Expression and prognostic significance of PTEN product protein in patients with esophageal squamous cell carcinoma

Multiomics blueprint of PANoptosis in deciphering immune characteristics and prognosis stratification of glioma patients

BACKGROUND

As the most prevalent primary brain tumor in adults, glioma accounts for the majority of all central nervous system malignant tumors. The concept of PANoptosis is a relatively new, underlining the interconnection and synergy among three distinct pathways: pyroptosis, apoptosis and necroptosis.

METHODS

We performed single-cell annotations of glioma cells and determined crucial signaling pathways through cell chat analysis. Using least absolute shrinkage and selection operator (LASSO) and Cox analyses, we identified a gene set with prognostic values. Our model was validated using independent external cohort. In addition, we employed single-sample gene set enrichment analysis and xCell analyses to describe the detailed profile of infiltrated immune cells and depicted the gene mutation landscape in the two groups.

RESULTS

We identified seven distinct cell clusters in glioma samples, including oligodendrocyte precursor cells (OPCs), myeloid cells, tumor cells, oligodendrocytes, astrocytes, vascular cells and neuronal cells. We found that myeloid cells showed the highest PANoptosis activity. An intense mutual cell communication pattern between the tumor cells and OPCs and oligodendrocytes was observed. Differentially expressed genes between the high-PANoptosis and low-PANoptosis cell groups were obtained, which were enriched to actin cytoskeleton, cell adhesion molecules and gamma R-mediated phagocytosis pathways. We determined a set of five genes of prognostic significance: SAA1, SLPI, DCX, S100A8 and TNR. The prognostic differences between the two groups in the internal and external sets were found to be statistically significant. We found a marked correlation between S100A8 and activated dendritic cell, macrophage, mast cell, myeloid derived suppressor cell and Treg infiltration. Moreover, we have observed a significant increase of PTEN mutation in the high risk (HR) group of glioma patients.

CONCLUSIONS

In the present study, we have constructed a prognostic model that is based on the PANoptosis, and we have demonstrated its significant efficacy in stratifying patients with glioma. This innovative prognostic model offers novel insights into precision immune treatments that could be used to combat this disease and improve patient outcomes, thereby providing a new avenue for personalized treatment options.

Nuclear PTEN Regulates Thymidylate Biosynthesis in Human Prostate Cancer Cell Lines

The phosphatase and tensin homologue deleted on chromosome 10 (PTEN) tumor suppressor governs a variety of biological processes, including metabolism, by acting on distinct molecular targets in different subcellular compartments. In the cytosol, inactive PTEN can be recruited to the plasma membrane where it dimerizes and functions as a lipid phosphatase to regulate metabolic processes mediated by the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin complex 1 (mTORC1) pathway. However, the metabolic regulation of PTEN in the nucleus remains undefined. Here, using a gain-of-function approach to targeting PTEN to the plasma membrane and nucleus, we show that nuclear PTEN contributes to pyrimidine metabolism, in particular de novo thymidylate (dTMP) biosynthesis. PTEN appears to regulate dTMP biosynthesis through interaction with methylenetetrahydrofolate dehydrogenase 1 (MTHFD1), a key enzyme that generates 5,10-methylenetetrahydrofolate, a cofactor required for thymidylate synthase (TYMS) to catalyze deoxyuridylate (dUMP) into dTMP. Our findings reveal a nuclear function for PTEN in controlling dTMP biosynthesis and may also have implications for targeting nuclear-excluded PTEN prostate cancer cells with antifolate drugs.

Pan-cancer genomic analysis shows hemizygous PTEN loss tumors are associated with immune evasion and poor outcome

In tumors, somatic mutations of the PTEN suppressor gene are associated with advanced disease, chemotherapy resistance, and poor survival. PTEN loss of function may occur by inactivating mutation, by deletion, either affecting one copy (hemizygous loss) leading to reduced gene expression or loss of both copies (homozygous) with expression absent. Various murine models have shown that minor reductions in PTEN protein levels strongly influence tumorigenesis. Most PTEN biomarker assays dichotomize PTEN (i.e. presence vs. absence) ignoring the role of one copy loss. We performed a PTEN copy number analysis of 9793 TCGA cases from 30 different tumor types. There were 419 (4.28%) homozygous and 2484 (25.37%) hemizygous PTEN losses. Hemizygous deletions led to reduced PTEN gene expression, accompanied by increased levels of instability and aneuploidy across tumor genomes. Outcome analysis of the pan-cancer cohort showed that losing one copy of PTEN reduced survival to comparable levels as complete loss, and was associated with transcriptomic changes controlling immune response and the tumor microenvironment. Immune cell abundances were significantly altered for PTEN loss, with changes in head and neck, cervix, stomach, prostate, brain, and colon more evident in hemizygous loss tumors. These data suggest that reduced expression of PTEN in tumors with hemizygous loss leads to tumor progression and influences anticancer immune response pathways.

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.

Targeting the PI3K/AKT/mTOR and RAF/MEK/ERK pathways for cancer therapy

The PI3K/AKT/mTOR and RAF/MEK/ERK pathways are commonly activated by mutations and chromosomal translocation in vital targets. The PI3K/AKT/mTOR signaling pathway is dysregulated in nearly all kinds of neoplasms, with the component in this pathway alternations. RAF/MEK/ERK signaling cascades are used to conduct signaling from the cell surface to the nucleus to mediate gene expression, cell cycle processes and apoptosis. RAS, B-Raf, PI3K, and PTEN are frequent upstream alternative sites. These mutations resulted in activated cell growth and downregulated cell apoptosis. The two pathways interact with each other to participate in tumorigenesis. PTEN alterations suppress RAF/MEK/ERK pathway activity via AKT phosphorylation and RAS inhibition. Several inhibitors targeting major components of these two pathways have been supported by the FDA. Dozens of agents in these two pathways have attracted great attention and have been assessed in clinical trials. The combination of small molecular inhibitors with traditional regimens has also been explored. Furthermore, dual inhibitors provide new insight into antitumor activity. This review will further comprehensively describe the genetic alterations in normal patients and tumor patients and discuss the role of targeted inhibitors in malignant neoplasm therapy. We hope this review will promote a comprehensive understanding of the role of the PI3K/AKT/mTOR and RAF/MEK/ERK signaling pathways in facilitating tumors and will help direct drug selection for tumor therapy.

Attacking the PI3K/Akt/mTOR signaling pathway for targeted therapeutic treatment in human cancer

Cancer is the second leading cause of human death globally. PI3K/Akt/mTOR signaling is one of the most frequently dysregulated signaling pathways observed in cancer patients that plays crucial roles in promoting tumor initiation, progression and therapy responses. This is largely due to that PI3K/Akt/mTOR signaling is indispensable for many cellular biological processes, including cell growth, metastasis, survival, metabolism, and others. As such, small molecule inhibitors targeting major kinase components of the PI3K/Akt/mTOR signaling pathway have drawn extensive attention and been developed and evaluated in preclinical models and clinical trials. Targeting a single kinase component within this signaling usually causes growth arrest rather than apoptosis associated with toxicity-induced adverse effects in patients. Combination therapies including PI3K/Akt/mTOR inhibitors show improved patient response and clinical outcome, albeit developed resistance has been reported. In this review, we focus on revealing the mechanisms leading to the hyperactivation of PI3K/Akt/mTOR signaling in cancer and summarizing efforts for developing PI3K/Akt/mTOR inhibitors as either mono-therapy or combination therapy in different cancer settings. We hope that this review will facilitate further understanding of the regulatory mechanisms governing dysregulation of PI3K/Akt/mTOR oncogenic signaling in cancer and provide insights into possible future directions for targeted therapeutic regimen for cancer treatment, by developing new agents, drug delivery systems, or combination regimen to target the PI3K/Akt/mTOR signaling pathway. This information will also provide effective patient stratification strategy to improve the patient response and clinical outcome for cancer patients with deregulated PI3K/Akt/mTOR signaling.

PTEN in Hereditary and Sporadic Cancer

Germline pathogenic phosphatase and tensin homolog (PTEN) mutations cause PTEN hamartoma tumor syndrome (PHTS), characterized by various benign and malignant tumors of the thyroid, breast, endometrium, and other organs. Patients with PHTS may present with other clinical features such as macrocephaly, intestinal polyposis, cognitive changes, and pathognomonic skin changes. Clinically, deregulation of PTEN function is implicated in other human diseases in addition to many types of human cancer. PTEN is an important phosphatase that counteracts one of the most critical cancer pathways: the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathways. Although PTEN can dephosphorylate lipids and proteins, it also has functions independent of phosphatase activity in normal and pathological states. It is positively and negatively regulated at the transcriptional level as well as posttranslationally by phosphorylation, ubiquitylation, oxidation, and acetylation. Although most of its tumor-suppressor activity is likely to be caused by lipid dephosphorylation at the plasma membrane, PTEN also resides in the cytoplasm and nucleus, and its subcellular distribution is under strict control. In this review, we highlight our current knowledge of PTEN function and recent discoveries in understanding PTEN function regulation and how this can be exploited therapeutically for cancer treatment.

Loss of phosphatase activity in PTEN (phosphatase and tensin homolog deleted on chromosome ten) results in endometrial carcinoma in humans: An in-silico study

The tumour suppressor gene, PTEN (Phosphatase and Tensin homolog deleted on chromosome Ten), can act as both protein phosphatase and lipid phosphatase, is known to play a vital role in Pi3k signalling pathway. In humans, it is located at 10q23. Loss of its phosphatase and catalytic activity is associated with various types of cancers. This study focuses on evolution, understanding the somatic missense mutation in a particular residue of PTEN and understanding the molecular mechanism that leads to endometrial carcinoma through molecular docking. Mutational analysis of H123 position indicates that the missense mutation at first position of the codon CAC by G or T, result in aspartic acid or tyrosine instead of histidine and can have negative effect on the function of PTEN. Alongside, structural analysis showed mutated PTEN has lower stability than the normal. Additionally, SNPs dataset for endometrial carcinoma suggests H123 as strongly mutated residue. The mutation in phosphatase domain of PTEN along with its effect and interaction with substrate TLA1352 were systematically studied through molecular docking. Molecular interaction study reveals that the optimal substrate binding site in PTEN is unable to interact with the substrate in the mutated condition. This observation drew attention on the impact of mutation on disease biology and enabled us to conduct follow-up studies to retrieve novel molecular targets, such as mutated protein domain and modified Asp and Tyr sites, to design effective therapies to either prevent endometrial carcinoma or impede its progression.

PI3K-AKT-mTOR and NFκB Pathways in Ovarian Cancer: Implications for Targeted Therapeutics

Ovarian cancer is the most lethal gynecologic malignancy in the United States, with an estimated 22,530 new cases and 13,980 deaths in 2019. Recent studies have indicated that the phosphoinositol 3 kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR), as well as the nuclear factor-κ light chain enhancer of activated B cells (NFκB) pathways are highly mutated and/or hyper-activated in a majority of ovarian cancer patients, and are associated with advanced grade and stage disease and poor prognosis. In this review, we will investigate PI3K/AKT/mTOR and their interconnection with NFκB pathway in ovarian cancer cells.

PTEN-opathies: from biological insights to evidence-based precision medicine

The tumor suppressor phosphatase and tensin homolog (PTEN) classically counteracts the PI3K/AKT/mTOR signaling cascade. Germline pathogenic PTEN mutations cause PTEN hamartoma tumor syndrome (PHTS), featuring various benign and malignant tumors, as well as neurodevelopmental disorders such as autism spectrum disorder. Germline and somatic mosaic mutations in genes encoding components of the PI3K/AKT/mTOR pathway downstream of PTEN predispose to syndromes with partially overlapping clinical features, termed the "PTEN-opathies." Experimental models of PTEN pathway disruption uncover the molecular and cellular processes influencing clinical phenotypic manifestations. Such insights not only teach us about biological mechanisms in states of health and disease, but also enable more accurate gene-informed cancer risk assessment, medical management, and targeted therapeutics. Hence, the PTEN-opathies serve as a prototype for bedside to bench, and back to the bedside, practice of evidence-based precision medicine.

A highly integrated precision nanomedicine strategy to target esophageal squamous cell cancer molecularly and physically

The prognosis of esophageal squamous cell carcinoma is poor. We hereby presented a highly integrated and clinically relevant precision nanomedicine strategy to target ESCC molecularly and physically for significant improvement of the treatment efficacy. We firstly identified PI3K overexpression in patient samples and its relation to poor patient survival. With our highly versatile tumor-targeted drug delivery platform (DCM), we were able to load a potent but toxic docetaxel (DTX) and a PI3K inhibitor (AZD8186) with favorable physical properties. The combination of the DTX-DCM and AZD8186-DCM showed a highly efficacious and synergistic anti-tumor effect and decreased hematotoxicity. A pro-apoptotic protein, Bax was significantly upregulated in ESCC cells treated with combination therapy compared to that with monotherapy. This study utilized a highly integrated precision nano-medicine strategy that combines the identification of cancer molecular target from human patients, precision drug delivery and effective combination therapy for the development of better ESCC treatment.

Clinical Significance of PTEN Deletion, Mutation, and Loss of PTEN Expression in De Novo Diffuse Large B-Cell Lymphoma

PTEN loss has been associated with poorer prognosis in many solid tumors. However, such investigation in lymphomas is limited. In this study, PTEN cytoplasmic and nuclear expression, PTEN gene deletion, and PTEN mutations were evaluated in two independent cohorts of diffuse large B-cell lymphoma (DLBCL). Cytoplasmic PTEN expression was found in approximately 67% of total 747 DLBCL cases, more frequently in the activated B-cell-like subtype. Nuclear PTEN expression was less frequent and at lower levels, which significantly correlated with higher PTEN mRNA expression. Remarkably, loss of PTEN protein expression was associated with poorer survival only in DLBCL with AKT hyperactivation. In contrast, high PTEN expression was associated with Myc expression and poorer survival in cases without abnormal AKT activation. Genetic and epigenetic mechanisms for loss of PTEN expression were investigated. PTEN deletions (mostly heterozygous) were detected in 11.3% of DLBCL, and showed opposite prognostic effects in patients with AKT hyperactivation and in MYC rearranged DLBCL patients. PTEN mutations, detected in 10.6% of patients, were associated with upregulation of genes involved in central nervous system function, metabolism, and AKT/mTOR signaling regulation. Loss of PTEN cytoplasmic expression was also associated with TP53 mutations, higher PTEN-targeting microRNA expression, and lower PD-L1 expression. Remarkably, low PTEN mRNA expression was associated with down-regulation of a group of genes involved in immune responses and B-cell development/differentiation, and poorer survival in DLBCL independent of AKT activation. Collectively, multi-levels of PTEN abnormalities and dysregulation may play important roles in PTEN expression and loss, and that loss of PTEN tumor-suppressor function contributes to the poor survival of DLBCL patients with AKT hyperactivation.

Knockdown of Phospholipase Cε (PLCε) Inhibits Cell Proliferation via Phosphatase and Tensin Homolog Deleted on Chromosome 10 (PTEN)/AKT Signaling Pathway in Human Prostate Cancer

Background

Phospholipase Cɛ (PLCɛ), a member of the plc family, has been extensively studied to reveal its role in the regulation of different cell functions, but understanding of the underlying mechanisms remains limited. In the present study, we explored the effects of PLCɛ on PTEN (phosphatase and tensin homolog deleted on chromosome 10) in cell proliferation in prostate cancer cells.

Material/Methods

We assessed PLCɛ and PTEN expression in human benign prostate tissues compared to prostate cancer tissues by immunohistochemistry. Lentivirus-shPLCɛ (LV-shPLCɛ) was designed to silence PLCɛ expression in DU145 and PC3 cell lines, and the effectiveness was tested by qRT-PCR and Western blotting. MTT assay and colony formation assay were conducted to observe cell proliferation. Western blotting and immunofluorescence assays were used to detect changed PTEN expression in DU145.

Results

We observed that PLCɛ expression was reduced in human benign prostate tissues compared to prostate cancer tissues, while PTEN expression showed the opposite trend. Silencing of the PLCɛ gene significantly inhibited cell proliferation in DU145 and PC3 cell lines. DU145 is a PTEN-expressing cell, while PC3 is PTEN-deficient. After infection by LV-shPLCɛ, we noticed that PTEN expression was up-regulated in DU145 cells but not in PC3 cells. Furthermore, we found that PLCɛ gene knockdown decreased P-AKT protein levels, but AKT protein levels were not affected. Immunofluorescence assays showed that PTEN expression had an intracellular distribution change in the DU145 cell line, and Western blot analysis showed that PTEN was obviously up-regulated in cell nucleus and cytoplasm.

Conclusions

PLCɛ is an oncogene, and knockdown of expression of PLCɛ inhibits PCa cells proliferation via the PTEN/AKT signaling pathway.

The Expression and Prognostic Impact of the PI3K/AKT/mTOR Signaling Pathway in Advanced Esophageal Squamous Cell Carcinoma

The abnormal phosphatase and tensin homolog expression and activated phosphoinositide-3 kinase/Protein kinase B (AKT)/mammalian target of rapamycin signaling pathway are involved in the progression of esophageal squamous cell carcinoma. By assessing the expression pattern of key components in the phosphoinositide-3 kinase/AKT/mammalian target of rapamycin signaling pathway by immunohistochemistry in tumor and nontumor esophageal mucosa from patients with esophageal squamous cell carcinomas, we aimed to carefully explore the relationship between the various protein expressions and clinicopathological factors, as well as patient outcome. A total of 145 tumor and 145 nontumor samples from patients with esophageal squamous cell carcinoma, collected from HuaShan Hospital (Shanghai, China) were evaluated. Clinical characteristics, the targeted protein expressions (including phosphatase and tensin homolog, phosphoinositide-3 kinase, AKT, p-AKT, mammalian target of rapamycin, p-mTOR, p70S6 kinase 1, p-P70S6K1, elongation initiation factor 4E binding protein-1, and p-4E-BP1, and survival rate were analyzed. Among them, phosphoinositide-3 kinase, AKT, p-AKT, mammalian target of rapamycin, p-mTOR, elongation initiation factor 4E binding protein-1, p70S6 kinase 1, and p-P70S6K1 proteins were significantly upregulated in tumor tissue. Conversely, phosphatase and tensin homolog was largely downregulated in tumor tissue, notably in pT3-T4 tumors. Low expression of phosphatase and tensin homolog whereas high expression of mammalian target of rapamycin signaling components in tumors was closely related to the presence of lymph node metastases and advanced TNM stage (all P < .05). Moreover phosphatase and tensin homolog, mammalian target of rapamycin, and p70S6 kinase 1 were correlated with overall survival as well as p-mTOR was correlated with progression-free survival (all P < .05). Overexpression of mammalian target of rapamycin was proved to be an independent adverse prognostic factor for overall survival in esophageal squamous cell carcinomas. Our results suggest that the phosphoinositide-3 kinase/AKT/mammalian target of rapamycin signaling pathway is activated in esophageal squamous cell carcinoma, with the low expression of phosphatase and tensin homolog and the high expression of the mammalian target of rapamycin component proteins (both total and phosphorylated) in tumor tissue. Our result might offer a new strategy for specific targeted therapy and prognostic assessment in esophageal cancer.

The Smad4/PTEN Expression Pattern Predicts Clinical Outcomes in Colorectal Adenocarcinoma

Background

Smad4 and PTEN are prognostic indicators for various tumor types. Smad4 regulates tumor suppression, whereas PTEN inhibits cell proliferation. We analyzed and compared the performance of Smad4 and PTEN for predicting the prognosis of patients with colorectal adenocarcinoma.

Methods

Combined expression patterns based on Smad4+/– and PTEN+/– status were evaluated by immunostaining using a tissue microarray of colorectal adenocarcinoma. The relationships between the protein expression and clinicopathological variables were analyzed.

Results

Smad4–/PTEN– status was most frequently observed in metastatic adenocarcinoma, followed by primary adenocarcinoma and tubular adenoma (p<.001). When Smad4–/PTEN– and Smad4+/PTEN+ groups were compared, Smad4–/PTEN– status was associated with high N stage (p=.018) and defective mismatch repair proteins (p=.006). Significant differences in diseasefree survival and overall survival were observed among the three groups (Smad4+/PTEN+, Smad4–/PTEN+ or Smad4+/PTEN–, and Smad4–/PTEN–) (all p<.05).

Conclusions

Concurrent loss of Smad4 and PTEN may lead to more aggressive disease and poor prognosis in patients with colorectal adenocarcinoma compared to the loss of Smad4 or PTEN alone.

SENP1 regulates PTEN stability to dictate prostate cancer development

SUMO protease SENP1 is elevated in multiple carcinomas including prostate cancer (PCa). SENP1 exhibits carcinogenic properties; it promotes androgen receptor-dependent and -independent cell proliferation, stabilizes HIF1a, increases VEGF, and supports angiogenesis. However, mice expressing an androgen-responsive promoter driven SENP1-transgene (SENP1-Tg) develop high-grade prostatic intraepithelial neoplasia, but not carcinoma. We now show that tumor suppressive PTEN signaling is induced in SENP1-Tg to enhance prostate epithelial cell apoptosis. SENP1 blocks SUMO1-dependent ubiquitylation and degradation of PTEN. In the absence of SENP1, SUMO1-modified PTEN is sequestered in the cytosol, where binding to ubiquitin-E3 ligase WWP2 occurs. Concurrently, WWP2 is also SUMOylated, which potentiates its interaction with PTEN. Thus, SENP1 directs ubiquitin-E3-substrate association to control PTEN stability. PTEN serves as a barrier for SENP1-mediated prostate carcinogenesis as SENP1-Tg mice develop invasive carcinomas only after PTEN reduction. Hence, SENP1 modulates multiple facets of carcinogenesis and may serve as a target specifically for aggressive PTEN-deficient PCa.

Phosphatase and tensin homolog (PTEN) expression on oncologic outcome in renal cell carcinoma: A systematic review and meta-analysis

The phosphatase and tensin homolog (PTEN) gene is suggested to be a dormant tumor suppressor. However, the prognostic value of the loss of PTEN expression in renal cell carcinoma (RCC) remains controversial. Therefore, we conducted a meta-analysis to evaluate the association of PTEN expression with the clinicopathological presentations and outcomes of patients with RCC through immunohistochemistry staining analysis. We systematically searched for relevant studies in PubMed, Web of Science, and Embase until March 2016. Data regarding clinical stage, pathological type, Fuhrman grade, overall survival (OS), progression-free survival (PFS), and disease-specific survival (DSS) was analyzed in the present study. In total, there were 12 studies with 2,368 patients included in this meta-analysis. The low PTEN expression in RCC was significantly associated with unfavorable DSS (HR = 1.568, 95% CI 1.015-2.242) in a random-effects model but not with OS (HR = 1.046, 95% CI 0.93-1.176) and PFS (HR = 1.244, 95% CI 0.907-1.704). Other results indicated that PTEN expression was not correlated with clinical stage, pathological type, and Fuhrman grade. This meta-analysis suggests that PTEN expression is of limited value in predicting the prognosis of patients with RCC for OS and PFS via immunohistochemistry staining analysis; and that for DSS, low PTEN expression is significantly associated with an unfavorable outcome.

Importin-11 keeps PTEN safe from harm

Nick R. Leslie discusses a new study by Chen et al., who show that Ipo11 regulates nuclear trafficking and tumor-suppressing function of PTEN.

In this issue, Chen et al. (2017. J. Cell Biol.https://doi.org/10.1083/jcb.201604025) show that Importin-11 traffics the tumor suppressor PTEN into the nucleus and in so doing protects it from cytoplasmic proteins that cause PTEN degradation. This work helps explain the nuclear accumulation of PTEN observed in many healthy tissues and, because Ipo11 mutant mice develop lung tumors, also implicates Importin-11 as a novel tumor suppressor.

In depth evaluation of the prognostic and predictive utility of PTEN immunohistochemistry in colorectal carcinomas: performance of three antibodies with emphasis on intracellular and intratumoral heterogeneity

BACKGROUND

Phosphatase and tensin homolog deleted in chromosome 10 (PTEN) loss of function is frequently detected in advanced colorectal cancer. Its detection is thought to have prognostic significance and it is being considered to predict responsiveness to anti-EGFR therapy. Unfortunately, while immunohistochemical assessment of PTEN expression is widespread, it lacks standardization and the results are hardly comparable across the available publications.

METHODS

Retrospectively collected, formalin-fixed and paraffin-embedded colorectal tumor tissue samples from 55 patients were combined into tissue microarray (TMA) blocks. We used three different PTEN antibodies to determine the frequency, intensity and intracellular pattern of PTEN immunohistochemical labeling: Neomarkers, Dako and CellSignaling. We evaluated the aforementioned parameters in selected regions of colorectal cancers and in their lymph node metastases by using three scoring methods that take into consideration both staining frequency and intensity (H1-H3-score). We also evaluated intracellular localization.

RESULTS

The Dako and CellSignaling antibodies stained predominantly cytoplasms, while the Neomarkers antibody specifically stained cell nuclei. PTEN H-scores were significantly lower in all tumor areas as compared to the normal colonic mucosa based on staining with the DAKO and CellSignaling antibodies. Intratumoral regional differences or differences between matching tumors and metastases were not detected with any of the antibodies. Neither Dako, neither CellSignaling, nor the Neomarkers antibodies revealed a significant correlation between PTEN expression and pT, Dukes/MAC and clinical stage. KRAS status, histological grade correlated with PTEN H-scores based on staining with the Neomarkers antibody. PTEN H-scores did not correlate with MMR status. PTEN H-scores did not show any correlation with relapse-free survival based on staining with either antibody.

CONCLUSIONS

While PTEN expression decreased in colorectal cancer according to two antibodies, neither of the three applied PTEN antibodies could justify significant correlation with clinicopathological data, nor had prognostic value. Thus, we might conclude that immunohistochemical PTEN investigation remains a challenge requiring more standardized evaluation on larger number of cases to clarify its utility as a prognostic and predictive tool in CRC. The standardization of immunohistochemical method is key in the evaluation process, which is further discussed.

Upregulation of microRNA‑337 promotes the proliferation of endometrial carcinoma cells via targeting PTEN

Endometrial carcinoma (EC) is a common malignancy in females. MicroRNAs (miRs) are a class of non‑coding RNA that regulate a wide variety of cellular processes, and are important in the development of multiple types of malignancy. In the present study, cancerous and adjacent non‑cancerous normal tissue samples were collected from 24 patients diagnosed with EC. Reverse transcription quantitative polymerase chain reaction was performed on the tissue samples to determine the expression levels of six candidate miRs. These miRs have been previously reported to be differentially expressed in EC; however, the present study observed that only miR‑337 was differentially expressed. In addition, the current study identified phosphatase and tensin homolog (PTEN) as a target of miR‑337 using computational analysis and a luciferase assay. EC cells transfected with miR‑337 mimics and anti‑PTEN small interfering RNA demonstrated significantly decreased expression of PTEN, markedly increased proliferation and inhibition of cell apoptosis. The results indicate that miR‑337 is oncogenic in EC cells, as it suppresses PTEN expression. This may facilitate the development of miR‑based prevention or treatment strategies for EC.

Herpes simplex virus type 1 VP22-mediated intercellular delivery of PTEN increases the antitumor activity of PTEN in esophageal squamous cell carcinoma cells in vitro and in vivo

In the past decade, studies have revealed that the phosphatase and tensin homolog (PTEN) protein, a tumor suppressor, comprises a potential biological marker and therapeutic target for esophageal squamous cell carcinoma (ESCC). As such, the delivery of the PTEN gene represents a powerful strategy for ESCC therapy. The tegument protein VP22 of herpes simplex virus type 1 (HSV-1) has been reported to act as a transporter of heterologous proteins across the host cell membrane, thereby enhancing the biological functions of these proteins. In the present study, the intercellular delivery and antitumor activity of the fusion protein PTEN-VP22 were examined in the esophageal squamous cell carcinoma cell line Eca109 both in vitro and in vivo. VP22-mediated PTEN intercellular delivery was confirmed in the Eca109 cells by western blot analysis and by quantitation of immunofluorescence. VP22 alone did not exert antiproliferative effects or induce cell cycle arrest, induction of apoptosis, blockage of the Akt and focal adhesion kinase (FAK) pathways, tumor growth inhibition, or antiangiogenic effects in Eca109 cells. However, compared with PTEN alone, PTEN-VP22 exerted significantly higher antiproliferative effects and induced cell cycle arrest at G1 stage, apoptosis and antiangiogenic effects in Eca109 cells. Together, our findings demonstrate that VP22 alone does not exert antitumor activity directly; however, this protein mediates the intercellular delivery of PTEN and thereby increases its intracellular concentration to achieve a therapeutic steady state, leading to an overall increase in the antitumor activity of PTEN. This study provides further experimental data to confirm the potential of VP22-based intercellular delivery strategies for enhancing the efficacy of gene therapy for cancer treatment.

PTEN at 18: Still Growing

Discovered in 1997, PTEN remains one of the most studied tumor suppressors. In this issue of Methods in Molecular Biology, we assembled a series of papers describing various clinical and experimental approaches to studying PTEN function. Due to its broad expression, regulated subcellular localization, and intriguing phosphatase activity, methodologies aimed at PTEN study have often been developed in the context of mutations affecting various aspects of its regulation, found in patients burdened with PTEN loss-driven tumors. PTEN's extensive posttranslational modifications and dynamic localization pose unique challenges for studying PTEN features in isolation and necessitate considerable development of experimental systems to enable controlled characterization. Nevertheless, ongoing efforts towards the development of PTEN knockout and knock-in animals and cell lines, antibodies, and enzymatic assays have facilitated a huge body of work, which continues to unravel the fascinating biology of PTEN.

Assessing PTEN Subcellular Localization

PTEN subcellular localization is fundamental in the execution of the distinct PTEN biological activities, including not only its PI(3,4,5)P3 phosphatase activity when associated to membranes but also its subcellular compartment-specific interactions with regulatory and effector proteins, including those exerted in the nucleus. As a consequence, PTEN subcellular localization is tightly regulated in vivo by both intrinsic and extrinsic mechanisms. The plasma membrane/nucleus/cytoplasm partitioning of PTEN has been the focus of several studies, both from a mechanistic and from a disease-association point of view. Here, we summarize the current knowledge on PTEN plasma membrane/nucleus/cytoplasm distribution, and present subcellular fractionation, immunofluorescence, and immunohistochemical methods to study the distribution and shuttling of PTEN between these subcellular compartments.

The PTEN tumor suppressor gene and its role in lymphoma pathogenesis

The phosphatase and tensin homolog gene PTEN is one of the most frequently mutated tumor suppressor genes in human cancer. Loss of PTEN function occurs in a variety of human cancers via its mutation, deletion, transcriptional silencing, or protein instability. PTEN deficiency in cancer has been associated with advanced disease, chemotherapy resistance, and poor survival. Impaired PTEN function, which antagonizes phosphoinositide 3-kinase (PI3K) signaling, causes the accumulation of phosphatidylinositol (3,4,5)-triphosphate and thereby the suppression of downstream components of the PI3K pathway, including the protein kinase B and mammalian target of rapamycin kinases. In addition to having lipid phosphorylation activity, PTEN has critical roles in the regulation of genomic instability, DNA repair, stem cell self-renewal, cellular senescence, and cell migration. Although PTEN deficiency in solid tumors has been studied extensively, rare studies have investigated PTEN alteration in lymphoid malignancies. However, genomic or epigenomic aberrations of PTEN and dysregulated signaling are likely critical in lymphoma pathogenesis and progression. This review provides updated summary on the role of PTEN deficiency in human cancers, specifically in lymphoid malignancies; the molecular mechanisms of PTEN regulation; and the distinct functions of nuclear PTEN. Therapeutic strategies for rescuing PTEN deficiency in human cancers are proposed.

microRNA-93 promotes cell proliferation via targeting of PTEN in Osteosarcoma cells

BACKGROUND

Aberrant microRNA (miRNA) expression plays an essential role in osteosarcoma (OS) pathogenesis. Recent studies have shown that dysregulation of miRNA expression is associated with increased tumorigenesis and poor prognosis in several types of cancers, including OS. The aim of this study was to investigate the relevant microRNAs involved in the development of OS.

METHODS

To explore possible oncogenic factors in OS, we used a microarray-based approach to profile changes in the expression of miRNAs and their target mRNAs in five OS cell lines and human mesenchymal stem cells (hMSCs). An miRNA, miR-93, was significantly up-regulated, whereas phosphatase and tensin homologue (PTEN) expression was significantly down-regulated in all tested OS cells, when compared with hMSCs.

RESULTS

When anti-miR-93 was transfected into OS cell lines, PTEN expression was greatly increased, suggesting that PTEN might be a target of miR-93 in ES cells. The expression of phosphorylated Akt protein, which is known to be inversely correlated with that of PTEN, was significantly down-regulated in anti-miR-93-transfected cells. Furthermore, transfection of anti-miR-93 inhibited the proliferation and cell cycle progression of ES cells. In addition, the down-regulation of miR-93 in these cells significantly suppressed tumor growth in vivo.

CONCLUSION

Ectopic expression of miR-93 decreased PTEN protein levels. Furthermore, miR-93 increased proliferation and decreased apoptosis in OS cells, whereas its silencing in these cells inhibited such carcinogenic processes. Taking these observations together, miR-93 can be seen to play a critical role in carcinogenesis through suppression of PTEN, and may serve as a therapeutic target for the treatment of OS.

PTEN gene is infrequently hypermethylated in human esophageal squamous cell carcinoma

Whether promoter hypermethylation of phosphatase and tensin homologue deleted from chromosome 10 (PTEN) is associated with loss of PTEN expression was not yet elucidated in esophageal squamous cell carcinoma (ESCC). The methylation status of PTEN gene was evaluated in 74 ESCC specimens and four esophageal cancer cell lines. Its association with clinicopathological factors or the prognosis was investigated by statistical analysis. We further measured messenger RNA (mRNA) and protein level of PTEN by quantitative RT-PCR and immunohistochemistry and studied the role of PTEN hypermethylation in loss of PTEN expression in clinical samples. Next, demethylation of PTEN gene with 5-azaC in EC9706 was performed to confirm the clinical findings. PTEN methylation was only found in 14 (18.9 %) of 74 ESCC tumor samples and one (EC9706) of four esophageal cancer cell lines. PTEN methylation was not statistically associated with clinicopathological factors and the prognosis (p > 0.05). In addition, 41 patients (55.4 %) and 38 patients (51.4 %) showed reduced mRNA level of PTEN and negative expression of PTEN protein in ESCC tumors, respectively. Detailed analysis indicated that PTEN methylation was a possible mechanism of loss of PTEN expression in ESCC, and further 5-azaC demethylation revealed inversed methylation status and increased mRNA or protein level of PTEN in EC9706. However, the role of PTEN methylation in loss of PTEN expression was still limited due to low frequency of methylation in ESCC. PTEN hypermethylation is a rare event and did not play an important role in the prognosis and loss of PTEN expression in ESCC.

Negative expression of PTEN identifies high risk for lymphatic-related metastasis in human esophageal squamous cell carcinoma

The poor prognosis of esophageal squamous cell carcinoma (ESCC) is mainly attributed to higher lymphatic-related metastatic ability. Whether the loss of expression of the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is associated with lymphatic-related metastasis needs elucidation. In the present study, we assessed the mRNA and protein level of PTEN in ESCC by qRT-PCR and immunohistochemistry. The results showed PTEN mRNA level in tumors was significantly lower than that in corresponding non-tumor esophageal epitheliums (p<0.001), while 38 (51.4%) tumor samples were negative for expression of PTEN in ESCC tumors. Then the association between negative expression of PTEN and lymphatic-related metastasis (lymph node metastasis/3-year postoperative lymphatic metastatic recurrence) was evaluated. The proportion of PTEN-negative expression was significantly higher in positive lymph node metastasis (pN+) than that in negative lymph node metastasis (pN0) (p=0.021). The negative expression of PTEN was not an independent risk factor for the lymphatic recurrence rate in multivariate analysis (p=0.498), however, the lymphatic recurrence rate (60.5%) in PTEN-negative expression group was higher than that (36.1%) in PTEN-positive expression group (p=0.019). Furthermore, PTEN expression was stably silenced by lentiviral-vectored shRNA (Lenti-shRNA) in Eca109 (ESCC-derived cell line) to study functional effect of PTEN in vitro and in vivo. The laboratory study indicated increased cell proliferation, migration and invasion in vitro and more rapid growth rate of xenograft tumors in vivo after stable silencing of PTEN expression. Moreover, we proved that FAK/pFAK were not the main factors mediating the mechanism of metastasis in ESCC. In conclusion, negative expression of PTEN could be a useful biomarker to predict high risk for lymphatic-related metastasis in ESCC.

PTEN Expression as a Predictor of Response to Focal Adhesion Kinase Inhibition in Uterine Cancer

PTEN is known to be frequently mutated in uterine cancer and also dephosphorylates FAK. Here, we examined the impact of PTEN alterations on the response to treatment with a FAK inhibitor (GSK2256098). In vitro and in vivo therapeutic experiments were carried out using PTEN-mutated and PTEN-wild-type models of uterine cancer alone and in combination with chemotherapy. Treatment with GSK2256098 resulted in greater inhibition of pFAK(Y397) in PTEN-mutated (Ishikawa) than in PTEN-wild-type (Hec1A) cells. Ishikawa cells were more sensitive to GSK2256098 than the treated Hec1A cells. Ishikawa cells were transfected with a wild-type PTEN construct and pFAK(Y397) expression was unchanged after treatment with GSK2256098. Decreased cell viability and enhanced sensitivity to chemotherapy (paclitaxel and topotecan) in combination with GSK2256098 was observed in Ishikawa cells as compared with Hec1a cells. In the Ishikawa orthoptopic murine model, treatment with GSK2256098 resulted in lower tumor weights and fewer metastases than mice inoculated with Hec1A cells. Tumors treated with GSK2256098 had lower microvessel density (CD31), less cellular proliferation (Ki67), and higher apoptosis (TUNEL) rates in the Ishikawa model when compared with the Hec1a model. From a large cohort of evaluable patients, increased FAK and pFAK(Y397) expression levels were significantly related to poor overall survival. Moreover, PTEN levels were inversely related to pFAK(Y397) expression. These preclinical data demonstrate that PTEN-mutated uterine cancer responds better to FAK inhibition than does PTEN wild-type cancer. Therefore, PTEN could be a biomarker for predicting response to FAK-targeted therapy during clinical development.

MiR-130b plays an oncogenic role by repressing PTEN expression in esophageal squamous cell carcinoma cells

BACKGROUND

Esophageal carcinoma is one of the most common malignancies with high cancer-related morbidity and mortality worldwide. MicroRNAs (miRNAs) are a class of small non-coding RNAs that regulate a wide variety of cellular processes, and also play an important role in the development and progression of cancers. In a previous microarray study, we demonstrated that miR-130b was upregulated in esophageal squamous cell carcinoma (ESCC) tissues. However, the biologic functions and the molecular mechanism of miR-130b in ESCC remain to be elucidated.

METHODS

qRT-PCR assays were used to quantify miR-130b expression levels in ESCC samples. Novel targets of miR-130b were identified via a bioinformatics search and confirmed using a dual-luciferase reporter system. Western blotting and qRT-PCR assays were used to quantify the expression of the target gene PTEN (phosphatase and tensin homolog) and the downstream effector, Akt. ESCC cells over- or underexpressing miR-130b were analyzed for in vitro biologic functions.

RESULTS

High levels of miR-130b were identified in 20 ESCC samples following comparison with adjacent non-neoplastic tissues. We confirmed that miR-130b interacted with the 3'-untranslated region of PTEN, and that an increase in the expression level of miR-130b negatively affected the protein level of PTEN. However, the dysregulation of miR-130b had no obvious impact on PTEN mRNA. As Akt is a downstream effector of PTEN, we explored if miR-130b affected Akt expression, and found that miR-130b indirectly regulated the level of phosphorylated Akt, while total Akt protein remained unchanged. Overexpression of miR-130b increased the proliferation of ESCC cells and enhanced their ability to migrate and invade. In contrast, the proliferation, migration, and invasion of ESCC cells were weakened when miR-130b expression was suppressed, which was reversed by PTEN-targeted siRNA.

CONCLUSION

The results indicate that miR-130b plays an oncogenic role in ESCC cells by repressing PTEN expression and Akt phosphorylation, which would be helpful in developing miRNA-based treatments for ESCC.

Characterization of nuclear PTEN and its post translational modifications

Somatic loss-of-function mutations of PTEN are found in a variety of human malignancies. Our recent work demonstrated that the nuclear function of PTEN is implicated in the maintenance of genome integrity. Proper subcellular localization of PTEN following genotoxic stress is coordinated by a cellular mechanism that involves post-translational modification by SUMOylation and ATM-mediated phosphorylation. Here we summarize biochemical and cell-based methodologies that can be used to characterize the SUMOylation and phosphorylation state of nuclear PTEN in the context of DNA damage. In addition, we describe assays to determine the biological function of SUMO-PTEN in homologous recombination DNA repair. These methods will help elucidate the precise molecular mechanisms of PTEN's role in the maintenance of genomic stability.

Modeling glands with PTEN deficient cells and microscopic methods for assessing PTEN loss: endometrial cancer as a model

PTEN is an important tumor suppressor gene. Interpreting PTEN deficiency in the appropriate microscopic context of cancer may be important to understand its role in tumor development and progression. This may be particularly relevant in heterogeneous tumors. Here, we discuss the usefulness of 3D cultures in understanding the consequences of PTEN inactivation in tissue architecture. Afterwards, we discuss the role of immunohistochemistry and fluorescent in situ hybridization in assessing PTEN loss in tumors. In this review, endometrial carcinoma is used as a model.

Esophageal cancer in a family with hamartomatous tumors and germline PTEN frameshift and SMAD7 missense mutations

Germline mutations in the PTEN tumor-suppressor gene cause autosomal-dominant conditions such as Cowden and Bannayan-Riley-Ruvalcaba syndromes with variable presentations, including hamartomatous gastrointestinal tumors, dermatologic abnormalities, neurologic symptoms, and elevated cancer risk. We describe a father and son with extensive hamartomatous gastrointestinal polyposis who both developed early-onset esophageal cancer. Exome sequencing identified a novel germline PTEN frameshift mutation (c.568_569insC, p.V191Sfs*11). In addition, a missense mutation of SMAD7 (c.115G>A, p.G39R) with an allele frequency of 0.3% in the Exome Variant Server was detected in both affected individuals. Fluorescence in situ hybridization for PTEN in the resected esophageal cancer specimen demonstrated no PTEN copy loss in malignant cells; however, results of an immunohistochemical analysis demonstrated a loss of PTEN protein expression. While the risks of many cancers are elevated in the PTEN hamartoma tumor syndromes, association between esophageal adenocarcinoma and these syndromes has not been previously reported. Esophageal adenocarcinoma and extensive polyposis/ganglioneuromatosis could represent less common features of these syndromes, potentially correlating with this novel PTEN frameshift and early protein termination genotype. Alternatively, because simultaneous disruption of both the PTEN and TGF-β/SMAD4 pathways is associated with development of esophageal cancer in a mouse model and because SMAD4 mutations cause gastrointestinal hamartomas in juvenile polyposis syndrome, the SMAD7 mutation may represent an additional modifier of these individuals' PTEN-mutant phenotype.

miR-508 sustains phosphoinositide signalling and promotes aggressive phenotype of oesophageal squamous cell carcinoma

The strength and duration of phosphoinositide signalling from phosphatidylinositol-3-kinase (PI3K) activation to Akt is tightly balanced by phosphoinositide kinases and phosphatases. However, how phosphatase-mediated negative regulatory effects are concomitantly disrupted in cancers, which commonly exhibit constitutively activated PI3K/Akt signalling, remains undefined. Here we report that miR-508 directly suppresses multiple phosphatases, including inositol polyphosphate-5-phosphatase J (INPP5J), phosphatase and tensin homologue (PTEN) and inositol polyphosphate 4-phosphatase type I (INPP4A), resulting in constitutive activation of PI3K/Akt signalling. Furthermore, we find that overexpressing miR-508 promotes, while silencing miR-508 impairs, the aggressive phenotype of oesophageal squamous cell carcinoma (ESCC) both in vitro and in vivo. Importantly, the level of miR-508 correlates with poor survival and activated PI3K/Akt signalling in a large cohort of ESCC specimens. These findings uncover a mechanism for constitutive PI3K/Akt activation in ESCC, and support a functionally and clinically relevant epigenetic mechanism in cancer progression.

Loss of nuclear PTEN in HCV-infected human hepatocytes

Background

Hepatitis C virus (HCV) infection is a major risk factor for chronic hepatitis and hepatocellular carcinoma (HCC); however, the mechanism of HCV-mediated hepatocarcinogenesis is not well understood. Insufficiency of PTEN tumor suppressor is associated with more aggressive cancers, including HCC. We asked whether viral non-coding RNA could initiate oncogenesis in HCV infected human hepatocytes. The results presented herein suggest that loss of nuclear PTEN in HCV-infected human hepatocytes results from depletion of Transportin-2, which is a direct target of viral non-coding RNA, vmr11.

Methods

The intracellular distribution of PTEN in HCV-infected cells was monitored by immunostaining and Western blots of nuclear and cytoplasmic proteins. Effects of PTEN depletion were examined by comparing expression arrays of uninfected cells with either HCV-infected or vmr11-transfected cells. Target genes suggested by array analyses were validated by Western blot. The influence of nuclear PTEN deficiency on virus production was determined by quantitative analysis of HCV genomic RNA in culture media of infected hepatocytes.

Results

Import of PTEN to the nucleus relies on the interaction of Transportin-2 and PTEN proteins; we show that depletion of Transportin-2 by HCV infection or by the introduction of vmr11 in uninfected cells results in reduced nuclear PTEN. In turn, nuclear PTEN insufficiency correlates with increased virus production and the induction of γ-H2AX, a marker of DNA double-strand breaks and genomic instability.

Conclusion

An HCV-derived small non-coding RNA inhibits Transportin-2 and PTEN translocation to the nucleus, suggesting a direct viral role in hepatic oncogenesis.

Prognostic impact of gastrointestinal bleeding and expression of PTEN and Ki-67 on primary gastrointestinal stromal tumors

BACKGROUND

Prognostic indicators for gastrointestinal stromal tumors (GISTs) are under investigation. The latest risk classification criteria may still have room for improvement. This study aims to investigate prognostic factors for primary GISTs from three aspects, including clinicopathological parameters, immunohistochemical (IHC) expression of PTEN, and Ki-67 labeling index (LI), and attempts to find valuable predictors for the malignancy potential of primary GISTs.

METHODS

Tumor samples and clinicopathological data from 84 patients with primary GISTs after R0 resection were obtained. Immunohistochemical analysis was performed based on tissue microarray (TMA) to estimate expression of PTEN and Ki-67 in tumor cells.

RESULTS

The cut-off point of Ki-67 LI was determined as 1%, using a receiver operator characteristic test with a sensitivity of 71.7% and a specificity of 64.5%. Univariate analysis demonstrated the following factors as poor prognostic indicators for relapse-free survival (RFS) against a median follow-up of 40.25 months: gastrointestinal (GI) bleeding (P = 0.009), non-gastric tumor location (P = 0.001), large tumor size (P = 0.022), high mitotic index (P < 0.001), high cellularity (P = 0.012), tumor rupture (P = 0.013), absent or low expression of PTEN (P = 0.036), and Ki-67 LI >1% (P = 0.043). Gastrointestinal bleeding (hazard ratio, 3.85; 95% confidence interval, 1.63 to 9.10; P = 0.002) was a negative independent risk predictor in multivariate analysis, in addition to tumor size (P = 0.023), and mitotic index (P = 0.002). In addition, GI bleeding showed a good ability to predict recurrence potential, when included in our re-modified risk stratification criteria.

CONCLUSIONS

This study suggests that GI bleeding is an independent predictor of poor prognosis for RFS in primary GISTs. Expression of PTEN and Ki-67 are correlated with high risk potential and may predict early recurrence in univariate analysis.

Altered Expression of PTEN and Its Major Regulator MicroRNA-21 in Pulmonary Neuroendocrine Tumors

Background

Phosphatase and tensin homolog on chromosome ten (PTEN) is one of the most frequently inactivated tumor suppressors in various tumor types. MicroRNA-21 (miR-21) may affect tumor progression by post-transcriptional repression of expression of tumor suppressors, such as PTEN. This study was conducted to evaluate the significance of PTEN expression in pulmonary neuroendocrine (NE) tumors and to analyze the relationship between PTEN and miR-21 expressions.

Methods

Expressions of PTEN and miR-21 were investigated by immunohistochemistry and real time reverse transcription-polymerase chain reaction, respectively, in 75 resected pulmonary NE tumors (23 typical carcinoids [TCs], nine atypical carcinoids [ACs], 22 large cell NE carcinomas [LCNECs], and 21 small cell lung carcinomas [SCLCs]).

Results

Loss of PTEN expression was observed in four of 23 TCs (17.4%), four of nine ACs (44.4%), 16 of 22 LCNECs (72.7%) and nine of 21 SCLCs (42.9%) (p=.025). The expression level of miR-21 was significantly higher in high-grade NE carcinomas than in carcinoid tumors (p<.001). PTEN expression was inversely correlated with miR-21 expression (p<.001).

Conclusions

This study suggests that aberrant expression of PTEN in relation to miR-21 may represent an important step in the development and progression of pulmonary NE tumors.

PIK3CA mutations frequently coexist with EGFR/KRAS mutations in non-small cell lung cancer and suggest poor prognosis in EGFR/KRAS wildtype subgroup

PURPOSE

PIK3CA gene encoding a catalytic subunit of the phosphatidylinositol-3-kinase (PI3K) is mutated and/or amplified in various neoplasia, including lung cancer. Here we investigated PIK3CA gene alterations, the expression of core components of PI3K pathway, and evaluated their clinical importance in non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

Oncogenic mutations/rearrangements in PIK3CA, EGFR, KRAS, HER2, BRAF, AKT1 and ALK genes were detected in tumors from 1117 patients with NSCLC. PIK3CA gene copy number was examined by fluorescent in situ hybridization and the expression of PI3K p110 subunit alpha (PI3K p110α), p-Akt, mTOR, PTEN was determined by immunohistochemistry in PIK3CA mutant cases and 108 patients without PIK3CA mutation.

RESULTS

PIK3CA mutation was found in 3.9% of squamous cell carcinoma and 2.7% of adenocarcinoma. Among 34 PIK3CA mutant cases, 17 tumors harbored concurrent EGFR mutations and 4 had KRAS mutations. PIK3CA mutation was significantly associated with high expression of PI3K p110α (p<0.0001), p-Akt (p = 0.024) and mTOR (p = 0.001), but not correlated with PIK3CA amplification (p = 0.463). Patients with single PIK3CA mutation had shorter overall survival than those with PIK3CA-EGFR/KRAS co-mutation or wildtype PIK3CA (p = 0.004). A significantly worse survival was also found in patients with PIK3CA mutations than those without PIK3CA mutations in the EGFR/KRAS wildtype subgroup (p = 0.043).

CONCLUSIONS

PIK3CA mutations frequently coexist with EGFR/KRAS mutations. The poor prognosis of patients with single PIK3CA mutation in NSCLC and the prognostic value of PIK3CA mutation in EGFR/KRAS wildtype subgroup suggest the distinct mutation status of PIK3CA gene should be determined for individual therapeutic strategies in NSCLC.

Cross Talk between Two Antioxidant Systems, Thioredoxin and DJ-1: Consequences for Cancer

Oxidative stress, which is associated with an increased concentration of reactive oxygen species (ROS), is involved in the pathogenesis of numerous diseases including cancer. In response to increased ROS levels, cellular antioxidant molecules such as thioredoxin, peroxiredoxins, glutaredoxins, DJ-1, and superoxide dismutases are upregulated to counteract the detrimental effect of ROS. However, cancer cells take advantage of upregulated antioxidant molecules for protection against ROS-induced cell damage. This review focuses on two antioxidant systems, Thioredoxin and DJ-1, which are upregulated in many human cancer types, correlating with tumour proliferation, survival, and chemo-resistance. Thus, both of these antioxidant molecules serve as potential molecular targets to treat cancer. However, targeting one of these antioxidants alone may not be an effective anti-cancer therapy. Both of these antioxidant molecules are interlinked and act on similar downstream targets such as NF-κβ, PTEN, and Nrf2 to exert cytoprotection. Inhibiting either thioredoxin or DJ-1 alone may allow the other antioxidant to activate downstream signalling cascades leading to tumour cell survival and proliferation. Targeting both thioredoxin and DJ-1 in conjunction may completely shut down the antioxidant defence system regulated by these molecules. This review focuses on the cross-talk between thioredoxin and DJ-1 and highlights the importance and consequences of targeting thioredoxin and DJ-1 together to develop an effective anti-cancer therapeutic strategy.

PTEN, Longevity and Age-Related Diseases

Since the discovery of PTEN, this protein has been shown to be an effective suppressor of cancer and a contributor to longevity. This report will review, in depth, the associations between PTEN and other molecules, its mutations and regulations in order to present how PTEN can be used to increase longevity. This report will collect recent research of PTEN and use this to discuss PTEN’s role in caloric restriction, antioxidative defense of DNA-damage and the role it plays in suppressing tumors. The report will also discuss that variety of ways that PTEN can be compromised, through mutations, complete loss of alleles and its main antagonist, the PI3K/AKT pathway.

Loss of phosphatase and tensin homolog protein expression is an independent poor prognostic marker in lung adenocarcinoma

INTRODUCTION

Phosphatase and tensin homolog (PTEN) has been established as a tumor suppressor gene with an important role in regulating the phosphatidylinositol-3-kinase/AKT antiapoptotic and survival pathway. The prognostic role of PTEN in non-small-cell lung carcinoma has not been evaluated completely in the context of other molecular information.

METHODS

Tissue microarrays containing 152 resected non-small-cell lung cancer specimens were used to investigate PTEN and p53 by immunohistochemistry and PTEN by fluorescence in situ hybridization. DNA was isolated and subjected to mutational profiling using the Sequenom Oncocarta v1.0 panel. Clinicopathological features were correlated with PTEN expression, gene copy number, and mutation status.

RESULTS

PTEN staining was absent in 63 (41.4%) of the cases. Significantly more squamous cell carcinomas compared with adenocarcinomas demonstrated loss of (negative) PTEN staining (26 of 44 [59%] versus 32 of 94 [34%]; p = 0.009). PTEN gene copy deletion was present in only seven of 124 evaluable cases (5.6%); all deleted cases were immunohistochemistry negative. In univariate and multivariate (MV) analyses adjusted for sex, age, histology, and stage, loss of PTEN protein expression was associated with significantly shorter disease-free survival (MV hazard ratio: 1.78, 95% confidence interval: 1.01-3.14, p = 0.048), whereas no significant associations were seen with p53 or KRAS and epidermal growth factor receptor (EGFR) mutation status. Importantly, the prognostic value of absent PTEN staining was limited to adenocarcinomas, with MV disease-free survival hazard ratio of 2.68 (95% confidence interval: 1.35-5.32, p = 0.005), whereas no such association was seen in squamous cell carcinomas.

CONCLUSION

Absence of PTEN protein expression is an independent prognostic marker in early-stage resected lung adenocarcinoma.

Loss and reduced expression of PTEN correlate with advanced-stage gastric carcinoma

Phosphatase and tensin homolog (PTEN) is a tumor suppressor involved in multiple cell processes. To investigate the role of PTEN in the development of gastric carcinoma, we determined the expression pattern of PTEN in primary gastric carcinoma and in paired adjacent non-neoplastic tissue. We also determined the correlation of PTEN expression with clinicopathological characteristics and patient survival. Overall, 159 gastric carcinomas and 151 paired adjacent non-neoplastic tissues were used in the present study. PTEN expression was determined using tissue microarrays and immunohistochemistry. The clinical sensitivity and specificity of PTEN expression were calculated using receiver operator characteristic curves. Results showed that the loss of cytoplasmic PTEN was significantly more frequent in carcinoma tissue compared with adjacent non-neoplastic tissue (62 vs. 5%, respectively; P<0.0001). PTEN expression was markedly downregulated in carcinoma tissues compared with adjacent non-neoplastic tissues. The loss of cytoplasmic PTEN expression was positively correlated with histological stage (P=0.016). The loss of nuclear or total PTEN, and downregulation of total PTEN expression, was significantly different between American Joint Committee on Cancer tumors of stage I and stages II-IV. A low cytoplasmic or total PTEN expression showed high clinical sensitivity and specificity for gastric carcinoma. However, PTEN expression was not significantly associated with overall or 3-year survival rates. The findings of the present study indicated that PTEN expression may be a molecular diagnostic marker for gastric cancer. Thus, the loss or reduced expression of PTEN potentially correlate with advanced stages of gastric carcinoma.

Inhibition of microRNA-21 increases radiosensitivity of esophageal cancer cells through phosphatase and tensin homolog deleted on chromosome 10 activation

The radioresistance of esophageal squamous cell carcinoma is a great obstacle to treatment. Although it has been demonstrated that microRNA-21 (miR-21) can act as an 'oncogene' in esophageal squamous cell carcinoma, its role in radioresistance remains unexplored. The aims of this study were to investigate the role of miR-21 in esophageal squamous carcinoma cells' radioresistance and to identify the possible mechanism. The relatively radioresistant esophageal squamous cancer TE-1 cells (TE-R60) was established by fractionated irradiation. By lentiviral transduction with miRZip-21, the miR-21 expression in TE-1 cells was stably downregulated, which was renamed as 'anti-miR-21 TE-1 cells.' The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) was knocked down in anti-miR-21 TE-1 cells through short interfering RNA. The expression level of miR-21 and PTEN messenger RNA were measured by quantitative real-time reverse transcription polymerase chain reaction or reverse transcription polymerase chain reaction. The expression level of PTEN, phospho-Akt, and Akt protein were detected by Western blot. Clongenic assay was used to analyze the cells' radiosensitivity. miR-21 was overexpressed, and PTEN was suppressed in established radioresistant TE-R60 cells compared with the parent cells (1.3-fold and 70.83%). The inhibition of miR-21 significantly increased the cells' radiosensitivity (P < 0.05) and the PTEN protein expression (2.3-fold) in TE-1 cells. In addition, phospho-Akt protein, downstream target of PTEN, reduced significantly in anti-miR-21 TE-1 cells. Knockdown of PTEN in anti-miR-21 TE-1 cells could abrogate the miR-21 inhibition-induced radiosensitization (P < 0.05). Inhibition of miR-21 increased radiosensitivity of esophageal cancer TE-1 cells, and this effect was possibly through the activation of PTEN. Inhibition of miR-21 may form a novel therapeutic strategy to increase the radiosensitivity of esophageal cancer.

PTEN gene: a model for genetic diseases in dermatology

PTEN gene is considered one of the most mutated tumor suppressor genes in human cancer, and it's likely to become the first one in the near future. Since 1997, its involvement in tumor suppression has smoothly increased, up to the current importance. Germline mutations of PTEN cause the PTEN hamartoma tumor syndrome (PHTS), which include the past-called Cowden, Bannayan-Riley-Ruvalcaba, Proteus, Proteus-like, and Lhermitte-Duclos syndromes. Somatic mutations of PTEN have been observed in glioblastoma, prostate cancer, and brest cancer cell lines, quoting only the first tissues where the involvement has been proven. The negative regulation of cell interactions with the extracellular matrix could be the way PTEN phosphatase acts as a tumor suppressor. PTEN gene plays an essential role in human development. A recent model sees PTEN function as a stepwise gradation, which can be impaired not only by heterozygous mutations and homozygous losses, but also by other molecular mechanisms, such as transcriptional regression, epigenetic silencing, regulation by microRNAs, posttranslational modification, and aberrant localization. The involvement of PTEN function in melanoma and multistage skin carcinogenesis, with its implication in cancer treatment, and the role of front office in diagnosing PHTS are the main reasons why the dermatologist should know about PTEN.

Nongenomic Mechanisms of PTEN Regulation

A large amount of data supports the view that PTEN is a bona fide tumor suppressor gene. However, recent evidence suggests that derailment of cellular localization and expression levels of functional nonmutated PTEN is a determining force in inducing abnormal cellular and tissue outcomes. As the cellular mechanisms that regulate normal PTEN enzymatic activity resolve, it is evident that deregulation of these mechanisms can alter cellular processes and tissue architecture and ultimately lead to oncogenic transformation. Here we discuss PTEN ubiquitination, PTEN complex formation with components of the adherens junction, PTEN nuclear localization, and microRNA regulation of PTEN as essential regulatory mechanisms that determine PTEN function independent of gene mutations and epigenetic events.

Association of genetic polymorphisms in MDM2, PTEN and P53 with risk of esophageal squamous cell carcinoma

Genetic variations in MDM2, PTEN and P53 might be involved in cancer susceptibility. To assess the contribution of polymorphisms in these three genes to the risk of esophageal squamous cell carcinoma (ESCC) in a Chinese population, we genotyped MDM2 T309G, Del1518, PTEN rs701848, rs2735343 and P53 Arg72Pro polymorphisms using PCR-restriction fragment length polymorphism analysis in 226 ESCC cases and 226 cancer-free controls. Here we showed that the risk of ESCC was elevated in subjects with any of the variant genotypes of PTEN rs2735343 and P53 Arg72Pro polymorphisms, but not any genotype of MDM2 or PTEN rs701848. Moreover, multiplicative interactions were observed between PTEN rs2735343 and P53 Arg72Pro or smoking status on risk of ESCC. Our study firstly indicated that PTEN rs2735343 might be a susceptibility factor for ESCC and reaffirmed the role of P53 Arg72Pro in ESCC in this Chinese population, but did not replicate the positive association between MDM2 T309G and ESCC found previously.

The multifaceted roles of USP7: new therapeutic opportunities

The deubiquitylating enzyme USP7 (HAUSP) sits at a critical node regulating the activities of numerous proteins broadly characterized as tumor suppressors, DNA repair proteins, immune responders, viral proteins, and epigenetic modulators. Aberrant USP7 activity may promote oncogenesis and viral disease making it a compelling target for therapeutic intervention. Disclosed drug discovery programs have identified inhibitors of USP7 such as P005091 with cellular proof of concept and anti-proliferative activity in cancer models. Taken together, USP7 inhibitors hold promise as a new strategy for the treatment of disease.

The role of Pea3 group transcription factors in esophageal squamous cell carcinoma

The transcription factors Pea3, Erm, and Er81 can promote cancer initiation and progression in various types of solid tumors. However, their role in esophageal squamous cell carcinoma (ESCC) has not been elucidated. In this study, we found that the expression levels of Pea3 and Erm, but not that of Er81, were significantly higher in ESCC compared with nontumor esophageal epithelium. A high level of Pea3 expression was significantly correlated with a shorter overall survival in a cohort of 81 patients with ESCC and the subgroup with N1 stage tumor (Wilcoxon-Gehan test, P = 0.016 and P = 0.001, respectively). Pea3 was overexpressed in seven ESCC cell lines compared with two immortalized esophageal cell lines. Pea3 knockdown reduced cell proliferation and suppressed nonadherent growth, migration, and invasion in ESCC cells in vitro. In addition, Pea3 knockdown in ESCC cells resulted in a down-regulation of phospho-Akt and matrix metalloproteinase 13, whereas a significant positive correlation in the expression levels was observed between Pea3 and phospho-Akt (r = 0.281, P < 0.013) and between Pea3 and matrix metalloproteinase 13 in the human specimens (r = 0.462, P < 0.001). Moreover, Pea3 modulated the sensitivity of EC109 cells to doxorubicin, probably via reduced activity of the phosphatidylinositol 3-kinase-Akt-mammalian target of Rapamycin complex 1 pathway on Pea3 knockdown. In conclusion, our results suggest that Pea3 plays an important role in the progression of ESCC.

Clinical significance of expression of PTEN, Akt and pAkt in hepatocellular carcinoma

AIM: To explore the expression of phosphatase and tensin homology deleted on chromosome ten (PTEN), Akt and pAkt proteins in hepatocellular carcinoma (HCC) and to elucidate their clinical significance.

METHODS: Immunohistochemical analysis was performed to detect the expression of PTEN, Akt and pAkt proteins in 78 specimens of hepatocellular carcinoma and 21 specimens of normal liver tissues. The relationship of their expression with clinicopathological and prognostic parameters was analyzed.

RESULTS: The rate of PTEN overexpression was significantly lower in HCC than in normal liver tissue (42.3% vs 90.5%, P < 0.05), while the rates of Akt and pAkt overexpression were significantly higher in HCC than in normal liver tissue (66.7% vs 33.3%; 43.6% vs 9.5%, both P < 0.05). PTEN expression was correlated with tumor size, cancer embolus of the portal vein, tumor invasion, lymph node metastasis and TNM stage. Akt and pAkt expression was correlated with tumor size, invasion, lymph node metastasis and TNM stage. PTEN expression was negatively correlated with Akt (r = -0.385, P = 0.000) and pAkt (r =- 0.334, P = 0.003) expression in HCC. Patients with low PTEN expression or high Akt and pAkt expression had a significantly worse survival time than those with high PTEN expression or low Akt and pAkt expression (P = 0.000). A multivariate analysis based on the COX regression model demonstrated that TNM stage and pAkt expression were independent prognostic factors for HCC.

CONCLUSION: The expression of PTEN, Akt and pAkt proteins is closely related to the malignant biological behavior of HCC. pAkt can be used as a key factor for predicting prognosis in HCC patients.