Mechanistic evaluation of the signaling events regulating curcumin-mediated chemosensitization of breast cancer cells to 5-fluorouracil

The Bright Side of Curcumin: A Narrative Review of Its Therapeutic Potential in Cancer Management

Curcumin, a polyphenolic compound derived from Curcuma longa, exhibits significant therapeutic potential in cancer management. This review explores curcumin's mechanisms of action, the challenges related to its bioavailability, and its enhancement through modern technology and approaches. Curcumin demonstrates strong antioxidant and anti-inflammatory properties, contributing to its ability to neutralize free radicals and inhibit inflammatory mediators. Its anticancer effects are mediated by inducing apoptosis, inhibiting cell proliferation, and interfering with tumor growth pathways in various colon, pancreatic, and breast cancers. However, its clinical application is limited by its poor bioavailability due to its rapid metabolism and low absorption. Novel delivery systems, such as curcumin-loaded hydrogels and nanoparticles, have shown promise in improving curcumin bioavailability and therapeutic efficacy. Additionally, photodynamic therapy has emerged as a complementary approach, where light exposure enhances curcumin's anticancer effects by modulating molecular pathways crucial for tumor cell growth and survival. Studies highlight that combining low concentrations of curcumin with visible light irradiation significantly boosts its antitumor efficacy compared to curcumin alone. The interaction of curcumin with cytochromes or drug transporters may play a crucial role in altering the pharmacokinetics of conventional medications, which necessitates careful consideration in clinical settings. Future research should focus on optimizing delivery mechanisms and understanding curcumin's pharmacokinetics to fully harness its therapeutic potential in cancer treatment.

Enhancing therapeutic efficacy: sustained delivery of 5-fluorouracil (5-FU) via thiolated chitosan nanoparticles targeting CD44 in triple-negative breast cancer

Our current study reports the successful synthesis of thiolated chitosan-based nanoparticles for targeted drug delivery of 5-Fluorouracil. This process was achieved through the ionic gelation technique, aiming to improve the efficacy of the chemotherapeutic moiety by modifying the surface of the nanoparticles (NPs) with a ligand. We coated these NPs with hyaluronic acid (HA) to actively target the CD44 receptor, which is frequently overexpressed in various solid malignancies, including breast cancer. XRD, FTIR, SEM, and TEM were used for the physicochemical analysis of the NPs. These 5-Fluorouracil (5-FU) loaded NPs were evaluated on MDA-MB-231 (a triple-negative breast cell line) and MCF-10A (normal epithelial breast cells) to determine their in vitro efficacy. The developed 5-FU-loaded NPs exhibited a particle size within a favorable range (< 300 nm). The positive zeta potential of these nanoparticles facilitated their uptake by negatively charged cancer cells. Moreover, they demonstrated robust stability and achieved high encapsulation efficiency. These nanoparticles exhibited significant cytotoxicity compared to the crude drug (p < 0.05) and displayed a promising release pattern consistent with the basic diffusion model. These traits improve the pharmacokinetic profile, efficacy, and ability to precisely target these nanoparticles, offering a potentially successful anticancer treatment for breast cancer. However, additional in vivo assessments of these formulations are obligatory to confirm these findings.

Curcumin/L-OHP co-loaded HAP for cGAS-STING pathway activation to enhance the natural immune response in colorectal cancer

Insufficient immune cell infiltration into the tumor microenvironment (TME) greatly compromises the clinical application of immune-checkpoint inhibitors (ICIs)-based immunotherapy. Recent findings have shown that activation of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway can enhance natural immunity and increase lymphocyte infiltration into the TME, which presents a promising strategy for cancer immunotherapy. In this study, we constructed hydroxyapatite nanoparticles co-loaded with curcumin and L-oxaliplatin (Cur/L-OHP@HAP NPs). We analyzed the particle-size distribution, zeta potential, spectral characteristics (Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy), and drug-release properties of the Cur/L-OHP@HAP NPs. The cellular uptake of the Cur/L-OHP@HAP NPs detected by flow cytometry and confocal laser-scanning microscopy. We comprehensively evaluated the anti-tumor properties and immune-activating effects of the NPs, both in vitro and in vivo. Physicochemical characterizations demonstrated that the Cur/L-OHP@HAP NPs were successfully synthesized and were capable of pH-dependent drug release. Notably, the Cur/L-OHP@HAP NPs efficiently entered cancer cells, after which the released L-OHP induced nuclear DNA (nDNA) damage to some extent. HAP promoted the release of intracellular Ca2+ stores in cancer cells, and curcumin inhibited Ca2+ efflux, resulting in intracellular Ca2+ overload and the release of mitochondrial DNA (mtDNA). Damage to both nDNA and mtDNA greatly stimulated the cGAS-STING pathway, thereby activating natural immunity, accompanied by immune cell recruitment to the TME. In summary, the Cur/L-OHP@HAP NPs show good prospects for improving cancer immunotherapy.

An Overview of the Enhanced Effects of Curcumin and Chemotherapeutic Agents in Combined Cancer Treatments

Due to the progressive ageing of the human population, the number of cancer cases is increasing. For this reason, there is an urgent need for new treatments that can prolong the lives of cancer patients or ensure them a good quality of life. Although significant progress has been made in the treatment of cancer in recent years and the survival rate of patients is increasing, limitations in the use of conventional therapies include the frequent occurrence of side effects and the development of resistance to chemotherapeutic agents. These limitations are prompting researchers to investigate whether combining natural agents with conventional drugs could have a positive therapeutic effect in cancer treatment. Several natural bioactive compounds, especially polyphenols, have been shown to be effective against cancer progression and do not exert toxic effects on healthy tissues. Many studies have investigated the possibility of combining polyphenols with conventional drugs as a novel anticancer strategy. Indeed, this combination often has synergistic benefits that increase drug efficacy and reduce adverse side effects. In this review, we provide an overview of the studies describing the synergistic effects of curcumin, a polyphenol that has been shown to have extensive cytotoxic functions against cancer cells, including combined treatment. In particular, we have described the results of recent preclinical and clinical studies exploring the pleiotropic effects of curcumin in combination with standard drugs and the potential to consider it as a promising new tool for cancer therapy.

Recent Advances in Curcumin-Based Combination Nanomedicines for Cancer Therapy

Standard cancer chemotherapeutics often produce significant adverse effects and eventually lose their effectiveness due to the emergence of resistance mechanisms. As a result, patients with malignant tumors experience a poor quality of life and a short lifespan. Thus, combination medication regimens provide various advantages, including increased success rate, fewer side effects, and fewer occurrences of resistance. Curcumin (Cur), a potential phytochemical from turmeric, when coupled with traditional chemotherapeutics, has been established to improve the effectiveness of cancer treatment in clinical and preclinical investigations. Cur not only exerts multiple mechanisms resulting in apoptotic cancer cell death but also reduces the resistance to standard chemotherapy drugs, mainly through downregulating the multi-drug resistance (MDR) cargoes. Recent reports showed the beneficial outcomes of Cur combination with many chemotherapeutics in various malignancies. Nevertheless, owing to the limited bioavailability, devising co-delivery strategies for Cur and conventional pharmaceuticals appears to be required for clinical settings. This review summarized various Cur combinations with standard treatments as cancer therapeutics.

Curcuminoids as Anticancer Drugs: Pleiotropic Effects, Potential for Metabolic Reprogramming and Prospects for the Future

The number of published studies on curcuminoids in cancer research, including its lead molecule curcumin and synthetic analogs, has been increasing substantially during the past two decades. Insights on the diversity of inhibitory effects they have produced on a multitude of pathways involved in carcinogenesis and tumor progression have been provided. As this wealth of data was obtained in settings of various experimental and clinical data, this review first aimed at presenting a chronology of discoveries and an update on their complex in vivo effects. Secondly, there are many interesting questions linked to their pleiotropic effects. One of them, a growing research topic, relates to their ability to modulate metabolic reprogramming. This review will also cover the use of curcuminoids as chemosensitizing molecules that can be combined with several anticancer drugs to reverse the phenomenon of multidrug resistance. Finally, current investigations in these three complementary research fields raise several important questions that will be put among the prospects for the future research related to the importance of these molecules in cancer research.

5-FU and the dietary flavonoid carvacrol: a synergistic combination that induces apoptosis in MCF-7 breast cancer cells

Along with the benefits of chemotherapy in the treatment of breast cancer, the side effects of these drugs along with drug resistance make their use complicated. One of the solutions to overcome this problem is the use of herbal products and combination therapy. In this research, we try to investigate the effects of carvacrol, a monoterpene flavonoid, in combination with the chemotherapy drug 5-FU. Combination index method was used for the drug-drug interactions analysis based on the Chou and Talalay method and the data from MTT assays. Apoptosis was assessed by the ELISA cell death method. P-glycoprotein expression was evaluated at the gene level by Real-time PCR. Here, we described the first experimental evidence for the existence of synergism between carvacrol and 5-FU in the in vitro model of breast cancer. MTT assay results showed combination treatment of the cells with carvacrol and 5-FU decreased 5-FU concentrations significantly. Incubation of the cells with carvacrol neutralized P-glycoprotein overexpression in qPCR assay (P ≤ 0.05). Compared with adding verapamil (a P-glycoprotein inhibitor) to 5-FU, the combination of carvacrol and 5-FU caused a further increase in the percentage of apoptotic cells when the cells were treated with both agents. Our results suggest that carvacrol can downregulate P-gp expression and combination therapy with carvacrol and 5-FU is considered a novel approach to improve the efficacy of chemotherapeutics in cancer patients with high P-glycoprotein expression.

Drug-herb combination therapy in cancer management

Cancer is the second leading cause of fatality all over the world. Various unwanted side effects are being reported with the use of conventional chemotherapy. The plant derived bioactive compounds are the prominent alternative medicinal approach for reduction of chemotherapy associated side effects. The data is collected from Pubmed, Sci-hub, Google scholar, and Research gate were systematically searched up to year 2020. Several herbal drugs have been investigated and found with grateful anti-cancer potentials hence, it can be used in combination with chemotherapy for the depletion of associated side-effects. Herbal drugs and their extracts contain a mixture of active ingredients, which show interactions within themselves and along with chemotherapeutic agents to show either synergistic or antagonistic therapeutic effects. Therefore, it is necessary to develop alternative treatment to control chemotherapy associated side-effects. In this review, we discussed some of the significant chemical compounds, which could be efficient against cancer. This review focuses on the different herbal drugs that play an important role in the treatment of cancer and its associated side-effects. This study aimed to evaluate the efficacy of herbal treatment in combination with chemotherapy for cancer treatment.

A Comprehensive Review on the Benefits and Problems of Curcumin with Respect to Human Health

Curcumin is the most important active component in turmeric extracts. Curcumin, a natural monomer from plants has received a considerable attention as a dietary supplement, exhibiting evident activity in a wide range of human pathological conditions. In general, curcumin is beneficial to human health, demonstrating pharmacological activities of anti-inflammation and antioxidation, as well as antitumor and immune regulation activities. Curcumin also presents therapeutic potential in neurodegenerative, cardiovascular and cerebrovascular diseases. In this review article, we summarize the advancements made in recent years with respect to curcumin as a biologically active agent in malignant tumors, Alzheimer’s disease (AD), hematological diseases and viral infectious diseases. We also focus on problems associated with curcumin from basic research to clinical translation, such as its low solubility, leading to poor bioavailability, as well as the controversy surrounding the association between curcumin purity and effect. Through a review and summary of the clinical research on curcumin and case reports of adverse effects, we found that the clinical transformation of curcumin is not successful, and excessive intake of curcumin may have adverse effects on the kidneys, heart, liver, blood and immune system, which leads us to warn that curcumin has a long way to go from basic research to application transformation.

Curcumin as an Enhancer of Therapeutic Efficiency of Chemotherapy Drugs in Breast Cancer

Female breast cancer is the world’s most prevalent cancer in 2020. Chemotherapy still remains a backbone in breast cancer therapy and is crucial in advanced and metastatic breast cancer treatment. The clinical efficiency of chemotherapy regimens is limited due to tumor heterogeneity, chemoresistance, and side effects. Chemotherapeutic drug combinations with natural products hold great promise for enhancing their anticancer efficacy. Curcumin is an ideal chemopreventive and chemotherapy agent owning to its multitargeting function on various regulatory molecules, key signaling pathways, and pharmacological safety. This review aimed to elucidate the potential role of curcumin in enhancing the efficacy of doxorubicin, paclitaxel, 5-fluorouracil, and cisplatin via combinational therapy. Additionally, the molecular mechanisms underlying the chemosensitizing activity of these combinations have been addressed. Overall, based on the promising therapeutic potential of curcumin in combination with conventional chemotherapy drugs, curcumin is of considerable value to develop as an adjunct for combination chemotherapy with current drugs to treat breast cancer. Furthermore, this topic may provide the frameworks for the future research direction of curcumin–chemotherapy combination studies and may benefit in the development of a novel therapeutic strategy to maximize the clinical efficacy of anticancer drugs while minimizing their side effects in the future breast cancer treatment.

Cancer Chemoprevention: A Strategic Approach Using Phytochemicals

Cancer chemoprevention approaches are aimed at preventing, delaying, or suppressing tumor incidence using synthetic or natural bioactive agents. Mechanistically, chemopreventive agents also aid in mitigating cancer development, either by impeding DNA damage or by blocking the division of premalignant cells with DNA damage. Several pre-clinical studies have substantiated the benefits of using various dietary components as chemopreventives in cancer therapy. The incessant rise in the number of cancer cases globally is an issue of major concern. The excessive toxicity and chemoresistance associated with conventional chemotherapies decrease the success rates of the existent chemotherapeutic regimen, which warrants the need for an efficient and safer alternative therapeutic approach. In this scenario, chemopreventive agents have been proven to be successful in protecting the high-risk populations from cancer, which further validates chemoprevention strategy as rational and promising. Clinical studies have shown the effectiveness of this approach in managing cancers of different origins. Phytochemicals, which constitute an appreciable proportion of currently used chemotherapeutic drugs, have been tested for their chemopreventive efficacy. This review primarily aims to highlight the efficacy of phytochemicals, currently being investigated globally as chemopreventives. The clinical relevance of chemoprevention, with special emphasis on the phytochemicals, curcumin, resveratrol, tryptanthrin, kaempferol, gingerol, emodin, quercetin genistein and epigallocatechingallate, which are potential candidates due to their ability to regulate multiple survival pathways without inducing toxicity, forms the crux of this review. The majority of these phytochemicals are polyphenols and flavanoids. We have analyzed how the key molecular targets of these chemopreventives potentially counteract the key drivers of chemoresistance, causing minimum toxicity to the body. An overview of the underlying mechanism of action of these phytochemicals in regulating the key players of cancer progression and tumor suppression is discussed in this review. A summary of the clinical trials on the important phytochemicals that emerge as chemopreventives is also incorporated. We elaborate on the pre-clinical and clinical observations, pharmacokinetics, mechanism of action, and molecular targets of some of these natural products. To summarize, the scope of this review comprises of the current status, limitations, and future directions of cancer chemoprevention, emphasizing the potency of phytochemicals as effective chemopreventives.

Evaluation of the Effects of Nanomicellar Curcumin, Berberine, and Their Combination with 5-Fluorouracil on Breast Cancer Cells

INTRODUCTION

Breast cancer is one of the main challenging areas in cancer treatment. Natural compounds such as curcumin and berberine have been approved with anticancer effects and are more favorable to people. Here, we investigated the potential synergistic anticancer effects of these two compounds in combination with the standard cancer drug 5-FU on the growth of MCF-7 breast cancer cells.

MATERIALS AND METHODS

This study tested the effects of six different treatments on cancer cell growth: A) control; B) curcumin; C) berberine; D) 5-FU; E) curcumin + berberine; and F) curcumin + berberine + 5-FU. The IC₅₀ concentration of each treatment on cancer cell growth was determined using the MTT assay. Invasiveness of cells grown in 3D culture was analyzed using the transwell chamber technique. Expression levels of genes involved in cancer cell growth and survival (WNT1, APC, AXIN1, CTNNB1, TCF, MTOR, AKT1, MAPK1, PTEN, BIRC5, CCNG1) were evaluated by real-time PCR.

RESULTS

There was a reduction in cancer cell growth and invasion, and an increase in cellular decomposition across all treatment groups compared to the control with the strongest effects seen in the combined curcumin/berberine/5-FU group. The expression levels of all tested genes were altered in all treatment groups compared to the control, with that of WNT1, CTNNB1, TCF, MTOR, AKT1, BIRC5, and CCND1 showing the most robust changes in the combined curcumin/berberine/5-FU treatment.

CONCLUSIONS

All treatment groups had anti-growth, anti-invasion, and pro-apoptotic effects on MCF-7 breast cancer cells in culture. In addition, all treatment groups showed changes in the expression of the genes involved in cancer cell growth and survival with the strongest effects found for the curcumin/berberine/5-FU combination. Therefore, curcumin and berberine may improve the anticancer effects of chemotherapy and these natural compounds should undergo further testing as potential adjuvants.

Current Advancements of Plant-Derived Agents for Triple-Negative Breast Cancer Therapy through Deregulating Cancer Cell Functions and Reprogramming Tumor Microenvironment

Triple-negative breast cancer (TNBC) is defined based on the absence of estrogen, progesterone, and human epidermal growth factor receptor 2 receptors. Currently, chemotherapy is the major therapeutic approach for TNBC patients; however, poor prognosis after a standard chemotherapy regimen is still commonplace due to drug resistance. Abnormal tumor metabolism and infiltrated immune or stromal cells in the tumor microenvironment (TME) may orchestrate mammary tumor growth and metastasis or give rise to new subsets of cancer cells resistant to drug treatment. The immunosuppressive mechanisms established in the TME make cancer cell clones invulnerable to immune recognition and killing, and turn immune cells into tumor-supporting cells, hence allowing cancer growth and dissemination. Phytochemicals with the potential to change the tumor metabolism or reprogram the TME may provide opportunities to suppress cancer metastasis and/or overcome chemoresistance. Furthermore, phytochemical intervention that reprograms the TME away from favoring immunoevasion and instead towards immunosurveillance may prevent TNBC metastasis and help improve the efficacy of combination therapies as phyto-adjuvants to combat drug-resistant TNBC. In this review, we summarize current findings on selected bioactive plant-derived natural products in preclinical mouse models and/or clinical trials with focus on their immunomodulatory mechanisms in the TME and their roles in regulating tumor metabolism for TNBC prevention or therapy.

Chemoresistance in breast cancer: PI3K/Akt pathway inhibitors vs the current chemotherapy

Breast cancer is the most prevalent type of cancer among women. Several types of drugs, targeting the specific proteins expressed on the breast cancer cell surface (such as receptor tyrosine kinases and immune checkpoint regulators) and proteins involved in cell cycle and motility (including cyclin-dependent kinases, DNA stabilisers, and cytoskeleton modulators) are approved for different subtypes of breast cancer. However, breast cancer also has a poor response to conventional chemotherapy due to intrinsic and acquired resistance, and an Akt fingerprint is detectable in most drug-resistant cases. Overactivation of Akt and its upstream and downstream regulators in resistant breast cancer cells is considered a major potential target for novel anti-cancer therapies, suggesting that Akt signalling acts as a cellular mechanism against chemotherapy. The present review has shown that sustained activation of Akt results in resistance to different types of chemotherapy. Akt signalling plays a cellular defence role against chemotherapy and (1) enhances multi-drug resistance, (2) increases reactive oxygen species at breast tumor microenvironment, (3) enhances anaerobic metabolism, (4) inhibits the tricarboxylic cycle, (5) promotes PD-L1 upregulation, (6) inhibits apoptosis, (7) increases glucose uptake, and more importantly (8) recruits and interconnects the plasma membrane, nucleus, endoplasmic reticulum, and mitochondria to hijack breast cancer cells and rescue these cells from chemotherapy. Therefore, Akt signalling is considered a cellular defence mechanism employed against chemotherapeutic effects. In addition, interfering roles of PI3K/Akt signalling on the current cytotoxic and molecularly targeted therapy as well as immunotherapy of breast cancer are discussed with a clinical approach. Although, alpelisib, a PIK3CA inhibitor, is the only PI3K/Akt pathway inhibitor approved for breast cancer, we also highlight well-evaluated inhibitors of PI3K/Akt signalling based on different subtypes of breast cancer, which are under clinical trials whether as monotherapy or in combination with other types of chemotherapy.

Apigenin enhances apoptosis induction by 5-fluorouracil through regulation of thymidylate synthase in colorectal cancer cells

Although effective drugs have been developed, including 5-fluorouracil (5-FU), advanced colorectal cancer (CRC) shows low therapeutic sensitivity resulting from the development of 5-FU resistance. Thymidylate synthase (TS) is a target protein of 5-FU, and elevated TS lowers the 5-FU sensitivity of CRC cells. Here, we tested the efficacy of several candidate phytochemicals against human CRC-derived HCT116 cells expressing wild-type tumor suppressor protein P53 and HT29 cells expressing mutant P53. Among them, we found that apigenin enhanced the inhibitory effect of 5-FU on cell viability. In addition, apigenin inhibited the upregulation of TS induced by 5-FU. Apigenin also potentiated 5-FU-induced apoptosis of HCT116 cells and enhanced cell cycle disruption. Furthermore, apigenin increased reactive oxygen species production, intracellular and intramitochondrial Ca²⁺ concentrations, and mitochondrial membrane potential upon cotreatment with 5-FU. Knockdown of forkhead box protein M, a transcription factor modulating 5-FU sensitivity, enhanced the potentiation of apoptosis by apigenin in HCT116 cells. Moreover, apigenin suppressed TS expression and inhibited the viability of 5-FU-resistant HCT116 cells. Therefore, apigenin may improve the therapeutic efficacy of 5-FU against CRC by suppressing TS, but apoptosis induction is mainly dependent on functional P53.

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Apigenin inhibits the upregulation of TS induced by 5-FU for apoptosis of CRC.

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FOXM1 silencing enhances the potentiation of apoptosis by apigenin.

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Suppressing TS and promoting P53 activity by apigenin reduce acquired 5-FU resistance.

Modulation of inflammation by phytochemicals to enhance efficacy and reduce toxicity of cancer chemotherapy

Treatment of cancer with chemotherapeutic drugs is associated with numerous adverse effects as well as the eventual development of resistance to chemotherapy. There is a great need for complementary therapies such as botanicals and nutritional supplements with little or no side effects that prevent resistance to chemotherapy and reduce its adverse effects. Inflammation plays a major role in the development of chemoresistance and the adverse effects of chemotherapy. Phytochemicals have well-established anti-inflammatory effects; thus, they could be used as complementary therapies along with chemotherapy to increase its efficacy and reduce its toxicity. Botanical compounds inhibit the NF-κB signaling pathway, which plays an important role in the generation of inflammation, chemotherapy resistance, and modulation of cell survival and apoptosis. Botanicals have previously been studied extensively for their cancer chemopreventive activities and are generally considered safe for human consumption. The present review focuses on the modulation of inflammation by phytochemicals and their role in increasing the efficacy and reducing the toxicity of cancer chemotherapy.

Targeting Thymidylate Synthase Enhances the Chemosensitivity of Triple-Negative Breast Cancer Towards 5-FU-Based Combinatorial Therapy

BACKGROUND

The ongoing treatment modalities for breast cancer (BC) primarily rely on the expression status of ER, PR and HER-2 receptors in BC tissues. Our strategy of chemosensitization provides new insights to counter chemoresistance, a major obstacle that limits the benefits of chemotherapy of mammary cancers.

METHODS

By utilizing a murine breast cancer model employing NSG mice bearing orthotopic triple-negative breast cancer (TNBC) xenografts, we have evaluated the ability of phytochemical curcumin in chemosensitizing BC to 5-Fluorouracil (5-FU) chemotherapy and the differential modulations of cellular events in response to this strategy, independent of their receptor status.

RESULTS

A significant synergistic antitumor potential was observed in the murine model with a sub-optimal dose treatment of 5-FU plus curcumin, as evaluated by a reduction in the tumor-related parameters. We authenticated the pivotal role of thymidylate synthase (TS) in regulating the 5-FU-curcumin synergism using the TNBC pre-clinical model. Our study also confirmed the pharmacological safety of this chemotherapeutic plus phytoactive combination using acute and chronic toxicity studies in Swiss albino mice. Subsequently, the molecular docking analysis of curcumin binding to TS demonstrated the affinity of curcumin towards the cofactor-binding site of TS, rather than the substrate-binding site, where 5-FU binds. Our concomitant in vivo and in silico evidence substantiates the superior therapeutic index of this combination.

CONCLUSION

This is the first-ever pre-clinical study portraying TS as the critical target of combinatorial therapy for mammary carcinomas and therefore we recommend its clinical validation, especially in TNBC patients, who currently have limited therapeutic options.

Curcumin: Modulator of Key Molecular Signaling Pathways in Hormone-Independent Breast Cancer

Simple Summary

Breast cancer remains the most commonly diagnosed cancer and the leading cause of cancer death among females worldwide. It is a highly heterogeneous disease, classified according to hormone and growth factor receptor expression. Patients with triple negative breast cancer (TNBC) (estrogen receptor-negative/progesterone receptor-negative/human epidermal growth factor receptor (HER2)-negative) and hormone-independent HER2 overexpressing subtypes still represent highly aggressive behavior, metastasis, poor prognosis, and drug resistance. Thus, new alternative anticancer agents based on the use of natural products have been receiving enormous attention. In this regard, curcumin is a promising lead in cancer drug discovery due its ability to modulate a diverse range of molecular targets and signaling pathways. The current review has emphasized the underlying mechanism of curcumin anticancer action mediated through the modulation of PI3K/Akt/mTOR, JAK/STAT, MAPK, NF-ĸB, p53, Wnt/β-catenin, apoptosis, and cell cycle pathways in hormone-independent breast cancer, providing frameworks for future studies and insights to improve its efficiency in clinical practice.

Abstract

Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death among women worldwide. Despite the overall successes in breast cancer therapy, hormone-independent HER2 negative breast cancer, also known as triple negative breast cancer (TNBC), lacking estrogens and progesterone receptors and with an excessive expression of human epidermal growth factor receptor 2 (HER2), along with the hormone-independent HER2 positive subtype, still remain major challenges in breast cancer treatment. Due to their poor prognoses, aggressive phenotype, and highly metastasis features, new alternative therapies have become an urgent clinical need. One of the most noteworthy phytochemicals, curcumin, has attracted enormous attention as a promising drug candidate in breast cancer prevention and treatment due to its multi-targeting effect. Curcumin interrupts major stages of tumorigenesis including cell proliferation, survival, angiogenesis, and metastasis in hormone-independent breast cancer through the modulation of multiple signaling pathways. The current review has highlighted the anticancer activity of curcumin in hormone-independent breast cancer via focusing on its impact on key signaling pathways including the PI3K/Akt/mTOR pathway, JAK/STAT pathway, MAPK pathway, NF-ĸB pathway, p53 pathway, and Wnt/β-catenin, as well as apoptotic and cell cycle pathways. Besides, its therapeutic implications in clinical trials are here presented.

Cytotoxic, chemosensitizing and radiosensitizing effects of curcumin based on thioredoxin system inhibition in breast cancer cells: 2D vs. 3D cell culture system

Targeting the thioredoxin/thioredoxin reductase (Trx/TrxR) system is a promising strategy to overcome cancer resistance to conventional therapy. The present study investigated the effect of curcumin on the Trx/TrxR system either alone or in combination with chemotherapy, or radiotherapy in human MCF-7 breast cancer cells seeded in 2 and 3D culture systems. Cell viability, thioredoxin reductase 1 (TrxR1) activity, and the genetic expression of Trx, TrxR1, Bcl2 and BAX genes were studied. The findings showed that the mode of culture significantly affected the response of cancer cells to different treatment modalities, as well as their gene expression patterns. Curcumin treatment resulted in a reduction of breast cancer cell proliferation and induction of apoptosis, an effect that may be mediated by manipulating Trx system components, mainly Trx expression, and to a lesser extent TrxR1 expression and concentration. Furthermore, curcumin increased the sensitivity of breast cancer cells to chemotherapy and radiotherapy by reducing Trx and TrxR1 expression levels. Thus, curcumin may have a potential role as a dose-modifying agent that can be used either to sensitize resistant cells to therapy or to reduce the dose of these therapeutic agents.

Curcumin Rescues Doxorubicin Responsiveness via Regulating Aurora a Signaling Network in Breast Cancer Cells

BACKGROUND

Insensitivity towards anthracycline drugs like doxorubicin poses a significant challenge in the treatment of breast cancer. Among several factors, Aurora A (a mitotic serine threonine kinase) plays crucial roles in acquiring non-responsiveness towards doxorubicin. However, the mechanisms underlying need to be elucidated. The present study was therefore designed to evaluate the underlying mechanisms of Aurora A mediated doxorubicin insensitivity in MCF-7Dox/R, an isolated resistant-subline of MCF-7 (breast adenocarcinoma cell line). Effect of curcumin, a natural phytochemical in restoring doxorubicin sensitivity by targeting Aurora A was assessed furthermore.

METHODS

A doxorubicin resistant subline (MCF-7Dox/R) was isolated from the parental MCF-7 cells by treating the cell with gradual step-wise increasing concentration of the drug. Expressions of Aurora A and its target proteins (Akt, IκBα and NFκB) were assessed in both parental and MCF-7Dox/R cells. Both the cell lines were pretreated with curcumin prior to doxorubicin treatment. Cellular proliferation rate was measured using BrdU (5-bromo-2'-deoxyuridine) assay kit. Intracellular doxorubicin accumulation was estimated spectrofluorimetrically. Cellular uptake of curcumin (spectrophotometric and spectrofluorimetric method) and its nuclear localization was confirmed by confocal microscopic study. Protein expressions were determined by western blot analysis. Localization of Aurora A was ascertained by immunofluorescence assay. To explore the possible outcome of impact of curcumin on Aurora A, cell-cycle distribution and apoptosis were performed subsequently.

RESULTS

Higher expressions of Aurora A in MCF-7Dox/R cells led to phosphorylation of Akt as well as IκBα. Phosphorylated IκBα preceded release of NFκB. Phospho-Akt, NFκB consequentially decreased doxorubicin accumulation by enhancing the expressions of ABCG2 and Pgp1 respectively. Curcumin by regulating Aurora A and its target molecules sensitized resistant subline towards doxorubicin mediated G2/M-arrest and apoptosis.

CONCLUSION

Molecular targeting of Aurora A by curcumin restores chemosensitivity by increasing the efficacy of doxorubicin in breast cancer.<br />.

Combination treatment of bicalutamide and curcumin has a strong therapeutic effect on androgen receptor-positive triple-negative breast cancers

Triple-negative breast cancers account for approximately 15-20% of breast cancer patients. Due to lack of expression of estrogen receptor, PR and human epidermal growth factor receptor 2 in triple-negative breast cancers, there are no targeted therapies available for these cancers. Therefore, a major research priority is to find potential therapeutic targets. Androgen receptor is present in 80-90% of all breast cancers, including 55% of estrogen receptor-α-negative cancers and 12%-35% of triple-negative breast cancers. Androgen receptor stimulates growth and survival in triple-negative breast cancer cells. Treatment with bicalutamide, an androgen receptor antagonist, has a good benefit for AR triple-negative breast cancer patients. AR triple-negative breast cancer cells were treated with curcumin or bicalutamide alone or in combination of both together. Cell growth, apoptosis and Wnt signaling pathways were examined. We found that curcumin dramatically suppressed Wnt signaling pathway in AR triple-negative breast cancer cells. Curcumin treatment inhibited androgen receptor protein expression in AR triple-negative breast cancer cells. Combination treatment of curcumin and bicalutamide has a robust increase in apoptosis. Furthermore, the combination treatment suppressed the growth of AR triple-negative breast cancer cells more effectively than with the single drug alone. Our data indicate that androgen receptor inhibition is a potential therapeutic approach for AR triple-negative breast cancers. In summary, our study for the first time shows that the combination treatment of curcumin and bicalutamide is effective in AR triple-negative breast cancer cells.

Antitumor effects of curcumin on the proliferation, migration and apoptosis of human colorectal carcinoma HCT‑116 cells

Curcumin is the main component of the Chinese herbal plant turmeric, which has been demonstrated to possess antitumor and other pharmacological properties. The aim of the present study was to investigate the effects of curcumin on the viability, migration and apoptosis of human colorectal carcinoma HCT-116 cells, and to explore the underlying molecular mechanisms. In addition, it was investigated whether the antitumor effect of curcumin on HCT-116 cells could match that of the chemotherapeutic drug 5-fluorouracil (5-FU). HCT-116 cells were treated with curcumin (10, 20 and 30 µM) and 5-FU (500 µM), and cell viability and proliferation were detected by Cell Counting Kit-8 and colony formation assays, respectively. The migration and invasion of treated cells were determined using Transwell and carboxyfluorescein succinimidyl amino ester fluorescent labeling assays. Cell cycle distribution and apoptosis rates were detected by flow cytometry. Furthermore, cell morphology changes associated with apoptosis were observed by fluorescence microscopy with acridine orange/ethidium bromide dual staining. To investigate the possible underlying molecular mechanisms, the gene and protein levels of Fas, Fas-associated via death domain (FADD), caspase-8, caspase-3, matrix metalloproteinase (MMP)-9, nuclear factor (NF)-κB, E-cadherin and claudin-3 were detected using quantitative PCR analysis, zymography and western blotting. The results revealed that curcumin markedly inhibited the viability and proliferation of HCT-116 cells in a dose- and time-dependent manner. The migration, aggregation and invasion of HCT-116 cells into the lungs of mice were decreased by curcumin treatment in a dose-dependent manner. S-phase arrest and gradually increased apoptotic rates of HCT-116 cells were observed with increasing curcumin concentrations. Additionally, the mRNA and protein levels of apoptosis-associated proteins (Fas, FADD, caspase-8 and caspase-3) and E-cadherin in HCT-116 cells were upregulated following treatment with curcumin in a dose-dependent manner. By contrast, the expression of migration-associated proteins, including MMP-9, NF-κB and claudin-3, was downregulated with increasing curcumin concentrations. These data suggested that the inhibitory effect of curcumin on HCT-116 cells may match that of 5-FU. Therefore, curcumin induced cell apoptosis and inhibited tumor cell metastasis by regulating the NF-κB signaling pathway, and its therapeutic effect may be comparable to that of 5-FU.

Medicinal Herbs Used in Traditional Management of Breast Cancer: Mechanisms of Action

Background: Breast cancer is one of the principal causes of death among women and there is a pressing need to develop novel and effective anti-cancer agents. Natural plant products have shown promising results as anti-cancer agents. Their effectiveness is reported as decreased toxicity in usage, along with safety and less recurrent resistances compared with hormonal targeting anti-cancer agents. Methods: A literature search was conducted for all English-language literature published prior to June 2020. The search was conducted using electronic databases, including PubMed, Embase, Web of Science, and Cochrane Library. The search strategy included keywords such as breast cancer, herbs, anti-cancer biologically active components, clinical research, chemotherapy drugs amongst others. Results: The literature provides documented evidence of the chemo-preventative and chemotherapeutic properties of Ginseng, garlic (Allium sativum), Black cohosh (Actaea racemose), Tumeric (Curcuma longa), Camellia sinenis (green tea), Echinacea, Arctium (burdock), Flaxseed (Linum usitatissimum) and Black Cumin (Nigella sativa). Conclusions: The nine herbs displayed anti-cancer properties and their outcomes and mechanisms of action include inhibition of cell proliferation, angiogenesis and apoptosis as well as modulation of key intracellular pathways. However, more clinical trials and cohort human studies should be conducted to provide key evidence of their medical benefits.

TRPM8-regulated calcium mobilization plays a critical role in synergistic chemosensitization of Borneol on Doxorubicin

Background: Lung cancer has a high mortality rate and is resistant to multiple chemotherapeutics. Natural Borneol (NB) is a monoterpenoid compound that facilitates the bioavailability of drugs. In this study, we investigated the effects of NB on chemosensitivity in the A549 human lung adenocarcinoma cell line and to elucidate therapeutic molecular target of NB. Methods: The chemosensitivity effects of NB in A549 cells were examined by MTT assay. The mechanism of NB action was evaluated using flow cytometry and Western blotting assays. Surface plasmon resonance (SPR) and LC-MS combined analysis (MS-SPRi) was performed to elucidate the candidate molecular target of NB. The chemosensitizing capacity of NB in vivo was assessed in nude mice bearing A549 tumors. Results: NB pretreatment sensitized A549 cells to low doxorubicin (DOX) dosage, leading to a 15.7% to 41.5% increase in apoptosis. This increase was correlated with ERK and AKT inactivation and activation of phospho-p38 MAPK, phospho-JNK, and phosphor-p53. Furthermore, this synergism depends on reactive oxygen species (ROS) generation. MS-SPRi analysis revealed that transient receptor potential melastatin-8 (TRPM8) is the candidate target of NB in potentiating DOX killing potency. Genetically, TRPM8 knock-down significantly suppresses the chemosensitizing effects of NB and inhibits ROS generation through restraining calcium mobilization. Moreover, pretreatment with NB synergistically enhances the anticancer effects of DOX to delay tumor progression in vivo. Conclusions: These results suggest that TRPM8 may be a valid therapeutic target in the potential application of NB, and show that NB is a chemosensitizer for lung cancer treatment.

Curcumin effect on cancer cells' multidrug resistance: An update

Chemotherapy is one of the main methods for cancer treatment. However, despite many advances in the design of anticancer drugs, their efficiency is limited due to their high toxicity and resistance of cells to chemotherapeutic drugs. In order to improve the cancer therapy, it is essential to use the compounds that can overcome drug resistance and increase treatment efficiency. Researchers have studied the effects of natural compounds for the controlling various drug resistance mechanisms. Curcumin is a natural phenolic compound which shows potent anticancer activities in different tumors, alone or as an adjuvant with other antitumor drugs to prevent or inhibit the survival and cancer progression by various mechanisms. The role of curcumin in overcoming drug resistance was followed by reviewing different applications of curcumin in cancer therapy. Afterward, the clinical impacts of curcumin, role of curcumin in decreasing drug resistance in different cancer cells and its mechanisms were discussed. It has been demonstrated that curcumin regulates signaling pathways in cancer cells, reduces the expression of proteins related to drug resistance, and increases the performance of antitumor drugs at various levels. Curcumin reverses multidrug resistance mechanisms and increases sensitivity of resistance cells to chemotherapy. This review mainly focuses on different mechanisms of drug resistance and curcumin as a nontoxic natural substance to eliminate the effects of drug resistance through modulation and controlling cell resistance pathways and eventually suggests curcumin as a potent chemosensitizer in cancers.

Breast Tumor Microenvironment: Emerging target of therapeutic phytochemicals

Triple negative breast cancer (TNBC) is the most aggressive and challenging form of breast cancers. Tumor microenvironment (TME) of TNBC is associated with induction of metastasis, immune system suppression, escaping immune detection and drug resistance. TME is highly complex and heterogeneous, consists of tumor cells, stromal cells and immune cells. The rapid expansion of tumors induce hypoxia, which concerns the reprogramming of TME components. The reciprocal communication of tumor cells and TME cells predisposes cancer cells to metastasis by modulation of developmental pathways, Wnt, notch, hedgehog and their related mechanisms in TME. Dietary phytochemicals are non-toxic and associated with various human health benefits and remarkable spectrum of biological activities. The phytochemicals serve as vital resources for drug discovery and also as a source for breast cancer therapy. The novel properties of dietary phytochemicals propose platform for modulation of tumor signaling, overcoming drug resistance, and targeting TME. Therefore, TME could serve as promising target for the treatment of TNBC. This review presents current status and implications of experimentally evaluated therapeutic phytochemicals as potential targeting agents of TME, potential nanosystems for targeted delivery of phytochemicals and their current challenges and future implications in TNBC treatment. The dietary phytochemicals especially curcumin with significant delivery system could prevent TNBC development as it is considered safe and well tolerated in phase II clinical trials.

Endoplasmic reticulum stress confers 5-fluorouracil resistance in breast cancer cell via the GRP78/OCT4/lncRNA MIAT/AKT pathway

5-Fluorouracil (5-FU) is an effective anticancer drug. However, high drug resistance limits its chemotherapeutic efficacy. Cancer cell resistance in colon cancer to 5-FU has been attributed to endoplasmic reticulum (ER) stress. But little is known about any similar role in resistance of breast cancer (BC). Here, we aim to investigate the role of ER stress played in BC cell resistance to 5-FU and to describe relevant molecular mechanisms. The expression patterns of 78-kDa glucose-regulated protein (GRP78), octamer 4 (OCT4), long non-coding RNA (lncRNA) myocardial infarction associated transcript (MIAT), and Protein kinase B (AKT) in BC MCF-7 cells resistant to 5-FU were determined by Western blot assay. Next, gain- and loss of-function experiments were conducted to verify effects of GRP78, OCT4, MIAT, and AKT on the to 5-FU sensitivity of MCF-7 cells and 5-FU resistant MCF cells (MCF-7/5-FU). Besides, the in vivo roles of the GRP78/OCT4/lncRNA MIAT/AKT pathway were assessed in tumor-bearing nude mice. 5-FU induced ER stress increased the expression of GRP78 in MCF-7 cells. GRP78 could positively regulate the expression of MIAT and AKT through upregulating OCT4, thereby contributing to 5-FU resistance in BC cells. Additionally, the function of GRP78 silencing in promoting tumor cell sensitivity was confirmed in vivo. These data supported an important role of the ER stress-mediated GRP78/OCT4/lncRNA MIAT/AKT pathway in BC cell resistance to 5-FU, highlighting potential molecular targets for combating 5-FU resistance in BC.

Alleviation of Multidrug Resistance by Flavonoid and Non-Flavonoid Compounds in Breast, Lung, Colorectal and Prostate Cancer

The aim of the manuscript is to discuss the influence of plant polyphenols in overcoming multidrug resistance in four types of solid cancers (breast, colorectal, lung and prostate cancer). Effective treatment requires the use of multiple toxic chemotherapeutic drugs with different properties and targets. However, a major cause of cancer treatment failure and metastasis is the development of multidrug resistance. Potential mechanisms of multidrug resistance include increase of drug efflux, drug inactivation, detoxification mechanisms, modification of drug target, inhibition of cell death, involvement of cancer stem cells, dysregulation of miRNAs activity, epigenetic variations, imbalance of DNA damage/repair processes, tumor heterogeneity, tumor microenvironment, epithelial to mesenchymal transition and modulation of reactive oxygen species. Taking into consideration that synthetic multidrug resistance agents have failed to demonstrate significant survival benefits in patients with different types of cancer, recent research have focused on beneficial effects of natural compounds. Several phenolic compounds (flavones, phenolcarboxylic acids, ellagitannins, stilbens, lignans, curcumin, etc.) act as chemopreventive agents due to their antioxidant capacity, inhibition of proliferation, survival, angiogenesis, and metastasis, modulation of immune and inflammatory responses or inactivation of pro-carcinogens. Moreover, preclinical and clinical studies revealed that these compounds prevent multidrug resistance in cancer by modulating different pathways. Additional research is needed regarding the role of phenolic compounds in the prevention of multidrug resistance in different types of cancer.

Phytofabrication of Nanoparticles as Novel Drugs for Anticancer Applications

Cancer is one of the foremost causes of death globally and also the major stumbling block of increasing life expectancy. Although the primary treatment of surgical resection, chemotherapy, and radiotherapy have greatly reduced the mortality of cancer, the survival rate is still low because of the metastasis of tumor, a range of adverse drug reactions, and drug resistance. For all this, it is relevant to mention that a growing amount of research has shown the anticarcinogenic effect of phytochemicals which can modulate the molecular pathways and cellular events include apoptosis, cell proliferation, migration, and invasion. However, their pharmacological potential is hindered by their low water solubility, low stability, poor absorption, and rapid metabolism. In this scenario, the development of nanotechnology has created novel formulations to maximize the potential use of phytochemicals in anticancer treatment. Nanocarriers can enhance the solubility and stability of phytochemicals, prolong their half-life in blood and even achieve site-targeting delivery. This review summarizes the advances in utilizing nanoparticles in cancer therapy. In particular, we introduce several applications of nanoparticles combined with apigenin, resveratrol, curcumin, epigallocatechin-3-gallate, 6-gingerol, and quercetin in cancer treatment.

BZD9L1 sirtuin inhibitor as a potential adjuvant for sensitization of colorectal cancer cells to 5-fluorouracil

Background:

This study aims to investigate the combination effect of a novel sirtuin inhibitor (BZD9L1) with 5-fluorouracil (5-FU) and to determine its molecular mechanism of action in colorectal cancer (CRC).

Methods:

BZD9L1 and 5-FU either as single treatment or in combination were tested against CRC cells to evaluate synergism in cytotoxicity, senescence and formation of micronucleus, cell cycle and apoptosis, as well as the regulation of related molecular players. The effects of combined treatments at different doses on stress and apoptosis, migration, invasion and cell death mechanism were evaluated through two-dimensional and three-dimensional cultures. In vivo studies include investigation on the combination effects of BZD9L1 and 5-FU on colorectal tumour xenograft growth and an evaluation of tumour proliferation and apoptosis using immunohistochemistry.

Results:

Combination treatments exerted synergistic reduction on cell viability on HCT 116 cells but not on HT-29 cells. Combined treatments reduced survival, induced cell cycle arrest, apoptosis, senescence and micronucleation in HCT 116 cells through modulation of multiple responsible molecular players and apoptosis pathways, with no effect in epithelial mesenchymal transition (EMT). Combination treatments regulated SIRT1 and SIRT2 protein expression levels differently and changed SIRT2 protein localization. Combined treatment reduced growth, migration, invasion and viability of HCT 116 spheroids through apoptosis, when compared with the single treatment. In addition, combined treatment was found to reduce tumour growth in vivo through reduction of tumour proliferation and necrosis compared with the vehicle control group. This highlights the potential therapeutic effects of BZD9L1 and 5-FU towards CRC.

Conclusion:

This study may pave the way for use of BZD9L1 as an adjuvant to 5-FU in improving the therapeutic efficacy for the treatment of colorectal cancer.

Zn(II)-curcumin solid dispersion impairs hepatocellular carcinoma growth and enhances chemotherapy by modulating gut microbiota-mediated zinc homeostasis

Zinc(II) complexes of curcumin display moderate cytotoxicity towards cancer cells at low micromolar concentrations. However, the clinical use of zinc(II) complexes is hampered by hydrolytic insolubility and poor bioavailability and their anticancer mechanisms remain unclear. Here, we investigated the efficacy and mechanism of action of a polyvinylpyrrolidone (PVP-k30)-based solid dispersion of Zn(II)-curcumin (ZnCM-SD) against hepatocellular carcinoma (HCC) in vitro and in vivo. In vitro assays revealed ZnCM-SD not only reduced the viability of HepG2 cells and SK-HEP1 cells in a dose-dependent manner, but also potently and synergistically enhanced cell growth inhibition and cell death in response to doxorubicin by regulating cellular zinc homeostasis. ZnCM-SD was internalized into the cells via non-specific endocytosis and degraded to release curcumin and Zn²⁺ ions within cells. The anticancer effects also occur in vivo in animals following the oral administration of ZnCM-SD, without significantly affecting the weight of the animals. Interestingly, ZnCM-SD did not reduce tumor growth or affect zinc homeostasis in HepG2-bearing mice after gut microbiome depletion. Moreover, administration of ZnCM-SD alone or in combination with doxorubicin significantly attenuated gut dysbiosis and zinc dyshomeostasis in a rat HCC model. Notably, fecal microbiota transplantation revealed the ability of ZnCM-SD to regulate zinc homeostasis and act as a chemosensitizer for doxorubicin were dependent on the gut microbiota. The crucial role of the gut microbiota in the chemosensitizing ability of ZnCM-SD was confirmed by broad-spectrum antibiotic treatment. Collectively, ZnCM-SD could represent a simple, well-tolerated, safe, effective therapy and function as a novel chemosensitizing agent for cancer.

Curcumin Combination Chemotherapy: The Implication and Efficacy in Cancer

Many chemotherapeutic drugs have been used for the treatment of cancer, for instance, doxorubicin, irinotecan, 5-fluorouracil, cisplatin, and paclitaxel. However, the effectiveness of chemotherapy is limited in cancer therapy due to drug resistance, therapeutic selectivity, and undesirable side effects. The combination of therapies with natural compounds is likely to increase the effectiveness of drug treatment as well as reduce the adverse outcomes. Curcumin, a polyphenolic isolated from Curcuma longa, belongs to the rhizome of Zingiberaceae plants. Studies from in vitro and in vivo revealed that curcumin exerts many pharmacological activities with less toxic effects. The biological mechanisms underlying the anticancer activity of co-treatment curcumin and chemotherapy are complex and worth to discuss further. Therefore, this review aimed to address the molecular mechanisms of combined curcumin and chemotherapy in the treatment of cancer. The anticancer activity of combined nanoformulation of curcumin and chemotherapy was also discussed in this study. Taken together, a better understanding of the implication and underlying mechanisms of action of combined curcumin and chemotherapy may provide a useful approach to combat cancer diseases.

Curcumin enhances cisplatin sensitivity by suppressing NADPH oxidase 5 expression in human epithelial cancer

Cisplatin-based chemotherapy regimens serve a pivotal role in human cancer treatment. Nevertheless, treatment failure may occur if the cancer is inherently resistant to cisplatin or acquires a resistant phenotype during the course of treatment. Although cisplatin resistance can hinder the efficacy of cisplatin treatment for human cancer, the underlying mechanism remains poorly understood. The current study established a cisplatin-resistant human epithelial cancer cell line. Notably, differential upregulation of NADPH oxidase 5 (NOX5) was identified in this resistant cell line. Furthermore, cisplatin treatment induced cancer cells to express NOX5 and cells that overexpressed NOX5 exhibited greater resistance to cisplatin via the activation of Akt. Treatment with curcumin may suppress NOX5 expression in cancer cells and enhance sensitivity to cisplatin treatment. In a xenograft model, a combined regimen of cisplatin with low-dose curcumin significantly reduced malignant tumor growth. These data demonstrate that curcumin has a chemosensitizing effect on cisplatin-resistant epithelial cancer types. Therefore, the use of curcumin in addition to a cisplatin-based treatment regimen may improve treatment outcomes in human patients with epithelial cancer.

Synergistic effect of kaempferol and 5‑fluorouracil on the growth of colorectal cancer cells by regulating the PI3K/Akt signaling pathway

Combination chemotherapy with chemosensitizers can exert synergistic therapeutic effects, reduce toxicity, and delay the induction of drug resistance. In the present study, the antitumor effects were investigated, and the possible underlying mechanisms of kaempferol combined with 5‑fluorouracil (5‑FU) in colorectal cancer cells were explored. HCT‑8 or HCT‑116 cells were treated with various concentrations of kaempferol and/or 5‑FU for the indicated time‑points. An MTT assay was used to determine cell viability, whereas the synergistic effects were assessed by calculating the combination indices of kaempferol and 5‑FU. Annexin V analysis and Hoechst staining were used to determine cell apoptosis. q‑PCR and western blotting were performed to determine the expression levels of Bax, Bcl‑2, thymidylate synthase (TS), PTEN, PI3K, AKT, and p‑AKT. The combination of kaempferol and 5‑FU was determined to be more effective in inhibiting cell viability than either of the agents alone. The inhibition of tumors in response to kaempferol and 5‑FU was associated with the reduction in proliferation ability and stimulation of apoptosis. The protein results indicated that kaempferol and 5‑FU could significantly upregulate the expression levels of Bax and downregulate the expression levels of Bcl‑2 and TS. Furthermore, the combination treatment greatly inhibited the activation of the PI3K/Akt pathway, suggesting the involvement of this pathway in the synergistic effects. The present study demonstrated that kaempferol has a synergistic effect with 5‑FU by inhibiting cell proliferation and inducing apoptosis in colorectal cancer cells via suppression of TS or attenuation of p‑Akt activation. The combination of kaempferol and 5‑FU may be used as an effective therapeutic strategy for colorectal cancer.

Combination of 5-fluorouracil and thymoquinone targets stem cell gene signature in colorectal cancer cells

Cancer stem cells (CSCs) residing in colorectal cancer tissues have tumorigenic capacity and contribute to chemotherapeutic resistance and disease relapse. It is well known that the survival of colorectal CSCs after 5-fluorouracil (5-FU)-based therapy leads to cancer recurrence. Thus CSCs represent a promising drug target. Here, we designed and synthesized novel hybrid molecules linking 5-FU with the plant-derived compound thymoquinone (TQ) and tested the potential of individual compounds and their combination to eliminate colorectal CSCs. Both, Combi and SARB hybrid showed augmented cytotoxicity against colorectal cancer cells, but were non-toxic to organoids prepared from healthy murine small intestine. NanoString analysis revealed a unique signature of deregulated gene expression in response to the combination of TQ and 5-FU (Combi) and SARB treatment. Importantly, two principle stem cell regulatory pathways WNT/ß-Catenin and PI3K/AKT were found to be downregulated after Combi and hybrid treatment. Furthermore, both treatments strikingly eliminated CD133+ CSC population, accompanying the depleted self-renewal capacity by eradicating long-term propagated 3D tumor cell spheres at sub-toxic doses. In vivo xenografts on chicken eggs of SARB-treated HCT116 cells showed a prominent nuclear ß-Catenin and E-cadherin staining. This was in line with the reduced transcriptional activity of ß-Catenin and diminished cell adhesion under SARB exposure. In contrast to 5-FU, both, Combi and SARB treatment effectively reduced the angiogenic capacity of the remaining resistant tumor cells. Taken together, combination or hybridization of single compounds target simultaneously a broader spectrum of oncogenic pathways leading to an effective eradication of colorectal cancer cells.

Synergistic delivery of 5-fluorouracil and curcumin using human serum albumin-coated iron oxide nanoparticles by folic acid targeting

Human serum albumin is the most abundant protein in plasma with the ability to bind to a variety of drug molecules. Magnetic nanoparticles are being extensively used in drug delivery due to its intrinsic magnetic properties. In this work, we have synthesized human serum albumin-coated citrate-functionalized iron oxide nanoparticles by CDI coupling. Furthermore, folic acid was decorated on human serum albumin by EDC and NHS coupling to confer targetability. Two cytotoxic drugs 5-fluorouracil (5FU) and curcumin were co-delivered. Wherein, the former is an anticancer agent and latter is a drug resistance depressor of former. The nanoparticles showed good aqueous dispersibility with a zeta potential of - 49.1 mV and magnetic core size in the range of 10-15 nm, thus exhibiting good magnetic property with magnetic saturation of 33.59 emu/g. Controlled drug release behavior was noticed in both drugs with faster release profile of 5FU. Nanoparticles also showed good cytotoxicity with lower IC50 values in the presence of magnetic field. The contrasting difference was noticed in folic acid-decorated and non-decorated composites, similarly in the presence of magnetic field where cell uptake was enhanced.

Curcumin as an anti-inflammatory agent: Implications to radiotherapy and chemotherapy

Cancer is the second cause of death worldwide. Chemotherapy and radiotherapy are the most common modalities for the treatment of cancer. Experimental studies have shown that inflammation plays a central role in tumor resistance and the incidence of several side effects following both chemotherapy and radiotherapy. Inflammation resulting from radiotherapy and chemotherapy is responsible for adverse events such as dermatitis, mucositis, pneumonitis, fibrosis, and bone marrow toxicity. Chronic inflammation may also lead to the development of second cancer during years after treatment. A number of anti-inflammatory drugs such as nonsteroidal anti-inflammatory agents have been proposed to alleviate chronic inflammatory reactions after radiotherapy or chemotherapy. Curcumin is a well-documented herbal anti-inflammatory agents. Studies have proposed that curcumin can help management of inflammation during and after radiotherapy and chemotherapy. Curcumin targets various inflammatory mediators such as cyclooxygenase-2, inducible nitric oxide synthase, and nuclear factor κB (NF-κB), thereby attenuating the release of proinflammatory and profibrotic cytokines, and suppressing chronic production of free radicals, which culminates in the amelioration of tissue toxicity. Through modulation of NF-κB and its downstream signaling cascade, curcumin can also reduce angiogenesis, tumor growth, and metastasis. Low toxicity of curcumin is linked to its cytoprotective effects in normal tissues. This protective action along with the capacity of this phytochemical to sensitize tumor cells to radiotherapy and chemotherapy makes it a potential candidate for use as an adjuvant in cancer therapy. There is also evidence from clinical trials suggesting the potential utility of curcumin for acute inflammatory reactions during radiotherapy such as dermatitis and mucositis.

The "Yin and Yang" of Natural Compounds in Anticancer Therapy of Triple-Negative Breast Cancers

Among the different types of breast cancers, triple-negative breast cancers (TNBCs) are highly aggressive, do not respond to conventional hormonal/human epidermal growth factor receptor 2 (HER2)-targeted interventions due to the lack of the respective receptor targets, have chances of early recurrence, metastasize, tend to be more invasive in nature, and develop drug resistance. The global burden of TNBCs is increasing regardless of the number of cytotoxic drugs being introduced into the market each year as they have only moderate efficacy and/or unforeseen side effects. Therefore, the demand for more efficient therapeutic interventions, with reduced side effects, for the treatment of TNBCs is rising. While some plant metabolites/derivatives actually induce the risk of cancers, many plant-derived active principles have gained attention as efficient anticancer agents against TNBCs, with fewer adverse side effects. Here we discuss the possible oncogenic molecular pathways in TNBCs and how the purified plant-derived natural compounds specifically target and modulate the genes and/or proteins involved in these aberrant pathways to exhibit their anticancer potential. We have linked the anticancer potential of plant-derived natural compounds (luteolin, chalcones, piperine, deguelin, quercetin, rutin, fisetin, curcumin, resveratrol, and others) to their ability to target multiple dysregulated signaling pathways (such as the Wnt/β-catenin, Notch, NF-κB, PI3K/Akt/mammalian target of rapamycin (mTOR), mitogen-activated protein kinase (MAPK) and Hedgehog) leading to suppression of cell growth, proliferation, migration, inflammation, angiogenesis, epithelial-mesenchymal transition (EMT) and metastasis, and activation of apoptosis in TNBCs. Plant-derived compounds in combination with classical chemotherapeutic agents were more efficient in the treatment of TNBCs, possibly with lesser side effects.

Wheat germ agglutinin modified magnetic iron oxide nanocomplex as a cell membrane specific receptor target material for killing breast cancer cells

Lectins are known for their specificity for carbohydrate binding. However, a few specific carbohydrate residues are over expressed in cancer cells, which may be an advantage for using a lectin that is specific to such residues. Herein, we report the strategic design of wheat germ agglutinin (WGA) and a fluorescent torch, FITC immobilized on Fe₃O₄ NPs as a cell membrane specific receptor target for breast cancer cells, viz., MCF-7 and MDA-MB-231. The resultant nanocomplexes were well characterized by using microscopy and spectroscopy. The WGA tagged nanocomplex was further loaded with the anticancer drug 5-fluorouracil (5-FU) to selectively kill the cancer cells. The loading efficiency of 5-FU is ∼356 μg mg^-1. The nanocomplex itself shows ∼90% cell viability for all the four cell lines (HEK, HeLa, MCF-7 and MDA-MB-231) studied and is therefore a suitable targeting drug delivery vehicle. However, the nanocomplex loaded with {WGA + 5-FU} shows a ∼1.5-fold decrease in cell viability in the case of specific cells (MCF-7 and MDA-MB-231) when compared to non-specific cells (HeLa and HEK). The internalization of the nanocomplex is supported by fluorescence microscopy and confocal laser scanning microscopy techniques by tracking with the fluorescent torch, FITC. The nanocomplex can be internalized ∼2 times more in the specific cells as compared to the non-specific cells. It is observed that the internalization is ∼2 fold increased when the MDA-MB-231 cells are exposed to a magnetic field for 24 h as compared to in the absence of a magnetic field. Live-dead cell assay of the 5-FU loaded nanocomplex was done by propidium iodide (PI) staining. There is an increase in the cell death by ∼2.5 fold when the cells are under a magnetic field as measured from the PI uptake. Such strategic designing of the nanocomplex can lead to the development of a better method to selectively target and kill the cancer cells by acting as a carrier to deliver a suitable drug, as a result of which the medical field can benefit.

Mechanistic evaluation of phytochemicals in breast cancer remedy: current understanding and future perspectives

Breast cancer is one of the most commonly diagnosed cancers around the globe and accounts for a large proportion of fatalities in women. Despite the advancement in therapeutic and diagnostic procedures, breast cancer still represents a major challenge. Current anti-breast cancer approaches include surgical removal, radiotherapy, hormonal therapy and the use of various chemotherapeutic drugs. However, drug resistance, associated serious adverse effects, metastasis and recurrence complications still need to be resolved which demand safe and alternative strategies. In this scenario, phytochemicals have recently gained huge attention due to their safety profile and cost-effectiveness. These phytochemicals modulate various genes, gene products and signalling pathways, thereby inhibiting breast cancer cell proliferation, invasion, angiogenesis and metastasis and inducing apoptosis. Moreover, they also target breast cancer stem cells and overcome drug resistance problems in breast carcinomas. Phytochemicals as adjuvants with chemotherapeutic drugs have greatly enhanced their therapeutic efficacy. This review focuses on the recently recognized molecular mechanisms underlying breast cancer chemoprevention with the use of phytochemicals such as curcumin, resveratrol, silibinin, genistein, epigallocatechin gallate, secoisolariciresinol, thymoquinone, kaempferol, quercetin, parthenolide, sulforaphane, ginsenosides, naringenin, isoliquiritigenin, luteolin, benzyl isothiocyanate, α-mangostin, 3,3'-diindolylmethane, pterostilbene, vinca alkaloids and apigenin.

mTORC1/2 inhibitor and curcumin induce apoptosis through lysosomal membrane permeabilization-mediated autophagy

mTOR is an important regulator of cell growth and forms two complexes, mTORC1/2. In cancer, mTOR signaling is highly activated, and the regulation of this signaling, as an anti-cancer strategy, has been emphasized. However, PP242 (inhibitor of mTORC1 and mTORC2) alone did not induce human renal carcinoma cell death. In this study, we found that PP242 alone did not alter cell viability, but combined curcumin and PP242 treatment induced cell death. Combined PP242 and curcumin treatment induced Bax activation and decreased expression of Mcl-1 and Bcl-2. Furthermore, co-treatment with PP242 and curcumin-induced the downregulation of the Rictor (an mTORC2 complex protein) and Akt protein levels, and ectopic overexpression of Rictor or Akt inhibited PP242 plus curcumin induced cell death. Downregulation of Rictor increased cytosolic Ca²⁺ release from endoplasmic reticulum, which led to lysosomal damage in PP242 plus curcumin-treated cells. Furthermore, damaged lysosomes induced autophagy. Autophagy inhibitors markedly inhibited cell death. Finally, combined curcumin and PP242 treatment reduced tumor growth and induced cell death in xenograft models. Altogether, our results reveal that combined PP242 and curcumin treatment could induce autophagy-mediated cell death by reducing the expression of Rictor and Akt in renal carcinoma cells.

PSMD4 is a novel therapeutic target in chemoresistant colorectal cancer activated by cytoplasmic localization of Nrf2

Nuclear Nrf2 (nNrf2) binding to the antioxidant response element may promote chemoresistance in colorectal cancer. However, the shuttling of Nrf2 between cytoplasm and nucleus in colon cancer cells has revealed the possibility that cytoplasmic location of Nrf2 (cNrf2) may play a specific role in chemoresistance. Transfection of a nuclear location sequence (NLS)-wild-type or NLS-mutated Nrf2 expression vector into a stable shNrf2 HCT116 clone using the MTT assay to examine whether chemoresistance induced by cNrf2 may be greater than nNrf2. Different specific inhibitors and small hairpin (sh)RNAs of targeting genes were used to verify the mechanistic action of cNrf2 in chemoresistance and further confirmed by an animal model. The association of cNrf2 with chemotherapeutic response in patients with colorectal cancer was statistically analyzed. The MTT assay indicated that cNrf2 may play a more important role than nNrf2 in conferring 5-fluorouracil (5-FU) and oxaliplatin resistance in HCT116 cells. Mechanistically, cNrf2-induced PSMD4 expression was responsible for chemoresistance in the NLS-mutated Nrf2-tranfected shNrf2HCT116 clone via the NF-κB/AKT/β-catenin/ZEB1 cascades. The tumor burden induced by the NLS-mutated Nrf2-transfected shNrf2HCT116 clone was completely suppressed by treatment with 5-FU in combination with carfilzomib. A higher prevalence of unfavorable chemotherapeutic response in colorectal cancer patients with cNrf2, PSMD4-positive, p-p65-positive, and nuclear β-catenin tumors was observed when compared to their counterparts. cNrf2 may play a more important role than nNrf2 in the chemoresistance of colorectal cancer. Activation of the NF-κB/AKT/β-catenin/ZEB1 cascade by PSMD4 may be responsible for cNrf2-mediated chemoresistance.

CONDENSED ABSTRACT

CNrf2 may play a more important role than nNrf2 in conferring 5-FU and oxaliplatin resistance. This observation in patients seemed to support the findings of the cell and animal models and suggested that PSMD4 may be responsible cNrf2-mediated chemoresistance via the NF-κB/AKT/β-catenin /ZEB1 cascades.