Expression of peroxiredoxins I and IV in multiple myeloma: association with immunoglobulin accumulation

Regulatory role of PDK1 via integrated gene analysis of mitochondria-immune response in periodontitis

AIMS

To investigate the association between mitochondrial events and immune response in periodontitis and related regulatory genes.

MAIN METHODS

Gene expression profiles in gingival tissues were retrieved from the Gene Expression Omnibus. Mitochondria-immune response-related differentially expressed genes (MIR-DEGs) between the healthy and periodontitis samples were determined. WGCNA, GO, and KEGG were used to investigate the function and the enriched pathways of MIR-DEGs. The correlation between MIR-DEGs expression and clinical probing pocket depth was analyzed. The MIR-DEGs were further identified and verified in animal samples. A periodontitis model was established in C57BL/6 mice with silk ligation. Micro-computed tomography was used to assess alveolar bone loss. Western blot, quantitative real-time polymerase chain reaction, and immunohistochemical analyses further validated the differential expression of the MIR-DEGs.

KEY FINDINGS

A total of ten MIR-DEGs (CYP24A1, PRDX4, GLDC, PDK1, BCL2A1, CBR3, ARMCX3, BNIP3, IFI27, and UNG) were identified, the expression of which could effectively distinguish patients with periodontitis from the healthy controls. Enhanced immune response was detected in the periodontitis group with that in the healthy controls, especially in B cells. PDK1 was a critical MIR-DEG correlated with B cell immune response and clinical periodontal probing pocket depth. Both animal and clinical periodontal samples presented higher gene and protein expression of PDK1 than the control samples. Additionally, PDK1 colocalized with B cells in both animal and clinical periodontal tissues.

SIGNIFICANCE

Mitochondria participate in the regulation of the immune response in periodontitis. PDK1 may be the key mitochondria-related gene regulating B-cell immune response in periodontitis.

Tigecycline Opposes Bortezomib Effect on Myeloma Cells Decreasing Mitochondrial Reactive Oxygen Species Production

Multiple myeloma is an incurable plasma cell malignancy. Most patients end up relapsing and developing resistance to antineoplastic drugs, like bortezomib. Antibiotic tigecycline has activity against myeloma. This study analyzed tigecycline and bortezomib combination on cell lines and plasma cells from myeloma patients. Apoptosis, autophagic vesicles, mitochondrial mass, mitochondrial superoxide, cell cycle, and hydrogen peroxide were studied by flow cytometry. In addition, mitochondrial antioxidants and electron transport chain complexes were quantified by reverse transcription real-time PCR (RT-qPCR) or western blot. Cell metabolism and mitochondrial activity were characterized by Seahorse and RT-qPCR. We found that the addition of tigecycline to bortezomib reduces apoptosis in proportion to tigecycline concentration. Supporting this, the combination of both drugs counteracts bortezomib in vitro individual effects on the cell cycle, reduces autophagy and mitophagy markers, and reverts bortezomib-induced increase in mitochondrial superoxide. Changes in mitochondrial homeostasis and MYC upregulation may account for some of these findings. These data not only advise to avoid considering tigecycline and bortezomib combination for treating myeloma, but caution on the potential adverse impact of treating infections with this antibiotic in myeloma patients under bortezomib treatment.

The deubiquitinase OTUD1 regulates immunoglobulin production and proteasome inhibitor sensitivity in multiple myeloma

Serum monoclonal immunoglobulin (Ig) is the main diagnostic factor for patients with multiple myeloma (MM), however its prognostic potential remains unclear. On a large MM patient cohort (n = 4146), we observe no correlation between serum Ig levels and patient survival, while amount of intracellular Ig has a strong predictive effect. Focused CRISPR screen, transcriptional and proteomic analysis identify deubiquitinase OTUD1 as a critical mediator of Ig synthesis, proteasome inhibitor sensitivity and tumor burden in MM. Mechanistically, OTUD1 deubiquitinates peroxiredoxin 4 (PRDX4), protecting it from endoplasmic reticulum (ER)-associated degradation. In turn, PRDX4 facilitates Ig production which coincides with the accumulation of unfolded proteins and higher ER stress. The elevated load on proteasome ultimately potentiates myeloma response to proteasome inhibitors providing a window for a rational therapy. Collectively, our findings support the significance of the Ig production machinery as a biomarker and target in the combinatory treatment of MM patients.

Peroxiredoxin IV plays a critical role in cancer cell growth and radioresistance through the activation of the Akt/GSK3 signaling pathways

High levels of redox enzymes have been commonly observed in various types of human cancer, although whether and how the enzymes contribute to cancer malignancy and therapeutic resistance have yet to be understood. Peroxiredoxin IV (Prx4) is an antioxidant with bona fide peroxidase and molecular chaperone functions. Here, we report that Prx4 is highly expressed in prostate cancer patient specimens, as well as established prostate cancer cell lines, and that its levels can be further stimulated through the activation of androgen receptor signaling. We used lentivirus-mediated shRNA knockdown and CRISPR-Cas9 based KO techniques to establish Prx4-depleted prostate cancer cells, which showed delayed cell cycle progression, reduced rate of cell proliferation, migration, and invasion compared to control cells. In addition, we used proteome profiler phosphokinase arrays to identify signaling changes in Prx4-depleted cells; we found that loss of Prx4 results in insufficient phosphorylation of both Akt and its downstream kinase GSK3α/β. Moreover, we demonstrate that Prx4-depleted cells are more sensitive to ionizing radiation as they display compromised ability to scavenge reactive oxygen species and increased accumulation of DNA damage. In mouse xenograft models, we show depletion of Prx4 leads to significant suppression of tumor growth, and tumors formed by Prx4-depleted cells respond more effectively to radiation therapy. Our findings suggest that increased levels of Prx4 contribute to the malignancy and radioresistance of prostate cancer through the activation of Akt/GSK3 signaling pathways. Therefore, strategies targeting Prx4 may be utilized to potentially inhibit tumor growth and overcome radioresistance in prostate cancer.

Crosstalk between endoplasmic reticulum stress and oxidative stress: a dynamic duo in multiple myeloma

Under physiological and pathological conditions, cells activate the unfolded protein response (UPR) to deal with the accumulation of unfolded or misfolded proteins in the endoplasmic reticulum. Multiple myeloma (MM) is a hematological malignancy arising from immunoglobulin-secreting plasma cells. MM cells are subject to continual ER stress and highly dependent on the UPR signaling activation due to overproduction of paraproteins. Mounting evidence suggests the close linkage between ER stress and oxidative stress, demonstrated by overlapping signaling pathways and inter-organelle communication pivotal to cell fate decision. Imbalance of intracellular homeostasis can lead to deranged control of cellular functions and engage apoptosis due to mutual activation between ER stress and reactive oxygen species generation through a self-perpetuating cycle. Here, we present accumulating evidence showing the interactive roles of redox homeostasis and proteostasis in MM pathogenesis and drug resistance, which would be helpful in elucidating the still underdefined molecular pathways linking ER stress and oxidative stress in MM. Lastly, we highlight future research directions in the development of anti-myeloma therapy, focusing particularly on targeting redox signaling and ER stress responses.

Tumor Microenvironment Proteomics: Lessons From Multiple Myeloma

Although the "seed and soil" hypothesis was proposed by Stephen Paget at the end of the 19th century, where he postulated that tumor cells (seeds) need a propitious medium (soil) to be able to establish metastases, only recently the tumor microenvironment started to be more studied in the field of Oncology. Multiple myeloma (MM), a malignancy of plasma cells, can be considered one of the types of cancers where there is more evidence in the literature of the central role that the bone marrow (BM) microenvironment plays, contributing to proliferation, survival, migration, and drug resistance of tumor cells. Despite all advances in the therapeutic arsenal for MM treatment in the last years, the disease remains incurable. Thus, studies aiming a better understanding of the pathophysiology of the disease, as well as searching for new therapeutic targets are necessary and welcome. Therefore, the present study aimed to evaluate the protein expression profiling of mononuclear cells derived from BM of MM patients in comparison with these same cell types derived from healthy individuals, in order to fill this gap in MM treatment. Proteomic analysis was performed using the mass spectrometry technique and further analyses were done using bioinformatics tools, to identify dysregulated biological pathways and/or processes in the BM microenvironment of patients with MM as a result of the disease. Among the pathways identified in this study, we can highlight an upregulation of proteins related to protein biosynthesis, especially chaperone proteins, in patients with MM. Additionally, we also found an upregulation of several proteins involved in energy metabolism, which is one of the cancer hallmarks. Finally, with regard to the downregulated proteins, we can highlight mainly those involved in different pathways of the immune response, corroborating the data that has demonstrated that the immune system of MM is impaired and, therefore, the immunotherapies that have been studied recently for the treatment of the disease are extremely necessary in the search for a control and a cure for these patients who live with the disease.

Metabolic, Anti-apoptotic and Immune Evasion Strategies of Primary Human Myeloma Cells Indicate Adaptations to Hypoxia

Multiple Myeloma (MM) is an incurable plasma cell malignancy primarily localized within the bone marrow (BM). It develops from a premalignant stage, monoclonal gammopathy of undetermined significance (MGUS), often via an intermediate stage, smoldering MM (SMM). The mechanisms of MM progression have not yet been fully understood, all the more because patients with MGUS and SMM already carry similar initial mutations as found in MM cells. Over the last years, increased importance has been attributed to the tumor microenvironment and its role in the pathophysiology of the disease. Adaptations of MM cells to hypoxic conditions in the BM have been shown to contribute significantly to MM progression, independently from the genetic predispositions of the tumor cells. Searching for consequences of hypoxia-induced adaptations in primary human MM cells, CD138-positive plasma cells freshly isolated from BM of patients with different disease stages, comprising MGUS, SMM, and MM, were analyzed by proteome profiling, which resulted in the identification of 6218 proteins. Results have been made fully accessible via ProteomeXchange with identifier PXD010600. Data previously obtained from normal primary B cells were included for comparative purposes. A principle component analysis revealed three clusters, differentiating B cells as well as MM cells corresponding to less and more advanced disease stages. Comparing these three clusters pointed to the alteration of pathways indicating adaptations to hypoxic stress in MM cells on disease progression. Protein regulations indicating immune evasion strategies of MM cells were determined, supported by immunohistochemical staining, as well as transcription factors involved in MM development and progression. Protein regulatory networks related to metabolic adaptations of the cells became apparent. Results were strengthened by targeted analyses of a selected panel of metabolites in MM cells and MM-associated fibroblasts. Based on our data, new opportunities may arise for developing therapeutic strategies targeting myeloma disease progression.

PRDX4 and Its Roles in Various Cancers

Reactive oxygen species play a vital role in cell survival by regulating physiological metabolism and signal transduction of cells. The imbalance of oxidant and antioxidant states induces oxidative stress within a cell. Redox regulation and oxidative stress are closely related to survival and proliferation of stem cells, cancer cells, and cancer stem cells. Peroxiredoxin 4, a typical endoplasmic reticulum-resident 2-Cys antioxidant of peroxiredoxins, can fine-tune hydrogen peroxide catabolism which affects cell survival by affecting redox balance, oxidative protein folding, and regulation of hydrogen peroxide signaling. Recent studies revealed the overexpression of peroxiredoxin 4 in several kinds of cancers, such as breast cancer, prostate cancer, ovarian cancer, colorectal cancer, and lung cancer. And it has been demonstrated that peroxiredoxin 4 causally contributes to tumorigenesis, therapeutic resistance, metastasis, and recurrence of tumors. In this article, the characteristics of peroxiredoxin 4 in physiological functions and the cancer-related research progress of mammalian peroxiredoxin 4 is reviewed. We believe that peroxiredoxin 4 has the potential of serving as a novel target for multiple cancers.

The Role of Redox-Regulating Enzymes in Inoperable Breast Cancers Treated with Neoadjuvant Chemotherapy

Although validated predictive factors for breast cancer chemoresistance are scarce, there is emerging evidence that the induction of certain redox-regulating enzymes may contribute to a poor chemotherapy effect. We investigated the possible association between chemoresistance and cellular redox state regulation in patients undergoing neoadjuvant chemotherapy (NACT) for breast cancer. In total, 53 women with primarily inoperable or inflammatory breast cancer who were treated with NACT were included in the study. Pre-NACT core needle biopsies and postoperative tumor samples were immunohistochemically stained for nuclear factor erythroid 2-related factor 2 (Nrf2), Kelch-like ECH-associated protein 1 (Keap1), thioredoxin (Trx), and peroxiredoxin I (Prx I). The expression of all studied markers increased during NACT. Higher pre-NACT nuclear Prx I expression predicted smaller size of a resected tumor (p = 0.00052; r = −0.550), and higher pre-NACT cytoplasmic Prx I expression predicted a lower amount of evacuated nodal metastasis (p = 0.0024; r = −0.472). Pre-NACT nuclear Trx expression and pre-NACT nuclear Keap1 expression had only a minor prognostic significance as separate factors, but when they were combined, low expression for both antibodies before NACT predicted dismal disease-free survival (log-rank p = 0.0030). Our results suggest that redox-regulating enzymes may serve as potential prognostic factors in primarily inoperable breast cancer patients.

Dimeric peroxiredoxins are druggable targets in human Burkitt lymphoma

Burkitt lymphoma is a fast-growing tumor derived from germinal center B cells. It is mainly treated with aggressive chemotherapy, therefore novel therapeutic approaches are needed due to treatment toxicity and developing resistance. Disturbance of red-ox homeostasis has recently emerged as an efficient antitumor strategy. Peroxiredoxins (PRDXs) are thioredoxin-family antioxidant enzymes that scavenge cellular peroxides and contribute to red-ox homeostasis. PRDXs are robustly expressed in various malignancies and critically involved in cell proliferation, differentiation and apoptosis. To elucidate potential role of PRDXs in lymphoma, we studied their expression level in B cell-derived primary lymphoma cells as well as in cell lines. We found that PRDX1 and PRDX2 are upregulated in tumor B cells as compared with normal counterparts. Concomitant knockdown of PRDX1 and PRDX2 significantly attenuated the growth rate of lymphoma cells. Furthermore, in human Burkitt lymphoma cell lines, we isolated dimeric 2-cysteine peroxiredoxins as targets for SK053, a novel thiol-specific small-molecule peptidomimetic with antitumor activity. We observed that treatment of lymphoma cells with SK053 triggers formation of covalent PRDX dimers, accumulation of intracellular reactive oxygen species, phosphorylation of ERK1/2 and AKT and leads to cell cycle arrest and apoptosis. Based on site-directed mutagenesis and modeling studies, we propose a mechanism of SK053-mediated PRDX crosslinking, involving double thioalkylation of active site cysteine residues. Altogether, our results suggest that peroxiredoxins are novel therapeutic targets in Burkitt lymphoma and provide the basis for new approaches to the treatment of this disease.

Oleate protects beta-cells from the toxic effect of palmitate by activating pro-survival pathways of the ER stress response

Long-term exposure of beta cells to saturated fatty acids impairs insulin secretion and increases apoptosis. In contrast, unsaturated fatty acids protect beta-cells from the long-term negative effects of saturated fatty acids. We aimed to identify the mechanisms underlying this protective action of unsaturated fatty acids. To address the aim, insulin-secreting MIN6 cells were exposed to palmitate in the absence or presence of oleate and analyzed by using nano-LC MS/MS based proteomic approach. Important findings were validated by using alternative approaches. Proteomic analysis identified 34 proteins differentially expressed in the presence of palmitate compared to control samples. These proteins play a role in insulin processing, mitochondrial function, metabolism of biomolecules, calcium homeostasis, exocytosis, receptor signaling, ER protein folding, antioxidant activity and anti-apoptotic function. When oleate was also present during culture, expression of 15 proteins was different from the expression in the presence of palmitate alone. Most of the proteins affected by oleate are targets of the ER stress response and play a pro-survival role in beta cells such as protein folding and antioxidative defence. We conclude that restoration of pro-survival pathways of the ER stress response is a major mechanism underlying the protective effect of unsaturated fatty acids in beta-cells treated with saturated fatty acids.

Total peroxiredoxin expression is associated with survival in patients with follicular lymphoma

Redox state-regulating enzymes may have roles in chemoresistance and also in lymphomagenesis, but there have been only a limited number of studies on this topic in lymphomas. Our aim was to assess expression of the redox state-regulating enzymes peroxiredoxins (Prxs) I-VI and thioredoxin (Trx) and the oxidative stress marker nitrotyrosine in follicular lymphomas (FLs). We immunohistochemically assessed Prxs I-VI, Trx and nitrotyrosine in a cohort of 76 histologically confirmed, untreated FLs. We also studied the localisation of Prxs I, II, III, V and VI by means of immunoelectron microscopy (IEM). Immunohistochemistry results were correlated with disease-specific survival (DSS), progression-free survival (PFS), overall survival (OS) and clinical prognostic factors. When all Prx expression intensities were grouped as a single variable, we discovered that high total Prx intensity correlated with favourable DSS (p = 0.024) and OS (p = 0.035) but not with PFS. No deaths due to lymphoma were recorded amongst patients with high total Prx expression during the median follow-up period of 7.6 years. IEM results were in line with earlier ones demonstrating wide subcellular localisation of Prx isoenzymes. In conclusion, our results demonstrate an association between high total Prx expression and prolonged survival and suggest that Prxs may have a protective role in FL that cannot be compensated by other antioxidant mechanisms.

Why high cholesterol levels help hematological malignancies: role of nuclear lipid microdomains

Background

Diet and obesity are recognized in the scientific literature as important risk factors for cancer development and progression. Hypercholesterolemia facilitates lymphoma lymphoblastic cell growth and in time turns in hypocholesterolemia that is a sign of tumour progression. The present study examined how and where the cholesterol acts in cancer cells when you reproduce in vitro an in vivo hypercholesterolemia condition.

Methods

We used non-Hodgkin’s T cell human lymphoblastic lymphoma (SUP-T1 cell line) and we studied cell morphology, aggressiveness, gene expression for antioxidant proteins, polynucleotide kinase/phosphatase and actin, cholesterol and sphingomyelin content and finally sphingomyelinase activity in whole cells, nuclei and nuclear lipid microdomains.

Results

We found that cholesterol changes cancer cell morphology with the appearance of protrusions together to the down expression of β-actin gene and reduction of β-actin protein. The lipid influences SUP-T1 cell aggressiveness since stimulates DNA and RNA synthesis for cell proliferation and increases raf1 and E-cadherin, molecules involved in invasion and migration of cancer cells. Cholesterol does not change GRX2 expression but it overexpresses SOD1, SOD2, CCS, PRDX1, GSR, GSS, CAT and PNKP. We suggest that cholesterol reaches the nucleus and increases the nuclear lipid microdomains known to act as platform for chromatin anchoring and gene expression.

Conclusion

The results imply that, in hypercholesterolemia conditions, cholesterol reaches the nuclear lipid microdomains where activates gene expression coding for antioxidant proteins. We propose the cholesterolemia as useful parameter to monitor in patients with cancer.

Proteomics Based Identification of Proteins with Deregulated Expression in B Cell Lymphomas

Follicular lymphoma and diffuse large B cell lymphomas comprise the main entities of adult B cell malignancies. Although multiple disease driving gene aberrations have been identified by gene expression and genomic studies, only a few studies focused at the protein level. We applied 2 dimensional gel electrophoresis to compare seven GC B cell non Hodgkin lymphoma (NHL) cell lines with a lymphoblastoid cell line (LCL). An average of 130 spots were at least two folds different in intensity between NHL cell lines and the LCL. We selected approximately 38 protein spots per NHL cell line and linked them to 145 unique spots based on the location in the gel. 34 spots that were found altered in at least three NHL cell lines when compared to LCL, were submitted for LC-MS/MS. This resulted in 28 unique proteins, a substantial proportion of these proteins were involved in cell motility and cell metabolism. Loss of expression of B2M, and gain of expression of PRDX1 and PPIA was confirmed in the cell lines and primary lymphoma tissue. Moreover, inhibition of PPIA with cyclosporine A blocked cell growth of the cell lines, the effect size was associated with the PPIA expression levels. In conclusion, we identified multiple differentially expressed proteins by 2-D proteomics, and showed that some of these proteins might play a role in the pathogenesis of NHL.

Physiological and pathological views of peroxiredoxin 4

Peroxiredoxins (PRDXs) form an enzyme family that exhibits peroxidase activity using electrons from thioredoxin and other donor molecules. As the signaling roles of hydrogen peroxide in response to extracellular stimuli have emerged, the involvement of PRDX in the hydrogen peroxide-mediated signaling has become evident. Among six PRDX members in mammalian cells, PRDX4 uniquely possesses a hydrophobic signal peptide at the amino terminus, and, hence, it undergoes either secretion or retention by the endoplasmic reticulum (ER) lumen. The role of PRDX4 as a sulfoxidase in ER is now attracting much attention regarding the oxidative protein folding of nascent proteins. Contrary to this role in the ER, the functional significance of PRDX4 in the extracellular milieu is virtually unknown despite its implications as a biomarker under pathological conditions in some diseases. Other than its systemically expressed form, a variant form of PRDX4 is transcribed from the upstream promoter/exon 1 of the systemic promoter/exon 1 and is uniquely expressed in sexually matured testes. Circumstantial evidence, together with deduced functions from the systemic form, suggests that there are potential roles for testicular PRDX4 in the reproductive processes such as the regulation of hormonal signals and the oxidative packaging of sperm chromatin. Elucidation of these PRDX4 functions under in vivo situations is expected to show the whole picture of how PRDX4 has evolved in multicellular organisms.

Identification of differentially expressed proteins from Leishmania amazonensis associated with the loss of virulence of the parasites

Background

The present study analyzed whether or not the in vitro cultivation for long periods of time of pre-isolated Leishmania amazonensis from lesions of chronically infected BALB/c mice was able to interfere in the parasites' infectivity using in vivo and in vitro experiments. In addition, the proteins that presented a significant decrease or increase in their protein expression content were identified applying a proteomic approach.

Methodology/Principal Findings

Parasites were cultured in vitro for 150 days. Aliquots were collected on the day 0 of culture (R0), as well as after ten (R10; 50 days of culture), twenty (R20; 100 days of culture), and thirty (R30; 150 days of culture) passages, and were used to analyze the parasites' in vitro and in vivo infectivity, as well as to perform the proteomic approach. Approximately 837, 967, 935, and 872 spots were found in 2-DE gels prepared from R0, R10, R20, and R30 samples, respectively. A total of 37 spots presented a significant decrease in their intensity of expression, whereas a significant increase in protein content during cultivation could be observed for 19 proteins (both cases >2.0 folds). Some of these identified proteins can be described, such as diagnosis and/or vaccine candidates, while others are involved in the infectivity of Leishmania. It is interesting to note that six proteins, considered hypothetical in Leishmania, showed a significant decrease in their expression and were also identified.

Conclusions/Significance

The present study contributes to the understanding that the cultivation of parasites over long periods of time may well be related to the possible loss of infectivity of L. amazonensis. The identified proteins that presented a significant decrease in their expression during cultivation, including the hypothetical, may also be related to this loss of parasites' infectivity, and applied in future studies, including vaccine candidates and/or immunotherapeutic targets against leishmaniasis.

Leishmania amazonensis can induce a diversity of clinical manifestations in mammal hosts, including tegumentary and visceral leishmaniasis. The present study evaluated the variation of infectivity of L. amazonensis, which was pre-isolated from lesions of chronically infected mice and in vitro cultured for 150 days, in turn connecting these results with the profile of parasite protein expression using a proteomic approach. Parasites were recovered after the first passage, as well as after 50, 100, and 150 days of axenic cultures, and were subsequently evaluated. A total of 37 proteins presented a significant decrease, whereas 19 proteins presented a significant increase in their protein expression content in the assays (both cases >2.0 fold). Some of the identified proteins have been reported in prior literature, including diagnosis and/or vaccine candidates for leishmaniasis, while others proved to be involved in the infectivity of Leishmania. It is interesting to note that proteins related to the parasites' metabolism were also the majority of the proteins identified in the old cultures of L. amazonensis, suggesting a possible relation between the metabolic state of parasites and their possible loss of infectivity. In conclusion, the proteins identified in this study represent a contribution to the discovery of new vaccine candidates and/or immunotherapeutic targets against leishmaniasis.