ABSTRACT
This corrects the article DOI: 10.1038/onc.2014.445.
ABSTRACT
The SET protein is a potent inhibitor of protein phosphatase 2A (PP2A). Here, we report the oncogenic role of SET in hepatocarcinogenesis, clinical aggressiveness and anti-hepatocellular carcinoma (HCC) therapeutics. By analyzing samples obtained from 147 HCC patients, we found that SET overexpression was detected specifically in 30.6% HCC tumor samples, and was significantly associated with worse clinical features and high p-Akt expression in HCC tumors. Co-expression of SET and Akt predicted shorter post-operative recurrence-free survival in this cohort (P=0.045). Furthermore, SET was significantly associated with cell growth and hepatosphere formation. To elucidate the anti-HCC potential of targeting SET, we generated a novel SET antagonist, EMQA (N(4)-(3-ethynylphenyl)-6,7-dimethoxy-N(2)-(4-phenoxyphenyl) quinazoline-2,4-diamine). EMQA enhanced PP2A activity via disrupting SET-PP2Ac (catalytic domain of PP2A) binding in HCC cells, which restored PP2A-mediated p-Akt downregulation and promoted HCC cell death. In HCC cells or recombinant proteins expressing the N- and C- truncated forms of SET, only the C-terminal SET was required for EMQA targeting. Furthermore, combining sorafenib and EMQA showed good synergism in inhibiting HCC survival. Our findings suggested the oncogenic role of SET and the adverse prognostic value of SET overexpression in HCC. This alteration defines a subgroup of HCC patients who could benefit from SET antagonists, such as EMQA.
Subject(s)
Carcinoma, Hepatocellular/drug therapy , Histone Chaperones/genetics , Liver Neoplasms/drug therapy , Prognosis , Quinazolines/administration & dosage , Transcription Factors/genetics , Animals , Apoptosis/drug effects , Carcinoma, Hepatocellular/genetics , Carcinoma, Hepatocellular/pathology , Cell Line, Tumor , Cell Proliferation/drug effects , DNA-Binding Proteins , Female , Gene Expression Regulation, Neoplastic/drug effects , Histone Chaperones/antagonists & inhibitors , Humans , Liver Neoplasms/genetics , Liver Neoplasms/pathology , Male , Mice , Niacinamide/administration & dosage , Niacinamide/analogs & derivatives , Phenylurea Compounds/administration & dosage , Quinazolines/chemical synthesis , Sorafenib , Transcription Factors/antagonists & inhibitors , Xenograft Model Antitumor AssaysABSTRACT
Epithelial-to-mesenchymal transition (EMT) is well known to involve in tumor invasion and metastasis. Src homology region 2 domain-containing phosphatase 1 (SHP-1) functions as a potent tumor suppressor and also acts as a negative regulator of p-STAT3(Tyr705) oncogenic signaling. However, little is known about the molecular mechanism(s) through which SHP-1 regulates EMT during hepatocellular carcinoma (HCC) progression. Here we first reported that endogenous SHP-1 protein levels were significantly downregulated in cells with mesenchymal characteristics and negatively correlated with p-STAT3(Tyr705) and vimentin but positively correlated with E-cadherin. SHP-1 overexpression abolished transforming growth factor-ß1 (TGF-ß1)-induced p-STAT3(Tyr705) and EMT, as well inhibited migration and invasion but further rescued by signal transducer and activator of transcription factor 3 (STAT3) overexpression. Depletion of SHP-1 could induce a more increase in TGF-ß1-induced p-STAT3(Tyr-705) and EMT characteristics, further supporting the mechanism that suppression of TGF-ß1-induced EMT is dependent on SHP-1-mediated STAT3 inactivation. Constitutively overexpressed SHP-1 tyrosine phosphatase activity by D61A-mutated SHP-1 markedly reduced TGF-ß1-induced p-STAT3(Tyr705) and EMT features but was not altered by C453S catalytic-dead mutant SHP-1. Consequently, SHP-1 acted as a powerful suppressor in preventing EMT by exerting its tyrosine phosphatase activity that directly downregulated p-STAT3(Tyr705). Most notably, we discovered a novel SHP-1 agonist SC-43 better than sorafenib to exert more potent anti-EMT effects in vitro as well as anti-metastatic growth in vivo. In conclusion, SHP-1 is a potent suppressor of HCC EMT and metastasis, thus highlighting that SC-43-SHP-1 axis may serve as a potential therapeutic target that antagonized p-STAT3(Tyr705) and thereby prevented HCC EMT and metastasis.
Subject(s)
Carcinoma, Hepatocellular/enzymology , Epithelial-Mesenchymal Transition , Liver Neoplasms/enzymology , Lung Neoplasms/enzymology , Protein Tyrosine Phosphatase, Non-Receptor Type 6/physiology , Animals , Carcinoma, Hepatocellular/secondary , Cell Line, Tumor , Humans , Liver Neoplasms/pathology , Lung Neoplasms/secondary , Mice, Nude , Neoplasm Transplantation , STAT3 Transcription Factor/metabolismABSTRACT
We investigated the molecular mechanisms underlying the effect of sorafenib and SC-59, a novel sorafenib derivative, on hepatocellular carcinoma (HCC). Sorafenib activated autophagy in a dose- and time-dependent manner in the HCC cell lines PLC5, Sk-Hep1, HepG2 and Hep3B. Sorafenib downregulated phospho-STAT3 (P-STAT3) and subsequently reduced the expression of myeloid cell leukemia-1 (Mcl-1). Inhibition of Mcl-1 by sorafenib resulted in disruption of the Beclin 1-Mcl-1 complex; however, sorafenib did not affect the amount of Beclin 1, suggesting that sorafenib treatment released Beclin 1 from binding with Mcl-1. Silencing of SHP-1 by small interference RNA (siRNA) reduced the effect of sorafenib on P-STAT3 and autophagy. Ectopic expression of Mcl-1 abolished the effect of sorafenib on autophagy. Knockdown of Beclin 1 by siRNA protected the cells from sorafenib-induced autophagy. Moreover, SC-59, a sorafenib derivative, had a more potent effect on cancer cell viability than sorafenib. SC-59 downregulated P-STAT3 and induced autophagy in all tested HCC cell lines. Furthermore, our in vivo data showed that both sorafenib and SC-59 inhibited tumor growth, downregulated P-STAT3, enhanced the activity of SHP-1 and induced autophagy in PLC5 tumors, suggesting that sorafenib and SC-59 activate autophagy in HCC. In conclusion, sorafenib and SC-59 induce autophagy in HCC through a SHP-1-STAT3-Mcl-1-Beclin 1 pathway.
Subject(s)
Antineoplastic Agents/toxicity , Apoptosis Regulatory Proteins/metabolism , Apoptosis/drug effects , Membrane Proteins/metabolism , Niacinamide/analogs & derivatives , Phenylurea Compounds/pharmacology , Phenylurea Compounds/toxicity , Proto-Oncogene Proteins c-bcl-2/metabolism , Animals , Antineoplastic Agents/therapeutic use , Apoptosis Regulatory Proteins/antagonists & inhibitors , Apoptosis Regulatory Proteins/genetics , Beclin-1 , Carcinoma, Hepatocellular/drug therapy , Carcinoma, Hepatocellular/metabolism , Carcinoma, Hepatocellular/pathology , Cell Line, Tumor , Down-Regulation/drug effects , Hep G2 Cells , Humans , Liver Neoplasms/metabolism , Liver Neoplasms/pathology , Membrane Proteins/antagonists & inhibitors , Membrane Proteins/genetics , Mice , Mice, Nude , Myeloid Cell Leukemia Sequence 1 Protein , Niacinamide/therapeutic use , Niacinamide/toxicity , Phenylurea Compounds/chemistry , Phenylurea Compounds/therapeutic use , Phosphorylation , Protein Tyrosine Phosphatase, Non-Receptor Type 6/antagonists & inhibitors , Protein Tyrosine Phosphatase, Non-Receptor Type 6/genetics , Protein Tyrosine Phosphatase, Non-Receptor Type 6/metabolism , RNA Interference , RNA, Small Interfering/metabolism , STAT3 Transcription Factor/metabolism , Sorafenib , Transplantation, HeterologousABSTRACT
BACKGROUND: Fatty acid synthase (FASN) is highly upregulated in human prostate carcinomas. Inhibition of FASN could arrest cell cycle and trigger apoptosis rapidly, implying the reliance of cancer cell survival on FASN. However, little is known about the effect of C75, a FASN inhibitor, and siFASN (that is, small interfering RNA targeted at FASN) on prostate cancer in living subjects. METHODS: We used C75 and siFASN to mediate the endogenous fatty acid metabolism in LNCaP human prostate cancer cells stably expressing herpes simplex virus type 1 thymidine kinase (HSV1-tk) and luciferase (luc) reporter genes, and assessed the effect of FASN blockade with different schedules of administration on tumor growth using noninvasive molecular imaging. RESULTS: FASN blockade exhibited the proliferative inhibition and induced G1-phase cell cycle arrest of LNCaP cells. For in vivo studies, the tumor growth inhibition by C75 (total 120 mgkg(-1); 30 mgkg(-1) once a week or 15 mgkg(-1) twice a week for 4 weeks) and siFASN (1.4 mgkg(-1) every alternate day up to 16 days) treatments were 80% and 70%, respectively, compared with that of the control. CONCLUSION: The results suggest that C75 may be superior to siFASN in anticancer effect on prostate cancer.
