Functional roles of Speckle-Type Poz (SPOP) Protein in Genomic stability

State of Knowledge About Thyroid Cancers in the Era of COVID-19-A Narrative Review

Thyroid cancer (TC), due to its heterogeneous nature, remains a clinical challenge. Many factors can initiate the carcinogenesis process of various types of TC, which complicates diagnosis and treatment. The presented review gathers current information on specific types of TC, taking into account the effects of the COVID-19 pandemic. It is likely that COVID-19 has influenced and continues to influence the function of the thyroid gland. A high percentage of patients with COVID-19 showing simultaneous pathological changes in the thyroid suggests that SARS-CoV-2 may disrupt the function of this gland and initiate pro-oxidative mechanisms, inflammatory states, and autoimmune diseases, thereby promoting the formation of neoplastic changes. Furthermore, changes in the expression of the ACE2, TMPRSS2, CLEC4M and DPP4 genes, observed in TC, also occur in COVID-19. Therefore, it is probable that the interaction of SARS-CoV-2 with thyroid cell receptors may initiate carcinogenesis in this gland. Additionally, some drugs used in TC therapy (e.g., levothyroxine) may increase the affinity of SARS-CoV-2 for cells, which could contribute to a more severe course of COVID-19 and the emergence of long-term symptoms (post-COVID-19). Moreover, the consequences of sanitary restrictions (limited access to medical services, reduction in endocrinological and oncological procedures) that took place in many countries during the COVID-19 pandemic may lead in the future to an increased number of missed diagnoses and the emergence of aggressive cancers.

Prevalence of SPOP and IDH Gene Mutations in Prostate Cancer in a Jordanian Population

Speckle-type POZ (SPOP) is described as an essential tumor suppressor factor in gastric cancer, colorectal cancer, and prostate cancer (PCa). SPOP gene mutations were reported in primary human PCa. Isocitrate dehydrogenase-1 (IDH1) oncogene mutations were detected in gliomas, acute myeloid leukemia, some benign and malignant cartilaginous tumors, and only 1% of PCa. This study aimed to investigate the prevalence of mutations of SPOP and IDH1 genes in PCa in the Jordanian population. One hundred formalin-fixed paraffin-embedded tissue samples were collected from patients diagnosed with prostate adenocarcinoma. The obtained specimens were subjected to genomic DNA extraction, PCR amplification, and direct sequencing of exons 4, 5, 6, and 7 of the SPOP gene and exon 6 of the IDH1 gene. SPOP gene mutations were found in 17% of PCa cases, while no mutation was detected in the screened exon 6 of the IDH1 gene. Clinicopathological data demonstrated a strong correlation between prostate-specific antigen (PSA) levels and both Gleason score (GS) and the International Society of Urological Pathology (ISUP) grade group (GG). There was no significant correlation between PSA levels and age (p = 0.816) nor there were significant associations for SPOP mutational status with age (p = 0.659), PSA levels (p = 0.395), GS (p = 0.259), and ISUP GG (p = 0.424) in the tested population. The study found a strong correlation between PSA levels and both GS and ISUP GG. It also identified a high frequency (17%) of SPOP gene mutations in Jordanian Arab PCa patients, mainly in exon 7. No IDH1 mutations were detected in exon 6.

Deciphering the genetic and epigenetic architecture of prostate cancer

Prostate cancer, one of the most frequently diagnosed cancers in men, leads to significant mortality worldwide. Its study is important due to the complexity and diversity in its progression, highlighting the urgent need for improved therapeutic strategies. This chapter probes into the genetic and epigenetic factors influencing prostate cancer progression, underscoring the importance of understanding the disease's molecular fundamentals for the development of targeted therapies. It specifically reviews the role of key genetic mutations in genes such as Androgen Receptor, TP53, SPOP, FOXA1 and PTEN which are crucial for the disease onset and a progression. Furthermore, it examines the impact of epigenetic modifications, including DNA methylation and histone modification, which contribute to the cancer's progression by affecting gene expression and cellular behavior. Further, in this chapter we delve into the underlying signaling mechanism, the advancements in targeting genetic and epigenetic alterations in prostate cancer. These findings have revealed promising targets for therapeutic advancements, aiming to understand and identify promising avenues for future therapies. This chapter improves our current understanding of prostate cancer genetic and epigenetic landscape, emphasizing the necessity of advancing our knowledge to refine and expand treatment options for prostate cancer patients.

Chicken speckle-type POZ protein (SPOP) negatively regulates MyD88/NF-κB signaling pathway mediated proinflammatory cytokine production to promote the replication of Newcastle disease virus

The speckle-type POZ protein (SPOP) is demonstrated to be a specific adaptor of the cullin-RING-based E3 ubiquitin ligase complex that participates in multiple cellular processes. Up to now, SPOP involved in inflammatory response has attracted more attention, but the association of SPOP with animal virus infection is scarcely reported. In this study, chicken MyD88 (chMyD88), an innate immunity-associated protein, was screened to be an interacting partner of chSPOP using co-immunoprecipitation (Co-IP) combined with liquid chromatography-tandem mass spectrometry methods. This interaction was further confirmed by fluorescence co-localization, Co-IP, and pull-down assays. It was interesting that exogenous recombinant protein HA-chSPOP or endogenous chSPOP alone was mainly located in the nucleus but was translocated to the cytoplasm upon co-expression with chMyD88 or lipopolysaccharide stimulation. In addition, chSPOP reduced chMyD88 expression by ubiquitination in a dose-dependent manner, and the regulation of NF-κB activity by chSPOP was dependent solely on chMyD88. Importantly, chSPOP played a negative regulatory role in the MyD88/NF-κB signaling pathway and the production of proinflammatory cytokines. Moreover, we found that velogenic Newcastle disease virus (NDV) infection changed the subcellular localization of chSPOP and the expression patterns of chSPOP and chMyD88, and overexpression of chSPOP decreased the production of proinflammatory cytokines to enhance velogenic and lentogenic NDV replication, while siRNA-mediated chSPOP knockdown obtained the opposite results, thereby indicating that chSPOP negatively regulated MyD88/NF-κB signaling pathway mediated proinflammatory cytokine production to promote NDV replication. These findings highlight the important role of the SPOP/MyD88/NF-κB signaling pathway in NDV replication and may provide insightful information about NDV pathogenesis.

Synthesis and Biological Evaluation of β-Lactam Derivatives Targeting Speckle-Type POZ Protein (SPOP)

Speckle-type POZ protein (SPOP) acts as a cullin3-RING ubiquitin ligase adaptor, which facilitates the recognition and ubiquitination of substrate proteins. Previous research suggests that targeting SPOP holds promise in the treatment of clear cell renal cell carcinoma (ccRCC). On the basis of the reported SPOP inhibitor 230D7, a series of β-lactam derivatives were synthesized in this study. The biological activity assessment of these compounds revealed E1 as the most potent inhibitor, which can disrupt the SPOP-substrate interactions in vitro and suppress the colony formation of ccRCC cells. Taken together, this study provided compound E1 as a potent inhibitor against ccRCC and offered insight into the development of the β-lactam SPOP inhibitor.

Biophysical Characterization of the Binding Mechanism between the MATH Domain of SPOP and Its Physiological Partners

SPOP (Speckle-type POZ protein) is an E3 ubiquitin ligase adaptor protein that mediates the ubiquitination of several substrates. Furthermore, SPOP is responsible for the regulation of both degradable and nondegradable polyubiquitination of a number of substrates with diverse biological functions. The recognition of SPOP and its physiological partners is mediated by two protein-protein interaction domains. Among them, the MATH domain recognizes different substrates, and it is critical for orchestrating diverse cellular pathways, being mutated in several human diseases. Despite its importance, the mechanism by which the MATH domain recognizes its physiological partners has escaped a detailed experimental characterization. In this work, we present a characterization of the binding mechanism of the MATH domain of SPOP with three peptides mimicking the phosphatase Puc, the chromatin component MacroH2A, and the dual-specificity phosphatase PTEN. Furthermore, by taking advantage of site-directed mutagenesis, we address the role of some key residues of MATH in the binding process. Our findings are briefly discussed in the context of previously existing data on the MATH domain.

Clinical significance of SPOP and APC gene alterations in colorectal cancer in Indian population

Speckle-Type Poz Protein (SPOP) involved in the regulation of proteasome-mediated degradation of several oncoproteins, resulting in cancer initiation and progression. Mutations in Adenomatous Polyposis Coli (APC) gene is reported in most sporadic and hereditary colorectal cancer (CRC). Identifying the cellular changes involved in carcinogenesis when APC is mutated is an important issue that needs attention. The tumor suppressive function of SPOP and APC has long been a major focus in the research field of colorectal cancer. However, the clinical significance of SPOP and APC gene alteration in CRC has not been established to date. Mutational analysis was performed by single-strand conformational polymorphism followed by Sanger sequencing, methylation status by methylation-specific PCR, and protein expression by immunohistochemistry on 142 tumor tissues along with their adjacent non-cancerous specimens. The overall survival (OS) and recurrence free survival (RFS) were estimated by Kaplan-Meier Curve. Mutation rates of APC and SPOP gene were 2.8% and 11.9% while that of promoter hypermethylation were 37% and 47%, respectively. The grade of differentiation and Lymph node metastasis were significantly correlated with APC methylation pattern (p ≤ 0.05). The down regulation of APC was more often seen in colonic cancer compared to rectal cancer (p = 0.07) and more commonly in T3-4 depth of invasion (p = 0.07) and in patients without lymphovascular and perineural invasion (p = 0.007, p = 0.08 respectively). The median overall survival and recurrence free survival (RFS) was 67 & 36 months while 3-yr and 5-yr OS and RFS were 61.1% & 56.4% and 49.2% & 44.8%, respectively. APC promoter methylation had a better overall survival (p = 0.035) while loss of SPOP expression had a worse survival (p = 0.09). Our findings reveal high percentage of SPOP gene mutations in CRC. A significant link is found between promoter hyper methylation and protein expression in all mutant cases of APC and SPOP, suggesting that both genes may be associated in the development of colorectal cancer in people of Indian decent. Hypermethylation of APC gene and loss of SPOP expression have shown an association with disease prognosis and could be further studied looking at its potential role in planning adjuvant treatment in CRC patients.

SPOP in Cancer: Phenomena, Mechanisms and Its Role in Therapeutic Implications

Speckle-type POZ (pox virus and zinc finger protein) protein (SPOP) is a cullin 3-based E3 ubiquitin ligase adaptor protein that plays a crucial role in ubiquitin-mediated protein degradation. Recently, SPOP has attracted major research attention as it is frequently mutated in a range of cancers, highlighting pleiotropic tumorigenic effects and associations with treatment resistance. Structurally, SPOP contains a functionally critical N-terminal meprin and TRAF homology (MATH) domain for many SPOP substrates. SPOP has two other domains, including the internal Bric-a-brac-Tramtrack/Broad (BTB) domain, which is linked with SPOP dimerization and binding to cullin3, and a C-terminal nuclear localization sequence (NLS). The dysregulation of SPOP-mediated proteolysis is associated with the development and progression of different cancers since abnormalities in SPOP function dysregulate cellular signaling pathways by targeting oncoproteins or tumor suppressors in a tumor-specific manner. SPOP is also involved in genome stability through its role in the DNA damage response and DNA replication. More recently, studies have shown that the expression of SPOP can be modulated in various ways. In this review, we summarize the current understanding of SPOP's functions in cancer and discuss how to design a rational therapeutic target.

C-terminal truncated SPOP, a Janus-faced variant, causing a mixed type 1 and type 2 Nabais Sa-de Vries syndrome

Nabais Sa-de Vries syndrome (NSDVS) is an autosomal dominant neurodevelopmental disorder first described in 2020 and is classified into type 1 (NSDVS1) and type 2 (NSDVS2) which encompassed of spectrum of distinct clinical features due to gain-of-function (GOF) and loss-of-function (LOF) variants respectively. So far only 6 cases of 5 different missense pathogenic variants had been reported which impact on the SPOP substrate binding affinity for the downstream ubiquitylation. Here, we report a novel and de novo heterozygous nonsense pathogenic variant, p.Tyr353Term at the BACK domain in a patient with neurodevelopmental delay plus mixed phenotypes of NSDVS type 1 and 2 using trio exome analysis. The BACK domain is functionally critical for the SPOP higher-order oligomerization and is shown to increase substrate binding avidity with enhanced ubiquitylation efficiency in vitro. Experimentally, a missense variant p.Tyr353Glu is proven to attenuate the tandem SPOP oligomer formation and we envisage the current truncated variant at the same residue would attenuate the oligomerization process. This is the first report providing in vivo clue about the clinical significance of SPOP oligomerization in human neurodevelopmental disorders with new understanding on the expanding spectrum of NSDVS. We conclude the p.Tyr353Term is a Janus-faced variant which explains the dual NSDVS type 1 and 2 phenotypes in this case.

The speckle-type POZ protein (SPOP) inhibits breast cancer malignancy by destabilizing TWIST1

Epithelial-mesenchymal transition (EMT) inducing transcription factor TWIST1 plays a vital role in cancer metastasis. How the tumor-suppressive E3 ligase, speckle-type POZ protein (SPOP), regulates TWIST1 in breast cancer remains unknown. In this study, we report that SPOP physically interacts with, ubiquitinates, and destabilizes TWIST1. SPOP promotes K63-and K48-linked ubiquitination of TWIST1, predominantly at K73, thereby suppressing cancer cell migration and invasion. Silencing SPOP significantly enhances EMT, which accelerates breast cancer cell migration and invasiveness in vitro and lung metastasis in vivo. Clinically, SPOP is negatively correlated with the levels of TWIST1 in highly invasive breast carcinomas. Reduced SPOP expression, along with elevated TWIST1 levels, is associated with poor prognosis in advanced breast cancer patients, particularly those with metastatic triple-negative breast cancer (TNBC). Taken together, we have disclosed a new mechanism linking SPOP to TWIST1 degradation. Thus SPOP may serve as a prognostic marker and a potential therapeutic target for advanced TNBC patients.

HS3ST1 Promotes Non-Small-Cell Lung Cancer Progression by Targeting the SPOP/FADD/NF-κB Pathway

Heparan sulfate proteoglycan is a key component of cell microenvironment and plays an important role in cell-cell interaction, adhesion, migration, and signal transduction. Heparan sulfate 3-O-sulfotransferase 1 (HS3ST1) is a metabolic-related gene of HS. The present study was aimed at exploring the role of HS3ST1 in the progress of non-small-cell lung cancer (NSCLC). Our results illustrated that HS3ST1 promoted the malignant behaviors of NSCLC cells both in vitro and in vivo. HS3ST1 was found to inhibit spot-type zinc finger protein (SPOP) expression, which might inhibit the NF-κB pathway activation through mediating the degradation of Fas-associated death domain protein (FADD). By analyzing NSCLC patient samples, we also found increased HS3ST1 expression and decreased SPOP expression in tumor tissues in contrast with those in adjoining normal tissues. In conclusion, HS3ST1 promotes NSCLC tumorigenesis by regulating SPOP/FADD/NF-κB pathway.

SPOP Inhibition of Endometrial Carcinoma and Its Clinicopathological Relationship

Objective

Endometrial carcinoma (EC) ranks first in the incidence of female genital malignancies in developed countries. SPOP (speckle-type POZ protein) has changed in EC with a statistically high frequency. This research may play a crucial role in the initiation and progression of EC, ultimately leading to fresh therapeutic targets. Explore the expression of SPOP in EC; observe its effect on the proliferation, invasion, and migration of EC cells after upregulating the expression of SPOP through RNA activation.

Methods

The expression levels of SPOP protein in 150 EC tissues and 45 normal endometrial tissues were detected by immunohistochemistry and Western blotting. Analyze the relationship between SPOP expression and clinicopathological characteristics. The differences of the proliferation, migration, and invasion abilities between before and after transfection were analyzed using CCK-8 and Transwell assays.

Results

The results of immunohistochemistry and Western blotting showed the expression level of SPOP in EC tissue significantly reduced or even missed compared with normal endometrial tissue. The results of CCK-8 showed that the growth of EC significantly slowed down after the upregulating of SPOP expression. The results of the Transwell assay showed the migration and invasion abilities of EC cells were weakened after the level of SPOP was upregulated.

Conclusions

The expression level of SPOP in EC tissues is lower and related to the clinicopathological features compared with normal endometrial tissues. After upregulating the SPOP expression by RNA activation in EC cell lines, the abilities of proliferation, migration, and invasion of cells were significantly inhibited.

LZTR1: A promising adaptor of the CUL3 family

The study of the disorders of ubiquitin-mediated proteasomal degradation may unravel the molecular basis of human diseases, such as cancer (prostate cancer, lung cancer and liver cancer, etc.) and nervous system disease (Parkinson's disease, Alzheimer's disease and Huntington's disease, etc.) and help in the design of new therapeutic methods. Leucine zipper-like transcription regulator 1 (LZTR1) is an important substrate recognition subunit of cullin-RING E3 ligase that plays an important role in the regulation of cellular functions. Mutations in LZTR1 and dysregulation of associated downstream signaling pathways contribute to the pathogenesis of Noonan syndrome (NS), glioblastoma and chronic myeloid leukemia. Understanding the molecular mechanism of the normal function of LZTR1 is thus critical for its eventual therapeutic targeting. In the present review, the structure and function of LZTR1 are described. Moreover, recent advances in the current knowledge of the functions of LZTR1 in NS, glioblastoma (GBM), chronic myeloid leukemia (CML) and schwannomatosis and the influence of LZTR1 mutations are also discussed, providing insight into how LZTR1 may be targeted for therapeutic purposes.

Phosphorylation-dependent regulation of SPOP by LIMK2 promotes castration-resistant prostate cancer

BACKGROUND

SPOP, an E3 ubiquitin ligase adaptor, can act either as a tumour suppressor or a tumour promoter. In prostate cancer (PCa), it inhibits tumorigenesis by degrading several oncogenic substrates. SPOP is the most altered gene in PCa (~15%), which renders it ineffective, promoting cancer. The remaining PCa tumours, which retain WT-SPOP, still progress to castration-resistant (CRPC) stage, indicating that other critical mechanisms exist for downregulating SPOP. SPOP is reduced in ~94% of WT-SPOP-bearing prostate tumours; however, no molecular mechanism is known for its downregulation.

METHODS

SPOP was identified as a direct target of LIMK2 using an innovative technique. The reciprocal relationship between SPOP and LIMK2 and its consequences on oncogenicity were analysed using a variety of biochemical assays. To probe this relationship in vivo, xenograft studies were conducted.

RESULTS

LIMK2 degrades SPOP by direct phosphorylation at three sites. SPOP promotes LIMK2's ubiquitylation, creating a feedback loop. SPOP's degradation stabilises AR, ARv7 and c-Myc promoting oncogenicity. Phospho-resistant SPOP completely suppresses tumorigenesis in vivo, indicating that LIMK2-mediated SPOP degradation is a key event in PCa progression.

CONCLUSIONS

While genomically altered SPOP-bearing tumours require gene therapy, uncovering LIMK2-SPOP relationship provides a powerful opportunity to retain WT-SPOP by inhibiting LIMK2, thereby halting disease progression.

Stabilization of ERK-Phosphorylated METTL3 by USP5 Increases m6A Methylation

N⁶-methyladenosine (m⁶A) is the most abundant mRNA modification and is installed by the METTL3-METTL14-WTAP methyltransferase complex. Although the importance of m⁶A methylation in mRNA metabolism has been well documented recently, regulation of the m⁶A machinery remains obscure. Through a genome-wide CRISPR screen, we identify the ERK pathway and USP5 as positive regulators of the m⁶A deposition. We find that ERK phosphorylates METTL3 at S43/S50/S525 and WTAP at S306/S341, followed by deubiquitination by USP5, resulting in stabilization of the m⁶A methyltransferase complex. Lack of METTL3/WTAP phosphorylation reduces decay of m⁶A-labeled pluripotent factor transcripts and traps mouse embryonic stem cells in the pluripotent state. The same phosphorylation can also be found in ERK-activated human cancer cells and contribute to tumorigenesis. Our study reveals an unrecognized function of ERK in regulating m⁶A methylation.

Association of SPOP Mutations with Outcomes in Men with De Novo Metastatic Castration-sensitive Prostate Cancer

Recently, mutations in speckle-type pox virus and zinc finger protein (SPOP) gene (mutant SPOP [mtSPOP]) have been associated with improved outcomes to abiraterone in the castration-resistant setting. We hypothesized that mtSPOP would be associated with improved outcomes to systemic therapy in men with de novo metastatic castration-sensitive prostate cancer (d-mCSPC). Retrospective data of newly diagnosed d-mCSPC patients were collected from four institutions. Eligibility criteria included standard androgen deprivation therapy without intensification, and SPOP mutational status (mtSPOP or wild-type SPOP [wtSPOP]) determination by targeted next-generation sequencing from tumor biopsies. A total of 121 men (25 mtSPOP [21%] and 96 wtSPOP [79%]) were included. After adjusting for covariates, mtSPOP was significantly associated with better median progression-free survival (35 vs 13 mo; adjusted hazard ratio [HR] 0.47; p =  0.016) and overall survival (97 vs 69 mo; adjusted HR 0.32; p =  0.027), with similar HR and p value on the univariate analysis. These findings, upon external validation, may assist with counseling and prognostication in the clinic, and inform the design of future clinical trials in this setting. PATIENT SUMMARY: : Presence of tumor mutation in speckle-type pox virus and zinc finger protein (SPOP) gene was associated with improved survival outcomes in men with de novo metastatic castration-sensitive prostate cancer receiving standard androgen deprivation therapy.

Structure-Activity Relationship of SPOP Inhibitors against Kidney Cancer

Speckle-type POZ protein (SPOP) is overexpressed in the nucleus and misallocated in the cytoplasm in almost all the clear-cell renal cell carcinomas (ccRCCs), which leads to kidney tumorigenesis. Previously, we elucidated that the oncogenic SPOP-signaling pathway in ccRCC could be suppressed by 6b that inhibits SPOP-mediated protein interactions. Herein, we have established a structure-activity relationship for 6b analogues as SPOP inhibitors. Compound 6lc suppresses the viability and inhibits the colony formation of ccRCC cell lines driven by cytoplasmic SPOP, superior to 6b. Compound 6lc binds to the SPOP protein in vitro and disrupts SPOP binding to phosphatase-and-tensin homologue (PTEN) in HEK293T cells, which causes the observable phenomena: a decline in the ubiquitination of PTEN, elevated levels of both PTEN and dual-specificity phosphatase 7, and decreased levels of phosphorylated AKT and ERK when ccRCC cell lines are exposed to 6lc in a dose-response manner. Taken together, compound 6lc is a potent candidate against kidney tumorigenesis.

The diverse roles of SPOP in prostate cancer and kidney cancer

Multiple studies have confirmed that speckle-type pox virus and zinc finger (POZ) protein (SPOP) functions as a substrate adaptor of cullin 3-based E3 ligase and has a crucial role in various cellular processes via specific targeting of proteins for ubiquitination and subsequent proteasomal degradation. Dysregulation of SPOP-mediated proteolysis might be involved in the development and progression of human prostate and kidney cancers. In prostate cancer, SPOP seems to function as a tumour suppressor by targeting several proteins, including androgen receptor (AR), steroid receptor coactivator 3 (SRC3) and BRD4, for degradation, whereas it might function as an oncoprotein in kidney cancer, for example, by targeting phosphatase and tensin homologue (PTEN) for proteasomal degradation. In addition, nuclear SPOP targets AR for degradation and has a role as a tumour suppressor in prostate cancer; however, in kidney cancer, SPOP largely accumulates in the cytoplasm and fails to promote degradation of AR located in the nucleus, resulting in activation of AR-driven pathways and cancer progression. Owing to the context-dependent function of SPOP in human malignancies, further assessment of the molecular mechanisms involving SPOP in prostate and kidney cancers is needed to improve our understanding of its role in the development of these cancer types. Treatments that target SPOP might become therapeutic strategies in these malignancies in the future.

SPOP negatively regulates Toll-like receptor-induced inflammation by disrupting MyD88 self-association

Toll-like receptor (TLR) signaling pathways need to be tightly controlled to avoid excessive inflammation and unwanted damage to the host. Myeloid differentiation primary response gene 88 (MyD88) is a critical adaptor of TLR signaling. Here, we identified the speckle-type POZ protein (SPOP) as a MyD88-associated protein. SPOP was recruited to MyD88 following TLR4 activation. TLR4 activation also caused the translocation of SPOP from the nucleus to the cytoplasm. SPOP depletion promoted the aggregation of MyD88 and recruitment of the downstream signaling kinases IRAK4, IRAK1 and IRAK2. Consistently, overexpression of SPOP inhibited the TLR4-mediated activation of NF-κB and production of inflammatory cytokines, whereas SPOP depletion had the opposite effects. Furthermore, knockdown of SPOP increased MyD88 aggregation and inflammatory cytokine production upon TLR2, TLR7 and TLR9 activation. Our findings reveal a mechanism by which MyD88 is regulated and highlight a role for SPOP in limiting inflammatory responses.

The emerging role of SPOP protein in tumorigenesis and cancer therapy

The nuclear speckle-type pox virus and zinc finger (POZ) protein (SPOP), a representative substrate-recognition subunit of the cullin-RING E3 ligase, has been characterized to play a dual role in tumorigenesis and cancer progression. Numerous studies have determined that SPOP suppresses tumorigenesis in a variety of human malignancies such as prostate, lung, colon, gastric, and liver cancers. However, several studies revealed that SPOP exhibited oncogenic function in kidney cancer, suggesting that SPOP could exert its biological function in a cancer type-specific manner. The role of SPOP in thyroid, cervical, ovarian, bone and neurologic cancers has yet to be determined. In this review article, we describe the structure and regulation of SPOP in human cancer. Moreover, we highlight the critical role of SPOP in tumorigenesis based on three major categories: physiological evidence (animal models), pathological evidence (human cancer specimens) and biochemical evidence (downstream ubiquitin substrates). Furthermore, we note that SPOP could be a promising therapeutic target for cancer treatment.

The emerging role of SPOP protein in tumorigenesis and cancer therapy

The nuclear speckle-type pox virus and zinc finger (POZ) protein (SPOP), a representative substrate-recognition subunit of the cullin-RING E3 ligase, has been characterized to play a dual role in tumorigenesis and cancer progression. Numerous studies have determined that SPOP suppresses tumorigenesis in a variety of human malignancies such as prostate, lung, colon, gastric, and liver cancers. However, several studies revealed that SPOP exhibited oncogenic function in kidney cancer, suggesting that SPOP could exert its biological function in a cancer type-specific manner. The role of SPOP in thyroid, cervical, ovarian, bone and neurologic cancers has yet to be determined. In this review article, we describe the structure and regulation of SPOP in human cancer. Moreover, we highlight the critical role of SPOP in tumorigenesis based on three major categories: physiological evidence (animal models), pathological evidence (human cancer specimens) and biochemical evidence (downstream ubiquitin substrates). Furthermore, we note that SPOP could be a promising therapeutic target for cancer treatment.

SPOP Regulates The Biological Mechanism Of Ovarian Cancer Cells Through The Hh Signaling Pathway

Background

Ovarian cancer is characterized by high metastatic potential and high mortality. More than 80% of primary ovarian malignancies are epithelial ovarian cancers. There is increasing evidence that Speckle-type POZ protein (SPOP) is highly correlated with the development of various types of cancer. However, the effects of SPOP on epithelial ovarian cancer and the associated molecular mechanisms remain unclear.

Materials and methods

We compared SPOP expression between epithelial ovarian cancer tissues and normal ovarian tissues by using immunohistochemical staining. To determine the role of SPOP in epithelial ovarian cancer cells, we overexpressed or knocked down SPOP in the epithelial ovarian cancer cell line OVCAR-3 using lentiviral vectors.

Results

Our results from the present study indicated that SPOP expression was significantly downregulated in human epithelial ovarian cancer and was associated with the FIGO stage and the histopathologic grading of the tumor. The overexpression and knockdown experiments revealed that SPOP inhibited proliferation while promoting apoptosis in ovarian cancer cells. Inhibition of SPOP mis-activated the Hedgehog (Hh) signaling pathway, thereby inhibiting apoptosis in ovarian cancer cells.

Conclusion

SPOP suppresses proliferation and promotes apoptosis in human ovarian cancer cells by inhibiting the Hh signaling pathway, offering the possibility of new approaches for the treatment of ovarian cancer.

SPOP inhibits mice pancreatic stellate cell activation by promoting FADD degradation in cerulein-induced chronic pancreatitis

Pancreatic stellate cells (PSCs) have been recognized as key mediators of pancreatic fibrosis, a characteristic feature of chronic pancreatitis (CP). As a cullin-based E3 ubiquitin ligase, speckle-type POZ protein (SPOP) has been identified to participate in tumorigenesis and organ development. However, its biological role in CP remains unknown. Therefore, this study sought to investigate the changed expression of SPOP in CP and to examine the effect on mice PSCs activation of SPOP. We found that SPOP was downregulated in the pancreatic tissues of cerulein-induced CP mice. siRNA-mediated knockdown of SPOP led to significant promotion in primary PSCs activity by activating the nuclear factor-kappaB (NF-κB)/interleukin-6 (IL-6) signaling pathway. In addition, we examined the effects of Fas-associated death domain (FADD), a proven SPOP substrate that activates NF-κB, on the regulation of PSCs activation. We found that FADD was downregulated by SPOP via interaction-mediated degradation, and was upregulated during PSCs activation. The promotion of PSCs activation in knocking down SPOP with siSPOP-1 were counteracted by knocking down FADD. The results suggest that the SPOP-induced inhibition of PSCs activation partially depended on FADD. These results highlight the importance of SPOP in CP and provide a potential target for therapeutic intervention.