Assessing the contribution of the two protein disulfide isomerases PDIA1 and PDIA3 to cisplatin resistance. J Inorg Biochem. 2015;153:247-252. [PMID: 26364260 DOI: 10.1016/j.jinorgbio.2015.08.028]

Critical roles of protein disulfide isomerases in balancing proteostasis in the nervous system

Protein disulfide isomerases (PDIs) constitute a family of oxidoreductases promoting redox protein folding and quality control in the endoplasmic reticulum. PDIs catalyze disulfide bond formation, isomerization, and reduction, operating in concert with molecular chaperones to fold secretory cargoes in addition to directing misfolded proteins to be refolded or degraded. Importantly, PDIs are emerging as key components of the proteostasis network, integrating protein folding status with central surveillance mechanisms to balance proteome stability according to cellular needs. Recent advances in the field driven by the generation of new mouse models, human genetic studies, and omics methodologies, in addition to interventions using small molecules and gene therapy, have revealed the significance of PDIs to the physiology of the nervous system. PDIs are also implicated in diverse pathologies, ranging from neurodevelopmental conditions to neurodegenerative diseases and traumatic injuries. Here, we review the principles of redox protein folding in the ER with a focus on current evidence linking genetic mutations and biochemical alterations to PDIs in the etiology of neurological conditions.

Roles of the protein disulphide isomerases AccPDIA1 and AccPDIA3 in response to oxidant stress in Apis cerana cerana

Protein disulphide isomerase (PDI) plays an important role in a variety of physiological processes through its oxidoreductase activity and molecular chaperone activity. In this study, we cloned two PDI family members, AccPDIA1 and AccPDIA3, from Apis cerana cerana. AccPDIA1 and AccPDIA3 had typical sequence features of PDI family members and were constitutively expressed in A. cerana cerana. The expression levels of AccPDIA1 and AccPDIA3 were generally upregulated after treatment with a variety of environmental stress factors. Inhibition assays showed that E. coli expressing recombinant AccPDIA1 and AccPDIA3 proteins was more resistant to oxidative stress than control E. coli. In addition, silencing AccPDIA1 or AccPDIA3 in A. cerana cerana resulted in significant changes in the expression levels of several antioxidant-related genes as well as the enzymatic activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) and reduced the survival rate of A. cerana cerana under oxidative stress caused by high temperature. In conclusion, our results suggest that AccPDIA1 and AccPDIA3 may play important roles in the antioxidant activities of A. cerana cerana.

Protein disulfide isomerase family 6 promotes the imatinib-resistance of renal cell carcinoma by regulation of Wnt3a-Frizzled1 axis

Imatinib is a nontoxic tyrosine kinase inhibitor, used in the treatment of advanced renal cell carcinoma. However, some patients with renal cell carcinoma develop resistance to imatinib. Protein disulfide isomerase family 6 (PDIA6) was involved in the chemo-resistance of lung adenocarcinoma. In this study, the effect of PDIA6 on imatinib-resistance of renal cell carcinoma was investigated. First, PDIA6 was found to be up-regulated in the imatinib-resistant renal cell carcinoma tissues and cells. Functional assays showed that knockdown of PDIA6 sensitized imatinib-resistant renal cell carcinoma cells to imatinib through decreasing the half-maximal inhibitory concentration (IC50) of imatinib-resistant renal cell carcinoma cells. Secondly, cell proliferation of imatinib-resistant renal cell carcinoma cells was suppressed by PDIA6 silencing, and the apoptosis was promoted with reduced Bcl-2, enhanced Bax and cleaved caspase-3. Moreover, the interference of PDIA6 increased phosphorylation of H2A histone family member X (γH2AX), while decreased Rad51 and phosphorylated DNA-dependent protein kinase (DNA-PK) (p-DNA-PK) in imatinib-resistant renal cell carcinoma cells. Lastly, protein expression levels of Wnt3a and Frizzled1 (FZD1) in imatinib-resistant renal cell carcinoma cells were down-regulated by silencing of PDIA6. Over-expression of FZD1 attenuated PDIA6 silencing-induced increase in cell apoptosis and decrease in cell proliferation in imatinib-resistant renal cell carcinoma cells. In conclusion, knockdown of PDIA6 sensitized imatinib-resistant renal cell carcinoma cells into imatinib through inactivation of Wnt3a-FZD1 axis.

Sequenced Combinations of Cisplatin and Selected Phytochemicals towards Overcoming Drug Resistance in Ovarian Tumour Models

In the present study, cisplatin, artemisinin, and oleanolic acid were evaluated alone, and in combination, on human ovarian A2780, A2780^ZD0473R, and A2780^cisR cancer cell lines, with the aim of overcoming cisplatin resistance and side effects. Cytotoxicity was assessed by MTT reduction assay. Combination index (CI) values were used as a measure of combined drug effect. MALDI TOF/TOF MS/MS and 2-DE gel electrophoresis were used to identify protein biomarkers in ovarian cancer and to evaluate combination effects. Synergism from combinations was dependent on concentration and sequence of administration. Generally, bolus was most synergistic. Moreover, 49 proteins differently expressed by 2 ≥ fold were: CYPA, EIF5A1, Op18, p18, LDHB, P4HB, HSP7C, GRP94, ERp57, mortalin, IMMT, CLIC1, NM23, PSA3,1433Z, and HSP90B were down-regulated, whereas hnRNPA1, hnRNPA2/B1, EF2, GOT1, EF1A1, VIME, BIP, ATP5H, APG2, VINC, KPYM, RAN, PSA7, TPI, PGK1, ACTG and VDAC1 were up-regulated, while TCPA, TCPH, TCPB, PRDX6, EF1G, ATPA, ENOA, PRDX1, MCM7, GBLP, PSAT, Hop, EFTU, PGAM1, SERA and CAH2 were not-expressed in A2780^cisR cells. The proteins were found to play critical roles in cell cycle regulation, metabolism, and biosynthetic processes and drug resistance and detoxification. Results indicate that appropriately sequenced combinations of cisplatin with artemisinin (ART) and oleanolic acid (OA) may provide a means to reduce side effects and circumvent platinum resistance.

Cisplatin Protein Binding Partners and Their Relevance for Platinum Drug Sensitivity

Cisplatin is a widely used drug in the treatment of various solid tumors, such as ovarian cancer. However, while the acquired resistance significantly limits the success of therapy, some tumors, such as colorectal cancer, are intrinsically insensitive to cisplatin. Only a small amount of intracellular platinum binds to the target-genomic DNA. The fate of the remaining drug is largely obscure. This work aimed to identify the cytosolic protein binding partners of cisplatin in ovarian and colorectal cancer cells and to evaluate their relevance for cell sensitivity to cisplatin and oxaliplatin. Using the fluorescent cisplatin analog BODIPY-cisplatin, two-dimensional gel electrophoresis, and mass spectrometry, we identified the protein binding partners in A2780 and cisplatin-resistant A2780cis ovarian carcinoma, as well as in HCT-8 and oxaliplatin-resistant HCT-8ox colorectal cell lines. Vimentin, only identified in ovarian cancer cells; growth factor receptor-bound protein 2, only identified in colorectal cancer cells; and glutathione-S-transferase π, identified in all four cell lines, were further investigated. The effect of pharmacological inhibition and siRNA-mediated knockdown on cytotoxicity was studied to assess the relevance of these binding partners. The silencing of glutathione-S-transferase π significantly sensitized intrinsically resistant HCT-8 and HCT-8ox cells to cisplatin, suggesting a possible involvement of the protein in the resistance of colorectal cancer cells to the drug. The inhibition of vimentin with FiVe1 resulted in a significant sensitization of A2780 and A2780cis cells to cisplatin, revealing new possibilities for improving the chemosensitivity of ovarian cancer cells.

P4HB, a Novel Hypoxia Target Gene Related to Gastric Cancer Invasion and Metastasis

Gastric cancer (GC) is a common tumor-associated lethal disease, and invasiveness and metastasis are primary challenges in its clinical treatment. Hypoxia microenvironment cannot be ignored in the process of metastasis. Hypoxia inducible factor-1α (HIF-1α) is the core component of the hypoxia signaling pathway. The aim of this study was to identify potential hub genes and signaling pathways associated with HIF-1α. We explored the invasiveness- and metastasis-associated phenotype of GC via bioinformatics analysis and molecular studies. Differentially expressed genes (DEGs) were identified in GC cells and HIF-1α-knockdown GC cells. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed, and a protein-protein interaction (PPI) network was constructed. Hub genes were identified via centrality analysis and Molecular Complex Detection (MCODE) module analysis. The findings suggested that prolyl 4-hydroxylase beta polypeptide (P4HB) has strong associations with HIF-1α. Further, we observed that HIF-1α and P4HB were upregulated in SGC-7901 and BGC-823 cells. In addition, inhibition of HIF-1α expression reduced invasion and metastasis in GC cells; this effect was partially reversed by P4HB overexpression. Our results confirm that P4HB plays a significant role in the regulatory network of HIF-1α. Therefore, HIF-1α and P4HB may be considered potential biomarkers of GC.

PDIA6 modulates apoptosis and autophagy of non-small cell lung cancer cells via the MAP4K1/JNK signaling pathway

BACKGROUND

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer with a poor prognosis. We previously found that protein disulfide isomerase family 6 (PDIA6) is upregulated in lung squamous cell carcinoma (LSCC). This study aimed to elucidate the clinical relevance, biological functions, and molecular mechanisms of PDIA6 in NSCLC.

METHODS

The expression of PDIA6 in NSCLC was assessed using the TCGA database, western blotting, and immunohistochemistry. Correlations of PDIA6 expression with clinicopathological and survival features were evaluated. The functions of PDIA6 in regulating NSCLC cell growth, apoptosis, and autophagy were investigated using gain-and loss-of-function strategies in vitro or in vivo. The underlying molecular mechanisms of PDIA6 function were examined by human phospho-kinase array and co-immunoprecipitation.

FINDINGS

PDIA6 expression was upregulated in NSCLC compared with adjacent normal tissues, and the higher PDIA6 expression was correlated with poor prognosis. PDIA6 knockdown decreased NSCLC cell proliferation and increased cisplatin-induced intrinsic apoptosis, while PDIA6 overexpression had the opposite effects. In addition, PDIA6 regulated cisplatin-induced autophagy, and this contributed to PDIA6-mediated apoptosis in NSCLC cells. Mechanistically, PDIA6 reduced the phosphorylation levels of JNK and c-Jun. Moreover, PDIA6 interacted with MAP4K1 and inhibited its phosphorylation, ultimately inhibiting the JNK/c-Jun signaling pathway.

INTERPRETATION

PDIA6 is overexpressed in NSCLC and inhibits cisplatin-induced NSCLC cell apoptosis and autophagy via the MAP4K1/JNK/c-Jun signaling pathway, suggesting that PDIA6 may serve as a biomarker and therapeutic target for NSCLC patients. FUND: National Natural Science Foundation of China and Institutions of higher learning of innovation team from Liaoning province.

A Novel Three-Gene Model Predicts Prognosis and Therapeutic Sensitivity in Esophageal Squamous Cell Carcinoma

To precisely predict the clinical outcome and determine the optimal treatment options for patients with esophageal squamous cell carcinoma (ESCC) remains challenging. Prognostic models based on multiple molecular markers of tumors have been shown to have superiority over the use of single biomarkers. Our previous studies have identified the crucial role of ezrin in ESCC progression, which prompted us to hypothesize that ezrin-associated proteins contribute to the pathobiology of ESCC. Herein, we explored the clinical value of a molecular model constructed based on ezrin-associated proteins in ESCC patients. We revealed that the ezrin-associated proteins (MYC, PDIA3, and ITGA5B1) correlated with the overall survival (OS) and disease-free survival (DFS) of patients with ESCC. High expression of MYC was associated with advanced pTNM-stage (P=0.011), and PDIA3 and ITGA5B1 were correlated with both lymph node metastasis (PDIA3: P < 0.001; ITGA5B1: P=0.001) and pTNM-stage (PDIA3: P=0.001; ITGA5B1: P=0.009). Furthermore, we found that, compared with the current TNM staging system, the molecular model elicited from the expression of MYC, PDIA3, and ITGA5B1 shows higher accuracy in predicting OS (P < 0.001) or DFS (P < 0.001) in ESCC patients. Moreover, ROC and regression analysis demonstrated that this model was an independent predictor for OS and DFS, which could also help determine a subgroup of ESCC patients that may benefit from chemoradiotherapy. In conclusion, our study has identified a novel molecular prognosis model, which may serve as a complement for current clinical risk stratification approaches and provide potential therapeutic targets for ESCC treatment.

Prognostic value of hypoxia-inducible factor-1 alpha and prolyl 4-hydroxylase beta polypeptide overexpression in gastric cancer

AIM

To investigate the relationship between hypoxia-inducible factor-1α (HIF-1α), prolyl 4-hydroxylase beta (P4HB) expression, and clinicopathologic parameters, as well as the prognostic value of these genes for patients with gastric cancer (GC).

METHODS

Hypoxia is a critical factor that shapes the GC microenvironment. In previous reports, we have demonstrated that P4HB is a potential target of HIF-1α. In the present study, gene expression profiling interactive analysis (GEPIA) was used to analyze the relationship between P4HB and hypoxia-associated genes. To this end, 428 GC tissue samples were used to analyze the expression of HIF-1α and P4HB via immunohistochemical staining. Patient samples were classified as having weak-expression or over-expression both in terms of HIF-1α and P4HB. Correlations between biomarkers and clinicopathological factors were analyzed to predict survival.

RESULTS

P4HB demonstrated a positive correlation with hypoxia-associated genes (P < 0.05). HIF-1α and P4HB overexpression have a significant correlation with TNM staging (χ² = 23.32, P = 0.00; χ² = 65.64, P = 0.00) and peritoneum cavity metastasis (χ² = 12.67, P = 0.00; χ² = 39.29, P = 0.00). In univariate analysis, patients with a high HIF-1α expression trend had a shorter disease-free survival (DFS: 44.80 mo vs 22.06 mo) and overall survival (OS: 49.58 mo vs 39.92 mo). P4HB overexpression reflected similar results: patients with over-expression of P4HB had a shorter survival time than those with weak-expression (DFS: 48.03 mo vs 29.64 mo, OS: 52.48 mo vs 36.87 mo). Furthermore, HIF-1α is also a clinicopathological predictor of dismal prognosis according to multivariate analysis (DFS, 95%CI: 0.52-0.88, P < 0.00; OS, 95%CI: 0.50-0.85, P < 0.00). However, P4HB was meaningful in DFS (95%CI: 0.58-1.00, P < 0.05) but not in OS (95%CI: 0.72-1.23, P > 0.05).

CONCLUSION

Overexpression of HIF-1α and P4HB is associated with poor prognosis in patients with GC. Thus, these genes may be potential prognostic biomarker candidates in GC.

P4HB and PDIA3 are associated with tumor progression and therapeutic outcome of diffuse gliomas

Diffuse gliomas are the most common type of primary brain and central nervous system (CNS) tumors. Protein disulfide isomerases (PDIs) such as P4HB and PDIA3 act as molecular chaperones for reconstructing misfolded proteins, and are involved in endoplasmic reticulum stress and the unfolded protein response. The present study focused on the role of P4HB and PDIA3 in diffuse gliomas. Analysis of GEO and HPA data revealed that the expression levels of P4HB and PDIA3 were upregulated in glioma datasets. Their increased expression was then validated in 99 glioma specimens compared with 11 non-tumor tissues. High expression of P4HB and PDIA3 was significantly correlated with high Ki-67 and a high frequency of the TP53 mutation. Kaplan-Meier survival curve and Cox regression analyses showed that glioma patients with high P4HB and PDIA3 expression had a poor survival outcome, P4HB and PDIA3 could be independent prognostic biomarkers for diffuse gliomas. In vitro, knockdown of PDIA3 suppressed cell proliferation, induced cell apoptosis, and decreased the migration of glioma cells. Furthermore, downregulation of P4HB and PDIA3 may contribute to improve the survival of patients who receive chemotherapy and radiotherapy. The data suggest that high expression of P4HB and PDIA3 plays an important role in glioma progression, and could predict the survival outcome and therapeutic response of glioma patients. Therefore, protein disulfide isomerases may be explored as prognostic biomarkers and therapeutic targets for diffuse gliomas.

Platinum Binds Proteins in the Endoplasmic Reticulum of S. cerevisiae and Induces Endoplasmic Reticulum Stress

Pt(II)-based anticancer drugs are widely used in the treatment of a variety of cancers, but their clinical efficacy is hindered by undesirable side effects and resistance. While much research has focused on Pt(II) drug interactions with DNA, there is increasing interest in proteins as alternative targets and contributors to cytotoxic and resistance mechanisms. Here, we describe a chemical proteomic method for isolation and identification of cellular protein targets of platinum compounds using Pt(II) reagents that have been modified for participation in the 1,3 dipolar cycloaddition "click" reaction. Using this method to visualize and enrich for targets, we identified 152 proteins in Pt(II)-treated Saccharomyces cerevisiae. Of interest was the identification of multiple proteins involved in the endoplasmic reticulum (ER) stress response, which has been proposed to be an important cytoplasmic mediator of apoptosis in response to cisplatin treatment. Consistent with possible direct targeting of this pathway, the ER stress response was confirmed to be induced in Pt(II)-treated yeast along with in vitro Pt(II)-inhibition of one of the identified proteins, protein disulfide isomerase.

MiR-330-5p regulates tyrosinase and PDIA3 expression and suppresses cell proliferation and invasion in cutaneous malignant melanoma

BACKGROUND

Increasing evidence has suggested that miR-330-5p can function as a tumor suppressor in different types of cancers. However, the effects and underlying mechanisms of miR-330-5p in the development of cutaneous malignant melanoma (CMM) remain largely unknown. The aim of the present study was to investigate the role of miR-330-5p in CMM and to determine the molecular mechanisms underlying its action.

MATERIALS AND METHODS

The expression level of miR-330-5p was detected in 26 cases of primary CMM tissues and cell lines by real-time quantitative polymerase chain reaction. We also assessed whether overexpression of miR-330-5p influences in vitro cell proliferation, invasion, and migration. Western blotting analysis was used to detect the influence of miR-330-5p on the targets, and Pearson analysis was used to calculate the correlation between the expression of targets gene and miR-330-5p in CMM tissues.

RESULTS

Our study showed that miR-330-5p was downregulated in CMM tissues (P = 0.010) and cell lines (P < 0.05), and patients with high mitotic activity showed lower miR-330-5p expression levels (P = 0.002). Enforced expression of miR-330-5p inhibits malignant CMM cells proliferation and migration and led to downregulation of the TYR and PDIA3 protein. Moreover, the expression level of miR-330-5p in CMM tissues showed inverse relationship with the expression level of TYR and PDIA3 protein.

CONCLUSIONS

In conclusion, our findings suggested that miR-330-5p represents a potential tumor-suppressive miRNA and plays an important role in CMM progression by suppressing TYR and PDIA3 expression.