Aplysin sensitizes cancer cells to TRAIL by suppressing P38 MAPK/survivin pathway

Combination of marine bioactive compounds and extracts for the prevention and treatment of chronic diseases

Background

In recent years, marine-based functional foods and combination therapy are receiving greater recognition for their roles in healthy lifestyle applications and are being investigated as viable and effective strategies for disease treatment or prevention.

Aim of the review

This review article presents and discusses the relevant scientific publications that have studied the synergistic and additive effects of natural marine bioactive compounds and extract combinations with anti-obesity, anti-inflammatory, antioxidant, and chemopreventive activities in the last two decades. The paper presents the mechanism of action and health benefits of developed combinations and discusses the limitation of the studies. Furthermore, it recommends alternatives and directions for future studies. Finally, it highlights the factors for developing novel combinations of marine bioactive compounds.

Key scientific concepts of review

Combination of marine bioactive compounds or extracts affords synergistic or additive effects by multiple means, such as multi-target effects, enhancing the bioavailability, boosting the bioactivity, and neutralizing adverse effects of compounds in the mixture. For the development of marine-based combinations, there are key points for consideration and issues to address: knowledge of the mechanism of action of individual compounds and their combinations, optimum ratio and dosing of compounds, and experimental models must all be taken into account. Strategies to increase the number and diversity of marine combinations, and further development of marine-based functional foods, are available. However, only a small number of natural marine bioactive combinations have been assessed, and most research has been focused on fish oil and carotenoid synergy. Therefore, more research and resources should be spent on developing novel marine bioactive combinations as functional foods and nutraceuticals.

MAPK signaling pathway-targeted marine compounds in cancer therapy

PURPOSE

This paper reviews marine compounds that target the mitogen-activated protein kinase (MAPK) signaling pathway and their main sources, chemical structures, major targeted cancers and possible mechanisms to provide comprehensive and basic information for the development of marine compound-based antitumor drugs in clinical cancer therapy research.

METHODS

This paper searched the PubMed database using the keywords "cancer", "marine*" and "MAPK signaling pathway"; this search was supplemented by the literature-tracing method. The marine compounds screened for review in this paper are pure compounds with a chemical structure and have antitumor effects on more than one tumor cell line by targeting the MAPK signaling pathway. The PubChem database was used to search for the PubMed CID and draw the chemical structures of the marine compounds.

RESULTS

A total of 128 studies were searched, and 32 marine compounds with unique structures from extensive sources were collected for this review. These compounds are cytotoxic to cancer cell lines, although their targets are still unclear. This paper describes their anticancer effect mechanisms and the protein expression changes in the MAPK pathway induced by these marine compound treatments. This review is the first to highlight MAPK signaling pathway-targeted marine compounds and their use in cancer therapy.

CONCLUSION

The MAPK signaling pathway is a promising potential target for cancer therapy. Searching for marine compounds that exert anticancer effects by targeting the MAPK signaling pathway and developing them into new marine anticancer drugs will be beneficial for cancer treatment.

Bioactive Compounds from Marine Heterobranchs

The natural products of heterobranch molluscs display a huge variability both in structure and in their bioactivity. Despite the considerable lack of information, it can be observed from the recent literature that this group of animals possesses an astonishing arsenal of molecules from different origins that provide the molluscs with potent chemicals that are ecologically and pharmacologically relevant. In this review, we analyze the bioactivity of more than 450 compounds from ca. 400 species of heterobranch molluscs that are useful for the snails to protect themselves in different ways and/or that may be useful to us because of their pharmacological activities. Their ecological activities include predator avoidance, toxicity, antimicrobials, antifouling, trail-following and alarm pheromones, sunscreens and UV protection, tissue regeneration, and others. The most studied ecological activity is predation avoidance, followed by toxicity. Their pharmacological activities consist of cytotoxicity and antitumoral activity; antibiotic, antiparasitic, antiviral, and anti-inflammatory activity; and activity against neurodegenerative diseases and others. The most studied pharmacological activities are cytotoxicity and anticancer activities, followed by antibiotic activity. Overall, it can be observed that heterobranch molluscs are extremely interesting in regard to the study of marine natural products in terms of both chemical ecology and biotechnology studies, providing many leads for further detailed research in these fields in the near future.

Aplysin Retards Pancreatic Necrosis and Inflammatory Responses in NOD Mice by Stabilizing Intestinal Barriers and Regulating Gut Microbial Composition

Aplysin is a brominated sesquiterpene with an isoprene skeleton and has biological activities. The purpose of this study is to investigate the inhibitory effect of aplysin on spontaneous pancreatic necrosis in nonobese diabetic (NOD) mice and its potential mechanisms. Results showed that NOD mice at 12 weeks of age showed obvious spontaneous pancreatic necrosis, damaged tight junctions of intestinal epithelia, and widened gaps in tight and adherens junctions. Aplysin intervention was able to alleviate spontaneous pancreatic necrosis in NOD mice, accompanied with decreased serum endotoxin levels and downregulated expressions of Toll-like receptor 4 and its related molecules MyD88, TRAF-6, NF-κB p65, TRIF, TRAM, and IRF-3, as well as protein levels of interleukin-1β and interferon-β in pancreatic tissues. In addition, we observed obvious improvements of intestinal mucosal barrier function and changes of gut microbiota in the relative abundance at the phylum level and the genus level in aplysin-treated mice compared with control mice. Together, these data suggested that aplysin could retard spontaneous pancreatic necrosis and inflammatory responses in NOD mice through the stabilization of intestinal barriers and regulation of gut microbial composition.

Bioactive compounds from marine invertebrates as potent anticancer drugs: the possible pharmacophores modulating cell death pathways

Marine invertebrates are extremely diverse, largely productive, untapped oceanic resources with chemically unique bioactive lead compound contributing a wide range of screening for the discovery of anticancer compounds. The lead compounds have unfurled an extensive array of pharmacological properties owing to the presence of polyphenols, alkaloids, terpenoids and other secondary metabolites. The antioxidant, immunomodulatory and anti-tumor activities exhibited, are possibly regulated by the apoptosis induction, scavenging of ROS and modulation of cellular signaling pathways to defy the cellular deafness during carcinogenesis. Despite the enriched bioactive compounds, the marine invertebrates are largely unexplored as identification, screening, pre-clinical and clinical assessment of lead compounds and their synthetic analogs remain a major task to be solved. In the current review, we focus on the principle strategy and underlying mechanisms deployed by the bioactive anticancer compounds derived from marine invertebrates to combat cancer with special insight into the cell death mechanism.

Antimycobacterial Activity of Laurinterol and Aplysin from Laurencia johnstonii

Marine environments represent a great opportunity for the discovery of compounds with a wide spectrum of bioactive properties. Due to their large variety and functions derived from natural selection, marine natural products may allow the identification of novel drugs based not only on newly discovered bioactive metabolites but also on already known compounds not yet thoroughly investigated. Since drug resistance has caused an increase in infections by Mycobacterium tuberculosis and nontuberculous mycobacteria, the re-evaluation of known bioactive metabolites has been suggested as a good approach to addressing this problem. In this sense, this study presents an evaluation of the in vitro effect of laurinterol and aplysin, two brominated sesquiterpenes isolated from Laurencia johnstonii, against nine M. tuberculosis strains and six nontuberculous mycobacteria (NTM). Laurinterol exhibited good antimycobacterial activity, especially against nontuberculous mycobacteria, being remarkable its effect against Mycobacterium abscessus, with minimum inhibitory concentration (MIC) values lower than those of the reference drug imipenem. This study provides further evidence for the antimycobacterial activity of some sesquiterpenes from L. johnstonii, which can be considered interesting lead compounds for the discovery of novel molecules to treat NTM infections.

Antitumoral Effect of Laurinterol on 3D Culture of Breast Cancer Explants

Macroalgae represent an important source of bioactive compounds with a wide range of biotechnological applications. Overall, the discovery of effective cytotoxic compounds with pharmaceutical potential is a significant challenge, mostly because they are scarce in nature or their total synthesis is not efficient, while the bioprospecting models currently used do not predict clinical responses. Given this context, we used three-dimensional (3D) cultures of human breast cancer explants to evaluate the antitumoral effect of laurinterol, the major compound of an ethanolic extract of Laurencia johnstonii. To this end, we evaluated the metabolic and histopathological effects of the crude extract of L. johnstonii and laurinterol on Vero and MCF-7 cells, in addition to breast cancer explants. We observed a dose-dependent inhibition of the metabolic activity, as well as morphologic and nuclear changes characteristic of apoptosis. On the other hand, a reduced metabolic viability and marked necrosis areas were observed in breast cancer explants incubated with the crude extract, while explants treated with laurinterol exhibited a heterogeneous response which was associated with the individual response of each human tumor sample. This study supports the cytotoxic and antitumoral effects of laurinterol in in vitro cell cultures and in ex vivo organotypic cultures of human breast cancer explants.

Computational Outlook of Marine Compounds as Anti-Cancer Representatives Targeting BCL-2 and Survivin

INTRODUCTION

The regulation of apoptosis via compounds originated from marine organisms signifies a new wave in the field of drug discovery. Marine organisms produce potent compounds as they hold the phenomenal diversity in chemical structures. The main focus of drug development is anticancer therapy.

METHODS

Expertise on manifold activities of compounds helps in the discovery of their derivatives for preclinical and clinical experiment that promotes improved activity of compounds for cancer patients.

RESULTS

These marine derived compounds stimulate apoptosis in cancer cells by targeting Bcl-2 and Survivin, highlighting the fact that instantaneous targeting of these proteins by novel derivatives results in efficacious and selective killing of cancer cells.

CONCLUSION

Our study reports the identification of Aplysin and Haterumaimide J as Bcl-2 inhibitors and Cortistatin A as an inhibitor of survivin protein, from a sequential virtual screening approach.

Regulated Cell Death Signaling Pathways and Marine Natural Products That Target Them

Our understanding of cell death used to consist in necrosis, an unregulated form, and apoptosis, regulated cell death. That understanding expanded to acknowledge that apoptosis happens through the intrinsic or extrinsic pathways. Actually, many other regulated cell death processes exist, including necroptosis, a regulated form of necrosis, and autophagy-dependent cell death. We also understand that apoptosis occurs beyond the intrinsic and extrinsic pathways with caspase independent forms of apoptosis existing. Our knowledge of the signaling continues to grow, and with that, so does our ability to target different parts of the pathways with small molecules. Marine natural products co-evolve with their targets, and these unique molecules have complex structures with exquisite biological activities and specificities. This article offers a review of our current understanding of the signaling pathways regulating cell death, and highlights marine natural products that can affect these signaling pathways.

Decoding the antineoplastic efficacy of Aplysin targeting Bcl-2: A de novo perspective

The B-cell lymphoma-2 (Bcl-2) family proteins have been attributed to be the key regulators in programmed cell death and apoptosis with a prominent role in human cancer. Understanding the fundamental principles of cell survival and death have been the main cornerstone in cancer drug discovery for identification of novel anticancer agents. In this context the Bcl-2 family of anti-and pro-apoptotic proteins provide an excellent opportunity for development of anticancer agents, as blocking the Bcl-2 or Bcl-XL functionally promotes apoptosis in tumor cells and also sensitize them to chemo- and radiotherapies. The present study reports the identification of novel Aplysin analogs as BCL-2 inhibitors from a sequential virtual screening approach using drug-like, ADMET, docking, pharmacophore filters and molecular dynamics simulation. We identified promising Aplysin analogs that have a potential to be Bcl-2 inhibitors just like the standard drug Obatoclax. One of the compound analog 11 was identified to be a promising inhibitor of Bcl-2 in the docking, pharmacophore and simulation based models.The molecular modeling information provided here can be vital in designing of the novel Bcl-2 inhibitors.

The regulation of combined treatment-induced cell death with recombinant TRAIL and bortezomib through TRAIL signaling in TRAIL-resistant cells

Background

Multiple trials have attempted to demonstrate the effective induction of cell death in TRAIL-resistant cancer cells, including using a combined treatment of recombinant TRAIL and various proteasome inhibitors. These studies have yielded limited success, as the mechanism of cell death is currently unidentified. Understanding this mechanism’s driving forces may facilitate the induction of cell death in TRAIL-resistant cancer cells.

Methods

Three kinds of recombinant soluble TRAIL proteins were treated into TRAIL-resistant cells and TRAIL-susceptible cells, with or without bortezomib, to compare their respective abilities to induce cell death. Recombinant TRAIL was treated with bortezomib to investigate whether this combination treatment could induce tumor regression in a mouse syngeneic tumor model. To understand the mechanism of combined treatment-induced cell death, cells were analyzed by flow cytometry and the effects of various cell death inhibitors on cell death rates were examined.

Results

ILz:rhTRAIL, a recombinant human TRAIL containing isoleucine zipper hexamerization domain, showed the highest cell death inducing ability both in single treatment and in combination treatment with bortezomib. In both TRAIL-resistant and TRAIL-susceptible cells treated with the combination treatment, an increase in cell death rates was dependent upon both the dose of TRAIL and its intrinsic properties. When a syngeneic mouse tumor model was treated with the combination of ILz:rhTRAIL and bortezomib, significant tumor regression was seen as a result of the effective induction of cancer cell death. The combination treatment-induced cell death was both inhibited by TRAIL blocking antibody and caspase-dependent. However, it was not inhibited by various ER stress inhibitors and autophagy inhibitors.

Conclusions

The combination treatment with ILz:rhTRAIL and bortezomib was able to induce cell death in both TRAIL-susceptible and TRAIL-resistant cancer cells through the intracellular TRAIL signaling pathway. The efficiency of cell death was dependent on the properties of TRAIL under the environment provided by bortezomib. The combination treatment-induced cell death was not regulated by bortezomib-induced ER stress response or by autophagy.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4352-3) contains supplementary material, which is available to authorized users.

Molecular docking analysis of aplysin analogs targeting survivin protein

Survivin (IAP proteins) remains an important target for anticancer drug development as it is reported to be over-expressed in tumor cells to enhance resistance to apoptotic stimuli. The study focuses on virtual screening of marine compounds inhibiting survivin, a multifunctional protein, using a computational approach. Structures of compounds were prepared using ChemDraw Ultra 10. Software and converted into its 3D PDB structure and its energy was minimized using Discovery Studio client 2.5. The target protein, survivin was retrieved from RCSB PDB. Lipinski's rule and ADMET toxicity profiling was carried out on marine compounds and the filtered compounds were further promoted for molecular docking analysis and interaction studies using AutoDock Tools 4.0. Molecular docking results revealed that analog (AP 4) of Aplysin, showed very promising inhibitory potential against survivin with a binding energy of -8.75 kcal/mol and Ki 388.28 nM as compared to its known inhibitor, Celecoxib having binding energy of -6.65 kcal/mol and Ki 13.43 μM. AP 4. The analog depicted similarity in pattern when compared to standard. The result proposes AP 4, is an effective molecule exhibiting prominent potential to inhibit survivin and thus promoting apoptosis in tumor cells.

Breast cancer suppression by aplysin is associated with inhibition of PI3K/AKT/FOXO3a pathway

Aplysin, a bromosesquiterpene isolated from Aplysia kurodai, was explored as a potential anti-breast cancer agent by us. However, the mechanisms underlying the anticarcinogenic effect of aplysin remain unclear. Here, aplysin was found to remarkably suppress tumor growth in vivo, inhibit cell proliferation and promote apoptosis in vitro. Additionally, we demonstrated that aplysin attained these effects in part by down-regulating PI3K/AKT/FOXO3a signaling pathway. Aplysin treatment inhibited the phosphorylation levels of AKT (Ser-473) and AKT-dependent phosphorylation of FOXO3a (Ser-253) in breast cancer cell lines and breast cancer tissues. The expression levels of FOXO3a-targeted genes were also destabilized by aplysin, cyclin D1 and Bcl-XL were declined; however, p21^CIP1, p27^KIP1, Bim, TRAIL and FasL were increased both in vivo and in vitro. Furthermore, activation of the PI3K/AKT signaling pathway by an activator and silencing of FOXO3a by shRNA protected the cells from aplysin mediated growth suppression and apoptosis. In summary, our findings revealed that aplysin could suppress breast cancer progression by inhibiting PI3K/AKT/FOXO3a pathway, thereby suggesting a potential role of aplysin as a chemoprevention drug for patients with breast cancer.

Marine Mollusk-Derived Agents with Antiproliferative Activity as Promising Anticancer Agents to Overcome Chemotherapy Resistance

The chemical investigation of marine mollusks has led to the isolation of a wide variety of bioactive metabolites, which evolved in marine organisms as favorable adaptations to survive in different environments. Most of them are derived from food sources, but they can be also biosynthesized de novo by the mollusks themselves, or produced by symbionts. Consequently, the isolated compounds cannot be strictly considered as "chemotaxonomic markers" for the different molluscan species. However, the chemical investigation of this phylum has provided many compounds of interest as potential anticancer drugs that assume particular importance in the light of the growing literature on cancer biology and chemotherapy. The current review highlights the diversity of chemical structures, mechanisms of action, and, most importantly, the potential of mollusk-derived metabolites as anticancer agents, including those biosynthesized by mollusks and those of dietary origin. After the discussion of dolastatins and kahalalides, compounds previously studied in clinical trials, the review covers potentially promising anticancer agents, which are grouped based on their structural type and include terpenes, steroids, peptides, polyketides and nitrogen-containing compounds. The "promise" of a mollusk-derived natural product as an anticancer agent is evaluated on the basis of its ability to target biological characteristics of cancer cells responsible for poor treatment outcomes. These characteristics include high antiproliferative potency against cancer cells in vitro, preferential inhibition of the proliferation of cancer cells over normal ones, mechanism of action via nonapoptotic signaling pathways, circumvention of multidrug resistance phenotype, and high activity in vivo, among others. The review also includes sections on the targeted delivery of mollusk-derived anticancer agents and solutions to their procurement in quantity.

Protective effect of aplysin on liver tissue and the gut microbiota in alcohol-fed rats

Background

This study investigated the protective effect of aplysin on the liver and its influence on inflammation and the gut microbiota in rats with ethanol-induced liver injury.

Methods

Male Sprague-Dawley rats were randomly assigned to an alcohol-containing liquid diet, control liquid diet or treatment with aplysin for 8 weeks. Hepatic and intestinal histopathological analysis was performed, and cytokine levels and the intestinal mucosal barrier were assessed. Enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) and 16S rDNA high-throughput sequencing were performed to provide an overview of the gut microbiota composition.

Results

Chronic alcohol exposure caused liver damage in rats. Serum aspartate aminotransferase (AST), aminotransferase (ALT), alkaline phosphatase (ALP) and triglyceride (TG) activities in liver tissue were higher than in the control group. Alcohol administration elevated the levels of serum transforming growth factor-β (TGF-β) and tumor necrosis factor-α (TNF-α) and reduced interleukin-10 (IL-10) levels compared with those of control rats. In addition, the levels of plasma endotoxin, diamine oxidase (DAO), and fatty acid-binding protein 2 (FABP2) in the alcohol group were higher than in the control group. The results of ERIC-PCR indicated that aplysin treatment shifted the overall structure of the ethanol-disrupted gut microbiota toward that of the control group. One hundred twenty to 190 genera of bacteria were detected by high throughput sequencing. Alcohol-induced changes in the gut microbial composition were detected at the genus level. These alcohol-induced effects could be reversed with aplysin treatment.

Conclusions

These results suggest that aplysin exerts a protective effect on ethanol-induced hepatic injury in rats by normalizing fecal microbiota composition and repairing intestinal barrier function.

The Laurencia Paradox: An Endless Source of Chemodiversity

Nature, the most prolific source of biological and chemical diversity, has provided mankind with treatments for health problems since ancient times and continues to be the most promising reservoir of bioactive chemicals for the development of modern drugs. In addition to the terrestrial organisms that still remain a promising source of new bioactive metabolites, the marine environment, covering approximately 70% of the Earth's surface and containing a largely unexplored biodiversity, offers an enormous resource for the discovery of novel compounds. According to the MarinLit database, more than 27,000 metabolites from marine macro- and microorganisms have been isolated to date providing material and key structures for the development of new products in the pharmaceutical, food, cosmeceutical, chemical, and agrochemical sectors. Algae, which thrive in the euphotic zone, were among the first marine organisms that were investigated as sources of food, nutritional supplements, soil fertilizers, and bioactive metabolites.Red algae of the genus Laurencia are accepted unanimously as one of the richest sources of new secondary metabolites. Their cosmopolitan distribution, along with the chemical variation influenced to a significant degree by environmental and genetic factors, have resulted in an endless parade of metabolites, often featuring multiple halogenation sites.The present contribution, covering the literature until August 2015, offers a comprehensive view of the chemical wealth and the taxonomic problems currently impeding chemical and biological investigations of the genus Laurencia. Since mollusks feeding on Laurencia are, in many cases, bioaccumulating, and utilize algal metabolites as chemical weaponry against natural enemies, metabolites of postulated dietary origin of sea hares that feed on Laurencia species are also included in the present review. Altogether, 1047 secondary metabolites, often featuring new carbocyclic skeletons, have been included.The chapter addresses: (1) the "Laurencia complex", the botanical description and the growth and population dynamics of the genus, as well as its chemical diversity and ecological relations; (2) the secondary metabolites, which are organized according to their chemical structures and are classified into sesquiterpenes, diterpenes, triterpenes, acetogenins, indoles, aromatic compounds, steroids, and miscellaneous compounds, as well as their sources of isolation which are depicted in tabulated form, and (3) the biological activity organized according to the biological target and the ecological functions of Laurencia metabolites.

Marine Drugs Regulating Apoptosis Induced by Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)

Marine biomass diversity is a tremendous source of potential anticancer compounds. Several natural marine products have been described to restore tumor cell sensitivity to TNF-related apoptosis inducing ligand (TRAIL)-induced cell death. TRAIL is involved during tumor immune surveillance. Its selectivity for cancer cells has attracted much attention in oncology. This review aims at discussing the main mechanisms by which TRAIL signaling is regulated and presenting how marine bioactive compounds have been found, so far, to overcome TRAIL resistance in tumor cells.

Tanshinone IIA enhances the effects of TRAIL by downregulating survivin in human ovarian carcinoma cells

BACKGROUND

Tanshinone IIA (TIIA), a diterpene quinone from the medicinal plant Salvia miltiorrhiza Bunge (Lamiaceae) was shown to possess apoptotic and TRAIL-sensitizing effects. Still, the molecular mechanisms whereby TIIA induces apoptosis remain largely unknown.

PURPOSE

The role of survivin, an inhibitor of apoptosis protein, in TIIA-induced apoptosis has never been addressed before and hence was the primary goal of this study.

METHODS

In this study, we explored the anticancer effect of TIIA in TOV-21G, SKOV3, and OVCAR3 ovarian carcinoma cells. Cytotoxicity was determined by MTS assay. Real-time RT-PCR and Western blotting were used to assess the mRNA and protein expression of related signaling proteins.

RESULTS

Our results illustrated that TIIA's cytotoxic effect was caused by apoptosis with the involvement of caspases activity. Moreover, TIIA downregulated survivin in a concentration-dependent manner without affecting the expression of Bcl-2, Bcl-xL, and Bax. TIIA-induced survivin downregulation is regulated by both transcriptional processes and proteasomal degradation. Using TOV-21G cells as our cellular model, we demonstrated that TIIA-induced survivin downregulation requires p38 MAPK activation. Importantly, genetic overexpression of survivin rendered cells more resistant to TIIA, indicating an essential role of survivin downregulation in TIIA-induced apoptosis. This TRAIL sensitization effect of TIIA is ascribed to survivin downregulation because the effect was abrogated in cells that overexpressed survivin.

CONCLUSION

Our findings provide new insights into the action modes of TIIA-mediated anticancer effects and further implicate a rational design for cancer therapeutic regimens by combining TIIA-sensitized TRAIL via downregulating survivin to elicit ovarian cancer cell death.

p38 MAPK-dependent Nrf2 induction enhances the resistance of glioma cells against TMZ

Temozolomide (TMZ) is an effective agent for clinical glioma treatment, but the innate and acquired resistance of glioma always limits its application. Although some advances have been achieved to elucidate the molecular mechanism underlying TMZ resistance, the role of Nrf2 (a principle regulator of cellular defense against drugs and oxidative stress) has not been well established in the acquisition of this phenotype. Our data showed that TMZ treatment induces the activation of Nrf2 and p38 MAPK signaling in glioma cells, while p38 inhibition abolished the effect of TMZ on Nrf2. Further study revealed that Nrf2 silencing was able to enhance the response of glioma cells to TMZ. Additionally, Nrf2 overexpression overrides the effect of p38 MAPK activation on Temozolomide resistance. In conclusions, we identified a p38 MAPK/Nrf2 signaling as a key molecular network contributing to TMZ resistance of glioma, and provided evidence that suppressing this signaling may be a promising strategy to improve TMZ's therapeutic efficiency.