Targeting the deubiquitinase STAMBPL1 triggers apoptosis in prostate cancer cells by promoting XIAP degradation

STAMBPL1, transcriptionally regulated by SREBP1, promotes malignant behaviors of hepatocellular carcinoma cells via Wnt/β-catenin signaling pathway

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. STAM binding protein-like 1 (STAMBPL1), a key member of the COP9 signalosome subunit 5/serine protease 27/proteasome 26S subunit non-ATPase 7 (JAMM) family, is closely associated with tumor development. In this work, data from GSE101728 and GSE84402 chips were analyzed, and STAMBPL1 was selected as the target factor. This study aimed to reveal the potential function of STAMBPL1 in HCC. Clinical results showed that STAMBPL1 was significantly increased in tumor tissues of HCC patients, and its expression was strongly associated with tumor size and TNM stage. Furthermore, STAMBPL1-overexpressed Hep3B2.1-7 cell line or STAMBPL1-silenced SNU-182 cell line were established using lentivirus carrying cDNA encoding STAMBPL1 mRNA or shRNA targeting STAMBPL1, respectively. STAMBPL1-overexpressed cells exhibited a pronounced enhancement of proliferation in vitro and in vivo. Exogenous expression of STAMBPL1 increased the percentage of cells in the S phase and upregulated the expressions of CyclinD1 and Survivin. As expected, STAMBPL1 knockdown exhibited completely opposite effects, resulting in impaired tumorigenicity in vitro and in vivo. Mechanistically, STAMBPL1 activated Wnt/β-catenin pathway and increased the expression of downstream cancer-promoting genes. Interestingly, we found that STAMBPL1 was transcriptionally regulated by sterol regulatory element-binding protein 1 (SREBP1), a modulator of lipid metabolism, as evidenced by luciferase reporter and chromatin-immunoprecipitation (Ch-IP) assays. Notably, STAMBPL1 overexpression increased lipid accumulation in HCC cells and xenograft tumors. Totally our findings suggest that STAMBPL1 plays a vital role in the tumorigenicity of HCC cells. Modulation of Wnt/β-catenin and lipid metabolism may contribute to its pro-cancer effects. STAMBPL1 may serve as a therapeutic target of HCC.

Tubeimoside-1 Enhances TRAIL-Induced Apoptotic Cell Death through STAMBPL1-Mediated c-FLIP Downregulation

Tubeimoside-1 (TBMS-1), a traditional Chinese medicinal herb, is commonly used as an anti-cancer agent. In this study, we aimed to investigate its effect on the sensitization of cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Our results revealed that even though monotherapy using TBMS-1 or TRAIL at sublethal concentrations did not affect cancer cell death, combination therapy using TBMS-1 and TRAIL increased apoptotic cell death. Mechanistically, TBMS-1 destabilized c-FLIP expression by downregulating STAMBPL1, a deubiquitinase (DUB). Specifically, when STAMBPL1 and c-FLIP bound together, STAMBPL1 deubiquitylated c-FLIP. Moreover, STAMBPL1 knockdown markedly increased sensitivity to TRAIL by destabilizing c-FLIP. These findings were further confirmed in vivo using a xenograft model based on the observation that combined treatment with TBMS-1 and TRAIL decreased tumor volume and downregulated STAMBPL1 and c-FLIP expression levels. Overall, our study revealed that STAMBPL1 is essential for c-FLIP stabilization, and that STAMBPL1 depletion enhances TRAIL-mediated apoptosis via c-FLIP downregulation.

STAMBPL1 promotes the progression of lung adenocarcinoma by inhibiting DHRS2 expression

BACKGROUND

Lung cancer is responsible for the majority of cancer deaths in the world. We found a significant increase of STAMBPL1 expression in lung adenocarcinoma (LUAD) tissues and cells. However, its mechanism has not been clarified.

METHODS

LUAD tissues and adjacent normal tissues were collected from 62 patients treated in the First Affiliated Hospital of Wenzhou Medical University from August 2018 to August 2021. In vivo, the clinical data and STAMBPL1 expression of 62 patients with LUAD were analyzed by qPCR. In vitro, cell experiments were carried out after STAMBPL1 knockdown in A549 and H1299 cells to determine cell growth, migration rate, evasiveness, colony-forming ability, and apoptosis. Gene sequencing was used to explore the expression of various genes in A549 and H1299 cells to verify that DHRS2 was up-regulated after STAMBPL1 knockdown; cell experiments further detected the role of the DHRS2 gene after DHRS2 overexpression in A549 and H1299 cells. A rescue experiment was conducted to certify that STAMBPL1 promotes NSCLC progression by regulating DHRS2 expression.

RESULTS

After STAMBPL1 knockdown by siRNA. Migration, invasion, colony formation, and proliferation of siRNA groups were suppressed than those of NC groups in A549 and H1299 cells, while the cell apoptosis rate of siRNA groups increased significantly. By using gene-sequence analysis, we found that the expression level of the DHRS2 gene was up-regulated in STAMBPL1 siRNA groups, compared with STAMBPL1 NC (negative control) groups in A549 and H1299, which was verified by qPCR and WB. Further experiments showed that the DHRS2 OE group was suppressed in cell proliferation, migration, and invasion in the A549 and H1299 cell lines compared to the DHRS2 NC group, while DHRS2 OE group was significantly enhanced in the cell apoptosis in the A549 and H1299 cell lines. According to the rescue experiment, cell proliferation, migration, and invasion of the STAMBPL1 SI+DHRS2 SI group were enhanced compared with the STAMBPL1 SI+DHRS2 NC group in A549 and H1299 cells, while the STAMBPL1 SI+DHRS2 OE group were further decreased.

CONCLUSIONS

The expression of STAMBPL1 mRNA is significantly up-regulated in LUAD, promoting the progression of LUAD by down-regulating the expression of DHRS2 and acting as a potential biomarker of LUAD.

STAMBPL1 promotes breast cancer cell resistance to cisplatin partially by stabilizing MKP-1 expression

Dual-specificity mitogen-activated protein kinase phosphatase-1 (MKP-1/DUSP1/CL-100) has been documented to promote breast cancer cell survival and chemoresistance. MKP-1 is an unstable protein that is ubiquitinated and degraded via the ubiquitin-proteasome system. However, it is not clear how MKP-1 protein stability is regulated in breast cancer. In this study, we performed a genome-wide siRNA library screen of deubiquitinases (DUBs) and identified STAMBPL1 as an MKP-1 DUB in breast cancer cells. STAMBPL1 interacts with MKP-1 and stabilizes MKP-1 via deubiquitination. Both STAMBPL1 and MKP-1 depletion sensitize breast cancer cells to cisplatin in vitro and in vivo, and ectopic overexpression of MKP-1 partially rescues STAMBPL1 depletion-induced cisplatin sensitivity. Furthermore, STAMBPL1 and MKP-1 depletion increased breast cancer sensitivity to cisplatin by increasing the phosphorylation and activation of c-Jun N-terminal protein kinase (JNK). Collectively, our findings not only identify STAMBPL1 as an MKP-1 DUB but also reveal a critical mechanism that regulates MKP-1 expression in breast cancer. Our findings indicate that the STAMBPL1/MKP-1 axis represents a potential therapeutic target in breast cancer.

E3 ligase RNF167 and deubiquitinase STAMBPL1 modulate mTOR and cancer progression

The mTOR complex 1 (mTORC1) is an essential metabolic hub that coordinates cellular metabolism with the availability of nutrients, including amino acids. Sestrin2 has been identified as a cytosolic leucine sensor that transmits leucine status signals to mTORC1. In this study, we identify an E3 ubiquitin ligase RING finger protein 167 (RNF167) and a deubiquitinase STAMBPL1 that function in concert to control the polyubiquitination level of Sestrin2 in response to leucine availability. Ubiquitination of Sestrin2 promotes its interaction with GATOR2 and inhibits mTORC1 signaling. Bioinformatic analysis reveals decreased RNF167 expression and increased STAMBPL1 expression in gastric and colorectal tumors. Knockout of STAMBPL1 or correction of the heterozygous STAMBPL1 mutation in a human colon cancer cell line suppresses xenograft tumor growth. Lastly, a cell-permeable peptide that blocks the STAMBPL1-Sestrin2 interaction inhibits mTORC1 and provides a potential option for cancer therapy.

Helicobacter pylori-induced reactive oxygen species direct turnover of CSN-associated STAMBPL1 and augment apoptotic cell death

Deubiquitinylases (DUBs) are central regulators of the ubiquitin system involved in protein regulation and cell signalling and are important for a variety of physiological processes. Most DUBs are cysteine proteases, and few other proteases are metalloproteases of the JAB1/MPN +/MOV34 protease family (JAMM). STAM-binding protein like 1 (STAMBPL1), a member of the JAMM family, cleaves ubiquitin bonds and has a function in regulating cell survival, Tax-mediated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation and epithelial-mesenchymal transition. However, the molecular mechanism by which STAMBPL1 influences cell survival is not well defined, especially with regard to its deubiquitinylation function. Here, we show that reactive oxygen species (ROS) induced by chemotherapeutic agents or the human microbial pathogen Helicobacter pylori can induce cullin 1-RING ubiquitin ligase (CRL1) and 26S proteasome-dependent degradation STAMBPL1. Interestingly, STAMBPL1 has a direct interaction with the constitutive photomorphogenic 9 (COP9 or CSN) signalosome subunits CSN5 and CSN6. The interaction with the CSN is required for the stabilisation and function of the STAMBPL1 protein. In addition, STAMBPL1 deubiquitinylates the anti-apoptotic protein Survivin and thus ameliorates cell survival. In summary, our data reveal a previously unknown mechanism by which the deubiquitinylase STAMBPL1 and the E3 ligase CRL1 balance the level of Survivin degradation and thereby determine apoptotic cell death. In response to genotoxic stress, the degradation of STAMBPL1 augments apoptotic cell death. This new mechanism may be useful to develop therapeutic strategies targeting STAMBPL1 in tumours that have high STAMBPL1 and Survivin protein levels.

Selection for or against escape from nonsense mediated decay is a novel signature for the detection of cancer genes

Escape from nonsense mediated mRNA decay (NMD-) can produce activated or inactivated gene products, and bias in rates of escape can identify functionally important genes in germline disease. We hypothesized that the same would be true of cancer genes, and tested for NMD- bias within The Cancer Genome Atlas pan-cancer somatic mutation dataset. We identify 29 genes that show significantly elevated or suppressed rates of NMD-. This novel approach to cancer gene discovery reveals genes not previously cataloged as potentially tumorigenic, and identifies many potential driver mutations in known cancer genes for functional characterization.

The deubiquitinase USP16 functions as an oncogenic factor in K-RAS-driven lung tumorigenesis

K-RAS mutation and molecular alterations of its surrogates function essentially in lung tumorigenesis and malignant progression. However, it remains elusive how tumor-promoting and deleterious events downstream of K-RAS signaling are coordinated in lung tumorigenesis. Here, we show that USP16, a deubiquitinase involved in various biological processes, functions as a promoter for the development of K-RAS-driven lung tumor. Usp16 deletion significantly attenuates K-rasG12D-mutation-induced lung tumorigenesis in mice. USP16 upregulation upon RAS activation averts reactive oxygen species (ROS)-induced p38 activation that would otherwise detrimentally influence the survival and proliferation of tumor cells. In addition, USP16 interacts with and deubiquitinates JAK1, and thereby promoting lung tumor growth by augmenting JAK1 signaling. Therefore, our results reveal that USP16 functions critically in the K-RAS-driven lung tumorigenesis through modulating the strength of p38 and JAK1 signaling.

Deubiquitinases: Modulators of Different Types of Regulated Cell Death

The mechanisms and physiological implications of regulated cell death (RCD) have been extensively studied. Among the regulatory mechanisms of RCD, ubiquitination and deubiquitination enable post-translational regulation of signaling by modulating substrate degradation and signal transduction. Deubiquitinases (DUBs) are involved in diverse molecular pathways of RCD. Some DUBs modulate multiple modalities of RCD by regulating various substrates and are powerful regulators of cell fate. However, the therapeutic targeting of DUB is limited, as the physiological consequences of modulating DUBs cannot be predicted. In this review, the mechanisms of DUBs that regulate multiple types of RCD are summarized. This comprehensive summary aims to improve our understanding of the complex DUB/RCD regulatory axis comprising various molecular mechanisms for diverse physiological processes. Additionally, this review will enable the understanding of the advantages of therapeutic targeting of DUBs and developing strategies to overcome the side effects associated with the therapeutic applications of DUB modulators.

Systematic analysis reveals a functional role for STAMBPL1 in the epithelial-mesenchymal transition process across multiple carcinomas

Background

Deubiquitinating enzymes (DUBs) are linked to cancer progression and dissemination, yet less is known about their regulation and impact on epithelial–mesenchymal transition (EMT).

Methods

An integrative translational approach combining systematic computational analyses of The Cancer Genome Atlas cancer cohorts with CRISPR genetics, biochemistry and immunohistochemistry methodologies to identify and assess the role of human DUBs in EMT.

Results

We identify a previously undiscovered biological function of STAM-binding protein like 1 (STAMBPL1) deubiquitinase in the EMT process in lung and breast carcinomas. We show that STAMBPL1 expression can be regulated by mutant p53 and that its catalytic activity is required to affect the transcription factor SNAI1. Accordingly, genetic depletion and CRISPR-mediated gene knockout of STAMBPL1 leads to marked recovery of epithelial markers, SNAI1 destabilisation and impaired migratory capacity of cancer cells. Reversely, STAMBPL1 expression reprogrammes cells towards a mesenchymal phenotype. A significant STAMBPL1-SNAI1 co-signature was observed across multiple tumour types. Importantly, STAMBPL1 is highly expressed in metastatic tissues compared to matched primary tumour of the same lung cancer patient and its expression predicts poor prognosis.

Conclusions

Our study provides a novel concept of oncogenic regulation of a DUB and presents a new role and predictive value of STAMBPL1 in the EMT process across multiple carcinomas.

Honokiol Enhances TRAIL-Mediated Apoptosis through STAMBPL1-Induced Survivin and c-FLIP Degradation

Honokiol is a natural biphenolic compound extracted from traditional Chinese medicine Magnolia species, which have been known to display various biological effects including anti-cancer, anti-proliferative, anti-angiogenic, and anti-metastatic activities in cancer cells. Here, we found that honokiol sensitizes cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis through downregulation of anti-apoptotic proteins survivin and c-FLIP. Ectopic expression of survivin and c-FLIP markedly abolished honokiol and TRAIL-induced apoptosis. Mechanistically, honokiol induced protein degradation of c-FLIP and survivin through STAMBPL1, a deubiquitinase. STAMBPL1 interacted with survivin and c-FLIP, resulted in reduction of ubiquitination. Knockdown of STAMBPL1 reduced survivin and c-FLIP protein levels, while overexpression of STAMBPL1 inhibited honokinol-induced survivin and c-FLIP degradation. Our findings provided that honokiol could overcome TRAIL resistance through survivin and c-FLIP degradation induced by inhibition of STAMBPL1 expression.