Overexpression of cytochrome P450 NADPH reductase sensitises MDA 231 breast carcinoma cells to 5-fluorouracil: possible mechanisms involved

POR overexpression induces tamoxifen-resistance in breast cancer through the STAT1/c-Myc pathway

Breast cancer is the most common cancer in women worldwide. Although tamoxifen (TAM), a selective estrogen receptor (ER) modulator, is widely used to treat ER-positive breast cancers, resistance to TAM remains a major clinical problem. NADPH-dependent cytochrome P450 reductase (POR) is known to participate in drug metabolism and steroid metabolism. Recent studies showed that high POR expression was correlated with poor outcomes in triple-negative breast cancer (TNBC), and POR might be a prognostic biomarker in TNBC. However, the role of POR in TAM resistance is still elusive. In this study, we found that high POR expression was associated with poor prognosis of ER-positive and TAM-treated breast cancer patients. In addition, COX analysis showed that POR expression was an independent prognostic biomarker for ER-positive as well as TAM-treated breast cancer patients. Furthermore, our results suggested that POR overexpression promoted TAM resistance by activating the STAT1/c-Myc pathway in ER-positive breast cancer cells. Immunohistochemical analysis showed that high POR/STAT1 expression was correlated with poor prognosis in TAM-treated breast cancer patients. Notably, combined treatment with TAM and a specific STAT1 inhibitor Fludarabine was more effective for inhibiting TAM-resistant breast cancer cells. Altogether, our findings suggested that POR overexpression induced TAM resistance through STAT1/c-Myc pathway and might serve as an independent prognostic biomarker in TAM-treated breast cancer patients. Combining TAM and STAT1 inhibitors might be an effective strategy for treating POR-induced TAM-resistant breast cancer.

Bioactive three-dimensional silk composite in vitro tumoroid model for high throughput screening of anticancer drugs

HYPOTHESIS

Modeling three-dimensional (3D) in vitro culture systems recapitulating spatiotemporal characteristics of native tumor-mass has shown tremendous potential as a pre-clinical tool for drug screening. However, their applications in clinical settings are still limited due to inappropriate recapitulation of tumor topography, culture instability, and poor durability of niche support.

EXPERIMENTS

Here, we have fabricated a bio-active silk composite scaffold assimilating tunable silk from Bombyx mori and - arginine-glycine-aspartate (RGD) rich silk from Antheraea assama to provide a better 3D-matrix for breast (MCF 7) and liver (HepG2) tumoroids. Cellular mechanisms underlying physiological adaptations in 3D constructs and subsequent drug responses were compared with conventional monolayer and multicellular spheroid culture.

FINDINGS

Silk composite matrix assists prolonged growth and high metabolic activity (Cytochrome P450 reductase) in breast and liver 3D-tumoroids. Enhanced stemness expression (Cell surface adhesion receptor; CD44, Aldehyde dehydrogenase 1) and epithelial-mesenchymal-transition markers (E-cadherin, Vimentin) at transcript and protein levels demonstrate that bio-active matrix-assisted 3D environment augmenting metastatic potential in tumoroids. Together, enhanced secretion of Transforming growth factor β (TGFβ), anchorage-independency, and colony-forming potential of cells in the 3D-tumoroids further corroborates the aggressive behavior of cells. Moreover, the multilayered 3D-tumoroids exhibit decreased sensitivity to some known anticancer drugs (Doxorubicin and Paclitaxel). In conclusion, the bio-active silk composite matrix offers an advantage in developing robust and sustainable 3D tumoroids for a high-throughput drug screening platform.

Biological Entanglement-Like Effect After Communication of Fish Prior to X-Ray Exposure

The phenomenon by which irradiated organisms including cells in vitro communicate with unirradiated neighbors is well established in biology as the radiation-induced bystander effect (RIBE). Generally, the purpose of this communication is thought to be protective and adaptive, reflecting a highly conserved evolutionary mechanism enabling rapid adjustment to stressors in the environment. Stressors known to induce the effect were recently shown to include chemicals and even pathological agents. The mechanism is unknown but our group has evidence that physical signals such as biophotons acting on cellular photoreceptors may be implicated. This raises the question of whether quantum biological processes may occur as have been demonstrated in plant photosynthesis. To test this hypothesis, we decided to see whether any form of entanglement was operational in the system. Fish from 2 completely separate locations were allowed to meet for 2 hours either before or after which fish from 1 location only (group A fish) were irradiated. The results confirm RIBE signal production in both skin and gill of fish, meeting both before and after irradiation of group A fish. The proteomic analysis revealed that direct irradiation resulted in pro-tumorigenic proteomic responses in rainbow trout. However, communication from these irradiated fish, both before and after they had been exposed to a 0.5 Gy X-ray dose, resulted in largely beneficial proteomic responses in completely nonirradiated trout. The results suggest that some form of anticipation of a stressor may occur leading to a preconditioning effect or temporally displaced awareness after the fish become entangled.

Effect of NADPH-cytochrome P450 reductase on all-trans-retinoic acid efficacy and cytochrome P450 26A1 expression in human myeloid leukaemia HL-60 cells

OBJECTIVES

All-trans-retinoic acid (ATRA), a naturally occurring metabolite of vitamin A, has been shown to have great potential as an antitumorigenic drug to treat acute leukaemia by promoting cancer cell differentiation. Cytochrome P450 oxidoreductase (POR) is the only obligate electron donor for all of the microsomal cytochrome P450 enzymes including CYP26A1 which is highly specific for ATRA metabolism and efficacy in human myeloid leukaemia cells. In this study, we aimed to investigate the effect of POR on ATRA efficacy and CYP26A1 expression in human myeloid leukaemia HL-60 cells.

METHODS

Stably expressed POR and POR-RNAi HL-60 cell lines were established by transfecting POR overexpression or RNAi (RNA interference) vectors mediated by lentivirus. The protein expression of POR and CYP26A1 was examined by Western blot. The potential roles of POR on ATRA efficacy in HL-60 cells were explored by cell viability assay, cell cycle distribution, cellular differentiation and apoptosis analysis.

KEY FINDINGS

All-trans-retinoic acid treatment caused the expression of POR upregulation and CYP26A1 downregulation in dose- and time-dependent manners. POR overexpression decreased CYP26A1 expression in HL-60 cells. When POR gene was interfered, the downregulation of CYP26A1 expression by ATRA was abolished. In addition, POR overexpression in HL-60 cells significantly compromised ATRA-induced cell proliferation inhibition, cell cycle arrest, differentiation and apoptosis, whereas downregulation of POR significantly potentiated ATRA effects.

CONCLUSIONS

Our study therefore suggested that POR played an important role in regulating ATRA efficacy and CYP26A1 expression in HL-60 cells.

A highly efficient tumor-infiltrating MDSC differentiation system for discovery of anti-neoplastic targets, which circumvents the need for tumor establishment in mice

Myeloid-derived suppressor cells (MDSCs) exhibit potent immunosuppressive activities in cancer. MDSCs infiltrate tumors and strongly inhibit cancer-specific cytotoxic T cells. Their mechanism of differentiation and identification of MDSC-specific therapeutic targets are major areas of interest. We have devised a highly efficient and rapid method to produce very large numbers of melanoma-infiltrating MDSCs ex vivo without inducing tumors in mice. These MDSCs were used to study their differentiation, immunosuppressive activities and were compared to non-neoplastic counterparts and conventional dendritic cells using unbiased systems biology approaches. Differentially activated/deactivated pathways caused by cell type differences and by the melanoma tumor environment were identified. MDSCs increased the expression of trafficking receptors to sites of inflammation, endocytosis, changed lipid metabolism, and up-regulated detoxification pathways such as the expression of P450 reductase. These studies uncovered more than 60 potential novel therapeutic targets. As a proof of principle, we demonstrate that P450 reductase is the target of pro-drugs such as Paclitaxel, which depletes MDSCs following chemotherapy in animal models of melanoma and in human patients. Conversely, P450 reductase protects MDSCs against the cytotoxic actions of other chemotherapy drugs such as Irinotecan, which is ineffective for the treatment of melanoma.

CYP3A4 overexpression enhances apoptosis induced by anticancer agent imidazoacridinone C-1311, but does not change the metabolism of C-1311 in CHO cells

AIM

To examine whether CYP3A4 overexpression influences the metabolism of anticancer agent imidazoacridinone C-1311 in CHO cells and the responses of the cells to C-1311.

METHODS

Wild type CHO cells (CHO-WT), CHO cells overexpressing cytochrome P450 reductase (CPR) [CHO-HR] and CHO cells coexpressing CPR and CYP3A4 (CHO-HR-3A4) were used. Metabolic transformation of C-1311 and CYP3A4 activity were measured using RP-HPLC. Flow cytometry analyses were used to examine cell cycle, caspase-3 activity and cell apoptosis. The expression of pH 6.0-dependent β-galactosidase (SA-β-gal) was studied to evaluate accelerated senescence. ROS generation was analyzed with CM-H2 DCFDA staining.

RESULTS

CYP3A4 overexpression did not change the metabolism of C-1311 in CHO cells: the levels of all metabolites of C-1311 increased with the exposure time to a similar extent, and the differences in the peak level of the main metabolite M3 were statistically insignificant among the three CHO cell lines. In CHO-HR-3A4 cells, C-1311 effectively inhibited CYP3A4 activity without affecting CYP3A4 protein level. In the presence of C-1311, CHO-WT cells underwent rather stable G2/M arrest, while the two types of transfected cells only transiently accumulated at this phase. C-1311-induced apoptosis and necrosis in the two types of transfected cells occurred with a significantly faster speed and to a greater extent than in CHO-WT cells. Additionally, C-1311 induced ROS generation in the two types of transfected cells, but not in CHO-WT cells. Moreover, CHO-HR-3A4 cells that did not die underwent accelerated senescence.

CONCLUSION

CYP3A4 overexpression in CHO cells enhances apoptosis induced by C-1311, whereas the metabolism of C-1311 is minimal and does not depend on CYP3A4 expression.

Natural antioxidant-isoliquiritigenin ameliorates contractile dysfunction of hypoxic cardiomyocytes via AMPK signaling pathway

Isoliquiritigenin (ISL), a simple chalcone-type flavonoid, is derived from licorice compounds and is mainly present in foods, beverages, and tobacco. Reactive oxygen species (ROS) is a critical factor involved in modulating cardiac stress response signaling during ischemia and reperfusion. We hypothesize that ISL as a natural antioxidant may protect heart against ischemic injury via modulating cellular redox status and regulating cardioprotective signaling pathways. The fluorescent probe H2DCFDA was used to measure the level of intracellular ROS. The glucose uptake was determined by 2-deoxy-D-glucose-(3)H accumulation. The IonOptix System measured the contractile function of isolated cardiomyocytes. The results demonstrated that ISL treatment markedly ameliorated cardiomyocytes contractile dysfunction caused by hypoxia. ISL significantly stimulated cardioprotective signaling, AMP-activated protein kinase (AMPK), and extracellular signal-regulated kinase (ERK) signaling pathways. The ROS fluorescent probe H2DCFDA determination indicated that ISL significantly reduced cardiac ROS level during hypoxia/reoxygenation. Moreover, ISL reduced the mitochondrial potential (Δψ) of isolated mouse cardiomyocytes. Taken together, ISL as a natural antioxidant demonstrated the cardioprotection against ischemic injury that may attribute to the activation of AMPK and ERK signaling pathways and balance of cellular redox status.

Isoliquiritigenin-induced differentiation in mouse melanoma B16F0 cell line

The chemotherapeutical treatment is very limited for malignant melanoma, a highly lethal disease occurs globally. Natural products derived from traditional Chinese medicine licorice are attractive in quest new treatments due to their anti-tumor activities. A new dietary flavonoid isoliquiritigenin (ISL) were thus investigated to indentify its anti-melanoma activities on mouse melanoma B16F0 cells in present study. Using biochemical and free radical biological experiments in vitro, we identified the pro-differentiated profiles of ISL and evaluated the role of reactive oxygen species (ROS) during B16F0 cell differentiation. The data showed a strong dose-response relationship between ISL exposure and the characteristics of B16F0 differentiation in terms of morphology changes and melanogenesis. The accumulated intercellular ROS during exposure are necessary to support ISL-induced differentiation, which was proven by additional redox modulators. It was confirmed further by the relative activities of enzymes and genes modulated melanogenesis in ISL-treatments with or without ROS modulators. The tumorigenicity of ISL-treated cells was limited significantly by using the colony formation assay in vitro and an animal model assay in vivo respectively. Our research demonstrated that isoliquiritigenin is a differentiation-inducing agent, and its mechanisms involve ROS accumulation facilitating melanogenesis.

Effects of transient overexpression or knockdown of cytochrome P450 reductase on reactive oxygen species generation and hypoxia reoxygenation injury in liver cells

1. Literature data suggest that the electron-donating enzyme, cytochrome P450 reductase (CPR), might act as a source of reactive oxygen species (ROS). However, the role of CPR in pathophysiological conditions associated with oxidative stress is unknown. The aim of the present study was to study the role of CPR in the generation of ROS and cellular injury under basal conditions, and after simulated in vitro ischaemia-reperfusion (IR). 2. Plasmid DNA or siRNA approaches were used to transiently overexpress or knockdown the human CPR gene in rat liver epithelial (WB-F344) or human hepatoblastoma (HepG2) cells, respectively. The generation of ROS and/or cellular injury was then studied under the basal conditions and after simulated IR (4 h of ischaemia plus 30 min of reoxygenation). 3. Under the basal conditions, transient overexpression of CPR protein in WB-F344 cells caused a 90% increase in the CPR activity, which was associated with a 100% increase in the ROS production. In contrast, after simulated IR, a 2.5-fold higher CPR activity did not significantly affect the magnitude of ROS generation or cell death. Similarly, although the knockdown of CPR protein resulted in a significant reduction (∼30%) in the CPR activity, the ROS production was not substantially altered after simulated IR in HepG2 cells. 4. Our data suggest that CPR plays a major role in the ROS generation by liver cells under the basal conditions. However, the role of CPR in the ROS generation during simulated in vitro IR injury in these cells is minimal, if any.

Monocytic differentiation of K562 cells induced by proanthocyanidins from grape seeds

Grape seeds procyanidins can inhibit the proliferation of some cancer cell lines and have strong antioxidant activity. The purpose of this study was to investigate whether grape seeds procyanidins affect the proliferation and redifferentiation in K562 cells. The sulforhodamine B colorimetric assay and trypan blue staining were used to measure cell proliferation and survival. Morphological changes, NBT reductive activity, and surface antigens were used to detect redifferentiation of K562 cells. Intracellular reactive oxygen species (iROS) were detected by a fluorescent probe. Grape seeds procyanidins inhibited cell proliferation but the treatment did not appreciably increase lethality. After treatment with grape seeds procyanidins, a typical differentiated morphology was observed. The positive rate of CD11b and CD14 cells and NBT reductive activities increased significantly. As antioxidants, grape seeds procyanidins can induce arrest in the phase G1 and decrease iROS formation. All results indicate that the antioxidant grape seeds procyanidins are likely to induce monocytic differentiation in leukemia cells, mostly through decreasing iROS formation and inducing phase G1 arrest.

Two different docetaxel resistant MCF-7 sublines exhibited different gene expression pattern

The objective of the present study was to investigate gene expression pattern of two docetaxel resistant MCF-7 breast carcinoma sublines step wisely selected in 30 and 120 nM docetaxel. Cell proliferation assay was performed in order to demonstrate development of docetaxel resistance. cDNA microarray analysis was performed using Affymetrix(®) Human Genome U133 Plus 2.0 Arrays in duplicate experiments. Quantitative and semi-quantitative gene expression analysis was also performed to confirm gene expression analysis for selected genes. XTT results demonstrated that 30 (MCF-7/30nM DOC) and 120 nM (MCF-7/120nM DOC) docetaxel selected cells were 13- and 47-fold resistant, respectively. cDNA microarray analysis demonstrated that expression profiles of MCF-7 and MCF-7/30nM DOC were more similar to each other where expression profile of MCF-7/120nM DOC was different as examined by line graphs and scatter plots. 2,837 and 4,036 genes were significantly altered in 30 and 120 nM docetaxel resistant sublines, respectively. Among these, 849 genes were altered in common in two docetaxel resistant sublines. Antiapoptotic gene expression (e.g., Bcl-2 and APRIL) were noticeably altered in MCF-7/30nM DOC. However, docetaxel resistance in MCF-7/120nM DOC were more complicated with the involvement of ECM related gene expression, cytokine and growth factor signaling, ROS metabolism and EMT related gene expression together with higher level of MDR1 expression. Expression profiles in 30 and 120 nM docetaxel resistant sublines changed gradually with increasing resistance index. Drug resistance development seems to be step wise event in MCF-7 cells.

Computational approach to characterization of human liver drug-metabolizing enzymes

Cytochromes P450 are the key enzymes for activating and inactivating many drugs; individual expression levels of CYPs may play a crucial role in drug safety and drug efficacy. Statistical comparison of biochemical profiles of 23 human liver microsomes have been used to characterize human liver samples. The profile included 12 parameters, namely activity of NADPH-cytochrome P450 reductase, cytochrome P450 content and cytochrome P450-dependent monooxygenase activities with marker substrates. Unsupervised statistical methods including cluster analysis and principal component analysis revealed with very high confidence the presence of two groups. Difference between the groups was explained by peculiarities of reductase activity and cytochrome P450 enzyme activities with 7-ethoxyresorufin, 7-methoxyresorufin, 7-methoxycoumarin, 7-benzyloxyresorufin and 7-benzyloxyquinoline. Results of biochemical assays coupled with multidimensional data analysis can be further used for targeted proteomic profiling of microsome oxidation mechanisms.

Compilation of a comprehensive gene panel for systematic assessment of genes that govern an individual’s drug responses

Aims: Polymorphisms of genes involved in the pharmacokinetic and pharmacodynamic processes underlie the divergent drug responses among individuals. Despite some successes in identifying these polymorphisms, the candidate gene approach suffers from insufficient gene coverage whereas the genome-wide association approach is limited by less than ideal coverage of SNPs in some important genes. To expand the potential of the candidate approach, we aim to delineate a comprehensive network of drug-response genes for in-depth genetic studies. Materials & methods: Pharmacologically important genes were extracted from various sources including literatures and web resources. These genes, along with their homologs and regulatory miRNAs, were organized based on their pharmacological functions and weighted by literature evidence and confidence levels. Their coverage was evaluated by analyzing three commercial SNP chips commonly used for genome-wide association studies: Affymetrix SNP array 6.0, Illumina HumanHap1M and Illumina Omni. Results: A panel of drug-response genes was constructed, which contains 923 pharmacokinetic genes, 703 pharmacodynamic genes and 720 miRNAs. There are only 16.7% of these genes whose all known SNPs can be directly or indirectly (r2 > 0.8) captured by the SNP chips with coverage of more than 80%. This is possibly because these SNPs chips have notably poor performance over rare SNPs and miRNA genes. Conclusion: We have compiled a panel of candidate genes that may be pharmacologically important. Using this knowledgebase, we are able to systematically evaluate genes and their variants that govern an individual’s response to a given pharmaceutical therapy. This approach can serve as a necessary complement to genome-wide associations.

Distinct roles of cytochrome P450 reductase in mitomycin C redox cycling and cytotoxicity

Mitomycin c (MMC), a quinone-containing anticancer drug, is known to redox cycle and generate reactive oxygen species. A key enzyme mediating MMC redox cycling is cytochrome P450 reductase, a microsomal NADPH-dependent flavoenzyme. In the present studies, Chinese hamster ovary (CHO) cells overexpressing this enzyme (CHO-OR cells) and corresponding control cells (CHO-WT cells) were used to investigate the role of cytochrome P450 reductase in the actions of MMC. In lysates from both cell types, MMC was found to redox cycle and generate H(2)O(2); this activity was greater in CHO-OR cells (V(max) = 1.2 +/- 0.1 nmol H(2)O(2)/min/mg protein in CHO-WT cells versus 32.4 +/- 3.9 nmol H(2)O(2)/min/mg protein in CHO-OR cells). MMC was also more effective in generating superoxide anion and hydroxyl radicals in CHO-OR cells, relative to CHO-WT cells. Despite these differences in MMC redox cycling, MMC-induced cytotoxicity, as measured by growth inhibition, was similar in the two cell types (IC(50) = 72 +/- 20 nmol/L for CHO-WT and 75 +/- 23 nmol/L for CHO-OR cells), as was its ability to induce G(2)-M and S phase arrest. Additionally, in nine different tumor cell lines, although a strong correlation was observed between MMC-induced H(2)O(2) generation and cytochrome P450 reductase activity, there was no relationship between redox cycling and cytotoxicity. Hypoxia, which stabilizes MMC radicals generated by redox cycling, also had no effect on the sensitivity of tumor cells to MMC-induced cytotoxicity. These data indicate that NADPH cytochrome P450 reductase-mediated MMC redox cycling is not involved in the cytotoxicity of this chemotherapeutic agent.

Isoliquiritigenin induces monocytic differentiation of HL-60 cells

It has been proven that isoliquiritigenin could inhibit the proliferation of some kinds of cancer cell lines and has a strong antioxidative activity. The purpose of this study is to investigate whether the antioxidant isoliquiritigenin affects the proliferation and redifferentiation in HL-60 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) colorimetric method and trypan blue staining were used to measure cell proliferentiation and survival. The morphological changes, nitroblue tetrazolium chloride (NBT) reductive activity, and the CD11b and CD14 surface antigens were used as the biomarkers of redifferentiation of HL-60 cells. The intracellular reactive oxygen species (iROS) level was detected by a fluorescent probe, 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA). Isoliquiritigenin (ISL) inhibited the cell proliferation and decreased the iROS levels in a dose-dependent manner, while the treatment did not increase the lethality rate. After 72 h treatment with 10 microg/ml ISL, a typical differentiated morphology was observed in HL-60 cells, including the decrease of karyoplasmic ratio and the increase of kidney-shape nuclear cells. The positive rate (%) of CD11b (26.4+/-3.90 vs 7.70+/-1.04, P<0.01) and CD14 (20.4+/-2.30 vs 2.63+/-0.133, P<0.01) cells increased significantly. The NBT reductive activity increased 2.3-fold as compared to that of the control group. As an antioxidant, ISL decreased the iROS formation in a dose-dependent manner. All the results indicate that the antioxidant ISL is able to induce the monocytic differentiation in leukemia cells. ISL has the potential as a drug to cure leukemia with fewer side effects.

Genetic alteration of Keap1 confers constitutive Nrf2 activation and resistance to chemotherapy in gallbladder cancer

BACKGROUND & AIMS

Biliary tract cancer (BTC) is a highly malignant tumor, and identification of effective therapeutic targets to improve prognosis is urgently required. Oncogenic activation of survival genes is important for cancer cells to overcome oxidative stresses induced by their microenvironments that include chronic inflammation or exposure to anticancer drugs. We attempted to examine whether deregulation of Nrf2, a master transcriptional factor of various cytoprotective genes against oxidative stress, plays a role in the carcinogenesis of BTC.

METHODS

We screened genetic alteration of Keap1, a negative regulator of Nrf2, in BTC including tumors originated from gallbladder and extra- and intrahepatic bile ducts. Functional analysis of cancer-related mutant Keap1 in Nrf2 repression and the association between Nrf2 activation and resistance to 5-fluorouracil (5-FU) were investigated.

RESULTS

Recurrent (in 1/11 cell lines and 6/53 primary tumors) Keap1 gene alterations were observed in BTC and were especially frequent (4/13, 30.7%) in gallbladder cancer (GBC). These alterations led to a considerable loss of Nrf2 repression activity, caused constitutive activation of Nrf2, and promoted cell proliferation. Down-regulation of Nrf2 activity by either Keap1 complementation or Nrf2 short interference RNA increased sensitivity to 5-FU in Keap1-altered BTC cells.

CONCLUSIONS

Keap1 mutation occurs frequently in GBC. Aberrant Nrf2 activation provoked by Keap1 alteration is one of the molecular mechanisms for chemotherapeutic resistance in GBC and will be a novel therapeutic target as an enhancer of sensitivity to 5-FU-based regimens.