Ferredoxin reductase affects p53-dependent, 5-fluorouracil-induced apoptosis in colorectal cancer cells

Atractyloside mimics BORIS knockdown to induce DNA damage in colorectal cancer cells

The Brother of Regulator of Imprinted Sites (BORIS) is expressed abnormally in colorectal cancer and is predicted to be a potential diagnostic and prognostic target. However, little is known about BORIS-related signaling pathways and no bioactive drugs have been found to target BORIS. We screened the gene regulation panels of BORIS-silenced colorectal cancer cells by microarray assay and applied the regulated gene list in a connectivity map (CMap) database to screen for bioactive drugs which regulate gene panels similar to BORIS knockdown. Gene set enrichment analysis (GSEA) suggests a correlation between BORIS knockdown and apoptosis. Screening revealed atractyloside treatment as a drug similar to BORIS siRNA in regulating genes in colorectal cancer cells. Atractyloside treatment or BORIS knockdown induced the expression of XRCC4, which suggested DNA damage was induced by knockdown of the BORIS signaling pathway. H2A.X immunofluorescence stain indicated BORIS knockdown indeed created DNA damage. As atractyloside synergized with 5-Fluoruracil (5-FU) to suppress colorectal cancer cell proliferation, we concluded that the inhibition of BORIS downstream by atractyloside amplifies the effect of 5-FU by promoting DNA damage.

Molecular and cellular mechanisms of chemoresistance in pancreatic cancer

Pancreatic Ductal Adenocarcinoma (PDAC) is one of the most chemoresistant cancers, and current therapies targeting cancer-associated molecular pathways have not given satisfactory results, owing in part to rapid upregulation of alternative compensatory pathways. Most of the available treatments are palliative, focussing on improving the quality of life. At present, available options are surgery, embolization, radiation, chemotherapy, immunotherapy and use of other more targeted drugs. In this review, we describe the cellular and molecular effects of current chemotherapy drugs such as gemcitabine, FOLFIRINOX (5-fluorouracil [5-FU], oxaliplatin, irinotecan, and leucovorin) and ABRAXANE (nab-Paclitaxel), which have shown a survival benefit, although modest, for pancreatic cancer patients. Nevertheless, gemcitabine remains the standard first-line option for advanced-stage pancreatic cancer patients and, as resistance to the drug has attracted an increasing scientific interest, we deliberate on the main intracellular processes and proteins vital in acquired chemoresistance to gemcitabine. Lastly, our review examines various microenvironmental factors capable of instigating PDAC to develop resistance to chemotherapeutic drugs.

Improved potency of F10 relative to 5-fluorouracil in colorectal cancer cells with p53 mutations

Aim:

Resistance to fluoropyrimidine drugs (FPs) is a major cause of mortality in colorectal cancer (CRC). We assessed the potency advantage of the polymeric FP F10 relative to 5-fluorouracil (5FU) in four human CRC cell lines that differ only in TP53 mutational status to determine how p53 mutations affect drug response and whether F10 is likely to improve outcomes.

Methods:

HCT-116 human CRC cells (p53^+/+) and three isogenic variants (p53^−/−, R248W/+, R248W/−) were assessed for drug response. Resistance factors were derived from cell viability data and used to establish the relative potency advantage for F10. Rescue studies with exogenous uridine/thymidine determined if cytotoxicity resulted from DNA-directed processes.

Results:

Significant resistance to 5-FU resulted from p53-loss or from gain-of-function (GOF) mutation (R248W) and was greatest when GOF mutation was coupled with loss of wild-type p53. F10 is much more potent than 5-FU (137–314-fold depending on TP53 mutational status). F10 and 5-FU induce apoptosis by DNA- and RNA-directed mechanisms, respectively, and only F10 shows a modest enhancement in cytotoxicity upon co-treatment with leucovorin.

Conclusion:

TP53 mutational status affects inherent sensitivity to FPs, with p53 GOF mutations most deleterious. F10 is much more effective than 5-FU regardless of TP53 mutations and has potential to be effective to CRC that is resistant to 5-FU due, in part, to TP53 mutations.6,7

Emerging Roles of p53 Family Members in Glucose Metabolism

Glucose is the key source for most organisms to provide energy, as well as the key source for metabolites to generate building blocks in cells. The deregulation of glucose homeostasis occurs in various diseases, including the enhanced aerobic glycolysis that is observed in cancers, and insulin resistance in diabetes. Although p53 is thought to suppress tumorigenesis primarily by inducing cell cycle arrest, apoptosis, and senescence in response to stress, the non-canonical functions of p53 in cellular energy homeostasis and metabolism are also emerging as critical factors for tumor suppression. Increasing evidence suggests that p53 plays a significant role in regulating glucose homeostasis. Furthermore, the p53 family members p63 and p73, as well as gain-of-function p53 mutants, are also involved in glucose metabolism. Indeed, how this protein family regulates cellular energy levels is complicated and difficult to disentangle. This review discusses the roles of the p53 family in multiple metabolic processes, such as glycolysis, gluconeogenesis, aerobic respiration, and autophagy. We also discuss how the dysregulation of the p53 family in these processes leads to diseases such as cancer and diabetes. Elucidating the complexities of the p53 family members in glucose homeostasis will improve our understanding of these diseases.

Redox control in cancer development and progression

Cancer is the leading cause of death worldwide after cardiovascular diseases. This has been the case for the last few decades despite there being an increase in the number of cancer treatments. One reason for the apparent lack of drug effectiveness might be, at least in part, due to unspecificity for tumors; which often leads to substantial side effects. One way to improve the treatment of cancer is to increase the specificity of the treatment in accordance with the concept of individualized medicine. This will help to prevent further progression of an existing cancer or even to reduce the tumor burden. Alternatively it would be much more attractive and efficient to prevent the development of cancer in the first place. Therefore, it is important to understand the risk factors and the mechanisms of carcinogenesis in detail. One such risk factor, often associated with tumorigenesis and tumor progression, is an increased abundance of reactive oxygen species (ROS) arising from an imbalance of ROS-producing and -eliminating components. A surplus of ROS can induce oxidative damage of macromolecules including proteins, lipids and DNA. In contrast, ROS are essential for an adequate signal transduction and are known to regulate crucial cellular processes like cellular quiescence, differentiation and even apoptosis. Therefore, regulated ROS-formation at physiological levels can inhibit tumor formation and progression. With this review we provide an overview on the current knowledge of redox control in cancer development and progression.

The guardian of the genome p53 regulates exercise-induced mitochondrial plasticity beyond organelle biogenesis

The Guardian of the Genome p53 has been established as a potent tumour suppressor. However, culminating from seminal findings in rodents more than a decade ago, several studies have demonstrated that p53 is required to maintain basal mitochondrial function [ie, respiration and reactive oxygen species (ROS) homeostasis]. Specifically, via its role(s) as a tumour suppressor, p53 intimately surveys cellular DNA damage, in particular mitochondrial DNA (mtDNA), to ensure that the mitochondrial network is carefully monitored and cell viability is upheld, because aberrant mtDNA damage leads to apoptosis and widespread cellular perturbations. Indeed, data from rodents and humans have demonstrated that p53 forms an integral component of the exercise-induced signal transduction network regulating skeletal muscle mitochondrial remodelling. In response to exercise-induced disruptions to cellular homeostasis that have the potential to harm mtDNA (eg, contraction-stimulated ROS emissions), appropriate p53-regulated, mitochondrial turnover responses prevail to protect the genome and ultimately facilitate a shift from aerobic glycolysis to oxidative phosphorylation, adaptations critical for endurance-based exercise that are commensurate with p53's role as a tumour suppressor. Despite these observations, several discrepancies exist between rodent and human studies pinpointing p53 subcellular trafficking from nuclear-to-mitochondrial compartments following acute exercise. Such interspecies differences in p53 activity and the plausible p53-mediated adaptations to chronic exercise training will be discussed herein.

FDXR is a biomarker of radiation exposure in vivo

Previous investigations in gene expression changes in blood after radiation exposure have highlighted its potential to provide biomarkers of exposure. Here, FDXR transcriptional changes in blood were investigated in humans undergoing a range of external radiation exposure procedures covering several orders of magnitude (cardiac fluoroscopy, diagnostic computed tomography (CT)) and treatments (total body and local radiotherapy). Moreover, a method was developed to assess the dose to the blood using physical exposure parameters. FDXR expression was significantly up-regulated 24 hr after radiotherapy in most patients and continuously during the fractionated treatment. Significance was reached even after diagnostic CT 2 hours post-exposure. We further showed that no significant differences in expression were found between ex vivo and in vivo samples from the same patients. Moreover, potential confounding factors such as gender, infection status and anti-oxidants only affect moderately FDXR transcription. Finally, we provided a first in vivo dose-response showing dose-dependency even for very low doses or partial body exposure showing good correlation between physically and biologically assessed doses. In conclusion, we report the remarkable responsiveness of FDXR to ionising radiation at the transcriptional level which, when measured in the right time window, provides accurate in vivo dose estimates.

ROS Modulator Molecules with Therapeutic Potential in Cancers Treatments

Reactive Oxygen Species (ROS) are chemically reactive chemical species containing oxygen. The redox status of a cell is function of the relative concentrations of oxidized and reduced forms of proteins, enzymes, ROS, molecules containing thiol and other factors. In the organism, the redox balance is based on the generation and elimination of ROS produced by endogenous and exogenous sources. All living organisms must maintain their redox equilibrium to survive and proliferate. Enzymatic and molecular pathways control ROS levels tightly but differentially depending on the type of cell. This review is an overview of various molecules that modulate ROS production/detoxification and have a synergistic action with the chemotherapies to kill cancer cells while preserving normal cells to avoid anticancer drugs side effects, allowing a better therapeutic index of the anticancer treatments.

The Central Role of Amino Acids in Cancer Redox Homeostasis: Vulnerability Points of the Cancer Redox Code

A fine balance in reactive oxygen species (ROS) production and removal is of utmost importance for homeostasis of all cells and especially in highly proliferating cells that encounter increased ROS production due to enhanced metabolism. Consequently, increased production of these highly reactive molecules requires coupling with increased antioxidant defense production within cells. This coupling is observed in cancer cells that allocate significant energy reserves to maintain their intracellular redox balance. Glutathione (GSH), as a first line of defense, represents the most important, non-enzymatic antioxidant component together with the NADPH/NADP⁺ couple, which ensures the maintenance of the pool of reduced GSH. In this review, the central role of amino acids (AAs) in the maintenance of redox homeostasis in cancer, through GSH synthesis (cysteine, glutamate, and glycine), and nicotinamide adenine dinucleotide (phosphate) production (serine, and glutamine/glutamate) are illustrated. Special emphasis is placed on the importance of AA transporters known to be upregulated in cancers (such as system x_c-light chain and alanine-serine-cysteine transporter 2) in the maintenance of AA homeostasis, and thus indirectly, the redox homeostasis of cancer cells. The role of the ROS varies (often described as a "two-edged sword") during the processes of carcinogenesis, metastasis, and cancer treatment. Therefore, the context-dependent role of specific AAs in the initiation, progression, and dissemination of cancer, as well as in the redox-dependent sensitivity/resistance of the neoplastic cells to chemotherapy are highlighted.

5-fluorouracil combined with cisplatin and mitomycin C as an optimized regimen for hyperthermic intraperitoneal chemotherapy in gastric cancer

BACKGROUND AND OBJECTIVES

Optimized drug regimens for hyperthermic intraperitoneal chemotherapy (HIPEC) have not been standardized completely in patients with advanced gastric cancer (GC). We evaluated an optimized anti-tumor protocol comprising 5-fluorouracil (5-FU) combined with cisplatin (CDDP) and mitomycin C (MMC) in vitro for clinical use of HIPEC.

METHODS

The sensitivities of 5-FU, CDDP, or MMC, alone or in combination, using different drug concentrations, exposure times, and hyperthermic conditions (42°C) were determined in vitro by the CD-DST method using 3 different differentiated GC cell lines.

RESULTS

The tumor cell growth-inhibitory effect of 5-FU was concentration-dependent for all cell lines. In addition, 5-FU showed a hyperthermic sensitization effect at all drug concentrations for all cell lines. The appropriate concentration of each drug was 5-FU, 200 µg/mL; CDDP, 10 µg/mL; MMC, 2 µg/mL. Under hyperthermic conditions, most growth-inhibitory effects for each drug at 30 min was equivalent to 60 min of exposure; use of three drugs combined significantly inhibited growth compared with any of the drugs alone.

CONCLUSION

An appropriate in vitro intraperitoneal chemotherapy regimen for GC was combined use of 5-FU, CDDP, and MMC at 42°C for 30 min.

Evaluation of the cytotoxicity of the Bithionol-paclitaxel combination in a panel of human ovarian cancer cell lines

Previously, Bithionol (BT) was shown to enhance the chemosensitivity of ovarian cancer cell lines to cisplatin treatment. In the present study, we focused on the anti-tumor potential of the BT-paclitaxel combination when added to a panel of ovarian cancer cell lines. This in vitro study aimed to 1) determine the optimum schedule for combination of BT and paclitaxel and 2) assess the nature and mechanism(s) underlying BT-paclitaxel interactions. The cytotoxic effects of both drugs either alone or in combination were assessed by presto-blue cell viability assay using six human ovarian cancer cell lines. Inhibitory concentrations to achieve 50% cell death (IC₅₀) were determined for BT and paclitaxel in each cell line. Changes in levels of cleaved PARP, XIAP, bcl-2, bcl-xL, p21 and p27 were determined via immunoblot. Luminescent and colorimetric assays were used to determine caspases 3/7 and autotaxin (ATX) activity. Cellular reactive oxygen species (ROS) were measured by flow cytometry. Our results show that the efficacy of the BT-paclitaxel combination depends upon the concentrations and sequence of addition of paclitaxel and BT. Pretreatment with BT followed by paclitaxel resulted in antagonistic interactions whereas synergistic interactions were observed when both drugs were added simultaneously or when cells were pretreated with paclitaxel followed by BT. Synergistic interactions between BT and paclitaxel were attributed to increased ROS generation and enhanced apoptosis. Decreased expression of pro-survival factors (XIAP, bcl-2, bcl-xL) and increased expression of pro-apoptotic factors (caspases 3/7, PARP cleavage) was observed. Additionally, increased expression of key cell cycle regulators p21 and p27 was observed. These results show that BT and paclitaxel interacted synergistically at most drug ratios which, however, was highly dependent on the sequence of the addition of drugs. Our results suggest that BT-paclitaxel combination therapy may be effective in sensitizing ovarian cancer cells to paclitaxel treatment, thus mitigating some of the toxic effects associated with high doses of paclitaxel.

Analysis of molecular mechanisms of 5-fluorouracil-induced steatosis and inflammation in vitro and in mice

Chemotherapy-associated steatohepatitis is attracting increasing attention because it heralds an increased risk of morbidity and mortality in patients undergoing surgery because of liver metastases. The aim of this study was to develop in vitro and in vivo models to analyze the pathogenesis of 5-fluorouracil (5-FU)-induced steatohepatitis.

Therefore, primary human hepatocytes and HepG2 hepatoma cells were incubated with 5-FU at non-toxic concentrations up to 24 h. Furthermore, hepatic tissue of C57BL/6N mice was analyzed 24 h after application of a single 5-FU dose (200 mg/kg body weight). In vitro, incubation with 5-FU induced a significant increase of hepatocellular triglyceride levels. This was paralleled by an impairment of mitochondrial function and a dose- and time-dependently increased expression of fatty acid acyl-CoA oxidase 1 (ACOX1), which catalyzes the initial step for peroxisomal β-oxidation. The latter is known to generate reactive oxygen species, and consequently, expression of the antioxidant enzyme heme oxygenase 1 (HMOX1) was significantly upregulated in 5-FU-treated cells, indicative for oxidative stress. Furthermore, 5-FU significantly induced c-Jun N-terminal kinase (JNK) activation and the expression of pro-inflammatory genes IL-8 and ICAM-1. Also in vivo, 5-FU significantly induced hepatic ACOX1 and HMOX1 expression as well as JNK-activation, pro-inflammatory gene expression and immune cell infiltration. In summary, we identified molecular mechanisms by which 5-FU induces hepatocellular lipid accumulation and inflammation. Our newly developed models can be used to gain further insight into the pathogenesis of 5-FU-induced steatohepatitis and to develop therapeutic strategies to inhibit its development and progression.

Bystander signaling via oxidative metabolism

The radiation-induced bystander effect (RIBE) is the initiation of biological end points in cells (bystander cells) that are not directly traversed by an incident-radiation track, but are in close proximity to cells that are receiving the radiation. RIBE has been indicted of causing DNA damage via oxidative stress, besides causing direct damage, inducing tumorigenesis, producing micronuclei, and causing apoptosis. RIBE is regulated by signaling proteins that are either endogenous or secreted by cells as a means of communication between cells, and can activate intracellular or intercellular oxidative metabolism that can further trigger signaling pathways of inflammation. Bystander signals can pass through gap junctions in attached cell lines, while the suspended cell lines transmit these signals via hormones and soluble proteins. This review provides the background information on how reactive oxygen species (ROS) act as bystander signals. Although ROS have a very short half-life and have a nanometer-scale sphere of influence, the wide variety of ROS produced via various sources can exert a cumulative effect, not only in forming DNA adducts but also setting up signaling pathways of inflammation, apoptosis, cell-cycle arrest, aging, and even tumorigenesis. This review outlines the sources of the bystander effect linked to ROS in a cell, and provides methods of investigation for researchers who would like to pursue this field of science.

Ferredoxin reductase is critical for p53-dependent tumor suppression via iron regulatory protein 2

In this study, Chen and colleagues investigated the biological function of ferredoxin reductase (FDXR), a target of p53. They generated a Fdxr-deficient mouse model and found that the signal from FDXR to iron homeostasis and the p53 pathway was transduced by ferredoxin 2, a substrate of FDXR, and that p53 played a role in iron homeostasis and was required for FDXR-mediated iron metabolism, suggesting that the FDXR–p53 loop is critical for tumor suppression via iron homeostasis.

Ferredoxin reductase (FDXR), a target of p53, modulates p53-dependent apoptosis and is necessary for steroidogenesis and biogenesis of iron–sulfur clusters. To determine the biological function of FDXR, we generated a Fdxr-deficient mouse model and found that loss of Fdxr led to embryonic lethality potentially due to iron overload in developing embryos. Interestingly, mice heterozygous in Fdxr had a short life span and were prone to spontaneous tumors and liver abnormalities, including steatosis, hepatitis, and hepatocellular carcinoma. We also found that FDXR was necessary for mitochondrial iron homeostasis and proper expression of several master regulators of iron metabolism, including iron regulatory protein 2 (IRP2). Surprisingly, we found that p53 mRNA translation was suppressed by FDXR deficiency via IRP2. Moreover, we found that the signal from FDXR to iron homeostasis and the p53 pathway was transduced by ferredoxin 2, a substrate of FDXR. Finally, we found that p53 played a role in iron homeostasis and was required for FDXR-mediated iron metabolism. Together, we conclude that FDXR and p53 are mutually regulated and that the FDXR–p53 loop is critical for tumor suppression via iron homeostasis.

Feasibility and safety of hyperthermic intraperitoneal chemotherapy using 5-fluorouracil combined with cisplatin and mitomycin C in patients undergoing gastrectomy for advanced gastric cancer

BACKGROUND AND OBJECTIVES

We conducted a dose-finding study for 5-fluorouracil (5-FU) administered with cisplatin (CDDP) and mitomycin C (MMC) to find an improved regimen for hyperthermic intraperitoneal chemotherapy (HIPEC) for advanced gastric cancer (GC).

METHODS

The appropriate HIPEC regimen previously determined in vitro was 5-FU (200 µg/mL), MMC (2 µg/mL), and CDDP (10 µg/mL) at hyperthermic conditions (42°C) for 30 min. This was a clinical study to determine the recommended dose of 5-FU in combination with MMC and CDDP at 42°C for 30 min and to evaluate HIPEC safety in patients at high risk of developing peritoneal metastases following GC surgery.

RESULTS

Twelve patients were treated with surgery plus HIPEC using 5-FU at 0, 500, 750, and 1000 mg combined with MMC (10 mg) and CDDP (50 mg) in the perfusate (5 L). Dose-limiting toxicities did not develop until 1000 mg 5-FU was reached. Four patients experienced grade 1 or 2 adverse events. The recommended dose was 1000 mg 5-FU/5 L perfusate. Eight (66.7%) patients demonstrated no recurrence of peritoneal metastases; 5-year overall survival rate was 83.3%.

CONCLUSION

Gastrectomy and HIPEC with MMC, CDDP, and 5-FU is feasible, safe, and may protect against peritoneal metastasis following surgery for advanced GC.

The essential role of TAp73 in bortezomib-induced apoptosis in p53-deficient colorectal cancer cells

Mutations in the tumor suppressor p53 are among the most highly occurring events in colorectal cancer (CRC). Such mutations have been shown to influence the sensitivity of cancer cells to chemotherapeutic agents. However their impact on the efficacy of the proteasomal inhibitor bortezomib remains controversial. We thus re-evaluated the toxicity of bortezomib in the CRC cell lines HCT116 wt (wild-type) and its p53-/- clone. Transient resistance to bortezomib treatment was observed in p53-null cells that was later accompanied by an increase in levels and nuclear translocation of TAp73, an isoform of the p53-homologue p73, as well as induction of apoptosis. Knockdown of p73 in p53-/- cells using CRISPR/Cas9 significantly prolonged the duration of resistance. Moreover, similar results were observed in HT-29 cells carrying mutated p53, but not human fibroblasts with expression of functional p53. Thus, our results clearly demonstrated that TAp73 served as a substitute for p53 in bortezomib-induced apoptosis in p53-deficient or mutated cells, implicating that TAp73 could be a potential therapeutic target for treatment of CRCs, in particular those lacking functional p53.

Redox Imbalance in the Development of Colorectal Cancer

Redox imbalance is resulted from the destruction of balance between oxidants and antioxidants. The dominant oxidants are reactive oxygen species (ROS), which are involved in multiple cellular processes by physiologically transporting signal as a second messenger or pathologically oxidizing DNA, lipids, and proteins. Generally speaking, low concentration of ROS is indispensable for cell survival and proliferation. However, high concentration of ROS is cytotoxic. Additionally, ROS are now known to induce the oxidative modification of macromolecules especially proteins. The redox modification of proteins is involved in numerous biological processes related to diseases including CRC. Herein, we attempt to afford an overview that highlights the crosstalk between redox imbalance and CRC.

Knockdown of PRDX2 sensitizes colon cancer cells to 5-FU by suppressing the PI3K/AKT signaling pathway

Although, 5-Fluorouracil (5-FU) remains widely used in adjuvant therapy in patients with colon cancer, resistance to 5-FU-based chemotherapy is an important reason for treatment failure. Recent studies have reported that an enhanced reactive oxygen species (ROS) scavenging system shows drug resistance to 5-FU. Peroxiredoxin-2 (PRDX2), is an important member of the ROS scavenging system, and may be a potential target that promotes chemosensitivity to 5-FU in colon cancer. Here, we depleted PRDX2 by PRDX2-shRNA-LV transduction in two colon cancer cell lines and found that in vitro PRDX2 knockdown facilitates cell death, and apoptosis in 5-FU-treated colon cancer cells. In addition, we found that PRDX2 depletion in mice treated with 5-FU resulted in, inhibition of tumor growth, compared with mice treated with 5-FU alone. Our data also suggested that the PI3K/AKT signaling pathway links PRDX2 with 5-FU-induced apoptosis in colon cancer. Furthermore, when PRDX2 was overexpressed in colon cancer cells, we found increased p-AKT protein expression and reduced Bcl-2/Bax protein expression. PRDX2 and p-AKT protein expression were analyzed by immunohistochemistry technology in human colon carcinoma tissues. Pearson correlation coefficient is 0.873 and P<0.05. PRDX2 depletion led to reduced p-AKT expression and PI3K/AKT pathway inhibition promoted cell apoptosis in HT29 cell line. Taken together, our study suggests that decreasing the expression of PRDX2 could be a promising strategy for increasing the sensitivity of colon cancer cells to 5-FU.

Antitumor effects of oncolytic herpes simplex virus type 2 against colorectal cancer in vitro and in vivo

Background

The incidence of colorectal cancer (CRC) is on the rise. Furthermore, late-stage diagnoses and limited efficacious treatment options make CRC a complex clinical challenge. Therefore, a new therapeutic regimen with a completely novel therapeutic mechanism is necessary for CRC. In the present study, the therapeutic efficacy of oncolytic herpes simplex virus type 2 (oHSV2) in CRC was assessed in vitro and in vivo. oHSV2 is an oncolytic agent derived from herpes simplex virus type 2 that encodes granulocyte-macrophage colony-stimulating factor.

Materials and methods

We investigated the cytopathic effects of oHSV2 in CRC cell lines using the MTT assay. Then, cell cycle progression and apoptosis of oHSV2 were examined by flow cytometry. We generated a model of CRC with mouse CRC cell CT26 in BALB/c mice. The antitumor effects and adaptive immune response of oHSV2 were assessed in tumor-bearing mice. The therapeutic efficacy of oHSV2 was compared with the traditional chemotherapeutic agent, 5-fluorouracil.

Results

The in vitro data showed that oHSV2 infected the CRC cell lines successfully and that the tumor cells formed a significant number of syncytiae postinfection. The oHSV2 killed cancer cells independent of the cell cycle and mainly caused tumor cells necrosis. The in vivo results showed that oHSV2 significantly inhibited tumor growth and prolonged survival of tumor-bearing mice without weight loss. With virus replication, oHSV2 not only resulted in a reduction of myeloid-derived suppressor cells and regulatory T cells in the spleen, but also increased the number of mature dendritic cells in tumor-draining lymph nodes and the effective CD4⁺T and CD8⁺T-cells in the tumor microenvironment.

Conclusion

Our study provides the first evidence that oHSV2 induces cell death in CRC in vitro and in vivo. These findings indicate that oHSV2 is an effective therapeutic cancer candidate that causes an oncolytic effect and recruits adaptive immune responses for an enhanced therapeutic impact, thus providing a potential therapeutic tool for treatment of CRC.

Brother of Regulator of Imprinted Sites (BORIS) suppresses apoptosis in colorectal cancer

Identifying oncogenes that promote cancer cell proliferation or survival is critical for treatment of colorectal cancer. The Brother of Regulator of Imprinted Sites (BORIS) is frequently expressed in most types of cancer, but rarely in normal tissues. Aberrantly expressed BORIS relates to colorectal cancer, but its function in colorectal cancer cells remains unclear. In addition, previous studies indicated the significance of cytoplasm-localized BORIS in cancer cells. However, none of them investigated its function. Herein, we investigated the functions of BORIS in cancer cell proliferation and apoptosis and the role of cytoplasm-localized BORIS in colorectal cancer. BORIS expression correlated with colorectal cancer proliferation. BORIS overexpression promoted colorectal cancer cell growth, whereas BORIS knockdown suppressed cell proliferation. Sensitivity of colorectal cancer cells to 5-fluorouracil (5-FU) was inversely correlated with BORIS expression. These data suggest that BORIS functions as an oncogene in colorectal cancer. BORIS silencing induced reactive oxygen species (ROS) production and apoptosis, whereas BORIS supplementation inhibited apoptosis induced by BORIS short interfering RNA (siRNA), hydrogen peroxide (H₂O₂) or 5-FU. Introduction of BORIS-ZFdel showed that cytoplasmic localization of BORIS inhibited apoptosis but not ROS production. Our study highlights the anti-apoptotic function of BORIS in colorectal cancer.

Evaluation of the cytotoxicity of the Bithionol - cisplatin combination in a panel of human ovarian cancer cell lines

Background

Combination drug therapy appears a promising approach to overcome drug resistance and reduce drug-related toxicities in ovarian cancer treatments. In this in vitro study, we evaluated the antitumor efficacy of cisplatin in combination with Bithionol (BT) against a panel of ovarian cancer cell lines with special focus on cisplatin-sensitive and cisplatin-resistant cell lines. The primary objectives of this study are to determine the nature of the interactions between BT and cisplatin and to understand the mechanism(s) of action of BT-cisplatin combination.

Methods

The cytotoxic effects of drugs either alone or in combination were evaluated using presto-blue assay. Cellular reactive oxygen species were measured by flow cytometry. Immunoblot analysis was carried out to investigate changes in levels of cleaved PARP, XIAP, bcl-2, bcl-xL, p21 and p27. Luminescent and colorimetric assays were used to test caspases 3/7 and ATX activity.

Results

The efficacy of the BT-cisplatin combination depends upon the cell type and concentrations of cisplatin and BT. In cisplatin-sensitive cell lines, BT and cisplatin were mostly antagonistic except when used at low concentrations, where synergy was observed. In contrast, in cisplatin-resistant cells, BT-cisplatin combination treatment displayed synergistic effects at most of the drug ratios/concentrations. Our results further revealed that the synergistic interaction was linked to increased reactive oxygen species generation and apoptosis. Enhanced apoptosis was correlated with loss of pro-survival factors (XIAP, bcl-2, bcl-xL), expression of pro-apoptotic markers (caspases 3/7, PARP cleavage) and enhanced cell cycle regulators p21 and p27.

Conclusion

In cisplatin-resistant cell lines, BT potentiated cisplatin-induced cytotoxicity at most drug ratios via enhanced ROS generation and modulation of key regulators of apoptosis. Low doses of BT and cisplatin enhanced efficiency of cisplatin treatment in all the ovarian cancer cell lines tested. Our results suggest that novel combinations such as BT and cisplatin might be an attractive therapeutic approach to enhance ovarian cancer chemosensitivity. Combining low doses of cisplatin with subtherapeutic doses of BT can ultimately lead to the development of an innovative combination therapy to reduce/prevent the side effects normally occurring when high doses of cisplatin are administered.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-3034-2) contains supplementary material, which is available to authorized users.

microRNA-1827 represses MDM2 to positively regulate tumor suppressor p53 and suppress tumorigenesis

The tumor suppressor p53 plays a central role in tumor prevention. The E3 ubiquitin ligase MDM2 is the most critical negative regulator of p53, which binds to p53 and degrades p53 through ubiquitation. MDM2 itself is a transcriptional target of p53, and therefore, MDM2 forms a negative feedback loop with p53 to tightly regulate p53 levels and function. microRNAs (miRNAs) play a key role in regulation of gene expression. miRNA dysregulation plays an important role in tumorigenesis. In this study, we found that miRNA miR-1827 is a novel miRNA that targets MDM2 through binding to the 3′-UTR of MDM2 mRNA. miR-1827 negatively regulates MDM2, which in turn increases p53 protein levels to increase transcriptional activity of p53 and enhance p53-mediated stress responses, including apoptosis and senescence. Overexpression of miR-1827 suppresses the growth of xenograft colorectal tumors, whereas the miR-1827 inhibitor promotes tumor growth in mice in a largely p53-dependent manner. miR-1827 is frequently down-regulated in human colorectal cancer. Decreased miR-1827 expression is associated with high MDM2 expression and poor prognosis in colorectal cancer. In summary, our results reveal that miR-1827 is a novel miRNA that regulates p53 through targeting MDM2, and highlight an important role and the underlying mechanism of miR-1827 in tumor suppression.

Ionizing radiation biomarkers in epidemiological studies - An update

Recent epidemiology studies highlighted the detrimental health effects of exposure to low dose and low dose rate ionizing radiation (IR): nuclear industry workers studies have shown increased leukaemia and solid tumour risks following cumulative doses of <100mSv and dose rates of <10mGy per year; paediatric patients studies have reported increased leukaemia and brain tumours risks after doses of 30-60mGy from computed tomography scans. Questions arise, however, about the impact of even lower doses and dose rates where classical epidemiological studies have limited power but where subsets within the large cohorts are expected to have an increased risk. Further progress requires integration of biomarkers or bioassays of individual exposure, effects and susceptibility to IR. The European DoReMi (Low Dose Research towards Multidisciplinary Integration) consortium previously reviewed biomarkers for potential use in IR epidemiological studies. Given the increased mechanistic understanding of responses to low dose radiation the current review provides an update covering technical advances and recent studies. A key issue identified is deciding which biomarkers to progress. A roadmap is provided for biomarker development from discovery to implementation and used to summarise the current status of proposed biomarkers for epidemiological studies. Most potential biomarkers remain at the discovery stage and for some there is sufficient evidence that further development is not warranted. One biomarker identified in the final stages of development and as a priority for further research is radiation specific mRNA transcript profiles.

5-Fluorouracil inhibits cell migration by induction of Sestrin2 in colon cancer cells

5-Fluorouracil (5-FU) is a chemotherapeutic agent used in the treatment of colorectal cancer. In this study, we investigated whether 5-FU induces Sestrin2 (SESN2), an antioxidant enzyme, and the role of SESN2 in 5-FU action in colon cancer cells. We found that 5-FU upregulated SESN2 protein expression in both HCT116 and HT29 cells. It also increased transcripts of SESN1 and SESN2, but not of SESN3. Furthermore, we investigated whether production of reactive oxygen species (ROS) was involved in 5-FU-induced SESN2 expression. 5-FU did not increase ROS production nor affect Nrf2 phosphorylation and expression levels. Moreover, SESN2 upregulation by 5-FU was not prevented by pretreatment with antioxidants. Next, we investigated p53 levels after 5-FU treatment to elucidate the regulation of SESN2 by 5-FU. An increase in p53 levels was detected following 5-FU treatment; pifithrin-α, an inhibitor of p53 activation, reversed 5-FU-induced SESN2 expression. 5-FU prevented serum-induced in vitro cell migration, but knockdown of SESN2 or treatment with pifithrin-α reversed a 5-FU-mediated decrease in cell migration. Taken together, our results suggest that 5-FU increases SESN2 levels via a p53-dependent pathway, which contributes to inhibition of cancer cell migration in vitro.

Oxidative Stress and Fitness Changes in Cancer Patients after Exercise Training

INTRODUCTION

The purpose of this study was to determine the effect of an exercise intervention (EX) on muscular strength, cardiorespiratory fitness (CRF), and oxidative stress in cancer survivors compared with a nonexercising cancer control group (CON).

METHODS

Fifteen cancer patients and seven age-matched individuals with no history of cancer (NC) participated in this study. A blood draw and assessments of muscular strength and CRF were administered to cancer survivors within 6 wk of completing radiation or chemotherapy, and again 10 wk later. Eight cancer patients completed a 10-wk supervised exercise intervention, whereas seven continued standard care. Baseline oxidative stress was compared between cancer patients and the NC group. Changes in plasma protein carbonyls, 8-OHdG, and Trolox equivalent antioxidant capacity were compared between groups using repeated-measures ANOVA, and correlations between fitness and oxidative stress changes were evaluated.

RESULTS

Baseline antioxidant capacity was significantly lower, and plasma protein carbonyls were significantly higher in cancer patients compared with NC (P = 0.001). EX had a significant increase in antioxidant capacity (P < 0.001) and decrease in protein carbonyls (P = 0.023), whereas CON did not. Improvements in composite arm (41%, P = 0.002) and leg strength (34%, P = 0.008), isometric handgrip strength (11%, P = 0.015), and V˙O2peak (16%, P = 0.018) were significant in EX but not in CON. 8-OHdG changes were significantly correlated with changes in V˙O2peak (r = -0.89, P < 0.001), arm strength (r = -0.67, P = 0.004), and leg strength (r = -0.56, P = 0.019).

CONCLUSION

A whole-body exercise intervention for cancer survivors may be an effective method of concurrently increasing muscular strength, CRF, and antioxidant capacity while decreasing markers of oxidative stress.

High-Resolution 4C Reveals Rapid p53-Dependent Chromatin Reorganization of the CDKN1A Locus in Response to Stress

A regulatory program involving hundreds of genes is coordinated by p53 to prevent carcinogenesis in response to stress. Given the importance of chromatin loops in gene regulation, we investigated whether DNA interactions participate in the p53 stress response. To shed light on this issue, we measured the binding dynamics of cohesin in response to stress. We reveal that cohesin is remodeled at specific loci during the stress response and that its binding within genes negatively correlates with transcription. At p53 target genes, stress-induced eviction of cohesin from gene bodies is concomitant to spatial reorganization of loci through the disruption of functional chromatin loops. These findings demonstrate that chromatin loops can be remodeled upon stress and contribute to the p53-driven stress response. Additionally, we also propose a mechanism whereby transcription-coupled eviction of cohesin from CDKN1A might act as a molecular switch to control spatial interactions between regulatory elements.

5-Fluorouracil-induced RNA stress engages a TRAIL-DISC-dependent apoptosis axis facilitated by p53

Despite recent advances in targeted therapeutics, administration of 5-fluorouracil (5-FU) remains a common clinical strategy for post-surgical treatment of solid tumors. Although it has been proposed that RNA metabolism is disturbed by 5-FU treatment, the key cytotoxic response is believed to be enzymatic inhibition of thymidylate synthase resulting in nucleotide pool disproportions. An operating p53 tumor suppressor signaling network is in many cases essential for the efficiency of chemotherapy, and malfunctions within this system remain a clinical obstacle. Since the fate of chemotherapy-insensitive tumor cells is rarely described, we performed a comparative analysis of 5-FU toxicity in p53-deficient cells and conclude that p53 acts as a facilitator rather than a gatekeeper of cell death. Although p53 can act as a regulator of several cellular stress responses, no rerouting of cell death mode was observed in absence of the tumor suppressor. Thus, the final death outcome of 5-FU-treated p53^−/− cells is demonstrated to be caspase-dependent, but due to a slow pace, accumulation of mitochondrial reactive oxygen species contributes to necrotic characteristics. The oligomerization status of the p53 target gene DR5 is determined as a significant limiting factor for the initiation of caspase activity in an intracellular TRAIL-dependent manner. Using several experimental approaches, we further conclude that RNA- rather than DNA-related stress follows by caspase activation irrespectively of p53 status. A distinct 5-FU-induced stress mechanism is thereby functionally connected to a successive and discrete cell death signaling pathway. Finally, we provide evidence that silencing of PARP-1 function may be an approach to specifically target p53-deficient cells in 5-FU combinatorial treatment strategies. Together, our results disclose details of impaired cell death signaling engaged as a consequence of 5-FU chemotherapy. Obtained data will contribute to the comprehension of factors restraining 5-FU efficiency, and by excluding DNA as the main stress target in some cell types they propose alternatives to currently used and suggested synergistic treatment regimens.

The Hallmarks of Cancer from a Redox Perspective

SIGNIFICANCE

For a healthy cell to turn into a cancer cell and grow out to become a tumor, it needs to undergo a series of complex changes and acquire certain traits, summarized as "The Hallmarks of Cancer." These hallmarks can all be regarded as the result of altered signal transduction cascades and an understanding of these cascades is essential for cancer treatment.

RECENT ADVANCES

Redox signaling is a long overlooked form of signal transduction that proceeds through the reversible oxidation of cysteines in proteins and that uses hydrogen peroxide as a second messenger.

CRITICAL ISSUES

In this article, we provide examples that show that redox signaling is involved in the regulation of proteins and signaling cascades that play roles in every hallmark of cancer.

FUTURE DIRECTIONS

An understanding of how redox signaling and "classical" signal transduction are intertwined could hold promising strategies for cancer therapy in the future. Antioxid. Redox Signal. 25, 300-325.

Dual role of macrophages in the response of C26 colon carcinoma cells to 5-fluorouracil administration

Previous studies have demonstrated that tumor-associated macrophages (TAMs) are pivotal players in tumor progression via modulation of tumor angiogenesis, inflammation, metastasis and oxidative stress, as well as of the response of cancer cells to cytotoxic drugs. Nevertheless, the role of TAMs in the prognosis of colorectal cancer remains controversial. Therefore, the present study aimed to investigate how TAMs mediate the response of C26 colon carcinoma cells to the cytotoxic drug 5-fluorouracil (5-FU), upon TAM co-cultivation with these cancer cells in vitro. In this respect, 5-FU cytotoxicity was assessed in C26 cells in standard culture and in a co-culture with peritoneal macrophages, the production of NF-κB was determined by western blot analysis, and the production of angiogenic/inflammatory proteins in each experimental model was evaluated by protein array analysis. To gain further evidence of the effect of TAMs on oxidative stress, malondialdehyde was measured through high-performance liquid chromatography, and the total nonenzymatic antioxidant levels and the production of nitrites were measured through colorimetric assays. The results demonstrated that TAMs exerted a dual role in the response of C26 cells to 5-FU administration in the co-culture model. Thus, on one side, TAMs sensitized C26 cells to 5-FU administration through inhibition of the production of inflammatory and angiogenic proteins in these cancer cells; however, they also protected cancer cells against 5-FU-induced oxidative stress. Collectively, the present findings suggest that the combined administration of 5-FU with pharmacological agents that prevent TAMs to maintain the physiological range of tumor cell oxidative stress may highly improve the therapeutic potential of this drug.

Enhancement of anti-tumor effects of 5-fluorouracil on hepatocellular carcinoma by low-intensity ultrasound

Background

Hepatocellular carcinoma (HCC) accounts for 75 % of liver cancers and is the second most lethal cancer, associated with its multiple etiologies, poor prognosis and resistance to chemotherapy drugs. Chemotherapy treatment on HCC suffers low efficacy of drug uptake and can produce a range of side effects. Here we report an investigation on the effect of a combined treatment on human hepatocellular carcinoma BEL-7402 cells using low-intensity ultrasound (US) and 5-fluorouracil (5-FU).

Methods

The uptake of 5-FU was measured by the high-performance liquid chromatography (HPLC). DNA damage was detected by the comet assay. MTT assay was used to examine cell viability. Intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (Δψm) were respectively detected by the fluorescent probes DCFH-DA or JC-1. Endogenous apoptosis-associated proteins were analyzed by the western blot and immunohistochemistry. Histopathological changes were evaluated by the hematoxylin and eosin (H&E) staining. Cell apoptosis was evaluated by the TUNEL and flow cytometry assays. Cell proliferation was measured using the immunohistochemical staining of PCNA.

Results

Our results showed that low-intensity US (1.1 MHz, 1.0 W/cm², 10 % duty cycle) significantly enhanced the uptake of 5-FU, 5-FU-mediated DNA damage and reactive oxygen species (ROS) generation. The increased ROS production up-regulated the p53 protein level, which led to the up-regulation of Bax and down-regulation of Bcl-2. The enhancement of ROS generation and the activation of the apoptosis-associated proteins further triggered the collapse of mitochondrial membrane potential, released cytochrome c from mitochondria into cytosol and activated the mitochondria-caspase pathway, and cell apoptosis. Such enhanced effects could be partially blocked by the ROS scavenger N-acetylcysteine (NAC). Overall, low-intensity US combined with 5-FU led to an effective inhibition of tumor growth and prolonged overall survival of BEL-7402 HCC-bearing nude mice by more than 15 % compared with 5-FU treatment alone.

Conclusions

Our results showed that low-intensity ultrasound combined with 5-FU produced much enhanced synergistic anti-tumor effects via enhanced ROS production in treating HCC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0349-4) contains supplementary material, which is available to authorized users.

TP53 mutation, mitochondria and cancer

Under normal conditions, basal levels of wild-type p53 promote mitochondrial function through multiple mechanisms. Remarkably, some missense mutations of p53, in contrast to the null state, can result in the retention of its metabolic activities. These effects are particularly prominent in the mitochondria and demonstrate a functional role for mutant p53 in cancer metabolism. This review summarizes accumulating data on the mechanisms by which p53 missense mutations can regulate mitochondrial metabolism and promote the viability and survival of both normal and cancer cells, thus acting as a double edged sword for the host. Greater understanding of these mechanisms may provide insights for developing new treatment or preventive strategies against cancer.

Network Analysis Identifies Mitochondrial Regulation of Epidermal Differentiation by MPZL3 and FDXR

Current gene expression network approaches commonly focus on transcription factors (TFs), biasing network-based discovery efforts away from potentially important non-TF proteins. We developed proximity analysis, a network reconstruction method that uses topological constraints of scale-free, small-world biological networks to reconstruct relationships in eukaryotic systems, independent of subcellular localization. Proximity analysis identified MPZL3 as a highly connected hub that is strongly induced during epidermal differentiation. MPZL3 was essential for normal differentiation, acting downstream of p63, ZNF750, KLF4, and RCOR1, each of which bound near the MPZL3 gene and controlled its expression. MPZL3 protein localized to mitochondria, where it interacted with FDXR, which was itself also found to be essential for differentiation. Together, MPZL3 and FDXR increased reactive oxygen species (ROS) to drive epidermal differentiation. ROS-induced differentiation is dependent upon promotion of FDXR enzymatic activity by MPZL3. ROS induction by the MPZL3 and FDXR mitochondrial proteins is therefore essential for epidermal differentiation.

Mitochondria-targeted molecules MitoQ and SS31 reduce mutant huntingtin-induced mitochondrial toxicity and synaptic damage in Huntington's disease

The objective of this study was to determine the protective effects of the mitochondria-targeted molecules MitoQ and SS31 in striatal neurons that stably express mutant huntingtin (Htt) (STHDhQ111/Q111) in Huntington's disease (HD). We studied mitochondrial and synaptic activities by measuring mRNA and the protein levels of mitochondrial and synaptic genes, mitochondrial function, and ultra-structural changes in MitoQ- and SS31-treated mutant Htt neurons relative to untreated mutant Htt neurons. We used gene expression analysis, biochemical methods, transmission electron microscopy (TEM) and confocal microscopy methods. In the MitoQ- and SS31-treated mutant Htt neurons, fission genes Drp1 and Fis1 were down-regulated, and fusion genes Mfn1, Mfn2 and Opa1 were up-regulated relative to untreated neurons, suggesting that mitochondria-targeted molecules reduce fission activity. Interestingly, the mitochondrial biogenesis genes PGC1α, PGC1β, Nrf1, Nrf2 and TFAM were up-regulated in MitoQ- and SS31-treated mutant Htt neurons. The synaptic genes synaptophysin and PSD95 were up-regulated, and mitochondrial function was normal in the MitoQ- and SS31-treated mutant Htt neurons. Immunoblotting findings of mitochondrial and synaptic proteins agreed with the mRNA findings. TEM studies revealed decreased numbers of structurally intact mitochondria in MitoQ- and SS31-treated mutant Htt neurons. These findings suggest that mitochondria-targeted molecules MitoQ and SS31 are protective against mutant Htt-induced mitochondrial and synaptic damage in HD neurons, and these mitochondria-targeted molecules are potential therapeutic molecules for the treatment of HD neurons.

JNK suppression of chemotherapeutic agents-induced ROS confers chemoresistance on pancreatic cancer stem cells

Chemoresistance associated with cancer stem cells (CSCs), which is now being held responsible for the pervasive therapy resistance of pancreatic cancer, poses a major challenge to the successful management of this devastating malignancy. However, the molecular mechanism underlying the marked chemoresistance of pancreatic CSCs remains largely unknown. Here we show that JNK, which is upregulated in pancreatic CSCs and contributes to their maintenance, is critically involved in the resistance of pancreatic CSCs to 5-fluorouracil (5-FU) and gemcitabine (GEM). We found that JNK inhibition effectively sensitizes otherwise chemoresistant pancreatic CSCs to 5-FU and GEM. Significantly, JNK inhibition promoted 5-FU- and GEM-induced increase in intracellular reactive oxygen species (ROS), and scavenging intracellular ROS by use of N-acetylcysteine impaired JNK inhibition-mediated promotion of the cytotoxicity of 5-FU and GEM. Our findings thus suggest that JNK may contribute to the chemoresistance of pancreatic CSCs through prevention of chemotherapeutic agents-induced increase in intracellular ROS. Our findings also suggest that JNK inhibition combined with 5-FU- and/or GEM-based regimens may be a rational therapeutic approach to effectively eliminate pancreatic CSCs.

Innovative Target Therapies Are Able to Block the Inflammation Associated with Dysfunction of the Cholesterol Biosynthesis Pathway

The cholesterol pathway is an essential biochemical process aimed at the synthesis of bioactive molecules involved in multiple crucial cellular functions. The end products of this pathway are sterols, such as cholesterol, which are essential components of cell membranes, precursors of steroid hormones, bile acids and other molecules such as ubiquinone. Several diseases are caused by defects in this metabolic pathway: the most severe forms of which cause neurological involvement (psychomotor retardation and cerebellar ataxia) as a result of a variety of cellular impairments, including mitochondrial dysfunction. These pathologies are induced by convergent mechanisms in which the mitochondrial unit plays a pivotal role contributing to defective apoptosis, autophagy and mitophagy processes. Unraveling these mechanisms would contribute to the development of effective drug treatments for these disorders. In addition, the development of biochemical models could have a substantial impact on the understanding of the mechanism of action of drugs that act on this pathway in multifactor disorders. In this review we will focus in particular on inhibitors of cholesterol synthesis, mitochondria-targeted drugs and inhibitors of the inflammasome.

EglN2 positively regulates mitochondrial function in breast cancer

Oxygen sensing is associated with mitochondrial function. EglN2, which contributes to breast tumorigenesis as a prolyl hydroxylase, has recently been identified as a transcription co-activator through interaction with NRF1 and PGC1α to regulate mitochondrial function under conditions of normoxia and hypoxia. FDXR is the important downstream target gene that mediates this regulation.

Oxidative Stress and Response to Thymidylate Synthase-Targeted Antimetabolites

Thymidylate synthase (TYMS; EC 2.1.1.15) catalyzes the reductive methylation of 2'-deoxyuridine-5'-monophosphate (dUMP) by N(5),N(10)-methyhlenetetrahydrofolate, forming dTMP for the maintenance of DNA replication and repair. Inhibitors of TYMS have been widely used in the treatment of neoplastic disease. A number of fluoropyrimidine and folate analogs have been developed that lead to inhibition of the enzyme, resulting in dTMP deficiency and cell death. In the current study, we have examined the role of oxidative stress in response to TYMS inhibitors. We observed that intracellular reactive oxygen species (ROS) concentrations are induced by these inhibitors and promote apoptosis. Activation of the enzyme NADPH oxidase (NOX), which catalyzes one-electron reduction of O2 to generate superoxide (O2 (●-)), is a significant source of increased ROS levels in drug-treated cells. However, gene expression profiling revealed a number of other redox-related genes that may contribute to ROS generation. TYMS inhibitors also induce a protective response, including activation of the transcription factor nuclear factor E2-related factor 2 (NRF2), a critical mediator of defense against oxidative and electrophilic stress. Our results show that exposure to TYMS inhibitors induces oxidative stress that leads to cell death, while simultaneously generating a protective response that may underlie resistance against such death.

Synthesis of triphenylphosphonium vitamin E derivatives as mitochondria-targeted antioxidants

A series of mitochondria-targeted antioxidants comprising a lipophilic triphenylphosphonium cation attached to the antioxidant chroman moiety of vitamin E by an alkyl linker have been prepared. The synthesis of a series of mitochondria-targeted vitamin E derivatives with a range of alkyl linkers gave compounds of different hydrophobicities. This work will enable the dependence of antioxidant defence on hydrophobicity to be determined in vivo.

EglN2 associates with the NRF1-PGC1α complex and controls mitochondrial function in breast cancer

The EglN2/PHD1 prolyl hydroxylase is an important oxygen sensor contributing to breast tumorigenesis. Emerging studies suggest that there is functional cross talk between oxygen sensing and mitochondrial function, both of which play an essential role for sustained tumor growth. However, the potential link between EglN2 and mitochondrial function remains largely undefined. Here, we show that EglN2 depletion decreases mitochondrial respiration in breast cancer under normoxia and hypoxia, which correlates with decreased mitochondrial DNA in a HIF1/2α-independent manner. Integrative analyses of gene expression profile and genomewide binding of EglN2 under hypoxic conditions reveal nuclear respiratory factor 1 (NRF1) motif enrichment in EglN2-activated genes, suggesting NRF1 as an EglN2 binding partner. Mechanistically, by forming an activator complex with PGC1α and NRF1 on chromatin, EglN2 promotes the transcription of ferridoxin reductase (FDXR) and maintains mitochondrial function. In addition, FDXR, as one of effectors for EglN2, contributes to breast tumorigenesis in vitro and in vivo. Our findings suggest that EglN2 regulates mitochondrial function in ERα-positive breast cancer.

The influence of p53 status on the cytotoxicity of fluorinated pyrimidine L-nucleosides

Fluorinated nucleoside analogues are a major class of cancer chemotherapy agents, and include the drugs 5-fluorouracil (5FU) and 5-fluoro-2'-deoxyuridine (FdUrd). The aim of this study was to examine the cellular toxicity of two novel fluorinated pyrimidine L-nucleosides that are enantiomers of D-nucleosides and may be able to increase selectivity for cancer cells as a result of their unnatural L-configuration. Two fluorinated pyrimidine L-nucleosides were examined in this study, L110 ([β-L, β-D]-5-fluoro-2'-deoxyuridine) and L117 (β-L-deoxyuridine:β-D-5'-fluoro-2'-deoxyuridine). The cytotoxicity of these L-nucleoside was determined in primary mouse fibroblasts and was compared with 5FU and FdUrd. In addition, the influence of p53 status on cytotoxicity was investigated. These cytotoxicity assays were performed on a matched set of primary mouse fibroblasts that were either wild type or null for the p53 tumour suppressor gene. It was found that cells lacking functional p53 were over 7500 times more sensitive to the drugs L110, L117 and FdUrd than cells containing wild type p53.

MicroRNA-339-5p inhibits colorectal tumorigenesis through regulation of the MDM2/p53 signaling

Tumor suppressor p53 plays a central role in tumor suppression. To ensure its proper function, the levels and activity of p53 are under a tight regulation in cells. MicroRNAs are short non-coding RNAs that play an important role in regulation of gene expression. Recently, microRNA-339-5p has been reported to be frequently down-regulated in colorectal cancer, and furthermore, its down-regulation is associated with poor prognosis in cancer patients, which strongly suggests a tumor suppressive function of microRNA-339-5p in colorectal cancer. In this study, we found that microRNA-339-5p directly represses the expression of MDM2, a key negative regulator of p53, through binding to MDM2 3′-UTR in colorectal cancer cells. Through the down-regulation of MDM2, microRNA-339-5p increases p53 protein levels and functions, including p53 transcriptional activity and p53-mediated apoptosis and senescence in response to stress. Furthermore, microRNA-339-5p inhibits the migration and invasion of colorectal cancer cells and the growth of colorectal xenograft tumors in a largely p53-dependent manner. Our results highlighted an important role of microRNA-339-5p in suppression of colorectal tumorigenesis, and also revealed that regulating the p53 function is an important mechanism for microRNA-339-5p in tumor suppression.

Sensitivity to anti-Fas is independent of increased cathepsin D activity and adrenodoxin reductase expression occurring in NOS-3 overexpressing HepG2 cells

Stable overexpression of endothelial nitric oxide synthase (NOS-3) in HepG2 cells (4TO-NOS) leads to increased nitro-oxidative stress and upregulation of the cell death mediators p53 and Fas. Thus, NOS-3 overexpression has been suggested as a useful antiproliferative mechanism in hepatocarcinoma cells. We aimed to identify the underlying mechanism of cell death induced by NOS-3 overexpression at basal conditions and with anti-Fas treatment. The intracellular localization of NOS-3, the nitro-oxidative stress and the mitochondrial activity were analysed. In addition, the protein expression profile in 4TO-NOS was screened for differentially expressed proteins potentially involved in the induction of apoptosis. NOS-3 localization in the mitochondrial outer membrane was not associated with changes in the respiratory cellular capacity, but was related to the mitochondrial biogenesis increase and with a higher protein expression of mitochondrial complex IV. Nitro-oxidative stress and cell death in NOS-3 overexpressing cells occurred with the expression increase of pro-apoptotic genes and a higher expression/activity of the enzymes adrenodoxin reductase mitochondrial (AR) and cathepsin D (CatD). CatD overexpression in 4TO-NOS was related to the apoptosis induction independently of its catalytic activity. In addition, CatD activity inhibition by pepstatin A was not effective in blocking apoptosis induced by anti-Fas. In summary, NOS-3 overexpression resulted in an increased sensitivity to anti-Fas induced cell death, independently of AR expression and CatD activity.

Mechanisms of chemotherapy-induced behavioral toxicities

While chemotherapeutic agents have yielded relative success in the treatment of cancer, patients are often plagued with unwanted and even debilitating side-effects from the treatment which can lead to dose reduction or even cessation of treatment. Common side effects (symptoms) of chemotherapy include (i) cognitive deficiencies such as problems with attention, memory and executive functioning; (ii) fatigue and motivational deficit; and (iii) neuropathy. These symptoms often develop during treatment but can remain even after cessation of chemotherapy, severely impacting long-term quality of life. Little is known about the underlying mechanisms responsible for the development of these behavioral toxicities, however, neuroinflammation is widely considered to be one of the major mechanisms responsible for chemotherapy-induced symptoms. Here, we critically assess what is known in regards to the role of neuroinflammation in chemotherapy-induced symptoms. We also argue that, based on the available evidence, neuroinflammation is unlikely the only mechanism involved in the pathogenesis of chemotherapy-induced behavioral toxicities. We evaluate two other putative candidate mechanisms. To this end we discuss the mediating role of damage-associated molecular patterns (DAMPs) activated in response to chemotherapy-induced cellular damage. We also review the literature with respect to possible alternative mechanisms such as a chemotherapy-induced change in the bioenergetic status of the tissue involving changes in mitochondrial function in relation to chemotherapy-induced behavioral toxicities. Understanding the mechanisms that underlie the emergence of fatigue, neuropathy, and cognitive difficulties is vital to better treatment and long-term survival of cancer patients.

Dissecting the mechanism of colorectal tumorigenesis based on RNA-sequencing data

OBJECTIVE

This study aimed to identify the differentially expressed genes (DEGs), mutated genes and fusion genes in colorectal cancer.

MATERIALS AND METHODS

RNA-sequencing data (ID: SRP009386) from cancerous, paracancerous non-tumor and distant normal tissue from one Chinese patient with stage III colorectal cancer were downloaded from Sequence Read Archive. Quality control was checked using FastQC, followed by sequence alignment against the hg19 reference genome using TopHat v1.3.3. The expression levels were quantified using Cufflinks, followed by DEGs screening using NOISeq. Enrichment analysis was performed using DAVID. Transcription factors were screened using TRANSFA. Mutated loci were identified using SAMTools and VCFTools. Gene fusion events were detected by TopHat-fusion.

RESULTS

In total 2440, 1887 and 834 DEGs were respectively detected in cancerous vs. normal tissue, cancerous vs. paracancerous tissue and paracancerous vs. normal tissue. The up-regulated genes from cancerous and paracancerous tissue compared with normal tissue were enriched in "extracellular matrix receptor interaction" and "focal adhesion pathway" as well as some biological processes except for "negative regulation of programmed cell death" uniquely presenting in cancer. Dysregulated transcription factors including SOX4, BCL6, CEBPB and MSX2 were enriched in the unique biological process. Trp53 was identified with one mutated locus 7577142 (C → T) on chromosome 17. BCL6 also experienced missense mutation. Additionally, COL1A1-PPP2R2C and EXPH5-COL1A2 were observed fusion genes in cancer tissue.

CONCLUSIONS

The unique biological process in cancer tissue may be the cause for colorectal carcinogenesis. The screened transcription factors, mutated genes and fusion genes may contribute to the progression of colorectal cancer.

Oxidative stress-related genetic polymorphisms are associated with the prognosis of metastatic gastric cancer patients treated with epirubicin, oxaliplatin and 5-fluorouracil combination chemotherapy

Background

Oxidative stress genes are related to cancer development and treatment response. In this study, we aimed to determine the predictive and prognostic roles of oxidative stress-related genetic polymorphisms in metastatic gastric cancer (MGC) patients treated with chemotherapy.

Methods

In this retrospective study, we genotyped nine oxidative stress-related single nucleotide polymorphisms (SNPs) in NQO1, SOD2, SOD3, PON1, GSTP1, GSTT1, and NOS3 (rs1800566, rs10517, rs4880, rs1799895, rs662, rs854560, rs1695, rs2266637, rs1799983, respectively) in 108 consecutive MGC patients treated with epirubicin, oxaliplatin, and 5-fluorouracil (EOF) regimen as the first-line chemotherapy and analyzed the association between the genotypes and the disease control rate (DCR), progression-free survival (PFS), and overall survival (OS).

Results

We found that, in addition to a lower pathological grade (p = 0.017), NQO1 rs1800566 CT/TT genotype was an independent predictive factor of poor PFS (hazard ratio [HR] = 1.97, 95% confidence interval [CI] = 1.23–3.16; p = 0.005). PON1 rs662 AA/AG genotype was significantly associated with poor OS (HR = 1.95, 95% CI = 1.07–3.54; p = 0.029). No associations were detected between the nine SNPs and DCR.

Conclusions

NQO1 rs1800566 is an independent predictive factor of PFS for MGC patients treated with EOF chemotherapy, and PON1 rs662 is a noteworthy prognostic factor of OS. Information on oxidative stress-related genetic variants may facilitate optimization of individualized chemotherapy in clinical practice.