Improving cancer chemotherapy with modulators of ABC drug transporters

Deciphering the Molecular Mechanisms behind Drug Resistance in Ovarian Cancer to Unlock Efficient Treatment Options

Ovarian cancer is a highly lethal form of gynecological cancer. This disease often goes undetected until advanced stages, resulting in high morbidity and mortality rates. Unfortunately, many patients experience relapse and succumb to the disease due to the emergence of drug resistance that significantly limits the effectiveness of currently available oncological treatments. Here, we discuss the molecular mechanisms responsible for resistance to carboplatin, paclitaxel, polyadenosine diphosphate ribose polymerase inhibitors, and bevacizumab in ovarian cancer. We present a detailed analysis of the most extensively investigated resistance mechanisms, including drug inactivation, drug target alterations, enhanced drug efflux pumps, increased DNA damage repair capacity, and reduced drug absorption/accumulation. The in-depth understanding of the molecular mechanisms associated with drug resistance is crucial to unveil new biomarkers capable of predicting and monitoring the kinetics during disease progression and discovering new therapeutic targets.

Overcoming multi drug resistance mediated by ABC transporters by a novel acetogenin- annonacin from Annona muricata L

ETHNOPHARMACOLOGICAL RELEVANCE

Multi-Drug Resistance (MDR), mediated by P-glycoprotein (P-gp) is one of the barriers to successful chemotherapy in colon cancer patients. Annona muricata L. (A.muricata), commonly known as soursop/Graviola, is a medicinal plant that has been traditionally used in treating diverse diseases including cancer. Phytochemicals of A.muricata (Annonaceous Acetogenins-AGEs) have been well-reported for their anti-cancer effects on various cancers.

AIM OF THE STUDY

The study aimed to examine the effect of AGEs in reversing MDR in colorectal cancer cells.

METHODS

Based on molecular docking and molecular dynamic simulation, the stability of annonacin upon P-gp was investigated. Further in vitro studies were carried in oxaliplatin-resistant human colon cancer cells (SW480R) to study the biological effect of annonacin, in reversing drug resistance in these cells.

RESULTS

Molecular docking and simulation studies have indicated that annonacin stably interacted at the drug binding site of P-gp. In vitro analysis showed that annonacin was able to significantly reduce the expression of P-gp by 2.56 folds. It also induced apoptosis in the drug-resistant colon cancer cells. Moreover, the intracellular accumulation of P-gp substrate (calcein-AM) was observed to increase in resistant cells upon treatment with annonacin.

CONCLUSION

Our findings suggest that annonacin could inhibit the efflux of chemotherapeutic drugs mediated by P-gp and thereby help in reversing MDR in colon cancer cells. Further in vivo studies are required to decipher the underlying mechanism of annonacin in treating MDR cancers.

ALDH1A3 promotes invasion and metastasis in triple-negative breast cancer by regulating the plasminogen activation pathway

Aldehyde dehydrogenase 1A3 (ALDH1A3) is a cancer stem cell marker that promotes metastasis. Triple-negative breast cancer (TNBC) progression has been linked to ALDH1A3-induced gene expression changes. To investigate the mechanism of ALDH1A3-mediated breast cancer metastasis, we assessed the effect of ALDH1A3 on the expression of proteases and the regulators of proteases that degrade the extracellular matrix, a process that is essential for invasion and metastasis. This revealed that ALDH1A3 regulates the plasminogen activation pathway; it increased the levels and activity of tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA). This resulted in a corresponding increase in the activity of serine protease plasmin, the enzymatic product of tPA and uPA. The ALDH1A3 product all-trans-retinoic acid similarly increased tPA and plasmin activity. The increased invasion of TNBC cells by ALDH1A3 was plasminogen-dependent. In patient tumours, ALDH1A3 and tPA are co-expressed and their combined expression correlated with the TNBC subtype, high tumour grade and recurrent metastatic disease. Knockdown of tPA in TNBC cells inhibited plasmin generation and lymph node metastasis. These results identify the ALDH1A3-tPA-plasmin axis as a key contributor to breast cancer progression.

TICBase: Integrated Resource for Data on Drug and Environmental Chemical Interactions with Mammalian Drug Transporters

Environmental health science seeks to predict how environmental toxins, chemical toxicants, and prescription drugs accumulate and interact within the body. Xenobiotic transporters of the ATP-binding cassette (ABC) and solute carrier (SLC) superfamilies are major determinants of the uptake and disposition of xenobiotics across the kingdoms of life. The goal of this study was to integrate drug and environmental chemical interactions of mammalian ABC and SLC proteins in a centralized, integrative database. We built upon an existing publicly accessible platform-the "TransPortal"-which was updated with novel data and searchable features on transporter-interfering chemicals from manually curated literature data. The integrated resource TransPortal-TICBase (https://transportal.compbio.ucsf.edu) now contains information on 46 different mammalian xenobiotic transporters of the ABC- and SLC-type superfamilies, including 13 newly added rodent and 2 additional human drug transporters, 126 clinical drug-drug interactions, and a more than quadrupled expansion of the initial in vitro chemical interaction data from 1,402 to 6,296 total interactions. Based on our updated database, environmental interference with major human and rodent drug transporters occurs across the ABC- and SLC-type superfamilies, with kinetics indicating that some chemicals, such as the ionic liquid 1-hexylpyridinium chloride and the antiseptic chlorhexidine, can act as strong inhibitors with potencies similar or even higher than pharmacological model inhibitors. The new integrated web portal serves as a central repository of current and emerging data for interactions of prescription drugs and environmental chemicals with human drug transporters. This archive has important implications for predicting adverse drug-drug and drug-environmental chemical interactions and can serve as a reference website for the broader scientific community of clinicians and researchers.

Advances in the structure, mechanism and targeting of chemoresistance-linked ABC transporters

Cancer cells frequently display intrinsic or acquired resistance to chemically diverse anticancer drugs, limiting therapeutic success. Among the main mechanisms of this multidrug resistance is the overexpression of ATP-binding cassette (ABC) transporters that mediate drug efflux, and, specifically, ABCB1, ABCG2 and ABCC1 are known to cause cancer chemoresistance. High-resolution structures, biophysical and in silico studies have led to tremendous progress in understanding the mechanism of drug transport by these ABC transporters, and several promising therapies, including irradiation-based immune and thermal therapies, and nanomedicine have been used to overcome ABC transporter-mediated cancer chemoresistance. In this Review, we highlight the progress achieved in the past 5 years on the three transporters, ABCB1, ABCG2 and ABCC1, that are known to be of clinical importance. We address the molecular basis of their broad substrate specificity gleaned from structural information and discuss novel approaches to block the function of ABC transporters. Furthermore, genetic modification of ABC transporters by CRISPR-Cas9 and approaches to re-engineer amino acid sequences to change the direction of transport from efflux to import are briefly discussed. We suggest that current information regarding the structure, mechanism and regulation of ABC transporters should be used in clinical trials to improve the efficiency of chemotherapeutics for patients with cancer.

Regression of ovarian cancer xenografts by depleting or inhibiting RLIP

Ovarian cancer (OC) is the most prevalent and deadly cancer of the female reproductive system. Women will continue to be impacted by OC-related morbidity and mortality. Despite the fact that chemotherapy with cisplatin is the main component as the first-line anticancer treatment for OC, chemoresistance and unfavorable side effects are important obstacles to effective treatment. Targets for effective cancer therapy are required for cancer cells but not for non-malignant cells because they are expressed differently in cancer cells compared to normal cells. Targets for cancer therapy should preferably be components that already exist in biochemical and signalling frameworks and that significantly contribute to the development of cancer or regulate the response to therapy. RLIP is an important mercapturic acid pathway transporter that is crucial for survival and therapy resistance in cancers, therefore, we examined the role of RLIP in regulating essential signalling proteins involved in relaying the inputs from upstream survival pathways and mechanisms contributing to chemo-radiotherapy resistance in OC. The findings of our research offer insight into a novel anticancer effect of RLIP depletion/inhibition on OC and might open up new therapeutic avenues for OC therapy.

Identification of NanoLuciferase Substrates Transported by Human ABCB1 and ABCG2 and their Zebrafish Homologs at the Blood-Brain Barrier

ATP-binding cassette (ABC) transporters expressed at the blood-brain barrier (BBB) impede delivery of therapeutic agents to the brain, including agents to treat neurodegenerative diseases and primary and metastatic brain cancers. Two transporters, P-glycoprotein (P-gp, ABCB1) and ABCG2, are highly expressed at the BBB and are responsible for the efflux of numerous clinically useful chemotherapeutic agents, including irinotecan, paclitaxel, and doxorubicin. Based on a previous mouse model, we have generated transgenic zebrafish in which expression of NanoLuciferase (NanoLuc) is controlled by the promoter of glial fibrillary acidic protein, leading to expression in zebrafish glia. To identify agents that disrupt the BBB, including inhibitors of ABCB1 and ABCG2, we identified NanoLuc substrates that are also transported by P-gp, ABCG2, and their zebrafish homologs. These substrates will elevate the amount of bioluminescent light produced in the transgenic zebrafish with BBB disruption. We transfected HEK293 cells with NanoLuc and either human ABCB1, ABCG2, or their zebrafish homologs Abcb4 or Abcg2a, respectively, and expressed at the zebrafish BBB. We evaluated the luminescence of ten NanoLuc substrates, then screened the eight brightest to determine which are most efficiently effluxed by the ABC transporters. We identified one substrate efficiently pumped out by ABCB1, two by Abcb4, six by ABCG2, and four by Abcg2a. These data will aid in the development of a transgenic zebrafish model of the BBB to identify novel BBB disruptors and should prove useful in the development of other animal models that use NanoLuc as a reporter.

Multi-Anticancer Activities of Phytoestrogens in Human Osteosarcoma

Phytoestrogens are plant-derived bioactive compounds with estrogen-like properties. Their potential health benefits, especially in cancer prevention and treatment, have been a subject of considerable research in the past decade. Phytoestrogens exert their effects, at least in part, through interactions with estrogen receptors (ERs), mimicking or inhibiting the actions of natural estrogens. Recently, there has been growing interest in exploring the impact of phytoestrogens on osteosarcoma (OS), a type of bone malignancy that primarily affects children and young adults and is currently presenting limited treatment options. Considering the critical role of the estrogen/ERs axis in bone development and growth, the modulation of ERs has emerged as a highly promising approach in the treatment of OS. This review provides an extensive overview of current literature on the effects of phytoestrogens on human OS models. It delves into the multiple mechanisms through which these molecules regulate the cell cycle, apoptosis, and key pathways implicated in the growth and progression of OS, including ER signaling. Moreover, potential interactions between phytoestrogens and conventional chemotherapy agents commonly used in OS treatment will be examined. Understanding the impact of these compounds in OS holds great promise for developing novel therapeutic approaches that can augment current OS treatment modalities.

Extracellular Vesicles and Cancer Multidrug Resistance: Undesirable Intercellular Messengers?

Cancer multidrug resistance (MDR) is one of the main mechanisms contributing to therapy failure and mortality. Overexpression of drug transporters of the ABC family (ATP-binding cassette) is a major cause of MDR. Extracellular vesicles (EVs) are nanoparticles released by most cells of the organism involved in cell-cell communication. Their cargo mainly comprises, proteins, nucleic acids, and lipids, which are transferred from a donor cell to a target cell and lead to phenotypical changes. In this article, we review the scientific evidence addressing the regulation of ABC transporters by EV-mediated cell-cell communication. MDR transfer from drug-resistant to drug-sensitive cells has been identified in several tumor entities. This was attributed, in some cases, to the direct shuttle of transporter molecules or its coding mRNA between cells. Also, EV-mediated transport of regulatory proteins (e.g., transcription factors) and noncoding RNAs have been indicated to induce MDR. Conversely, the transfer of a drug-sensitive phenotype via EVs has also been reported. Additionally, interactions between non-tumor cells and the tumor cells with an impact on MDR are presented. Finally, we highlight uninvestigated aspects and possible approaches to exploiting this knowledge toward the identification of druggable processes and molecules and, ultimately, the development of novel therapeutic strategies.

ABCB1 and ABCG2 Overexpression Mediates Resistance to the Phosphatidylinositol 3-Kinase Inhibitor HS-173 in Cancer Cell Lines

Constitutive activation of the phosphoinositide-3-kinase (PI3K)/Akt signaling pathway is crucial for tumor growth and progression. As such, this pathway has been an enticing target for drug discovery. Although HS-173 is a potent PI3K inhibitor that halts cancer cell proliferation via G2/M cell cycle arrest, the resistance mechanisms to HS-173 have not been investigated. In this study, we investigated the susceptibility of HS-173 to efflux mediated by the multidrug efflux transporters ABCB1 and ABCG2, which are two of the most well-known ATP-binding cassette (ABC) transporters associated with the development of cancer multidrug resistance (MDR). We found that the overexpression of ABCB1 or ABCG2 significantly reduced the efficacy of HS-173 in human cancer cells. Our data show that the intracellular accumulation of HS-173 was substantially reduced by ABCB1 and ABCG2, affecting G2/M arrest and apoptosis induced by HS-173. More importantly, the efficacy of HS-173 in multidrug-resistant cancer cells could be recovered by inhibiting the drug-efflux function of ABCB1 and ABCG2. Taken together, our study has demonstrated that HS-173 is a substrate for both ABCB1 and ABCG2, resulting in decreased intracellular concentration of this drug, which may have implications for its clinical use.

The WD repeat-containing protein 5 (WDR5) antagonist WDR5-0103 restores the efficacy of cytotoxic drugs in multidrug-resistant cancer cells overexpressing ABCB1 or ABCG2

The development of multidrug resistance (MDR) is one of the major challenges in the treatment of cancer which is caused by the overexpression of the ATP-binding cassette (ABC) transporters ABCB1 (P-glycoprotein) and/or ABCG2 (BCRP/MXR/ABCP) in cancer cells. These transporters are capable of reducing the efficacy of cytotoxic drugs by actively effluxing them out of cancer cells. Since there is currently no approved treatment for patients with multidrug-resistant tumors, the drug repurposing approach provides an alternative route to identify agents to reverse MDR mediated by ABCB1 and/or ABCG2 in multidrug-resistant cancer cells. WDR5-0103 is a histone H3 lysine 4 (H3K4) methyltransferase inhibitor that disrupts the interaction between the WD repeat-containing protein 5 (WDR5) and mixed-lineage leukemia (MLL) protein. In this study, the effect of WDR5-0103 on MDR mediated by ABCB1 and ABCG2 was determined. We found that in a concentration-dependent manner, WDR5-0103 could sensitize ABCB1- and ABCG2-overexpressing multidrug-resistant cancer cells to conventional cytotoxic drugs. Our results showed that WDR5-0103 reverses MDR and improves drug-induced apoptosis in multidrug-resistant cancer cells by inhibiting the drug-efflux function of ABCB1 and ABCG2, without altering the protein expression of ABCB1 or ABCG2. The potential sites of interactions of WDR5-0103 with the drug-binding pockets of ABCB1 and ABCG2 were predicted by molecular docking. In conclusion, the MDR reversal activity of WDR5-0103 demonstrated here indicates that it could be used in combination therapy to provide benefits to a subset of patients with tumor expressing high levels of ABCB1 or ABCG2.

Emerging nanotechnology-based therapeutics to combat multidrug-resistant cancer

Cancer often develops multidrug resistance (MDR) when cancer cells become resistant to numerous structurally and functionally different chemotherapeutic agents. MDR is considered one of the principal reasons for the failure of many forms of clinical chemotherapy. Several factors are involved in the development of MDR including increased expression of efflux transporters, the tumor microenvironment, changes in molecular targets and the activity of cancer stem cells. Recently, researchers have designed and developed a number of small molecule inhibitors and derivatives of natural compounds to overcome various mechanisms of clinical MDR. Unfortunately, most of the chemosensitizing approaches have failed in clinical trials due to non-specific interactions and adverse side effects at pharmacologically effective concentrations. Nanomedicine approaches provide an efficient drug delivery platform to overcome the limitations of conventional chemotherapy and improve therapeutic effectiveness. Multifunctional nanomaterials have been found to facilitate drug delivery by improving bioavailability and pharmacokinetics, enhancing the therapeutic efficacy of chemotherapeutic drugs to overcome MDR. In this review article, we discuss the major factors contributing to MDR and the limitations of existing chemotherapy- and nanocarrier-based drug delivery systems to overcome clinical MDR mechanisms. We critically review recent nanotechnology-based approaches to combat tumor heterogeneity, drug efflux mechanisms, DNA repair and apoptotic machineries to overcome clinical MDR. Recent successful therapies of this nature include liposomal nanoformulations, cRGDY-PEG-Cy5.5-Carbon dots and Cds/ZnS core–shell quantum dots that have been employed for the effective treatment of various cancer sub-types including small cell lung, head and neck and breast cancers.

Euphorbia diterpenoids: isolation, structure, bioactivity, biosynthesis, and synthesis (2013-2021)

Covering: 2013 to 2021As the characteristic metabolites of Euphorbia plants, Euphorbia diterpenoids have always been a hot topic in related science communities due to their intriguing structures and broad bioactivities. In this review, we intent to provide an in-depth and extensive coverage of Euphorbia diterpenoids reported from 2013 to the end of 2021, including 997 new Euphorbia diterpenoids and 78 known ones with latest progress. Multiple aspects will be summarized, including their occurrences, chemical structures, bioactivities, and syntheses, in which the structure-activity relationship and biosynthesis of this class will be discussed for the first time.

Effects of Resveratrol, Curcumin and Quercetin Supplementation on Bone Metabolism—A Systematic Review

Phenolic compounds are natural phytochemicals that have recently reported numerous health benefits. Resveratrol, curcumin, and quercetin have recently received the most attention among these molecules due to their documented antioxidant effects. The review aims to investigate the effects of these molecules on bone metabolism and their role in several diseases such as osteopenia and osteoporosis, bone tumours, and periodontitis. The PubMed/Medline, Web of Science, Google Scholar, Scopus, Cochrane Library, and Embase electronic databases were searched for papers in line with the study topic. According to an English language restriction, the screening period was from January 2012 to 3 July 2022, with the following Boolean keywords: (“resveratrol” AND “bone”); (“curcumin” AND “bone”); (“quercetin” AND “bone”). A total of 36 papers were identified as relevant to the purpose of our investigation. The studies reported the positive effects of the investigated phenolic compounds on bone metabolism and their potential application as adjuvant treatments for osteoporosis, bone tumours, and periodontitis. Furthermore, their use on the titanium surfaces of orthopaedic prostheses could represent a possible application to improve the osteogenic processes and osseointegration. According to the study findings, resveratrol, curcumin, and quercetin are reported to have a wide variety of beneficial effects as supplement therapies. The investigated phenolic compounds seem to positively mediate bone metabolism and osteoclast-related pathologies.

Stem Cells as Target for Prostate cancer Therapy: Opportunities and Challenges

Cancer stem cells (CSCs) and cells in a cancer stem cell-like (CSCL) state have proven to be responsible for tumor initiation, growth, and relapse in Prostate Cancer (PCa) and other cancers; therefore, new strategies are being developed to target such cellular populations. TLR3 activation-based immunotherapy using Polyinosinic:Polycytidylic acid (PIC) has been proposed to be used as a concomitant strategy to first-line treatment. This strategy is based on the induction of apoptosis and an inflammatory response in tumor cells. In combination with retinoids like 9cRA, this treatment can induce CSCs differentiation and apoptosis. A limitation in the use of this combination is the common decreased expression of TLR3 and its main positive regulator p53. observed in many patients suffering of different cancer types such as PCa. Importantly, human exposure to certain toxicants, such as iAs, not only has proven to enrich CSCs population in an in vitro model of human epithelial prostate cells, but additionally, it can also lead to a decreased p53, TLR3 and RA receptor (RARβ), expression/activation and thus hinder this treatment efficacy. Therefore, here we point out the relevance of evaluating the TLR3 and P53 status in PCa patients before starting an immunotherapy based on the use of PIC +9cRA to determine whether they will be responsive to treatment. Additionally, the use of strategies to overcome the lower TLR3, RARβ or p53 expression in PCa patients, like the inclusion of drugs that increase p53 expression, is encouraged, to potentiate the use of PIC+RA based immunotherapy in these patients.

A thioredoxin reductase 1 inhibitor pyrano [3,2-a] phenazine inhibits A549 cells proliferation and migration through the induction of reactive oxygen species production

BACKGROUND

Thioredoxin reductase 1 (TrxR1) inhibitor, pyrano [3,2-a] phenazine, named CPUL-1, was synthesized with potential anticancer activity. The aim of the present work was to explore the potential anti-proliferative and anti-metastatic ability of CPUL-1 against A549 cancer cell lines in vitro.

METHODS AND RESULTS

First, Cell Counting Kit-8 (CCK8) assay was used to assess cell proliferation. The A549 cell migration was evaluated by wound healing assay and transwell assay. Second, the epithelial-mesenchymal transition (EMT)-related proteins in A549 cells treated with CPUL-1 were analyzed by western blot methods. Then, TrxR1 enzyme activity assay and reactive oxygen species (ROS) assay were conducted to evaluate the effect of CPUL-1 on TrxR1 inhibition and ROS levels. Finally, western blotting was used to explore the mechanism of CPUL-1. The study results revealed that the ability of cell proliferation and migration was decreased under CPUL-1 treatment. CPUL-1 could distinctly restrain the migration and invasion of A549 cells through inhibiting EMT process. The results of TrxR1 enzyme activity assay, ROS assay and western blotting showed that CPUL-1 influenced EMT via inducing ROS-mediated ERK/JNK signaling by inhibiting TrxR1 enzyme activity.

CONCLUSIONS

Together, proliferation suppression and anti-metastasis activity of CPUL-1 in A549 cells were demonstrated by all the evidence. Our findings highlight the great potential of phenazine compound CPUL-1 to suppress A549 cells proliferation and metastasis.

Itraconazole Reverts ABCB1-Mediated Docetaxel Resistance in Prostate Cancer

Docetaxel (DTX) was the first chemotherapeutic agent to demonstrate significant efficacy in the treatment of men with metastatic castration-resistant prostate cancer. However, response to DTX is generally short-lived, and relapse eventually occurs due to emergence of drug-resistance. We previously established two DTX-resistant prostate cancer cell lines, LNCaP^R and C4-2B^R, derived from the androgen‐dependent LNCaP cell line, and from the LNCaP lineage-derived androgen-independent C4-2B sub-line, respectively. Using an unbiased drug screen, we identify itraconazole (ITZ), an oral antifungal drug, as a compound that can efficiently re-sensitize drug-resistant LNCaP^R and C4-2B^R prostate cancer cells to DTX treatment. ITZ can re-sensitize multiple DTX-resistant cell models, not only in prostate cancer derived cells, such as PC-3 and DU145, but also in docetaxel-resistant breast cancer cells. This effect is dependent on expression of ATP-binding cassette (ABC) transporter protein ABCB1, also known as P-glycoprotein (P-gp). Molecular modeling of ITZ bound to ABCB1, indicates that ITZ binds tightly to the inward-facing form of ABCB1 thereby inhibiting the transport of DTX. Our results suggest that ITZ may provide a feasible approach to re-sensitization of DTX resistant cells, which would add to the life-prolonging effects of DTX in men with metastatic castration-resistant prostate cancer.

Ultrasound Triggers Hypericin Activation Leading to Multifaceted Anticancer Activity

The use of ultrasound (US) in combination with a responsive chemical agent (sonosensitizer) can selectively trigger the agent's anticancer activity in a process called sonodynamic therapy (SDT). SDT shares some properties with photodynamic therapy (PDT), which has been clinically approved, but sets itself apart because of its use of US rather than light to achieve better tissue penetration. SDT provides anticancer effects mainly via the sonosensitizer-mediated generation of reactive oxygen species (ROS), although the precise nature of the underpinning mechanism is still under debate. This work investigates the SDT anticancer activity of hypericin (Hyp) in vitro in two- (2D) and three-dimensional (3D) HT-29 colon cancer models, and uses PDT as a yardstick due to its well-known Hyp phototoxicity. The cancer cell uptake and cellular localization of Hyp were investigated first to determine the proper noncytotoxic concentration and incubation time of Hyp for SDT. Furthermore, ROS production, cell proliferation, and cell death were evaluated after Hyp was exposed to US. Since cancer relapse and transporter-mediated multidrug resistance (MDR) are important causes of cancer treatment failure, the US-mediated ability of Hyp to elicit immunogenic cell death (ICD) and overcome MDR was also investigated. SDT showed strong ROS-mediated anticancer activity 48 h after treatment in both the HT-29 models. Specific damage-associated molecular patterns that are consistent with ICD, such as calreticulin (CRT) exposure and high-mobility group box 1 protein (HMGB1) release, were observed after SDT with Hyp. Moreover, the expression of the ABC transporter, P-glycoprotein (P-gp), in HT-29/MDR cells was not able to hinder cancer cell responsiveness to SDT with Hyp. This work reveals, for the first time, the US responsiveness of Hyp with significant anticancer activity being displayed, making it a full-fledged sonosensitizer for the SDT of cancer.

Recent Advances in Dual PI3K/mTOR Inhibitors for Tumour Treatment

The PI3K-Akt-mTOR pathway is a viable target for cancer treatment and can be used to treat various malignant tumours, including follicular lymphoma and breast cancer. Both enzymes, PI3K and mTOR, are critical in this pathway. Hence, in recent years, an array of inhibitors targeting these two targets have been studied, showing dual PI3K/mTOR inhibition compared with single targeting small molecule inhibitors. Inhibitors not only inhibit cell proliferation but also promote cell apoptosis. These inhibitors show high potency and little drug resistance even at low doses, suggesting that PI3K/mTOR inhibitors are promising cancer drugs. Herein, we summarised the recent research of PI3K/mTOR dual inhibitors—for example, structure-activity relationship, pharmacokinetics, and clinical practice, and briefly commented on them.

Clinical Trial Registration:https://clinicaltrials.gov.

Multiple Effects of Resveratrol on Osteosarcoma Cell Lines

Osteosarcoma (OS) is the most common primary bone sarcoma affecting the life of pediatric patients. The clinical treatment faces numerous difficulties, including the adverse effects of chemotherapies, chemoresistance, and recurrences. In this study, the effects of resveratrol (RSV), a natural polyphenol, on OS cell lines were investigated to evaluate its action as an adjuvant therapy to the current chemotherapy regimens. RSV exhibited multiple tumor-suppressing activities on OS cell lines, inducing a series of critical events. We found (1) a cell growth inhibition due to an increase in cell distress, which was, in part, due to the involvement of the AKT and caspase-3 pathways, (2) an increase in cellular differentiation due to major gene expression levels of the osteoblastic differentiation genes, (3) an inhibition of IL-6 secretion due to an epigenetic effect on the IL-6 promoter, and (4) an inhibition of OS cells migration related to the decrease in IL-8 secretion levels due to an epigenetic effect on its promoter. Finally, the cotreatment of RSV with doxorubicin and cisplatin increased their cytotoxic effect on OS cells. Although further investigations are mandatory, it seems RSV might be a promising therapeutic adjuvant agent for OS cell treatment, exerting an antitumor effect when combined with chemotherapy.

A critical review on modulators of Multidrug Resistance Protein 1 in cancer cells

Multidrug resistance protein 1 (MRP1/ABCC1) is an ATP-dependent efflux transporter, and responsible for the transport of a broad spectrum of xenobiotics, toxins, and physiological substrates across the plasma membrane. As an efflux pump, it plays a significant role in the absorption and disposition of drugs including anticancer drugs, antivirals, antimalarials, and antibiotics and their metabolites across physiological barriers in cells. MRP1 is also known to aid in the regulation of several physiological processes such as redox homeostasis, steroid metabolism, and tissue defense. However, its overexpression has been reported to be a key clinical marker associated with multidrug resistance (MDR) of several types of cancers including lung cancer, childhood neuroblastoma, breast and prostate carcinomas, often resulting in a higher risk of treatment failure and shortened survival rates in cancer patients. Aside MDR, overexpression of MRP1 is also implicated in the development of neurodegenerative and cardiovascular diseases. Due to the cellular importance of MRP1, the identification and biochemical/molecular characterization of modulators of MRP1 activity and expression levels are of key interest to cancer research and beyond. This review primarily aims at highlighting the physiological and pharmacological importance of MRP1, known MRP1 modulators, current challenges encountered, and the potential benefits of conducting further research on the MRP1 transporter.

A Phenylfurocoumarin Derivative Reverses ABCG2-Mediated Multidrug Resistance In Vitro and In Vivo

The ATP-binding cassette subfamily G member 2 (ABCG2) transporter is involved in the development of multidrug resistance in cancer patients. Many inhibitors of ABCG2 have been reported to enhance the chemosensitivity of cancer cells. However, none of these inhibitors are being used clinically. The aim of this study was to identify novel ABCG2 inhibitors by high-throughput screening of a chemical library. Among the 5812 compounds in the library, 23 compounds were selected in the first screening, using a fluorescent plate reader-based pheophorbide a (PhA) efflux assay. Thereafter, to validate these compounds, a flow cytometry-based PhA efflux assay was performed and 16 compounds were identified as potential inhibitors. A cytotoxic assay was then performed to assess the effect these 16 compounds had on ABCG2-mediated chemosensitivity. We found that the phenylfurocoumarin derivative (R)-9-(3,4-dimethoxyphenyl)-4-((3,3-dimethyloxiran-2-yl)methoxy)-7H-furo [3,2-g]chromen-7-one (PFC) significantly decreased the IC₅₀ of SN-38 in HCT-116/BCRP colon cancer cells. In addition, PFC stimulated ABCG2-mediated ATP hydrolysis, suggesting that this compound interacts with the substrate-binding site of ABCG2. Furthermore, PFC reversed the resistance to irinotecan without causing toxicity in the ABCG2-overexpressing HCT-116/BCRP cell xenograft mouse model. In conclusion, PFC is a novel inhibitor of ABCG2 and has promise as a therapeutic to overcome ABCG2-mediated MDR, to improve the efficiency of cancer chemotherapy.

ATP binding cassette transporters and cancer: revisiting their controversial role

The expression of ATP-binding cassette transporter (ABC transporters) has been reported in various tissues such as the lung, liver, kidney, brain and intestine. These proteins account for the efflux of different compounds and metabolites across the membrane, thus decreasing the concentration of the toxic compounds. ABC transporter genes play a vital role in the development of multidrug resistance, which is the main obstacle that hinders the success of chemotherapy. Preclinical and clinical trials have investigated the probability of overcoming drug-associated resistance and substantial toxicities. The focus has been put on several strategies to overcome multidrug resistance. These strategies include the development of modulators that can modulate ABC transporters. This knowledge can be translated for clinical oncology treatment in the future.

Discovery of the Triazolo[1,5-a]Pyrimidine-Based Derivative WS-898 as a Highly Efficacious and Orally Bioavailable ABCB1 Inhibitor Capable of Overcoming Multidrug Resistance

Targeting P-glycoprotein (ABCB1 or P-gp) has been recognized as a promising strategy to overcome multidrug resistance. Here, we reported our medicinal chemistry efforts that led to the discovery of the triazolo[1,5-a]pyrimidine derivative WS-898 as a highly effective ABCB1 inhibitor capable of reversing paclitaxel (PTX) resistance in drug-resistant SW620/Ad300, KB-C2, and HEK293/ABCB1 cells (IC₅₀ = 5.0, 3.67, and 3.68 nM, respectively), more potent than verapamil and zosuquidar. WS-898 inhibited the efflux function of ABCB1, thus leading to decreased efflux and increased intracellular PTX concentration in SW620/Ad300 cells. The cellular thermal shift assay indicated direct engagement of WS-898 to ABCB1. Furthermore, WS-898 stimulated the ATPase activity of ABCB1 but had minimal effects on cytochrome P450 3A4 (CYP3A4). Importantly, WS-898 increased PTX sensitization in vivo without obvious toxicity. The results suggest that WS-898 is a highly effective triazolo[1,5-a]pyrimidine-based ABCB1 inhibitor and shows promise in reversing ABCB1-mediated PTX resistance.

Distinct allosteric mechanisms of first-generation MsbA inhibitors

[Figure: see text].

Lepidium sativum Secondary Metabolites (Essential Oils): In Vitro and In Silico Studies on Human Hepatocellular Carcinoma Cell Lines

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and the greatest cause of cancer-related death in the world. Garden cress (Lepidium sativum) seeds have been proven to possess extraordinary antioxidant, anti-inflammatory, hypothermic, and analgesic properties. In this study, in vitro cytotoxic efficiency evaluation of L. sativum fractions was performed against two hepatocellular carcinoma cell lines (HuH-7 and HEPG-2), and the expression of some apoptotic genes was explored. In addition, the chemical composition of a potent extract of L. sativum was analyzed using gas chromatography coupled with mass spectrometry. Then, molecular docking analysis was implemented to identify the potential targets of the L. sativum components’ most potent extract. Overall, the n-hexane extract was the most potent against the two HCC cell lines. Moreover, these cytotoxicity levels were supported by the significant downregulation of EGFR and BCL2 gene expression levels and the upregulation of SMAD3, BAX, and P53 expression levels in both HuH-7 and HEPG2 cell lines. Regarding L. sativum’s chemical composition, GC–MS analysis of the n-hexane extract led to the identification of thirty compounds, including, mainly, hydrocarbons and terpenoids, as well as other volatile compounds. Furthermore, the binding affinities and interactions of the n-hexane fraction’s major metabolites were predicted against EGFR and BCL2 molecular targets using the molecular docking technique. These findings reveal the potential use of L. Sativum in the management of HCC.

Oral lipid nanomedicines: Current status and future perspectives in cancer treatment

Oral anticancer drugs have earned a seat at the table, as the need for homecare treatment in oncology has increased. Interest in this field is growing as a result of their proven efficacy, lower costs and positive patient uptake. However, the gastrointestinal barrier is still the main obstacle to surmount in chemotherapeutic oral delivery. Anticancer nanomedicines have been proposed to solve this quandary. Among these, lipid nanoparticles are described to be efficiently absorbed while protecting drugs from early degradation in hostile environments. Their intestinal lymphatic tropism or mucoadhesive/penetrative properties give them unique characteristics for oral administration. Considering that chronic cancer cases are increasing over time, it is important to be able to provide treatments with low toxicity and low prices. The challenges, opportunities and therapeutic perspectives of lipid nanoparticles in this area will be discussed in this review, taking into consideration the pre-clinical and clinical progress made in the last decade.

KRAS and EGFR Mutations Differentially Alter ABC Drug Transporter Expression in Cisplatin-Resistant Non-Small Cell Lung Cancer

Lung carcinoma is still the most common malignancy worldwide. One of the major subtypes of non-small cell lung cancer (NSCLC) is adenocarcinoma (AC). As driver mutations and hence therapies differ in AC subtypes, we theorized that the expression and function of ABC drug transporters important in multidrug resistance (MDR) would correlate with characteristic driver mutations KRAS or EGFR. Cisplatin resistance (CR) was generated in A549 (KRAS) and PC9 (EGFR) cell lines and gene expression was tested. In three-dimensional (3D) multicellular aggregate cultures, both ABCB1 and ABCG2 transporters, as well as the WNT microenvironment, were investigated. ABCB1 and ABCG2 gene expression levels were different in primary AC samples and correlated with specific driver mutations. The drug transporter expression pattern of parental A549 and PC9, as well as A549-CR and PC9-CR, cell lines differed. Increased mRNA levels of ABCB1 and ABCG2 were detected in A549-CR cells, compared to parental A549, while the trend observed in the case of PC9 cells was different. Dominant alterations were observed in LEF1, RHOU and DACT1 genes of the WNT signalling pathway in a mutation-dependent manner. The study confirmed that, in lung AC-s, KRAS and EGFR driver mutations differentially affect both drug transporter expression and the cisplatin-induced WNT signalling microenvironment.

Overexpression of ABCC1 Confers Drug Resistance to Betulin

Betulin is a lupane-type pentacyclic triterpene, which is isolated from birch bark. It has a broad spectrum of biological and pharmacological properties, such as anti-inflammatory, anti-tumor, anti-viral, and anti-bacterial activity. Herein, we explored the factors that may result in betulin resistance, especially with respect to its interaction with ATP-binding cassette subfamily C member 1 (ABCC1). ABCC1 is an important member of the ATP-binding cassette (ABC) transporter family, which is central to mediating multidrug resistance (MDR) in naturally derived anticancer agents. An MTT-based cell viability assay showed that ABCC1 overexpression has the ability to desensitize both cancer cell line and gene-transfected cell line to betulin and that this betulin-induced resistance can be antagonized by a known ABCC1 inhibitor MK571 at 25 μM. Additionally, betulin upregulates the ABCC1 protein expression level in both concentration-dependent and time-dependent manners, also blocks the transport function mediated by ABCC1. Subsequently, a high affinity score of betulin was achieved in a computational docking analysis, demonstrating a strong interaction of betulin with ABCC1.

Incorporation of natural assumption to deal with cancer

The current state of the art for the use of natural ingredients for cancer therapy is by reviewing the publications and findings associated with cancer research with the employment of flavonoids. Cancer is the most furious disease making fear in the eyes of mankind. Though various treatment methods are prevalent, the patient's choices are shifting from synthetic treatment strategy to the natural ones. The plant-based metabolites are used very often in our life as a food additive and also as a medicine for primary health care. The safety profile and its efficacy add on advantage for the incorporation of the natural products separately or in combination as a remedy for cancer. Flavonoids, the plant-based metabolites are proven for their anti-inflammatory, anti-oxidant, and anti-cancer properties. Their chemotherapeutic and chemosensitizing power had made it interesting for the researchers to dig more on the health benefits of the flavonoids and incorporating it in a holistic approach, with its natural benefits to relieve the pain and the symptoms of the patient suffering from various medical conditions. The predominant approach for the management of cancer is by following safe and effective treatment modality. In this review, we mentioned the benefits of the flavonoids for the management of various cancers and its potency as a chemotherapeutic agent and as the chemosensitizer. Our mother nature had given remedies to cure various diseases in both human beings and animals by it; we just need to find out the sources and access to them.

Structure-Based Design, Synthesis, and Biological Evaluation of New Triazolo[1,5-a]Pyrimidine Derivatives as Highly Potent and Orally Active ABCB1 Modulators

ABCB1 is a promising therapeutic target for overcoming multidrug resistance (MDR). In this work, we reported the structure-based design of triazolo[1,5-a]pyrimidines as new ABCB1 modulators, of which WS-691 significantly increased sensitization of ABCB1-overexpressed SW620/Ad300 cells to paclitaxel (PTX) (IC₅₀ = 22.02 nM). Mechanistic studies indicated that WS-691 significantly increased the intracellular concentration of PTX and [³H]-PTX while decreasing the efflux of [³H]-PTX in SW620/Ad300 cells by inhibiting the efflux function of ABCB1. The cellular thermal shift assay suggested that WS-691 could stabilize ABCB1 by directly binding to ABCB1. WS-691 could stimulate the activity of ABCB1 ATPase but had almost no inhibitory activity against CYP3A4. Importantly, WS-691 increased the sensitivity of SW620/Ad300 cells to PTX in vivo without observed toxicity. Collectively, WS-691 is a highly potent and orally active ABCB1 modulator capable of overcoming MDR. The triazolo[1,5-a]pyrimidine may be a promising scaffold for developing more potent ABCB1 modulators.

The functional role of long non-coding RNAs and their underlying mechanisms in drug resistance of non-small cell lung cancer

BACKGROUND

Non-small cell lung cancer (NSCLC) is the most commonly diagnosed solid cancer and the main origin of cancer-related deaths worldwide. Current strategies to treat advanced NSCLC are based on a combined approach of targeted therapy and chemotherapy. But most patients will eventually get resistance to either chemotherapy or targeted therapy, leading to the poor prognosis. The mechanism of NSCLC drug resistance is inconclusive and is affected by multiple factors. Long non-coding RNAs (LncRNAs) are non-coding RNAs (ncRNAs) longer than 200 nucleotides. Recent studies show that lncRNAs are involved in many cellular physiological activities, including drug resistance of NSCLC. It is of great clinical significance to understand the specific mechanisms and the role of lncRNAs in it.

CONCLUSIONS

Herein, we focus on the functional roles and the underlying mechanisms of lncRNAs in acquired drug resistance of NSCLC. LncRNAs have potential values as novel prognostic biomarkers and even therapeutic targets in the clinical management of NSCLC.

Investigation of physiological and molecular mechanisms conferring diurnal variation in auxinic herbicide efficacy

The efficacy of auxinic herbicides, a valuable weed control tool for growers worldwide, has been shown to vary with the time of day in which applications are made. However, little is known about the mechanisms causing this phenomenon. Investigating the differential in planta behavior of these herbicides across different times of application may grant an ability to advise which properties of auxinic herbicides are desirable when applications must be made around the clock. Radiolabeled herbicide experiments demonstrated a likely increase in ATP-binding cassette subfamily B (ABCB)-mediated 2,4-D and dicamba transport in Palmer amaranth (Amaranthus palmeri S. Watson) at simulated dawn compared to mid-day, as dose response models indicated that many orders of magnitude higher concentrations of N-1-naphthylphthalamic acid (NPA) and verapamil, respectively, are required to inhibit translocation by 50% at simulated sunrise compared to mid-day. Gas chromatographic analysis displayed that ethylene evolution in A. palmeri was higher when dicamba was applied during mid-day compared to sunrise. Furthermore, it was found that inhibition of translocation via 2,3,5-triiodobenzoic acid (TIBA) resulted in an increased amount of 2,4-D-induced ethylene evolution at sunrise, and the inhibition of dicamba translocation via NPA reversed the difference in ethylene evolution across time of application. Dawn applications of these herbicides were associated with increased expression of a putative 9-cis-epoxycarotenoid dioxygenase biosynthesis gene NCED1, while there was a notable lack of trends observed across times of day and across herbicides with ACS1, encoding 1-aminocyclopropane-1-carboxylic acid synthase. Overall, this research indicates that translocation is differentially regulated via specific protein-level mechanisms across times of application, and that ethylene release, a chief phytotoxic process involved in the response to auxinic herbicides, is related to translocation. Furthermore, transcriptional regulation of abscisic acid involvement in phytotoxicity and/or translocation are suggested.

Herb-drug interactions between the medicinal mushrooms Lingzhi and Yunzhi and cytotoxic anticancer drugs: a systematic review

BACKGROUND

Lingzhi and Yunzhi are medicinal mushrooms commonly used with cytotoxic chemotherapy in cancer patients in Asian countries. The current systematic review aims to identify potential pharmacokinetic or pharmacodynamic interactions from the existing literature to ensure their effective and safe combination usage in cancer patients.

METHODS

A systematic search was conducted on nine major Chinese and English databases, including China Journal Net, Allied and Complementary Medicine Database, and Ovid MEDLINE®, etc., to identify clinical, animal, and in-vitro studies that evaluate the effect of combined use of Lingzhi or Yunzhi with cytotoxic drugs. The Jadad scale was used to assess the quality of clinical studies.

RESULTS

This search identified 213 studies, including 77 clinical studies that reported on the combined use of cytotoxic drugs with Yunzhi (n = 56) or Lingzhi (n = 21). Majority of these clinical studies demonstrated modest methodological quality. In clinical practice, the most commonly used cytotoxic drugs with Lingzhi were cisplatin, 5-fluorouracil (5-FU) and paclitaxel, whereas Tegafur/uracil (UFT)/Tegafur, 5-FU, and mitomycin were the ones used more often with Yunzhi. Only two clinical pharmacokinetic studies were available showing no significant interactions between Polysaccharide K (PSK) and Tegafur. From the pharmacodynamic interactions perspective, combination uses of Yunzhi/Lingzhi with cytotoxic drugs in clinical practice could lead to improvement in survival (n = 31) and quality of life (n = 17), reduction in tumor lesions (n = 22), immune modulation (n = 38), and alleviation of chemotherapy-related side effects (n = 14) with no reported adverse effects.

CONCLUSION

Our findings suggest that the clinical combination use of Lingzhi or Yunzhi with cytotoxic drugs could enhance the efficacy and ameliorate the adverse effects of cytotoxic drugs, leading to improved quality of life in cancer patients. More high quality clinical studies including pharmacokinetic herb-drug interactions studies are warranted to verify these observations and mechanisms involved. Based on the high quality clinical data, pharmacoepidemiology methods and bioinformatics or data mining could be adopt for further identification of clinical meaningful herb-drug interactions in cancer therapies.

Expression profile of stem cell markers and ABC transporters in 5-fluorouracil resistant Hep-2 cells

Resistance of laryngeal squamous cell carcinoma cells to traditional therapeutic regimens still remains to be a major reason for therapeutic failure in patients. In this study, we aimed at investigating the expression profiles of ATP-binding cassette (ABC) transporters and stem cell markers in 5-fluorouracil (5-FU) resistant laryngeal Hep-2 cells. We treated parental Hep-2 cells, with stepwise increased doses of 5-FU for almost 1 year to develop 5-FU resistant sub-lines with resistance against varying levels of 5-FU concentrations (4 sub-lines resistant to 1, 2, 4, and eightfold of 5-FU). Then, we measured the expression levels of 10 genes from ABC transporters family and 4 stem cell associated markers using quantitative reverse transcription polymerase chain reaction (qRT-PCR) to find out a potential relationship between these markers and chemoresistance. We found that stemness-associated markers had elevated expressions from the beginning of 5-FU resistance acquisition. Their expressions elevated stepwise while parental Hep-2 cells got resistance to higher doses of 5-FU. Expressions of tested ABC transporters (ABCA5, ABCB1, ABCB6, ABCC1, ABCC2, ABCC3, ABCC5, ABCC10 and ABCF2, and ABCG2) were also deregulated in 5-FU resistant Hep-2 cells. Although their expressions remained unaltered at the beginning of acquisition of resistance, expressions of ABC transporters except from ABCB6 increased significantly when cells became resistant to higher doses of 5-FU. Our results suggest that enrichment of cells with stemness characteristics and upregulation of ABC transporters might be amongst the crucial contributors of chemoresistance in laryngeal cancer cells.

Overexpression of ABCB1 and ABCG2 contributes to reduced efficacy of the PI3K/mTOR inhibitor samotolisib (LY3023414) in cancer cell lines

LY3023414 (samotolisib) is a promising new dual inhibitor of phosphoinositide 3-kinase (PI3K) and mammalian target of rapamycin (mTOR). Currently, multiple clinical trials are underway to evaluate the efficacy of LY3023414 in patients with various types of cancer. However, the potential mechanisms underlying acquired resistance to LY3023414 in human cancer cells still remain elusive. In this study, we investigated whether the overexpression of ATP-binding cassette (ABC) drug transporters such as ABCB1 and ABCG2, one of the most common mechanisms for developing multidrug resistance, may potentially reduce the efficacy of LY3023414 in human cancer cells. We demonstrated that the intracellular accumulation of LY3023414 in cancer cells was significantly reduced by the drug efflux function of ABCB1 and ABCG2. Consequently, the cytotoxicity and efficacy of LY3023414 for inhibiting the activation of the PI3K pathway and induction of G0/G1 cell-cycle arrest were substantially reduced in cancer cells overexpressing ABCB1 or ABCG2, which could be restored using tariquidar or Ko143, respectively. Furthermore, stimulatory effect of LY3023414 on the ATPase activity of ABCB1 and ABCG2, as well as in silico molecular docking analysis of LY3023414 binding to the substrate-binding pockets of these transporters provided additional insight into the manner in which LY3023414 interacts with both transporters. In conclusion, we report that LY3023414 is a substrate for ABCB1 and ABCG2 transporters implicating their role in the development of resistance to LY3023414, which can have substantial clinical implications and should be further investigated.

Intra-tumoral drug concentration mapping within solid tumor micro-milieu using in-vitro model and doxorubicin as a model drug

In contrast to plasma pharmacokinetics, intratumoral pharmacokinetics of doxorubicin (DOX) determines its spatial anti-tumoral activity. Three-dimensional multicellular layers (MCL) model for solid tumors present optimum experimental platform for studying the intratumoral pharmacokinetics of DOX. This might imply new insights for understanding intratumoral pharmacokinetic parameters with realistic clinical implications. Herein, we are presenting simplified method for the spatial in-situ concentration assessment of DOX within the avascular simulating MCL solid tumor model of DLD-1 and HT-29 cell lines. DLD-1 and HT-29 formed viable well-structured MCL model abundant in extracellular matrix component (fibronectin). DOX (100 µM) showed stronger anti-proliferative effect against MCL of DLD-1 compared to HT-29 MCL (38.8% and 27.9%, respectively). The differential potencies of DOX closely correlate to the intratumoral pharmacokinetics within MCL’s of both cell lines. DOX penetrated faster and washed out slower through the MCL of DLD-1 compared to HT-29 MCL. Distribution of DOX within MCL of DLD-1 was more homogenous compared to HT-29 MCL. Tissue concentration of DOX within MCL of DLD-1 was significantly higher than HT-29 MCL’s after 96 h exposure (0.7 and 0.4 µmole/gm tissue, respectively). Concentration of DOX within MCL of both cell lines exceeded the IC₅₀ under monolayer conditions (2.3 ± 0.6 µM and 0.6 ± 0.1 µM, respectively). In addition, DOX was extensively metabolized to less active metabolites (doxorubicinol and doxorubicinone) through the thickness of both MCL’s. In conclusion, Intratumoral pharmacokinetic barriers to DOX might be key determinant in drug resistance on the tissue level, despite cellular and molecular events.

Cancer stem cells and oral cancer: insights into molecular mechanisms and therapeutic approaches

Cancer stem cells (CSCs) have been identified as a little population of cancer cells, which have features as the same as the cells normal stem cells. There is enough knowledge of the CSCs responsibility for metastasis, medicine resistance, and cancer outbreak. Therefore, CSCs control possibly provides an efficient treatment intervention inhibiting tumor growth and invasion. In spite of the significance of targeting CSCs in treating cancer, few study comprehensively explored the nature of oral CSCs. It has been showed that oral CSCs are able to contribute to oral cancer progression though activation/inhibition a sequences of cellular and molecular pathways (microRNA network, histone modifications and calcium regulation). Hence, more understanding about the properties of oral cancers and their behaviors will help us to develop new therapeutic platforms. Head and neck CSCs remain a viable and intriguing option for targeted therapy. Multiple investigations suggested the major contribution of the CSCs to the metastasis, tumorigenesis, and resistance to the new therapeutic regimes. Therefore, experts in the field are examining the encouraging targeted therapeutic choices. In spite of the advancements, there are not enough information in this area and thus a magic bullet for targeting and eliminating the CSCs deviated us. Hence, additional investigations on the combined therapies against the head and neck CSCs could offer considerable achievements. The present research is a review of the recent information on oral CSCs, and focused on current advancements in new signaling pathways contributed to their stemness regulation. Moreover, we highlighted various therapeutic approaches against oral CSCs.

Mechanisms of promiscuity among drug metabolizing enzymes and drug transporters

Detoxication, or 'drug-metabolizing', enzymes and drug transporters exhibit remarkable substrate promiscuity and catalytic promiscuity. In contrast to substrate-specific enzymes that participate in defined metabolic pathways, individual detoxication enzymes must cope with substrates of vast structural diversity, including previously unencountered environmental toxins. Presumably, evolution selects for a balance of 'adequate' kcat /KM values for a wide range of substrates, rather than optimizing kcat /KM for any individual substrate. However, the structural, energetic, and metabolic properties that achieve this balance, and hence optimize detoxication, are not well understood. Two features of detoxication enzymes that are frequently cited as contributions to promiscuity include the exploitation of highly reactive versatile cofactors, or cosubstrates, and a high degree of flexibility within the protein structure. This review examines these intuitive mechanisms in detail and clarifies the contributions of the classic ligand binding models 'induced fit' (IF) and 'conformational selection' (CS) to substrate promiscuity. The available literature data for drug metabolizing enzymes and transporters suggest that IF is exploited by these promiscuous detoxication enzymes, as it is with substrate-specific enzymes, but the detoxication enzymes uniquely exploit 'IFs' to retain a wide range of substrates at their active sites. In contrast, whereas CS provides no catalytic advantage to substrate-specific enzymes, promiscuous enzymes may uniquely exploit it to recruit a wide range of substrates. The combination of CS and IF, for recruitment and retention of substrates, can potentially optimize the promiscuity of drug metabolizing enzymes and drug transporters.

Reversal of ABCB1-related multidrug resistance by ERK5-IN-1

Background

Inhibition of ABC transporters is considered the most effective way to circumvent multidrug resistance (MDR). In the present study, we evaluated the MDR modulatory potential of ERK5-IN-1, a potent extracelluar signal regulated kinase 5 (ERK5) inhibitor.

Methods

The cytotoxicity and MDR reversal effect of ERK5-IN-1 were assessed by MTT assay. The KBv200-inoculated nude mice xenograft model was used for the in vivo study. Doxorubicin efflux and accumulation were measured by flow cytometry. The modulation of ABCB1 activity was measured by colorimetric ATPase assay and [¹²⁵I]-iodoarylazidoprazosin (IAAP) photolabeling assay. Effect of ERK5-IN-1 on expression of ABCB1 and its downstream markers was measured by PCR and/or Western blot. Cell surface expression and subcellular localization of ABCB1 were tested by flow cytometry and immunofluorescence.

Results

Our results showed that ERK5-IN-1 significantly increased the sensitivity of vincristine, paclitaxel and doxorubicin in KBv200, MCF7/adr and HEK293/ABCB1 cells, respectively. This effect was not found in respective drug sensitive parental cell lines. Moreover, in vivo combination studies showed that ERK5-IN-1 effectively enhanced the antitumor activity of paclitaxel in KBv200 xenografts without causing addition toxicity. Mechanistically, ERK5-IN-1 increased intracellular accumulation of doxorubicin dose dependently by directly inhibiting the efflux function of ABCB1. ERK5-IN-1 stimulated the ABCB1 ATPase activity and inhibited the incorporation of [¹²⁵I]-iodoarylazidoprazosin (IAAP) into ABCB1 in a concentration-dependent manner. In addition, ERK5-IN-1 treatment neither altered the expression level of ABCB1 nor blocked the phosphorylation of downstream Akt or Erk1/2. No significant reversal effect was observed on ABCG2-, ABCC1-, MRP7- and LRP-mediated drug resistance.

Conclusions

Collectively, these results indicated that ERK5-IN-1 efficiently reversed ABCB1-mediated MDR by competitively inhibiting the ABCB1 drug efflux function. The use of ERK5-IN-1 to restore sensitivity to chemotherapy or to prevent resistance could be a potential treatment strategy for cancer patients.

Understanding Failure and Improving Treatment Using HDAC Inhibitors for Prostate Cancer

Novel treatment regimens are required for castration-resistant prostate cancers (CRPCs) that become unresponsive to standard treatments, such as docetaxel and enzalutamide. Histone deacetylase (HDAC) inhibitors showed promising results in hematological malignancies, but they failed in solid tumors such as prostate cancer, despite the overexpression of HDACs in CRPC. Four HDAC inhibitors, vorinostat, pracinostat, panobinostat and romidepsin, underwent phase II clinical trials for prostate cancers; however, phase III trials were not recommended due to a majority of patients exhibiting either toxicity or disease progression. In this review, the pharmacodynamic reasons for the failure of HDAC inhibitors were assessed and placed in the context of the advancements in the understanding of CRPCs, HDACs and resistance mechanisms. The review focuses on three themes: evolution of androgen receptor-negative prostate cancers, development of resistance mechanisms and differential effects of HDACs. In conclusion, advancements can be made in this field by characterizing HDACs in prostate tumors more extensively, as this will allow more specific drugs catering to the specific HDAC subtypes to be designed.

Dual-functionalized liposome by co-delivery of paclitaxel with sorafenib for synergistic antitumor efficacy and reversion of multidrug resistance

Multidrug resistance (MDR) remains one of the major reasons for inefficiency of many chemotherapeutic agents in cancer therapy. In this study, a D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) and polylysine-deoxycholic acid copolymer (PLL-DA) co-modified cationic liposome coating with hyaluronic acid (HA) was constructed for co-delivery of paclitaxel (PTX) and chemosensitizing agent, sorafenib (SOR) to treat the MDR cancer. The multifunctional liposome (HA-TPD-CL-PTX/SOR) presented good stability against rat plasma and was capable of reversing surface zeta potential under acidic conditions in the presence of HAase. Additionally, experimental result confirmed that the PLL-DA copolymer would facilitate the endo-lysosomal escape of the liposome. In vitro study demonstrated that HA-TPD-CL-PTX/SOR could significantly enhance drug accumulation in resistant MCF-7/MDR cells by inhibiting the P-gp efflux, and effectively inhibited growth of tumor cells. Furthermore, the liposome showed an enhanced anticancer activity in vivo, with a tumor growth inhibition rate of 78.52%. In summary, HA-TPD-CL-PTX/SOR exhibited a great potential for effective therapy of resistant cancers by combining with chemotherapeutic agents and could be a promising nano-carrier for reversing MDR and improving the effectiveness of chemotherapy.

Combined approach of homology modeling, molecular dynamics, and docking: computer-aided drug discovery

With the continuous development in software, algorithms, and increase in computer speed, the field of computer-aided drug design has been witnessing reduction in the time and cost of the drug designing process. Structure based drug design (SBDD), which is based on the 3D structure of the enzyme, is helping in proposing novel inhibitors. Although a number of crystal structures are available in various repositories, there are various proteins whose experimental crystallization is difficult. In such cases, homology modeling, along with the combined application of MD and docking, helps in establishing a reliable 3D structure that can be used for SBDD. In this review, we have reported recent works, which have employed these three techniques for generating structures and further proposing novel inhibitors, for cytoplasmic proteins, membrane proteins, and metal containing proteins. Also, we have discussed these techniques in brief in terms of the theory involved and the various software employed. Hence, this review can give a brief idea about using these tools specifically for a particular problem.

Therapeutic Strategies Targeting Cancer Stem Cells and Their Microenvironment

Cancer stem cells (CSCs) have been demonstrated in a variety of tumors and are thought to act as a clonogenic core for the genesis of new tumor growth. This small subpopulation of cancer cells has been proposed to help drive tumorigenesis, metastasis, recurrence and conventional therapy resistance. CSCs show self-renewal and flexible clonogenic properties and help define specific tumor microenvironments (TME). The interaction between CSCs and TME is thought to function as a dynamic support system that fosters the generation and maintenance of CSCs. Investigation of the interaction between CSCs and the TME is shedding light on the biologic mechanisms underlying the process of tumor malignancy, metastasis, and therapy resistance. We summarize recent advances in CSC biology and their environment, and discuss the challenges and future strategies for targeting this biology as a new therapeutic approach.

ABC Transporter-Mediated Multidrug-Resistant Cancer

ATP-binding cassette (ABC) transporters are involved in active pumping of many diverse substrates through the cellular membrane. The transport mediated by these proteins modulates the pharmacokinetics of many drugs and xenobiotics. These transporters are involved in the pathogenesis of several human diseases. The overexpression of certain transporters by cancer cells has been identified as a key factor in the development of resistance to chemotherapeutic agents. In this chapter, the localization of ABC transporters in the human body, their physiological roles, and their roles in the development of multidrug resistance (MDR) are reviewed. Specifically, P-glycoprotein (P-GP), multidrug resistance-associated proteins (MRPs), and breast cancer resistance protein (BCRP/ABCG2) are described in more detail. The potential of ABC transporters as therapeutic targets to overcome MDR and strategies for this purpose are discussed as well as various explanations for the lack of efficacy of ABC drug transporter inhibitors to increase the efficiency of chemotherapy.

The Role of ATP-Binding Cassette Transporters in the Chemoresistance of Anaplastic Thyroid Cancer: A Systematic Review

Anaplastic thyroid cancer (ATC) is an aggressive type of thyroid cancer with a high mortality rate. Cytotoxic drugs are among the treatment modalities usually used for ATC treatment. However, systemic chemotherapies for ATC have not been shown to have remarkable efficacy. ATP-binding cassette (ABC) transporters have been suggested as a possible mechanism in ATC resistance to chemotherapy. This systematic review was aimed to define the possible roles of ABC transporters in ATC resistance to chemotherapy. Numerous databases, including Scopus, Web of Science, PubMed, Cochrane Library, Ovid, ProQuest, and EBSCO, were searched for papers published since 1990, with predefined keywords. The literature searches were updated twice, in 2015 and 2017. All identified articles were reviewed, and 14 papers that met the inclusion criteria were selected. In the eligible studies, the roles of 10 out of 49 ABC transporters were evaluated; among them, three pumps (ABCB1, ABCC1, and ABCG2) were the most studied transporters in ATC samples. ABCC1 and ABCG2 had the highest expression rates in ATC, and ABCB1 ranked second among the inspected transporters. In conclusion, ABC transporters are the major determinants of ATC resistance to chemotherapy. By identifying these transporters, we can tailor the best treatment approach for patients with ATC. Additional studies are needed to define the exact role of each ABC transporter and other mechanisms in ATC drug resistance.

Unsymmetric dihydropyridines bearing 2-pyridyl methyl carboxylate as modulators of P-glycoprotein; synthesis and biological evaluation in resistant and non-resistant cancer cells

Multi-drug resistance (MDR) in cancer cells is often associated with overexpression of P-glycoprotein (P-gp or ABCB1 or MDR1); therefore, modulators of this transporter might be helpful in overcoming MDR. In this study, 16 novel unsymmetrical dihydropyridine (DHP) derivatives bearing 2-pyridyl methyl carboxylate at C3 and a nitroimidazole or nitrophenyl ring at C4 positions of the DHP ring were synthesized. Their cytotoxicity was tested against four human cancer cells by MTT assay. The reversal capacity of MDR was examined in P-gp overexpressing cells (MES-SA/DX5) by measuring the alteration of doxorubicin’s IC50 and performing flow cytometric determination of intracellular rhodamine 123 accumulation. The calcium channel blocking (CCB) activity, as a side effect of DHPs, was tested on the ileum of a guinea pig. Molecular docking was performed to explain the binding mode of compounds. Two derivatives, 4a and 4c, containing 4-nitrophenyl at C4 and possessing methyl (4a) and iso-propyl (4c) carboxylates at the C5 position of DHP core demonstrated superior cytotoxic and MDR reversal activities and lower CCB effect. Docking analysis confirmed the importance of the 4-nitrophenyl ring for P-gp inhibitory activity. Some of the synthesized DHP derivatives with considerable MDR reversal capacity could be promising compounds for further discovery of useful agents for management of drug resistant cancer.

The Role of Cancer Stem Cells and Mechanical Forces in Ovarian Cancer Metastasis

Ovarian cancer is an extremely lethal gynecologic disease; with the high-grade serous subtype predominantly associated with poor survival rates. Lack of early diagnostic biomarkers and prevalence of post-treatment recurrence, present substantial challenges in treating ovarian cancers. These cancers are also characterized by a high degree of heterogeneity and protracted metastasis, further complicating treatment. Within the ovarian tumor microenvironment, cancer stem-like cells and mechanical stimuli are two underappreciated key elements that play a crucial role in facilitating these outcomes. In this review article, we highlight their roles in modulating ovarian cancer metastasis. Specifically, we outline the clinical relevance of cancer stem-like cells, and challenges associated with their identification and characterization and summarize the ways in which they modulate ovarian cancer metastasis. Further, we review the mechanical cues in the ovarian tumor microenvironment, including, tension, shear, compression and matrix stiffness, that influence (cancer stem-like cells and) metastasis in ovarian cancers. Lastly, we outline the challenges associated with probing these important modulators of ovarian cancer metastasis and provide suggestions for incorporating these cues in basic biology and translational research focused on metastasis. We conclude that future studies on ovarian cancer metastasis will benefit from the careful consideration of mechanical stimuli and cancer stem cells, ultimately allowing for the development of more effective therapies.