Usp7 regulates Hippo pathway through deubiquitinating the transcriptional coactivator Yorkie

Silence of yki by miR-7 regulates the Hippo pathway

The Hippo signaling pathway governs organ size via coordinating cell proliferation and apoptosis, and its dysregulation causes congenital diseases and cancers. The homeostasis of Hippo pathway is achieved through multiple post translational modifications. Through Drosophila genetic screening, we found that miRNAs were also involved in Hippo pathway regulation. Here, we showed that overexpression of miR-7 resulted in small wings, which were neutralized by miR-7-sponge (miR-7-sp) co-expression. Mechanistically, miR-7 inhibited the expression of Hippo pathway target genes. Epistatic analyses revealed that miR-7 modulated Hippo pathway through the transcriptional cofactor Yorkie (Yki). Consistently, overexpression of miR-7 decreased Yki protein. We further found a seed sequence of miR-7 in the yki 3'-UTR region. In addition, we discovered that miR-7 was a transcriptional target of Yki. Thus, a negative feedback loop existed for fine tuning Hippo pathway activity. Taken together, our findings uncovered a novel mechanism by which Yki was silenced by miR-7 for Hippo pathway regulation.

MiR-135b promotes HCC tumorigenesis through a positive-feedback loop

Hippo pathway plays critical roles in cell proliferation and apoptosis and its dysregulation leads to various types of cancers, including hepatocellular carcinoma (HCC). However, the mechanism maintaining Hippo pathway homeostasis still remains unclear. In this study, we discovered that the expression of miR-135b is apparently upregulated in HCC tissues and HCC cell lines. The level of miR-135b was positively correlated with HCC stages and negatively correlated with the survival of HCC patients, suggesting an oncogenic role of miR-135b in HCC progression. Similarly, miR-135b mimic promoted HCC cell proliferation and migration, whereas its inhibitor played an opposite role. Mechanistically, we identified a seed sequence of miR-135b in the MST1 3'-UTR region. MiR-135b inhibited the Hippo pathway by silencing MST1 expression. Additionally, we revealed that miR-135b was a transcriptional target of the Hippo pathway. Based on these data, we propose that a positive-feedback axis of MST1-YAP-miR-135b exists for HCC aggravation. Our study not only deepens the insight into the Hippo pathway homeostasis, but also suggests miR-135b as a potential prognosis biomarker and therapeutic target for HCC.

WD repeat-containing protein 1 maintains β-Catenin activity to promote pancreatic cancer aggressiveness

Background

The molecular signature underlying pancreatic ductal adenocarcinoma (PDAC) progression may include key proteins affecting the malignant phenotypes. Here, we aimed to identify the proteins implicated in PDAC with different tumour-node-metastasis (TNM) stages.

Methods

Eight-plex isobaric tags coupled with two-dimensional liquid chromatography–tandem mass spectrometry were used to analyse the proteome of PDAC tissues with different TNM stages. A loss-of-function study was performed to evaluate the oncogenic roles of WD repeat-containing protein 1 (WDR1) in PDAC. The molecular mechanism by which WDR1 promotes PDAC progression was studied by real-time qPCR, Western blotting, proximity ligation assay and co-immunoprecipitation.

Results

A total of 5036 proteins were identified, and 4708 proteins were quantified with high confidence. Compared with normal pancreatic tissues, 37 proteins were changed significantly in PDAC tissues of different stages. Moreover, 64 proteins were upregulated or downregulated in a stepwise manner as the TNM stages of PDAC increased, and 10 proteins were related to tumorigenesis. The functionally uncharacterised protein, WDR1, was highly expressed in PDAC and predicted a poor prognosis. WDR1 knockdown suppressed PDAC tumour growth and metastasis in vitro and in vivo. Moreover, WDR1 knockdown repressed the activity of the Wnt/β-Catenin pathway; ectopic expression of a stabilised form of β-Catenin restored the suppressive effects of WDR1 knockdown. Mechanistically, WDR1 interacted with USP7 to prevent ubiquitination-mediated degradation of β-Catenin.

Conclusion

Our study identifies several previous functional unknown proteins implicated in the progression of PDAC, and provides new insight into the oncogenic roles of WDR1 in PDAC development.

Big data-driven precision medicine: Starting the custom-made era of iatrology

Precision medicine is a new therapeutic concept and method emerging in recent years. The rapid development of precision medicine is driven by the development of omics related technology, biological information and big data science. Precision medicine is provided to implement precise and personalized treatment for diseases and specific patients. Precision medicine is commonly used in the diagnosis, treatment and prevention of various diseases. This review introduces the application of precision medicine in eight systematic diseases of the human body, and systematically presenting the current situation of precision medicine. At the same time, the shortcomings and limitations of precision medicine are pointed out. Finally, we prospect the development of precision medicine.

Dual functions of Rack1 in regulating Hedgehog pathway

Hedgehog (Hh) pathway plays multiple roles in many physiological processes and its dysregulation leads to congenital disorders and cancers. Hh regulates the cellular localization of Smoothened (Smo) and the stability of Cubitus interruptus (Ci) to fine-tune the signal outputs. However, the underlying mechanisms are still unclear. Here, we show that the scaffold protein Rack1 plays dual roles in Hh signaling. In the absence of Hh, Rack1 promotes Ci and Cos2 to form a Ci–Rack1–Cos2 complex, culminating in Slimb-mediated Ci proteolysis. In the presence of Hh, Rack1 dissociates from Ci–Rack1–Cos2 complex and forms a trimeric complex with Smo and Usp8, leading to Smo deubiquitination and cell surface accumulation. Furthermore, we find the regulation of Rack1 on Hh pathway is conserved from Drosophila to mammalian cells. Our findings demonstrate that Rack1 plays dual roles during Hh signal transduction and provide Rack1 as a potential drug target for Hh-related diseases.

Correction of the tumor suppressor Salvador homolog-1 deficiency in tumors by lycorine as a new strategy in lung cancer therapy

Salvador homolog-1 (SAV1) is a tumor suppressor required for activation of the tumor-suppressive Hippo pathway and inhibition of tumorigenesis. SAV1 is defective in several cancer types. SAV1 deficiency in cells promotes tumorigenesis and cancer metastasis, and is closely associated with poor prognosis for cancer patients. However, investigation of therapeutic strategies to target SAV1 deficiency in cancer is lacking. Here we found that the small molecule lycorine notably increased SAV1 levels in lung cancer cells by inhibiting SAV1 degradation via a ubiquitin-lysosome system, and inducing phosphorylation and activation of the SAV1-interacting protein mammalian Ste20-like 1 (MST1). MST1 activation then caused phosphorylation, ubiquitination, and degradation of the oncogenic Yes-associated protein (YAP), therefore inhibiting YAP-activated transcription of oncogenic genes and tumorigenic AKT and NF-κB signal pathways. Strikingly, treating tumor-bearing xenograft mice with lycorine increased SAV1 levels, and strongly inhibited tumor growth, vasculogenic mimicry, and metastasis. This work indicates that correcting SAV1 deficiency in lung cancer cells is a new strategy for cancer therapy. Our findings provide a new platform for developing novel cancer therapeutics.

A novel lncRNA PLK4 up-regulated by talazoparib represses hepatocellular carcinoma progression by promoting YAP-mediated cell senescence

A growing number of studies recognize that long non‐coding RNAs (lncRNAs) are essential to mediate multiple tumorigenic processes, including hepatic tumorigenesis. However, the pathological mechanism of lncRNA‐regulated liver cancer cell growth remains poorly understood. In this study, we identified a novel function lncRNA, named polo‐like kinase 4 associated lncRNA (lncRNA PLK4, GenBank Accession No. RP11‐50D9.3), whose expression was dramatically down‐regulated in hepatocellular carcinoma (HCC) tissues and cells. Interestingly, talazoparib, a novel and highly potent poly‐ADP‐ribose polymerase 1/2 (PARP1/2) inhibitor, could increase lncRNA PLK4 expression in HepG2 cells. Importantly, we showed that talazoparib‐induced lncRNA PLK4 could function as a tumour suppressor gene by Yes‐associated protein (YAP) inactivation and induction of cellular senescence to inhibit liver cancer cell viability and growth. In summary, our findings reveal the molecular mechanism of talazoparib‐induced anti‐tumor effect, and suggest a potential clinical use of talazoparib‐targeted lncRNA PLK4/YAP‐dependent cellular senescence for the treatment of HCC.

Chromatin accessibility is associated with the changed expression of miRNAs that target members of the Hippo pathway during myoblast differentiation

miRNAs reportedly participate in various biological processes, such as skeletal muscle proliferation and differentiation. However, the regulation of differentially expressed (DE) miRNAs and their function in myogenesis remain unclear. Herein, miRNA expression profiles and regulation during C2C12 differentiation were analyzed in relation to chromatin states by RNA-seq, ATAC-seq, and ChIP-seq. We identified 19 known and nine novel differentially expressed miRNAs at days 0, 1, 2, and 4. The expression of the differentially expressed miRNAs was related to the chromatin states of the 113 surrounding open chromatin regions defined by ATAC-seq peaks. Of these open chromatin regions, 44.25% were colocalized with MyoD/MyoG binding sites. The remainder of the above open chromatin regions were enriched with motifs of the myoblast-expressed AP-1 family, Ctcf, and Bach2 transcription factors (TFs). Additionally, the target genes of the above differentially expressed miRNAs were enriched primarily in muscle growth and development pathways, especially the Hippo signaling pathway. Moreover, via combining a loss-of-function assay with Q-PCR, western blotting, and immunofluorescence, we confirmed that the Hippo signaling pathway was responsible for C2C12 myoblast differentiation. Thus, our results showed that these differentially expressed miRNAs were regulated by chromatin states and affected muscle differentiation through the Hippo signaling pathway. Our findings provide new insights into the function of these differentially expressed miRNAs and the regulation of their expression during myoblast differentiation.

Parthenolide inhibits ubiquitin-specific peptidase 7 (USP7), Wnt signaling, and colorectal cancer cell growth

It has been well-established that the deubiquitinating enzyme ubiquitin-specific peptidase 7 (USP7) supports cancer growth by up-regulating multiple cellular pathways, including Wnt/β-catenin signaling. Therefore, considerable efforts are directed at identifying and developing USP7 inhibitors. Here, we report that sesquiterpene lactone parthenolide (PTL) inhibits USP7 activity, assessed with deubiquitinating enzyme activity assays, including fluorogenic Ub-AMC/Ub-Rho110, Ub-VME/PA labeling, and Di-Ub hydrolysis assays. Further investigations using cellular thermal shift (CETSA), surface plasmon resonance (SPR), and mass spectrum (MS) assays revealed that PTL directly interacts with USP7. Consistent with the role of USP7 in stimulating Wnt signaling and carcinogenesis, PTL treatment inhibited the activity of Wnt signaling partly by destabilizing β-catenin. Moreover, using cell viability assays, we found that PTL suppresses the proliferation of colorectal cancer cells and induces apoptosis in these cells. Additionally, we examined the effects of two other sesquiterpene lactones (costunolide and α-santonin) on USP7 and Wnt signaling and found that α-methylene-γ-butyrolactone may provide a scaffold for future USP7 inhibitors. In summary, our findings reveal that PTL inhibits USP7 activity, identifying a potential mechanism by which PTL suppresses Wnt/β-catenin signaling. We further suggest that sesquiterpene lactones might represent a suitable scaffold for developing USP7 inhibitors and indicate that PTL holds promise as an anticancer agent targeting aberrant USP7/Wnt signaling.

Usp10 Modulates the Hippo Pathway by Deubiquitinating and Stabilizing the Transcriptional Coactivator Yorkie

The Hippo signaling pathway is an evolutionarily conserved regulator that plays important roles in organ size control, homeostasis, and tumorigenesis. As the key effector of the Hippo pathway, Yorkie (Yki) binds to transcription factor Scalloped (Sd) and promotes the expression of target genes, leading to cell proliferation and inhibition of apoptosis. Thus, it is of great significance to understand the regulatory mechanism for Yki protein turnover. Here, we provide evidence that the deubiquitinating enzyme ubiquitin-specific protease 10 (Usp10) binds Yki to counteract Yki ubiquitination and stabilize Yki protein in Drosophila S2 cells. The results in Drosophila wing discs indicate that silence of Usp10 decreases the transcription of target genes of the Hippo pathway by reducing Yki protein. In vivo functional analysis ulteriorly showed that Usp10 upregulates the Yki activity in Drosophila eyes. These findings uncover Usp10 as a novel Hippo pathway modulator and provide a new insight into the regulation of Yki protein stability and activity.

STUB1 suppresseses tumorigenesis and chemoresistance through antagonizing YAP1 signaling

Yes-associated protein (YAP) is a component of the canonical Hippo signaling pathway that is known to play essential roles in modulating organ size, development, and tumorigenesis. Activation or upregulation of YAP1, which contributes to cancer cell survival and chemoresistance, has been verified in different types of human cancers. However, the molecular mechanism of YAP1 upregulation in cancer is still unclear. Here we report that the E3 ubiquitin ligase STUB1 ubiquitinates and destabilizes YAP1, thereby inhibiting cancer cell survival. Low levels of STUB1 expression were correlated with increased protein levels of YAP1 in human gastric cancer cell lines and patient samples. Moreover, we revealed that STUB1 ubiquitinates YAP1 at the K280 site by K48-linked polyubiquitination, which in turn increases YAP1 turnover and promotes cellular chemosensitivity. Overall, our study establishes YAP1 ubiquitination and degradation mediated by the E3 ligase STUB1 as an important regulatory mechanism in gastric cancer, and provides a rationale for potential therapeutic interventions.

MicroRNA let-7a inhibits proliferation of breast cancer cell by downregulating USP32 expression

Background

The present study aimed to investigate the effect of microRNA (miR) let-7a on ubiquitin specific protease 32 (USP32) expression and its potential function in MCF-7 breast cancer (BCa) cell line.

Methods

BCa MCF-7 cells were transfected with hsa-miR let-7a mimics or inhibitors, then the USP32 expression was evaluated using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot analysis in the transfected cells. USP32 as a target regulated by miR let-7a was confirmed via Dual-luciferase reporter assay. The effects of miR let-7a on the viability were determined using MTT assay and colony formation analysis.

Results

Western blot analysis revealed that miR let-7a mimics dramatically decreased the USP32 protein expression, whereas miR let-7a inhibitors increased the protein expression of USP32 compared with their controls in the MCF-7 cells. Dual-luciferase reporter assay showed that miR let-7a mimics could directly target the 3'-untranslated region (UTR) of USP32. Further, MTT assay and colony formation analysis showed that miR let-7a significantly inhibited cell proliferation of MCF-7 cells. However, overexpression of USP32 could reverse the effect of miR let-7a on MCF-7 cells proliferation.

Conclusions

Collectively, the results suggested that miR let-7a functions as a tumor suppressor to reduce proliferation by targeting USP32 in BCa cells.

HERC4 exerts an anti-tumor role through destabilizing the oncoprotein Smo

The GPCR-like transmembrane protein Smoothened (Smo) is an indispensable transducer in Hedgehog (Hh) pathway, its hyperactivation leads to several human cancers, including non-small cell lung cancer (NSCLC). The mechanism governing Smo stability still remains elusive. Here, we perform a modifier screening in Drosophila, and find that the E3 ligase dHerc4 degrades dSmo. Depletion of dherc4 increases dSmo protein and activates Hh pathway. In addition, we reveal that HERC4 is downregulated in NSCLC samples, negative correlating with Smo. HERC4 interacts with Smo reciprocally in NSCLC cells. Finally, we show that knockdown of herc4 activates Hh pathway and promotes NSCLC cell proliferation. Taken together, our studies have demonstrated that HERC4 acts as a tumor suppressor via destabilizing the oncoprotein Smo, and provided HERC4 as a promising therapeutic target for NSCLC treatment.