Imatinib and Nilotinib inhibit Bcr-Abl-induced ROS through targeted degradation of the NADPH oxidase subunit p22phox

A bis-pyridinium fullerene derivative induces apoptosis through the generation of ROS in BCR-ABL-positive leukemia cells

A fusion protein, Breakpoint cluster region-Abelson (BCR-ABL) is responsible for the development of chronic myeloid leukemia (CML) and acute lymphocytic leukemia (ALL). Inhibitors against BCR-ABL are effective for the treatment of leukemia; however, a gatekeeper mutation (T315I) in BCR-ABL results in resistance to these inhibitors, which markedly impedes their efficacy. We herein demonstrated that a bis-pyridinium fullerene derivative (BPF) significantly induced apoptosis in human CML-derived K562 cells and ALL-derived SUP-B15 cells via the generation of reactive oxygen species (ROS). BPF reduced the expression of Bcr-Abl mRNA by inhibiting expression of c-Myc through ROS production. BPF also accelerated protein degradation of BCR-ABL through ROS production. Furthermore, BPF down-regulated the expression of not only BCR-ABL but also T315I-mutated BCR-ABL in ROS-dependent manner. As a result, BPF effectively induced apoptosis in transformed Ba/F3 cells expressing both BCR-ABL and T315I-mutated BCR-ABL. Collectively, these results indicate the potential of BPF as an effective leukemia drug that overcomes resistance to BCR-ABL inhibitors.

Reactive Oxygen Species in Acute Lymphoblastic Leukaemia: Reducing Radicals to Refine Responses

Acute lymphoblastic leukaemia (ALL) is the most common cancer diagnosed in children and adolescents. Approximately 70% of patients survive >5-years following diagnosis, however, for those that fail upfront therapies, survival is poor. Reactive oxygen species (ROS) are elevated in a range of cancers and are emerging as significant contributors to the leukaemogenesis of ALL. ROS modulate the function of signalling proteins through oxidation of cysteine residues, as well as promote genomic instability by damaging DNA, to promote chemotherapy resistance. Current therapeutic approaches exploit the pro-oxidant intracellular environment of malignant B and T lymphoblasts to cause irreversible DNA damage and cell death, however these strategies impact normal haematopoiesis and lead to long lasting side-effects. Therapies suppressing ROS production, especially those targeting ROS producing enzymes such as the NADPH oxidases (NOXs), are emerging alternatives to treat cancers and may be exploited to improve the ALL treatment. Here, we discuss the roles that ROS play in normal haematopoiesis and in ALL. We explore the molecular mechanisms underpinning overproduction of ROS in ALL, and their roles in disease progression and drug resistance. Finally, we examine strategies to target ROS production, with a specific focus on the NOX enzymes, to improve the treatment of ALL.

Expression of inducible NOS is indispensable for the antiproliferative and proapoptotic effect of imatinib in BCR-ABL positive cells

Chronic myeloid leukemia (CML) is characterized by constitutive BCR-ABL kinase activity, an aggressive proliferation of immature cells, and reduced differentiation. Targeting tyrosine kinase activity of BCR-ABL with imatinib is an effective therapy for the newly diagnosed CML patients; however, 20%-30% of the patients initially treated with imatinib eventually experience treatment failure. Therefore, early identification of these patients is of high clinical relevance. In the present study, we by undertaking a direct comparison of inducible NOS (iNOS) status in neutrophils from healthy volunteers, newly diagnosed, imatinib responder, and resistant CML patients as well as by conducting in vitro studies in K562 cells demonstrated that inhibition of BCR-ABL by imatinib or siRNA significantly enhanced NO generation and iNOS expression. Indeed, patients exhibiting treatment failure or imatinib resistance were less likely to induce NO generation/iNOS expression. Our findings further demonstrated that imatinib mediated antiproliferative and proapoptotic effect in BCR-ABL⁺ cells associated with enhanced iNOS expression, and it was significantly prevented in the presence of L-NAME, 1400W, or iNOS siRNA. Overexpression of iNOS in K562 cells expectedly enhanced imatinib sensitivity on cytostasis and apoptosis, even at lower concentration (0.1 μM) of imatinib. Mechanistically, imatinib or BCR-ABL siRNA following deglutathionylation of NF-κB, enhanced its binding to iNOS promoter and induced iNOS transcription. Deglutathionylation of procaspase-3 however associated with increased caspase-3 activity and cell apoptosis. Taken together, results obtained suggest that monitoring NO/iNOS level could be useful to identify patients likely to be responsive or resistant to imatinib and can be used to personalized alternative therapy.

Tetrahydrobenzimidazole TMQ0153 triggers apoptosis, autophagy and necroptosis crosstalk in chronic myeloid leukemia

By comparing imatinib-sensitive and -resistant chronic myeloid leukemia (CML) cell models, we investigated the molecular mechanisms by which tetrahydrobenzimidazole derivative TMQ0153 triggered caspase-dependent apoptosis at low concentrations accompanied by loss of mitochondrial membrane potential (MMP) and increase of cytosolic free Ca²⁺ levels. Interestingly, at higher concentrations, TMQ0153 induced necroptotic cell death with accumulation of ROS, both preventable by N-acetyl-L-cysteine (NAC) pretreatment. At necroptosis-inducing concentrations, we observed increased ROS and decreased ATP and GSH levels, concomitant with protective autophagy induction. Inhibitors such as bafilomycin A1 (baf-A1) and siRNA against beclin 1 abrogated autophagy, sensitized CML cells against TMQ0153 and enhanced necroptotic cell death. Importantly, TMQ153-induced necrosis led to cell surface exposure of calreticulin (CRT) and ERp57 as well as the release of extracellular ATP and high mobility group box (HMGB1) demonstrating the capacity of this compound to release immunogenic cell death (ICD) markers. We validated the anti-cancer potential of TMQ0153 by in vivo inhibition of K562 microtumor formation in zebrafish. Taken together, our findings provide evidence that cellular stress and redox modulation by TMQ0153 concentration-dependently leads to different cell death modalities including controlled necrosis in CML cell models.

Inhibition of Xanthine Oxidoreductase Enhances the Potential of Tyrosine Kinase Inhibitors against Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is characterized by the expression of the oncogenic kinase BCR-ABL. Although tyrosine kinase inhibitors (TKIs) against BCR-ABL represent the standard therapeutic option for CML, resistances to TKIs can be a serious problem. Thus, the search for novel therapeutic approaches is still needed. CML cells show an increased ROS production, which is required for maintaining the BCR-ABL signaling cascade active. In line with that, reducing ROS levels could be an interesting therapeutic strategy for the clinical management of resistant CML. To analyze the therapeutic potential of xanthine oxidoreductase (XOR) in CML, we tested the effect of XOR inhibitor allopurinol. Here, we show for the first time the therapeutic potential of allopurinol against BCR-ABL-positive CML cells. Allopurinol reduces the proliferation and clonogenic ability of the CML model cell lines K562 and KCL22. More importantly, the combination of allopurinol with imatinib or nilotinib reduced cell proliferation in a synergistic manner. Moreover, the co-treatment arms hampered cell clonogenic capacity and induced cell death more strongly than each single-agent arm. The reduction of intracellular ROS levels and the attenuation of the BCR-ABL signaling cascade may explain these effects. Finally, the self-renewal potential of primary bone marrow cells from CML patients was also severely reduced especially by the combination of allopurinol with TKIs. In summary, here we show that XOR inhibition is an interesting therapeutic option for CML, which can enhance the effectiveness of the TKIs currently used in clinics.

Protective role of hazelnut peptides on oxidative stress injury in human umbilical vein endothelial cells

The crude protein hydrolysates of wild hazel have good immunoregulation and antioxidation effects. However, the components responsible for their antioxidation effect remain unknown. In this study, six antioxidative peptides (EW, DWDPK, ADGF, SGAF, ETTL, and AGGF) were tested for their protective effects on oxidative stress injury in human umbilical vein endothelial cells (HUVECs). The results demonstrated that the six peptides are nontoxic and have a protective effect on oxidative stress injury induced by Ang II. Three peptides (EW, ADGF, and DWDPK) inhibited the morphological changes, downregulated the content of lactate dehydrogenase and malondialdehyde, upregulated the activity of antioxidant enzymes catalase, total superoxide dismutase and glutathione peroxidase, and scavenged reactive oxygen species (ROS) in HUVECs. Quantitative reverse transcriptive polymerase chain reaction and western blot assays indicated that these three peptides regulated NADPH oxidase activity and ROS production by reducing NOX4 and p22phox levels. Overall, they have a significant protective effect against oxidative stress injury and have potential application in developing new functional foods. PRACTICAL APPLICATIONS: Corylus heterophylla Fisch is a good quality wild hazel distributed in Northeast China. Wild hazelnut of the species C. heterophylla Fisch was selected as experimental object and has high nutritive values and have abundant proteins (20%-30%), fats (40%-50%), carbohydrates (13%-24%), dietary fibers (8.2%-9.6%), vitamins, and micronutrients. Our results indicate that hazelnut peptides (EW, ADGF, and DWDPK) can ensure normal growth of cells by protecting important antioxidant enzyme systems, by enhancing antioxidant defense, by directly affecting nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, and by reducing intracellular reactive oxygen species (ROS) production in HUVECs, indicating that the three antioxidative peptides have a protective effect against Ang II-induced oxidative stress injury. Therefore, the antioxidative peptides from C. heterophylla Fisch may be a promising candidate for functional food ingredients and/or pharmaceuticals.

Effects of antioxidants on apoptosis induced by dasatinib and nilotinib in K562 cells

In clinical practice for the treatment of chronic myeloid leukemia, second generation of tyrosine kinase inhibitors such as Nilotinib (NIL) specific and potent inhibitor of the BCR/ABL kinase and Dasatinib (DAS) a inhibitor of BCR/ABL and Src family kinase were developed to clinically overcome imatinib resistance. In this study, we wanted to test the ability of some antioxidants such Resveratrol (RES) or a new recombinant mitochondrial manganese containing superoxide dismutase (rMnSOD) or δ-tocotrienol (δ-TOCO) to interact with DAS and NIL on viability, reactive oxygen species (ROS) production, lipid peroxidation, and apoptosis. To test the possible mechanisms of action of such antioxidants, we utilized N-acetyl-L-cysteine (NAC) a specific inhibitor ROS production or PP1 a specific Src tyrosine kinase inhibitor or BAPTA a specific chelator of intracellular calcium. Our data demonstrated: 1) RES, rMnSOD, δ-TOCO, and NAC, at dose used, significantly reduced the intracellular levels of MDA induced by DAS or NIL; 2) RES, rMnSOD, and δ-TOCO increased the intracellular ROS levels; 3) The increase ROS levels is related to higher levels of oligonucleosomesi induced by DAS and NIL and that NAC significantly reduced this activity. Interestingly, our data showed that apoptotic activity of DAS and NIL have significantly increased the production of oligonucleosomes by triggering excessive ROS generation as well as functionality of SERCA receptors.

Nuclear membrane-localised NOX4D generates pro-survival ROS in FLT3-ITD-expressing AML

Internal tandem duplication of the juxtamembrane domain of FMS-like tyrosine kinase 3 (FLT3-ITD) is the most prevalent genetic aberration present in 20-30% of acute myeloid leukaemia (AML) cases and is associated with a poor prognosis. FLT3-ITD expressing cells express elevated levels of NADPH oxidase 4 (NOX4)-generated pro-survival hydrogen peroxide (H₂O₂) contributing to increased levels of DNA oxidation and double strand breaks. NOX4 is constitutively active and has been found to have various isoforms expressed at multiple locations within a cell. The purpose of this study was to investigate the expression, localisation and regulation of NOX4 28 kDa splice variant, NOX4D. NOX4D has previously been shown to localise to the nucleus and nucleolus in various cell types and is implicated in the generation of reactive oxygen species (ROS) and DNA damage. Here, we demonstrate that FLT3-ITD expressing-AML patient samples as well as -cell lines express the NOX4D isoform resulting in elevated H₂O₂ levels compared to FLT3-WT expressing cells, as quantified by flow cytometry. Cell fractionation indicated that NOX4D is nuclear membrane-localised in FLT3-ITD expressing cells. Treatment of MV4-11 cells with receptor trafficking inhibitors, tunicamycin and brefeldin A, resulted in deglycosylation of NOX4 and NOX4D. Inhibition of the FLT3 receptor revealed that the FLT3-ITD oncogene is responsible for the production of NOX4D-generated H₂O₂ in AML. We found that inhibition of the PI3K/AKT and STAT5 pathways resulted in down-regulation of NOX4D-generated pro-survival ROS. Taken together these findings indicate that nuclear membrane-localised NOX4D-generated pro-survival H₂O₂ may be contributing to genetic instability in FLT3-ITD expressing AML.

The selective tyrosine kinase-inhibitor nilotinib alleviates experimentally induced cisplatin nephrotoxicity and heptotoxicity

This work tested the action of nilotinib, selective inhibitor of tyrosine kinase on cisplatin (CP)-induced damage of kidney and liver in rats. Rats were assigned to 4 groups, control, nilotinib, CP, and CP plus nilotinib. Assessment of kidney and liver function, lipid peroxidation and antioxidant markers, anti-apoptotic protein Bcl2, nuclear factor- kappa B (NF-κB) immunoreactivity, and caspase 3 activity were done. CP-induced damage evidenced by histopathological changes, deterioration of renal and liver function, imbalance in oxidants/antioxidants markers, decreased Bcl2, increased caspase 3 activity, and NF-κB nuclear expression in both organs. Nilotinib treatment with CP restored kidney and liver oxidants/antioxidant levels also increased Bcl2 and decreased NF-κB immunoreactivity were evident with nilotinib treatment. In conclusions these results demonstrated a protective effect of nilotinib in experimentally induced CP kidney and liver damage that could be mediated through combating oxidative stress, reducing inflammation and anti-apoptosis in the two organs.

Alterations in the Reactive Oxygen Species in Peripheral Blood of Chronic Myeloid Leukaemia Patients from Northern India

INTRODUCTION

There is a significant difference in the Reactive Oxygen Species (ROS) levels of Chronic Myeloid Leukaemia (CML) patients before and during treatment with Tyrosine Kinase Inhibitors (TKIs). This is because high ROS levels support oncogenic phenotype of CML by inducing proliferation pathway and accumulation of further genetic mutations. Often the measurement is done on WBC or serum for ascertaining one type of ROS species, but measurement of global ROS in fresh whole blood will give more accurate estimation of ROS.

AIM

To measure global ROS in peripheral blood of CML patients.

MATERIALS AND METHODS

A case control study was undertaken to measure ROS in peripheral blood of CML patients from Northern India. CML patients on TKIs (n=40 on imatinib herein called treated) and untreated (n=17, who were not on any TKIs or alternative medicine, called as treatment naive) and 52 healthy controls were also enrolled. Chemiluminescent assay was carried out using luminol as signal enhancer in 400 µl of blood to measure ROS. The chemiluminescence was measured as Relative Light Units (RLU)/sec/104 WBC. Data was presented in terms of mean±SE or geometric mean (95% Confidence Interval) for continuous variables and percentage for categorical variables. Groups were compared using two sample t-test for continuous variables and chi-square test for categorical variables.

RESULTS

The WBC profile and ROS levels of patients taking TKIs were quite similar and showed no significant difference (p<0.999) compared to healthy controls. In contrast, significant increase was observed in the ROS levels of CML patients not on TKIs (untreated) compared to patients under treatment (p<0.029) and healthy controls (p<0.007). We also observed that the absolute ROS values and WBC counts were higher in untreated patients compared to patients on TKIs and healthy controls, even though mean ROS value was less.

CONCLUSION

To ascertain the alterations in ROS levels of CML patients before and during treatment with TKIs, it is better to measure global ROS in fresh whole blood by chemiluminescent method using luminol. Luminol assay is a quick, easy and inexpensive method to measure global ROS. Patient under treatment with TKIs show significant decrease in ROS levels almost similar to the levels measured in healthy controls yet the mechanisms by which this decrease occurs needs to be elucidated.

Genomic instability is a principle pathologic feature of FLT3 ITD kinase activity in acute myeloid leukemia leading to clonal evolution and disease progression

Acute Myeloid Leukemia with FLT3 ITD mutations are associated with a poor prognosis characterized by a higher relapse rate, shorter relapse free survival, and decreased likelihood of response to therapy at relapse. FLT3 ITD signaling drives cell proliferation and survival. FLT3 ITD AML disease progression is associated with cytogenetic evolution and acquired tyrosine kinase inhibitor (TKI) resistance suggesting a potential role of genomic instability. There is growing evidence demonstrating a relationship between FLT3 signaling and increased DNA damage, specifically through increased reactive oxygen species (ROS) resulting in double-strand breaks (DSB), as well as impaired DNA repair, involving deficiencies in the non-homologous end joining (NHEJ), alternative non-homologous end joining (ALT NHEJ) and homologous recombination (HR) pathways. The role of genomic instability in the pathogenesis of FLT3 ITD AML warrants further examination as it offers potential therapeutic targets.

A NOX2/Egr-1/Fyn pathway delineates new targets for TKI-resistant malignancies

Tyrosine kinase inhibitors (TKI) have improved CML response rates, and some are effective against resistance-promoting point mutations in BCR-ABL1. However, in the absence of point mutations, resistance still occurs. Here, we identify a novel pathway mediating resistance which connects p47phox, the organizer subunit of NADPH oxidase-2 (NOX2), with early growth response-1 (Egr-1) and the Src family kinase Fyn. We found up-regulation of p47phox, Egr-1, and Fyn mRNA and protein using paired isogenic CML cell lines and mined data. Isolation of CD34⁺ cells and tissue microarray staining from blast crisis CML patients confirmed in vivo over-expression of components of this pathway. Knockdown studies revealed that p47phox modulated reactive oxygen species and Egr-1 expression, which, in turn, controlled Fyn expression. Interestingly, Fyn knockdown sensitized TKI-resistant cells to dasatinib, a dual BCR-ABL1/Src inhibitor. Egr-1 knockdown had similar effects, indicating the utility of targeting Fyn expression over activation. Pointedly, p47phox knockdown also restored TKI-sensitivity, indicating that targeting the NOX2 complex can overcome resistance. The NOX2/Egr-1/Fyn pathway was also conserved within TKI-resistant EGFRΔIII-expressing glioblastoma and patient-derived glioblastoma stem cells. Thus, our findings suggest that targeting the NOX2/Egr-1/Fyn pathway may have clinical implications within multiple cancer types; particularly where efficacy of TKI is compromised.

ROS signalling, NADPH oxidases and cancer

ROS (reactive oxygen species) have long been regarded as a series of destructive molecules that have a detrimental effect on cell homoeostasis. In support of this are the myriad antioxidant defence systems nearly all eukaryotic cells have that are designed to keep the levels of ROS in check. However, research data emerging over the last decade have demonstrated that ROS can influence a range of cellular events in a manner similar to that seen for traditional second messenger molecules such as cAMP. Hydrogen peroxide (H2O2) appears to be the main ROS with such signalling properties, and this molecule has been shown to affect a wide range of cellular functions. Its localized synthesis by the Nox (NADPH oxidase) family of enzymes and how these enzymes are regulated is of particular interest to those who work in the field of tumour biology.

NADPH oxidase-generated hydrogen peroxide induces DNA damage in mutant FLT3-expressing leukemia cells

Internal tandem duplication of the FMS-like tyrosine kinase (FLT3-ITD) receptor is present in 20% of acute myeloid leukemia (AML) patients and it has been associated with an aggressive AML phenotype. FLT3-ITD expressing cell lines have been shown to generate increased levels of reactive oxygen species (ROS) and DNA double strand breaks (DSBs). However, the molecular basis of how FLT3-ITD-driven ROS leads to the aggressive form of AML is not clearly understood. Our group has previously reported that inhibition of FLT3-ITD signaling results in post-translational down-regulation of p22(phox), a small membrane-bound subunit of the NADPH oxidase (NOX) complex. Here we demonstrated that 32D cells, a myeloblast-like cell line transfected with FLT3-ITD, have a higher protein level of p22(phox) and p22(phox)-interacting NOX isoforms than 32D cells transfected with the wild type FLT3 receptor (FLT3-WT). The inhibition of NOX proteins, p22(phox), and NOX protein knockdowns caused a reduction in ROS, as measured with a hydrogen peroxide (H2O2)-specific dye, peroxy orange 1 (PO1), and nuclear H2O2, as measured with nuclear peroxy emerald 1 (NucPE1). These reductions in the level of H2O2 following the NOX knockdowns were accompanied by a decrease in the number of DNA DSBs. We showed that 32D cells that express FLT3-ITD have a higher level of both oxidized DNA and DNA DSBs than their wild type counterparts. We also observed that NOX4 and p22(phox) localize to the nuclear membrane in MV4-11 cells expressing FLT3-ITD. Taken together these data indicate that NOX and p22(phox) mediate the ROS production from FLT3-ITD that signal to the nucleus causing genomic instability.

Chaetocin antileukemia activity against chronic myelogenous leukemia cells is potentiated by bone marrow stromal factors and overcomes innate imatinib resistance

Chronic myelogenous leukemia (CML) is maintained by a minor population of leukemic stem cells (LSCs) that exhibit innate resistance to tyrosine kinase inhibitors (TKIs) targeting BCR-ABL. Innate resistance can be induced by secreted bone marrow stromal cytokines and growth factors (BMSFs) that protect CML-LSCs from TKIs, resulting in minimal residual disease. Developing strategies to eradicate innate TKI resistance in LSCs is critical for preventing disease relapse. Cancer cells balance reactive oxygen species (ROS) at higher than normal levels, promoting their proliferation and survival, but also making them susceptible to damage by ROS-generating agents. Bcr-Abl increases cellular ROS levels, which can be reduced with TKI inhibitors, whereas, BMSFs increase ROS levels. We hypothesized that BMSF-mediated increases in ROS would trigger ROS damage in TKI-treated CML-LSCs when exposed to chaetocin, a mycotoxin that imposes oxidative stress by inhibiting thioredoxin reductase-1. Here, we showed that chaetocin suppressed viability and colony formation, and induced apoptosis of the murine hematopoietic cell line TonB210 with and without Bcr-Abl expression, and these effects were potentiated by BMSFs. In contrast, imatinib activities in Bcr-Abl-positive TonB210 cells were inhibited by BMSFs. Further, BMSFs did not inhibit imatinib activities when TonB210 cells expressing Bcr-Abl were cotreated with chaetocin. Chaetocin showed similar activities against LSC-enriched CML cell populations isolated from a murine transplant model of CML blast crisis that were phenotypically negative for lineage markers and positive for Sca-1 and c-Kit (CML-LSK). BMSFs and chaetocin increased ROS in CML-LSK cells and addition of BMSFs and chaetocin resulted in higher levels compared with chaetocin or BMSF treatment alone. Pretreatment of CML-LSKs with the antioxidant N-acetylcysteine blocked chaetocin cytotoxicity, even in the presence of BMSFs, demonstrating the importance ROS for chaetocin activities. Chaetocin effects on self-renewal of CML-LSKs were assessed by transplanting CML-LSKs into secondary recipients following ex vivo exposure to chaetocin, in the presence or absence of BMSFs. Disease latency in mice transplanted with CML-LSKs following chaetocin treatment more than doubled compared with untreated CML-LSKs or BMSFs-treated CML-LSKs. Mice transplanted with CML-LSKs following chaetocin treatment in the presence of BMSFs had significantly extended survival time compared with mice transplanted with CML-LSKs treated with chaetocin alone. Our findings indicate that chaetocin activity against CML-LSKs is significantly enhanced in the presence of BMSFs and suggest that chaetocin may be effective as a codrug to complement TKIs in CML treatment by disrupting the innate resistance of CML-LSKs through an ROS dependent mechanism.

Cell-penetrating fusion peptides OD1 and OD2 interact with Bcr-Abl and influence the growth and apoptosis of K562 cells

The Bcr-Abl oncoprotein is the cause of chronic myelogenous leukemia (CML). Crystal structure analysis suggests that Bcr30-63 is the core of the Bcr-Abl oligomerization interface for aberrant kinase activity; however, the precise role of other residues of Bcr1-72 excluding Bcr30-63 have not been evaluated. In this study, Bcr30-63 was named OD2 and other residues of Bcr1-72 were named OD1. Cytoplasmic transduction peptide (CTP) was used to carry molecules into cytoplasm. CTP-OD1 and CTP-OD2 fusion peptides were expressed from a cold-inducible expression system. Our results demonstrated that both fusion peptides could localize into the cytoplasm, specifically interact with the Bcr-Abl protein and further inhibit growth, induce apoptosis, and decrease the phosphorylation of Bcr-Abl in K562 cell lines. However, the viability of THP-1, a Bcr-Abl negative cell line, was unaffected. These results suggested that CTP-OD1 and CTP-OD2 may be an attractive therapeutic option to inhibit the activation of Bcr-Abl kinase in CML.

Targeting the therapeutic effects of exercise on redox-sensitive mechanisms in the vascular endothelium during tumor progression

The American Cancer Society estimated 1.5 million new cancer cases in the United States in 2012. Although the exact number is not known, it is estimated that brain metastases occur in 20-40% of cancer patients (39). Owing to the complexity of development and the variation in tumor etiology, therapy options have been limited for a number of cancers, whereas progressive treatments have been successful for some malignancies. Combining treatment strategies has shown potential to increase positive outcomes; however, cancer remains a formidable diagnosis with no true cure. Many researchers have focused on alternative forms of cancer prevention or treatment to slow cancer progression. Studies have shown that with moderate, regular exercise signaling pathways associated with increased antioxidant activity and cellular repair are upregulated in vascular tissue; however, the physiological mechanisms are poorly understood. The purpose of this review is to examine the current literature to better understand the impact of exercise on cancer progression and tumor metastasis and discuss potential redox-related signaling in the vasculature that may be involved.