Decoding the Expressions, Immune Relevance, and Prognostic Values of Ferroptosis Gene TMEM189: A Pan-Cancer Analysis.

BACKGROUND: TMEM189 is a recently discovered transmembrane protein involved in ether glycerophospholipid synthesis and ferroptosis regulation. However, its role in tumors are not well understood. OBJECTIVE: To elucidate the oncogenic effects and prognostic values of TMEM189 in tumors. METHODS: We performed a pan-cancer analysis of TMEM189 using various databases, bioinformatics and statistical tools, and tissue microarray analysis. RESULTS: TMEM189 is generally upregulated in tumors compared to normal tissues. High TMEM189 expression is linked to reduced promoter methylation. TMEM189 exhibits a negative correlation with immunogenic markers, immune cell infiltration, and expression of immune checkpoint genes (ICGs) in most cancers, implicating its immunosuppressive role in tumor microenvironments (TME). The interacting and similar genes with TMEM189 were involved in hotspot signaling pathways in pan-cancer. TMEM189 overexpression is usually associated with poor prognosis, especially an independent prognostic risk factor for BLCA, BRCA, LUAD, MESO, LIHC and SKCM. CONCLUSION: TMEM189 is overexpressed and exerts immunosuppressive effects in many tumors with a significant association with poor prognosis, suggesting its potential as a therapeutic target in cancer treatment.

P4HA2 Promotes Epithelial-to-Mesenchymal Transition and Glioma Malignancy through the Collagen-Dependent PI3K/AKT Pathway.

Prolyl-4-hydroxylase subunit 2 (P4HA2) is a member of collagen modification enzymes involved in the remodeling of the extracellular matrix (ECM). Mounting evidence has suggested that deregulation of P4HA2 is common in cancer. However, the role of P4HA2 in glioma remains unknown. The present study aimed to elucidate the expression pattern, oncogenic functions, and molecular mechanisms of P4HA2 in glioblastoma cells. The TCGA datasets and paraffin samples were used for examining the expressions of P4HA2. P4HA2-specific lentivirus was generated to assess its oncogenic functions. A P4HA2 enzyme inhibitor (DHB) and an AKT agonist (SC79) were utilized to study the mechanisms. As a result, we demonstrated that P4HA2 is overexpressed in glioma and inversely correlates with patient survival. Knockdown of P4HA2 inhibited proliferation, migration, invasion, and epithelial-to-mesenchymal transition (EMT) like phenotype of glioma cells in vitro and suppressed tumor xenograft growth in vivo. Mechanistically, expressions of a series of collagen genes and of phosphorylated PI3K/AKT were downregulated by either P4HA2 silencing or inhibition of its prolyl hydroxylase. Finally, the inhibitory effects on the migration, invasion, and EMT-related molecules by P4HA2 knockdown were reversed by AKT activation with SC79. Our findings for the first time reveal that P4HA2 acts as an oncogenic molecule in glioma malignancy by regulating the expressions of collagens and the downstream PI3K/AKT signaling pathway.

Hypoxia-induced USP22-BMI1 axis promotes the stemness and malignancy of glioma stem cells via regulation of HIF-1α.

AIMS: This study intends to investigate the mechanisms of ubiqutin-specific protease 22 (USP22)/B cell-specific Moloney murine leukemia virus integration site 1 (BMI1) on the biological phenotypes of glioma stem cells (GSCs) under hypoxia. MAIN METHODS: Western blot, Cell Counting Kit-8, colony formation and flow cytometry assays were preformed to evaluate cells biological behaviors. Luciferase assay was utilized to identify the associations among USP22, HIF-1α and BMI1. KEY FINDINGS: Silencing USP22 reduced the stemness and proliferation of GSCs, and increased its apoptosis in response to hypoxia. Whilst, overexpression of BMI1 reversed these phenomena. Whilst, a significant decrease in proliferation and stemness of GSCs caused by HIF-1α exhaustion were inversed by overexpression of USP22 or BMI1. SIGNIFICANCE: Function of USP22-BMI1 on biological behaviors of GSCs was regulated by HIF-1α in response to hypoxia.

Ubiquitin-specific protease 22 acts as an oncoprotein to maintain glioma malignancy through deubiquitinating B cell-specific Moloney murine leukemia virus integration site 1 for stabilization.

Ubiquitin-specific protease 22 (USP22) is a member of the "death-from-cancer" signature, which plays a key role in cancer progression. Previous evidence has shown that USP22 is overexpressed and correlates with poor prognosis in glioma. The effect and mechanism of USP22 in glioma malignancy, especially cancer stemness, remain elusive. Herein, we find USP22 is more enriched in stem-like tumorspheres than differentiated glioma cells. USP22 knockdown inhibits cancer stemness in glioma cell lines. With a cell-penetrating TAT-tag protein, B cell-specific Moloney murine leukemia virus integration site 1 (BMI1), a robust glioma stem-cell marker, is found to mediate the effect of USP22 on glioma stemness. By immunofluorescence, USP22 and BMI1 are found to share similar intranuclear expression in glioma cells. By analysis with immunohistochemistry and bioinformatics, USP22 is found to positively correlate with BMI1 at the post-translational level only rather than at the transcriptional level. By immunoprecipitation and in vivo deubiquitination assay, USP22 is found to interact with and deubiquitinate BMI1 for protein stabilization. Microarray analysis shows that USP22 and BMI1 mutually regulate a series of genes involved in glioma stemness such as POSTN, HEY2, PDGFRA and ATF3. In vivo study with nude mice confirms the role of USP22 in promoting glioma tumorigenesis by regulating BMI1. All these findings indicate USP22 as a novel deubiquitinase of BMI1 in glioma. We propose a working model of the USP22-BMI1 axis, which promotes glioma stemness and tumorigenesis through oncogenic activation. Thus, targeting USP22 might be an effective strategy to treat glioma especially in those with elevated BMI1 expression.

Characterizing the molecular mechanisms of acquired temozolomide resistance in the U251 glioblastoma cell line by protein microarray.

Acquired chemoresistance refers to tumor cells gradually losing their sensitivity to anticancer drugs during the course of treatment, resulting in tumor progression or recurrence. This phenomenon, which has deleterious outcomes for the patient, has long been observed in patients with glioblastoma receiving temozolomide (TMZ)-based radiochemotherapy. Currently, the mechanisms for acquired TMZ chemoresistance are not fully understood. In the present study, a TMZ-resistant cell line U251R with a 4-fold 50% inhibition concentration compared with its TMZ-sensitive parent cell line was isolated by incremental long-time TMZ treatment in the human glioblastoma cell line U251. Fluorescence-activated cell sorting analysis indicated G2/M arrest and a lower proportion of cells in the S phase, accompanied by a decreased apoptosis rate in the U251R cell line compared with the parental U251 cell line. In addition, a sphere-formation assay indicated an increased self-renewal capacity in U251R cells. Furthermore, a high-throughput protein microarray unveiled more than 200 differentially expressed proteins as potential molecular targets accounting for acquired TMZ resistance. Subsequent bioinformatics analysis illustrated the molecular and signaling networks and revealed the central role of SRC. Immunoblotting and reverse-transcription quantitative polymerase chain reaction analysis further confirmed the expressional upregulation of SRC family kinases. Moreover, SRC knockdown led to partial reversal of TMZ resistance in the U251R cell line and sensitization in the U373 cell line. These data helped to develop a comprehensive understanding of survival strategies, particularly with respect to pro-stemness regulation, which could be potential targets for overcoming TMZ resistance.

FBW7 is associated with prognosis, inhibits malignancies and enhances temozolomide sensitivity in glioblastoma cells.

F-box and WD repeat domain-containing 7 (FBW7) is a SCF-type E3 ubiquitin ligase targeting a multitude of oncoproteins for degradation. Acting as one of the most important tumor suppressors, it is frequently inactivated in various tumors. In this study we aimed to evaluate the relationship of FBW7 with glioma pathology and prognosis, and examine its effect in glioma malignancies and temozolomide (TMZ)-based therapy. Clinical tissues and TCGA database analysis revealed that FBW7 expression was correlated inversely with glioma histology and positively with patient survival time. Lentivirus transfection-induced FBW7 overexpression significantly suppressed proliferation, invasion and migration of U251 and U373 cells, whereas knockdown of FBW7 by targeted shRNA promoted proliferation, invasion and migration of glioma cells. Most importantly, the expression level of FBW7 was found to affect the 50% inhibitory concentration (IC50) of U251 and the TMZ-resistant variant. Combining TMZ with FBW7 overexpression notably increased the cytotoxicity compared to TMZ treatment alone, which was conversely attenuated by FBW7 knockdown. Moreover, flow cytometry (FC) analysis showed overexpression of FBW7, TMZ or the combination-increased proportion of G2/M arrest and the apoptotic rate, whereas FBW7 inhibition reduced G2/M arrest and apoptosis in U251 cells. Finally, mechanistic study found that FBW7 overexpression downregulated Aurora B, Mcl1 and Notch1 levels in a time-dependent pattern and this expressional suppression was independent of TMZ. These findings collectively demonstrate the critical role of FBW7 as a prognostic factor and a potential target to overcome chemoresistance of glioblastoma.

Organoids: An intermediate modeling platform in precision oncology.

Cancer harbors variable heterogeneity and plasticity. Thus far, our comprehension is greatly based on cell lines, organoids, and patient-derived tumor xenografts (PDTXs). Organoids are a three-dimensional in vitro culture platform constructed from self-organizing stem cells. They can almost accurately recapitulate tumor heterogeneity and microenvironment "in a dish," which surpass established cell lines and are not as expensive and time-consuming as PDTXs. As an intermediate model, tumor organoids are also used to study the fundamental issues of tumorigenesis and metastasis. They are specifically applied for drug testing and stored as "living biobanks." In this review, we highlight the translational applications of organoid technologies in tumor research and precision medicine, discuss the advantages and limitations compared with other mentioned methods, and provide our outlook on its future.

Overexpression of ubiquitin specific proteases 44 promotes the malignancy of glioma by stabilizing tumor-promoter securin.

Ubiquitin specific peptidase 44 (USP44) has been identified as an important component of spindle assemble checkpoint (SAC) to prevent the formation of aneuploidy. However, recent study raised a controversy about the effect of USP44 in tumor. Here, we first confirmed the intranuclear localization of USP44 by testing several specific antibodies to recognize endogenous USP44. Then, data from IHC and qRT-PCR assay indicated that the high expression of USP44 existed in high-grade glioma tissues and signified a poor prognosis. Knockdown of USP44 inhibited proliferation, migration and invasion, induced apoptosis, and arrested cell cycle in G2/M phase in the established glioma cell lines. Down-regulation of oncoprotein securin was detected in USP44 deficient cells, and the interaction of endogenous USP44 and securin was confirmed by immunoprecipitation in U251MG cells, which indicated that securin was a substrate of USP44, and might be stabilized by USP44. In vivo, knockdown of USP44 inhibited the tumorigenicity of U87MG cells significantly. Consequently, our findings suggested that overexpression of USP44 could enhance the malignancy of glioma via securin. USP44 might serve as a predictive biomarker, and the USP44-securin pathway might provide a new therapeutic strategy for the treatment of glioma.

Reprogramming of the Tumor in the Hypoxic Niche: The Emerging Concept and Associated Therapeutic Strategies.

Hypoxia exerts a profound impact on diverse aspects of cancer biology. Increasing evidence has revealed novel functions of hypoxia in cancer cell epigenomics, epitranscriptomics, metabolism, and intercellular communication, all hotspots of cancer research. Several drugs have been developed to target intratumoral hypoxia and have entered clinical trials to treat refractory tumors. However, direct targeting of hypoxia signaling still has limitations in the clinic with regard to cancer progression and resistance to therapy. Comprehensive understanding of the molecular mechanisms by which hypoxia reshapes tumors and their microenvironment, as well as how tumor cells adapt to and thrive in hypoxic conditions, will therefore continue to be a focus of cancer research and will provide new directions for hypoxic tumor treatment.

The bad seed gardener: Deubiquitinases in the cancer stem-cell signaling network and therapeutic resistance.

Tumors are comprised of highly heterogeneous populations of cells, of which only a small subset of stem-like cells possess the ability to regenerate tumors in vivo. These rare cancer stem cells (CSCs) have been regarded as the "bad seeds" accounted for tumor initiation, progression, metastasis, relapse and therapeutic resistance. CSC-targeted therapy seems to be a better avenue for radical cure of cancer. Deubiquitinases (DUBs), specifically disassembling ubiquitin chains, have been demonstrated to play an important role in rigidly maintaining the balance between ubiquitination and deubiquitination for protein quality control and homeostasis in normal circumstances. Dysfunction or deregulation of DUBs always leads to a series of disorders, even malignant transformation. Despite the accumulative evidence that DUB inhibitors in cancer remedy mainly target the tumor bulk, side effects like toxicity and resistance are still hard nuts to crack. In this article, we review the concept of ubiquitin proteasome system (UPS) and hallmarks of CSCs related to tumor obstinacy. We primarily summarize the CSC-related factors and signaling pathways and focus on the function of DUBs on biological traits of CSCs. We also illustrate the opportunities and challenges for the application of DUB inhibitors in the CSC-targeted therapy. Finally, we discuss the complexity of cancer stem cell hierarchy complexity and argue that a combination therapy for both CSCs and non-CSCs should be a desirable option.

Targeting Deubiquitinating Enzymes in Glioblastoma Multiforme: Expectations and Challenges.

Glioblastoma (GBM) is regarded as the most common primary intracranial neoplasm. Despite standard treatment with tumor resection and radiochemotherapy, the outcome remains gloomy. It is evident that a combination of oncogenic gain of function and tumor-suppressive loss of function has been attributed to glioma initiation and progression. The ubiquitin-proteasome system is a well-orchestrated system that controls the fate of most proteins by striking a dynamic balance between ubiquitination and deubiquitination of substrates, having a profound influence on the modulation of oncoproteins, tumor suppressors, and cellular signaling pathways. In recent years, deubiquitinating enzymes (DUBs) have emerged as potential anti-cancer targets due to their targeting several key proteins involved in the regulation of tumorigenesis, apoptosis, senescence, and autophagy. This review attempts to summarize recent studies of GBM-associated DUBs, their roles in various cellular processes, and discuss the relation between DUBs deregulation and gliomagenesis, especially how DUBs regulate glioma stem cells pluripotency, microenvironment, and resistance of radiation and chemotherapy through core stem-cell transcriptional factors. We also review recent achievements and progress in the development of potent and selective reversible inhibitors of DUBs, and attempted to find a potential GBM treatment by DUBs intervention.

The transducible TAT-RIZ1-PR protein exerts histone methyltransferase activity and tumor-suppressive functions in human malignant meningiomas.

Malignant meningiomas are a rare meningioma subtype and tend to have post-surgical recurrence. Significant endeavors have been taken to identify functional therapeutic targets to halt the growth of this aggressive cancer. We have recently discovered that RIZ1 is downregulated in high-grade meningiomas, and RIZ1 overexpression inhibits proliferation while promoting cell apoptosis of the IOMM-Lee malignant meningioma cell line. In this report, we show that the N-terminal PR domain of RIZ1 alone possessed growth-inhibitory activity and anticancer activity in primary human meningioma cells. Interestingly, the effects seem to be dependent on differential RIZ1 protein levels. Transducible TAT-RIZ1-PR protein could also inhibit meningioma tumor growth in nude mice models. We further demonstrate that PR protein exerts histone methyltransferase activity. A microarray analysis of TAT-RIZ1-PR-treated human malignant meningioma cells reveals 969 differentially expressed genes and 848 alternative splicing exons. Moreover, c-Myc and TXNIP, two putative downstream targets of H3K9 methylation, may be involved in regulating RIZ1 tumor-suppressive effects. The reciprocal relationship between RIZ1 and c-Myc was then validated in primary meningioma cells and human tumor samples. These findings provide insights into RIZ1 tumor suppression mechanisms and suggest that TAT-RIZ1-PR protein is a potential new epigenetic therapeutic agent for advanced meningiomas.

RNA interference against TMEM97 inhibits cell proliferation, migration, and invasion in glioma cells.

Gliomas are the most common form of primary brain tumor in the adult central nervous system. Altered expression and prognostic value of transmembrane protein 97 (TMEM97) has been recently reported in different types of human tumors. However, the association of TMEM97and glioma is poorly defined. Here, we reported that TMEM97 was significantly increased in glioma tissues compared to non-tumorous brain tissues. Furthermore, TMEM97 levels were progressively increased with increasing histologic tumor grade in glioma. Higher TMEM97 expression level was correlated with shorter survival time of patients with glioma. Downregulation of TMEM97 through RNA interference inhibited cell proliferation and G1/S transition in two glioma cell lines, U87 and U373. More importantly, TMEM97 silencing induced a significant decrease in the expression of G1/S transition key regulators, cyclin D1, cyclin E, CDK2, and CDK4. Additionally, downregulation of TMEM97 in glioma cells notably repressed cell migration and cell invasion. Further analysis suggested that the decreased invasion was associated with alterations in EMT markers, including E-cadherin, ß-catenin, and Twist. Since expression of TMEM97 seems to be associated with the oncogenic potential of glioma, and suppression of its expression can inhibit cancer cell growth and metastasis, TMEM97 may be a potential therapeutic target in human glioma.

Knockdown of TMEM45A inhibits the proliferation, migration and invasion of glioma cells.

Gliomas are the most common and aggressive type of primary adult brain tumor. Although high expression and prognostic value of TMEM45A has been recently reported in various types of human tumors, the association of TMEM45A expression and glioma is still unknown. Here, we reported that TMEM45A was significantly overexpressed in glioma tissues compared to non-tumorous brain tissues. Furthermore, TMEM45A mRNA levels were gradually increased with the increasing severity of histological grade of glioma. Moreover, high TMEM45A expression level was correlated with short survival time of glioma patients. Down-regulation of TMEM45A in two glioma cell lines, U251 and U373 by transected with TMEM45A siRNA resulted in a significant reduction of cell proliferation and G1-phase arrest. Additionally, we found that suppressing of TMEM45A expression in glioma cells remarkably suppressed cell migration and cell invasion. More importantly, TMEM45A siRNA treatment significantly down-regulated the proteins promoting cell cycles transition (Cyclin D1, CDK4 and PCNA) and cell invasion (MMP-2 and MMP-9), which indicted a possible mechanism underlying its functions on glioma. In summary, our study suggests that TMEM45A may work as an oncogene and a new effective therapeutic target for glioma treatment.