Ubiquitination modulates a large repertoire of cellular functions and thus, dysregulation of the ubiquitin system results in multiple human diseases, including cancer. Ubiquitination requires an E3 ...ligase, which is responsible for substrate recognition and conferring specificity to ubiquitination. HUWE1 is a multifaceted HECT domain-containing ubiquitin E3 ligase, which catalyzes both mono-ubiquitination and K6-, K48- and K63-linked poly-ubiquitination of its substrates. Many of the substrates of HUWE1 play a crucial role in maintaining the homeostasis of cellular development. Not surprisingly, dysregulation of HUWE1 is associated with tumorigenesis and metastasis. HUWE1 is frequently overexpressed in solid tumors, but can be downregulated in brain tumors, suggesting that HUWE1 may possess differing cell-specific functions depending on the downstream targets of HUWE1. This review introduces some important discoveries of the HUWE1 substrates, including those controlling proliferation and differentiation, apoptosis, DNA repair, and responses to stress. In addition, we review the signaling pathways HUWE1 participates in and obstacles to the identification of HUWE1 substrates. We also discuss up-to-date potential therapeutic designs using small molecules or ubiquitin variants (UbV) against the HUWE1 activity. These molecular advances provide a translational platform for future bench-to-bed studies. HUWE1 is a critical ubiquitination modulator during the tumor progression and may serve as a possible therapeutic target for cancer treatment.
Markers of cancer stemness predispose patients to tumor aggressiveness, drug and immunotherapy resistance, relapse, and metastasis. DDX17 is a cofactor of the Drosha-DGCR8 complex in miRNA biogenesis ...and transcriptional coactivator and has been associated with cancer stem-like properties. However, the precise mechanism by which DDX17 controls cancer stem-like features remains elusive. Here, we show that the E3 ligase HectH9 mediated K63-polyubiquitination of DDX17 under hypoxia to control stem-like properties and tumor-initiating capabilities. Polyubiquitinated DDX17 disassociated from the Drosha-DGCR8 complex, leading to decreased biogenesis of anti-stemness miRNAs. Increased association of polyubiquitinated DDX17 with p300-YAP resulted in histone 3 lysine 56 (H3K56) acetylation proximal to stemness-related genes and their subsequent transcriptional activation. High expression of HectH9 and six stemness-related genes (
, and
) predicted poor survival in patients with head and neck squamous cell carcinoma and lung adenocarcinoma. Our findings demonstrate that concerted regulation of miRNA biogenesis and histone modifications through posttranslational modification of DDX17 underlies many cancer stem-like features. Inhibition of DDX17 ubiquitination may serve as a new therapeutic venue for cancer treatment. SIGNIFICANCE: Hypoxia-induced polyubiquitination of DDX17 controls its dissociation from the pri-miRNA-Drosha-DCGR8 complex to reduce anti-stemness miRNA biogenesis and association with YAP and p300 to enhance transcription of stemness-related genes.
Intratumoural hypoxia induces HIF-1α and promotes tumour progression, metastasis and treatment resistance. HIF-1α stability is regulated by VHL-E3 ligase-mediated ubiquitin-dependent degradation; ...however, the hypoxia-regulated deubiquitinase that stabilizes HIF-1α has not been identified. Here we report that HAUSP (USP7) deubiquitinase deubiquitinates HIF-1α to increase its stability, induce epithelial-mesenchymal transition and promote metastasis. Hypoxia induces K63-linked polyubiquitinated HAUSP at lysine 443 to enhance its functions. Knockdown of HAUSP decreases acetylation of histone 3 lysine 56 (H3K56Ac). K63-polyubiquitinated HAUSP interacts with a ubiquitin receptor CBP to specifically mediate H3K56 acetylation. ChIP-seq analysis of HAUSP and HIF-1α binding reveals two motifs responsive to hypoxia. HectH9 is the E3 ligase for HAUSP and a prognostic marker together with HIF-1α. This report demonstrates that hypoxia-induced K63-polyubiquitinated HAUSP deubiquitinates HIF-1α and causes CBP-mediated H3K56 acetylation on HIF-1α target gene promoters to promote EMT/metastasis, further defining HAUSP as a therapeutic target in hypoxia-induced tumour progression.
Purpose
Metastasis is the end stage of renal cell carcinoma (RCC), and clear cell renal cell carcinoma (ccRCC) is the most common malignant subtype. The hypoxic microenvironment is a common feature ...in ccRCC and plays an essential role in the regulation of epithelial–mesenchymal transition (EMT). Accumulating evidence manifests that long non‐coding RNAs (lncRNAs) participate in RCC tumorigenesis and regulate hypoxia‐induced EMT. Here, we identified a lncRNA RP11‐367G18.1 induced by hypoxia, that was overexpressed in ccRCC tissues.
Methods
A total of 216 specimens, including 149 ccRCC tumor samples and 67 related normal kidney parenchyma tissue samples, were collected. To investigate the biological fucntions of RP11.367G18.1 in ccRCC, migration, invasion, soft agar colony formation, xenograft tumorigenicity assays, and tail vein and orthotopic metastatic mouse models were performed. The relationship between RP11‐367G18.1 and downstream signaling was analyzed utilizing reporter assay, RNA pull‐down, chromatin immunopreciptation, and chromatin isolation by RNA purification assays.
Results
Hypoxic conditions and overexpression of HIF‐1α increased the level of RP11‐367G18.1. RP11‐367G18.1 induced EMT and enhanced cell migration and invasion through variant 2. Inhibition of RP11‐367G18.1 variant 2 reversed hypoxia‐induced EMT phenotypes. An in vivo study revealed that RP11‐367G18.1 variant 2 was required for hypoxia‐induced tumor growth and metastasis in ccRCC. Mechanistically, RP11‐367G18.1 variant 2 interacted with p300 histone acetyltransferase to regulate lysine 16 acetylation on histone 4 (H4K16Ac), thus contributing to hypoxia‐regulated gene expression. Clinically, RP11‐367G18.1 variant 2 was upregulated in ccRCC tissues, particularly metastatic ccRCC tissues, and it is linked to poor overall survival.
Conclusion
These findings demonstrate the prognostic value and EMT‐promoting role of RP11‐367G18.1 and indicate that this lncRNA may provide a therapeutic target for ccRCC.
Hypoxia upregulated lncRNA RP11‐367G18.1 variant 2 which was associated with p300‐mediated chromatin modifying complex to activate H4K16Ac marks. RP11‐367G18.1 variant 2 increased the levels of H4K16Ac on the promoter of hypoxia‐regulated genes leading to EMT and tumor metastasis.
Triple-negative breast cancer (TNBC) represents up to 20% of all breast cancers. This cancer lacks the expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor ...receptor 2. The current therapeutic strategy for patients with this subtype is the use of cytotoxic chemotherapy and surgery. Luteolin is a natural herbal flavonoid and a potential therapeutic candidate for multiple diseases. The use of a treatment that combines Chinese herbal medicine and western medicine is rising in Asia.
The present study evaluates the effects and molecular mechanisms involved with luteolin treatment and evaluates whether this herb affects androgen receptor-positive breast cancer cell proliferation or metastasis.
In vitro evaluation of the effect of luteolin on androgen receptor-positive TNBC cell proliferation and metastasis
Cell viability analysis was used for the cytotoxicity test. Colony formation and Bromodeoxyuridine (BrdU) staining-based proliferation experiments were used for cell proliferation. Wound healing and transwell assays were used for in vitro migration/invasion. The RT-qPCR analysis was used for gene expression. Furthermore, ChIP-qPCR analysis was used for epigenetic modification of gene promoters.
Luteolin significantly inhibited the proliferation and metastasis of androgen receptor-positive TNBC. Furthermore, luteolin inactivated the AKT/mTOR signaling pathway and reversed the epithelial-mesenchymal transition (EMT). The combination of luteolin and inhibitors of AKT/mTOR synergistically repressed an androgen receptor-positive TNBC cell proliferation and metastasis. Luteolin also downregulated MMP9 expression by decreasing the levels of the AKT/mTOR promoting H3K27Ac and H3K56A on the MMP9 promoter region.
Our findings indicate that luteolin inhibited the proliferation and metastasis of androgen receptor-positive TNBC by regulating MMP9 expression through a reduction in the levels of AKT/mTOR-inducing H3K27Ac and H3K56Ac.
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Abstract
Background
The hypoxia-responsive long non-coding RNA,
RP11-367G18.1
, has recently been reported to induce histone 4 lysine 16 acetylation (H4K16Ac) through its variant 2; however, the ...underlying molecular mechanism remains poorly understood.
Methods
RNA pull-down assay and liquid chromatography-tandem mass spectrometry were performed to identify
RP11-367G18.1
variant 2-binding partner. The molecular events were examined utilizing western blot analysis, real-time PCR, luciferase reporter assay, chromatin immunoprecipitation, and chromatin isolation by RNA purification assays. The migration, invasion, soft agar colony formation, and in vivo xenograft experiments were conducted to evaluate the impact of
RP11-367G18.1
variant 2–YY1 complex on tumor progression.
Results
In this study, RNA sequencing data revealed that hypoxia and
RP11-367G18.1
variant 2 co-regulated genes were enriched in tumor-related pathways. YY1 was identified as an
RP11-367G18.1
variant 2-binding partner that activates the H4K16Ac mark. YY1 was upregulated under hypoxic conditions and served as a target gene for hypoxia-inducible factor-1α.
RP11-367G18.1
variant 2 colocalized with YY1 and H4K16Ac in the nucleus under hypoxic conditions. Head and neck cancer tissues had higher levels of
RP11-367G18.1
and YY1 which were associated with poor patient outcomes.
RP11-367G18.1
variant 2–YY1 complex contributes to hypoxia-induced epithelial–mesenchymal transition, cell migration, invasion, and tumorigenicity. YY1 regulated hypoxia-induced genes dependent on
RP11-367G18.1
variant 2.
Conclusions
RP11-367G18.1
variant 2–YY1 complex mediates the tumor-promoting effects of hypoxia, suggesting that this complex can be targeted as a novel therapeutic strategy for cancer treatment.
Triple-negative breast cancer (TNBC) accounts for 15–20% of all breast cancer. TNBC does not express the estrogen receptor, progesterone receptor, or human epidermal growth factor receptor 2. ...Cytotoxic chemotherapy and surgery are the current therapeutic strategies for TNBC patients, but the chemoresistance of TNBC limits the efficiency of this strategy and shortens the lifespan of patients. The exploration of targeted therapy is ongoing in TNBC research. The aim of the present study was to identify the mechanism underlying acquired resistance in TNBC through the exploration of the relationship between the expression of USP7 and of ABCB1. We found that ubiquitin specific protease 7 (USP7) is a potential therapeutic target for overcoming the chemoresistance of TNBC. USP7 overexpression increased the chemoresistance of TNBC, while the knockdown of USP7 effectively increased the chemosensitivity of chemoresistant TNBC. A USP7 inhibitor effectively induced apoptosis and suppressed metastasis in chemoresistant TNBC. We further clarified that USP7 is a specific deubiquitinating enzyme for ABCB1 that plays an essential role in drug resistance. USP7 directly interacted with ABCB1 and regulated its stability. We concluded that USP7 promotes the chemoresistance of TNBC by stabilizing the ABCB1 protein.
•Nafamostat mesylate (NM) causes apoptosis and suppresses metastasis of endocrine-resistant ER-positive breast cancer (ERPBC).•Epigenetic downregulation of CDK4/CDK6 by NM in endocrine-resistant ...ERPBC via disruption of binding of H3K27Ac on promoter region.•Combination of nafamostat mesylate and CDK4/6 inhibitor synergistically overcomes endocrine resistance of breast cancer.•Nafamostat mesylate would be a well-efficient drug for endocrine-resistant ERPBC.
Breast cancer is common worldwide, and the estrogen receptor-positive subtype accounts for approximately 70% of breast cancer in women. Tamoxifen and fulvestrant are drugs currently used for endocrinal therapy. Breast cancer exhibiting endocrine resistance can undergo metastasis and lead to the death of breast cancer patients. Drug repurposing is an active area of research in clinical medicine. We found that nafamostat mesylate, clinically used for patients with pancreatitis and disseminated intravascular coagulation, acts as an anti-cancer drug for endocrine-resistant estrogen receptor-positive breast cancer (ERPBC). Epigenetic repression of CDK4 and CDK6 by nafamostat mesylate induced apoptosis and suppressed the metastasis of ERPBC through the deacetylation of Histone 3 Lysine 27. A combination of nafamostat mesylate and CDK4/6 inhibitor synergistically overcame endocrine resistance in ERPBC. Nafamostat mesylate might be an essential adjuvant or alternative drug for the treatment of endocrine-resistant ERPBC due to the low cost-efficiency of the CDK4/6 inhibitor.
K63-linked polyubiquitination of proteins have nonproteolytic functions and regulate the activity of many signal transduction pathways. USP7, a HIF1α deubiquitinase, undergoes K63-linked ...polyubiquitination under hypoxia. K63-polyubiquitinated USP7 serves as a scaffold to anchor HIF1α, CREBBP, the mediator complex, and the super elongation complex to enhance HIF1α-induced gene transcription. However, the physiological role of K63-polyubiquitinated USP7 remains unknown.
Using a Usp7K444R point mutation knock-in mouse strain, we performed immunohistochemistry and standard molecular biological methods to examine the organ defects of liver and kidney in this knock-in mouse strain. Mechanistic studies were performed by using deubiquitination, immunoprecipitation, and quantitative immunoprecipitations (qChIP) assays.
We observed multiple organ defects, including decreased liver and muscle weight, decreased tibia/fibula length, liver glycogen storage defect, and polycystic kidneys. The underlying mechanisms include the regulation of protein stability and/or modulation of transcriptional activation of several key factors, leading to decreased protein levels of Prr5l, Hnf4α, Cebpα, and Hnf1β. Repression of these crucial factors leads to the organ defects described above.
K63-polyubiquitinated Usp7 plays an essential role in the development of multiple organs and illustrates the importance of the process of K63-linked polyubiquitination in regulating critical protein functions.
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