PI3K/AKT activation induces PTEN ubiquitination and destabilization accelerating tumourigenesis

Long noncoding RNA MALAT-1: A versatile regulator in cancer progression, metastasis, immunity, and therapeutic resistance

Long noncoding RNAs (lncRNAs) are RNA transcripts longer than 200 nucleotides that do not code for proteins but have been linked to cancer development and metastasis. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT-1) influences crucial cancer hallmarks through intricate molecular mechanisms, including proliferation, invasion, angiogenesis, apoptosis, and the epithelial-mesenchymal transition (EMT). The current article highlights the involvement of MALAT-1 in drug resistance, making it a potential target to overcome chemotherapy refractoriness. It discusses the impact of MALAT-1 on immunomodulatory molecules, such as major histocompatibility complex (MHC) proteins and PD-L1, leading to immune evasion and hindering anti-tumor immune responses. MALAT-1 also plays a significant role in cancer immunology by regulating diverse immune cell populations. In summary, MALAT-1 is a versatile cancer regulator, influencing tumorigenesis, chemoresistance, and immunotherapy responses. Understanding its precise molecular mechanisms is crucial for developing targeted therapies, and therapeutic strategies targeting MALAT-1 show promise for improving cancer treatment outcomes. However, further research is needed to fully uncover the role of MALAT-1 in cancer biology and translate these findings into clinical applications.

Cannabidiol mitigates radiation-induced intestine ferroptosis via facilitating the heterodimerization of RUNX3 with CBFβ thereby promoting transactivation of GPX4

Radiation enteritis remains a major challenge for radiotherapy against abdominal and pelvic malignancies. Nevertheless, there is no approved effective therapy to alleviate irradiation (IR)-induced gastrointestinal (GI) toxicity. In the current study, Cannabidiol (CBD) was found to mitigate intestinal injury by GPX4-mediated ferroptosis resistance upon IR exposure. RNA-sequencing was employed to investigate the underlying mechanism involved in the radio-protective effect of CBD, wherein runt-related transcription factor 3 (RUNX3) and its target genes were changed significantly. Further experiment showed that the transactivation of GPX4 triggered by the direct binding of RUNX3 to its promoter region, or by stimulating the transcriptional activity of NF-κB via RUNX3-mediated LILRB3 upregulation was critical for the anti-ferroptotic effect of CBD upon IR injury. Specially, CBD was demonstrated to be a molecular glue skeleton facilitating the heterodimerization of RUNX3 with its transcriptional chaperone core-biding factor β (CBFβ) thereby promoting their nuclear localization and the subsequent transactivation of GPX4 and LILRB3. In short, our study provides an alternative strategy to counteract IR-induced enteritis during the radiotherapy on abdominal/pelvic neoplasms.

Regulation of inflammatory response by LINC00346 via miR-25-3p-mediated modulation of the PTEN/PI3K/AKT/NF-κB pathway

Long intergenic non-coding RNA 346 (LINC00346) has been reported to be involved in the development of atherosclerosis and specific cancers by affecting signaling pathways. However, its function in inflammation has not been thoroughly studied. Therefore, its expression pattern and function were determined in the human macrophage-like cell line THP-1. Lipopolysaccharide (LPS) treatment induced the expression of LINC00346. LPS-induced NF-κB activation and proinflammatory cytokine expression were suppressed or enhanced by the overexpression or knockdown of LINC00346, respectively. Analyses using dual luciferase assay and decoy RNAs that could block RNA-RNA interactions indicated that LINC00346 improves phosphatase and tensin homolog (PTEN) expression by sponging miR-25-3p. Subsequently, PTEN suppresses phosphoinositide-3 kinase (PI3K)-mediated conversion of phosphatidylinositol-4,5-bisphosphate (PIP2) into phosphatidylinositol-3,4,5-trisphosphate (PIP3) as well as consequent activation of protein kinase B (AKT) and NF-κB. Interestingly, database analysis revealed that the expression levels of LINC00346 and PTEN were simultaneously decreased in breast cancer tissues. Further analyses conducted using a breast cancer cell line, MDA-MB-231, confirmed the functional relationship among LINC00346, miR-25-3p, and PTEN in LPS-induced activation of NF-κB. These results indicate that miR-25-3p-sponging activity of LINC00346 affects the balance between PTEN and PI3K as well as the downstream activation of AKT/NF-κB pathway in inflammatory conditions.

Plasmodium falciparum selectively degrades α-spectrin of infected erythrocytes after invasion

Remodeling the erythrocyte membrane and skeleton by the malarial parasite Plasmodium falciparum is closely associated with intraerythrocytic development. However, the mechanisms underlying this association remain unclear. In this study, we present evidence that erythrocytic α-spectrin, but not β-spectrin, was dynamically ubiquitinated and progressively degraded during the intraerythrocytic development of P. falciparum, from the ring to the schizont stage. We further observed an upregulated expression of P. falciparum phosphatidylinositol 3-kinase (PfPI3K) in the infected red blood cells during the intraerythrocytic development of the parasite. The data indicated that PfPI3K phosphorylated and activated erythrocytic ubiquitin-protein ligase, leading to increased α-spectrin ubiquitination and degradation during P. falciparum development. We further revealed that inhibition of the activity of PfPI3K impaired P. falciparum development in vitro and Plasmodium berghei infectivity in mice. These findings collectively unveil an important mechanism of PfPI3K-ubiquitin-mediated degradation of α-spectrin during the intraerythrocytic development of Plasmodium species. Proteins in the PfPI3K regulatory pathway are novel targets for effective treatment of severe malaria.

IMPORTANCE

Plasmodium falciparum is the causative agent of severe malaria that causes millions of deaths globally. The parasite invades human red blood cells and induces a cascade of alterations in erythrocytes for development and proliferation. Remodeling the host erythrocytic cytoskeleton is a necessary process during parasitization, but its regulatory mechanisms remain to be elucidated. In this study, we observed that erythrocytic α-spectrin is selectively degraded after P. falciparum invasion, while β-spectrin remained intact. We found that the α-spectrin chain was profoundly ubiquitinated by E3 ubiquitin ligase and degraded by the 26S proteasome. E3 ubiquitin ligase activity was regulated by P. falciparum phosphatidylinositol 3-kinase (PfPI3K) signaling. Additionally, blocking the PfPI3K-ubiquitin-proteasome pathway in P. falciparum-infected red blood cells reduced parasite proliferation and infectivity. This study deepens our understanding of the regulatory mechanisms of host and malarial parasite interactions and paves the way for the exploration of novel antimalarial drugs.

SF3A2 promotes progression and cisplatin resistance in triple-negative breast cancer via alternative splicing of MKRN1

Triple-negative breast cancer (TNBC) is the deadliest subtype of breast cancer owing to the lack of effective therapeutic targets. Splicing factor 3a subunit 2 (SF3A2), a poorly defined splicing factor, was notably elevated in TNBC tissues and promoted TNBC progression, as confirmed by cell proliferation, colony formation, transwell migration, and invasion assays. Mechanistic investigations revealed that E3 ubiquitin-protein ligase UBR5 promoted the ubiquitination-dependent degradation of SF3A2, which in turn regulated UBR5, thus forming a feedback loop to balance these two oncoproteins. Moreover, SF3A2 accelerated TNBC progression by, at least in part, specifically regulating the alternative splicing of makorin ring finger protein 1 (MKRN1) and promoting the expression of the dominant and oncogenic isoform, MKRN1-T1. Furthermore, SF3A2 participated in the regulation of both extrinsic and intrinsic apoptosis, leading to cisplatin resistance in TNBC cells. Collectively, these findings reveal a previously unknown role of SF3A2 in TNBC progression and cisplatin resistance, highlighting SF3A2 as a potential therapeutic target for patients with TNBC.

Substrate preference of protein kinase B isoforms can vary depending on the cell line

Many proteins in higher eukaryotes, especially those with crucial functions, have multiple isoforms with redundant roles providing protection against potential functional deficiencies in one isoform. However, these isoforms can also have some unique roles. Protein kinase B, also known as Akt, is one such protein that has three isoforms encoded on different genes. Due to high sequence similarity and the general lack of specific reagents, most studies on Akt generalize their findings and do not distinguish between the isoforms. Using an established chemical genetic strategy and a set of known Akt substrates, this work explores substrate specificity of Akt isoforms under steady state conditions in two commonly used cell lines. This strategy can be applied to study any Akt isoform-specific substrates of interest in any cell line of choice as long as the cell line can be transfected.

MKRN1 regulates the expression profiles and transcription factor activity in HeLa cells inhibition suppresses cervical cancer cell progression

Cervical cancer is one of the most common gynecologic malignancies worldwide, necessitating the identification of novel biomarkers and therapeutic targets. This study aimed to investigate the significance of MKRN1 in cervical cancer and explore its potential as a diagnostic marker and therapeutic target. The results indicated that MKRN1 expression was up-regulated in cervical cancer tissues and correlated with advanced tumor stage, higher grade, and poor patient survival. Functional studies demonstrated that targeting MKRN1 effectively inhibited cell proliferation, migration, and invasion, highlighting its critical role in tumor progression and metastasis. Moreover, the knockdown of MKRN1 resulted in altered expression patterns of six transcription factor-encoding genes, revealing its involvement in gene regulation. Co-expression network analysis unveiled complex regulatory mechanisms underlying the effects of MKRN1 knockdown on gene expression. Furthermore, the results suggested that MKRN1 might serve as a diagnostic marker for personalized treatment strategies and a therapeutic target to inhibit tumor growth, metastasis, and overcome drug resistance. The development of MKRN1-targeted interventions might hold promise for advancing personalized medicine approaches in cervical cancer treatment. Further research is warranted to validate these findings, elucidate underlying mechanisms, and translate these insights into improved management and outcomes for cervical cancer patients.

The potential role of hydrogen sulfide in cancer cell apoptosis

For a long time, hydrogen sulfide (H2S) has been considered a toxic compound, but recent studies have found that H2S is the third gaseous signaling molecule which plays a vital role in physiological and pathological conditions. Currently, a large number of studies have shown that H2S mediates apoptosis through multiple signaling pathways to participate in cancer occurrence and development, for example, PI3K/Akt/mTOR and MAPK signaling pathways. Therefore, the regulation of the production and metabolism of H2S to mediate the apoptotic process of cancer cells may improve the effectiveness of cancer treatment. In this review, the role and mechanism of H2S in cancer cell apoptosis in mammals are summarized.

Prevalence and Prognostic Significance of PIK3CA Mutation and CNV Status and Phosphorylated AKT Expression in Patients With Cervical Cancer Treated With Primary Surgery

Currently, there are limited and conflicting reports on the prognostic utility of PIK3CA and associated pathway markers for cervical cancers treated with primary surgical management. Moreover, current studies are lacking complete characterization of adjuvant treatment with RT and/or chemotherapy. We aimed to document the prevalence, clinicopathologic, adjuvant treatment details, and prognostic value of PI3K/AKT pathway mutations and copy number variation and phosphorylated AKT status in patients with cervical cancers treated with primary surgery. A clinicopathologic review was performed on a retrospective cohort of 185 patients with cervical cancer, treated with primary surgery at a single tertiary institution. Next-generation sequencing and digital PCR was used to determine PI3K/AKT pathway mutational status and PIK3CA copy number variation, respectively, and fluorescent immunohistochemistry measured phosphorylated AKT expression. In all, 179 of 185 (96.8%) of tumors were successfully sequenced; 48 (26.8%) were positive for PI3K/AKT pathway mutations-the majority (n=37, 77.1%) PIK3CA mutations. PIK3CA mutation was associated with pathologically positive lymph nodes [12 (32%) vs. 22 (16%); P =0.022] and indication for postoperative chemoradiotherapy [17 (45.9%) vs. 32 (22.5%); P =0.004]. On multivariable analysis, PIK3CA status was not associated with overall survival ( P =0.103) or progression-free survival ( P =0.240) at 5 yrs, nor was PIK3CA copy number variation status. phosphorylated AKT ≤ median significantly predicted for progression-free survival [multivariable hazard ratio 0.39 (0.17-0.89; P =0.025)] but not overall survival ( P =0.087). The correlation of PIK3CA with pathologic positive lymph node status yet lack of association with survival outcomes may be due to the use of adjuvant postoperative therapy. PIK3CA assessment before radical hysterectomy may help identify patients with a higher risk of node-positive disease.

Oxidized Low-Density Lipoprotein Accumulation in Macrophages Impairs Lipopolysaccharide-Induced Activation of AKT2, ATP Citrate Lyase, Acetyl-Coenzyme A Production, and Inflammatory Gene H3K27 Acetylation

The accumulation of lipid and the formation of macrophage foam cells is a hallmark of atherosclerosis, a chronic inflammatory disease. To better understand the role of macrophage lipid accumulation in inflammation during atherogenesis, we studied early molecular events that follow the accumulation of oxidized low-density lipoprotein (oxLDL) in cultured mouse macrophages. We previously showed that oxLDL accumulation downregulates the inflammatory response in conjunction with downregulation of late-phase glycolysis. In this study, we show that within hours after LPS stimulation, macrophages with accumulated oxLDL maintain early-phase glycolysis but selectively downregulate activation of AKT2, one of three AKT isoforms. The inhibition of AKT2 activation reduced LPS-induced ATP citrate lyase activation, acetyl-CoA production, and acetylation of histone 3 lysine 27 (H3K27ac) in certain inflammatory gene promoters. In contrast to oxLDL, multiple early LPS-induced signaling pathways were inhibited in macrophages with accumulated cholesterol, including TBK1, AKT1, AKT2, MAPK, and NF-κB, and early-phase glycolysis. The selective inhibition of LPS-induced AKT2 activation was dependent on the generation of mitochondrial oxygen radicals during the accumulation of oxLDL in macrophages prior to LPS stimulation. This is consistent with increased oxidative phosphorylation, fatty acid synthesis, and oxidation pathways found by comparative transcriptomic analyses of oxLDL-loaded versus control macrophages. Our study shows a functional connection between oxLDL accumulation, inactivation of AKT2, and the inhibition of certain inflammatory genes through epigenetic changes that occur soon after LPS stimulation, independent of early-phase glycolysis.

The role of ubiquitination and deubiquitination in PI3K/AKT/mTOR pathway: A potential target for cancer therapy

The PI3K/AKT/mTOR pathway controls key cellular processes, including proliferation and tumor progression, and abnormally high activation of this pathway is a hallmark in human cancers. The post-translational modification, such as Ubiquitination and deubiquitination, fine-tuning the protein level and the activity of members in this pathway play a pivotal role in maintaining normal physiological process. Emerging evidence show that the unbalanced ubiquitination/deubiquitination modification leads to human diseases via PI3K/AKT/mTOR pathway. Therefore, a comprehensive understanding of the ubiquitination/deubiquitination regulation of PI3K/AKT/mTOR pathway may be helpful to uncover the underlying mechanism and improve the potential treatment of cancer via targeting this pathway. Herein, we summarize the latest research progress of ubiquitination and deubiquitination of PI3K/AKT/mTOR pathway, systematically discuss the associated crosstalk between them, as well as focus the clinical transformation via targeting ubiquitination process.

Revealing the role of epigenetic and post-translational modulations of autophagy proteins in the regulation of autophagy and cancer: a therapeutic approach

Autophagy is a process that is characterized by the destruction of redundant components and the removal of dysfunctional ones to maintain cellular homeostasis. Autophagy dysregulation has been linked to various illnesses, such as neurodegenerative disorders and cancer. The precise transcription of the genes involved in autophagy is regulated by a network of epigenetic factors. This includes histone modifications and histone-modifying enzymes. Epigenetics is a broad category of heritable, reversible changes in gene expression that do not include changes to DNA sequences, such as chromatin remodeling, histone modifications, and DNA methylation. In addition to affecting the genes that are involved in autophagy, the epigenetic machinery can also alter the signals that control this process. In cancer, autophagy plays a dual role by preventing the development of tumors on one hand and this process may suppress tumor progression. This may be the control of an oncogene that prevents autophagy while, conversely, tumor suppression may promote it. The development of new therapeutic strategies for autophagy-related disorders could be initiated by gaining a deeper understanding of its intricate regulatory framework. There is evidence showing that certain machineries and regulators of autophagy are affected by post-translational and epigenetic modifications, which can lead to alterations in the levels of autophagy and these changes can then trigger disease or affect the therapeutic efficacy of drugs. The goal of this review is to identify the regulatory pathways associated with post-translational and epigenetic modifications of different proteins in autophagy which may be the therapeutic targets shortly.

Site-specific protein conjugates incorporating Para-Azido-L-Phenylalanine for cellular and in vivo imaging

This work features the use of amber suppression-mediated unnatural amino acid (UAA) incorporation into proteins for various imaging purposes. The site-specific incorporation of the UAA, p-azido-L-phenylalanine (pAzF), provides an azide handle that can be used to complete the strain promoted azide-alkyne click cycloaddition (SPAAC) reaction to introduce an imaging modality such as a fluorophore or a positron emission tomography (PET) tracer on the protein of interest (POI). Such methodology can be pursued directly in mammalian cell lines or on proteins expressed in vitro, thereby conferring a homogeneous pool of protein conjugates. A general procedure for UAA incorporation to use with a site-specific protein labeling method is provided allowing for in vitro and in vivo imaging applications based on the representative proteins PTEN and PD-L1. This approach would help elucidate the cellular or in vivo biological activities of the POI.

MKRN1 promotes colorectal cancer metastasis by activating the TGF-β signalling pathway through SNIP1 protein degradation

BACKGROUND

The Makorin ring finger protein 1 (MKRN1) gene, also called RNF61, is located on the long arm of chromosome 7 and is a member of the RING finger protein family. The E3 ubiquitin ligase MKRN1 is closely linked to tumour development, but the exact mechanism needs to be elucidated. In this study, we aimed to investigate the specific mechanism and role of MKRN1 in colorectal cancer (CRC) development.

METHODS

MKRN1 expression in CRC was analysed using the Cancer Cell Line Encyclopaedia and the Cancer Genome Atlas (TCGA) databases. Rectal tumour tissues were frozen to explore the MKRN1 expression in CRC and its clinical significance. The impact of MKRN1 on CRC cell proliferation and migration was observed using CCK8, colony formation, wound healing, and transwell assays. A combination of MKRN1 quantitative proteomics, ubiquitination modification omics analysis, and a string of in vitro and in vivo experiments revealed the potential mechanisms by which MKRN1 regulates CRC metastasis.

RESULTS

MKRN1 expression was significantly elevated in CRC tissues compared to paracancerous tissues and was positively linked with prognosis (P < 0.01). MKRN1 downregulation inhibits CRC cell proliferation, migration, and invasion. Conversely, MKRN1 overexpression promotes the proliferation, migration, and invasion of CRC cells. Mechanistically, MKRN1 induces epithelial-mesenchymal transition (EMT) in CRC cells via ubiquitination and degradation of Smad nuclear-interacting protein 1 (SNIP1). Furthermore, SNIP1 inhibits transforming growth factor-β (TGF-β) signalling, and MKRN1 promotes TGF-β signalling by degrading SNIP1 to induce EMT in CRC cells. Finally, using conditional knockout mice, intestinal lesions and metastatic liver microlesions were greatly reduced in the intestinal knockout MKRN1 group compared to that in the control group.

CONCLUSIONS

High MKRN1 levels promote TGF-β signalling through ubiquitination and degradation of SNIP1, thereby facilitating CRC metastasis, and supporting MKRN1 as a CRC pro-cancer factor. The MKRN1/SNIP1/TGF-β axis may be a potential therapeutic target in CRC.

The Upregulation of GSTO2 is Associated with Colon Cancer Progression and a Poor Prognosis

Colorectal cancer is the second-leading cause of cancer-related mortality in the United States. Glutathione S-transferase can affect the development of cancer. Glutathione S-transferase omega 2, a member of the GST family, plays an important role in many tumors. However, the role of Glutathione S-transferase omega 2 in the development of colon cancer remains unclear. Herein, our study aimed to investigate the exact role of Glutathione S-transferase omega 2 in colon cancer. We used RNA sequencing data from The Cancer Genome Atlas and the Genotype-Tissue Expression database to analyze Glutathione S-transferase omega 2 expressions. Then, we explore the protein information of Glutathione S-transferase omega 2 in the Human Protein Atlas, GeneCards, and String database. In addition, western blot and immunohistochemistry were performed to evaluate the protein levels of Glutathione S-transferase omega 2 in colon cancer tissues. We acquire data from the Gene Expression Omnibus and The Cancer Genome Atlas databases. Also, we performed relevant prognostic analyses of these data. In addition, we performed a statistical analysis of the clinical data from The Cancer Genome Atlas database and the expression level of Glutathione S-transferase omega 2. Then, we performed Cox regression analysis and found independent risk factors for prognosis in patients with colon cancer. The Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses were used to explore the potential biological functions of Glutathione S-transferase omega 2. The infiltration of colon cancer-immune cells was evaluated by the CIBERSORT method. RNA silencing was performed using siRNA constructs in HCT-116 and HT-29 cell lines. Cell Counting Kit-8 and EdU assays were performed to determine cell proliferation. Transwell experiments and scratch tests were used to determine cell migration. As for the mRNA and protein expression levels of cells, we used quantitative real-time PCR and western blot to detect them. Our research shows that Glutathione S-transferase omega 2 is overexpressed in colon cancer patients, and this overexpression is associated with a poor prognosis. The high expression of Glutathione S-transferase omega 2 is significantly correlated stage with stage, M, and N classification progression in colon cancer by statistical analysis. Univariate and multivariate Cox regression analyses showed that Glutathione S-transferase omega 2 was an independent risk factor for poor prognosis in colon cancer. In addition, we also found that Glutathione S-transferase omega 2 expression levels can affect the immune microenvironment of colon cancer cells. Gene silencing of Glutathione S-transferase omega 2 in HT-29 and HCT-116 cells significantly inhibited tumor growth and migration. In summary, we found that Glutathione S-transferase omega 2 can be used as a molecular indicator of colon cancer prognosis. In vitro, gene silencing of Glutathione S-transferase omega 2 inhibited colon cancer cells' growth and migration.

Emerging roles of circular RNAs in gastric cancer metastasis and drug resistance

Gastric cancer (GC) is an aggressive malignancy with a high mortality rate and poor prognosis, primarily caused by metastatic lesions. Improved understanding of GC metastasis at the molecular level yields meaningful insights into potential biomarkers and therapeutic targets. Covalently closed circular RNAs (circRNAs) have emerged as crucial regulators in diverse human cancers including GC. Furthermore, accumulating evidence has demonstrated that circRNAs exhibit the dysregulated patterns in GC and have emerged as crucial regulators in GC invasion and metastasis. However, systematic knowledge regarding the involvement of circRNAs in metastatic GC remains obscure. In this review, we outline the functional circRNAs related to GC metastasis and drug resistance and discuss their underlying mechanisms, providing a comprehensive delineation of circRNA functions on metastatic GC and shedding new light on future therapeutic interventions for GC metastases.

The E3 Ligases in Cervical Cancer and Endometrial Cancer

Endometrial (EC) and cervical (CC) cancers are the most prevalent malignancies of the female reproductive system. There is a global trend towards increasing incidence and mortality, with a decreasing age trend. E3 ligases label substrates with ubiquitin to regulate their activity and stability and are involved in various cellular functions. Studies have confirmed abnormal expression or mutations of E3 ligases in EC and CC, indicating their vital roles in the occurrence and progression of EC and CC. This paper provides an overview of the E3 ligases implicated in EC and CC and discusses their underlying mechanism. In addition, this review provides research advances in the target of ubiquitination processes in EC and CC.

Distinctive gene expression patterns in pregnancy-associated breast cancer

Pregnancy-associated breast cancer (PABC) is diagnosed during pregnancy or within 1 year postpartum, but the unique aspects of its etiology and pathogenesis have not been fully elucidated. This study aimed to ascertain the molecular mechanisms of PABC to facilitate diagnosis and therapeutic development. The Limma package was used to characterize the differentially expressed genes in PABC as compared to non-pregnancy-associated breast cancer (NPABC) and normal breast tissue. A total of 871 dysregulated genes were identified in the PABC versus NPABC groups and 917 in the PABC versus normal groups, with notable differences in the expression of MAGE and CXCL family genes. The dysregulated genes between the PABC and normal groups were mainly associated with signal transduction and immune response, while Kyoto Encyclopedia of Genes and Genomes analysis revealed that the dysregulated genes were enriched in immune-related pathways, including the major histocompatibility complex (MHC) class II protein complex, the type I interferon signaling pathway, regulation of α-β T-cell proliferation, and the T-cell apoptotic process. Through protein-protein interaction network construction, CD44 and BRCA1 were identified as prominent hub genes with differential expression in PABC versus NPABC. Furthermore, a cluster with eleven hub genes was identified in PABC versus normal adjacent tissues, of which the expression of EGFR, IGF1, PTGS2, FGF1, CAV1, and PLCB1 were verified to be differentially expressed in an independent cohort of PABC patients. Notably, IGF1, PTGS2, and FGF1 were demonstrated to be significantly related to patient prognosis. Our study reveals a distinctive gene expression pattern in PABC and suggests that IGF1, PTGS2, and FGF1 might serve as biomarkers for diagnosis and prognosis of PABC.

The Role of PTEN in Epithelial–Mesenchymal Transition

Simple Summary

The PTEN phosphatase is a ubiquitously expressed tumor suppressor, which inhibits the PI3K/AKT pathway in the cell. The PI3K/AKT pathway is considered to be one of the main signaling pathways that drives the proliferation of cancer cells. Furthermore, the same pathway controls the epithelial–mesenchymal transition (EMT). EMT is an evolutionarily conserved developmental program, which, upon aberrant reactivation, is also involved in the formation of cancer metastases. Importantly, metastasis is the leading cause of cancer-associated deaths. In this review, we discuss the literature data that highlight the role of PTEN in EMT. Based on this knowledge, we speculate about new possible strategies for cancer treatment.

Abstract

Phosphatase and Tensin Homolog deleted on Chromosome 10 (PTEN) is one of the critical tumor suppressor genes and the main negative regulator of the PI3K pathway. PTEN is frequently found to be inactivated, either partially or fully, in various malignancies. The PI3K/AKT pathway is considered to be one of the main signaling cues that drives the proliferation of cells. Perhaps it is not surprising, then, that this pathway is hyperactivated in highly proliferative tumors. Importantly, the PI3K/AKT pathway also coordinates the epithelial–mesenchymal transition (EMT), which is pivotal for the initiation of metastases and hence is regarded as an attractive target for the treatment of metastatic cancer. It was shown that PTEN suppresses EMT, although the exact mechanism of this effect is still not fully understood. This review is an attempt to systematize the published information on the role of PTEN in the development of malignant tumors, with a main focus on the regulation of the PI3K/AKT pathway in EMT.

PTEN/AKT signaling pathway related to hTERT downregulation and telomere shortening induced in Toxoplasma GRA16-expressing colorectal cancer cells

This study investigated whether the molecular mechanism of granule protein 16 (GRA16), a dense granule protein of Toxoplasma gondii (T. gondii) that induces cancer cell apoptosis, results in telomere shortening in cancer cells. The molecular mechanism of GRA16 responsible for regulating telomerase reverse transcriptase (hTERT) activity and telomere shortening was investigated using GRA16-transferred HCT116 human colorectal cancer cells (GRA16-stable cells). GRA16 directly decreased hTERT expression by downregulating the expression and phosphorylation of hTERT transcriptional factors accompanied by decreased expression of shelterin complex molecules. Moreover, GRA16 resulted in cancer cell death through reduction of telomerase activity which leads to telomere shortening (decreased relative ratio of telomeric repeat-amplified sequence to that of a single-copy gene) (T/S ratio)), and at the same time gamma-H2A histone family member X (γ-H2A.X) stained nucleus was increased in the cells. The molecular mechanism between GRA16 and hTERT inactivation was revealed using inhibitors for phosphatase and tensin homolog (PTEN) and protein phosphatase 2A (PP2A) as well as siRNAs against PTEN and PP2A. hTERT dephosphorylation was induced effectively by the signaling pathway of HAUSP/PTEN/p-AKT(S473) but not by PP2A-B55/p-AKT(T308). Inhibition of the PTEN signaling pathway increased mRNA expressions in hTERT transcriptional factors, cell cycle activating factors, and apoptosis-inhibiting factors. When HCT116 cells were infected with T. gondii, the number of γ-H2A.X-stained nuclei also increased and p-hTERT/hTERT decreased as in GRA16-stable cells. Altogether, our results emphasize that GRA16 is a novel promising telomerase inhibitor that causes telomere shortening through telomerase inactivation by inducing the activation of the tumor suppressor PTEN.

Host MKRN1-Mediated Mycobacterial PPE Protein Ubiquitination Suppresses Innate Immune Response

Mycobacterium tuberculosis (Mtb), as an important intracellular pathogen, can invade and survive in macrophages and is capable of escaping the clearance of immune system. Despite decades of research efforts, the precise mechanism of immune escape and the virulence factors encoded by Mtb involved remain to be explored. Mtb-specific genomic regions of deletion (RD)-encoded proteins and PE/PPE family proteins have been implicated in immune evasion. Here, we screened more than forty RD-encoded proteins which might be involved in facilitating bacterial survival in macrophages, and found that a Mtb PPE68/Rv3873 protein, encoded by Mtb-RD1, is essential for efficient Mtb intracellular survival in macrophages. In terms of mechanism, we found that the ubiquitin ligase (E3) Makorin Ring Finger Protein 1 (MKRN1) of macrophage interacted with PPE68 and promoted the attachment of lysine (K)-63-linked ubiquitin chains to the K166 site of PPE68. K63-ubiquitination of PPE68 further bound src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP1) to suppress K63-linked polyubiquitin chains of tumor necrosis factor receptor-associated factor 6 (TRAF6), and then remarkably suppressed TRAF6-driven NF-κB and AP-1 signaling and TNF-α, IL-6 and NO production. We demonstrate that the K63-linked ubiquitination of PPE68 by MKRN1 contributed to the PPE68-mediated mycobacterial immune escape. Our finding identifies a previously unrecognized mechanism by which host MKRN1-mediated-ubiquitination of mycobacterial PPE protein suppresses innate immune responses. Disturbing the interaction between host MKRN1 ubiquitin system and mycobacterial PPE protein might be a potential therapeutic target for tuberculosis.

MRKNs: Gene, Functions, and Role in Disease and Infection

The makorin RING finger protein (MKRN) gene family encodes proteins (makorins) with a characteristic array of zinc-finger motifs present in a wide array from invertebrates to vertebrates. MKRNs (MKRN1, MKRN2, MKRN3, MKRN4) as RING finger E3 ligases that mediate substrate degradation are related with conserved RING finger domains that control multiple cellular components via the ubiquitin-proteasome system (UPS), including p53, p21, FADD, PTEN, p65, Nptx1, GLK, and some viral or bacterial proteins. MKRNs also served as diverse roles in disease, like MKRN1 in transcription regulation, metabolic disorders, and tumors; MKRN2 in testis physiology, neurogenesis, apoptosis, and mutation of MKRN2 regulation signals transduction, inflammatory responses, melanoma, and neuroblastoma; MKRN3 in central precocious puberty (CPP) therapy; and MKRN4 firstly reported as a novel E3 ligase instead of a pseudogene to contribute to systemic lupus erythematosus (SLE). Here, we systematically review advances in the gene’s expression, function, and role of MKRNs orthologs in disease and pathogens infection. Further, MKRNs can be considered targets for the host’s innate intracellular antiviral defenses and disease therapy.

Hyperoside Ameliorates DSS-Induced Colitis through MKRN1-Mediated Regulation of PPARγ Signaling and Th17/Treg Balance

Hyperoside (HYP), a naturally occurring flavonoid compound, exerts multiple biological functions including myocardial protection, antiredox, and anti-inflammatory activities. However, the role of HYP on inflammatory bowel disease (IBD) and the underlying mechanism need to be further established. Here, we show that HYP treatment profoundly alleviated dextran sulfate sodium-induced ulcerative colitis in mice, characterized by reduced pathological scores, preserved tissue integrity, suppressed colonic inflammation, and balanced Th17/Treg response. Mechanistically, HYP was shown to restrain the expression of the E3 ubiquitin ligase, makorin ring finger protein 1 (MKRN1), which in turn promoted the ubiquitination and proteasomal degradation of peroxisome proliferator-activated receptor gamma (PPARγ), an essential regulator of Th17 and Treg differentiation. Consequently, HYP treatment enhanced PPARγ signaling and hence promoted Treg differentiation while suppressing Th17 cell development during colitis. Thus, our data indicate that HYP acts through the MKRN1/PPARγ axis to modulate the Th17/Treg axis and thereby confers protection against experimental colitis. The findings extend our understanding about HYP action and may provide a potential therapeutic target for IBD.

Regulation of the tumor suppressor PTEN in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype of breast cancer (BCa) in which estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2) are not expressed. Although TNBC cases account for approximately 15% of all BCa cases, TNBC patients' prognosis is poor compared with that of other BCa subtypes. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) plays an important role in cell proliferation and migration by negatively regulating the PI3K/Akt pathway. PTEN is one of the most commonly inactivated tumor suppressors in BCa. PTEN inactivity is associated with larger tumor sizes, multiple lymph node metastases, and an aggressive triple-negative phenotype. This review primarily focuses on two key points: (1) PTEN and its function. (2) The regulation of tumor suppressor PTEN in TNBC. We provide a summary of genomic alterations of PTEN in BCa. We further discuss the transcriptional regulation of PTEN and how PTEN is regulated by posttranscription and posttranslational modification, as well as by protein interactions. Finally, we discuss the perspectives of the PTEN protein in TNBC.

Bone morphogenetic protein 9 enhances osteogenic and angiogenic responses of human amniotic mesenchymal stem cells cocultured with umbilical vein endothelial cells through the PI3K/AKT/m-TOR signaling pathway

Background: Neovascularization plays an essential part in bone fracture and defect healing, constructing tissue engineered bone that targets bone regeneration. Bone morphogenetic protein 9 (BMP9) is a regular indicator that potentiates osteogenic and angiogenic differentiation of MSCs.

Objectives: To investigate the effects of BMP9 on osteogenesis and angiogenesis of human amniotic mesenchymal stem cells (hAMSCs) cocultured with human umbilical vein endothelial cells (HUVECs) and determine the possible underlying molecular mechanism.

Results: The isolated hAMSCs expressed surface markers of MSCs. hAMSCs cocultured with HUVECs enhance osteogenic differentiation and upregulate the expression of angiogenic factors. BMP9 not only potentiates angiogenic signaling of hAMSCs cocultured with HUVECs also increases ectopic bone formation and subcutaneous vessel invasion. Mechanically, the coupling effect between osteogenesis and angiogenesis induced by BMP9 was activated by the BMP/Smad and PI3K/AKT/m-TOR signaling pathways.

Conclusions: BMP9-enhanced osteoblastic and angiogenic differentiation in cocultivation with hAMSCs and HUVECs in vitro and in vivo also provide a chance to harness the BMP9-regulated coordinated effect between osteogenic and angiogenic pathways through BMP/Smad and PI3K/AKT/m-TOR signalings.

Materials and Methods: The ALP and Alizarin Red S staining assay to determine the effects of osteoblastic differentiation. RT-qPCR and western blot was measured the expression of angiogenesis-related factors. Ectopic bone formation was established and retrieved bony masses were subjected to histochemical staining. The angiogenesis ability and vessel invasion were subsequently determined by immunofluorescence staining. Molecular mechanisms such as the BMP/Smad and PI3K/AKT/m-TOR signaling pathways were detected by ELISA and western blot analysis.

MicroRNA 142-5p promotes tumor growth in oral squamous cell carcinoma via the PI3K/AKT pathway by regulating PTEN

MicroRNAs (miRNAs) play an important role in carcinogenesis and cancer progression. The purpose of this study was to identify miRNAs associated with carcinoma function in OSCC and to investigate the potential role of the specific miRNAs. First, a comprehensive microarray analysis was performed, and miR-142-5p was identified as a candidate miRNA involved in OSCC. miR-142-5p has been reported to show high expression levels in cancer patients and to be involved in tumor growth and metastasis. However, the expression and function of miR-142-5p in oral squamous cell carcinoma (OSCC) are not fully characterized. We evaluated miR-142-5p expression in both OSCC-derived cell lines and primary OSCC tissues and performed functional analysis of miR-142-5p in OSCC-derived cell lines using mimics and inhibitors. miR-142-5p expression was up-regulated in OSCC tissues and OSCC cell lines. Overexpression of miR-142-5p significantly promoted the proliferation and invasion of OSCC cells. Bioinformatics analysis was performed using TargetScan to predict potential target sites that match the seed region of miR-142-5p. Phosphatase and tensin homolog deleted on chromo-some 10 (PTEN) was identified as a potential target and selected for further analysis. PTEN expression levels were down-regulated and AKT expression levels were up-regulated in miR-142-5p-overexpressing cells. We have shown that miR-142-5p targets the PTEN gene and is involved in cancer progression. Our results suggest that miR-142-5p is involved in the progression of OSCC by controlling the phosphatidylinositol 3-kinase (PI3K)/AKT pathway by targeting the PTEN gene. Our findings suggest that miR-142-5p may be a new target for the treatment of OSCC.

Epigenetic and post-transcriptional regulation of somatostatin receptor subtype 5 (SST5 ) in pituitary and pancreatic neuroendocrine tumors

Somatostatin receptor subtype 5 (SST₅) is an emerging biomarker and actionable target in pituitary (PitNETs) and pancreatic (PanNETs) neuroendocrine tumors. Transcriptional and epigenetic regulation of SSTR5 gene expression and mRNA biogenesis is poorly understood. Recently, an overlapping natural antisense transcript, SSTR5‐AS1, potentially regulating SSTR5 expression, was identified. We aimed to elucidate whether epigenetic processes contribute to the regulation of SSTR5 expression in PitNETs (somatotropinomas) and PanNETs. We analyzed the SSTR5/SSTR5‐AS1 human locus in silico to identify CpG islands. SSTR5 and SSTR5‐AS1 expression was assessed by quantitative real‐time PCR (qPCR) in 27 somatotropinomas, 11 normal pituitaries (NPs), and 15 PanNETs/paired adjacent (control) samples. We evaluated methylation grade in four CpG islands in the SSTR5/SSTR5‐AS1 genes. Results revealed that SSTR5 and SSTR5‐AS1 were directly correlated in NP, somatotropinoma, and PanNET samples. Interestingly, selected CpG islands were differentially methylated in somatotropinomas compared with NPs. In PanNETs cell lines, SSTR5‐AS1 silencing downregulated SSTR5 expression, altered aggressiveness features, and influenced pasireotide response. These results provide evidence that SSTR5 expression in PitNETs and PanNETs can be epigenetically regulated by the SSTR5‐AS1 antisense transcript and, indirectly, by DNA methylation, which may thereby impact tumor behavior and treatment response.

Circular RNA hsa_circ_0000730 restrains cell proliferation, migration, and invasion in cervical cancer through miR-942-5p/PTEN axis

Circular RNAs (circRNAs) play prominent roles in regulating the progression of cancers. This study is aimed to decipher the role of hsa_circ_0000730 in cervical cancer (CC).The differentially expressed circRNAs of CC were screened out from the Gene Expression Omnibus database. qRT-PCR was used to detect circ_0000730 expression in CC tissues and cell lines, and the Kaplan-Meier curve was adopted to figure out the relationship between circ_000730 expression and the overall survival time of CC patients. BrdU assay and Tanswell assay were utilized to examine the proliferation, migration, and invasion of CC cells. Western blot was adopted to detect PTEN protein expression. Bioinformatics analysis and dual-luciferase reporter assay were used to examine the target relationship between miR-942-5p and circ_0000730 or PTEN, respectively.Circ_0000730 was among the differentially expressed circRNAs in CC. Circ_0000730 was significantly down-regulated in the cancer tissues of 50 CC patients and CC cell lines. Additionally, underexpression of circ_0000730 was associated with the shorter survival time of CC patients. Gain- and loss-of-function assays highlighted that circ_0000730 significantly inhibited the proliferation, migration, and invasion of CC cells. Mechanistically, miR-942-5p was identified as a downstream target of circ_0000730, and circ_0000730 could positively regulate PTEN expression via repressing miR-942-5p in CC cells.Circ_0000730 inhibits the proliferation, migration, and invasion of CC cells via regulating miR-942-5p/PTEN axis. Circ_0000730 probably acts as a tumor suppressor in CC, and it may be a candidate target for the treatment of CC.

Tetrandrine suppresses the growth of human osteosarcoma cells by regulating multiple signaling pathways

Although osteosarcoma (OS) is the most common malignant tumor among juvenile bone tumors, its treatment plan and clinical outcome have not improved significantly in recent decades. Tetrandrine (TET), a Chinese medicine that is usually used in the therapy of silicosis, hypertension and arthritis, has been confirmed by many studies to possess potent antitumour growth properties, but there are different limitations when describing specific mechanisms. Here, we found that TET can obviously prevent the proliferation, migration and invasion of both 143B and MG63 cells and promote their apoptosis in vitro. Our results for luciferase reporter and Western blotting assays show that TET may exert its antitumour activity by regulating multiplex signaling pathways, including the MAPK/Erk, PTEN/Akt, Juk and Wnt signaling pathways. Furthermore, the regulatory effect of TET on OS cells and related signaling pathways was verified again in vivo. Our findings suggest that the anticancer function of TET on human OS may be mediated by its targeting of multiple signaling pathways and that TET may be used as a single drug or in combination with other drugs during the treatment of OS.

Acylglycerol Kinase-Targeted Therapies in Oncology

Acylglycerol kinase (AGK) is a recently discovered mitochondrial lipid kinase, and mutation of its gene is the fundamental cause of Sengers syndrome. AGK is not only involved in the stability of lipid metabolism but also closely related to mitochondrial protein transport, glycolysis, and thrombocytopoiesis. Evidence indicates that AGK is an important factor in the occurrence and development of tumors. Specifically, AGK has been identified as an oncogene that partakes in the regulation of tumor cell growth, invasion, metastasis, and drug resistance. The versatility of AGK and its unique role in different types of cancerous and normal cells greatly piqued our interest. We believe that AGK is a promising target for cancer therapy. Therefore, this review summarizes the main research advances concerning AGK, including the discovery of its physiological/pathogenic mechanisms, and provides a reference for the feasible evaluation of AGK as a therapeutic target for human diseases, particularly tumors.

From Micro to Long: Non-Coding RNAs in Tamoxifen Resistance of Breast Cancer Cells

Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer mortality among women. Two thirds of patients are classified as hormone receptor positive, based on expression of estrogen receptor alpha (ERα), the main driver of breast cancer cell proliferation, and/or progesterone receptor, which is regulated by ERα. Despite presenting the best prognosis, these tumors can recur when patients acquire resistance to treatment by aromatase inhibitors or antiestrogen such as tamoxifen (Tam). The mechanisms that are involved in Tam resistance are complex and involve multiple signaling pathways. Recently, roles for microRNAs and lncRNAs in controlling ER expression and/or tamoxifen action have been described, but the underlying mechanisms are still little explored. In this review, we will discuss the current state of knowledge on the roles of microRNAs and lncRNAs in the main mechanisms of tamoxifen resistance in hormone receptor positive breast cancer. In the future, this knowledge can be used to identify patients at a greater risk of relapse due to the expression patterns of ncRNAs that impact response to Tam, in order to guide their treatment more efficiently and possibly to design therapeutic strategies to bypass mechanisms of resistance.

MicroRNA-103a-3p Promotes Cell Proliferation and Invasion in Non-Small-Cell Lung Cancer Cells through Akt Pathway by Targeting PTEN

Background

Increasing evidence has suggested that microRNA- (miR-) 103a-3p is crucial for cancer progression. However, the specific mechanism of miR-103a-3p in non-small-cell lung cancer (NSCLC) remains unclear until now. So, it is particularly urgent to clarify the mechanism between them.

Methods

qRT-PCR and western blot were used to measure the expression of miR-103a-3p, PTEN, Akt, and p-Akt. Cell biology experiment was applied to detect the biological function of miR-103a-3p in NSCLC cell lines. Moreover, bioinformatics analysis, luciferase reporter assay, and functional complementation analysis were carried out to investigate the target gene.

Results

miR-103a-3p was highly expressed in primary NSCLC samples and cell lines. miR-103a-3p mimics promoted the proliferation and invasion of NSCLC cells; miR-103a-3p inhibitor had the opposite effect. A double luciferase reporter gene experiment revealed that miR-103a-3p directly targets the PTEN mRNA 3'UTR region. siPTEN inhibited the proliferation and invasion of NSCLC cells. Further mechanistic studies showed that both overexpression of miR-103a-3p and PTEN knockdown reduced the expression of the p-Akt protein. Overexpression of PTEN partially reversed the cancer-promoting effect of miR-103a-3p.

Conclusion

miR-103a-3p promotes the progression of NSCLC via Akt signaling by targeting PTEN, highlighting the role of miR-103a-3p/PTEN/Akt signaling and suggesting miR-103a-3p as a novel therapeutic target for NSCLC.

Pentamidine Inhibits Ovarian Cancer Cell Proliferation and Migration by Maintaining Stability of PTEN in vitro

Purpose

Pentamidine is an anti-protozoal cationic aromatic diamidine drug and has been reported to exhibit anticancer properties. We aimed to identify the effect of pentamidine on proliferation and migration of human ovarian cancer (OC) cell lines and the related mechanisms.

Methods

HO8910 and Caov3 ovarian cancer cells were treated with pentamidine. MTS and colony formation assays were used to detect the proliferation ability of cells. The migration of cells was detected using wound healing and transwell assays. The protein levels of PTEN, phosphorylated Akt, Akt, N-cadherin, E-cadherin and snail were detected by Western blotting. Immunoprecipitation and Western blotting were used to detect ubiquitination levels of PTEN.

Results

Our findings revealed that pentamidine inhibited both proliferation and migration of OC cells. Further investigation found that pentamidine increased the protein expression of PTEN and reduced phosphorylation levels of AKT in OC cells. Pentamidine treatment modulated PTEN stability through the ubiquitin/proteasome pathway. In addition, pentamidine inhibited the expression of N-cadherin and snail, and increased E-cadherin expression in a dose-dependent manner.

Conclusion

Pentamidine is involved in the maintenance of PTEN protein stability and suppresses proliferation and migration of OC cells.

Targeting therapy-resistant lung cancer stem cells via disruption of the AKT/TSPYL5/PTEN positive-feedback loop

Cancer stem cells (CSCs) are regarded as essential targets to overcome tumor progression and therapeutic resistance; however, practical targeting approaches are limited. Here, we identify testis-specific Y-like protein 5 (TSPYL5) as an upstream regulator of CSC-associated genes in non-small cell lung cancer cells, and suggest as a therapeutic target for CSC elimination. TSPYL5 elevation is driven by AKT-dependent TSPYL5 phosphorylation at threonine-120 and stabilization via inhibiting its ubiquitination. TSPYL5-pT120 also induces nuclear translocation and functions as a transcriptional activator of CSC-associated genes, ALDH1 and CD44. Also, nuclear TSPYL5 suppresses the transcription of PTEN, a negative regulator of PI3K signaling. TSPYL5-pT120 maintains persistent CSC-like characteristics via transcriptional activation of CSC-associated genes and a positive feedback loop consisting of AKT/TSPYL5/PTEN signaling pathway. Accordingly, elimination of TSPYL5 by inhibiting TSPYL5-pT120 can block aberrant AKT/TSPYL5/PTEN cyclic signaling and TSPYL5-mediated cancer stemness regulation. Our study suggests TSPYL5 be an effective target for therapy-resistant cancer.

In order to assist the development of cancer stem cell (CSC) therapy, Kim et al identified testis-specific Y-like protein 5 (TSPYL5) as an upstream regulator of CSC-associated genes in non-small cell lung cancer cells. They demonstrated in cancer cell lines and in vivo that TSPYL5 activity is dependent on AKT signalling and that disruption of TSPYL5 signalling could serve as a potential strategy to tackle therapy-resistant cancers.

GREB1 regulates PI3K/Akt signaling to control hormone-sensitive breast cancer proliferation

Over 70% of breast cancers express the estrogen receptor (ER) and depend on ER activity for survival and proliferation. While hormone therapies that target receptor activity are initially effective, patients invariably develop resistance which is often associated with activation of the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway. While the mechanism by which estrogen regulates proliferation is not fully understood, one gene target of ER, growth regulation by estrogen in breast cancer 1 (GREB1), is required for hormone-dependent proliferation. However, the molecular function by which GREB1 regulates proliferation is unknown. Herein, we validate that knockdown of GREB1 results in growth arrest and that exogenous GREB1 expression initiates senescence, suggesting that an optimal level of GREB1 expression is necessary for proliferation of breast cancer cells. Under both of these conditions, GREB1 is able to regulate signaling through the PI3K/Akt/mTOR pathway. GREB1 acts intrinsically through PI3K to regulate phosphatidylinositol (3,4,5)-triphosphate levels and Akt activity. Critically, growth suppression of estrogen-dependent breast cancer cells by GREB1 knockdown is rescued by expression of constitutively activated Akt. Together, these data identify a novel molecular function by which GREB1 regulates breast cancer proliferation through Akt activation and provides a mechanistic link between estrogen signaling and the PI3K pathway.

Integrative Systems Biology Approaches to Identify Potential Biomarkers and Pathways of Cervical Cancer

Nowadays, cervical cancer (CC) is treated as the leading cancer among women throughout the world. Despite effective vaccination and improved surgery and treatment, CC retains its fatality rate of about half of the infected population globally. The major screening biomarkers and therapeutic target identification have now become a global concern. In the present study, we have employed systems biology approaches to retrieve the potential biomarkers and pathways from transcriptomic profiling. Initially, we have identified 76 of each up-regulated and down-regulated gene from a total of 4643 differentially expressed genes. The up-regulatory genes mainly concentrate on immune-inflammatory responses, and the down-regulatory genes are on receptor binding and gamma-glutamyltransferase. The involved pathways associated with these genes were also assessed through pathway enrichment, and we mainly focused on different cancer pathways, immunoresponse, and cell cycle pathways. After the subsequent enrichment of these genes, we have identified 12 hub genes, which play a crucial role in CC and are verified by expression profile analysis. From our study, we have found that genes LILRB2 and CYBB play crucial roles in CC, as reported here for the first time. Furthermore, the survivability of the hub genes was also assessed, and among them, finally, CXCR4 has been identified as one of the most potential differentially expressed genes that might play a vital role in the survival of CC patients. Thus, CXCR4 could be used as a prognostic and/or diagnostic biomarker and a drug target for CC.

Circular RNA VRK1 facilitates pre-eclampsia progression via sponging miR-221-3P to regulate PTEN/Akt

Pre‐eclampsia (PE) is a worldwide pregnancy‐related disorder. It is mainly characterized by defect migration and invasion of trophoblast cells. Recently, circular RNAs (circRNAs) have been believed to play a vital role in PE. The expression patterns and the biological functions of circRNAs in PE remain elusive. Here, we performed a circRNA microarray to identify putative PE‐related circRNAs. Bioinformatics analyses were used to screen the circRNAs which have potential relationships with pre‐eclampsia, and we identified a novel circRNA (circVRK1) that was up‐regulated in PE placenta tissues. By using HTR‐8/SVneo cells, circVRK1 knockdown significantly enhanced cell migration and invasion abilities, as well as epithelial‐mesenchymal transition (EMT). Mechanistically, we found that circVRK1 and PTEN could function as the ceRNAs to miR‐221‐3p. Overexpression of miR‐221‐3p promoted cell migration, invasion and EMT via regulating PTEN. The cotransfection of miR‐221‐3p inhibitor or PTEN reversed the effect from circVRK1 knockdown. Moreover, the circVRK1/miR‐221‐3p/PTEN axis greatly regulated Akt phosphorylation. In general, circVRK1 suppresses trophoblast cell migration, invasion and EMT, by acting as a ceRNA to miR‐221‐3p to regulate PTEN, and further inhibit PI3K/Akt activation. The purpose of this paper is to open wide insights to investigate the onset of PE and provide new potential therapeutic targets in PE.

Recent advances in PTEN signalling axes in cancer

In over two decades since the discovery of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), nearly 18,000 publications have attempted to elucidate its functions and roles in normal physiology and disease. The frequent disruption of PTEN in cancer cells was a strong indication that it had critical roles in tumour suppression. Germline PTEN mutations have been identified in patients with heterogeneous tumour syndromic diseases, known as PTEN hamartoma tumour syndrome (PHTS), and in some individuals with autism spectrum disorders (ASD). Today we know that by limiting oncogenic signalling through the phosphoinositide 3-kinase (PI3K) pathway, PTEN governs a number of processes including survival, proliferation, energy metabolism, and cellular architecture. Some of the most exciting recent advances in the understanding of PTEN biology and signalling have revisited its unappreciated roles as a protein phosphatase, identified non-enzymatic scaffold functions, and unravelled its nuclear function. These discoveries are certain to provide a new perspective on its full tumour suppressor potential, and knowledge from this work will lead to new anti-cancer strategies that exploit PTEN biology. In this review, we will highlight some outstanding questions and some of the very latest advances in the understanding of the tumour suppressor PTEN.

E3 ubiquitin ligase RNF126 affects bladder cancer progression through regulation of PTEN stability

E3 ubiquitin ligase RNF126 (ring finger protein 126) is highly expressed in various cancers and strongly associated with tumorigenesis. However, its specific function in bladder cancer (BCa) is still debatable. Here, we found that RNF126 was significantly upregulated in BCa tissue by TCGA database, and our studies indicated that downregulation of RNF126 significantly inhibited cell proliferation and metastasis through the EGFR/PI3K/AKT signaling pathway in BCa cells. Furthermore, we identified PTEN, an inhibitor of the PI3K/AKT signaling pathway, as a novel substrate for RNF126. By co-immunoprecipitation assays, we proved that RNF126 directly interacts with PTEN. Predominantly, PTEN binds to the C-terminal containing the RING domain of RNF126. The in vivo ubiquitination assay showed that RNF126 specifically regulates PTEN stability through poly-ubiquitination. Furthermore, PTEN knockdown restored cell proliferation, metastasis, and tumor formation of BCa cells inhibited by RNF126 silencing in vitro and in vivo. In conclusion, these results identified RNF126 as an oncogene that functions through ubiquitination and degradation of PTEN in BCa.

Identification of MKRN1 as a second E3 ligase for Eag1 potassium channels reveals regulation via differential degradation

Mutations in the human gene encoding the neuron-specific Eag1 voltage-gated K⁺ channel are associated with neurodevelopmental diseases, indicating an important role of Eag1 during brain development. A disease-causing Eag1 mutation is linked to decreased protein stability that involves enhanced protein degradation by the E3 ubiquitin ligase cullin 7 (CUL7). The general mechanisms governing protein homeostasis of plasma membrane- and endoplasmic reticulum (ER)-localized Eag1 K⁺ channels, however, remain unclear. By using yeast two-hybrid screening, we identified another E3 ubiquitin ligase, makorin ring finger protein 1 (MKRN1), as a novel binding partner primarily interacting with the carboxyl-terminal region of Eag1. MKRN1 mainly interacts with ER-localized immature core-glycosylated, as well as nascent nonglycosylated, Eag1 proteins. MKRN1 promotes polyubiquitination and ER-associated proteasomal degradation of immature Eag1 proteins. Although both CUL7 and MKRN1 contribute to ER quality control of immature core-glycosylated Eag1 proteins, MKRN1, but not CUL7, associates with and promotes degradation of nascent, nonglycosylated Eag1 proteins at the ER. In direct contrast to the role of CUL7 in regulating both ER and peripheral quality controls of Eag1, MKRN1 is exclusively responsible for the early stage of Eag1 maturation at the ER. We further demonstrated that both CUL7 and MKRN1 contribute to protein quality control of additional disease-causing Eag1 mutants associated with defective protein homeostasis. Our data suggest that the presence of this dual ubiquitination system differentially maintains Eag1 protein homeostasis and may ensure efficient removal of disease-associated misfolded Eag1 mutant channels.

Potential Target miR-455 Delaying Arterial Stenosis Progression Through PTEN

Background: Vascular smooth muscle cells (VSMC) underwent phenotypic switching upon stimulation signals, and this is the prerequisite for their proliferation and migration. Previous work revealed that miR-455 may be involved in vascular stenosis. Thus, this study aimed to explore potential targets and mechanisms underlying the dynamics of miR-455 in vascular stenosis.

Methods: miR-455 and PTEN expression levels were studied in normal and stenosis tissue, as well as in VSMC in proliferation model. Manipulating miR-455 expression levels was achieved by transfection of either miR-455 mimic or inhibitor, and its effect on cell proliferation was studied by CCK-8 assay. Its effect on gene expression was studied by RT-qPCR and western blot. The expression regulation mechanism was studied by luciferase reporter system. Finally, the effect of miR-455 on regulating vascular stenosis was studied using a rat balloon-injured carotid artery stenosis model.

Results: High expression levels of miR-455 were detected in both stenosis arterial tissues and VSMC proliferation models. In contrast, the expression levels of PTEN were downregulated in these systems. miR-455 transfected VSMC showed higher levels of proliferation and decreased levels of PTEN. Potential binding sites between miR-455 and PTEN 3′UTR were predicted and confirmed. NF-kB p65 was found to bind directly on miR-455 promoter region and regulate its transcription. The progression of arterial stenosis could be delayed by introducing miR-455 antagomir.

Conclusions: The p65/miR-455/PTEN signaling pathway plays a crucial role in regulating VSMC proliferation and vascular stenosis. This indicated that miR-455 is a novel target that would help improve treatment outcomes in patients suffering from vascular stenosis.

Signaling pathways of EBV-induced oncogenesis

Epstein-Barr virus (EBV) is closely associated with multiple human cancers. EBV-associated cancers are mainly lymphomas derived from B cells and T cells (Hodgkin lymphoma, Burkitt lymphoma, NK/T-cell lymphoma, and posttransplant lymphoproliferative disorder (PTLD)) and carcinomas derived from epithelial cells (nasopharyngeal carcinoma and gastric carcinoma). EBV can induce oncogenesis in its host cell by activating various signaling pathways, such as nuclear factor-κB (NF-κB), phosphoinositide-3-kinase/protein kinase B (PI3K/AKT), Janus kinase/signal transducer and transcription activator (JAK/STAT), mitogen-activated protein kinase (MAPK), transforming growth factor-β (TGF-β), and Wnt/β-catenin, which are regulated by EBV-encoded proteins and noncoding RNA. In this review, we focus on the oncogenic roles of EBV that are mediated through the aforementioned signaling pathways.

Ubiquitin-proteasome system-targeted therapy for uveal melanoma: what is the evidence?

Uveal melanoma (UM) is a rare ocular tumor. The loss of BRCA1-associated protein 1 (BAP1) and the aberrant activation of G protein subunit alpha q (GNAQ)/G protein subunit alpha 11 (GNA11) contribute to the frequent metastasis of UM. Thus far, limited molecular-targeted therapies have been developed for the clinical treatment of UM. However, an increasing number of studies have revealed the close relationship between the ubiquitin proteasome system (UPS) and the malignancy of UM. UPS consists of a three-enzyme cascade, i.e. ubiquitin-activating enzymes (E1s); ubiquitin-conjugating enzymes (E2s); and ubiquitin-protein ligases (E3s), as well as 26S proteasome and deubiquitinases (DUBs), which work coordinately to dictate the fate of intracellular proteins through regulating ubiquitination, thus influencing cell viability. Due to the critical role of UPS in tumors, we here provide an overview of the crosstalk between UPS and the malignancy of UM, discuss the current UPS-targeted therapies in UM and highlight its potential in developing novel regimens for UM.

Celecoxib induces apoptosis through Akt inhibition in 5-fluorouracil-resistant gastric cancer cells

Gastric cancer is the fifth leading cause of cancer and a global public health problem. 5-Fluorouracil (5-FU) is the primary drug chosen for the treatment of advanced gastric cancer, but acquired cancer drug resistance limits its effectiveness and clinical use. Proliferation assays showed that a gastric carcinoma cell line, AGS and 5-FU-resistant AGS cells (AGS FR) treated with 3-100 μM 5-FU for 48 h or 72 h showed different sensitivities to 5-FU. Immunoblot assay demonstrated that AGS FR cells expressed more COX-2 and PGE₂-cognated receptor EP2 than AGS cells. AGS FR cells considerably produced PGE₂ than AGS upon stimulation with 5-FU. These results suggest that COX-2 expression is associated with 5-FU resistance. Unlike AGS FR cells, AGS cells showed increased levels of both cleaved caspase-3 and Bax following 5-FU treatment. Treatment of cells with the COX-2 selective inhibitor celecoxib induced cell death of AGS FR cells in a time- and concentration-dependent manner. FACS analysis showed that celecoxib at high doses caused apoptotic cell death, demonstrating a concentration-dependent increase in the cell populations undergoing early apoptosis and late apoptosis. This apoptotic induction was strongly supported by the expression profiles of apoptosis- and survival-associated proteins in response to celecoxib; pro-apoptotic cellular proteins increased while expressions of COX-2 and p-Akt were downregulated in a concentration-dependent manner. An increase in PTEN expression was accompanied with downregulation of p-Akt. Based on the data that downregulation of COX-2 was correlated with the concentrations of celecoxib, COX-2 may play a key role in celecoxib-induced cell death of AGS FR cells. Butaprost, the EP2 agonist, promoted proliferative activity of AGS FR cells in a concentration-dependent manner compared with AGS cells. In cells exposed to butaprost, expressions of COX-2 and p-Akt were increased in a concentration-dependent manner with concomitantly reduced PTEN levels. Taken together, 5-FU-resistance in gastric cancer is correlated with COX-2 expression, and therefore the selective inhibition of COX-2 leads to suppression of cell proliferation of AGS FR cells. Modulation of COX-2 expression and its catalytic activity may be a potential therapeutic strategy to overcome 5-FU-resistant gastric cancer.

Ubiquitin Ligase Activities of WWP1 Germline Variants K740N and N745S

WWP1 is an E3 ubiquitin ligase that has been reported to target the tumor suppressor lipid phosphatase PTEN. K740N and N745S are recently identified germline variants of WWP1 that have been linked to PTEN-associated cancers [Lee, Y. R., et al. (2020) N. Engl. J. Med.]. These WWP1 variants have been suggested to release WWP1 from its native autoinhibited state, thereby promoting enhanced PTEN ubiquitination as a mechanism for driving cancer. Using purified proteins and in vitro enzymatic assays, we investigate the possibility that K740N and N745S WWP1 possess enhanced ubiquitin ligase activity and demonstrate that these variants are similar to the wild type (WT) in both autoubiquitination and PTEN ubiquitination. Furthermore, K740N and N745S WWP1 show dependencies similar to those of WT in terms of allosteric activation by an engineered ubiquitin variant, upstream E2 concentration, and substrate ubiquitin concentration. Transfected WWP1 WT and mutants demonstrate comparable effects on cellular PTEN levels. These findings challenge the idea that K740N and N745S WWP1 variants promote cancer by enhanced PTEN ubiquitination.

BAP1 suppresses prostate cancer progression by deubiquitinating and stabilizing PTEN

Deubiquitinase BAP1 is an important tumor suppressor in several malignancies, but its functions and critical substrates in prostate cancer (PCa) remain unclear. Here, we report that the mRNA and protein expression levels of BAP1 are downregulated in clinical PCa specimens. BAP1 can physically bind to and deubiquitinate PTEN, which inhibits the ubiquitination-mediated degradation of PTEN and thus stabilizes PTEN protein. Ectopically expressed BAP1 in PCa cells increases PTEN protein level and subsequently inhibits the AKT signaling pathway, thus suppressing PCa progression. Conversely, knockdown of BAP1 in PCa cells leads to the decrease in PTEN protein level and the activation of the Akt signaling pathway, therefore promoting malignant transformation and cancer metastasis. However, these can be reversed by the re-expression of PTEN. More importantly, we found that BAP1 protein level positively correlates with PTEN in a substantial fraction of human cancers. These findings demonstrate that BAP1 is an important deubiquitinase of PTEN for its stability and the BAP1-PTEN signaling axis plays a crucial role in tumor suppression.

Role of CCCH-Type Zinc Finger Proteins in Human Adenovirus Infections

The zinc finger proteins make up a significant part of the proteome and perform a huge variety of functions in the cell. The CCCH-type zinc finger proteins have gained attention due to their unusual ability to interact with RNA and thereby control different steps of RNA metabolism. Since virus infections interfere with RNA metabolism, dynamic changes in the CCCH-type zinc finger proteins and virus replication are expected to happen. In the present review, we will discuss how three CCCH-type zinc finger proteins, ZC3H11A, MKRN1, and U2AF1, interfere with human adenovirus replication. We will summarize the functions of these three cellular proteins and focus on their potential pro- or anti-viral activities during a lytic human adenovirus infection.

Upregulated microRNA-126 induces apoptosis of dental pulp stem cell via mediating PTEN-regulated Akt activation

INTRODUCTION

Human dental pulp stem cells (DPSCs) have potential applications in regenerative medicine. The molecular mechanisms underlying DPSCs viability and apoptosis are not completely understood. Here, we investigated the role of miR-126 in DPSCs viability and apoptosis.

MATERIAL AND METHODS

Senescent DPSCs were compared with early passage DPSCs. real-time PCR and microARRAY were performed to identify the differential expression of miR-126, and western blot was performed to detect the expression of PTEN. MTT assay was utilized to reveal the proliferative rate of both senescent and early passage DPSCs. Flow cytometry was used to examine the apoptotic rate of DPSCs. Dual-luciferase reporter assay was carried out to detect the interaction of miR-126 and PTEN.

RESULTS

Senescent DPSCs showed a high level of apoptosis. Further study showed that miR-126 is upregulated in senescent DPSCs and its overexpression in early passaged DPSCs induced apoptosis. Phosphatase and tensin homolog gene (PTEN) was identified as a target of miR-126. PTEN was downregulated in senescent DPSCs, whereas miR-126 inhibition upregulated PTEN level, and subsequently activated Akt pathway and suppressed the apoptotic phenotype of senescent DPSCs. In addition, PTEN overexpression rescued apoptosis of DPSCs at later stage.

CONCLUSION

Our results demonstrate that the miR-126-PTEN-Akt axis plays a key role in the regulation of DPSCs apoptosis and provide a candidate target to improve the functional and therapeutic potential of DPSCs.

Palmitic acid negatively regulates tumor suppressor PTEN through T366 phosphorylation and protein degradation

Chronic elevated free fatty (FFA) levels are linked to metabolic disorders and tumorigenesis. However, the molecular mechanism by which FFAs induce cancer remains poorly understood. Here, we show that the tumor suppressor PTEN protein levels were decreased in high fat diet (HFD) fed mice. As palmitic acid (PA, C16:0) showed a significant increase in the HFD fed mice, we further investigated its role in PTEN down regulation. Our studies revealed that exposure of cells to high doses of PA induced mTOR/S6K-mediated phosphorylation of PTEN at T366. The phosphorylation subsequently enhanced the interaction of PTEN with the E3 ubiquitin ligase WW domain-containing protein 2 (WWP2), which promoted polyubiquitination of PTEN and protein degradation. Consistent with PTEN degradation, exposure of cells to increased concentrations of PA also promoted PTEN-mediated AKT activation and cell proliferation. Significantly, a higher level of S6K activation, PTEN T366 phosphorylation, and AKT activation were also observed in the livers of the HFD fed mice. These results provide a molecular mechanism by which a HFD and elevated PA regulate cell proliferation through inactivation of tumor suppressor PTEN.