Flavonoids are polyphenols that are found in numerous edible plant species. Data obtained from preclinical and clinical
studies suggest that specific flavonoids are chemo-preventive and cytotoxic ...against various cancers via a multitude
of mechanisms. However, the clinical use of flavonoids is limited due to challenges associated with their effective
use, including (1) the isolation and purification of flavonoids from their natural resources; (2) demonstration of the
effects of flavonoids in reducing the risk of certain cancer, in tandem with the cost and time needed for epidemiological
studies, and (3) numerous pharmacokinetic challenges (e.g., bioavailability, drug–drug interactions, and metabolic
instability). Currently, numerous approaches are being used to surmount some of these challenges, thereby increasing
the likelihood of flavonoids being used as chemo-preventive drugs in the clinic. In this review, we summarize the
most important challenges and efforts that are being made to surmount these challenges.
Abstract ATP-binding cassette (ABC) transporters represent one of the largest and oldest families of membrane proteins in all extant phyla from prokaryotes to humans, which couple the energy derived ...from ATP hydrolysis essentially to translocate, among various substrates, toxic compounds across the membrane. The fundamental functions of these multiple transporter proteins include: (1) conserved mechanisms related to nutrition and pathogenesis in bacteria, (2) spore formation in fungi, and (3) signal transduction, protein secretion and antigen presentation in eukaryotes. Moreover, one of the major causes of multidrug resistance (MDR) and chemotherapeutic failure in cancer therapy is believed to be the ABC transporter-mediated active efflux of a multitude of structurally and mechanistically distinct cytotoxic compounds across membranes. It has been postulated that ABC transporter inhibitors known as chemosensitizers may be used in combination with standard chemotherapeutic agents to enhance their therapeutic efficacy. The current paper reviews the advance in the past decade in this important domain of cancer chemoresistance and summarizes the development of new compounds and the re-evaluation of compounds originally designed for other targets as transport inhibitors of ATP-dependent drug efflux pumps.
The successful treatment of cancer has significantly improved as a result of targeted therapy and immunotherapy. However, during chemotherapy, cancer cells evolve and can acquire “multidrug ...resistance” (MDR), which significantly limits the efficacy of cancer treatment and impacts patient survival and quality of life. Among the approaches to reverse MDR, modulating reactive oxidative species (ROS) may represent a strategy to kill MDR cancer cells that are mechanistically diverse. ROS in cancer cells play a central role in regulating and inducing apoptosis, thereby modulating cancer cells proliferation, survival and drug resistance. The levels of ROS and the activity of scavenging/anti-oxidant enzymes in drug resistant cancer cells are typically increased compared to non-MDR cancer and normal cells. Consequently, MDR cancer cells may be more susceptible to alterations in ROS levels. Numerous studies suggest that compounds modulating cellular ROS levels can enhance MDR cancer cell death and sensitize MDR cancer cells to certain chemotherapeutic drugs.
In the current review, we discuss the critical and targetable redox-regulating enzymes, including mitochondrial electron transport chain (ETC) complexes, NADPH oxidases (NOXs), enzymes related to glutathione metabolism, glutamate/cystine antiporter xCT, thioredoxin reductases (TrxRs), nuclear factor erythroid 2-related factor 2 (Nrf2), and their roles in regulating cellular ROS levels, drug resistance as well as their clinical significance. We also discuss and summarize the findings in the past decade regarding the efficacy of ROS modulators for the treatment of MDR cancer alone or as sensitizing compounds. Compounds that are efficacious in modulating ROS generation represent a prominent class of drug candidates that warrants evaluation in clinical trials for patients harboring MDR cancers.
Multidrug resistance (MDR) remains one of the major impediments for efficacious cancer chemotherapy. Increased efflux of multiple chemotherapeutic drugs by transmembrane ATP‐binding cassette (ABC) ...transporter superfamily is considered one of the primary causes for cancer MDR, in which the role of P‐glycoprotein (P‐gp/ABCB1) has been most well‐established. The clinical co‐administration of P‐gp drug efflux inhibitors, in combination with anticancer drugs which are P‐gp transport substrates, was considered to be a treatment modality to surmount MDR in anticancer therapy by blocking P‐gp‐mediated multidrug efflux. Extensive attempts have been carried out to screen for sets of nontoxic, selective, and efficacious P‐gp efflux inhibitors. In this review, we highlight the recent achievements in drug design, characterization, structure–activity relationship (SAR) studies, and mechanisms of action of the newly synthetic, potent small molecules P‐gp inhibitors in the past 5 years. The development of P‐gp inhibitors will increase our knowledge of the mechanisms and functions of P‐gp‐mediated drug efflux which will benefit drug discovery and clinical cancer therapeutics where P‐gp transporter overexpression has been implicated in MDR.
Display omitted
Drug resistance is a major obstacle in the field of pre-clinical and clinical therapeutics. The development of novel technologies and targeted therapies have yielded new modalities to ...overcome drug resistance, but multidrug resistance (MDR) remains one of the major challenges in the treatment of cancer. The ubiquitin-proteasome system (UPS) has a central role in regulating the levels and activities of a multitude of proteins as well as regulation of cell cycle, gene expression, response to oxidative stress, cell survival, cell proliferation and apoptosis. Therefore, inhibition of the UPS could represent a novel strategy for the treatment and overcoming of drug resistance in chemoresistant malignancies. In 2003, bortezomib was approved by the FDA for the treatment of multiple myeloma (MM). However, due to its limitations, second generation proteasome inhibitors (PIs) like carfilzomib, ixazomib, oprozomib, delanzomib and marizomib were introduced which displayed clinical activity in bortezomib-resistant tumors. Past studies have demonstrated that proteasome inhibition potentiates the anti-cancer efficacy of other chemotherapeutic drugs by: i) decreasing the expression of anti-apoptotic proteins such as TNF-α and NF-kB, ii) increasing the levels of Noxa, a pro-apoptotic protein, iii) activating caspases and inducing apoptosis, iv) degrading the pro-survival protein, induced myeloid leukemia cell differentiation protein (MCL1), and v) inhibiting drug efflux transporters. In addition, the mechanism of action of the immunoproteasome inhibitors, ONX-0914 and LU-102, suggested their therapeutic role in the combination treatment with PIs. In the current review, we discuss various PIs and their underlying mechanisms in surmounting anti-tumor drug resistance when used in combination with conventional chemotherapeutic agents.
Chemoresistance, whether intrinsic or acquired, is a major obstacle in the treatment of cancer. The resistance of cancer cells to chemotherapeutic drugs can result from various mechanisms. Over the ...last decade, it has been reported that 1ong noncoding RNAs (lncRNAs) can mediate carcinogenesis and drug resistance/sensitivity in cancer cells. This article reviews, in detail, recent studies regarding the roles of lncRNAs in mediating drug resistance.
Curcumin (1E,6E)‑1,7‑bis(4‑hydroxy‑3‑-methoxyphenyl) hepta‑1,6‑diene‑3,5‑dione is a natural polyphenol that is derived from the turmeric plant (curcuma longa L.). Curcumin is widely used in food ...coloring, preservatives, and condiments. Curcumin possesses anti‑tumor, anti‑oxidative and anti‑inflammatory efficacy, as well as other pharmacological effects. Emerging evidence indicates that curcumin alters microRNAs (miRNAs) and long non‑coding RNAs (lncRNAs) in various types of cancers. Both miRNAs and lncRNAs are non‑coding RNAs that can epigenetically modulate the expression of multiple genes via post‑transcriptional regulation. In the present review, the interactions between curcumin and non‑coding RNAs are summarized in numerous types of cancers, including lung, colorectal, prostate, breast, nasopharyngeal, pancreatic, blood, and ovarian cancer, and the vital non‑coding RNAs and their downstream targets are described.
Cuproptosis, a newly identified form of regulated cell death that is copper‐dependent, offers great opportunities for exploring the use of copper‐based nanomaterials inducing cuproptosis for cancer ...treatment. Here, a glucose oxidase (GOx)‐engineered nonporous copper(I) 1,2,4‐triazolate (Cu(tz)) coordination polymer (CP) nanoplatform, denoted as GOx@Cu(tz), for starvation‐augmented cuproptosis and photodynamic synergistic therapy is developed. Importantly, the catalytic activity of GOx is shielded in the nonporous scaffold but can be “turned on” for efficient glucose depletion only upon glutathione (GSH) stimulation in cancer cells, thereby proceeding cancer starvation therapy. The depletion of glucose and GSH sensitizes cancer cells to the GOx@Cu(tz)‐mediated cuproptosis, producing aggregation of lipoylated mitochondrial proteins, the target of copper‐induced toxicity. The increased intracellular hydrogen peroxide (H2O2) levels, due to the oxidation of glucose, activates the type I photodynamic therapy (PDT) efficacy of GOx@Cu(tz). The in vivo experimental results indicate that GOx@Cu(tz) produces negligible systemic toxicity and inhibits tumor growth by 92.4% in athymic mice bearing 5637 bladder tumors. This is thought to be the first report of a cupreous nanomaterial capable of inducing cuproptosis and cuproptosis‐based synergistic therapy in bladder cancer, which should invigorate studies pursuing rational design of efficacious cancer therapy strategies based on cuproptosis.
An enzyme‐engineered cupreous nanomaterial capable of inducing cuproptosis and cuproptosis‐based synergistic therapy in cancer cells is reported, which may invigorate studies pursuing rational design of effective cancer therapy strategies based on cuproptosis.
Display omitted
•Resistance to Taxanesoccurs at molecular and genetic levels.•Taxanes inhibit tubulin depolymerization•Nanocarriers and RNAi techniques decrease the magnitude of resistance to ...Taxanes.•Secondary metabolites reverse drug resistance by targeting P-gp, β-tubulin and the Akt/NF-κB pathways.
One of the primary causes of attenuated or loss of efficacy of cancer chemotherapy is the emergence of multidrug resistance (MDR). Numerous studies have been published regarding potential approaches to reverse resistance to taxanes, including paclitaxel (PTX) and docetaxel, which represent one of the most important classes of anticancer drugs. Since 1984, following the FDA approval of paclitaxel for the treatment of advanced ovarian carcinoma, taxanes have been extensively used as drugs that target tumor microtubules. Taxanes, have been shown to affect an array of oncogenic signaling pathways and have potent cytotoxic efficacy. However, the clinical success of these drugs has been restricted by the emergence of cancer cell resistance, primarily caused by the overexpression of MDR efflux transporters or by microtubule alterations. In vitro and in vivo studies indicate that the mechanisms underlying the resistance to PTX and docetaxel are primarily due to alterations in α-tubulin and β-tubulin. Moreover, resistance to PTX and docetaxel results from: 1) alterations in microtubule-protein interactions, including microtubule-associated protein 4, stathmin, centriole, cilia, spindle-associated protein, and kinesins; 2) alterations in the expression and activity of multidrug efflux transporters of the ABC superfamily including P-glycoprotein (P-gp/ABCB1); 3) overexpression of anti-apoptotic proteins or inhibition of apoptotic proteins and tumor-suppressor proteins, as well as 4) modulation of signal transduction pathways associated with the activity of several cytokines, chemokines and transcription factors.
In this review, we discuss the abovementioned molecular mechanisms and their role in mediating cancer chemoresistance to PTX and docetaxel. We provide a detailed analysis of both in vitro and in vivo experimental data and describe the application of these findings to therapeutic practice. The current review also discusses the efficacy of different pharmacological modulations to achieve reversal of PTX resistance. The therapeutic roles of several novel compounds, as well as herbal formulations, are also discussed. Among them, many structural derivatives had efficacy against the MDR phenotype by either suppressing MDR or increasing the cytotoxic efficacy compared to the parental drugs, or both. Natural products functioning as MDR chemosensitizers offer novel treatment strategies in patients with chemoresistant cancers by attenuating MDR and increasing chemotherapy efficacy. We broadly discuss the roles of inhibitors of P-gp and other efflux pumps, in the reversal of PTX and docetaxel resistance in cancer cells and the significance of using a nanomedicine delivery system in this context. Thus, a better understanding of the molecular mechanisms mediating the reversal of drug resistance, combined with drug efficacy and the application of target-based inhibition or specific drug delivery, could signal a new era in modern medicine that would limit the pathological consequences of MDR in cancer patients.
The adenosine tri-phosphate binding cassette (ABC) transporters are one of the largest transmembrane gene families in humans. The ABC transporters are present in a number of tissues, providing ...protection against xenobiotics and certain endogenous molecules. Unfortunately, their presence produces suboptimal chemotherapeutic outcomes in cancer patient tumor cells. It is well established that they actively efflux antineoplastic agents from cancer cells, producing the multidrug resistance (MDR) phenotype. The inadequate response to chemotherapy and subsequent poor prognosis in cancer patients can be in part the result of the clinical overexpression of ABC transporters. In fact, one of the targeted approaches for overcoming MDR in cancer cells is that directed towards blocking or inhibiting ABC transporters. Indeed, for almost three decades, research has been conducted to overcome MDR through pharmacological inhibition of ABC transporters with limited clinical success. Therefore, contemporary strategies to identify or to synthesize selective "resensitizers" of ABC transporters with limited nonspecific toxicity have been undertaken. Innovative approaches en route to understanding specific biochemical role of ABC transporters in MDR and tumorigenesis will prove essential to direct our knowledge towards more effective targeted therapies. This review briefly discusses the current knowledge regarding the clinical involvement of ABC transporters in MDR to antineoplastic drugs and highlights approaches undertaken so far to overcome ABC transporter-mediated MDR in cancer.
PDF
