The MST/YAP (mammalian Ste20-like kinase/Yes-associated protein 2) pathway plays an important role in hepatocellular carcinoma (HCC). Although post-translational modification-especially MST/Lats (large tumor suppressor)-mediated phosphorylation and PP1 (protein phosphatase-1)-mediated dephosphorylation-has been found to regulate the activity of YAP2, very little is known about its acetylation. In our experiments, we observed that the expression of SIRT1 is significantly upregulated in the tumor samples of the hepatocarcinoma patients, and SIRT1 mRNA level positively correlates with connective tissue growth factor (CTGF) mRNA level. We then found that SIRT1 deacetylates YAP2 protein in HCC cells and SIRT1-mediated deacetylation increases the YAP2/TEAD4 association, leading to YAP2/TEAD4 transcriptional activation and upregulated cell growth in HCC cells. Moreover, knockdown of SIRT1 blocks the cisplatin (CDDP)-induced nuclear translocation of YAP2 and enhances the chemosensitivity of HCC cells to CDDP treatment. Together, our findings reveal a new regulatory mechanism of YAP2 by the SIRT1-mediated deacetylation that may be involved in HCC tumorigenesis and drug resistance.

Oxidative stress influences cell survival and homeostasis, but the mechanisms underlying the biological effects of oxidative stress remain to be elucidated. The protein kinase MST1 (mammalian Ste20-like kinase 1) plays a major role in oxidative stress-induced cell death in primary mammalian neurons. However, the mechanisms that regulate MST1 in oxidative stress responses remain largely unknown. In the present study, we demonstrate that the protein kinase c-Abl phosphorylates MST1 at Y433, which triggers the stabilization and activation of MST1.

Reversible protein phosphorylation is a key event in numerous biological processes. Mass spectrometry (MS) is the most powerful analysis tool in modern phosphoproteomics. However, the direct MS analysis of phosphorylated proteins/peptides is still a big challenge because of the low abundance and insufficient ionization of phosphorylated proteins/peptides as well as the suppression effects of nontargets. Enrichment of phosphorylated proteins/peptides by affinity materials from complex biosamples is the most widely used strategy to enhance the MS detection. The demand of efficiently enriching phosphorylated proteins/peptides has spawned diverse affinity materials based on different enrichment principles (e.g., electronic attraction, chelating). In this review, we summarize the recent development of various affinity materials for phosphorylated proteins/peptides enrichment. We will highlight the design and fabrication of these affinity materials, discuss the enrichment mechanisms involved in different affinity materials, and suggest the future challenges and research directions in this field.

Lung metastasis and relapse in osteosarcoma (OS) patients indicate poor prognosis. Here, we identified significantly decreased expression of miR-382 in highly metastatic OS cell lines and relapsed OS samples compared to their parental cell lines and primary OS samples, respectively. In addition, our clinical data showed that the miR-382 expression level was inversely associated with relapse and positively associated with metastasis-free survival in OS patients. The overexpression of miR-382 suppressed epithelial-mesenchymal transition (EMT) and metastasis. This overexpression also decreased the cancer stem cell (CSC) population and function in OS cells. In contrast, inhibition of miR-382 stimulated EMT and metastasis and increased CSC population in OS cells. In addition, our in vivo experiments showed that the overexpression of miR-382 inhibited CSC-induced tumor formation, and the combination of miR-382 with doxorubicin prevented disease relapse in OS patients. Furthermore, we demonstrated that miR-382 exerted its tumor-suppressing potential by directly targeting Y box-binding protein 1 (YB-1) in OS. Taken together, our findings suggest that miR-382 functions as a tumor suppressor function and that the overexpression of miR-382 is a novel strategy to inhibit tumor metastasis and prevent CSC-induced relapse in OS.

LSS results in higher 5-year survival rates and better functional outcomes as indicated by MSTS scores in patients with limb osteosarcomas.

Osteosarcoma is a highly metastatic malignancy often with poor prognosis. c-Myc amplification is implicated in osteosarcoma pathogenesis. However, the role of c-myc overexpression in osteosarcoma cell invasion remains unexplored. This study showed that c-myc overexpression enhanced MG-63 and SAOS-2 osteosarcoma cell invasion. Treatment of MEK inhibitor PD98059 or PI3K inhibitor LY294002 decreased cell invasion along with downregulation of MMP-2 and MMP-9 expression. c-Myc overexpression stimulated MEK-ERK pathway whereas inhibited the activity of PI3K-AKT pathway. Specifically, inhibition of MEK-ERK pathway by PD98509 blocked the enhancement effect on cell invasion as well as MMP-2 and MMP-9 expression. The present study demonstrates that c-myc overexpression promotes osteosarcoma cell invasion, probably via activation of MEK-ERK pathway.

Cadherin-6 (CDH6) is aberrantly expressed in cancer and closely associated with tumor progression. However, the functions of CDH6 in human osteosarcoma and the molecular mechanisms underlying CDH6 in osteosarcoma oncogenesis remain poorly understood. In this work, we assessed the role of CDH6 in human osteosarcoma and identified that the expression of CDH6 was closely related with the overall survival and poor prognosis of osteosarcoma patients. MicroRNAs (miRNAs) have been implicated as important epigenetic regulators during the progression of osteosarcoma. Using dual-luciferase reporter assays, we showed that miR-223-3p suppresses CDH6 expression by directly binding to the 3' UTR of CDH6. miR-223-3p overexpression significantly inhibited cell invasion, migration, growth, and proliferation by suppressing the CDH6 expression in vivo and in vitro. Besides, CDH6 overexpression in the miR-223-3p-transfected osteosarcoma cells effectively rescued the inhibition of cell invasion, migration, growth, and proliferation mediated by miR-223-3p. Additionally, Kaplan-Meier analysis suggests that the expression of miR-223-3p predicts favorable clinical outcomes for osteosarcoma patients. Moreover, the expression of miR-223-3p was downregulated in osteosarcoma patients and was negatively associated with the expression of CDH6. Collectively, these data highlight that miR-223-3p/CDH6 axis is an important novel pleiotropic regulator and could early predict the metastatic potential in human osteosarcoma treatments.

Dysregulation of miRNAs is involved in osteosarcoma (OS). Here, we demonstrate that miR-382 is decreased in specimens of OS patients with a poor chemoresponse compared to those with a good chemoresponse. In addition, our clinical data show that decreased miR-382 was associated with poor survival in OS patients. Overexpression of miR-382 inhibited cell growth and chemoresistance by targeting KLF12 and HIPK3, respectively. In contrast, inhibition of miR-382 or overexpression of target genes stimulated OS cell growth and chemoresistance both in vitro and in vivo. Taken together, these findings suggest that miR-382 is a tumor suppressor miRNA and induction of miR-382 is a potential strategy to inhibit OS progression.