Establishment of a prognosis predictive model for liver cancer based on expression of genes involved in the ubiquitin-proteasome pathway

BACKGROUND The ubiquitin-proteasome pathway(UPP)has been proven to play important roles in cancer.AIM To investigate the prognostic significance of genes involved in the UPP and develop a predictive model for liver cancer based on the expression of these genes.METHODS In this study,UPP-related E1,E2,E3,deubiquitylating enzyme,and proteasome gene sets were obtained from the Kyoto Encyclopedia of Genes and Genomes(KEGG)database,aiming to screen the prognostic genes using univariate and multivariate regression analysis and develop a prognosis predictive model based RESULTS Five genes(including autophagy related 10,proteasome 20S subunit alpha 8,proteasome 20S subunit beta 2,ubiquitin specific peptidase 17 like family member 2,and ubiquitin specific peptidase 8)were proven significantly correlated with prognosis and used to develop a prognosis predictive model for liver cancer.Among training,validation,and Gene Expression Omnibus sets,the overall survival differed significantly between the high-risk and low-risk groups.The expression of the five genes was significantly associated with immunocyte infiltration,tumor stage,and postoperative recurrence.A total of 111 differentially expressed genes(DEGs)were identified between the high-risk and low-risk groups and they were enriched in 20 and 5 gene ontology and KEGG pathways.Cell division cycle 20,Kelch repeat and BTB domain containing 11,and DDB1 and CUL4 associated factor 4 like 2 were the DEGs in the E3 gene set that correlated with survival.CONCLUSION We have constructed a prognosis predictive model in patients with liver cancer,which contains five genes that associate with immunocyte infiltration,tumor stage,and postoperative recurrence.

Effects of inhibition of ubiquitin-proteasome pathway on human primary leukemic cells

Though there were a lot of reports about the totally different responses to the inhibition of ubiquitin-proteasome pathway in different kinds of cell lines, much less has been known about the responses in primary human leukemic cells. In this study, the effects of inhibition of ubiquitin-proteasome pathway on human bone marrow (BM) mononuclear cells (MNCs) obtained from 10 normal persons and 8 leukemia patients were examined. The results showed that the responses obviously varied individually. Among them, BM MNCs in 3 cases of leukemic patients were extremely sensitive, demonstrated by that >90% cells were induced to undergo apoptosis within 24 h, but MNCs in 10 cases of normal persons showed resistance to the inhibition and no apoptosis was observed. Furthermore, Western blots revealed that the Bcl-2 expression was relatively high in the sensitive primary leukemia cells, and especially the cleavage of 26 ku Bcl-2 into a 22 ku fragment occurred during the induction of apoptosis. In contrast, the Bcl-2 expression was either undetectable or detectable but no cleavage of that above was observed in the cells insensitive to the inhibition of the pathway (including BM MNCs in normal persons). Together with the observations on the leukemic cell lines, these findings suggested the correlation of the specific cleavage of Bcl-2 into a shortened fragment with the sensitivity of cells to the inhibition of ubiquitin-proteasome pathway, which provides clues to the further understanding of the mechanisms of that dramatically different responses existing in different kinds of cells to the inhibition of ubiquitin-proteasome pathway.

泛素-蛋白酶体通路与神经生长因子家族的肿瘤相关性研究进展

泛素化是蛋白质翻译后重要修饰之一,是蛋白质降解信号,被泛素化修饰的蛋白质被蛋白酶识别从而被降解。近年来,人们通过对泛素化-蛋白酶体通路研究的深入,发现其是细胞内蛋白质选择性降解的主要途径,参与细胞凋亡、MHCⅠ类抗原的递呈、细胞周期以及细胞内信号传导等过程,对维持细胞的稳态具有极其重要的意义。

New insights into estrogenic regulation of O^6-methylguanine DNA-methyltransferase (MGMT) in human breast cancer cells： Co-degradation of ER-α and MGMT proteins by fulvestrant or O^6-benzylguanine indicates fresh avenues for therapy

Endocrine therapy using estrogen receptor-u （ER-α） antagonists for attenuating horm2one-driven cell proliferation is a major treatment modality for breast cancers. To exploit any DNA repair deficiencies associated with endocrine therapy, we investigated the functional and physical interactions of ER-α with O^6-methylguanine DNA methyltransferase （MGMT）, a unique DNA repair protein that confers tumor resistance to various anticancer alkylating agents. The ER-α -positive breast cancer cell lines （MCF-7, T47D） and ER- negative cell lines （MDAMB- 468, MDAMB-231）, and established inhibitors of ER-α and MGMT, namely, ICI-182,780 （Faslodex） and O^6- benzylguanine, respectively, were used to study MGMT- ER interactions. The MGMT gene promoter was found to harbor one full and two half estrogen-responsive elements （EREs） and two antioxidant-responsive elements （AREs）. MGMT expression was upregulated by estrogen, downregulated by tamoxifen in Western blot and promoter-linked reporter assays. Similarly, both transient and stable transfections of Nrf-2 （nuclear factor-erythroid 2-related factor-2） increased the levels of MGMT protein and activity 3 to 4-fold reflecting novel regulatory nodes for this dragresistance determinant. Of the different ER-α antagonists tested, the pure anti-estrogen fulvestrant was most potent in inhibiting the MGMT activity in a dose, time and ER-α dependent manner, similar to O^6-benzylguanine. Interestingly, fulvestrant exposure led to a degradation of both ER-α and MGMT proteins and O^6-benzylguanine also induced a specific loss of ER-a and MGMT proteins in MCF-7 and T47D breast cancer cells with similar kinetics. Immunoprecipitation revealed a specific association of ER-a and MGMT proteins in breast cancer cells. Furthermore, silencing of MGMT gene expression triggered a decrease in the levels of both MGMT and ER-a proteins. The involvement of proteasome in the drug-induced degradation of both proteins was also demonstrated. Fulvestrant enhanced the cytotoxicity of MGMT-targeted alkylating agents, namely, temozolomide and BCNU by 3 to 4-fold in ER-α positive cells, but not in ER-negative cells. We conclude that MGMT and ER-α proteins exist as a complex and are co-targeted for ubiquitin-conjugation and subsequent proteasomal degradation. The findings offer a clear rationale for combining alkylating agents with endocrine therapy.

Anti-tumor Action and Clinical Application of Proteasome Inhibitor

Ubiquitin-proteasome pathway mediates the degradation of cell protein, and cell cycle, gene translation and expression, antigen presentation and inflammatory development. Proteasome inhibitor can inhibit growth and proliferation of tumor cell, induce apoptosis and reverse multipledrug resistance of tumor cell, increase the sensitivity of other chemotherapeutic drugs and radiotherapy, and is a novel class of potent anti-tumor agents.

Ubiquitin-conjugating enzyme involved in the immune response caused by pathogens invasion

Ubiquitin-proteasome pathway (UPP) is a significant way of protein degradation and modification in eukaryotic cell and involved in a complex series of intracellular processes. As a key component in UPP,?ubiquitin-conjugating enzyme (E2) plays an extremely important role in ubiquitin (Ub) transferring and substrate specific recognition. Abundant evidences have proved that UPP is involved in cells immune reaction caused by pathogens and the attendance of E2 has a significant effect on host cells and pathogen. This article presents an overview of the current research on E2s that is involved in immune response caused by viruses and bacteria.

Increased expression of the 20S proteasome in peripheral blood mononuclear cells of type 2 diabetic patients

Objective To investigate the dynamic expression of the 20S proteasome in peripheral blood mononuclear cells(PBMCs)of type 2 diabetic patients without vascular complications.Methods PBMCs were prepared from 30 type 2 diabetic patients and 30 nondiabetic controls.The general indexes including weight,height and blood pressure were recorded.Fasting plasma glucose,fasting plasma insulin and glycosylated hemoglobin were measured.The protein level of the 20S proteasome was measured by Western blotting.The mRNA expression levels of the 20S proteasome β1,β2 and β5 subunits were detected by real-time PCR.Results Compared with that in the nondiabetic controls,the protein level of the 20S proteasome was significantly increased in the diabetic patients and was positively associated with glycosylated hemoglobin.Conclusion Type 2 diabetic patients without vascular complications have an increased 20S proteasome expression,the significance of which needs to be explored by further study.

Effects of ubiquitin-protea-some pathway on mouse sperm capacitation, acrosome reaction and in vitro fertilization

Chlortetracycline (CTC) fluorescence patterns were used to study changes in the patterns B and AR of mouse sperm after incubation with reagents that would block the UPP. They were the monoclonal antibody againstubiquitinated proteins——UCPi; the polyclonal antibodyagainst ubiquitin-anti-Ub, and a special inhibitor againstproteasome——ALLN. Furthermore, we treated the capaci-tated sperm or the eggs with these reagents separately and tested whether the normal in vitro fertilization was blocked or not. Results illustrate that UCP1, anti-Ub, and ALLN have little effects on sperm capacitation and acrosome reaction, but they do inhibit fusion of mouse sperm with eggs, which suggests that UPP play an important role in mouse in vitro fertilization.

The Smad pathway in transforming growth factor-β signaling

The Smad pathway is involved in transforming growth factor-b (TGF-b) signal transduction. The Smad complex binds with the promoter of target gene to modulate gene transcription. Various transcriptional coactivators and corepressors associate directly with Smads for appropriate binding of Smads to target promoters and regulation of Smads transcriptional activities. The ultimate degradation of Smads mediated by the ubiquitin-proteasome pathway (UPP) has been established as a mechanism to shut off the Smad pathway. In addition to the Smad pathway, TGF-?can also activate other signaling pathway such as the MAPK pathway. The cross-talk of the Smad pathway with other signaling pathways constitutes an important mechanism for the regulatory network of TGF-b signaling.

Large yellow croaker(Larimichthys crocea)mitofusin 2 inhibits type I IFN responses by degrading MAVS via enhanced K48‑linked ubiquitination

In mammals,mitofusin 2(MFN2)is involved in mitochondrial fusion,and suppresses the virus-induced RIG-I-like receptor(RLR)signaling pathway.However,little is known about the function of MFN2 in non-mammalian species.In the present study,we cloned an MFN2 ortholog(LcMFN2)in large yellow croaker(Larimichthys crocea).Phylogenetic analysis showed that MFN2 emerged after the divergence of amphioxus and vertebrates.The protein sequences of MFN2 were well conserved from fsh to mammals.LcMFN2 was expressed in all the tissues/organs examined at diferent levels,and its expression was upregulated in response to poly(I:C)stimulation.Overexpression of LcMFN2 inhibited MAVS-induced type I interferon(IFN)promoter activation and antiviral gene expression.In contrast,knockdown of endogenous LcMFN2 enhanced poly(I:C)induced production of type I IFNs.Additionally,LcMFN2 enhanced K48-linked polyubiquitination of MAVS,promoting its degradation.Also,overexpression of LcMFN2 impaired the cellular antiviral response,as evidenced by the increased expression of viral genes and more severe cytopathic efects(CPE)in cells infected with spring viremia of carp virus(SVCV).These results indicated that LcMFN2 inhibited type I IFN response by degrading MAVS,suggesting its negative regulatory role in cellular antiviral response.Therefore,our study sheds a new light on the regulatory mechanisms of the cellular antiviral response in teleosts.