PTEN Physically Interacts with and Regulates E2F1-mediated Transcription in Lung Cancer

The prognostic impact of pathogenic stromal cell-associated genes in lung adenocarcinoma

BACKGROUND

Lung adenocarcinoma (LUAD) stands as the most prevalent subtype among lung cancers. Interactions between stromal and cancer cells influence tumor growth, invasion, and metastasis. However, the regulatory mechanisms of stromal cells in the lung adenocarcinoma tumor microenvironment remain unclear. This study seeks to elucidate the regulatory connections among critical pathogenic genes and their associated expression variations within distinct stromal cell subtypes.

METHOD

Analysis and investigation were conducted on a total of 114,019 single-cell RNA data and 346 The Cancer Genome Atlas (TCGA) LUAD-related samples using bioinformatics and statistical algorithms. Differential gene expression analysis was performed for tumor samples and controls, followed by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Differential genes between stromal cells and other cell clusters were identified and intersected with the differential genes from TCGA. We employed a combination of LASSO regression and multivariable Cox regression to identify the ultimate set of pathogenic gene. Survival models were trained to predict the relationship between patient survival and these pathogenic genes. Analysis of transcription factor (TF) cell specificity and pseudotime trajectories within stromal cell subpopulations revealed that vascular endothelial cells (ECs) and matrix cancer-associated fibroblasts (CAFs) are key in regulation of the prognosis-associated genes CAV2, COL1A1, TIMP1, ETS2, AKAP12, ID1 and COL1A2.

RESULTS

Seven pathogenic genes associated with LUAD in stromal cells were identified and used to develop a survival model. High expression of these genes is linked to a greater risk of poor survival. Stromal cells were categorized into eight subtypes and one unannotated cluster. Mesothelial cells, vascular endothelial cells (ECs), and matrix cancer-associated fibroblasts (CAFs) showed cell-specific regulation of the pathogenic genes.

CONCLUSIONS

The seven disease-causing genes in vascular ECs and matrix CAFs can be used to detect the survival status of LUAD patients, providing new directions for future targeted drug design.

PTEN regulates expression of its pseudogene in glioblastoma cells in DNA methylation-dependent manner

Glioblastoma (GBM) is the most aggressive and frequent type of primary brain cancer in adult patients. One of the key molecular features associated with GBM pathogenesis is the dysfunction of PTEN oncosuppressor. In addition to PTEN gene, humans and several primates possess processed PTEN pseudogene (PTENP1) that gives rise to long non-coding RNA lncPTENP1-S. Regulation and functions of PTEN and PTENP1 are highly interconnected, however, the exact molecular mechanism of how these two genes affect each other remains unclear. Here, we analyzed the methylation level of the CpG islands (CpGIs) in the promoter regions of PTEN and PTENP1 in patient-derived GBM neurospheres. We found that increased PTEN methylation corelates with decreased PTEN mRNA level. Unexpectedly, we showed the opposite trend for PTENP1. Using targeted methylation and demethylation of PTENP1 CpGI, we demonstrated that DNA methylation increases lncPTENP1-S expression in the presence of wild type PTEN protein but decreases lncPTENP1-S expression if PTEN protein is absent. Further experiments revealed that PTEN protein binds to PTENP1 promoter region and inhibits lncPTENP1-S expression if its CpGI is demethylated. Interestingly, we did not detect any effect of lncPTENP1-S on the level of PTEN mRNA, indicating that in GBM cells PTENP1 is a downstream target of PTEN rather than its upstream regulator. Finally, we studied the functions of lncPTENP1-S and demonstrated that it plays a pro-oncogenic role in GBM cells by upregulating the expression of cancer stem cell markers and decreasing cell adhesion.

The E3 ubiquitin ligase CHIP drives monoubiquitylation-mediated nuclear import of the tumor suppressor PTEN

Monoubiquitylation is a principal mechanism driving nuclear translocation of the protein PTEN (phosphatase and tensin homolog deleted on chromosome ten). In this study, we describe a novel mechanism wherein the protein CHIP (C-terminus of Hsc70-interacting protein) mediates PTEN monoubiquitylation, leading to its nuclear import. Western blot analysis revealed a rise in both nuclear and total cellular PTEN levels under monoubiquitylation-promoting conditions, an effect that was abrogated by silencing CHIP expression. We established time-point kinetics of CHIP-mediated nuclear translocation of PTEN using immunocytochemistry and identified a role of karyopherin α1 (KPNA1) in facilitating nuclear transport of monoubiquitylated PTEN. We further established a direct interaction between CHIP and PTEN inside the nucleus, with CHIP participating in either polyubiquitylation or monoubiquitylation of nuclear PTEN. Finally, we showed that oxidative stress enhanced CHIP-mediated nuclear import of PTEN, which resulted in increased apoptosis, and decreased cell viability and proliferation, whereas CHIP knockdown counteracted these effects. To the best of our knowledge, this is the first report elucidating non-canonical roles for CHIP on PTEN, which we establish here as a nuclear interacting partner of CHIP.

E2F1‑mediated RAB34 upregulation accelerates the proliferation and inhibits the cell cycle arrest and apoptosis of acute myeloid leukemia cells

Acute myeloid leukemia (AML) is a malignant disease that is mainly arisen from myeloid stem/progenitor cells. The pathogenesis of AML is complex. Ras-related protein member RAS oncogene GTPases (RAB) 34 protein has been reported to serve an important role in the development of cancer. However, to the best of our knowledge, the role of RAB34 in AML has not been previously reported. The GEPIA database was used to predict the expression levels of RAB34 in patients with AML. Reverse transcription-quantitative PCR and western blotting were used to detect the expression of RAB34 in AML cell lines. Cell transfection with short hairpin (sh)RNAs targeting RAB34 was used to interfere with RAB34 expression. Cell Counting Kit-8 and 5-ethynyl-2'-deoxyuridine staining were used to measure cell proliferation. Flow cytometry was used to investigate cell cycle distribution and apoptosis. Western blotting was used to assess the protein expression levels of RAB34 and E2F transcription factor 1 (E2F1), and cell cycle- and apoptosis-associated proteins, including Bcl-2, Bax, CDK4, CDK8 and cyclin D1. The potential binding between E2F1 and RAB34 was then verified by luciferase reporter and chromatin immunoprecipitation assays. Subsequently, cells were co-transfected with RAB34 shRNA and the E2F1 overexpression plasmid before cell proliferation, cell cycle and apoptosis were analyzed further. The expression of RAB34 was found to be significantly increased in AML cell lines. Knocking down RAB34 expression in AML cells was found to significantly inhibit cell proliferation, induce cell cycle arrest and promote apoptosis. E2F1 activated the transcription of RAB34 and E2F1 elevation reversed the impacts of RAB34 silencing on cell proliferation, cell cycle and apoptosis in AML. Therefore, these findings suggest that E2F1-mediated RAB34 upregulation may accelerate the malignant progression of AML.

Significance of RB Loss in Unlocking Phenotypic Plasticity in Advanced Cancers

Cancer cells can undergo plasticity in response to environmental stimuli or under selective therapeutic pressures that result in changes in phenotype. This complex phenomenon of phenotypic plasticity is now recognized as a hallmark of cancer. Lineage plasticity is often associated with loss of dependence on the original oncogenic driver and is facilitated, in part, by underlying genomic and epigenetic alterations. Understanding the molecular drivers of cancer plasticity is critical for the development of novel therapeutic strategies. The retinoblastoma gene RB1 (encoding RB) is the first tumor suppressor gene to be discovered and has a well-described role in cell-cycle regulation. RB is also involved in diverse cellular functions beyond cell cycle including differentiation. Here, we describe the emerging role of RB loss in unlocking cancer phenotypic plasticity and driving therapy resistance across cancer types. We highlight parallels in cancer with the noncanonical role of RB that is critical for normal development and lineage specification, and the downstream consequences of RB loss including epigenetic reprogramming and chromatin reorganization that can lead to changes in lineage program. Finally, we discuss potential therapeutic approaches geared toward RB loss cancers undergoing lineage reprogramming.

Identification of NLE1/CDK1 axis as key regulator in the development and progression of non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the most common pathological type of lung cancer, which is a severer threaten to human health because of its extremely high morbidity and mortality. In this study, the role of Notchless homolog 1 (NLE1) in the development of NSCLC was investigated and the underlying mechanism was explored. The outcomes showed that NLE1 expression is significantly higher in tumor tissues than normal tissues, and is correlated with the pathological stage. The regulation of NSCLC development by NLE1 was also visualized by the in vitro and in vivo loss-of-function studies, which indicated the inhibition of cell growth and migration, as well as enhancement of cell apoptosis on condition of NLE1 knockdown. As for the mechanism, it was demonstrated that NLE1 may execute its tumor-regulating function through activating E2F1-mediated transcription of CDK1, and PI3K/Akt signaling pathway was also supposed as a downstream of NLE1 in the regulation of NSCLC. Both CDK1 overexpression and treatment of Akt pathway activator could reverse the NLE1 knockdown induced NSCLC inhibition to some extent. In conclusion, this study identified NLE1 as a novel tumor promotor in the development and progression of NSCLC, which may be a potential therapeutic target in the treatment of NSCLC.

Nuclear PTEN's Functions in Suppressing Tumorigenesis: Implications for Rare Cancers

Phosphatase and tensin homolog (PTEN) encodes a tumor-suppressive phosphatase with both lipid and protein phosphatase activity. The tumor-suppressive functions of PTEN are lost through a variety of mechanisms across a wide spectrum of human malignancies, including several rare cancers that affect pediatric and adult populations. Originally discovered and characterized as a negative regulator of the cytoplasmic, pro-oncogenic phosphoinositide-3-kinase (PI3K) pathway, PTEN is also localized to the nucleus where it can exert tumor-suppressive functions in a PI3K pathway-independent manner. Cancers can usurp the tumor-suppressive functions of PTEN to promote oncogenesis by disrupting homeostatic subcellular PTEN localization. The objective of this review is to describe the changes seen in PTEN subcellular localization during tumorigenesis, how PTEN enters the nucleus, and the spectrum of impacts and consequences arising from disrupted PTEN nuclear localization on tumor promotion. This review will highlight the immediate need in understanding not only the cytoplasmic but also the nuclear functions of PTEN to gain more complete insights into how important PTEN is in preventing human cancers.

PTEN phosphatase inhibits metastasis by negatively regulating the Entpd5/IGF1R pathway through ATF6

PTEN encodes a tumor suppressor with lipid and protein phosphatase activities whose dysfunction has been implicated in melanomagenesis; less is known about how its phosphatases regulate melanoma metastasis. We demonstrate that PTEN expression negatively correlates with metastatic progression in human melanoma samples and a PTEN-deficient mouse melanoma model. Wildtype PTEN expression inhibited melanoma cell invasiveness and metastasis in a dose-dependent manner, behaviors that specifically required PTEN protein phosphatase activity. PTEN phosphatase activity regulated metastasis through Entpd5. Entpd5 knockdown reduced metastasis and IGF1R levels while promoting ER stress. In contrast, Entpd5 overexpression promoted metastasis and enhanced IGF1R levels while reducing ER stress. Moreover, Entpd5 expression was regulated by the ER stress sensor ATF6. Altogether, our data indicate that PTEN phosphatase activity inhibits metastasis by negatively regulating the Entpd5/IGF1R pathway through ATF6, thereby identifying novel candidate therapeutic targets for the treatment of PTEN mutant melanoma.

Advanced Platelet-Rich Fibrin Extract Treatment Promotes the Proliferation and Differentiation of Human Adipose-Derived Mesenchymal Stem Cells through Activation of Tryptophan Metabolism

BACKGROUND

Advanced platelet-rich fibrin extract (APRFE) contains a high concentration of various cytokines that are helpful for improving stem cells repair function.

OBJECTIVE

However, the underlying mechanism of APRFE improving stem cell repairing is not clear.

METHODS

We produced APRFE by centrifuging fresh peripheral blood samples and isolated and identified human adipose-derived mesenchymal stem cells (ADMSCs). The abundance of cytokines contained in APRFE was detected by the Enzyme-linked immunosorbent assay (ELISA). The ADMSCs treated with or without APRFE were collected for transcriptome sequencing.

RESULTS

Based on the sequencing data, the expression profiles were contracted. The differentially expressed genes and lncRNA (DEGs and DElncRNAs) were obtained using for the differential expression analysis. The lncRNA-miRNA-mRNA network was constructed based on the miRNet database. The further enrichment analysis results showed that the biological functions were mainly related to proliferation, differentiation, and cell-cell function. To explore the role of APRFE, the protein-protein interaction network was constructed among the cytokines included in APRFE and DEGs. Furthermore, we constructed the global regulatory network based on the RNAInter and TRRUST database. The pathways in the global regulatory network were considered as the core pathways. We found that the DEGs in the core pathways were associated with stemness scores.

CONCLUSION

In summary, we predicted that APRFE activated three pathways (tryptophan metabolism, mTOR signaling pathway, and adipocytokine signaling) to promote the proliferation and differentiation of ADMSCs. The finding may be helpful for guiding the application of ADMSCs in the clinic.

Structural and Dynamic Effects of PTEN C-Terminal Tail Phosphorylation

The phosphatase and tensin homologue deleted on chromosome 10 (PTEN) tumor suppressor gene encodes a tightly regulated dual-specificity phosphatase that serves as the master regulator of PI3K/AKT/mTOR signaling. The carboxy-terminal tail (CTT) is key to regulation and harbors multiple phosphorylation sites (Ser/Thr residues 380-385). CTT phosphorylation suppresses the phosphatase activity by inducing a stable, closed conformation. However, little is known about the mechanisms of phosphorylation-induced CTT-deactivation dynamics. Using explicit solvent microsecond molecular dynamics simulations, we show that CTT phosphorylation leads to a partially collapsed conformation, which alters the secondary structure of PTEN and induces long-range conformational rearrangements that encompass the active site. The active site rearrangements prevent localization of PTEN to the membrane, precluding lipid phosphatase activity. Notably, we have identified phosphorylation-induced allosteric coupling between the interdomain region and a hydrophobic site neighboring the active site in the phosphatase domain. Collectively, the results provide a mechanistic understanding of CTT phosphorylation dynamics and reveal potential druggable allosteric sites in a previously believed clinically undruggable protein.

Comprehensive analysis to identify a novel PTEN-associated ceRNA regulatory network as a prognostic biomarker for lung adenocarcinoma

Lung adenocarcinoma (LUAD) is one of the most prevalent forms of lung cancer. Competitive endogenous RNA (ceRNA) plays an important role in the pathogenesis of lung cancer. Phosphatase and tensin homolog (PTEN) is one of the most frequently deleted tumour suppressor genes in LUAD. The present study aimed to identify a novel PTEN-associated-ceRNA regulatory network and identify potential prognostic markers associated with LUAD. Transcriptome sequencing profiles of 533 patients with LUAD were obtained from TCGA database, and differentially expressed genes (DEGs) were screened in LUAD samples with PTEN high- (PTENhigh) and low- (PTENlow) expression. Eventually, an important PTEN-related marker was identified, namely, the LINC00460/miR-150-3p axis. Furthermore, the predicted target genes (EME1/HNRNPAB/PLAUR/SEMA3A) were closely related to overall survival and prognosis. The LINC00460/miR-150-3p axis was identified as a clinical prognostic factor through Cox regression analysis. Methylation analyses suggested that abnormal regulation of the predicted target genes might be caused by hypomethylation. Furthermore, immune infiltration analysis showed that the LINC00460/miR-150-3p axis could alter the levels of immune infiltration in the tumour immune microenvironment, and promote the clinical progression of LUAD. To specifically induce PTEN deletion in the lungs, we constructed an STP mouse model (SFTPC-rtTA/tetO-cre/Ptenflox/+). Quantitative PCR (qPCR) and immunohistochemical (IHC) analysis were used to detect predicted target genes. Therefore, we revealed that the PTEN-related LINC00460/miR-150-3p axis based on ceRNA mechanism plays an important role in the development of LUAD and provides a new direction and theoretical basis for its targeted therapy.

Circular RNA hsa_circ_0000317 inhibits non-small cell lung cancer progression through regulating microRNA-494-3p/phosphatase and tensin homolog deleted on chromosome 10 axis

BACKGROUND

Circular RNA (circRNA), a group of non-coding RNA, is pivotal in the progression of various cancers, including Non-Small Cell Lung Cancer (NSCLC). Some circRNAs have been reported to be implicated in the progression of NSCLC, however, the function and molecular mechanism of hsa_circ_0000317 (circ_0000317) in NSCLC have not been fully understood.

METHODS

The significantly differentially expressed circRNA in NSCLC tissues, circ_0000317, was screened out by microarray. Circ_0000317, microRNA(miR)-494-3p and Phosphatase and Tensin Homolog Deleted on Chromosome 10 (PTEN) expressions in NSCLC tissues were respectively probed by quantitative real-time polymerase chain reaction and western blot assay. MTT and Transwell assays were adopted to examine the growth, migration, and invasion of NSCLC cells. Bioinformatics, luciferase reporter gene assay, RNA immunoprecipitation, and RNA pull-down assay were conducted to probe the relationships among circ_0000317, miR-494-3p, and PTEN.

RESULTS

Circ_0000317 expression level was reduced in NSCLC tissues and cell lines. Circ_0000317 expression in NSCLC patients was associated with TNM stage and lymphatic metastasis. Circ_0000317 overexpression restrained the proliferation, migration, and invasion of NSCLC cells, but co-transfection of miR-494-3p mimics partially reversed this effect. In addition, circ_0000317, was identified as a competitive endogenous RNA, which could sponge miR-494-3p to increase PTEN expression and activate PI3K/AKT pathway.

CONCLUSION

Circ_0000317, inhibits NSCLC progression via modulating miR-494-3p/PTEN/PI3K/AKT pathway.

Procollagen-lysine, 2-oxoglutarate 5-dioxygenase 1 increases cellular proliferation and colony formation capacity in lung cancer via activation of E2F transcription factor 1

Procollagen-lysine, 2-oxoglutarate 5-dioxygenase 1 (PLOD1) is an enzyme that catalyzes the hydroxylation of lysyl residues in collagen-like peptides, and is responsible for the stability of intermolecular crosslinks. High PLOD1 mRNA levels have been determined to be prognostically significant in numerous human malignancies. The objective of the present study was to elucidate the pathological mechanism of PLOD1 in lung cancer. The expression status and prognostic value of PLOD1 in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSA) were investigated using Gene Expression Profiling Interactive Analysis (GEPIA). Cell Counting Kit 8 and colony formation assays were performed to assess the impact of PLOD1 depletion and overexpression on the proliferation and colony formation abilities of the A549 lung cancer cell line. Luciferase reporter assays were used to clarify whether E2F transcription factor 1 (E2F1) was a downstream target of PLOD1 in lung cancer. Finally, the correlations between PLOD1 expression and a typical central downstream effector molecule of E2F1 signaling were determined using cBioportal. The GEPIA datasets revealed that PLOD1 mRNA levels were upregulated in LUAD and LUSC samples. Furthermore, the overexpression of PLOD1 promoted cancer cell proliferation and colony formation in vitro, while PLOD1-knockout produced the opposite effect. Notably, PLOD1 markedly induced the transcriptional activity of E2F1. Additionally, the expression of PLOD1 was significantly correlated with that of H2A histone family member X. In conclusion, the findings of the present study indicate that PLOD1 promoted lung cancer through E2F1 activation, and proposed a rationale for targeting the PLOD1/E2F1 axis to treat lung cancer.

Role of succinylation modification in thyroid cancer and breast cancer

The incidence of thyroid cancer and breast cancer is increasing year by year, and the specific pathogenesis is unclear. Posttranslational modifications constitute an important regulatory mechanism that affects the function of almost all proteins, are essential for a diverse and well-functioning proteome and can integrate metabolism with physiological and pathological processes. In recent years, posttranslational modifications, which mainly include metabolic enzyme-mediated protein posttranslational modifications, such as methylation, phosphorylation, acetylation and succinylation, have become a research hotspot. Among these modifications, lysine succinylation is a newly discovered broad-spectrum, dynamic, non-enzymatic protein post-translational modification, and it plays an important regulatory role in a variety of tumors. Studies have shown that succinylation can affect the synthesis of thyroid hormones, and the regulation of this post-translational modification can inhibit the apoptosis and migration of thyroid cancer cell lines, and promote breast cancer cell proliferation, DNA damage repair and autophagy-related regulation. However, the specific regulatory mechanism of succinylation in thyroid cancer and breast cancer is currently unclear. Therefore, this article mainly reviews the research progress of succinylation modification in thyroid cancer and breast cancer. It is expected to provide new directions and targets for the prevention and treatment of thyroid cancer and breast cancer.

Non-canonical function of nuclear PTEN and its implication on tumorigenesis

Suppression of genomic instability is the key to prevent tumor development. PTEN is a unique tumor suppressor protein having both lipid and protein phosphatase activities. Interestingly though it is a cytoplasmic protein, but a significant pool of PTEN can also be localized in nucleus. The function of cytoplasmic PTEN is well defined and extensively studied in various literatures focusing mainly on the negative regulation of oncogenic PI-3Kinase-AKT pathway but functional regulation of nuclear PTEN is less defined and therefore it is a fascinating subject of research in cancer biology. Post-translation modulation of PTEN such as phosphorylation, sumorylation, acetylation and methylation also regulates its cellular localization, protein-protein association and catalytic function. Loss or mutation in PTEN is associated with the development of tumors in various tissues from the brain to prostate. Here we have summarized the role of nuclear PTEN and its epigenetic modulation in various DNA metabolic pathways, for example, DNA damage response, DNA repair, DNA replication, DNA segregation etc. Further, pathways involved in nuclear PTEN degradation are also discussed. Additionally, we also emphasize probable potential targets associated with PTEN pathway for chemotherapeutic purpose.

G protein gamma 7 suppresses progression of lung adenocarcinoma by inhibiting E2F transcription factor 1

G protein gamma 7 (GNG7) has been found to be aberrantly expressed in some kinds of malignant tumors. In this study, we mainly discuss the antitumor role of it in lung adenocarcinoma (LUAD) cells. Protein levels of GNG7 in LUAD tissues were measured by western blot and immunohistochemical analysis. Cell proliferation, invasion and migration were detected by CCK-8 assay, 5-ethynyl-2'-deoxyuridine (EdU), and Transwell assay. In our study, GNG7 was down-regulated in LUAD, which significantly correlated with survival of LUAD patients. Functional experiments revealed that GNG7 significantly inhibited LUAD cell proliferation, migration, and invasion in vitro and E2F1 overexpression reversed these properties. GNG7 suppressed xenograft tumorigenesis in nude mice models in vivo. In conclusion, GNG7 functions as a tumor suppressor in LUAD cells through inhibiting E2F1.

Inhibition Sequence of miR-205 Hinders the Cell Proliferation and Migration of Lung Cancer Cells by Regulating PETN-Mediated PI3K/AKT Signal Pathway

The aim of this study was to identify the pro-tumor role of miR-205 in patients with lung cancer (LC) on the cell proliferation and migration through regulating PTEN-mediated PI3K/AKT signal pathway. Paired cancer tissues and adjacent tissues were collected from 107 LC patients who received treatment in Jinan Central hospital. In addition, the purchased LC cell lines were transfected into HCC827 cell line to observe and compare the biological behaviors. Compared with adjacent tissues, miR-205 was statistically higher in LC tissues, while PTEN was notably lower (P < 0.05). Inhibition of miR-205 not only suppressed cell proliferation, migration and invasion, increased apoptosis rate, but regulated epithelial mesenchymal transformation (EMT)-related proteins. Likewise, overexpression of PETN played the same role as that of miR-205 inhibition sequence. Inhibited miR-205 or PTEN overexpression brought dramatically decreased PI3K and p-Akt. The relationship between miR-205 and PTEN was verified through the biological prediction website and luciferase reporter. Co-transfection experiments revealed that after cotransfection of miR-205 inhibitor and si-PETN, the cell proliferation and invasion showed no marked difference between cotransfection group and NC group. MiR-205 is involved in LC cell proliferation and migration by regulating PETN-mediated PI3K/AKT signal pathway, which may be a feasible treatment target for LC in clinical practice.

Neddylation of PTEN regulates its nuclear import and promotes tumor development

PTEN tumor suppressor opposes the PI3K/Akt signaling pathway in the cytoplasm and maintains chromosomal integrity in the nucleus. Nucleus-cytoplasm shuttling of PTEN is regulated by ubiquitylation, SUMOylation and phosphorylation, and nuclear PTEN has been proposed to exhibit tumor-suppressive functions. Here we show that PTEN is conjugated by Nedd8 under high glucose conditions, which induces PTEN nuclear import without effects on PTEN stability. PTEN neddylation is promoted by the XIAP ligase and removed by the NEDP1 deneddylase. We identify Lys197 and Lys402 as major neddylation sites on PTEN. Neddylated PTEN accumulates predominantly in the nucleus and promotes rather than suppresses cell proliferation and metabolism. The nuclear neddylated PTEN dephosphorylates the fatty acid synthase (FASN) protein, inhibits the TRIM21-mediated ubiquitylation and degradation of FASN, and then promotes de novo fatty acid synthesis. In human breast cancer tissues, neddylated PTEN correlates with tumor progression and poor prognosis. Therefore, we demonstrate a previously unidentified pool of nuclear PTEN in the Nedd8-conjugated form and an unexpected tumor-promoting role of neddylated PTEN.

WGCNA reveals key gene modules regulated by the combined treatment of colon cancer with PHY906 and CPT11

Irinotecan (CPT11) is one of the most effective drugs for treating colon cancer, but its severe side effects limit its application. Recently, a traditional Chinese herbal preparation, named PHY906, has been proved to be effective for improving therapeutic effect and reducing side effects of CPT11. The aim of the present study was to provide novel insight to understand the molecular mechanism underlying PHY906-CPT11 intervention of colon cancer. Based on the GSE25192 dataset, for different three treatments (PHY906, CPT11, and PHY906-CPT11), we screened out differentially expressed genes (DEGs) and constructed a co-expression network by weighted gene co-expression network analysis (WGCNA) to identify hub genes. The key genes of the three treatments were obtained by merging the DEGs and hub genes. For the PHY906-CPT11 treatment, a total of 18 key genes including Eif4e, Prr15, Anxa2, Ddx5, Tardbp, Skint5, Prss12 and Hnrnpa3, were identified. The results of functional enrichment analysis indicated that the key genes associated with PHY906-CPT11 treatment were mainly enriched in ‘superoxide anion generation’ and ‘complement and coagulation cascades’. Finally, we validated the key genes by Gene Expression Profiling Interactive Analysis (GEPIA) and RT-PCR analysis, the results indicated that EIF4E, PRR15, ANXA2, HNRNPA3, NCF1, C3AR1, PFDN2, RGS10, GNG11, and TMSB4X might play an important role in the treatment of colon cancer with PHY906-CPT11. In conclusion, a total of 18 key genes were identified in the present study. These genes showed strong correlation with PHY906-CPT11 treatment in colon cancer, which may help elucidate the underlying molecular mechanism of PHY906-CPT11 treatment in colon cancer.

TRIM37 Mediates Chemoresistance and Maintenance of Stemness in Pancreatic Cancer Cells via Ubiquitination of PTEN and Activation of the AKT-GSK-3β-β-Catenin Signaling Pathway

Purpose

The tripartite motif-containing family member TRIM37 is involved in a number of important biological and pathological processes, and it has recently been shown to be an essential regulator of protein ubiquitination and a contributor to tumorigenesis. We previously showed that TRIM37 is overexpressed in and promotes the proliferation and invasion of pancreatic cancer (PC).

Methods

Sphere formation, flow cytometric, qRT-PCR, western blot, colony formation, EdU incorporation, mouse xenograft model, TUNEL and IHC assays were performed to detect the role of TRIM37 in stemness and chemoresistance of PC in vitro and in vivo. Bioinformatics analysis and dual-luciferase reporter assays were used to determine which intracellular pathways might mediate the effects of TRIM37 in PC cells. Immunofluorescent(IF) staining, co-immunoprecipitation(CO-IP), protein stability and ubiquitination assays were performed to investigate the relationship between TRIM37 and PTEN.

Results

TRIM37 modulates the ubiquitination and degradation of the tumor suppressor phosphatase and tensin homolog (PTEN), which negatively regulates the AKT–GSK-3β–β-catenin signaling pathway, thereby sustaining aberrant activation of PC cells. High expression of TRIM37 combined with low expression of PTEN correlates with poor survival of PC patients.

Conclusions

Collectively, our results suggest that inhibition of the TRIM37–AKT–GSK-3β–β-catenin axis may be a promising strategy for treatment of PC.

Phosphatase and Tensin Homolog (PTEN) of Japanese Flounder-Its Regulation by miRNA and Role in Autophagy, Apoptosis and Pathogen Infection

MicroRNAs (miRNAs) are small non-coding RNAs with important roles in diverse biological processes including immunity. Japanese flounder (Paralichthys olivaceus) is an aquaculture fish species susceptible to the infection of bacterial and viral pathogens including Edwardsiella tarda. In a previous study, pol-miR-novel_547, a novel miRNA of flounder with unknown function, was found to be induced by E. tarda. In the present study, we investigated the regulation and function of pol-miR-novel_547 and its target gene. We found that pol-miR-novel_547 was regulated differently by E. tarda and the viral pathogen megalocytivirus, and pol-miR-novel_547 repressed the expression of PTEN (phosphatase and tensin homolog) of flounder (PoPTEN). PoPTEN is ubiquitously expressed in multiple tissues of flounder and responded to bacterial and viral infections. Interference with PoPTEN expression in flounder cells directly or via pol-miR-novel_547 promoted E. tarda invasion. Consistently, in vivo knockdown of PoPTEN enhanced E. tarda dissemination in flounder tissues, whereas in vivo overexpression of PoPTEN attenuated E. tarda dissemination but facilitated megalocytivirus replication. Further in vitro and in vivo studies showed that PoPTEN affected autophagy activation via the AKT/mTOR pathway and also modulated the process of apoptosis. Together these results reveal for the first time a critical role of fish PTEN and its regulatory miRNA in pathogen infection, autophagy, and apoptosis.

PTEN as a Guardian of the Genome: Pathways and Targets

Faithful transmission of genetic information is only possible with the structural and functional integrity of the genome. PTEN has been recognized as a guardian of the genome since the identification of its noncanonical localization and function in the nucleus. Yet, the role of PTEN in guarding the genome relies on integration of diverse mechanisms elicited by its canonical activity in antagonizing PI3K as well as emerging noncanonical functions. In the nucleus, PTEN maintains the structural integrity of chromosomes and the architecture of heterochromatin by physically interacting with chromosomal and nucleosomal components. PTEN also controls the functional integrity of key genetic transmission machineries by promoting proper assembly of the replisome and mitotic spindles. Deregulation of PTEN signaling impairs genome integrity, leading to spontaneous replication/mitotic stress and subsequent stress tolerance. Identification of novel targets of PTEN signaling and illumination of the interplay of diverse PTEN pathways in genome maintenance will help us better understand mechanisms underlying tumor evolution and therapeutic resistance.

PTEN Alterations and Their Role in Cancer Management: Are We Making Headway on Precision Medicine?

Alterations in the tumor suppressor phosphatase and tensin homolog (PTEN) occur in a substantial proportion of solid tumors. These events drive tumorigenesis and tumor progression. Given its central role as a downregulator of the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway, PTEN is deeply involved in cell growth, proliferation, and survival. This gene is also implicated in the modulation of the DNA damage response and in tumor immune microenvironment modeling. Despite the actionability of PTEN alterations, their role as biomarkers remains controversial in clinical practice. To date, there is still a substantial lack of validated guidelines and/or recommendations for PTEN testing. Here, we provide an update on the current state of knowledge on biologic and genetic alterations of PTEN across the most frequent solid tumors, as well as on their actual and/or possible clinical applications. We focus on possible tailored schemes for cancer patients' clinical management, including risk assessment, diagnosis, prognostication, and treatment.

PTEN Inhibition Protects Against Experimental Intracerebral Hemorrhage-Induced Brain Injury Through PTEN/E2F1/β-Catenin Pathway

Intracerebral hemorrhage (ICH) is a subtype of stroke with highest mortality and morbidity. We have previously demonstrated that dipotassium bisperoxo (picolinato) oxovanadate (V), (bpV[pic]) inhibits phosphatase and tensin homolog (PTEN) and activates extracellular signal-regulated kinase (ERK)1/2. In this study, we examined the effect of bpV[pic] in the rat ICH model in vivo and the hemin-induced injury model in rat cortical cultures. The rat model of ICH was created by injecting autologous blood into the striatum, and bpV[pic] was intraperitoneally injected. The effects of bpV[pic] were evaluated by neurological tests, Fluoro-Jade C (FJC) staining, and Nissl staining. We demonstrate that bpV[pic] attenuates ICH-induced brain injury in vivo and hemin-induced neuron injury in vitro. The expression of E2F1 was increased, but β-catenin expression was decreased after ICH, and the altered expressions of E2F1 and β-catenin after ICH were blocked by bpV[pic] treatment. Our results further show that bpV[pic] increases β-catenin expression through downregulating E2F1 in cortical neurons and prevents hemin-induced neuronal damage through E2F1 downregulation and subsequent upregulation of β-catenin. By testing the effect of PTEN-siRNA, PTEN cDNA, or combined use of ERK1/2 inhibitor and bpV[pic] in cultured cortical neurons after hemin-induced injury, we provide evidence suggesting that PTEN inhibition by bpV[pic] confers neuroprotection through E2F1 and β-catenin pathway, but the neuroprotective role of ERK1/2 activation by bpV[pic] cannot be excluded.

Inhibiting Pathways Predicted From a Steroid Hormone Gene Signature Yields Synergistic Antitumor Effects in NSCLC

INTRODUCTION

Mounting evidence supports a role for estrogen signaling in NSCLC progression. We previously reported a seven-gene signature that predicts prognosis in estrogen receptor β positive (ERβ+) NSCLC. The signature defines a network comprised of ER and human EGFR-2/3 (HER2/HER3) signaling.

METHODS

We tested the efficacy of combining the pan-HER inhibitor, dacomitinib, with the estrogen antagonist, fulvestrant, in ERβ+ NSCLC models with differing genotypes. We assessed the potency of this combination on xenograft growth and survival of host mice, and the ability to reverse the gene signature associated with poor outcome.

RESULTS

Synergy was observed between dacomitinib and fulvestrant in three human ERβ+ NSCLC models: 201T (wild-type EGFR), A549 (KRAS mutant), and HCC827 (EGFR 19 deletion) with combination indices of 0.1-0.6. The combination, but not single agents, completely reversed the gene signature associated with poor prognosis in a mechanism that is largely mediated by activator protein 1 downregulation. In vivo, the combination also induced tumor regression and reversed the gene signature. In HCC827 xenografts treated with the combination, survival of mice was prolonged after therapy discontinuation, tumors that recurred were less aggressive, and two mechanisms of HER inhibitor resistance involving c-Met activation and PTEN loss were blocked.

CONCLUSIONS

The combination of an ER blocker and a pan-HER inhibitor provides synergistic efficacy in different models of ERβ+ NSCLC. Our data support the use of this combination clinically, considering its ability to induce potent antitumor effects and produce a gene signature that predicts better clinical outcomes.

PTEN in Lung Cancer: Dealing with the Problem, Building on New Knowledge and Turning the Game Around

Lung cancer is the most common malignancy and cause of cancer deaths worldwide, owing to the dismal prognosis for most affected patients. Phosphatase and tensin homolog deleted in chromosome 10 (PTEN) acts as a powerful tumor suppressor gene and even partial reduction of its levels increases cancer susceptibility. While the most validated anti-oncogenic duty of PTEN is the negative regulation of the PI3K/mTOR/Akt oncogenic signaling pathway, further tumor suppressor functions, such as chromosomal integrity and DNA repair have been reported. PTEN protein loss is a frequent event in lung cancer, but genetic alterations are not equally detected. It has been demonstrated that its expression is regulated at multiple genetic and epigenetic levels and deeper delineation of these mechanisms might provide fertile ground for upgrading lung cancer therapeutics. Today, PTEN expression is usually determined by immunohistochemistry and low protein levels have been associated with decreased survival in lung cancer. Moreover, available data involve PTEN mutations and loss of activity with resistance to targeted treatments and immunotherapy. This review discusses the current knowledge about PTEN status in lung cancer, highlighting the prevalence of its alterations in the disease, the regulatory mechanisms and the implications of PTEN on available treatment options.

miR-3691-5p promotes hepatocellular carcinoma cell migration and invasion through activating PI3K/Akt signaling by targeting PTEN

Background: The enhanced ability of cancer metastasis is the major cause for the cancer-related death of hepatocellular carcinoma (HCC). Better understanding the mechanisms for the motility of cancer cells will benefit the treatment. Accumulating evidence suggests that aberrant microRNA (miRNA) expression contributes to HCC development and progression, whereas miR-3691-5p has not been reported in HCC.

Purpose: The aim of this study was to elucidate the expression, function and mechanism of miR-3691-5p in HCC.

Methods: Real-time quantitative polymerase chain reaction (qPCR) was performed to detect miR-3691-5p expression in HCC tissues and cell lines database analysis were conducted for detection of the expression of miR-3691-5p in HCC. Then, the association of miR-3691-5p with clinicopathological features of HCC patients were statistically measured. Subsequently, we attempted to observe the effects of miR-3691-5p on migration and invasion of HCC cells by transwell assays. Furthermore, bioinformatics tools and luciferase reporter gene assay as well as recuse experiments were conducted to explore the target of miR-3691-5p in HCC, and to explore whether the target mediated the effects of miR-3691-5p HCC cells.

Results: In the current study, we found that miR-3691-5p expression was elevated in both HCC tissues and cell lines, which was significantly correlated with poor prognosis and clinicopathological features including TNM stage (P=0.016) and vascular invasion (P=0.016). Furthermore, gain-or loss-of function assays demonstrated that miR-3691-5p promoted HCC cell migration and invasion. Luciferase reporter assay confirmed that PTEN was a direct downstream target of miR-3691-5p. Recuse assays showed that restoration of PTEN reversed the effects of miR-3691-5p on HCC cell migration and invasion through decreasing PI3K/Akt signaling.

Conclusion: Our results demonstrated that miR-3691-5p contributes to HCC cell migration and invasion through activating PI3K/Akt signaling by targeting PTEN.

Long non-coding RNA-HAGLR suppressed tumor growth of lung adenocarcinoma through epigenetically silencing E2F1

Emerging evidence indicates that long noncoding RNAs (LncRNAs) are new players in gene regulation but their mechanisms of action are mainly undocumented. In this study, we investigated LncRNA alterations that contribute to lung cancer by analyzing published microarray data in Gene Expression Obminus (GEO) and The Cancer Genome Atlas RNA (TCGA) sequencing data. Here, we reported that HAGLR (also called HOXD-AS1) was frequently down-regulated in lung adenocarcinoma (LUAD) tissues, and decreased HAGLR expression was clinically associated with shorter survival of LUAD patients. Preclinical studies using multiple LUAD cells and in vivo mouse model indicated that HAGLR could attenuate LUAD cell growth in vitro and in vivo. Mechanistically, HAGLR could physically interact with DNMT1, and recruit DNMT1 on E2F1 promoter to increase local DNA methylation. Overall, our study demonstrated that HAGLR promoted LUAD progression by recruiting DNMT1 to modulate the promoter methylation and expression of E2F1, which expanded potential therapeutic strategies for LUAD treatment.

Enhanced plasma miR-142-5p promotes the progression of intrahepatic cholangiocarcinoma via targeting PTEN

The aim of the present study was to evaluate the expression and specific role of microRNA (miR)-142-5p in the progression of intrahepatic cholangiocarcinoma (ICC). Reverse transcription-quantitative polymerase chain reaction was performed to evaluate miR-142-5p expression in patients with ICC and healthy control subjects. The results revealed that plasma miR-142-5p was significantly increased in patients with ICC compared with the control group. Furthermore, miR-142-5p was also increased in ICC tissues compared with adjacent non-neoplastic tissues. Compared with patients with Ta-T1 stage ICC, miR-142-5p was significantly elevated in patients with ICC ≥T2 stage. Patients with ICC at G3 stage had much higher plasma miR-142-5p levels compared with those at G1/2 stage. Receiver operating characteristic analysis indicated that miR-142-5p could be used as a biomarker to differentiate patients with ICC from healthy controls. Kaplan-Meier analysis demonstrated that plasma miR-142-5p was negatively correlated with survival in patients with ICC. A dual luciferase reporter assay indicated that miR-142-5p significantly suppressed the relative luciferase activity of pmirGLO-PTEN-3' untranslated region compared with the control group. In summary, the results of the present study provide novel data indicating that plasma miR-142-5p is significantly upregulated in patients with ICC. miR-142-5p may therefore have potential as a biomarker for screening patients with ICC from healthy controls.