Impact of context-dependent autophagy states on tumor progression.

Macroautophagy is a cellular quality-control process that degrades proteins, protein aggregates and damaged organelles. Autophagy plays a fundamental role in cancer where, in the presence of stressors (for example, nutrient starvation, hypoxia, mechanical pressure), tumor cells activate it to degrade intracellular substrates and provide energy. Cell-autonomous autophagy in tumor cells and cell-nonautonomous autophagy in the tumor microenvironment and in the host converge on mechanisms that modulate metabolic fitness, DNA integrity and immune escape and, consequently, support tumor growth. In this Review, we will discuss insights into the tumor-modulating roles of autophagy in different contexts and reflect on how future studies using physiological culture systems may help to understand the complexity and open new therapeutic avenues.

KRAS protein expression becomes progressively restricted during embryogenesis and in adulthood.

KRAS mutants are common in many cancers and wild-type KRAS is essential in development as its absence causes embryonic lethality. Despite this critical role in development and disease, the normal expression pattern of KRAS protein is still largely unknown at the tissue level due to the lack of valid antibodies. To address this issue, we used the citrine-Kras mouse model in which the Citrine-KRAS (Cit-K) fusion protein functions as a validated surrogate of endogenous KRAS protein that can be detected on tissue sections by immunolabeling with a GFP antibody. In the embryo, we found expression of KRAS protein in a wide range of organs and tissues. This expression tends to decrease near birth, mainly in mesenchymal cells. During transition to the adult stage, the dynamics of KRAS protein expression vary among organs and detection of KRAS becomes restricted to specific cell types. Furthermore, we found that steady state KRAS protein expression is detectable at the cell membrane and in the cytoplasm and that this subcellular partitioning differed among cell types. Our results reveal hitherto unanticipated dynamics in developmental, tissular, cell-specific and subcellular expression of KRAS protein. They provide insight into the reason why specific cell-types are sensitive to KRAS mutations during cancer initiation.

N-Acetylcysteine Reduces the Pro-Oxidant and Inflammatory Responses during Pancreatitis and Pancreas Tumorigenesis.

Pancreatitis, an inflammation of the pancreas, appears to be a main driver of pancreatic cancer when combined with Kras mutations. In this context, the exact redox mechanisms are not clearly elucidated. Herein, we treated mice expressing a KrasG12D mutation in pancreatic acinar cells with cerulein to induce acute pancreatitis. In the presence of KrasG12D, pancreatitis triggered significantly greater redox unbalance and oxidative damages compared to control mice expressing wild-type Kras alleles. Further analyses identified the disruption in glutathione metabolism as the main redox event occurring during pancreatitis. Compared to the wild-type background, KrasG12D-bearing mice showed a greater responsiveness to treatment with a thiol-containing compound, N-acetylcysteine (NAC). Notably, NAC treatment increased the pancreatic glutathione pool, reduced systemic markers related to pancreatic and liver damages, limited the extent of pancreatic edema and fibrosis as well as reduced systemic and pancreatic oxidative damages. The protective effects of NAC were, at least, partly due to a decrease in the production of tumor necrosis factor-α (TNF-α) by acinar cells, which was concomitant with the inhibition of NF-κB(p65) nuclear translocation. Our data provide a rationale to use thiol-containing compounds as an adjuvant therapy to alleviate the severity of inflammation during pancreatitis and pancreatic tumorigenesis.

Genetic Inactivation of Peroxiredoxin-I Impairs the Growth of Human Pancreatic Cancer Cells.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with few therapeutic options. The identification of new promising targets is, therefore, an urgent need. Using available transcriptomic datasets, we first found that Peroxiredoxin-1 gene (PRDX1) expression was significantly increased in human pancreatic tumors, but not in the other gastrointestinal cancers; its high expression correlated with shortened patient survival. We confirmed by immunostaining on mouse pancreata the increased Peroxiredoxin-I protein (PRX-I) expression in pancreatic neoplastic lesions and PDAC. To question the role of PRX-I in pancreatic cancer, we genetically inactivated its expression in multiple human PDAC cell lines, using siRNA and CRISPR/Cas9. In both strategies, PRX-I ablation led to reduced survival of PDAC cells. This was mainly due to an increase in the production of reactive oxygen species (ROS), accumulation of oxidative DNA damage (i.e., 8-oxoguanine), and cell cycle blockade at G2/M. Finally, we found that PRX-I ablation disrupts the autophagic flux in PDAC cells, which is essential for their survival. This proof-of-concept study supports a pro-oncogenic role for PRX-I in PDAC.

Dynamic Regulation of Expression of KRAS and Its Effectors Determines the Ability to Initiate Tumorigenesis in Pancreatic Acinar Cells.

Pancreatic acinar cells are a cell type of origin for pancreatic cancer that become progressively less sensitive to tumorigenesis induced by oncogenic Kras mutations after birth. This sensitivity is increased when Kras mutations are combined with pancreatitis. Molecular mechanisms underlying these observations are still largely unknown. To identify these mechanisms, we generated the first CRISPR-edited mouse models that enable detection of wild-type and mutant KRAS proteins in vivo. Analysis of these mouse models revealed that more than 75% of adult acinar cells are devoid of detectable KRAS protein. In the 25% of acinar cells expressing KRAS protein, transcriptomic analysis highlighted a slight upregulation of the RAS and MAPK pathways. However, at the protein level, only marginal pancreatic expression of essential KRAS effectors, including C-RAF, was observed. The expression of KRAS and its effectors gradually decreased after birth. The low sensitivity of adult acinar cells to Kras mutations resulted from low expression of KRAS and its effectors and the subsequent lack of activation of RAS/MAPK pathways. Pancreatitis triggered expression of KRAS and its effectors as well as subsequent activation of downstream signaling; this induction required the activity of EGFR. Finally, expression of C-RAF in adult pancreas was required for pancreatic tumorigenesis. In conclusion, our study reveals that control of the expression of KRAS and its effectors regulates the sensitivity of acinar cells to transformation by oncogenic Kras mutations. SIGNIFICANCE: This study generates new mouse models to study regulation of KRAS during pancreatic tumorigenesis and highlights a novel mechanism through which pancreatitis sensitizes acinar cells to Kras mutations.

A Novel KRAS Antibody Highlights a Regulation Mechanism of Post-Translational Modifications of KRAS during Tumorigenesis.

KRAS is a powerful oncogene responsible for the development of many cancers. Despite the great progress in understanding its function during the last decade, the study of KRAS expression, subcellular localization, and post-translational modifications remains technically challenging. Accordingly, many facets of KRAS biology are still unknown. Antibodies could be an effective and easy-to-use tool for in vitro and in vivo research on KRAS. Here, we generated a novel rabbit polyclonal antibody that allows immunolabeling of cells and tissues overexpressing KRAS. Cell transfection experiments with expression vectors for the members of the RAS family revealed a preferential specificity of this antibody for KRAS. In addition, KRAS was sensitively detected in a mouse tissue electroporated with an expression vector. Interestingly, our antibody was able to detect endogenous forms of unprenylated (immature) and prenylated (mature) KRAS in mouse organs. We found that KRAS prenylation was increased ex vivo and in vivo in a model of KRASG12D-driven tumorigenesis, which was concomitant with an induction of expression of essential KRAS prenylation enzymes. Therefore, our tool helped us to put the light on new regulations of KRAS activation during cancer initiation. The use of this tool by the RAS community could contribute to discovering novel aspects of KRAS biology.

Exercise training improves radiotherapy efficiency in a murine model of prostate cancer.

Engaging in exercise while undergoing radiotherapy (RT) has been reported to be safe and achievable. The impact of exercise training (ET) on RT efficiency is however largely unknown. Our study aims to investigate the interactions between ET and RT on prostate cancer growth. Athymic mice received a subcutaneous injection of PPC-1 cells and were randomly assigned to either cancer control, cancer ET, cancer RT, or cancer RT combined with ET (CaRT-ET). Mice were sacrificed 24 days post-injection. All three intervention groups had reduced tumor size, the most important decrease being observed in CaRT-ET mice. Apoptotic marker cleaved caspase-3 was not modified by ET, but enhanced with RT. Importantly, this increase was the highest when the two strategies were combined. Furthermore, NK1.1 staining and gene expression of natural killer (NK) cell receptors Klrk1 and Il2rß were not affected by ET alone but were increased with RT, this effect being potentiated when combined with ET. Overall, our study shows that (a) ET enhances RT efficiency by potentiating NK cell infiltration, and (b) while ET alone and ET combined with RT both reduce tumor growth, the mechanisms mediating these effects are different.

Exercise shapes redox signaling in cancer.

In this paper of the special issue dedicated for the Olympics 2020, we put the light on an exciting facet of exercise-oncology, which may still be unknown to some audience. Accumulating convincing evidences show that exercise reduces cancer progression and recurrence mainly in colon and breast cancer patients. Interestingly, the positive effects of exercise on cancer outcomes were mainly observed when patients practiced vigorous exercise of 6 METs or more. At the molecular level, experimental studies highlighted that regular vigorous exercise could reduce tumor growth by driving changes in immune system, metabolism, hormones, systemic inflammation, angiogenesis and redox status. In the present review, we describe the main redox-sensitive mechanisms mediated by exercise. These redox mechanisms are of particular therapeutic interest as they may explain the emerging preclinical findings proving that the association of vigorous exercise with chemotherapy or radiotherapy improves the anti-cancer responses of both interventions. Clinical and preclinical studies converge to support the practice of exercise as an adjuvant therapy that improves cancer outcomes. The understanding of the underpinning molecular mechanisms of exercise in cancer can open new avenues to improve cancer care in patients.

Kras and Lkb1 mutations synergistically induce intraductal papillary mucinous neoplasm derived from pancreatic duct cells.

OBJECTIVE: Pancreatic cancer can arise from precursor lesions called intraductal papillary mucinous neoplasms (IPMN), which are characterised by cysts containing papillae and mucus-producing cells. The high frequency of KRAS mutations in IPMN and histological analyses suggest that oncogenic KRAS drives IPMN development from pancreatic duct cells. However, induction of Kras mutation in ductal cells is not sufficient to generate IPMN, and formal proof of a ductal origin of IPMN is still missing. Here we explore whether combining oncogenic KrasG12D mutation with an additional gene mutation known to occur in human IPMN can induce IPMN from pancreatic duct cells. DESIGN: We created and phenotyped mouse models in which mutations in Kras and in the tumour suppressor gene liver kinase B1 (Lkb1/Stk11) are conditionally induced in pancreatic ducts using Cre-mediated gene recombination. We also tested the effect of ß-catenin inhibition during formation of the lesions. RESULTS: Activating KrasG12D mutation and Lkb1 inactivation synergised to induce IPMN, mainly of gastric type and with malignant potential. The mouse lesions shared several features with human IPMN. Time course analysis suggested that IPMN developed from intraductal papillae and glandular neoplasms, which both derived from the epithelium lining large pancreatic ducts. ß-catenin was required for the development of glandular neoplasms and subsequent development of the mucinous cells in IPMN. Instead, the lack of ß-catenin did not impede formation of intraductal papillae and their progression to papillary lesions in IPMN. CONCLUSION: Our work demonstrates that IPMN can result from synergy between KrasG12D mutation and inactivation of a tumour suppressor gene. The ductal epithelium can give rise to glandular neoplasms and papillary lesions, which probably both contribute to IPMN formation.

DIE-RNA: A Reproducible Strategy for the Digestion of Normal and Injured Pancreas, Isolation of Pancreatic Cells from Genetically Engineered Mouse Models and Extraction of High Quality RNA.

The isolation of ribonucleic acid (RNA) suitable for gene expression studies is challenging in the pancreas, due to its high ribonuclease activity. This is even more complicated during pancreatitis, a condition associated with inflammation and fibrosis. Our aim was to implement a time-effective and reproducible protocol to isolate high quality RNA from specific pancreatic cell subtypes, in normal and inflammatory conditions. We used two genetically engineered mouse models (GEMM), Ela-CreER/YFP and Sox9-CreER/YFP, to isolate acinar and ductal cells, respectively. To induce pancreatitis, mice received a caerulein treatment (125 µg/kg) for 8 and 72 h. We alternatively used EGTA and calcium buffers that contain collagenase P (0.6 mg/mL) to rapidly digest the pancreas into individual cells. Most of the cells from normal and injured pancreas were single-dissociated, exhibited a round morphology and did not incorporate trypan blue dye. Cell suspensions from Ela- and Sox9-CreER/YFP pancreas were then sorted by flow cytometry to isolate the YFP-positive acinar and ductal cells, respectively. Sorted cells kept a round shape and emitted fluorescence detected by the 38 HE green fluorescence filter. RNA was isolated by column-based purification approach. The RNA integrity number (RIN) was high in sorted acinar cell fractions treated with or without caerulein (8.6 ± 0.17 and 8.4 ± 0.09, respectively), compared to the whole pancreas fraction (4.8 ± 1.1). Given the low number of sorted ductal cells, the RIN value was slightly lower compared to acini (7.4 ± 0.4). Quantitative-PCR experiments indicated that sorted acinar and ductal cells express the specific acinar and ductal markers, respectively. Additionally, RNA preparations from caerulein-treated acinar cells were free from significant contamination with immune cell RNA. We thus validated the DIE (Digestion, Isolation, and Extraction)-RNA tool as a reproducible and efficient protocol to isolate pure acinar and ductal cells in vivo and to extract high quality RNA from these cells.

The Practice of Physical Activity in the Setting of Lower-Extremities Sarcomas: A First Step toward Clinical Optimization.

Lower-extremities sarcoma patients, with bone tumor and soft-tissue sarcoma, are a unique population at high risk of physical dysfunction and chronic heart diseases. Thus, providing an adequate physical activity (PA) program constitutes a primary part of the adjuvant treatment, aiming to improve patients' quality of life. The main goal of this paper is to offer clear suggestions for clinicians regarding PA around the time between diagnosis and offered treatments. These preliminary recommendations reflect our interpretation of the clinical and preclinical data published on this topic, after a systematic search on the PubMed database. Accordingly, patients could be advised to (1) start sessions of supportive rehabilitation and low-intensity PA after surgery and (2) increase PA intensities progressively during home stay. The usefulness of PA during the preoperative period remains largely unknown but emerging preclinical data on mice bearing intramuscular sarcoma are most likely discouraging. However, efforts are still needed to in-depth elucidate the impact of PA before surgery completion. PA should be age-, sex-, and treatment-adapted, as young/adolescent, women and patients receiving platinum-based chemotherapy are more susceptible to physical quality deterioration. Concerning PA intensity, the practice of moderate-intensity resistance and endurance exercises (30-60 min/day) are safe after surgery, even when receiving adjuvant chemo/radiotherapy. The general PA recommendations for cancer patients, 150 min/week of combined moderate-intensity endurance/resistance exercises, could be feasible after 18-24 months of rehabilitation. We believe that these suggestions will help clinicians to design a low-risk and useful PA program.

The differential role of reactive oxygen species in early and late stages of cancer.

The large doses of vitamins C and E and ß-carotene used to reduce reactive oxygen species (ROS) production and oxidative damages in cancerous tissue have produced disappointing and contradictory results. This therapeutic conundrum was attributed to the double-faced role of ROS, notably, their ability to induce either proliferation or apoptosis of cancer cells. However, for a ROS-inhibitory approach to be effective, it must target ROS when they induce proliferation rather than apoptosis. On the basis of recent advances in redox biology, this review underlined a differential regulation of prooxidant and antioxidant system, respective to the stage of cancer. At early precancerous and neoplastic stages, antioxidant activity decreases and ROS appear to promote cancer initiation via inducing oxidative damage and base pair substitution mutations in prooncogenes and tumor suppressor genes, such as RAS and TP53, respectively. Whereas in late stages of cancer progression, tumor cells escape apoptosis by producing high levels of intracellular antioxidants, like NADPH and GSH, via the pentose phosphate pathway to buffer the excessive production of ROS and related intratumor oxidative injuries. Therefore, antioxidants should be prohibited in patients with advanced stages of cancer and/or undergoing anticancer therapies. Interestingly, the biochemical and biophysical properties of some polyphenols allow them to selectively recognize tumor cells. This characteristic was exploited to design and deliver nanoparticles coated with low doses of polyphenols and containing chemotherapeutic drugs into tumor-bearing animals. First results are encouraging, which may revolutionize the conventional use of antioxidants in cancer.

Interleukin-6, C/EBP-ß and PPAR-γ expression correlates with intramuscular liposarcoma growth in mice: The impact of voluntary physical activity levels.

IL-6 is an axial cytokine overexpressed in cancer to promote growth and increase resistance to anti-cancer therapies. As the application of IL-6-targeting therapies are still limited, alternative non-aggressive and adjuvant approaches, like physical activity (PA) could be useful to reverse IL-6 effects. To get more insights into liposarcoma (LS) pathophysiology, we investigated potential molecular links between IL-6 and LS growth and we tested the impact of PA on such mechanism in an orthotopic model of intramuscular LS. Initially active nude mice have received an intramuscular injection of either human SW872 cells or vehicle, then were respectively randomized into voluntary-active or inactive mice with open or restricted access to activity-wheels. We found that LS-bearing mice exhibited ∼6 fold increase in circulating IL-6 comparing to controls, with a concomitant decrease in hepatic drug-metabolizing enzymes expression. Circulating IL-6 levels were positively correlated with intra-tumor IL-6 expression (r = 0.85, P < 0.01). Interestingly, intra-tumor IL-6, C/EBP-α/ß and PPAR-γ expression were correlated together and with greater tumor mass and autophagy markers, notably, GABARAPL-1. Intriguingly, we found that maintaining a spontaneous PA after tumor injection did not reduce the levels of IL-6, but even enhanced tumor growth, induced body weight loss and increased the risk of developing lung metastasis. Our findings suggest that (1) IL-6, C/EBP-ß and PPAR-γ exert a potential role in promoting growth of dedifferentiated LS and (2) that PA failed to mechanistically interfere with these factors, but enhanced LS growth via other independent-mechanisms. The preclinical data reported here could be helpful in the sub-molecular classification of LS patients to improve diagnosis and design a low-risk treatment. Circulating IL-6 could serve as an indicator for treatment follow-up and, perhaps, for infra-radiologic LS relapses.

Maintaining a regular physical activity aggravates intramuscular tumor growth in an orthotopic liposarcoma model.

Today, care teams within cancer centers encourage patients to be physically active, after diagnosis, based on data obtained mainly from breast, colon and prostate cancer. Intriguingly, the impact of physical activity (PA) on intramuscular tumors (e.g. sarcomas) has not been specifically addressed and, thus, could be mistakenly confounded with other cancers. In this preclinical study we assessed the impact of PA on intramuscular liposarcoma (LS) evolution. Four-week-old nude male mice were active by voluntary running on wheels, for six weeks. Then, mice were divided into four groups with open or restricted access to wheels, which have received an orthotopic intramuscular injection of either vehicle or human LS, SW872, cells. Active mice presented ~1.5 fold increase in tumor mass, which was mainly due to higher cellular mitosis and proliferation. This bulging intramuscular tumor mass altered muscle function, as evidence by overall muscle strength and maximum running capacity. From a molecular point of view, active mice exhibited poor levels of Phospho-p38Thr180/Tyr182 and p21 content in tumors and also displayed low amounts of circulating insulin comparing to inactive counterparts. Insulin induced Phospho-p38Thr180/Tyr182 and p21 expression in SW872 cells, in vitro. The expression of p21 was regulated in a p38-dependent fashion, since inhibition of p38 activity abolished the up-regulation of p21. Our data suggest that insulin-dependent activation of p38 MAPK-p21 pathway is a possible mechanism responsible for delaying tumor growth in inactive mice. Clinically, patients with lower-extremities LS could be advised to reduce or minimize their levels of PA during the preoperative period.

The Janus-Faced Role of Antioxidants in Cancer Cachexia: New Insights on the Established Concepts.

Chronic inflammation and excessive loss of skeletal muscle usually occur during cancer cachexia, leading to functional impairment and delaying the cure of cancer. The release of cytokines by tumor promotes the formation of reactive oxygen species (ROS), which in turn regulate catabolic pathways involved in muscle atrophy. ROS also exert a dual role within tumor itself, as they can either promote proliferation and vascularization or induce senescence and apoptosis. Accordingly, previous studies that used antioxidants to modulate these ROS-dependent mechanisms, in cancer and cancer cachexia, have obtained contradictory results, hence the need to gather the main findings of these studies and draw global conclusions in order to stimulate more oriented research in this field. Based on the literature reviewed in this paper, it appears that antioxidant supplementation is (1) beneficial in cancer cachectic patients with antioxidant deficiencies, (2) most likely harmful in cancer patients with adequate antioxidant status (i.e., lung, gastrointestinal, head and neck, and esophageal), and (3) not recommended when undergoing radiotherapy. At the moment, measuring the blood levels of antioxidants may help to identify patients with systemic deficiencies. This approach is simple to realize but could not be a gold standard method for cachexia, as it does not necessarily reflect the redox state in other organs, like muscle.

Antioxidant supplementation accelerates cachexia development by promoting tumor growth in C26 tumor-bearing mice.

More than 50% of patients with advanced stages of colon cancer suffer from progressive loss of skeletal muscle, called cachexia, resulting in reduced quality of life and shortened survival. It is becoming evident that reactive oxygen species (ROS) regulate pathways controlling skeletal muscle atrophy. Herein we tested the hypothesis that antioxidant supplementation could prevent skeletal muscle atrophy in a model of cachectic Colon 26 (C26) tumor-bearing mice. Seven-week-old BALB/c mice were subcutaneously inoculated with colon 26 (C26) cancer cells or PBS. Then C26-mice were daily gavaged during 22 days either with PBS (vehicle) or an antioxidant cocktail whose composition is close to that of commercial dietary antioxidant supplements (rich in catechins, quercetin and vitamin C). We found that antioxidants enhanced weight loss and caused premature death of mice. Antioxidants supplementation failed to prevent (i) the increase in plasma TNF-α levels and systemic oxidative damage, (ii) skeletal muscle atrophy and (iii) activation of the ubiquitin-proteasome system (MuRF-1, MAFbx and polyubiquitinated proteins). Accordingly, immunohistological staining for Ki-67 and the expression of cell cycle inhibitors demonstrated that tumor of supplemented mice developed faster with a concomitant decrease in oxidative damage. Previous studies have shown that the use of catechins and quercetin separately can improve the musculoskeletal function in cachectic animals. However, our results indicate that the combination of these antioxidants reduced survival and enhanced cachexia in C26-mice.

Regulation of type I-interferon responses in the human epidermal melanocyte cell line SKMEL infected by the Ross River alphavirus.

Melanocytes are melanin-producing cells and with emerging innate immune functions including the expression of antiviral interferon-type I cytokines. We herein ascertained the susceptibility of the human melanocytes to Ross River alphavirus (RRV) infection and analyzed the subsequent immune responses. We demonstrated for the first time that (1) SKMEL-28 melanocyte cell line was susceptible to RRV infection and displaying major cytopathic activities and (2) RRV interfered with the interferon-type I response by altering nuclear translocation of pSTAT1 and pSTAT2 in infected SKMEL-28. These results suggest that the human melanoma cell line SKMEL-28 is a valuable model to analyze the mechanisms involved in severe skin manifestations and melanocyte's immunity at the portal of entry of major infection by arboviruses.

Antioxidants and muscle atrophy in colon cancer: beneficial or deleterious effects?

Cancer cachexia is a multifactorial syndrome characterized by an ongoing loss of body weight, mainly due to adipose tissue and skeletal muscle wasting. Muscle atrophy leads to a progressive functional impairment and contributes to a negative impact on patient's quality of life. Oxidative Stress (OS) seems to play a major role in muscle atrophy since OS markers are increased in plasma and muscles of cancer patients. Thus, supplementing patients with antioxidant may reduce OS and restore muscle mass and function. In this study, we assess the effects of antioxidant supplementation on muscle atrophy in a model of colon 26 tumor-bearing mice (C26-mice). Five-week old Balb/c mice receive a subcutaneous injection of PBS or C26 cancer cells with or without daily supplementation with Allopurinol or Oxynov (50mg/kg and 163mg/kg respectively). Blood and muscles are removed 20-22 days after injection. C26-mice develop cachexia, with a decrease in total body weight, muscular endurance and muscle fibers diameter. Furthermore, injection of C26 induces ubiquitination of muscles proteins, suggesting the enhancement of muscle proteolysis. Contrary to our expectations, supplementation with antioxidants (Allopurinol or Oxynov) doesn't prevent weight loss and muscle atrophy but induces premature death of mice. C26-mice exhibit systemic oxidative stress markers (i.e. carbonyl proteins and 4-HNE) and show an increase in phosphorylation levels of the redox-dependent kinase, JNK, in the atrophied muscles (i.e. gastrocnemius). Surprisingly, Allopurinol or Oxynov decrease the total antioxidant defenses in plasma but has no effect on C26-induced oxidative damages and JNK phosphorylation. Our results are in agreement with recent reports showing deleterious effects of antioxidants supplementation in lung and prostate cancer. However, such findings require further investigations.