Role of MMP-9 in Epithelial-Mesenchymal Transition of Thyroid Cancer

Background The purpose of this study is to explore the role and mechanism of MMP-9 in the EMT process of thyroid cancer (TC), so as to provide a basis for clinical exploration of invasion and metastasis process of TC, looking for biological markers of tumor metastasis and molecular intervention therapy.Methods Western Blot and RT-PCR were employed to detect the expression of MMP-9 in human normal thyroid cell line HT-ori3 and human TC cell lines IHH-4 (PTC), FTC-133 and 8505C. Expression levels of EMT-related markers: epithelial cell marker E-cadherin and stromal cell marker Vimentin in TGF-1-induced TC cell lines were detected by Western Blot and RT-PCR, respectively. The effects of MMP-9 down-regulation on cell invasion and metastasis were investigated by wound-healing assay and cell invasion experiment.Results The protein and mRNA expression levels of MMP-9 in TC cell lines were increased compared with human normal thyroid cell line HT-ori3. When TGF-β1 was added, the expression of EMT and Vimentin increased while the expression of E-cadherin decreased. Compared with the control group, the TC cells stably transfected with MMP-9 shRNA showed inhibited EMT, decreased Vimentin expression and increased E-cadherin expression. The induction of TGF-β1 did not promote the occurrence of EMT in TC cells which were stably transformed with MMP-9 shRNA. The addition of TGF-β1 to TC cells increased the ability of the cells to migrate and invade. Compared with the control group, the migration and invasion ability of TC cells stably transfected with MMP-9 shRNA was significantly reduced, and the induction of TGF-β1 could not restore the migration and invasion ability of cells without MMP-9.Conclusions In conclusion, we found that MMP-9 can be used as a biomarker for TC, which can promote the EMT process of TGF-β1 induced TC, and thus affecting the cell migration and invasion ability.

FAM129A regulates autophagy in thyroid carcinomas in an oncogene-dependent manner

We previously proposed that high expression of FAM129A can be used as a thyroid carcinoma biomarker in preoperative diagnostic exams of thyroid nodules. Here, we identify that FAM129A expression is increased under nutrient and growth factor depletion in a normal thyroid cell line (PCCL3), overlapping with increased expression of autophagy-related protein and inhibition of AKT/mTOR/p70S6K. Supplementation of insulin, TSH and serum to the medium was able to reduce the expression of both FAM129A and autophagy-related protein and reestablish the AKT/mTOR/p70S6K axis. To determine the direct role of FAM129A on autophagy, FAM129A was transfected into PCCL3 cells. Its overexpression induced autophagic vesicles formation, evidenced by transmission electron microscopy. Co-expression of FAM129A and mCherry-EGFP-LC3B in PCCL3 showed an increased yellow puncta formation, suggesting that FAM129Ainduces autophagy. To further confirm its role on autophagy, we knockdown FAM129A in two thyroid carcinoma cell lines (TPC1 and FTC-236). Unexpectedly, FAM129A silencing increased autophagic flux, suggesting that FAM129A inhibits autophagy in these models. We next co-transfected PCCL3 cells with FAM129A and RET/PTC1 and tested autophagy in this context. Co-expression of FAM129A and RET/PTC1 oncogene in PCCL3 cells, inhibited RET/PTC1-induced autophagy. Together, our data suggest that, in normal cells FAM129A induces autophagy in order to maintain cell homeostasis and provide substrates under starvation conditions. Instead, in cancer cells, decreased autophagy may help the cells to overcome cell death. FAM129A regulates autophagy in a cell- and/or context-dependent manner. Our data reinforce the concept that autophagy can be used as a strategy for cancer treatment.