Clinical Impact of PD-L1 Expression for Survival in Curatively Resected Colon Cancer.

BACKGROUND: Programmed death 1 (PD-1) and its ligand PD-L1 play a key dysfunction of T lymphocytes. The purpose of this study was to assess and compare the prognostic role of tumor- TILs and its relationship with PD-L1 expression in stage II and III colon cancer. METHODS: Immunohistochemisty was used to assess the densities of CD8+, CD4+, and FOXP3+ cells, and PD-L1 expression in intraepithelial tumor site from 58 stage II and III colon cancers. These were evaluated for association with histopathologic features and overall survival. RESULTS: PD-L1-positive tumors contained a higher number of CD8+ TILs with statistical significance (p = 0.001). CD4+ TILs showed positive correlation with PD-L1 expression (p = 0.034). There were no associations between PD-L1 expression and FOXP3+ TILs. Microsatellite instability (MSI)-high status (p = 0.001; Odd ration 18.0; 95% CI = 4.3-74.8) was the strongest prognostic factor along with mucinous/poor cell differentiation, CD8 and right tumor location was associated with PD-L1 expression (p = 0.024, 0.035 and 0.033, respectively). CONCLUSION: This study demonstrated that PD-L1 expression was associated with MSI-high, increased CD8+ TILs, mucinous and poor cell differentiation, and right-sided tumor location.

Clinicopathologic Analysis of Cathepsin B as a Prognostic Marker of Thyroid Cancer.

Thyroid cancer incidence has increased worldwide; however, investigations of thyroid cancer-related factors as potential prognosis markers remain insufficient. Secreted proteins from the cancer secretome are regulators of several molecular mechanisms and are, thereby, ideal candidates for potential markers. We aimed to identify a specific factor for thyroid cancer by analyzing the secretome from normal thyroid cells, papillary thyroid cancer (PTC) cells, and anaplastic thyroid cancer cells using mass spectrometry (MS). Cathepsin B (CTSB) showed highest expression in PTC cells compared to other cell lines, and CTSB levels in tumor samples were higher than that seen in normal tissue. Further, among thyroid cancer patients, increased CTSB expression was related to higher risk of lymph node metastasis (LNM) and advanced N stage. Overexpression of CTSB in thyroid cancer cell lines activated cell migration by increasing the expression of vimentin and Snail, while its siRNA-mediated silencing inhibited cell migration by decreasing vimentin and Snail expression. Mechanistically, CTSB-associated enhanced cell migration and upregulation of vimentin and Snail occurred via increased phosphorylation of p38. As our results suggest that elevated CTSB in thyroid cancer induces the expression of metastatic proteins and thereby leads to LNM, CTSB may be a good and clinically relevant prognostic marker.

Cold-inducible RNA-binding protein promotes epithelial-mesenchymal transition by activating ERK and p38 pathways.

Transforming growth factor-ß1 (TGF-ß1), a potent inducer of epithelial-to-mesenchymal transition (EMT), upregulates the cold-inducible RNA-binding protein (CIRP). The link between CIRP and EMT, however, remains unknown. To determine the role of CIRP in EMT, we performed CIRP knockdown and overexpression experiments in in vitro TGF-ß1-induced EMT models. We found that CIRP overexpression promoted the downregulation of epithelial markers and the upregulation of mesenchymal markers after TGF-ß1 treatment for EMT induction. It also promoted cell migration and invasion, key features of EMT. In contrast, CIRP knockdown inhibited the downregulation of epithelial markers and the upregulation of mesenchymal markers after TGF-ß1 treatment for EMT induction. In addition, it also inhibited cell migration and invasion. Furthermore, we demonstrated that the RNA-recognition motif in CIRP is essential for the role of CIRP in EMT. At the downstream level, CIRP knockdown downregulated Snail, key transcriptional regulator of EMT, while CIRP overexpression upregulated it. We found out that the link between CIRP and Snail is mediated by ERK and p38 pathways. EMT is a critical component of carcinoma metastasis and invasion. As demonstrated in this study, the biological role of CIRP in EMT may explain why CIRP overexpression has been associated with a bad prognosis in cancer patients.

Cytotoxic Compounds from Juglans sinensis Dode Display Anti-Proliferative Activity by Inducing Apoptosis in Human Cancer Cells.

Phytochemical investigation of the bark of Juglans sinensis Dode (Juglandaceae) led to the isolation of two active compounds, 8-hydroxy-2-methoxy-1,4-naphthoquinone (1) and 5-hydroxy-2-methoxy-1,4-naphthoquinone (2), together with 15 known compounds 3-17. All compounds were isolated from this plant for the first time. The structures of 1 and 2 were elucidated by spectroscopic data analysis, including 1D and 2D NMR experiments. Compounds 1-17 were tested for their cytotoxicity against the A549 human lung cancer cell line; compounds 1 and 2 exhibited significant cytotoxicity and additionally had potent cytotoxicity against six human cancer cell lines, MCF7 (breast cancer), SNU423 (liver cancer), SH-SY5Y (neuroblastoma), HeLa (cervical cancer), HCT116 (colorectal cancer), and A549 (lung cancer). In particular, breast, colon, and lung cancer cells were more sensitive to the treatment using compound 1. In addition, compounds 1 and 2 showed strong cytotoxic activity towards human breast cancer cells MCF7, HS578T, and T47D, but not towards MCF10A normal-like breast cells. They also inhibited the colony formation of MCF7, A549, and HCT116 cells in a dose-dependent manner. Flow cytometry analysis revealed that the percentage of apoptotic cells significantly increased in MCF7 cells upon the treatment with compounds 1 and 2. The mechanism of cell death caused by compounds 1 and 2 may be attributed to the upregulation of Bax and downregulation of Bcl2. These findings suggest that compounds 1 and 2 may be regarded as potential therapeutic agents against cancer.

Cold-inducible RNA-binding protein, CIRP, inhibits DNA damage-induced apoptosis by regulating p53.

CIRP has been implicated in apoptosis, yet its mechanism of action remains unknown. To determine the role of CIRP in DNA damage-induced apoptosis, we performed CIRP overexpression and knockdown experiments to investigate the effects of CIRP on key molecules in apoptosis pathway. Etoposide treatment was used to induce DNA damage-induced apoptosis. We found that CIRP knockdown increased p53 level, which in turn up-regulated pro-apoptotic genes and down-regulated anti-apoptotic genes. In contrast, CIRP overexpression decreased p53 level, which in turn down-regulated pro-apoptotic genes and up-regulated anti-apoptotic genes. The change in the expression levels of pro-apoptotic and anti-apoptotic genes shifts the balance between life and death of cells. CIRP expression is upregulated by chronic inflammation, and this phenomenon provides an interesting interventional opportunity in cancers arising from chronic inflammation. Chronic inflammation up-regulates CIRP, which in turn inhibit apoptosis. Therefore, inhibiting the function of up-regulated CIRP may have a therapeutic value in cancer.

YB-1 overexpression promotes a TGF-ß1-induced epithelial-mesenchymal transition via Akt activation.

The Y-box binding protein-1 (YB-1) is a transcription/translation regulatory protein, and the expression thereof is associated with cancer aggressiveness. In the present study, we explored the regulatory effects of YB-1 during the transforming growth factor-ß1 (TGF-ß1)-induced epithelial-to-mesenchymal transition (EMT) in lung adenocarcinoma cells. Downregulation of YB-1 increased E-cadherin promoter activity, and upregulation of YB-1 decreased promoter activity, suggesting that the YB-1 level may be correlated with the EMT. TGF-ß1 induced YB-1 expression, and TGF-ß1 translocated cytosolic YB-1 into the nucleus. YB-1 overexpression promoted TGF-ß1-induced downregulation of epithelial markers, upregulation of mesenchymal markers, and cell migration. Moreover, YB-1 overexpression enhanced the expression of E-cadherin transcriptional repressors via TGF-ß1-induced Akt activation. Our findings afford new insights into the role played by YB-1 in the TGF-ß1 signaling pathway.

Reversal of 2-Cys peroxiredoxin oligomerization by sulfiredoxin.

Hydrogen peroxide (H(2)O(2)) regulates the structure and function of 2-Cys peroxiredoxins (Prxs). Upon oxidation by excess H(2)O(2), Prxs become overoxidized to a sulfinic acid of its peroxidatic cysteine residue, resulting in a structural change from a small oligomer with peroxidase function to a large oligomer with chaperone function. Then, sulfiredoxin (Srx) reduces the overoxidized Prxs by an ATP-dependent mechanism. Although Srx is known to repair the overoxidized forms of Prx, the role of Srx in the reversal of Prx oligomerization remains to be elucidated. Here we investigated whether Srx1 directly facilitates the dissociation of yeast Prx1 (YPrx1) from a high-molecular-weight (HMW) complex to a low-molecular-weight (LMW) complex in vitro. Srx1 reactivates the YPrx1 peroxidase activity that is inactivated by H(2)O(2), whereas it decreases the chaperone activity enhanced by H(2)O(2). We show that Srx1 dissociates the H(2)O(2)-induced HMW YPrx1 complex, and that the Srx1 Cys84 residue is critical for its dissociation. In contrast to wild-type Srx1, an inactive Srx1 mutant (Srx1-C84S) did not induce the reactivation of inactivated YPrx1 or dissociation of the HMW YPrx1 complex. We revealed that Srx1 interacts directly with YPrx1 in yeast cells using bimolecular fluorescence complementation. Taken together, these findings suggest that Srx1 regulates YPrx1 function and structure in yeast cells through a direct interaction.

Targeted Protein Degradation: Principles and Applications of the Proteasome.

The proteasome is a multi-catalytic protease complex that is involved in protein quality control via three proteolytic activities (i.e., caspase-, trypsin-, and chymotrypsin-like activities). Most cellular proteins are selectively degraded by the proteasome via ubiquitination. Moreover, the ubiquitin-proteasome system is a critical process for maintaining protein homeostasis. Here, we briefly summarize the structure of the proteasome, its regulatory mechanisms, proteins that regulate proteasome activity, and alterations to proteasome activity found in diverse diseases, chemoresistant cells, and cancer stem cells. Finally, we describe potential therapeutic modalities that use the ubiquitin-proteasome system.

RNA-binding properties and RNA chaperone activity of human peroxiredoxin 1.

Human peroxiredoxin 1 (hPrx1), a member of the peroxiredoxin family, detoxifies peroxide substrates and has been implicated in numerous biological processes, including cell growth, proliferation, differentiation, apoptosis, and redox signaling. To date, Prx1 has not been implicated in RNA metabolism. Here, we investigated the ability of hPrx1 to bind RNA and act as an RNA chaperone. In vitro, hPrx1 bound to RNA and DNA, and unwound nucleic acid duplexes. hPrx1 also acted as a transcription anti-terminator in an assay using an Escherichia coli strain containing a stem-loop structure upstream of the chloramphenicol resistance gene. The overall cellular level of hPrx1 expression was not increased at low temperatures, but the nuclear level of hPrx1 was increased. In addition, hPrx1 overexpression enhanced the survival of cells exposed to cold stress, whereas hPrx1 knockdown significantly reduced cell survival under the same conditions. These findings suggest that hPrx1 may perform biological functions as a RNA-binding protein, which are distinctive from known functions of hPrx1 as a reactive oxygen species scavenger.

Human peroxiredoxin 1 modulates TGF-ß1-induced epithelial-mesenchymal transition through its peroxidase activity.

The epithelial-to-mesenchymal transition (EMT), which is induced by transforming growth factor-ß1 (TGF-ß1), is an important event that allows cancer cells to obtain invasive and metastatic characteristics. Although human peroxiredoxin 1 (hPrx1) has been implicated in tumor progression (e.g., invasion and metastasis), little is known about the role of hPrx1 in the EMT process during tumorigenesis. Here, we investigated the regulatory effect of hPrx1 during TGF-ß1-induced EMT in A549 lung adenocarcinoma cells. We observed that high hPrx1 levels downregulated E-cadherin expression, and low hPrx1 levels upregulated E-cadherin expression, suggesting that the hPrx1 level may be correlated with EMT. Knockdown of hPrx1 significantly inhibited TGF-ß1-induced EMT and cell migration, whereas hPrx1 overexpression enhanced TGF-ß1-induced EMT and cell migration. In contrast to wild-type hPrx1, a peroxidase-inactive hPrx1 mutant (hPrx1-C51S) resulted in markedly increased E-cadherin expression. Moreover, hPrx1 regulated the expression of two E-cadherin transcriptional repressors, Snail and Slug. These findings provide new insight into the role of hPrx1 in regulating TGF-ß1-induced EMT.

Large-scale production of soluble recombinant amyloid-ß peptide 1-42 using cold-inducible expression system.

Amyloid-ß peptide 1-42 (Aß(1-42)), the predominant form in senile plaques, plays important roles in the pathogenesis of Alzheimer's disease. Because Aß(1-42) has aggregation-prone nature, it has been difficult to produce in a soluble state in bacterial expression systems. In this study, we modified our expression system to increase the soluble fraction of Aß(1-42) in Escherichia coli (E. coli) cells. The expression level and solubility of recombinant Aß(1-42) induced at the low temperature (16°C) is highly increased compared to that induced at 37°C. To optimize expression temperature, the coding region of Aß(1-42) was constructed in a pCold vector, pCold-TF, which has a hexahistidine-tagged trigger factor (TF). Recombinant Aß(1-42) was expressed primarily as a soluble protein using pCold vector system and purified with a nickel-chelating resin. When the toxic effect of recombinant Aß(1-42) examined on human neuroblastoma SH-SY5Y cells, the purified Aß(1-42) induced cell toxicity on SH-SY5Y cells. In conclusion, the system developed in this study will provide a useful method for the production of aggregation prone-peptide such as Aß(1-42).

Heat-shock dependent oligomeric status alters the function of a plant-specific thioredoxin-like protein, AtTDX.

We found that Arabidopsis AtTDX, a heat-stable and plant-specific thioredoxin (Trx)-like protein, exhibits multiple functions, acting as a disulfide reductase, foldase chaperone, and holdase chaperone. The activity of AtTDX, which contains 3 tetratricopeptide repeat (TPR) domains and a Trx motif, depends on its oligomeric status. The disulfide reductase and foldase chaperone functions predominate when AtTDX occurs in the low molecular weight (LMW) form, whereas the holdase chaperone function predominates in the high molecular weight (HMW) complexes. Because deletion of the TPR domains results in a significant enhancement of AtTDX disulfide reductase activity and complete loss of the holdase chaperone function, our data suggest that the TPR domains of AtTDX block the active site of Trx and play a critical role in promoting the holdase chaperone function. The oligomerization status of AtTDX is reversibly regulated by heat shock, which causes a transition from LMW to HMW complexes with concomitant functional switching from a disulfide reductase and foldase chaperone to a holdase chaperone. Overexpression of AtTDX in Arabidopsis conferred enhanced heat shock resistance to plants, primarily via its holdase chaperone activity.

Prx1 Regulates Thapsigargin-Mediated UPR Activation and Apoptosis.

Endoplasmic reticulum (ER) stress activates the unfolded protein response (UPR) signaling via the accumulation of unfolded and misfolded proteins. ER stress leads to the production of reactive oxygen species (ROS), which are necessary to maintain redox homeostasis in the ER. Although peroxiredoxin 1 (Prx1) is an antioxidant enzyme that regulates intracellular ROS levels, the link between Prx1 and ER stress remains unclear. In this study, we investigated the role of Prx1 in X-box binding protein 1 (XBP-1) activation, the C/EBP homologous protein (CHOP) pathway, and apoptosis in response to ER stress. We observed that Prx1 overexpression inhibited the nuclear localization of XBP-1 and the expression of XBP-1 target genes and CHOP after thapsigargin (Tg) treatment to induce ER stress. In addition, Prx1 inhibited apoptosis and ROS production during ER stress. The ROS scavenger inhibited ER stress-induced apoptosis but did not affect XBP-1 activation and CHOP expression. Therefore, the biological role of Prx1 in ER stress may have important implications for ER stress-related diseases.

Proteomic identification of an embryo-specific 1Cys-Prx promoter and analysis of its activity in transgenic rice.

Proteomic analysis of a rice callus led to the identification of 10 abscisic acid (ABA)-induced proteins as putative products of the embryo-specific promoter candidates. 5'-flanking sequence of 1 Cys-Prx, a highly-induced protein gene, was cloned and analyzed. The transcription initiation site of 1 Cys-Prx maps 96 nucleotides upstream of the translation initiation codon and a TATA-box and putative seed-specific cis-acting elements, RYE and ABRE, are located 26, 115 and 124 bp upstream of the transcription site, respectively. ß-glucuronidase (GUS) expression driven by the 1 Cys-Prx promoters was strong in the embryo and aleurone layer and the activity reached up to 24.9 ± 3.3 and 40.5 ± 2.1 pmol (4 MU/min/µg protein) in transgenic rice seeds and calluses, respectively. The activity of the 1 Cys-Prx promoters is much higher than that of the previously-identified embryo-specific promoters, and comparable to that of strong endosperm-specific promoters in rice. GUS expression driven by the 1 Cys-Prx promoters has been increased by ABA treatment and rapidly induced by wounding in callus and at the leaf of the transgenic plants, respectively. Furthermore, ectopic expression of the GUS construct in Arabidopsis suggested that the 1 Cys-Prx promoter also has strong activity in seeds of dicot plants.

SILAC-Based Quantitative Proteomic Analysis of Oxaliplatin-Resistant Pancreatic Cancer Cells.

Oxaliplatin is a commonly used chemotherapeutic drug for the treatment of pancreatic cancer. Understanding the cellular mechanisms of oxaliplatin resistance is important for developing new strategies to overcome drug resistance in pancreatic cancer. In this study, we performed a stable isotope labelling by amino acids in cell culture (SILAC)-based quantitative proteomics analysis of oxaliplatin-resistant and sensitive pancreatic cancer PANC-1 cells. We identified 107 proteins whose expression levels changed (thresholds of 2-fold changes and p-value ≤ 0.05) between oxaliplatin-resistant and sensitive cells, which were involved in multiple biological processes, including DNA repair, cell cycle process, and type I interferon signaling pathway. Notably, myristoylated alanine-rich C-kinase substrate (MARCKS) and Wntless homolog protein (WLS) were upregulated in oxaliplatin-resistant cells compared to sensitive cells, as confirmed by qRT-PCR and Western blot analysis. We further demonstrated the activation of AKT and ß-catenin signaling (downstream targets of MARCKS and WLS, respectively) in oxaliplatin-resistant PANC-1 cells. Additionally, we show that the siRNA-mediated suppression of both MARCKS and WLS enhanced oxaliplatin sensitivity in oxaliplatin-resistant PANC-1 cells. Taken together, our results provide insights into multiple mechanisms of oxaliplatin resistance in pancreatic cancer cells and reveal that MARCKS and WLS might be involved in the oxaliplatin resistance.

The Role of Peroxiredoxin Family in Cancer Signaling.

Peroxiredoxins (Prxs) are antioxidant enzymes that protect cells from oxidative stress by reducing intracellular accumulation of reactive oxygen species (ROS). In mammalian cells, the six Prx isoforms are ubiquitously expressed in diverse intracellular locations. They are involved in the regulation of various physiological processes including cell growth, differentiation, apoptosis, immune response and metabolism as well as intracellular ROS homeostasis. Although there are increasing evidences that Prxs are involved in carcinogenesis of many cancers, their role in cancer is controversial. The ROS levels in cancer cells are increased compared to normal cells, thus promoting cancer development. Nevertheless, for various cancer types, an overexpression of Prxs has been found to be associated with poor patient prognosis, and an increasing number of studies have reported that tumorigenesis is either facilitated or inhibited by regulation of cancer-associated signaling pathways. This review summarizes Prx isoforms and their basic functions, the relationship between the expression level and the physiological role of Prxs in cancer cells, and their roles in regulating cancer-associated signaling pathways.

Role of Cytosolic 2-Cys Prx1 and Prx2 in Redox Signaling.

Peroxiredoxins (Prxs), a family of peroxidases, are reactive oxygen species scavengers that hydrolyze H2O2 through catalytic cysteine. Mammalian Prxs comprise six isoforms (typical 2-Cys Prxs; Prx1-4, atypical 2-Cys Prx; Prx5, and 1-Cys Prx; Prx6) that are distributed over various cellular compartments as they are classified according to the position and number of conserved cysteine. 2-Cys Prx1 and Prx2 are abundant proteins that are ubiquitously expressed mainly in the cytosol, and over 90% of their amino acid sequences are homologous. Prx1 and Prx2 protect cells from ROS-mediated oxidative stress through the elimination of H2O2 and regulate cellular signaling through redox-dependent mechanism. In addition, Prx1 and Prx2 are able to bind to a diversity of interaction partners to regulate other various cellular processes in cancer (i.e., regulation of the protein redox status, cell growth, apoptosis, and tumorigenesis). Thus, Prx1 and Prx2 can be potential therapeutic targets and it is particularly important to control their level or activity. This review focuses on cytosolic 2-Cys Prx1 and Prx2 and their role in the regulation of redox signaling based on protein-protein interaction.

Data on the stability of Prx1-associated snRNAs and mRNAs.

This data set is related to the research article entitled "Peroxiredoxin 1 post-transcriptionally regulates snoRNA expression" (Kim et al., 2019). It demonstrates that peroxiredoxin 1 (Prx1) increases the stability of Prx1-associated small nuclear RNAs (snRNAs) and mRNAs. We overexpressed Prx1 in SNU484 and HeLa cells, which were then treated with Actinomycin D (ActD) to inhibit transcription. After that, we measured the levels of Prx1-associated snRNAs and mRNAs using qPCR analysis.

Proteomic Analysis of Primary Colon Cancer and Synchronous Solitary Liver Metastasis.

BACKGROUND/AIM: Colon cancer is prone to distant metastases to other sites and the risk of recurrence is relatively high. Therefore, the identification of liver metastasis-related factors is important for the diagnosis or treatment of colon cancer. The aim of this study was to identify the metastasis-related factors that are differentially expressed in synchronous solitary liver metastasis compared to primary colon cancer. MATERIALS AND METHODS: Tissues of primary colon cancer and associated with liver metastases of five patients were used for mass spectrometry. Identified proteins were validated by western blotting. The in silico analysis was performed using the STRING database and GeneMANIA. RESULTS: We identified 58 differentially expressed proteins (DEPs), including 51 under-expressed and 7 over-expressed proteins among a total of 164 identified proteins. Major hubs of protein-protein networks were ACTC1, PRDX6, TPI1, and ALDH1A1. DEPs were located in the extracellular region and cytoplasm and were involved in the regulation of enzymatic activity. The metabolic process was significantly enriched in biological processes and an involvement in the KEGG pathway. CONCLUSION: These DEPs can potentially be used as biomarkers for the diagnosis of liver metastasis and they may provide a new strategy for developing anti-metastatic liver drugs in colon cancer patients.

Prx2 links ROS homeostasis to stemness of cancer stem cells.

Cancer stem cells (CSC) with low levels of reactive oxygen species (ROS) are resistant to conventional chemotherapy or radiation therapy. Peroxiredoxin 2 (Prx2) is a redox regulatory protein that plays a key role in maintaining ROS homeostasis in the tumor microenvironment. However, despite the role of Prx2 in ROS-mediated signal transduction, the association of Prx2 with stemness via ROS in CSC has not been thoroughly investigated. In this study, we investigated the link between Prx2 and CSC stemness through regulation of ROS levels in hepatocellular carcinoma (HCC) cells. ROS induced CSC stemness reduction and downregulated stem cell markers in Huh7 and SK-HEP1 cells. Prx2 knockdown decreased CSC sphere formation and expression of stem cell makers with increasing intracellular ROS levels. This effect was reversed by the ROS scavengers NAC and GSH in Prx2 knockdown cells. Conversely, we found that Prx2 overexpression promotes CSC stemness and the peroxidase activity of Prx2 is essential for CSC stemness using peroxidase inactive mutant, Prx2C51/172S. More importantly, the hyperoxidation-resistant mutant (Prx2ΔYF), which has a constant ROS scavenging activity even at high concentrations of ROS, increased the CSC stemness and expression of stem cell markers more than Prx2WT under oxidative stress. Taken together, our findings demonstrate that Prx2 links ROS homeostasis to CSC stemness; Prx2 is a mediator between ROS homeostasis and CSC stemness.