Effect of cyclophilin A on gene expression in human pancreatic cancer cells

Cyclophilin A inhibits A549 cell oxidative stress and apoptosis by modulating the PI3K/Akt/mTOR signaling pathway

The excessive and inappropriate production of reactive oxygen species (ROS) can cause oxidative stress and is implicated in the pathogenesis of lung cancer. Cyclophilin A (CypA), a member of the immunophilin family, is secreted in response to ROS. To determine the role of CypA in oxidative stress injury, we investigated the role that CypA plays in human lung carcinoma (A549) cells. Here, we showed the protective effect of human recombinant CypA (hCypA) on hydrogen peroxide (H₂O₂)-induced oxidative damage in A549 cells, which play crucial roles in lung cancer. Our results demonstrated that hCypA substantially promoted cell viability, superoxide dismutase (SOD), glutathione (GSH), and GSH peroxidase (GSH-Px) activities, and attenuated ROS and malondialdehyde (MDA) production in H₂O₂-induced A549 cells. Compared with H₂O₂-induced A549 cells, Caspase-3 activity in hCypA-treated cells was significantly reduced. Using Western blotting, we showed that hCypA facilitated Bcl-2 expression and inhibited Bax, Caspase-3, Caspase-7, and PARP-1 expression. Furthermore, hCypA activates the PI3K/Akt/mTOR pathway in A549 cells in response to H₂O₂ stimulation. Additionally, peptidyl-prolyl isomerase activity was required for PI3K/Akt activation by CypA. The present study showed that CypA protected A549 cells from H₂O₂-induced oxidative injury and apoptosis by activating the PI3K/Akt/mTOR pathway. Thus, CypA might be a potential target for lung cancer therapy.

CypA: A Potential Target of Tumor Radiotherapy and/or Chemotherapy

Cyclophilin A (CypA) is a ubiquitous and highly conserved protein. CypA, the intracellular target protein for the immunosuppressant cyclosporine A (CsA), plays important cellular roles through peptidyl-prolyl cis-trans isomerase (PPIase). Increasing evidence shows that CypA is up-regulated in a variety of human cancers. In addition to being involved in the occurrence and development of multiple tumors, overexpression of CypA has also been shown to be strongly associated with malignant transformation. Surgery, chemotherapy and radiotherapy are the three main treatments for cancer. Chemotherapy and radiotherapy are often used as direct or adjuvant treatments for cancer. However, various side effects and resistance to both chemotherapy and radiotherapy bring great challenges to these two forms of treatment. According to recent reports, CypA can improve the chemosensitivity and/or radiosensitivity of cancers, possibly by affecting the expression of drug-resistant related proteins, cell cycle arrest and activation of the mitogen-activated protein kinase (MAPK) signaling pathways. In this review, we focus on the role of CypA in cancer, its impact on cancer chemotherapeutic and radiotherapy sensitivity, and the mechanism of action. It is suggested that CypA may be a novel potential therapeutic target for cancer chemotherapy and/or radiotherapy.

Development and validation of an immune-related prognostic signature in lung adenocarcinoma

BACKGROUND

Lung adenocarcinomas (LUAD) is the most common histological subtype of lung cancers. Tumor immune microenvironment (TIME) is involved in tumorigeneses, progressions, and metastases. This study is aimed to develop a robust immune-related signature of LUAD.

METHODS

A total of 1774 LUAD cases sourced from public databases were included in this study. Immune scores were calculated through ESTIMATE algorithm and weighted gene co-expression network analysis (WGCNA) was applied to identify immune-related genes. Stability selections and Lasso COX regressions were implemented to construct prognostic signatures. Validations and comparisons with other immune-related signatures were conducted in independent Gene Expression Omnibus (GEO) cohorts. Abundant infiltrated immune cells and pathway enrichment analyses were carried out, respectively, through ImmuCellAI and gene set enrichment analysis (GSEA).

RESULTS

In Cancer Genome Atlas (TCGA) LUAD cohorts, immune scores of higher levels were significantly associated with better prognoses (P < .05). Yellow (n = 270) and Blue (n = 764) colored genes were selected as immune-related genes, and after univariate Cox regression analysis (P < .005), a total of 133 genes were screened out for subsequent model constructions. A four-gene signature (ARNTL2, ECT2, PPIA, and TUBA4A) named IPSLUAD was developed through stability selection and Lasso COX regression. It was suggested by multivariate and subgroup analyses that IPSLUAD was an independent prognostic factor. It was suggested by Kaplan-Meier survival analysis that eight out of nine patients in high-risk groups had significantly worse prognoses in validation data sets (P < .05). IPSLUAD outperformed other signatures in two independent cohorts.

CONCLUSIONS

A robust immune-related prognostic signature with great performances in multiple LUAD cohorts was developed in this study.

Jack of many trades: Multifaceted role of neuropilins in pancreatic cancer

Neuropilins (NRPs) have been described as receptors for class 3 semaphorins and coreceptors for a plethora of ligands, such as members of the vascular endothelial growth factor (VEGF) family of angiogenic cytokines and transforming growth factor (TGF). Initial studies using genetic models have indicated that neuropilin-1 (NRP-1) is essential for axonal guidance during neuronal and cardiovascular development, regulated via semaphorins and VEGF, respectively, whereas the other homolog of neuropilin, NRP-2, has been shown to play a more specific role in neuronal patterning and lymphangiogenesis. Pancreatic ductal adenocarcinoma (PDAC) remains a significant cause of cancer mortality with the lowest five-year survival rate compared to other types of cancer. Recent findings have indicated that NRPs are abundantly expressed in pancreatic cancer cell lines and pancreatic tumor tissues, where they mediate several essential cancer-initiating and cancer-promoting functional responses through their unique ability to bind multiple ligands. Specifically, NRPs have been implicated in numerous biological processes such as cancer cell proliferation, survival, invasion, and tumor growth. More recently, several other protumorigenic roles mediated by NRPs have emerged, advocating NRPs as ideal therapeutic targets against PDAC.

Downregulation of Peptidylprolyl isomerase A promotes cell death and enhances doxorubicin-induced apoptosis in hepatocellular carcinoma

Peptidylprolyl isomerase A (PPIA) is a peptidyl-prolyl cis-trans isomerase that is known to play a critical role in the development of many human cancers. However, the precise biological function of PPIA in hepatocellular carcinoma (HCC) remains largely unclear. In this study, lentiviral overexpression vectors and small interfering RNA knockdown methods were employed to investigate the biological effects of PPIA in HCC. PPIA levels in HCC tissues and peritumoral tissues were detected by real-time Polymerase Chain Reaction (RT-PCR), Western blotting, and immunohistochemistry. Our results indicate that PPIA levels were significantly higher in the HCC tissues compared to the matched peritumoral tissues. Moreover, PPIA expression was significantly associated with tumor size in these tissues. Interestingly, serum PPIA (sPPIA) levels were significantly higher in healthy controls compared to the HCC patients. Knockdown or overexpression of PPIA was shown to downregulate and upregulate cell growth, respectively. Moreover, PPIA siRNA knockdown appears to promote doxorubicin-induced apoptosis in HCC cells, altering the expression of downstream apoptotic factors. In summary, our results indicate that PPIA may play a pivotal role in HCC by regulating cell growth and could serve as a novel marker and therapeutic molecular target for HCC patients.

Cyclophilin A Enhances Cell Proliferation and Xenografted Tumor Growth of Early Gastric Cancer

BACKGROUND

Recently Cyclophilin A (CypA) was identified as a candidate target protein in gastric carcinoma. However, the role of CypA in gastric cancer (GC) has not been investigated extensively so far.

AIM

The purpose of this study was to determine the expression pattern of CypA in human GC, and to explore the effects of suppressed CypA expression on cell proliferation and xenografted tumor growth of gastric cancer.

METHODS

In the present study, we detected the expression pattern of CypA in human GC by immunohistochemistry analysis. Further, the RNAi method was used to silence CypA, and colony formation assay, growth curves, cell cycle and mouse xenograft were analysed.

RESULTS

An elevated expression of CypA in GC tissues compared with normal gastric mucosa was observed, especially in TNM stage-I and intestinal type of tumor. CypA was overexpressed in most GC cell lines and endogenous expression of CypA correlated with cell growth phenotypes. Transient suppression of CypA reduced the proliferation of BGC-823 and SGC-7901 GC cell lines. Exogenous CypA promoted the proliferation of NCI-N87 GC cells in a concentration dependent manner. Further study revealed that stable CypA silencing inhibited the proliferation, prevented cell cycle and reduced autophagy of BGC-823 GC cells in vitro through suppressing the ERK1/2 signal pathway. Stable CypA silencing also inhibited the growth of xenografted tumor of BGC-823 GC cell in nude mice.

CONCLUSIONS

These results indicate a special function mode for CypA of playing more important roles in the early stage of gastric tumorigenesis and suggest CypA as a new molecular target of diagnosis and treatment for GC patients.

Computational perspective and evaluation of plausible catalytic mechanisms of peptidyl-prolyl cis-trans isomerases

BACKGROUND

Peptidyl prolyl cis-trans isomerization of the protein backbone is involved in the regulation of many biological processes. Cis-trans isomerization is notoriously slow and is catalyzed by a family of cis-trans peptidyl prolyl isomerases (PPIases) that have been implicated in many diseases. A general consensus on how these enzymes speed up prolyl isomerization has not been reached after decades of both experimental and computational studies.

SCOPE OF REVIEW

Computational studies carried out to understand the catalytic mechanism of the prototypical FK506 binding protein 12, Cyclophilin A and peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (Pin1) are reviewed. A summary and an evaluation of the implications of the proposed mechanisms from computational studies are presented.

MAJOR CONCLUSIONS

The analysis of computational studies and evaluation of the proposed mechanisms provide a general consensus and a better understanding of PPIase catalysis. The speedup of the rate of peptidyl-prolyl isomerization by PPIases can be best described by a catalytic mechanism in which the substrate in transition state configuration is stabilized. The enzymes preferentially bind the transition state configuration of the substrate relative to the cis conformation, which in most cases is bound better than the trans conformation of the substrate. Stabilization of the transition state configuration of the substrate leads to a lower free energy barrier and a faster rate of isomerization when compared to the uncatalyzed isomerization reaction.

GENERAL SIGNIFICANCE

Fully understanding the catalytic mechanism of PPIases has broad implications for drug design, elucidation of the molecular basis of many diseases, protein engineering, and enzyme catalysis in general. This article is part of a Special Issue entitled Proline-directed Foldases: Cell Signaling Catalysts and Drug Targets.

Cyclophilin A as a New Therapeutic Target for Hepatitis C Virus-induced Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) related to hepatitis B virus (HBV) and hepatitis C virus (HCV) infections is thought to account for more than 80% of primary liver cancers. Both HBV and HCV can establish chronic liver inflammatory infections, altering hepatocyte and liver physiology with potential liver disease progression and HCC development. Cyclophilin A (CypA) has been identified as an essential host factor for the HCV replication by physically interacting with the HCV non structural protein NS5A that in turn interacts with RNA-dependent RNA polymerase NS5B. CypA, a cytosolic binding protein of the immunosuppressive drug cyclosporine A, is overexpressed in many cancer types and often associated with malignant transformation. Therefore, CypA can be a good target for molecular cancer therapy. Because of antiviral activity, the CypA inhibitors have been tested for the treatment of chronic hepatitis C. Nonimmunosuppressive Cyp inhibitors such as NIM811, SCY-635, and Alisporivir have attracted more interests for appropriating CypA for antiviral chemotherapeutic target on HCV infection. This review describes CypA inhibitors as a potential HCC treatment tool that is contrived by their obstructing chronic HCV infection and summarizes roles of CypA in cancer development.

Proteomic analysis in clear cell renal cell carcinoma: identification of differentially expressed protein by 2-D DIGE

Renal cell carcinoma (RCC), the most common neoplasm affecting the adult kidney, is characterised by heterogeneity of histological subtypes, drug resistance, and absence of molecular markers. Two-dimensional difference gel electrophoresis (2-D DIGE) technology in combination with mass spectrometry (MS) was applied to detect differentially expressed proteins in 20 pairs of RCC tissues and matched adjacent normal kidney cortex (ANK), in order to search for RCC markers. After gel analysis by DeCyder 6.5 and EDA software, differentially expressed protein spots were excised from Deep Purple stained preparative 2DE gel. A total of 100 proteins were identified by MS out of 2500 spots, 23 and 77 of these were, respectively, over- and down-expressed in RCC. The Principal Component Analysis applied to gels and protein spots exactly separated the two sample classes in two groups: RCC and ANK. Moreover, some spots, including ANXA2, PPIA, FABP7 and LEG1, resulted highly differential. The DIGE data were also confirmed by immunoblotting analysis for these proteins. In conclusion, we suggest that applying 2-D DIGE to RCC may provide the basis for a better molecular characterization and for the discovery of candidate biomarkers.

An Overview of Cyclophilins in Human Cancers

Cyclophilins (Cyps) belong to a group of proteins that have peptidyl-prolyl cis–trans isomerase (PPIase) and molecular chaperone activities. Originally, Cyps were identified as the intracellular receptors for the immunosuppressive drug cyclosporin A. Cyps are found in all prokaryotes and eukaryotes, and have been structurally conserved throughout evolution, implying their importance in cellular function. There are seven major Cyp isoforms in humans. CypA is up-regulated in many human cancers, and there is a strong correlation between over-expression of the CYPA gene and malignant transformation in some cancers. Moreover, CypA is directly under the transcriptional control of two critical transcription factors for cancer development: p53 and hypoxia inducible factor-1α. This review discusses the general biological functions of Cyps under a variety of stress conditions, and the importance and diverse roles of over-expression of CYP genes in human cancers, with a particular emphasis on CYPA. These oncogenic properties suggest that CypA is a promising target for cancer therapy.

Tissue proteomics reveals differential and compartment-specific expression of the homologs transgelin and transgelin-2 in lung adenocarcinoma and its stroma

Discovery of tissue-specific biomarkers for human cancer is crucial for early diagnosis and molecular understanding of the disease. To overcome the limitations posed by the large dynamic concentration range and compositional complexity of tissue biomacromolecules, we applied heparin affinity fractionation for proteomic enrichment. Comparing the proteomes of five paired samples of normal lung and pulmonary adenocarcinoma tissue by 2-D difference gel electrophoresis, 14 spots were found to be differentially expressed. From these candidate spots, three proteins overexpressed in cancer were identified by mass spectrometry as transgelin (TAGLN, SM22-alpha, WS3-10), transgelin-2 (TAGLN2), and cyclophilin A (PPIA). Quantitative RT-PCR indicated that both TAGLN2 and PPIA were upregulated at the transcriptional level. Differential protein expression levels were validated by Western blot analysis using an independent set of 10 paired lung adenocarcinoma samples. Using immunohistochemistry on human tissue sections, we discovered that overexpression of TAGLN was strictly localized to the tumor-induced reactive myofibroblastic stromal tissue compartment, whereas overexpression of TAGLN2 was exclusively localized to the neoplastic glandular compartment. Thus, the highly homologous protein pair TAGLN and TAGLN2 displayed mutually exclusive, compartment-specific cell type expression regulation in tumor stroma vs neoplastic epithelial cells. Our data further suggest that TAGLN may be a marker of active stromal remodeling in the vicinity of invasive carcinomas. It may shed light on mechanisms of tumor-stroma interaction and could be useful for early diagnosis, treatment guidance, and treatment response monitoring.

Role of cyclophilin a during oncogenesis

Cyclophilins (Cyps) are ubiquitously expressed proteins that are evolutionarily conserved. CypA is the most abundant among the Cyps and is expressed in the cytosol. With its chaperone and PPIase activities, CypA contributes to the maintenance of correct conformation of nascent or denatured proteins and also provides protection against environmental insults. Also, its expression is induced in response to a wide variety of stressors including cancer. Upregulation of CypA in small cell lung cancer, pancreatic cancer, breast cancer, colorectal cancer, squamous cell carcinoma and melanoma has been reported. In some cancers a correlation between CypA overexpression and malignant transformation has been established. While molecular partners of CypA that promote cancer development are yet to be discovered, various mechanisms have been proposed to account for the cytoprotective functions of CypA during cancer development. CypA may promote the survival of cells under the stressful condition of cancer. CypA may well be essential for maintaining the conformation of oncogenic proteins, signalling proteins for cell proliferation, antiapoptotic components, transcription factors, or cell motility regulatory proteins. Antioxidant effects of CypA, which have been suggested by some researchers, may also become critical to reactive oxygen species (ROS) creating an oncogenetic environment. Developing new CypA inhibitors for therapeutics has been surmised from the cytoprotective functions of CypA and its overexpression in many cancer types. Therefore, CypA can be further investigated as a useful tool for early diagnosis, treatment and prevention of human cancers.

Proteome analysis of multidrug resistance of human oral squamous carcinoma cells using CD147 silencing

There is a correlation between the multidrug-resistance (MDR) of cancer cells and their enhanced invasive or metastatic potential. We studied the expression of CD147, a plasma membrane glycoprotein that plays a key role in tumor metastasis by stimulating the production of matrix metalloproteinases (MMPs), in sensitive human oral squamous KB and MDR derivative KB/V cells. Reverse transcription-PCR and flow cytometric analysis revealed that KB/V cells expressed CD147 at significantly higher levels than their parental KB cells. Using stable RNA interference, we succeeded in establishing a CD147 knock-down KB/V cell line (KB/VsiCD147). MTT colorimetric assay showed an increase in the chemosensitivity to vincristine (VCR), all transretinoic acid (ATRA), taxol, and 5-fluorouracil (5-Fu) of KB/VsiCD147 cells. Proteome analysis of KB, KB/V, and KB/VsiCD147 cell lines identified 21 differently expressed proteins. The enhanced expression of representative active proteins, GRP75 and CyPA, was confirmed by Western blotting and RT-PCR. In addition, pretreatment of KB/V cells with a CyPA-binding immunosuppressive drug, cyclosporine A (CsA), enhanced their chemosensitivity to VCR and 5-Fu. We document an abundance of molecules that interact with CD147 in the MDR of human oral squamous carcinoma cells. Additional studies are needed to investigate these novel target proteins of CD147.

Interleukin-8 increases vascular endothelial growth factor and neuropilin expression and stimulates ERK activation in human pancreatic cancer

Interleukin-8 (IL-8) is associated with tumorigenesis by promoting angiogenesis and metastasis. Although up-regulation of IL-8 is indicated in many cancers, its function in pancreatic cancer has not been well characterized. In this study we examined the expression of IL-8 on pancreatic cancer cells and clinical tissue specimens, and investigated the effect of exogenous IL-8 on gene expression, and signaling in human pancreatic cancer cells. We found that pancreatic cancer cells expressed higher amount of IL-8 mRNA than normal human pancreatic ductal epithelium cells. IL-8 mRNA was also substantially overexpressed in 11 of 14 (79%) clinical pancreatic-adenocarcinoma samples compared with that in their surrounding normal tissues. Exogenous IL-8 up-regulated the expression of vascular endothelial growth factor(165), and neuropilin (NRP)-2 in BxPC-3 cells, one of human pancreatic cancer cell lines. IL-8 expression was inducible by hypoxia mimicking reagent cobalt chloride. In addition, IL-8 activated extracellular signal-regulated kinase (ERK)1/2 signaling pathway in BxPC-3 cells. Our studies suggest that IL-8 might be a malignant factor in human pancreatic cancer by induction of vascular endothelial growth factor and NRP-2 expression and ERK activation. Targeting IL-8 along with other antiangiogenesis therapy could be an effective treatment for this malignancy.

Defining the regulated secreted proteome of rodent adipocytes upon the induction of insulin resistance

Insulin resistance defines the metabolic syndrome and precedes, as well is the hallmark of, type II diabetes. Adipocytes, besides being a major site for energy storage, are endocrine in nature and secrete a variety of proteins, adipocytokines (adipokines), that can modulate insulin sensitivity, inflammation, obesity, hypertension, food intake (anorexigenic and orexigenic), and general energy homeostasis. Recent data demonstrates that increased intracellular glycosylation of proteins via O-GlcNAc can induce insulin resistance and that a rodent model with genetically elevated O-GlcNAc levels in muscle and fat displays hyperleptinemia. The link between O-GlcNAc levels, insulin resistance, and adipocytokine secretion is further explored here. First, with the use of immortalized and primary rodent adipocytes, the secreted proteome of differentiated adipocytes is more fully elucidated by the identification of 97 and 203 secreted proteins, respectively. Mapping of more than 80 N-linked glycosylation sites on adipocytokines from the cell lines further defines this proteome. Importantly, adipocytokines that are modulated when cells are shifted from insulin responsive to insulin resistant conditions are determined. By the use of two protocols for inducing insulin resistance, classical hyperglycemia with chronic insulin exposure and pharmacological elevation of O-GlcNAc levels, several proteins are identified that are regulated in a similar fashion under both conditions including HCNP, Quiescin Q6, Angiotensin, lipoprotein lipase, matrix metalloproteinase 2, and slit homologue 3. Detection of these potential prognostic/diagnostic biomarkers for metabolic syndrome, type II diabetes, and the resulting complications of both diseases further establishes the central role of the O-GlcNAc modification of intracellular proteins in the pathophysiology of these conditions.

Overexpressed cyclophilin A in cancer cells renders resistance to hypoxia- and cisplatin-induced cell death

Cyclophilin A (CypA) has been reported to be overexpressed in cancer cells, especially in solid tumors. To determine the role of CypA in tumorigenesis, we investigated the induction of CypA as well as the role it plays in cancer cells. Here, we have shown that induction of CypA is associated with hypoxia in a variety of cells, including DU145 human prostate cancer cell line. Our analysis of the CypA promoter clearly showed that CypA up-regulation is mediated by hypoxia-inducible factor-1alpha transcription factor. Interestingly, overexpression of CypA prevented hypoxia- and cisplatin-induced apoptosis, and this was associated with the suppression of reactive oxygen species generation and depolarization of mitochondrial membrane potential, whereas small interfering RNA-based CypA knockdown aggravated these factors. These results suggest that CypA is important in tumorigenesis, especially in tumor apoptosis.

Mass spectrometric proteomics profiles ofin vivo tumor secretomes: Capillary ultrafiltration sampling of regressive tumor masses

Identification of in vivo secreted peptides/proteins (secretomes) in tumor masses has the potential to provide important biomarkers and therapeutic targets for cancer therapy. However, limitations of existing technologies have made obtaining these secretomes for analysis extremely difficult. Here we employed an in vivo sampling technique using capillary ultrafiltration (CUF) probes to collect secretomes directly from tumor masses. Mass spectrometric proteomics approaches were then used to identify the tumor secretomes. A UV-induced skin fibrosarcoma cell line (UV-2240) was subcutaneously injected into C3H/NeH mice, resulting in tumor masses that initially progressed, then regressed and eventually eradicated. We then implanted CUF probes into tumor masses at the progressive and regressive stage. Five secreted proteins (cyclophilin-A, S100A4, profilin-1, thymosin beta 4 and 10), previously associated with tumor progression, were identified from tumor masses at the progressive stage. Five secreted proteins including three protease inhibitors (fetuin-A, alpha-1 antitrypsin 1-6, and contrapsin) were identified from tumor masses at the regressive stage. The technique involving CUF probes linked to mass spectrometric proteomics reinforces systems biology studies of cell-cell interactions and is potentially applicable to the discovery of in vivo biomarkers in human disease.

Dealing with the family: CD147 interactions with cyclophilins

CD147 is a widely expressed plasma membrane protein that has been implicated in a variety of physiological and pathological activities. It is best known for its ability to function as extracellular matrix metalloproteinase inducer (hence the other name for this protein, EMMPRIN), but has also been shown to regulate lymphocyte responsiveness, monocarboxylate transporter expression and spermatogenesis. These functions reflect multiple interacting partners of CD147. Recently, interaction of CD147 with proteins of the cyclophilin family has been demonstrated and activity of CD147 as a signalling receptor to extracellular cyclophilins A and B has been shown. Given that extracellular cyclophilins are potent chemotactic agents for various immune cells, further studies of the role of cyclophilin-CD147 interaction in inflammation followed. They demonstrated that agents targeting CD147 or cyclophilin had a significant anti-inflammatory effect in animal models of acute or chronic lung diseases and rheumatoid arthritis. Here, we review the current knowledge about interactions between CD147 and cyclophilins.