Cellular prion protein contributes to LS 174T colon cancer cell carcinogenesis by increasing invasiveness and resistance against doxorubicin-induced apoptosis

High cellular prion protein expression in cholangiocarcinoma: A marker for early postoperative recurrence and unfavorable prognosis

BACKGROUND

The cellular prion protein (PrPC), traditionally associated with neurodegenerative disorders, plays an important role in cancer progression and metastasis by inhibiting apoptosis.

AIM

To investigate the influence of PrPC expression in cholangiocarcinoma (CCA) on patient outcomes following surgical resection.

METHODS

Patients who underwent curative surgical resection for either intrahepatic or hilar CCA were enrolled in this retrospective study. Based on the immunohistochemical staining results of the surgical specimens, patients were categorized into two groups: The low PrPC group (negative or 1+) and the high PrPC group (2+ or 3+). Survival analyses, including overall survival and recurrence-free survival, were conducted using the Kaplan-Meier method and compared using the log-rank test.

RESULTS

In total, seventy-six patients diagnosed with CCA (39 with intrahepatic and 37 with hilar CCA) underwent curative hepatectomy from January 2011 to November 2021. Among these patients, 38 (50%) demonstrated high PrPC expression, whereas the remaining 38 (50%) showed low expression of PrPC. During a median follow-up period of 31.2 months (range: 1 to 137 months), the high PrPC group had a significantly shorter median overall survival than the low PrPC group (40.4 months vs 137.9 months, respectively; P = 0.041). Moreover, the high PrPC group had a significantly shorter median recurrence-free survival than the low PrPC group (13.3 months vs 23.8 months, respectively; P = 0.026).

CONCLUSION

PrPC expression is significantly associated with early recurrence and decreased survival period in CCA patients following surgical resection. Thus, PrPC may be used as a prognostic factor in treatment planning.

miR-193b-3p suppresses lung cancer cell migration and invasion through PRNP targeting

BACKGROUND

Tumor metastasis is responsible for approximately 90% of mortality in lung cancer. Understanding the molecular mechanisms of lung cancer metastasis is crucial for developing new treatment strategies. Cellular prion protein (PrPc), encoded by PRNP gene, was previously found to enhance lung cancer invasiveness. However, research on the post-transcriptional regulation of PRNP remains limited.

METHODS

Dual-luciferase reporter assays identified miRNAs targeting the PRNP 3'-UTR, and RNA immunoprecipitation (RIP) confirmed the interaction between miR-193b-3p and PRNP mRNA. Promoter deletions and chromatin immunoprecipitation (ChIP) assays established c-Jun as a transcriptional repressor of miR-193b-3p. Functional validation of the c-Jun-miR-193b-3p-PrPc axis was conducted using transwell assays, LNA-in situ hybridization, RT-PCR, Western blot, and immunohistochemistry. Subcutaneous mouse xenograft models assessed the anti-tumor effects of miR-193b-3p in vivo.

RESULTS

We demonstrated that miR-193b-3p downregulates PrPc expression by directly targeting the 3'-UTR of PRNP. Overexpression of miR-193b-3p significantly suppressed PRNP expression at both mRNA and protein levels, and reduced lung cancer cell migration, invasion and proliferation, which was reversed by PrPc overexpression. Conversely, miR-193b-3p silencing enhanced PRNP expression as well as those oncogenic properties, which were mitigated by PRNP knockdown. Spearman correlation analysis revealed a significant negative association between miR-193b-3p and PrPc expression in lung cancer tissues (p = 0.017), and Kaplan-Meier survival analysis demonstrated that high PrPc (p = 0.039) or low miR-193b-3p (p = 0.027) expression correlated with poorer overall survival. Intra-tumoral injection of the miR-193b-3p mimic in mouse xenograft models significantly reduced tumor volume. In addition, c-Jun was identified as a transcriptional repressor of miR-193b-3p. Functional studies revealed that c-Jun knockdown inhibited lung cancer cell migration, invasion, and proliferation, effects that were reversed by either PrPc overexpression or miR-193b-3p inhibitor treatment. A significant association between PrPc and c-Jun expression in lung cancer tissues (p = 0.004) was observed. High expression of PrPc and/or c-Jun was found to be associated with poor overall survival of patients (p < 0.05).

CONCLUSIONS

This study is the first to uncover a novel regulatory pathway where c-Jun acts as a transcriptional repressor of miR-193b-3p, leading to PRNP upregulation, which promotes lung cancer migration and invasion. This previously unrecognized c-Jun-miR-193b-3p-PrPc axis also provides valuable insights for the potential development of new therapeutic strategies against lung cancer metastasis through RNA-targeting technology.

The expression of pro-prion, a transmembrane isoform of the prion protein, leads to the constitutive activation of the canonical Wnt/β-catenin pathway to sustain the stem-like phenotype of human glioblastoma cells

BACKGROUND

Cellular prion protein (PrPC) is a widely expressed membrane-anchored glycoprotein, which has been associated with the development and progression of several types of human malignancies, controlling cancer stem cell activity. However, the different molecular mechanisms regulated by PrPC in normal and tumor cells have not been characterized yet.

METHODS

To assess the role of PrPC in patient-derived glioblastoma stem cell (GSC)-enriched cultures, we generated cell lines in which PrPC was either overexpressed or down-regulated and investigated, in 2D and 3D cultures, its role in cell proliferation, migration, and invasion. We evaluated the role of PrPC in supporting GSC stemness and the intracellular signaling involved using qRT-PCR, immunocytofluorescence, and Western blot.

RESULTS

Stable PrPC down-regulation leads to a significant reduction of GSC proliferation, migration, and invasiveness. These effects were associated with the inhibition of the expression of stemness genes and overexpression of differentiation markers. At molecular level PrPC down-regulation caused a significant inhibition of Wnt/β-catenin pathway, through a reduced expression of Wnt and Frizzled ligand/receptor subtypes, resulting in the inhibition of β-catenin transcriptional activity,  as demonstrated by the reduced expression of its target genes. The specificity of PrPC in these effects was demonstrated by rescuing the phenotype and the biological activity of PrPC down-regulated GSCs by re-expressing the protein. To get insights into the distinct mechanisms by which PrPC regulates proliferation in GSCs, but not in normal astrocytes, we analyzed structural features of PrPC in glioma stem cells and astrocytes using Western blot and immunofluorescence techniques. Using Pi-PLC, an enzyme that cleaves GPI anchors, we show that, in GSCs, PrP is retained within the plasma membrane in an immature Pro-PrP isoform whereas in astrocytes, it is expressed in its mature PrPC form, anchored on the extracellular face of the plasma membrane.

CONCLUSIONS

The persistence of Pro-PrP in GSCs is an altered cellular mechanism responsible of the aberrant, constitutive activation of Wnt/β-catenin pathway, which contributes to glioblastoma malignant features. Thus, the activity of Pro-PrP may represent a targetable vulnerability in glioblastoma cells, offering a novel approach for differentiating and eradicating glioblastoma stem cells.

PRNP is a pan-cancer prognostic and immunity-related to EMT in colorectal cancer

Background

Prion protein gene (PRNP) is widely expressed in a variety of tissues. Although the roles of PRNP in several cancers have been investigated, no pan-cancer analysis has revealed its relationship with tumorigenesis and immunity.

Methods

Comprehensive analyses were conducted on The Cancer Genome Atlas (TCGA) Pan-Cancer dataset from the University of California Santa Cruz (UCSC) database to determine the expression of PRNP and its potential prognostic implications. Immune infiltration and enrichment analysis methods were used to ascertain correlations between PRNP expression levels, tumor immunity, and immunotherapy. Additionally, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) methods were employed to examine possible signaling pathways involving PRNP. In vitro experiments using CCK-8 assay, Wound healing assay, and Transwell assay to detect the effect of Cellular prion protein (PrPC) on proliferation, migration, and invasion in colorectal cancer (CRC) cells. The expression levels of epithelial-mesenchymal transition (EMT)-related proteins (N-cadherin, E-cadherin, Vimentin and Snail) were detected by western blot.

Results

Among most cancer types, PRNP is expressed at high levels, which is linked to the prognosis of patients. PRNP expression is strongly associated with immune infiltrating cells, immunosuppressive cell infiltration and immune checkpoint molecules. In addition to tumor mutation burden (TMB), substantial correlations are detected between PRNP expression and microsatellite instability (MSI) in several cancers. In vitro cell studies inferred that PrPC enhanced the proliferation, migration, invasion, and EMT of CRC cells.

Conclusion

PRNP serves as an immune-related prognostic marker that holds promise for predicting outcomes related to CRC immunotherapy while simultaneously promoting cell proliferation, migration, and invasion activities. Furthermore, it potentially plays a role in governing EMT regulation within CRC.

β-eudesmol inhibits cell proliferation and induces ferroptosis via regulating MAPK signaling pathway in breast cancer

The aim of this study was to explore the influences and underlying mechanisms of β-eudesmol on breast cancer (BC). Different concentrations of β-eudesmol (0, 10, 20, and 40 μM) were taken to treat BC cells. Cell Counting Kit-8, colony formation assay, and flow cytometry were performed to evaluate the influences of β-eudesmol on cell viability, proliferation, and apoptosis. To assess the influences of β-eudesmol on cell ferroptosis, the change of ROS, SOD, MDA, and intracellular iron and Fe2+ were determined. The protein changes of apoptosis, ferroptosis, and MAPK pathway (Bcl-2, Bax, cleaved caspase-3, SLC7A11, GPX4, SLC40A1, Transferrin, MEK1, and ERK1/2) were checked utilizing Western blot. In a concentration-dependent manner, β-eudesmol restrained cell viability and proliferation. β-eudesmol promoted cell apoptosis, as evidenced by the decline level of Bcl-2 and the raised level of Bax and cleaved caspase-3. β-eudesmol enhanced the level of ROS, MDA, iron, Fe2+, and Transferrin, and lessened SOD activity and the protein expression of SLC7A11, GPX4, SLC40A1, MEK1, and ERK1/2. Moreover, ferroptosis inhibitor Fer-1 and MEK1 overexpression both reversed the changes on cell proliferation, apoptosis, and ferroptosis induced by β-eudesmol. β-eudesmol inhibited cell proliferation and promoted cell apoptosis and ferroptosis via regulating MAPK pathway in BC.

The Multifaceted Functions of Prion Protein (PrPC) in Cancer

The cellular prion protein (PrPC) is a glycoprotein anchored to the cell surface by glycosylphosphatidylinositol (GPI). PrPC is expressed both in the brain and in peripheral tissues. Investigations on PrPC's functions revealed its direct involvement in neurodegenerative and prion diseases, as well as in various physiological processes such as anti-oxidative functions, copper homeostasis, trans-membrane signaling, and cell adhesion. Recent findings have revealed the ectopic expression of PrPC in various cancers including gastric, melanoma, breast, colorectal, pancreatic, as well as rare cancers, where PrPC promotes cellular migration and invasion, tumor growth, and metastasis. Through its downstream signaling, PrPC has also been reported to be involved in resistance to chemotherapy and tumor cell apoptosis. This review summarizes the variance of expression of PrPC in different types of cancers and discusses its roles in their development and progression, as well as its use as a potential target to treat such cancers.

Roles of anoikis in colorectal cancer therapy and the assessment of anoikis-regulatory molecules as therapeutic targets

Colorectal cancer (CRC) is a deadly malignancy and therapeutic approaches for CRC are evolving every day. Anoikis is a key mechanism for programmed cell death of cancer cells that undergo anchorage-independent growth at a different matrix than the one which is expected. Yet, anoikis is a less studied mechanism of cell death in comparison to other mechanisms such as apoptosis. Relating to this, resistance to anoikis among cancer cells remains critical for improved metastasis and survival in a new environment evading anoikis. Since CRC cells have the ability to metastasize from proximal sites to secondary organs such as liver and promote cancer in those distant sites, a clear knowledge of the mechanisms essential for anchorage-independent growth and subsequent metastasis is necessary to counteract CRC progression and spread. Therefore, the identification of novel drug candidates and studying the roles of anoikis in assisting CRC therapy using such drugs can prevent anchorage-independent cancer cell growth. Additionally, the identification of novel biomarkers or therapeutic targets seems essential for implementing superior therapy, impeding relapse among malignant cells and improving the survival rate of clinical patients. As there are no reviews published on this topic till date, anoikis as a mechanism of cell death and its therapeutic roles in CRC are discussed in this review. In addition, several molecules were identified as therapeutic targets for CRC.

Second Sphere Interactions in Amyloidogenic Diseases

Amyloids are protein aggregates bearing a highly ordered cross β structural motif, which may be functional but are mostly pathogenic. Their formation, deposition in tissues and consequent organ dysfunction is the central event in amyloidogenic diseases. Such protein aggregation may be brought about by conformational changes, and much attention has been directed toward factors like metal binding, post-translational modifications, mutations of protein etc., which eventually affect the reactivity and cytotoxicity of the associated proteins. Over the past decade, a global effort from different groups working on these misfolded/unfolded proteins/peptides has revealed that the amino acid residues in the second coordination sphere of the active sites of amyloidogenic proteins/peptides cause changes in H-bonding pattern or protein-protein interactions, which dramatically alter the structure and reactivity of these proteins/peptides. These second sphere effects not only determine the binding of transition metals and cofactors, which define the pathology of some of these diseases, but also change the mechanism of redox reactions catalyzed by these proteins/peptides and form the basis of oxidative damage associated with these amyloidogenic diseases. The present review seeks to discuss such second sphere modifications and their ramifications in the etiopathology of some representative amyloidogenic diseases like Alzheimer's disease (AD), type 2 diabetes mellitus (T2Dm), Parkinson's disease (PD), Huntington's disease (HD), and prion diseases.

Melatonin: Regulation of Prion Protein Phase Separation in Cancer Multidrug Resistance

The unique ability to adapt and thrive in inhospitable, stressful tumor microenvironments (TME) also renders cancer cells resistant to traditional chemotherapeutic treatments and/or novel pharmaceuticals. Cancer cells exhibit extensive metabolic alterations involving hypoxia, accelerated glycolysis, oxidative stress, and increased extracellular ATP that may activate ancient, conserved prion adaptive response strategies that exacerbate multidrug resistance (MDR) by exploiting cellular stress to increase cancer metastatic potential and stemness, balance proliferation and differentiation, and amplify resistance to apoptosis. The regulation of prions in MDR is further complicated by important, putative physiological functions of ligand-binding and signal transduction. Melatonin is capable of both enhancing physiological functions and inhibiting oncogenic properties of prion proteins. Through regulation of phase separation of the prion N-terminal domain which targets and interacts with lipid rafts, melatonin may prevent conformational changes that can result in aggregation and/or conversion to pathological, infectious isoforms. As a cancer therapy adjuvant, melatonin could modulate TME oxidative stress levels and hypoxia, reverse pH gradient changes, reduce lipid peroxidation, and protect lipid raft compositions to suppress prion-mediated, non-Mendelian, heritable, but often reversible epigenetic adaptations that facilitate cancer heterogeneity, stemness, metastasis, and drug resistance. This review examines some of the mechanisms that may balance physiological and pathological effects of prions and prion-like proteins achieved through the synergistic use of melatonin to ameliorate MDR, which remains a challenge in cancer treatment.

Detailing the ultrastructure's increase of prion protein in pancreatic adenocarcinoma

BACKGROUND

Recent evidences have shown a relationship between prion protein (PrPc) expression and pancreatic ductal adenocarcinoma (PDAC). Indeed, PrPc could be one of the markers explaining the aggressiveness of this tumor. However, studies investigating the specific compartmentalization of increased PrPc expression within PDAC cells are lacking, as well as a correlation between ultrastructural evidence, ultrastructural morphometry of PrPc protein and clinical data. These data, as well as the quantitative stoichiometry of this protein detected by immuno-gold, provide a significant advancement in understanding the biology of disease and the outcome of surgical resection.

AIM

To analyze quantitative stoichiometry and compartmentalization of PrPc in PDAC cells and to correlate its presence with prognostic data.

METHODS

Between June 2018 and December 2020, samples from pancreatic tissues of 45 patients treated with pancreatic resection for a preoperative suspicion of PDAC at our Institution were collected. When the frozen section excluded a PDAC diagnosis, or the nodules were too small for adequate sampling, patients were ruled out from the present study. Western blotting was used to detect, quantify and compare the expression of PrPc in PDAC and control tissues, such as those of non-affected neighboring pancreatic tissue of the same patient. To quantify the increase of PrPc and to detect the subcellular compartmentalization of PrPc within PDAC cells, immuno-gold stoichiometry within specific cell compartments was analyzed with electron microscopy. Finally, an analysis of quantitative PrPc expression according to prognostic data, such as cancer stage, recurrence of the disease at 12 mo after surgery and recurrence during adjuvant chemotherapy was made.

RESULTS

The amount of PrPc within specimen from 38 out of 45 patients was determined by semi-quantitative analysis by using Western blotting, which indicates that PrPc increases almost three-fold in tumor pancreatic tissue compared with healthy pancreatic regions [242.41 ± 28.36 optical density (OD) vs 95 ± 17.40 OD, P < 0.0001]. Quantitative morphometry carried out by using immuno-gold detection at transmission electron microscopy confirms an increased PrPc expression in PDAC ductal cells of all patients and allows to detect a specific compartmentalization of PrPc within tumor cells. In particular, the number of immuno-gold particles of PrPc was significantly higher in PDAC cells respect to controls, when considering the whole cell (19.8 ± 0.79 particles vs 9.44 ± 0.45, P < 0.0001). Remarkably, considering PDAC cells, the increase of PrPc was higher in the nucleus than cytosol of tumor cells, which indicates a shift in PrPc compartmentalization within tumor cells. In fact, the increase of immuno-gold within nuclear compartment exceeds at large the augment of PrPc which was detected in the cytosol (nucleus: 12.88 ± 0.59 particles vs 5.12 ± 0.32, P < 0.0001; cytosol: 7.74. ± 0.44 particles vs 4.3 ± 0.24, P < 0.0001). In order to analyze the prognostic impact of PrPc, we found a correlation between PrPc expression and cancer stage according to pathology results, with a significantly higher expression of PrPc for advanced stages. Moreover, 24 patients with a mean follow-up of 16.8 mo were considered. Immuno-blot analysis revealed a significantly higher expression of PrPc in patients with disease recurrence at 12 mo after radical surgery (360.71 ± 69.01 OD vs 170.23 ± 23.06 OD, P = 0.023), also in the subgroup of patients treated with adjuvant CT (368.36 ± 79.26 OD in the recurrence group vs 162.86 ± 24.16 OD, P = 0.028), which indicates a correlation with a higher chemo-resistance.

CONCLUSION

Expression of PrPc is significantly higher in PDAC cells compared with control, with the protein mainly placed in the nucleus. Preliminary clinical data confirm the correlation with a poorer prognosis.

The Cellular Prion Protein and the Hallmarks of Cancer

Simple Summary

The cellular prion protein PrP^C is best known for its involvement, under its pathogenic isoform, in a group of neurodegenerative diseases. Notwithstanding, an emerging role for PrP^C in various cancer-associated processes has attracted increasing attention over recent years. PrP^C is overexpressed in diverse types of solid cancers and has been incriminated in various aspects of cancer biology, most notably proliferation, migration, invasion and metastasis, as well as resistance to cytotoxic agents. This article aims to provide a comprehensive overview of the current knowledge of PrP^C with respect to the hallmarks of cancer, a reference framework encompassing the major characteristics of cancer cells.

Abstract

Beyond its causal involvement in a group of neurodegenerative diseases known as Transmissible Spongiform Encephalopathies, the cellular prion protein PrP^C is now taking centre stage as an important contributor to cancer progression in various types of solid tumours. The prion cancer research field has progressively expanded in the last few years and has yielded consistent evidence for an involvement of PrP^C in cancer cell proliferation, migration and invasion, therapeutic resistance and cancer stem cell properties. Most recent data have uncovered new facets of the biology of PrP^C in cancer, ranging from its control on enzymes involved in immune tolerance to its radio-protective activity, by way of promoting angiogenesis. In the present review, we aim to summarise the body of literature dedicated to the study of PrP^C in relation to cancer from the perspective of the hallmarks of cancer, the reference framework defined by Hanahan and Weinberg.

The Role of Cellular Prion Protein in Cancer Biology: A Potential Therapeutic Target

Prion protein has two isoforms including cellular prion protein (PrP^C) and scrapie prion protein (PrP^Sc). PrP^Sc is the pathological aggregated form of prion protein and it plays an important role in neurodegenerative diseases. PrP^C is a glycosylphosphatidylinositol (GPI)-anchored protein that can attach to a membrane. Its expression begins at embryogenesis and reaches the highest level in adulthood. PrP^C is expressed in the neurons of the nervous system as well as other peripheral organs. Studies in recent years have disclosed the involvement of PrP^C in various aspects of cancer biology. In this review, we provide an overview of the current understanding of the roles of PrP^C in proliferation, cell survival, invasion/metastasis, and stem cells of cancer cells, as well as its role as a potential therapeutic target.

The Role of Cellular Prion Protein in Promoting Stemness and Differentiation in Cancer

Cellular prion protein (PrPC) is seminal to modulate a variety of baseline cell functions to grant homeostasis. The classic role of such a protein was defined as a chaperone-like molecule being able to rescue cell survival. Nonetheless, PrPC also represents the precursor of the deleterious misfolded variant known as scrapie prion protein (PrPSc). This variant is detrimental in a variety of prion disorders. This multi-faceted role of PrP is greatly increased by recent findings showing how PrPC in its folded conformation may foster tumor progression by acting at multiple levels. The present review focuses on such a cancer-promoting effect. The manuscript analyzes recent findings on the occurrence of PrPC in various cancers and discusses the multiple effects, which sustain cancer progression. Within this frame, the effects of PrPC on stemness and differentiation are discussed. A special emphasis is provided on the spreading of PrPC and the epigenetic effects, which are induced in neighboring cells to activate cancer-related genes. These detrimental effects are further discussed in relation to the aberrancy of its physiological and beneficial role on cell homeostasis. A specific paragraph is dedicated to the role of PrPC beyond its effects in the biology of cancer to represent a potential biomarker in the follow up of patients following surgical resection.

The Cellular Prion Protein: A Promising Therapeutic Target for Cancer

Studies on the cellular prion protein (PrP^C) have been actively conducted because misfolded PrP^C is known to cause transmissible spongiform encephalopathies or prion disease. PrP^C is a glycophosphatidylinositol-anchored cell surface glycoprotein that has been reported to affect several cellular functions such as stress protection, cellular differentiation, mitochondrial homeostasis, circadian rhythm, myelin homeostasis, and immune modulation. Recently, it has also been reported that PrP^C mediates tumor progression by enhancing the proliferation, metastasis, and drug resistance of cancer cells. In addition, PrP^C regulates cancer stem cell properties by interacting with cancer stem cell marker proteins. In this review, we summarize how PrP^C promotes tumor progression in terms of proliferation, metastasis, drug resistance, and cancer stem cell properties. In addition, we discuss strategies to treat tumors by modulating the function and expression of PrP^C via the regulation of HSPA1L/HIF-1α expression and using an anti-prion antibody.

Prion Protein at the Leading Edge: Its Role in Cell Motility

Cell motility is a central process involved in fundamental biological phenomena during embryonic development, wound healing, immune surveillance, and cancer spreading. Cell movement is complex and dynamic and requires the coordinated activity of cytoskeletal, membrane, adhesion and extracellular proteins. Cellular prion protein (PrPC) has been implicated in distinct aspects of cell motility, including axonal growth, transendothelial migration, epithelial-mesenchymal transition, formation of lamellipodia, and tumor migration and invasion. The preferential location of PrPC on cell membrane favors its function as a pivotal molecule in cell motile phenotype, being able to serve as a scaffold protein for extracellular matrix proteins, cell surface receptors, and cytoskeletal multiprotein complexes to modulate their activities in cellular movement. Evidence points to PrPC mediating interactions of multiple key elements of cell motility at the intra- and extracellular levels, such as integrins and matrix proteins, also regulating cell adhesion molecule stability and cell adhesion cytoskeleton dynamics. Understanding the molecular mechanisms that govern cell motility is critical for tissue homeostasis, since uncontrolled cell movement results in pathological conditions such as developmental diseases and tumor dissemination. In this review, we discuss the relevant contribution of PrPC in several aspects of cell motility, unveiling new insights into both PrPC function and mechanism in a multifaceted manner either in physiological or pathological contexts.

Prion Protein in Glioblastoma Multiforme

The cellular prion protein (PrPc) is an evolutionarily conserved cell surface protein encoded by the PRNP gene. PrPc is ubiquitously expressed within nearly all mammalian cells, though most abundantly within the CNS. Besides being implicated in the pathogenesis and transmission of prion diseases, recent studies have demonstrated that PrPc contributes to tumorigenesis by regulating tumor growth, differentiation, and resistance to conventional therapies. In particular, PrPc over-expression has been related to the acquisition of a malignant phenotype of cancer stem cells (CSCs) in a variety of solid tumors, encompassing pancreatic ductal adenocarcinoma (PDAC), osteosarcoma, breast cancer, gastric cancer, and primary brain tumors, mostly glioblastoma multiforme (GBM). Thus, PrPc is emerging as a key in maintaining glioblastoma cancer stem cells’ (GSCs) phenotype, thereby strongly affecting GBM infiltration and relapse. In fact, PrPc contributes to GSCs niche’s maintenance by modulating GSCs’ stem cell-like properties while restraining them from differentiation. This is the first review that discusses the role of PrPc in GBM. The manuscript focuses on how PrPc may act on GSCs to modify their expression and translational profile while making the micro-environment surrounding the GSCs niche more favorable to GBM growth and infiltration.

Cellular prion protein transcriptionally regulated by NFIL3 enhances lung cancer cell lamellipodium formation and migration through JNK signaling

Tumor invasion and metastasis are the major causes of treatment failure and mortality in lung cancer patients. In this study, we identified a group of genes with differential expression in in situ and invasive lung adenocarcinoma tissues by expression profiling; among these genes we further characterized the association of the upregulation of PRNP, the gene encoding cellular Prion protein (PrPc), with lung adenocarcinoma invasiveness. Immunohistochemistry on clinical specimens showed an association of PrPc expression with invasive but not in situ lung adenocarcinoma. Consistently, the expression of PrPc was higher in the highly invasive than in the lowly invasive lung adenocarcinoma cell lines. Knockdown of PrPc expression in cultured lung adenocarcinoma cells decreased their lamellipodium formation, in vitro migration and invasion, and in vivo experimental lung metastasis. Phosphorylation of JNKs was found to correlate with PrPc expression and the inhibition of JNKs suppressed the PrPc-induced up-regulation of lamellipodium formation, cell migration, and invasion. Moreover, we identified the nuclear factor, interleukin 3 regulated (NFIL3) protein as a transcriptional activator of the PRNP promoter. Accordingly, NFIL3 promoted lung cancer cell migration and invasion in a PrPc-dependent manner. High NFIL3 expression in clinical specimens of lung adenocarcinoma was also associated with tumor invasiveness. Overall, our observations suggest that the NFIL3/PrPc axis, through regulating lamellipodium formation and cell mobility via JNK signaling, plays a critical role in lung cancer invasiveness and metastasis.

The cellular prion protein controls the mesenchymal-like molecular subtype and predicts disease outcome in colorectal cancer

Background

Comprehensive transcriptomic analyses have shown that colorectal cancer (CRC) is heterogeneous and have led to the definition of molecular subtypes among which the stem-cell, mesenchymal-like group is associated with poor prognosis. The molecular pathways orchestrating the emergence of this subtype are incompletely understood. In line with the contribution of the cellular prion protein PrP^C to stemness, we hypothesize that deregulation of this protein could lead to a stem-cell, mesenchymal-like phenotype in CRC.

Methods

We assessed the distribution of the PrP^C-encoding PRNP mRNA in two large CRC cohorts according to molecular classification and its association with patient survival. We developed cell-based assays to explore the impact of gain and loss of PrP^C function on markers of the mesenchymal subtype and to delineate the signalling pathways recruited by PrP^C. We measured soluble PrP^C in the plasmas of 325 patients with metastatic CRC and probed associations with disease outcome.

Findings

We found that PRNP gene expression is enriched in tumours of the mesenchymal subtype and is associated with poor survival. Our in vitro analyses revealed that PrP^C controls the expression of genes that specify the mesenchymal subtype through the recruitment of the Hippo pathway effectors YAP and TAZ and the TGFß pathway. We showed that plasma levels of PrP^C are elevated in metastatic CRC and are associated with poor disease control.

Interpretation

Our findings define PrP^C as a candidate driver of the poor-prognosis mesenchymal subtype of CRC. They suggest that PrP^C may serve as a potential biomarker for patient stratification in CRC.

Funding

Grant support was provided by the following: Cancéropôle Ile de France (grant number 2016-1-EMERG-36-UP 5-1), Association pour la Recherche sur le Cancer (grant number PJA 20171206220), SATT Ile de France Innov (grant number 415) as well as INSERM.

Cellular prion protein and γ-synuclein overexpression in LS 174T colorectal cancer cell drives endothelial proliferation-to-differentiation switch

Background

Tumor-induced angiogenesis is an imperative event in pledging new vasculature for tumor metastasis. Since overexpression of neuronal proteins gamma-synuclein (γ-Syn) and cellular prion protein (PrP^C) is always detected in advanced stages of cancer diseases which involve metastasis, this study aimed to investigate whether γ-Syn or PrP^C overexpression in colorectal adenocarcinoma, LS 174T cells affects angiogenesis of endothelial cells, EA.hy 926 (EA).

Methods

EA cells were treated with conditioned media (CM) of LS 174T-γ-Syn or LS 174T-PrP, and their proliferation, invasion, migration, adhesion and ability to form angiogenic tubes were assessed using a range of biological assays. To investigate plausible background mechanisms in conferring the properties of EA cells above, nitrite oxide (NO) levels were measured and the expression of angiogenesis-related factors was assessed using a human angiogenesis antibody array.

Results

EA proliferation was significantly inhibited by LS 174T-PrP CM whereas its telomerase activity was reduced by CM of LS 174T-γ-Syn or LS 174T-PrP, as compared to EA incubated with LS 174T CM. Besides, LS 174T-γ-Syn CM or LS 174T-PrP CM inhibited EA invasion and migration in Boyden chamber assay. Furthermore, LS 174T-γ-Syn CM significantly inhibited EA migration in scratch wound assay. Gelatin zymography revealed reduced secretion of MMP-2 and MMP-9 by EA treated with LS 174T-γ-Syn CM or LS 174T-PrP CM. In addition, cell adhesion assay showed lesser LS 174T-γ-Syn or LS 174T-PrP cells adhered onto EA, as compared to LS 174T. In tube formation assay, LS 174T-γ-Syn CM or LS 174T-PrP CM induced EA tube formation. Increased NO secretion by EA treated with LS 174T-γ-Syn CM or LS 174T-PrP CM was also detected. Lastly, decreased expression of pro-angiogenic factors like CXCL16, IGFBP-2 and amphiregulin in LS 174T-γ-Syn CM or LS 174T-PrP CM was detected using the angiogenesis antibody array.

Discussion

These results suggest that overexpression of γ-Syn or PrP^C could possibly be involved in colorectal cancer-induced angiogenesis by inducing an endothelial proliferation-differentiation switch. NO could be the main factor in governing this switch, and modulation on the secretion patterns of angiogenesis-related proteins could be the strategy of colorectal cancer cells overexpressing γ-Syn or PrP^C in ensuring this transition.

Cytotoxic activities and effects of atractylodin and β-eudesmol on the cell cycle arrest and apoptosis on cholangiocarcinoma cell line

Cholangiocarcinoma (CCA) is the cancer of bile duct with high mortality rate particularly in Thailand. The clinical efficacy of the standard chemotherapeutics remains unsatisfactory, and therefore, discovery and development of the new alternative drugs with high efficacy and tolerability is needed. The aim of the study was to investigate cytotoxic activity as well as the underlying mechanisms through which atractylodin and β-eudesmol exert their activities on CCA cell growth inhibition, cell cycle arrest, and cell apoptosis. Effects of the compounds on cell cytotoxicity, cell cycle arrest, and cell apoptosis were analyzed using MTT assay, BD Cycletest™ Plus DNA kit, and FITC Annexin V Apoptosis Detection Kit I, respectively. The cytotoxic activities of both compounds were concentration- and time-dependent. The IC₅₀ [mean (SD)] of atractylodin and β-eudesmol were 41.66 (2.51) and 39.33 (1.15) μg/ml respectively. Both promoted cell cycle arrest at G1 phase, and induced cell apoptosis through activation of caspase-3/7. The highest activity was observed at 48 h of exposure. Results suggest that these mechanisms are at least in part, explain the cell cytotoxic and anti-CCA activity of atractylodin and β-eudesmol shown in vitro and in vivo models.

ATF4 regulated by MYC has an important function in anoikis resistance in human osteosarcoma cells

Anoikis resistance is a crucial step in the process of tumor metastasis. This step determines whether the tumor cells will survive when they become detached from the extracellular matrix. However, the specific mechanism of tumor cells to bypass anoikis and become resistant remains to be elucidated. The present study aimed to determine the internal mechanism of bypassing anoikis through comparison of human osteosarcoma cell lines with human normal cell lines. High activating transcription factor 4 (ATF4) and myelocytomatosis oncogene (MYC) expression levels were observed in MG-63 and U-2 OS human osteosarcoma cell lines. It is possible that ATF4 and MYC contribute to tumor progression. Subsequently, the expression levels of ATF4 and MYC in HUVEC and CHON-001 human normal cell lines were upregulated and their adhesion abilities were reduced; whereas their ability to bypass anoikis increased significantly. Simultaneously, after we Following a knock-down of ATF4 and MYC expression levels in MG-63 and U-2 OS human osteosarcoma cell lines, their adhesion ability increased and their ability to bypassing anoikis was significantly reduced. Upregulation of MYC resulted in an upregulation of ATF4, and chromatin immunoprecipitation and luciferase reporter gene technology demonstrated that MYC binds to the promoter of ATF4. These findings suggest that ATF4 regulated by MYC might contribute to resistance to anoikis in human osteosarcoma cells.

Role of HSPA1L as a cellular prion protein stabilizer in tumor progression via HIF-1α/GP78 axis

The cellular prion protein (PrP^C) is associated with metastasis, tumor progression and recurrence; however, the precise mechanisms underlying its action is not well understood. Our study found that PrP^C degradation decreased tumor progression in colorectal cancer (CRC). In a CRC cell line and human CRC tissue exposed to hypoxia, induced heat-shock 70-kDa protein-1-like (HSPA1L) expression stabilized hypoxia-inducible factor-1α (HIF-1α) protein and promoted PrP^C accumulation and tumorigenicity in vivo. PrP^C was degraded via the proteasome pathway mediated by the ubiquitin-protein E3 ligase glycoprotein 78 (GP78), which interacts directly with PrP^C. However, hypoxia-induced HSPA1L interacted with GP78 and inhibited its functions. HSPA1L knockdown facilitated the interaction of GP78 and PrP^C, thereby increasing PrP^C ubiquitination. Thus, GP78 was identified as the ubiquitinase for PrP^C, thereby revealing an essential mechanism that controls PrP^C levels in CRC. Our results suggest that the HSPA1L/HIF-1α/GP78 axis has a crucial role in PrP^C accumulation during tumor progression.

Physiological Functions of the Cellular Prion Protein

The prion protein, PrP^C, is a small, cell-surface glycoprotein notable primarily for its critical role in pathogenesis of the neurodegenerative disorders known as prion diseases. A hallmark of prion diseases is the conversion of PrP^C into an abnormally folded isoform, which provides a template for further pathogenic conversion of PrP^C, allowing disease to spread from cell to cell and, in some circumstances, to transfer to a new host. In addition to the putative neurotoxicity caused by the misfolded form(s), loss of normal PrP^C function could be an integral part of the neurodegenerative processes and, consequently, significant research efforts have been directed toward determining the physiological functions of PrP^C. In this review, we first summarise important aspects of the biochemistry of PrP^C before moving on to address the current understanding of the various proposed functions of the protein, including details of the underlying molecular mechanisms potentially involved in these functions. Over years of study, PrP^C has been associated with a wide array of different cellular processes and many interacting partners have been suggested. However, recent studies have cast doubt on the previously well-established links between PrP^C and processes such as stress-protection, copper homeostasis and neuronal excitability. Instead, the functions best-supported by the current literature include regulation of myelin maintenance and of processes linked to cellular differentiation, including proliferation, adhesion, and control of cell morphology. Intriguing connections have also been made between PrP^C and the modulation of circadian rhythm, glucose homeostasis, immune function and cellular iron uptake, all of which warrant further investigation.

Cellular Prion Protein PrPC and Ecto-5'-Nucleotidase Are Markers of the Cellular Stress Response to Aneuploidy

Aneuploidy is a hallmark of most human tumors, but the molecular physiology of aneuploid cells is not well characterized. In this study, we screened cell surface biomarkers of approximately 300 proteins by multiparameter flow cytometry using multiple aneuploid model systems such as cell lines, patient samples, and mouse models. Several new biomarkers were identified with altered expression in aneuploid cells, including overexpression of the cellular prion protein CD230/PrP^C and the immunosuppressive cell surface enzyme ecto-5'-nucleotidase CD73. Functional analyses associated these alterations with increased cellular stress. An increased number of CD73⁺ cells was observed in confluent cultures in aneuploid cells relative to their diploid counterparts. An elevated expression in CD230/PrP^C was observed in serum-deprived cells in association with increased generation of reactive oxygen species. Overall, our work identified biomarkers of aneuploid karyotypes, which suggest insights into the underlying molecular physiology of aneuploid cells. Cancer Res; 77(11); 2914-26. ©2017 AACR.

Integrated, High-Throughput, Multiomics Platform Enables Data-Driven Construction of Cellular Responses and Reveals Global Drug Mechanisms of Action

An understanding of how cells respond to perturbation is essential for biological applications; however, most approaches for profiling cellular response are limited in scope to pre-established targets. Global analysis of molecular mechanism will advance our understanding of the complex networks constituting cellular perturbation and lead to advancements in areas, such as infectious disease pathogenesis, developmental biology, pathophysiology, pharmacology, and toxicology. We have developed a high-throughput multiomics platform for comprehensive, de novo characterization of cellular mechanisms of action. Platform validation using cisplatin as a test compound demonstrates quantification of over 10 000 unique, significant molecular changes in less than 30 days. These data provide excellent coverage of known cisplatin-induced molecular changes and previously unrecognized insights into cisplatin resistance. This proof-of-principle study demonstrates the value of this platform as a resource to understand complex cellular responses in a high-throughput manner.

Cellular prion protein mediates early apoptotic proteome alternation and phospho-modification in human neuroblastoma cells

Anti-apoptotic properties of physiological and elevated levels of the cellular prion protein (PrP^c) under stress conditions are well documented. Yet, detrimental effects of elevated PrP^c levels under stress conditions, such as exposure to staurosporine (STS) have also been described. In the present study, we focused on discerning early apoptotic STS-induced proteome and phospho-proteome changes in SH-SY5Y human neuroblastoma cells stably transfected either with an empty or PRNP-containing vector, expressing physiological or supraphysiological levels of PrP^c, respectively. PrP^c-overexpression per se appears to stress the cells under STS-free conditions as indicated by diminished cell viability of PrP^c-overexpressing versus control cells. However, PrP^c-overexpression becomes advantageous following exposure to STS. Thus, only a short exposure (2 h) to 1 μM STS results in lower survival rates and significantly higher caspase-3 activity in control versus PrP^c-overexpressing cells. Hence, by exposing both experimental groups to the same apoptotic conditions we were able to induce apoptosis in control, but not in PrP^c-overexpressing cells (as assessed by caspase-3 activity), which allowed for filtering out proteins possibly contributing to protection against STS-induced apoptosis in PrP^c-overexpressing cells. Among other proteins regulated by different PrP^c levels following exposure to STS, those involved in maintenance of cytoskeleton integrity caught our attention. In particular, the finding that elevated PrP^c levels significantly reduce profilin-1 (PFN-1) expression. PFN-1 is known to facilitate STS-induced apoptosis. Silencing of PFN-1 expression by siRNA significantly increased viability of PrP^c-overexpressing versus control cells, under STS treatment. In addition, PrP^c-overexpressing cells depleted of PFN-1 exhibited increased viability versus PrP^c-overexpressing cells with preserved PFN-1 expression, both subjected to STS. Concomitant increase in caspase-3 activity was observed in control versus PrP^c-overexpressing cells after treatment with siRNA- PFN-1 and STS. We suggest that reduction of PFN-1 expression by elevated levels of PrP^c may contribute to protective effects PrP^c-overexpressing SH-SY5Y cells confer against STS-induced apoptosis.

Prion Protein Family Contributes to Tumorigenesis via Multiple Pathways

A wealth of evidence suggests that proteins from prion protein (PrP) family contribute to tumorigenesis in many types of cancers, including pancreatic ductal adenocarcinoma (PDAC), breast cancer, glioblastoma, colorectal cancer, gastric cancer, melanoma, etc. It is well documented that PrP is a biomarker for PDAC, breast cancer, and gastric cancer. However, the underlying mechanisms remain unclear. The major reasons for cancer cell-caused patient death are metastasis and multiple drug resistance, both of which connect to physiological functions of PrP expressing in cancer cells. PrP enhances tumorigenesis by multiple pathways. For example, PrP existed as pro-PrP in most of the PDAC cell lines, thus increasing cancer cell motility by binding to cytoskeletal protein filamin A (FLNa). Using PDAC cell lines BxPC-3 and AsPC-1 as model system, we identified that dysfunction of glycosylphosphatidylinositol (GPI) anchor synthesis machinery resulted in the biogenesis of pro-PrP. In addition, in cancer cells without FLNa expression, pro-PrP can modify cytoskeleton structure by affecting cofilin/F-actin axis, thus influencing cancer cell movement. Besides pro-PrP, we showed that GPI-anchored unglycosylated PrP can elevate cell mobility by interacting with VEGFR2, thus stimulating cell migration under serum-free condition. Besides affecting cancer cell motility, overexpressed PrP or doppel (Dpl) in cancer cells has been shown to increase cell proliferation, multiple drug resistance, and angiogenesis, thus, proteins from PrP gene family by affecting important processes via multiple pathways for cancer cell growth exacerbating tumorigenesis.

Prion protein binding to HOP modulates the migration and invasion of colorectal cancer cells

Colorectal cancer (CRC) is one of the most frequently diagnosed malignancies. The generation of conventional treatments has improved, but approximately 50 % of patients with CRC who undergo potentially curative surgery ultimately relapse and die, usually as a consequence of metastatic disease. Our previous findings showed that engagement of the cellular prion protein (PrP(C)) to its ligand HSP70/90 heat shock organizing protein (HOP) induces proliferation of glioblastomas. In addition, PrP(C) has been described as an important modulator of colorectal tumor growth. Here, we investigated the biological relevance of the PrP(C)-HOP interaction in CRC cells. We demonstrate that HOP induced the migration and invasion of CRC cell lines in a PrP(C)-dependent manner and that phosphorylation of the ERK1/2 pathway is a downstream mediator of these effects. Additionally, we show that a HOP peptide with the ability to bind PrP(C) and abolish the PrP(C)-HOP interaction inhibited the migration and invasion of CRC cells. Together, these data indicate that the disruption of the PrP(C)-HOP complex could be a potential therapeutic target for modulating the migratory and invasive cellular properties that lead to metastatic CRC.