Low-Dose DMC Significantly Enhances the Effect of TMZ on Glioma Cells by Targeting Multiple Signaling Pathways Both In Vivo and In Vitro

The Small Molecules of Plant Origin with Anti-Glioma Activity

Gliomas, originating from glial cells, are prevalent and aggressive brain tumors with high recurrence rates and poor prognosis. Despite advancements in surgical, radiation, and chemotherapeutic treatments, the survival rates remain low. Current standard therapies, such as Temozolomide, have limitations due to cytotoxicity, restricted effectiveness, and severe side effects. So, the development of safer anti-glioma agents is the need of the hour. Bioactive compounds of plant origin, either natural or synthetic, have potential implications due to them actively attacking different targets with a wide range of bioactivities, including anti-glioma activities. In this review, for the first time, there is an overall overview of 51 small molecules of plant origin and seven of their synthetic derivatives, represented as anti-glioma agents in the past decades. The goal of the present review is to provide a summary to comprehend the anti-glioma effects of these compounds in addition to providing a reference for preclinical research into novel anti-glioma agents for future clinical application.

Potential of Natural Products in the Treatment of Glioma: Focus on Molecular Mechanisms

Despite the waning of traditional treatments for glioma due to possible long-term issues, the healing possibilities of substances derived from nature have been reignited in the scientific community. These natural substances, commonly found in fruits and vegetables, are considered potential alternatives to pharmaceuticals, as they have been shown in prior research to impact pathways surrounding cancer progression, metastases, invasion, and resistance. This review will explore the supposed molecular mechanisms of different natural components, such as berberine, curcumin, coffee, resveratrol, epigallocatechin-3-gallate, quercetin, tanshinone, silymarin, coumarin, and lycopene, concerning glioma treatment. While the benefits of a balanced diet containing these compounds are widely recognized, there is considerable scope for investigating the efficacy of these natural products in treating glioma.

Ultrastructural and immunohistochemical insights on the anti-glioma effects of a dual-drug cocktail in an in vivo experimental model

Glioma coined as 'butterfly tumor' exhibits intense heterogeneity at the molecular and cellular levels. Although, Temozolomide exerted a long-ranging and prevailing therapeutic effect against glioma, albeit it has provided modest survival outcome. Fucoidan, (marine brown algal derivative) has demonstrated potent anti-tumor effects including glioma. Nevertheless, there is paucity of studies conducted on Fucoidan to enhance the anti-glioma efficacy of Temozolomide. The present study aimed to explore the plausible synergistic anti-glioma efficacy of Fucoidan in combination with Temozolomide in an in vivo experimental model. The dual-drug combination significantly inhibited tumor growth in in vivo and prolonged the survival rate when compared with the other treatment and tumor-control groups, via down-regulation of inflammatory cascade- IL-6/T LR4 and JAK/STAT3 as per the immunohistochemistry findings. Furthermore, the ultrastructural analysis indicated that the combinatorial treatment had restored the normal neuronal architecture of glioma-induced rats. Overall, the dual-drug cocktail might enhance the therapeutic outcome in glioma patients.

Natural Compounds as Promising Adjuvant Agents in The Treatment of Gliomas

In humans, glioblastoma is the most prevalent primary malignant brain tumor. Usually, glioblastoma has specific characteristics, such as aggressive cell proliferation and rapid invasion of surrounding brain tissue, leading to a poor patient prognosis. The current therapy-which provides a multidisciplinary approach with surgery followed by radiotherapy and chemotherapy with temozolomide-is not very efficient since it faces clinical challenges such as tumor heterogeneity, invasiveness, and chemoresistance. In this respect, natural substances in the diet, integral components in the lifestyle medicine approach, can be seen as potential chemotherapeutics. There are several epidemiological studies that have shown the chemopreventive role of natural dietary compounds in cancer progression and development. These heterogeneous compounds can produce anti-glioblastoma effects through upregulation of apoptosis and autophagy; allowing the promotion of cell cycle arrest; interfering with tumor metabolism; and permitting proliferation, neuroinflammation, chemoresistance, angiogenesis, and metastasis inhibition. Although these beneficial effects are promising, the efficacy of natural compounds in glioblastoma is limited due to their bioavailability and blood-brain barrier permeability. Thereby, further clinical trials are necessary to confirm the in vitro and in vivo anticancer properties of natural compounds. In this article, we overview the role of several natural substances in the treatment of glioblastoma by considering the challenges to be overcome and future prospects.

Medicinal Plants for Glioblastoma Treatment

Glioblastoma, an aggressive brain cancer, demonstrates the least life expectancy among all brain cancers. Because of the regulation of diverse signaling pathways in cancers, the chemotherapeutic approaches used to suppress their multiplication and spreading are restricted. Sensitivity towards chemotherapeutic agents has developed because of the pathological and drug-evading abilities of these diverse mechanisms. As a result, the identification and exploration of strategies or treatments, which can overcome such refractory obstacles to improve glioblastoma response to treatment as well as recovery, is essential. Medicinal herbs contain a wide variety of bioactive compounds, which could trigger aggressive brain cancers, regulate their anti-cancer mechanisms and immune responses to assist in cancer elimination, and cause cell death. Numerous tumor-causing proteins, which facilitate invasion as well as metastasis of cancer, tolerance of chemotherapies, and angiogenesis, are also inhibited by these phytochemicals. Such herbs remain valuable for glioblastoma prevention and its incidence by effectively being used as anti-glioma therapies. This review thus presents the latest findings on medicinal plants using which the extracts or bioactive components are being used against glioblastoma, their mechanism of functioning, pharmacological description as well as recent clinical studies conducted on them.

Demethoxycurcumin induces apoptosis in HER2 overexpressing bladder cancer cells through degradation of HER2 and inhibiting the PI3K/Akt pathway

Bladder cancer is the most common malignancy of the urinary tract and arising from the epithelial lining of the urinary bladder. Resistance to cytotoxic therapies is associated with overexpression of oncogenic proteins; including HER2, and Akt in chemotherapy resistance of bladder cancer. Various studies demonstrated that curcuminoids, the most important active phenolic compounds of turmeric (Curcuma longa), have anti-tumor activities in a wide range of human malignant cell lines. The aim of this study is to evaluate whether curcuminoids (curcumin, demethoxycurcumin (DMC), and bisdemethoxycurcumin) could repress the expression of HER2 in HER2-overexpressing bladder cancer cells. Among the test compounds, DMC significantly suppressed the expression of HER2, and preferentially inhibited cell proliferation and induced apoptosis in HER2-overexpressing bladder cancer cells. DMC decreases HER2 level through inhibiting the interaction of HER2 and Hsp90. Our study also indicated that DMC showed additive activity in combination with chemotherapeutic agents, including paclitaxel and cisplatin. These findings show that DMC should be developed further as a new antitumor drug candidate for treatment of HER2-overexpressing bladder cancer.

Demethoxycurcumin analogue DMC-BH exhibits potent anticancer effects on orthotopic glioblastomas

Demethoxycurcumin (DMC) has anti-glioma effects in vitro and in subcutaneous xenotransplanted tumors. Our previous study confirmed that the molecule also has mild anti-glioma effects on orthotopic glioblastomas in vivo. In this study, we found that DMC-BH, a DMC analogue, exhibited more potent in vitro and in vivo activities than did DMC. DMC-BH was cytotoxic against various glioma cells including SHG-44, C6, U251, U87, A172 and primary glioma cells. DMC-BH activity was characterized by low acute toxicity and an appropriate pharmacokinetic profile. We evaluated the anti-tumor effects of DMC-BH in an ectopic xenograft model, an orthotopic glioblastoma xenograft model and a patient-derived tumor xenograft (PDTX) model. DMC-BH exhibited potent anti-tumor activity in both the ectopic xenograft and PDTX models. Indeed, bioluminescence measurements showed that DMC-BH exerted a significantly greater anti-tumor effect on orthotopic glioma growth than DMC. Immunohistochemical analysis revealed that DMC-BH inhibited expression of Ki67 and increased the incidence of TUNEL-positive cells. Western blotting showed that DMC-BH significantly decreased p-Akt and p-mTOR expression in orthotopic glioma tissues. These results suggest that the DMC analogue DMC-BH has potent anti-tumor properties that warrant further study.

The Multi-Faceted Effect of Curcumin in Glioblastoma from Rescuing Cell Clearance to Autophagy-Independent Effects

The present review focuses on the multi-faceted effects of curcumin on the neurobiology glioblastoma multiforme (GBM), with a special emphasis on autophagy (ATG)-dependent molecular pathways activated by such a natural polyphenol. This is consistent with the effects of curcumin in a variety of experimental models of neurodegeneration, where the molecular events partially overlap with GBM. In fact, curcumin broadly affects various signaling pathways, which are similarly affected in cell degeneration and cell differentiation. The antitumoral effects of curcumin include growth inhibition, cell cycle arrest, anti-migration and anti-invasion, as well as chemo- and radio-sensitizing activity. Remarkably, most of these effects rely on mammalian target of rapamycin (mTOR)-dependent ATG induction. In addition, curcumin targets undifferentiated and highly tumorigenic GBM cancer stem cells (GSCs). When rescuing ATG with curcumin, the tumorigenic feature of GSCs is suppressed, thus counteracting GBM establishment and growth. It is noteworthy that targeting GSCs may also help overcome therapeutic resistance and reduce tumor relapse, which may lead to a significant improvement of GBM prognosis. The present review focuses on the multi-faceted effects of curcumin on GBM neurobiology, which represents an extension to its neuroprotective efficacy.

Demethoxycurcumin Inhibits In Vivo Growth of Xenograft Tumors of Human Cervical Cancer Cells

BACKGROUND/AIM

Demethoxycurcumin (DMC), a derivate of curcumin from natural plants, exerts antitumor effects on various human cancer cells in vitro and in vivo. Nevertheless, no reports have disclosed whether DMC can affect the growth of human cervical cancer cells in vivo. Therefore we investigated the antitumor effects of DMC on a HeLa cell xenograft model in nude mice in this study.

MATERIALS AND METHODS

Twenty-four nude mice were subcutaneously injected with HeLa cells. All mice were randomly divided into control, low-dose DMC (30 mg/kg), and high-dose DMC (50 mg/kg) groups and individual mice were treated intraperitoneally accordingly every 2 days.

RESULTS

DMC significantly reduced tumor weights and volumes of HeLa cell xenografts in mice, indicating the suppression of growth of xenograft tumors.

CONCLUSION

These effects and findings might provide evidence for investigating the potential use of DMC as an anti-cervical cancer drug in the future.

Therapeutic potentials of curcumin in the treatment of glioblstoma

Glioblastoma multiforme (GBM), a greatly aggressive malignancy of the brain, is correlated with a poor prognosis and low rate of survival. Up to now, chemotherapy and radiation therapy after surgical approaches have been the treatments increasing the survival rates. The low efficacy of mentioned therapies as well as their side-effects has forced researchers to explore an appropriate alternative or complementary treatment for glioblastoma. In experimental models, it has been shown that curcumin has therapeutic potentials to fight against GBM. Given that curcumin has pharmacological effects against cancer stem cells, as major causes of resistance to therapy in glioblastoma cells. Moreover, it has been showed that curcumin exerts its therapeutic effects on GBM cells via affecting on apoptosis, oxidant system, and inflammatory pathways. Curcumin would possess a synergistic impact with chemotherapeutic agents. Herein, we summarized the current findings on curcumin as therapeutic agent in the treatment of GBM.

Combined treatment of AT101 and demethoxycurcumin yields an enhanced anti-proliferative effect in human primary glioblastoma cells

PURPOSE

Glioblastoma multiforme (GBM) is a poorly curable disease due to its profound chemoresistance. Despite recent advances in surgery, radiotherapy and chemotherapy, the efficient treatment of GBMs is still a clinical challenge. Beside others, AT101, the R-(-) enantiomer of gossypol, and demethoxycurcumin (DMC), a curcumin-related demethoxy compound derived from Curcuma longa, were considered as possible alternative drugs for GBM therapy.

METHODS

Using different human primary GBM cell cultures in a long-term stimulation in vitro model, the cytotoxic and anti-proliferative effects of single and combined treatment with 5 µM AT101 and 5 µM or 10 µM DMC were investigated. Furthermore, western blots on pAkt and pp44/42 as well as JC-1 staining and real-time RT-PCR were performed to understand the influence of the treatment at the molecular and gene level.

RESULTS

Due to enhanced anti-proliferative effects, we showed that combined therapy with both drugs was superior to a single treatment with AT101 or DMC. Here, by determination of the combination index, a synergism of the combined drugs was detectable. Phosphorylation and thereby activation of the kinases p44/42 and Akt, which are involved in proliferation and survival processes, were inhibited, the mitochondrial membrane potential of the GBM cells was altered, and genes involved in dormancy-associated processes were regulated by the combined treatment strategy.

CONCLUSION

Combined treatment with different drugs might be an option to efficiently overcome chemoresistance of GBM cells in a long-term treatment strategy.

MicroRNA 145 enhances chemosensitivity of glioblastoma stem cells to demethoxycurcumin

Background: The presence of glioma stem cells (GSCs) is thought to be a key factor responsible for development of the incurable glioblastoma multiforme (GBM). GSCs are often displayed during chemotherapy resistance, except for demethoxycurcumin (DMC), a component of curcumin, which has been previously confirmed to inhibit GSCs proliferation and induce apoptosis.

Purpose: The objective of this study was to identify the main mechanism underlying anti-GSCs resistance by DMC.

Patients and methods: qRT-PCR was used to determine the expression of miR-145 in glioma patients and GSCs, and GSCs were transfected with miR-145 overexpressed vectors. Then, functional analyses (in vitro and in vivo) were performed to confirm the role of miR-145 and DMC in GSCs. Finally, related proteins were tested by immunohistochemistry and Western blot.

Results: miR-145 was atypically low-expressed miRNA in GSCs, and could enhance GSC chemosensitivity to DMC both in vitro and in vivo. Upregulation of miR-145 in GSCs resulted in increased cell growth inhibition and apoptosis to DMC. Further research on the mechanism demonstrated that the combined effects of miR-145 and DMC were involved in the miR-145/SOX2-Wnt/β-catenin pathway. Overexpression of SOX2 reduced GSC resistance to growth inhibition by miR-145+ DMC treatment.

Conclusion: Our data strongly support an important role for miR-145 in enhancing GSC chemosensitivity to DMC by targeting the SOX2-Wnt/β-catenin axis.

Demethoxycurcumin: A naturally occurring curcumin analogue with antitumor properties

The eradication of cancer in a patient remains an elusive challenge despite advances in early detection and diagnosis, chemo- and immunotherapy, pinpoint radiation treatments, and expert surgical intervention. Although significant gains have been made in our understanding of cancer cell biology, a definite cure for most cancers does not exist at present. Thus, it is not surprising that the research and medical communities continue to explore the importance and therapeutic potential of natural products in their multimodality cancer treatment approach. Curcuminoids found in turmeric are one such class of natural products that have been extensively investigated for their potential to halt the progression of cancer cell proliferation and, more important, to stop metastasis from occurring. In this review, we examine one curcuminoid (demethoxycurcumin [DMC]) largely because of its increased stability and better aqueous solubility at physiological pH, unlike the more well-known curcuminoid (curcumin), which is largely unabsorbed after oral ingestion. The present review will focus on the signaling pathways that DMC utilizes to modulate the growth, invasion, and metastasis of cancer cells in an effort to provide enhanced mechanistic insight into DMC's action as it pertains to brain, ovarian, breast, lung, skin, and prostate cancer. Additionally, this review will attempt to provide an overview of DMC's mechanism of action by modulating apoptosis, cell cycle, angiogenesis, metastasis, and chemosensitivity. Lastly, it is hoped that increased understanding will be gained concerning DMC's interactive role with microRNA-551a, 5' adenosine monophosphate-activated protein kinase, nuclear factor-κB, Wnt inhibitory factor-1, and heat shock protein 70 to affect the progression of cancer.

DMC is not better than TMZ on intracranial anti-glioma effects

Previous studies showed Demethoxycurcumin (DMC) has stronger anti-glioma and anti-GSCs effects both in vitro and in vivo. In addition, DMC seems to be lower toxicity than TMZ on nude mice. However, this conclusion was confirmed to be wrong in this study. We have evaluated the antitumor efficacy of DMC or TMZ treatment by an orthotopic glioblastoma xenograft model. Nude mice were injected with U87MG-luc cells in the caudate nucleus of the brain and treated with DMC (30 mg/kg q.d.) or TMZ (10 mg/kg q.d.) by intraperitoneal injection. Bioluminescence imaging (BLI) was used to monitoring tumor growth and response to therapy. Western blot was used to detect the expression of p-Akt, cleaved-caspase-3 and Bax. The average value of BLI showed TMZ determined a significant tumor regression while DMC had a mild regression effect on tumor growth compared with control group. Immunohistochemistry for Ki67, proliferating cell nuclear antigen (PCNA), and TUNEL demonstrated that TMZ more effectively inhibited the expression of Ki67 and PCNA, and increased the ratio of TUNEL-positive cells in in situ tumor tissue. Western blot analysis also indicated that TMZ but not DMC more significantly decreased p-Akt and increased cleaved-caspase-3 and Bax expression.These findings suggested a fact that TMZ appear to be more effective in controlling the growth of glioblastoma than DMC in an orthotopic glioblastoma xenograft model.

Demethoxycurcumin inhibited human epithelia ovarian cancer cells’ growth via up-regulating miR-551a

Curcumin is a natural agent that has ability to dampen tumor cells’ growth. However, the natural form of curcumin is prone to degrade and unstable in vitro. Here, we demonstrated that demethoxycurcumin (a curcumin-related demethoxy compound) could inhibit cell proliferation and induce apoptosis of ovarian cancer cells. Moreover, IRS2/PI3K/Akt axis was inactivated in cells treated with demethoxycurcumin. Quantitative real-time reverse transcription polymerase chain reaction demonstrated that miR-551a was down-regulated in ovarian cancer tissues and ovarian cancer cell lines. Over-expression of miR-551a inhibited cell proliferation and induced apoptosis of ovarian cancer cells, whereas down-regulation of miR-551a exerted the opposite function. Luciferase assays confirmed that there was a binding site of miR-551a in IRS2, and we found that miR-551a exerted tumor-suppressive function by targeting IRS2 in ovarian cancer cells. Remarkably, miR-551a was up-regulated in the cells treated with demethoxycurcumin, and demethoxycurcumin suppressed IRS2 by restoration of miR-551a. In conclusion, demethoxycurcumin hindered ovarian cancer cells’ malignant progress via up-regulating miR-551a.

Up-regulation of miR-497 confers resistance to temozolomide in human glioma cells by targeting mTOR/Bcl-2

The occurrence of an inherent or acquired resistance to temozolomide (TMZ) is a major burden for patients suffering from glioma. Recently, studies have demonstrated that microRNAs play an important role in the regulation of tumor properties in cancers. However, whether miR‐497 contributes to glioma resistance to chemotherapy is not fully understood. In this study, we showed that the expression of miR‐497 was markedly up‐regulated in TMZ‐resistant glioma cells; high miR‐497 expression level was associated with TMZ‐resistant phenotype of glioma cells. The down‐regulation of miR‐497 in glioma cells enhanced the apoptosis‐induction and growth inhibition effects of TMZ both in vitro and in vivo, whereas promotion of miR‐497 increased the chemosensitization of glioma cells to TMZ. The increased level of miR‐497 in TMZ‐resistant glioma cells was concurrent with the up‐regulation of insulin‐like growth factor 1 receptor (IGF1R)/insulin receptor substrate 1 (IRS1) pathway‐related proteins, that is, IGF1R, IRS1, mammalian target of rapamycin (mTOR), and Bcl‐2. In addition, the knockdown of mTOR and Bcl‐2 reduced the tolerance of glioma cells to TMZ. Our results demonstrated that overexpression of miR‐497 is significantly correlated with TMZ resistance in glioma cells by regulating the IGF1R/IRS1 pathway. Therefore, miR‐497 may be used as a new target for treatment of chemotherapy‐resistant glioma.

Demethoxycurcumin was superior to temozolomide in the inhibition of the growth of glioblastoma stem cells in vivo

Temozolomide (TMZ) is widely used in the treatment of glioblastoma multiforme (GBM) as it can effectively inhibit the growth of GBM for some months; however, this cancer type is still incurable. The existence of glioma stem cells (GSCs) is thought to be responsible for the invariable recurrence of GBM after treatment, but GSCs are insensitive to TMZ. Our recent research showed that demethoxycurcumin (DMC), a component of curcumin, was superior to TMZ in its ability to inhibit proliferation and induce apoptosis of GSCs in vitro. In addition, the combined treatment of TMZ + DMC induced more obvious anti-GSC effects. However, in this study, no obvious synergistic anti-GSC effects of TMZ + DMC were found in vivo, while DMC was still superior to TMZ with respect to growth inhibition of GSCs in vivo. Furthermore, immunohistochemistry for proliferating cell nuclear antigen (PCNA) showed that such inhibitory effects were mainly related to the inhibition of cell proliferation rather than to apoptosis. However, a high concentration of DMC (50 mg/kg) alone or combined with TMZ could also induce approximately 10 % of the cells to undergo apoptosis according to a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Finally, an investigation of the underlying mechanism revealed that the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) 3 signaling pathway played an important role in the anti-GSC effects. When the JAK inhibitor AG490 was applied, the anti-GSC effects of DMC were enhanced. Taken together, the present work reveals that DMC is superior to TMZ with respect to its anti-GSC effects in vivo, which are mediated through the inhibition of the activation of the JAK/STAT3 pathway; however, DMC demonstrated no synergistic effects with TMZ.

Role of Redox Status in Development of Glioblastoma

Glioblastoma multiforme (GBM) is a highly aggressive neoplasia, prognosis remains dismal, and current therapy is mostly palliative. There are no known risk factors associated with gliomagenesis; however, it is well established that chronic inflammation in brain tissue induces oxidative stress in astrocytes and microglia. High quantities of reactive species of oxygen into the cells can react with several macromolecules, including chromosomal and mitochondrial DNA, leading to damage and malfunction of DNA repair enzymes. These changes bring genetic instability and abnormal metabolic processes, favoring oxidative environment and increase rate of cell proliferation. In GBM, a high metabolic rate and increased basal levels of reactive oxygen species play an important role as chemical mediators in the regulation of signal transduction, protecting malignant cells from apoptosis, thus creating an immunosuppressive environment. New redox therapeutics could reduce oxidative stress preventing cellular damage and high mutation rate accompanied by chromosomal instability, reducing the immunosuppressive environment. In addition, therapies directed to modulate redox rate reduce resistance and moderate the high rate of cell proliferation, favoring apoptosis of tumoral cells. This review describes the redox status in GBM, and how this imbalance could promote gliomagenesis through genomic and mitochondrial DNA damage, inducing the pro-oxidant and proinflammatory environment involved in tumor cell proliferation, resistance, and immune escape. In addition, some therapeutic agents that modulate redox status and might be advantageous in therapy against GBM are described.