Inhibition of aldehyde dehydrogenase-1 and p-glycoprotein-mediated multidrug resistance by curcumin and vitamin D3 increases sensitivity to paclitaxel in breast cancer

A vitamin D-based strategy overcomes chemoresistance in prostate cancer

BACKGROUND AND PURPOSE

Castration-resistant prostate cancer (CRPC) is a common male malignancy that requires new therapeutic strategies due to acquired resistance to its first-line treatment, docetaxel. The benefits of vitamin D on prostate cancer (PCa) progression have been previously reported. This study aimed to investigate the effects of vitamin D on chemoresistance in CRPC.

EXPERIMENTAL APPROACH

Structure function relationships of potent vitamin D analogues were determined. The combination of the most potent analogue and docetaxel was explored in chemoresistant primary PCa spheroids and in a xenograft mouse model derived from a patient with a chemoresistant CRPC.

KEY RESULTS

Here, we show that Xe4MeCF3 is more potent than the natural ligand to induce vitamin D receptor (VDR) transcriptional activities and that it has a larger therapeutic window. Moreover, we demonstrate that VDR agonists restore docetaxel sensitivity in PCa spheroids. Importantly, Xe4MeCF3 reduces tumour growth in a chemoresistant CRPC patient-derived xenograft. In addition, this treatment targets signalling pathways associated with cancer progression in the remaining cells.

CONCLUSION AND IMPLICATIONS

Taken together, these results unravel the potency of VDR agonists to overcome chemoresistance in CRPC and open new avenues for the clinical management of PCa.

Carrier-free chemo-phototherapeutic nanomedicines with endo/lysosomal escape function enhance the therapeutic effect of drug molecules in tumors

Carrier-free nanomedicines offer advantages of extremely high drug loading capacity (>80%), minimal non-drug constituent burden, and facile preparation processes. Numerous studies have proved that multimodal cancer therapy can enhance chemotherapy efficiency and mitigate multi-drug resistance (MDR) through synergistic therapeutic effects. Upon penetration into the tumor matrix, nanoparticles (NPs) are anticipated to be uptaken by cancer cells, primarily through clathrin-meditated endocytosis pathways, leading to their accumulation in endosomes/lysosomes within cells. However, endo/lysosomes exhibit a highly degradative environment for organic NPs and drug molecules, often resulting in treatment failure. Hence, this study designed a lysosomal escape mechanism with carrier-free nanomedicine, combining the chemotherapeutic drug, curcumin (Cur), and the photothermal/photodynamic therapeutic drug, indocyanine green (ICG), for synergistic cancer treatment (ICG-Cur NPs) via a facile preparation process. To facilitate endo/lysosomal escape, ICG-Cur NPs were modified with metal-phenolic networks (MPNs) of different thickness. The results indicate that a thick MPN coating promotes rapid endo/lysosomal escape of ICG-Cur NPs within 4 h and enhances the photothermal conversion efficiency of ICG-Cur NPs by 55.8%, significantly improving anticancer efficacy in both chemo- and photo-therapies within 3D solid tumor models. This finding underscores the critical role of endo/lysosomal escape capacity in carrier-free drug NPs for therapeutic outcomes and offers a facile solution to achieve it.

Slow Sulfide Donor GYY4137 Increased the Sensitivity of Two Breast Cancer Cell Lines to Paclitaxel by Different Mechanisms

Paclitaxel (PTX) is a chemotherapeutic agent affecting microtubule polymerization. The efficacy of PTX depends on the type of tumor, and its improvement would be beneficial in patients' treatment. Therefore, we tested the effect of slow sulfide donor GYY4137 on paclitaxel sensitivity in two different breast cancer cell lines, MDA-MB-231, derived from a triple negative cell line, and JIMT1, which overexpresses HER2 and is resistant to trastuzumab. In JIMT1 and MDA-MB-231 cells, we compared IC50 and some metabolic (apoptosis induction, lactate/pyruvate conversion, production of reactive oxygen species, etc.), morphologic (changes in cytoskeleton), and functional (migration, angiogenesis) parameters for PTX and PTX/GYY4137, aiming to determine the mechanism of the sensitization of PTX. We observed improved sensitivity to paclitaxel in the presence of GYY4137 in both cell lines, but also some differences in apoptosis induction and pyruvate/lactate conversion between these cells. In MDA-MB-231 cells, GYY4137 increased apoptosis without affecting the IP3R1 protein, changing the morphology of the cytoskeleton. A mechanism of PTX sensitization by GYY4137 in JIMT1 cells is distinct from MDA-MB-231, and remains to be further elucidated. We suggest different mechanisms of action for H2S on the paclitaxel treatment of MDA-MB-231 and JIMT1 breast cancer cell lines.

Protective Effects of Dietary Vitamin D3, Turmeric Powder, and Their Combination against Gasoline Intoxication in Rats

The inhalation of gasoline vapors (GV) is associated with developing various pathologies. Particularly, oil refinery and gas station workers are at a greater risk of developing lung cancer, kidney cancer, bladder cancer, and hematological disorders, including acute myeloid leukemia. Therefore, preventing the harmful effects of GV and alleviating their consequences appear to be important and timely issues. In this study, we investigated the potential of vitamin D3, turmeric powder, and their combination to ameliorate the toxicity of gasoline fumes in rats. Separate groups of animals fed with a standard rodent diet, with or without the supplementation of vitamin D3 (750 IU/kg body weight) and/or turmeric powder (0.5%, w/w, in food), were untreated or treated with GV (11.5 ± 1.3 cm3/h/m3/day) for 30, 60, or 90 days. Changes in the body weight were monitored weekly. Histological, biochemical, and hematological parameters were determined at the end of each treatment period. While the exposure of rats to GV resulted in a time-dependent reduction in body weight, supplementation with vitamin D3, but not with turmeric root powder or their combination, partially prevented weight loss. Macroscopical and histological analyses showed pronounced time-dependent changes in the organs and tissues of GV-treated rats. These included alveolar wall collapse in the lungs, the destruction of the lobular structure and hepatocytolysis in the liver, the shrinkage and fragmentation of glomeruli in the kidneys, and the disorganization of the lymphoid follicles in the spleen. However, co-treatment with the nutritional supplements tested, especially vitamin D3, noticeably alleviated the above conditions. This was accompanied by a significant improvement in the blood chemistry and hematological parameters. Collectively, our results demonstrate that the harmful effects of environmental exposure to GV can be reduced upon supplementation of vitamin D3. The fact that the protective activity of vitamin D3 alone was higher than that of turmeric root powder or the combined treatment suggests that combinations of these supplements may not always be more beneficial than each agent applied separately.

Emerging perspectives: unraveling the anticancer potential of vitamin D3

Vitamin D3, a fat-soluble vitamin known for its critical function in calcium homeostasis and bone health, is gaining interest for its anticancer properties. Observational studies have suggested a negative relationship between vitamin D levels and the incidence of some malignancies throughout the years, prompting substantial investigation to find its anticancer effects. The purpose of this comprehensive review is to investigate the diverse function of vitamin D3 in cancer prevention and therapy. We explored the molecular mechanism underlying its effects on cancer cells, which range from cell cycle control and death to angiogenesis and immune response modulation. Insights from in vitro and in vivo studies provide valuable evidence supporting its anticancer potential. Furthermore, we look at epidemiological and clinical studies that investigate the relationship between vitamin D3 levels and cancer risk or treatment results. Vitamin D3 supplementation's safety profile and cost-effectiveness increase its attractiveness as an adjuvant therapy in conjunction with traditional treatment regimens. Our critical review of the current literature provides an in-depth understanding of vitamin D3's anticancer effect, covering the obstacles and possibilities in realizing its promise for cancer prevention and therapy. The findings of this study might pave the way for the development of innovative treatment techniques that take use of the advantages of vitamin D3 to fight cancer and improve patient care. As research progresses, a better understanding of vitamin D3's anticancer processes will surely simplify its incorporation into personalized cancer care techniques, hence enhancing patient outcomes in the battle against cancer.

Targeted inhibition of the HNF1A/SHH axis by triptolide overcomes paclitaxel resistance in non-small cell lung cancer

Paclitaxel resistance is associated with a poor prognosis in non-small cell lung cancer (NSCLC) patients, and currently, there is no promising drug for paclitaxel resistance. In this study, we investigated the molecular mechanisms underlying the chemoresistance in human NSCLC-derived cell lines. We constructed paclitaxel-resistant NSCLC cell lines (A549/PR and H460/PR) by long-term exposure to paclitaxel. We found that triptolide, a diterpenoid epoxide isolated from the Chinese medicinal herb Tripterygium wilfordii Hook F, effectively enhanced the sensitivity of paclitaxel-resistant cells to paclitaxel by reducing ABCB1 expression in vivo and in vitro. Through high-throughput sequencing, we identified the SHH-initiated Hedgehog signaling pathway playing an important role in this process. We demonstrated that triptolide directly bound to HNF1A, one of the transcription factors of SHH, and inhibited HNF1A/SHH expression, ensuing in attenuation of Hedgehog signaling. In NSCLC tumor tissue microarrays and cancer network databases, we found a positive correlation between HNF1A and SHH expression. Our results illuminate a novel molecular mechanism through which triptolide targets and inhibits HNF1A, thereby impeding the activation of the Hedgehog signaling pathway and reducing the expression of ABCB1. This study suggests the potential clinical application of triptolide and provides promising prospects in targeting the HNF1A/SHH pathway as a therapeutic strategy for NSCLC patients with paclitaxel resistance. Schematic diagram showing that triptolide overcomes paclitaxel resistance by mediating inhibition of the HNF1A/SHH/ABCB1 axis.

Recent Contributions of Mass Spectrometry-Based "Omics" in the Studies of Breast Cancer

Breast cancer (BC) is one of the most heterogeneous groups of cancer. As every biotype of BC is unique and presents a particular "omic" signature, they are increasingly characterized nowadays with novel mass spectrometry (MS) strategies. BC therapeutic approaches are primarily based on the two features of human epidermal growth factor receptor 2 (HER2) and estrogen receptor (ER) positivity. Various strategic MS implementations are reported in studies of BC also involving data independent acquisitions (DIAs) of MS which report novel differential proteomic, lipidomic, proteogenomic, phosphoproteomic, and metabolomic characterizations associated with the disease and its therapeutics. Recently many "omic" studies have aimed to identify distinct subsidiary biotypes for diagnosis, prognosis, and targets of treatment. Along with these, drug-induced-resistance phenotypes are characterized by "omic" changes. These identifying aspects of the disease may influence treatment outcomes in the near future. Drug quantifications and characterizations are also done regularly and have implications in therapeutic monitoring and in drug efficacy assessments. We report these studies, mentioning their implications toward the understanding of BC. We briefly provide the MS instrumentation principles that are adopted in such studies as an overview with a brief outlook on DIA-MS strategies. In all of these, we have chosen a model cancer for its revelations through MS-based "omics".

Antioxidant curcumin induces oxidative stress to kill tumor cells (Review)

Curcumin is a plant polyphenol in turmeric root and a potent antioxidant. It binds to antioxidant response elements for gene regulation by nuclear factor erythroid 2-related factor 2, thereby suppressing reactive oxygen species (ROS) and exerting anti-inflammatory, anti-infective and other pharmacological effects. Of note, curcumin induces oxidative stress in tumors. It binds to several enzymes in tumors, such as carbonyl reductases, glutathione S-transferase P1 and nicotinamide adenine dinucleotide phosphate to induce mitochondrial damage, increase ROS production and ultimately induce tumor cell death. However, the instability and poor pharmacokinetic profile of curcumin in vivo limit its clinical application. Therefore, the effects of curcumin in vivo may be enhanced through its combination with drugs, derivative development and nanocarriers. In the present review, the mechanisms of curcumin that induce tumor cell death through oxidative stress are discussed. In addition, the methods used to enhance the antitumor activity of curcumin are described. Finally, the existing knowledge on the functions of curcumin in tumors, particularly in terms of oxidative stress, are summarized to facilitate future curcumin research.

Curcumin for Treating Breast Cancer: A Review of Molecular Mechanisms, Combinations with Anticancer Drugs, and Nanosystems

Breast cancer (BC) has become the fifth most prevalent cause of cancer-related morbidity, attracting significant attention from researchers due to its heightened malignancy and drug resistance. Conventional chemotherapy approaches have proven inadequate in addressing all BC subtypes, highlighting the urgent need for novel therapeutic approaches or drugs. Curcumin (CUR), a phytochemical derived from Curcuma longa (turmeric), has shown substantial potential in inhibiting BC cell migration, metastasis, and proliferation. However, the use of CUR in this context comes with challenges due to its dynamic and easily degradable nature, poor aqueous solubility, low bioavailability, rapid metabolism, and swift systemic elimination, collectively limiting its clinical applications. As such, we provide an overview of the properties, synthesis, and characterization of the hybridization of CUR and its analogue with chemo-drug building blocks. We reviewed research from the last five years on CUR's biogenesis with respect to the regulation of BC, revealing that CUR participates in arresting BC cells in the cell cycle and significantly induces apoptosis in BC cells. Information on the chemotherapeutic and antitumor mechanisms of CUR in BC, including regulation of the cell cycle, increased cell apoptosis, and inhibition of multidrug resistance (MDR), was compiled. Additionally, we provide an overview of CUR loaded into nanomaterials that are cotreated with other chemotherapeutic drugs, such as paclitaxel, thymoquinone, and tamoxifen. In this review, we discuss different types of nanoparticles that can be used for CUR delivery, such as polymeric nanoparticles, carbon nanotubes, and liposomes. By comparing the size, entrapment efficiency, drug-loading capacity, release time, biocompatibility, pharmaceutical scale, and reproducibility of various nanomaterials, we aimed to determine which formulations are better suited for loading CUR or its analogue. Ultimately, this review is expected to offer inspiring ideas, promising strategies, and potential pathways for developing advanced anti-BC strategy nanosystems in clinical practice.

Targeted therapies of curcumin focus on its therapeutic benefits in cancers and human health: Molecular signaling pathway-based approaches and future perspectives

The curry powder spices turmeric (Curcuma longa L.), which contains curcumin (diferuloylmethane), an orange-yellow chemical. Polyphenols are the most commonly used sources of curcumin. It combats oxidative stress and inflammation in diseases, such as hyperlipidemia, metabolic syndrome, arthritis, and depression. Most of these benefits are due to their anti-inflammatory and antioxidant properties. Curcumin consumption leads to decreased bioavailability, resulting in limited absorption, quick metabolism, and quick excretion, which hinders health improvement. Numerous factors can increase its bioavailability. Piperine enhances bioavailability when combined with curcumin in a complex. When combined with other enhancing agents, curcumin has a wide spectrum of health benefits. This review evaluates the therapeutic potential of curcumin with a specific emphasis on its approach based on molecular signaling pathways. This study investigated its influence on the progression of cancer, inflammation, and many health-related mechanisms, such as cell proliferation, apoptosis, and metastasis. Curcumin has a significant potential for the prevention and treatment of various diseases. Curcumin modulates several biochemical pathways and targets involved in cancer growth. Despite its limited tissue accumulation and bioavailability when administered orally, curcumin has proven useful. This review provides an in-depth analysis of curcumin's therapeutic applications, its molecular signaling pathway-based approach, and its potential for precision medicine in cancer and human health.

The mechanisms of multidrug resistance of breast cancer and research progress on related reversal agents

Chemotherapy is the mainstay in the treatment of breast cancer. However, many drugs that are commonly used in clinical practice have a high incidence of side effects and multidrug resistance (MDR), which is mainly caused by overexpression of drug transporters and related enzymes in breast cancer cells. In recent years, researchers have been working hard to find newer and safer drugs to overcome MDR in breast cancer. In this review, we provide the molecule mechanism of MDR in breast cancer, categorize potential lead compounds that inhibit single or multiple drug transporter proteins, as well as related enzymes. Additionally, we have summarized the structure-activity relationship (SAR) based on potential breast cancer MDR modulators with lower side effects. The development of novel approaches to suppress MDR is also addressed. These lead compounds hold great promise for exploring effective chemotherapy agents to overcome MDR, providing opportunities for curing breast cancer in the future.

Breast cancer: miRNAs monitoring chemoresistance and systemic therapy

With a high mortality rate that accounts for millions of cancer-related deaths each year, breast cancer is the second most common malignancy in women. Chemotherapy has significant potential in the prevention and spreading of breast cancer; however, drug resistance often hinders therapy in breast cancer patients. The identification and the use of novel molecular biomarkers, which can predict response to chemotherapy, might lead to tailoring breast cancer treatment. In this context, accumulating research has reported microRNAs (miRNAs) as potential biomarkers for early cancer detection, and are conducive to designing a more specific treatment plan by helping analyze drug resistance and sensitivity in breast cancer treatment. In this review, miRNAs are discussed in two alternative ways-as tumor suppressors to be used in miRNA replacement therapy to reduce oncogenesis and as oncomirs to lessen the translation of the target miRNA. Different miRNAs like miR-638, miR-17, miR-20b, miR-342, miR-484, miR-21, miR-24, miR-27, miR-23 and miR-200 are involved in the regulation of chemoresistance through diverse genetic targets. For instance, tumor-suppressing miRNAs like miR-342, miR-16, miR-214, and miR-128 and tumor-promoting miRNAs like miR101 and miR-106-25 cluster regulate the cell cycle, apoptosis, epithelial to mesenchymal transition and other pathways to impart breast cancer drug resistance. Hence, in this review, we have discussed the significance of miRNA biomarkers that could assist in providing novel therapeutic targets to overcome potential chemotherapy resistance to systemic therapy and further facilitate the design of tailored therapy for enhanced efficacy against breast cancer.

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.

Role of the Dietary Phytochemical Curcumin in Targeting Cancer Cell Signalling Pathways

The diarylheptanoid curcumin [(1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)hepta-1,6-diene-3,5-dione] is one of the phenolic pigments responsible for the yellow colour of turmeric (Curcuma longa L.). This phytochemical has gained much attention in recent years due to its therapeutic potential in cancer. A range of drug delivery approaches have been developed to optimise the pharmacokinetic profile of curcumin and ensure that it reaches its target sites. Curcumin exhibits numerous biological effects, including anti-inflammatory, cardioprotective, antidiabetic, and anti-aging activities. It has also been extensively studied for its role as a cancer chemopreventive and anticancer agent. This review focusses on the role of curcumin in targeting the cell signalling pathways involved in cancer, particularly via modulation of growth factors, transcription factors, kinases and other enzymes, pro-inflammatory cytokines, and pro-apoptotic and anti-apoptotic proteins. It is hoped that this study will help future work on the potential of curcumin to fight cancer.

Combination Chemotherapy with Selected Polyphenols in Preclinical and Clinical Studies-An Update Overview

This review article describes studies published over the past five years on the combination of polyphenols, which are the most studied in the field of anticancer effects (curcumin, quercetin, resveratrol, epigallocatechin gallate, and apigenin) and chemotherapeutics such as cisplatin, 5-fluorouracil, oxaliplatin, paclitaxel, etc. According to WHO data, research has been limited to five cancers with the highest morbidity rate (lung, colorectal, liver, gastric, and breast cancer). A systematic review of articles published in the past five years (from January 2018 to January 2023) was carried out with the help of all Web of Science databases and the available base of clinical studies. Based on the preclinical studies presented in this review, polyphenols can enhance drug efficacy and reduce chemoresistance through different molecular mechanisms. Considering the large number of studies, curcumin could be a molecule in future chemotherapy cocktails. One of the main problems in clinical research is related to the limited bioavailability of most polyphenols. The design of a new co-delivery system for drugs and polyphenols is essential for future clinical research. Some polyphenols work in synergy with chemotherapeutic drugs, but some polyphenols can act antagonistically, so caution is always required.

Targeting aldehyde dehydrogenase enzymes in combination with chemotherapy and immunotherapy: An approach to tackle resistance in cancer cells

Modern cancer chemotherapy originated in the 1940s, and since then, many chemotherapeutic agents have been developed. However, most of these agents show limited response in patients due to innate and acquired resistance to therapy, which leads to the development of multi-drug resistance to different treatment modalities, leading to cancer recurrence and, eventually, patient death. One of the crucial players in inducing chemotherapy resistance is the aldehyde dehydrogenase (ALDH) enzyme. ALDH is overexpressed in chemotherapy-resistant cancer cells, which detoxifies the generated toxic aldehydes from chemotherapy, preventing the formation of reactive oxygen species and, thus, inhibiting the induction of oxidative stress and the stimulation of DNA damage and cell death. This review discusses the mechanisms of chemotherapy resistance in cancer cells promoted by ALDH. In addition, we provide detailed insight into the role of ALDH in cancer stemness, metastasis, metabolism, and cell death. Several studies investigated targeting ALDH in combination with other treatments as a potential therapeutic regimen to overcome resistance. We also highlight novel approaches in ALDH inhibition, including the potential synergistic employment of ALDH inhibitors in combination with chemotherapy or immunotherapy against different cancers, including head and neck, colorectal, breast, lung, and liver.

Curcumin: a natural organic component that plays a multi-faceted role in ovarian cancer

Curcumin, a natural organic component obtained from Curcuma longa's rhizomes, shows abundant anti-tumor, antioxidant and anti-inflammatory pharmacological activities, among others. Notably the anti-tumor activity has aroused widespread attention from scholars worldwide. Numerous studies have reported that curcumin can delay ovarian cancer (OC), increase its sensitivity to chemotherapy, and reduce chemotherapy drugs' side effects. It has been shown considerable anticancer potential by promoting cell apoptosis, suppressing cell cycle progression, inducing autophagy, inhibiting tumor metastasis, and regulating enzyme activity. With an in-depth study of curcumin's anti-OC mechanism, its clinical application will have broader prospects. This review summarizes the latest studies on curcumin's anti-OC activities, and discusses the specific mechanism, hoping to provide references for further research and applications.

ATP-binding cassette efflux transporters and MDR in cancer

Of the many known multidrug resistance (MDR) mechanisms, ATP-binding cassette (ABC) transporters expelling drug molecules out of cells is a major factor limiting the efficacy of present-day anticancer drugs. In this review, we highlights updated information on the structure, function, and regulatory mechanisms of major MDR-related ABC transporters, such as P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1), and breast cancer resistance protein (BCRP), and the effect of modulators on their functions. We also provide focused information on different modulators of ABC transporters that could be utilized against the emerging MDR crisis in cancer treatment. Finally, we discuss the importance of ABC transporters as therapeutic targets in light of future strategic planning for translating ABC transporter inhibitors into clinical practice.

Anti-lung cancer effect of paclitaxel solid lipid nanoparticles delivery system with curcumin as co-loading partner in vitro and in vivo

The main aim of this study was to improve the therapeutic potential of a paclitaxel (PTX) and curcumin (CU) combination regimen using solid lipid nanoparticles (SLNs). PTX and CU were successfully co-encapsulated at a predetermined ratio in SLNs (PC-SLNs) with high encapsulation efficiency (CU: 97.6%, PTX: 95.8%), appropriate particle size (121.8 ± 1.69 nm), small PDI (0.267 ± 0.023), and negative zeta potential (–30.4 ± 1.25 mV). Compared with PTX or the combination of CU and PTX (CU + PTX), PC-SLNs can greatly reduce the dose of PTX while still achieving the same therapeutic effect on four cancer cell lines, among which the inhibitory effect on A549 lung cancer cells was the strongest. PC-SLNs improved the area under the curve (CU: 1.40-fold; PTX: 2.88-fold), prolonged the residence time (CU: 6.94-fold; PTX: 2.51-fold), and increased the half-life (CU: 5.62-fold; PTX: 6.46-fold), achieving long circulation. PC-SLNs were used to treat lung cancer in a nude mouse xenograft tumor model and the tumor suppression rate reached 78.42%, while those of PTX and (CU + PTX) were 40.53% and 51.56%, respectively. As PC-SLNs can prevent P-glycoprotein efflux, reverse MDR and downregulate the NF-κB pathway. PC-SLNs are a potential antineoplastic agent that is more effective and less toxic in treating lung cancer.

ALDH1: A potential therapeutic target for cancer stem cells in solid tumors

Solid tumors can be divided into benign solid tumors and solid malignant tumors in the academic community, among which malignant solid tumors are called cancers. Cancer is the second leading cause of death in the world, and the global incidence of cancer is increasing yearly New cancer patients in China are always the first. After the concept of stem cells was introduced in the tumor community, the CSC markers represented by ALDH1 have been widely studied due to their strong CSC cell characteristics and potential to be the driving force of tumor metastasis. In the research results in the past five years, it has been found that ALDH1 is highly expressed in various solid cancers such as breast cancer, lung cancer, colorectal cancer, liver cancer, gastric cancer, cervical cancer, esophageal cancer, ovarian cancer, head,and neck cancer. ALDH1 can activate and transform various pathways (such as the USP28/MYC signaling pathway, ALDH1A1/HIF-1α/VEGF axis, wnt/β-catenin signaling pathway), as well as change the intracellular pH value to promote formation and maintenance, resulting in drug resistance in tumors. By targeting and inhibiting ALDH1 in tumor stem cells, it can enhance the sensitivity of drugs and inhibit the proliferation, differentiation, and metastasis of solid tumor stem cells to some extent. This review discusses the relationship and pathway of ALDH1 with various solid tumors. It proposes that ALDH1 may serve as a diagnosis and therapeutic target for CSC, providing new insights and new strategies for reliable tumor treatment.

Targeting Breast Cancer-Derived Stem Cells by Dietary Phytochemicals: A Strategy for Cancer Prevention and Treatment

Breast cancer is heterogeneous disease with variable prognosis and therapeutic response. Approximately, 70% of diagnosed breast cancer represents the luminal A subtype. This subpopulation has a fair prognosis with a lower rate of relapse than the other clinical subtypes. Acquisition of stemness in luminal A subtype modifies the phenotype plasticity to accomplish increased aggressiveness and therapeutic resistance. Therefore, targeting luminal A-derived breast cancer stem cells (BCSCs) could be a promising strategy for its prevention and treatment. Extensive studies reveal that dietary phytochemicals have the potential to target BCSCs by modulating the molecular and signal transduction pathways. Dietary phytochemicals alone or in combination with standard therapeutic modalities exert higher efficacy in targeting BCSCs through changes in stemness, self-renewal properties and hypoxia-related factors. These combinations offer achieving higher radio- and chemo- sensitization through alteration in the key signaling pathways such as AMPK, STAT3, NF-ĸB, Hedgehog, PI3K/Akt/mTOR, Notch, GSK3β, and Wnt related to cancer stemness and drug resistance. In this review, we highlight the concept of targeting luminal A-derived BCSCs with dietary phytochemicals by summarizing the pathways and underlying mechanism(s) involved during therapeutic resistance.

Electrochemical Behavior and Direct Quantitative Determination of Paclitaxel

The electrochemical behavior and direct quantitative determination of paclitaxel, a poorly soluble drug made into microemulsion, were researched by cyclic voltammetry in acetate buffer solutions (pH = 4.0) at a glassy carbon electrode. The results show that the oxidation process is irreversible and controlled by diffusion. Moreover, the effects of anodic peak current (Ipa), anodic peak potential, scan rate, pH, and the electrochemical redox mechanism have been studied. The anodic peak current varied linearly with paclitaxel concentration in the range of 5 × 10-5 mol/L to 5 × 10-4 mol/L, and the detection limit was 9.15 × 10-8 mol/L. The results of RSD (0.90%) and recovery (99.22%-101.69%) were obtained. Additionally, it has been proved that one electron and one proton are involved in the electrochemical redox process. The present research has been successfully used to determine paclitaxel in pure and real samples, which further supported the electrochemical behavior investigation of paclitaxel and direct determination of micro-emulsion.

Noncoding RNAs and their therapeutics in paclitaxel chemotherapy: Mechanisms of initiation, progression, and drug sensitivity

The identification of agents that can reverse drug resistance in cancer chemotherapy, and enhance the overall efficacy is of great interest. Paclitaxel (PTX) belongs to taxane family that exerts an antitumor effect by stabilizing microtubules and inhibiting cell cycle progression. However, PTX resistance often develops in tumors due to the overexpression of drug transporters and tumor-promoting pathways. Noncoding RNAs (ncRNAs) are modulators of many processes in cancer cells, such as apoptosis, migration, differentiation, and angiogenesis. In the present study, we summarize the effects of ncRNAs on PTX chemotherapy. MicroRNAs (miRNAs) can have opposite effects on PTX resistance (stimulation or inhibition) via influencing YES1, SK2, MRP1, and STAT3. Moreover, miRNAs modulate the growth and migration rates of tumor cells in regulating PTX efficacy. PIWI-interacting RNAs, small interfering RNAs, and short-hairpin RNAs are other members of ncRNAs regulating PTX sensitivity of cancer cells. Long noncoding RNAs (LncRNAs) are similar to miRNAs and can modulate PTX resistance/sensitivity by their influence on miRNAs and drug efflux transport. The cytotoxicity of PTX against tumor cells can also be affected by circular RNAs (circRNAs) and limitation is that oncogenic circRNAs have been emphasized and experiments should also focus on onco-suppressor circRNAs.

Piperlongumine induces ROS mediated apoptosis by transcriptional regulation of SMAD4/P21/P53 genes and synergizes with doxorubicin in osteosarcoma cells

Piperlongumine is a herbal drug, with well-known anti-microbial and anti-neoplastic properties. The anti-carcinogenic potential of piperlongumine has been extensively explored for breast, colorectal, lungs, pancreatic, prostate, and oral carcinoma. However, a few numbers of studies are available on its bio-activity in osteosarcoma. Therefore, the present study aimed at exploring the therapeutic potential and possible mechanisms of action of piperlongumine in three human osteosarcoma cell lines in-vitro. The cytotoxicity of piperlongumine was determined by MTT assay, which shows dose and time-dependent inhibition of MG-63, 143B and KHOS/NP cells. Piperlongumine arrest the cells in G2/M phase of cell cycle and increases reactive oxygen species production, which possibly leads to lethal oxidative stress and apoptosis. Piperlongumine treatment significantly upregulated the expression of genes BAX, P21, P53, and SMAD4; while the BCL-2, SURVIVIN, TNFA, and NFKB genes expression was found down-regulated. Furthermore, piperlongumine exposure inhibited the migration of osteosarcoma cells as the expression of migration marker genes CDH2, CTNNB1, FN1, and TWIST were found to be down-regulated. The drug combination studies show the synergistic effect of piperlongumine with the conventional chemotherapeutic drug doxorubicin in osteosarcoma cells. Taken together, the above results suggest that PL displays anticancer properties against osteosarcoma and can be used as a therapeutic agent for osteosarcoma treatment in clinical settings.

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.

Combinations of Calcitriol with Anticancer Treatments for Breast Cancer: An Update

Preclinical, clinical, and epidemiological studies indicate that vitamin D3 (VD) deficiency is a risk factor for the development of breast cancer. Underlying mechanisms include the ability of calcitriol to induce cell differentiation, inhibit oncogenes expression, and modify different signaling pathways involved in the control of cell proliferation. In addition, calcitriol combined with different kinds of antineoplastic drugs has been demonstrated to enhance their beneficial effects in an additive or synergistic fashion. However, a recognized adjuvant regimen based on calcitriol for treating patients with breast cancer has not yet been fully established. Accordingly, in the present work, we review and discuss the preclinical and clinical studies about the combination of calcitriol with different oncological drugs, aiming to emphasize its main therapeutic benefits and opportunities for the treatment of this pathology.

Causal Links between Hypovitaminosis D and Dysregulation of the T Cell Connection of Immunity Associated with Obesity and Concomitant Pathologies

Subclinical inflammation in morbid obesity is associated with immune activation and the development of concomitant diseases. Impaired immune homeostasis and immune cell dysregulation in adipose tissue are associated with phenotypic and functional changes in the pool of T lymphocytes and the development of chronic hypovitaminosis D. Low vitamin D levels in obesity lead to the activation, proliferation and production of pro-inflammatory mediators by T cells. Hypovitaminosis D is the cause of a decrease in the functional potential of regulatory and anti-inflammatory lymphocytes and the maintenance of the inflammatory response. The exact molecular genetic mechanisms of the effect of vitamin D on T lymphocytes have not been fully elucidated. Therefore, uncovering the functional role of T cells and their relationship to vitamin D homeostasis in the context of obesity development may contribute to the development of new pathogenetic methods for clinical prediction of the risk of metabolic, oncologic, autoimmune and infectious complications. The review presents the molecular genetic mechanisms of the effect of vitamin D on adipose tissue resident T lymphocytes and the characteristics of vitamin D receptor expression, and analyzes the phenotypic and functional characteristics of potentially pathogenic T lymphocytes in relation to the development of obesity and its associated complications.

Effects and mechanisms of dietary bioactive compounds on breast cancer prevention

Breast cancer (BC) is the most often diagnosed cancer among females globally and has become an increasing global health issue over the last decades. Despite the substantial improvement in screening methods for initial diagnosis, effective therapy remains lacking. Still, there has been high recurrence and disease progression after treatment of surgery, endocrine therapy, chemotherapy, and radiotherapy. Considering this view, there is a crucial requirement to develop safe, freely accessible, and effective anticancer therapy for BC. The dietary bioactive compounds as auspicious anticancer agents have been recognized to be active and their implications in the treatment of BC with negligible side effects. Hence, this review focused on various dietary bioactive compounds as potential therapeutic agents in the prevention and treatment of BC with the mechanisms of action. Bioactive compounds have chemo-preventive properties as they inhibit the proliferation of cancer cells, downregulate the expression of estrogen receptors, and cell cycle arrest by inducing apoptotic settings in tumor cells. Therapeutic drugs or natural compounds generally incorporate engineered nanoparticles with ideal sizes, shapes, and enhance their solubility, circulatory half-life, and biodistribution. All data of in vitro, in vivo, and clinical studies of dietary bioactive compounds and their impact on BC were collected from Science Direct, PubMed, and Google Scholar. The data of chemopreventive and anticancer activity of dietary bioactive compounds were collected and orchestrated in a suitable place in the review. These shreds of data will be extremely beneficial to recognize a series of additional diet-derived bioactive compounds to treat BC with the lowest side effects.

Luteolin Inhibits Breast Cancer Stemness and Enhances Chemosensitivity through the Nrf2-Mediated Pathway

Cancer stem cells (CSCs) are subpopulations of tumor masses with unique abilities in self-renewal, stemness maintenance, drug resistance, and the promotion of cancer recurrence. Recent studies have suggested that breast CSCs play essential roles in chemoresistance. Therefore, new agents that selectively target such cells are urgently required. Reactive oxygen species (ROS)-producing enzymes are the reason for an elevated tumor oxidant status. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcriptional factor, which upon detecting cellular oxidative stress, binds to the promoter region of antioxidant genes. By triggering a cytoprotective response, Nrf2 maintains cellular redox status. Cripto-1 participates in the self-renewal of CSCs. Herein, luteolin, a flavonoid found in Taraxacum officinale extract, was determined to inhibit the expressions of stemness-related transcriptional factors, the ATP-binding cassette transporter G2 (ABCG2), CD44, aldehyde dehydrogenase 1 activity as well as the sphere formation properties of breast CSCs. Furthermore, luteolin suppressed the protein expressions of Nrf2, heme oxygenase 1 (HO-1), and Cripto-1 which have been determined to contribute critically to CSC features. The combination of luteolin and the chemotherapeutic drug, Taxol, resulted in enhanced cytotoxicity to breast cancer cells. These findings suggest that luteolin treatment significantly attenuated the hallmarks of breast cancer stemness by downregulating Nrf2-mediated expressions. Luteolin constitutes a potential agent for use in cancer stemness-targeted breast cancer treatments.

Traditional Chinese medicine reverses cancer multidrug resistance and its mechanism

Chemotherapy is one of the most commonly used clinical treatments among the currently available cancer therapies. However, the phenomenon of Multidrug resistance (MDR) has become a challenge in the treatment process, weakening the impact of chemotherapy. Extensive research on elucidating the development of cancer MDR has identified the following mechanisms that play a critical role in the development of several MDR reversal agents: abnormal expression of cell membrane transporters, adaptation of cancer cells to the microenvironment, regulation of hypoxia, repair of DNA damage and reduction of apoptosis, the enhancement of the EMT process, the existence of cancer stem cells (CSCs), and the abnormal activation of key signaling pathways. However, they failed to demonstrate significant efficacy due to severe side effects during their clinical trials. Traditional Chinese medicines (TCMs) are known to play an important anti-cancer role since they have low toxicity, high efficacy, and safety and can reverse MDR. TCMs reversal agents can be divided into Chinese medicine monomers, synthetic monomers, analogs, or derivatives. Several studies have shown that TCMs can effectively overcome cancer MDR and can be effectively used for treating cancer patients.

The Role of Curcumin in Cancer Treatment

Curcumin is a polyphenol extracted from the rhizomes of the turmeric plant, Curcuma longa which has anti-inflammatory, and anticancer properties. Chronic inflammation is associated with the development of cancer. Curcumin acts on the regulation of various immune modulators, including cytokines, cyclooxygenase-2 (COX-2), and reactive oxygen species (ROS), which partly explains its anticancer effects. It also takes part in the downregulation of growth factors, protein kinases, oncogenic molecules and various signaling pathways, such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), c-Jun N-terminal kinase (JNK) and signal transducer and activator of transcription 3 (STAT3) signaling. Clinical trials of curcumin have been completed or are ongoing for various types of cancer. This review presents the molecular mechanisms of curcumin in different types of cancer and the evidence from the most recent clinical trials.

In Vivo Efficacy and Toxicity of Curcumin Nanoparticles in Breast Cancer Treatment: A Systematic Review

Breast cancer is one of the most prevalent types of malignant tumors in the world, resulting in a high incidence of death. The development of new molecules and technologies aiming to apply more effective and safer therapy strategies has been intensively explored to overcome this situation. The association of nanoparticles with known antitumor compounds (including plant-derived molecules such as curcumin) has been considered an effective approach to enhance tumor growth suppression and reduce adverse effects. Therefore, the objective of this systematic review was to summarize published data regarding evaluations about efficacy and toxicity of curcumin nanoparticles (Cur-NPs) in in vivo models of breast cancer. The search was carried out in the databases: CINAHL, Cochrane, LILACS, Embase, FSTA, MEDLINE, ProQuest, BSV regional portal, PubMed, ScienceDirect, Scopus, and Web of Science. Studies that evaluated tumor growth in in vivo models of breast cancer and showed outcomes related to Cur-NP treatment (without association with other antitumor molecules) were included. Of the 528 initially gathered studies, 26 met the inclusion criteria. These studies showed that a wide variety of NP platforms have been used to deliver curcumin (e.g., micelles, polymeric, lipid-based, metallic). Attachment of poly(ethylene glycol) chains (PEG) and active targeting moieties were also evaluated. Cur-NPs significantly reduced tumor volume/weight, inhibited cancer cell proliferation, and increased tumor apoptosis and necrosis. Decreases in cancer stem cell population and angiogenesis were also reported. All the studies that evaluated toxicity considered Cur-NP treatment to be safe regarding hematological/biochemical markers, damage to major organs, and/or weight loss. These effects were observed in different in vivo models of breast cancer (e.g., estrogen receptor-positive, triple-negative, chemically induced) showing better outcomes when compared to treatments with free curcumin or negative controls. This systematic review supports the proposal that Cur-NP is an effective and safe therapeutic approach in in vivo models of breast cancer, reinforcing the currently available evidence that it should be further analyzed in clinical trials for breast cancer treatments.

Polychemotherapy with Curcumin and Doxorubicin via Biological Nanoplatforms: Enhancing Antitumor Activity

Doxorubicin (DOX) is a well-known chemotherapeutic agent extensively applied in the field of cancer therapy. However, similar to other chemotherapeutic agents such as cisplatin, paclitaxel, docetaxel, etoposide and oxaliplatin, cancer cells are able to obtain chemoresistance that limits DOX efficacy. In respect to dose-dependent side effect of DOX, enhancing its dosage is not recommended for effective cancer chemotherapy. Therefore, different strategies have been considered for reversing DOX resistance and diminishing its side effects. Phytochemical are potential candidates in this case due to their great pharmacological activities. Curcumin is a potential antitumor phytochemical isolated from Curcuma longa with capacity of suppressing cancer metastasis and proliferation and affecting molecular pathways. Experiments have demonstrated the potential of curcumin for inhibiting chemoresistance by downregulating oncogene pathways such as MMP-2, TGF-β, EMT, PI3K/Akt, NF-κB and AP-1. Furthermore, coadministration of curcumin and DOX potentiates apoptosis induction in cancer cells. In light of this, nanoplatforms have been employed for codelivery of curcumin and DOX. This results in promoting the bioavailability and internalization of the aforementioned active compounds in cancer cells and, consequently, enhancing their antitumor activity. Noteworthy, curcumin has been applied for reducing adverse effects of DOX on normal cells and tissues via reducing inflammation, oxidative stress and apoptosis. The current review highlights the anticancer mechanism, side effects and codelivery of curcumin and DOX via nanovehicles.

Chemotherapeutic efficacy of curcumin and resveratrol against cancer: Chemoprevention, chemoprotection, drug synergism and clinical pharmacokinetics

The frequent inefficiency of conventional cancer therapies due to drug resistance, non-targeted drug delivery, chemotherapy-associated toxic side effects turned the focus to bioactive phytochemicals. In this context, curcumin and resveratrol have emerged as potent chemopreventive and chemoprotective compounds modulating apoptotic and autophagic cell death pathways in cancer in vitro and in vivo. As synergistic agents in combination with clinically established anticancer drugs, the enhanced anticancer activity at reduced chemotherapy-associated toxicity towards normal organs can be explained by improved pharmacokinetics, pharmacodynamics, bioavailability and metabolism. With promising preclinical and clinical applications, the design of drug-loaded nanoparticles, nanocarriers, liposomes and micelles have gained much attention to improve target specificity and drug efficacy. The present review focuses on the molecular modes of chemoprevention, chemoprotection and drug synergism with special emphasis to preclinical and clinical applications, pharmacokinetics, pharmacodynamics and advanced drug delivery methods for the development of next-generation personalized cancer therapeutics.

Flaming the fight against cancer cells: the role of microRNA-93

There have been attempts to develop novel anti-tumor drugs in cancer therapy. Although satisfying results have been observed at a consequence of application of chemotherapeutic agents, the cancer cells are capable of making resistance into these agents. This has forced scientists into genetic manipulation as genetic alterations are responsible for generation of a high number of cancer cells. MicroRNAs (miRs) are endogenous, short non-coding RNAs that affect target genes at the post-transcriptional level. Increasing evidence reveals the potential role of miRs in regulation of biological processes including angiogenesis, metabolism, cell proliferation, cell division, and cell differentiation. Abnormal expression of miRs is associated with development of a number of pathologic events, particularly cancer. MiR-93 plays a significant role in both physiological and pathological mechanisms. At the present review, we show how this miR dually affects the proliferation and invasion of cancer cells. Besides, we elucidate the oncogenesis or oncosuppressor function of miR-93.

Curcumin in cancer therapy: A novel adjunct for combination chemotherapy with paclitaxel and alleviation of its adverse effects

Dealing with cancer is of importance due to enhanced incidence rate of this life-threatening disorder. Chemotherapy is an ideal candidate in overcoming and eradication of cancer. To date, various chemotherapeutic agents have been applied in cancer therapy and paclitaxel (PTX) is one of them. PTX is a key member of taxane family with potential anti-tumor activity against different cancers. Notably, PTX has demonstrated excellent proficiency in elimination of cancer in clinical trials. This chemotherapeutic agent is isolated from Taxus brevifolia, and is a tricyclic diterpenoid. However, resistance of cancer cells into PTX chemotherapy has endangered its efficacy. Besides, administration of PTX is associated with a number of side effects such as neurotoxicity, hepatotoxicity, cardiotoxicity and so on, demanding novel strategies in obviating PTX issues. Curcumin is a pharmacological compound with diverse therapeutic effects including anti-tumor, anti-oxidant, anti-inflammatory, anti-diabetic and so on. In the current review, we demonstrate that curcumin, a naturally occurring nutraceutical compound is able to enhance anti-tumor activity of PTX against different cancers. Besides, curcumin administration reduces adverse effects of PTX due to its excellent pharmacological activities. These topics are discussed with an emphasis on molecular pathways to provide direction for further studies in revealing other signaling networks.

Crosstalk between aldehyde dehydrogenase-1 and chemoresistance in breast cancer: Insights into the role of vitamin D3

AIMS

Aldehyde dehydrogenase-1 (ALDH-1) is considered a signature of breast cancer stem cells and is linked to poor outcomes in breast cancer patients. This study aimed at investigating the effect of vitamin D3 on enhancing the tumor responsiveness to different conventional chemotherapeutic agents, viz., cisplatin, methotrexate, and doxorubicin.

MAIN METHODS

In vitro and in vivo experiments were performed using combinations of vitamin D3 and chemotherapeutic agents. Cell cycle analysis and apoptosis assays were performed. Moreover, ALDH-1 expression levels were estimated in cancer cell lines and solid tumors. For solid tumors, tumor volume and histopathological necrotic indices were estimated. Leukocyte presence was also evaluated in tumors using leukocyte common antigen (LCA).

KEY FINDINGS

Results showed a synergistic interaction between vitamin D3 and each of the chemotherapeutic agents on breast cancer cell lines as well as cell cycle arrest at G2/M phase. A decrease in ALDH-1 levels was reported in both breast cancer cells and in tumor tissues. Reductions in tumor volume were also observed in the groups which received the combination therapy. An influence on necrosis rather than apoptosis was also reported, as evidenced by necrotic indices and Bcl-2 expression in tumor sections, respectively. Increased local leukocytes in tumors was also evident, as indicated by increased expression of leukocyte common antigen (LCA).

SIGNIFICANCE

Overall, the present study shows that vitamin D3 has an impact on resistance to different chemotherapeutic agents which could be due to the inhibition of ALDH-1, suggesting its use as an adjuvant therapy in cancer patients receiving chemotherapy.

Machilin D, a Lignin Derived from Saururus chinensis, Suppresses Breast Cancer Stem Cells and Inhibits NF-κB Signaling

Cancer stem cells are responsible for breast cancer initiation, metastasis, and relapse. Targeting breast cancer stem cells (BCSCs) using phytochemicals is a good strategy for the treatment of cancer. A silica gel, a reversed-phase C18 column (ODS), a Sephadex LH-20 gel, thin layer chromatography, and high-performance liquid chromatography (HPLC) were used for compound isolation from Saururus chinensis extracts. The isolated compound was identified as machilin D by mass spectrometry and nuclear magnetic resonance (NMR). Machilin D inhibited the growth and mammosphere formation of breast cancer cells and inhibited tumor growth in a xenograft mouse model. Machilin D reduced the proportions of CD44⁺/CD24^- and aldehyde dehydrogenase 1 (ALDH1)-positive cells. Furthermore, this compound reduced the nuclear localization of the NF-κB protein and decreased the IL-6 and IL-8 secretion in mammospheres. These results suggest that machilin D blocks IL-6 and IL-8 signaling and induces CSC death and thus may be a potential agent targeting BCSCs.