%. As shown in cell migration assay, the migrating number of SW-597cells (196±10) transfected with SATB1expression plasmids was increased as compared with control group (107±12)(p<0.01). Similarly, invasion of transfected cells through Matrigel matrices was increased as control (p<0.01). Elevated level of phosphorylated Akt was found in SW-597cells transfected with SATB1as compared with control group although the total Akt almost the same in the two groups. SW-597cells transfected with SATB1were treated with PI3K inhibitor, LY294002for12h, after that, Western blotting indicated that LY294002inhibited the migratory and invasive ability of SW-597cells, which suggested that PI3K/Akt signaling is necessary for the metastasis process in SW-597cells.ConclusionsWe conclude that SATB1is concerned with the metastasis of thyroid carcinoma, overexpression of SATB1induces EMT in human thyroid cancer cells. We propose that PI3K/Akt signalling pathway may play an important role in the pro-matastasisi process of SATB1in human thyroid cancer cells. Further study the molecule mechanism and the effect of SATB1on invasion in vivo, may provide new strategies for treatment of thyroid cancer metastasis. |
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