Drug-resistant Cancer Stem Cells Research Articles

Stabilization of TGF-β Receptor 1 by a Receptor-Associated Adaptor Dictates Feedback Activation of the TGF-β Signaling Pathway to Maintain Liver Cancer Stemness and Drug Resistance.

Dysregulation of the transforming growth factor-β (TGF-β)signaling pathway regulates cancer stem cells (CSCs) and drug sensitivity, whereas it remains largely unknown how feedback regulatory mechanisms are hijacked to fuel drug-resistant CSCs. Through a genome-wide CRISPR activation screen utilizing stem-like drug-resistant properties as a readout, the TGF-β receptor-associated binding protein 1 (TGFBRAP1) is identified as a TGF-β-inducible positive feedback regulator that governs sensitivity to tyrosine kinase inhibitors (TKIs) and promotes liver cancer stemness. By interacting with and stabilizing the TGF-β receptor type 1 (TGFBR1), TGFBRAP1 plays an important role in potentiating TGF-β signaling. Mechanistically, TGFBRAP1 competes with E3 ubiquitin ligases Smurf1/2 for binding to TGFΒR1, leading to impaired receptor poly-ubiquitination and proteasomal degradation. Moreover, hyperactive TGF-β signaling in turn up-regulates TGFBRAP1 expression in drug-resistant CSC-like cells, thereby constituting a previously uncharacterized feedback mechanism to amplify TGF-β signaling. As such, TGFBRAP1 expression is correlated with TGFΒR1 levels and TGF-β signaling activity in hepatocellular carcinoma (HCC) tissues, as well as overall survival and disease recurrence in multiple HCC cohorts. Therapeutically, blocking TGFBRAP1-mediated stabilization of TGFBR1 by selective inhibitors alleviates Regorafenib resistance via reducing CSCs. Collectively, targeting feedback machinery of TGF-β signaling pathway may be an actionable approach to mitigate drug resistance and liver cancer stemness.

Graphene Quantum Dots Eradicate Resistant and Metastatic Cancer Cells by Enhanced Interfacial Inhibition.

Drug-resistant and metastatic cancer cells such as a small population of cancer stem cells (CSCs) play a crucial role in metastasis and relapse. Conventional small-molecule chemotherapeutics, however, are unable to eradicate drug-resistant CSCs owing to limited interface inhibitory effects. Herein, it is reported that enhanced interfacial inhibition leading to eradication of drug-resistant CSCs can be dramatically induced by self-insertion of bioactive graphene quantum dots (GQDs) into DNA major groove (MAG) sites in cancer cells. Since transcription factors regulate gene expression at the MAG site, MAG-targeted GQDs exert greatly enhanced interfacial inhibition, downregulating the expression of a collection of cancer stem genes such as ALDH1, Notch1, and Bmi1. Moreover, the nanoscale interface inhibition mechanism reverses cancer multidrug resistance (MDR) by inhibiting MDR1 gene expression when GQDs are used at a nontoxic concentration (1/4 × half-maximal inhibitory concentration (IC50)) as the MDR reverser. Given their high efficacy in interfacial inhibition, CSC-mediated migration, invasion, and metastasis of cancer cells can be substantially blocked by MAG-targeted GQDs, which can also be harnessed to sensitize clinical cytotoxic agents for improved efficacy in combination chemotherapy. These findings elucidate the inhibitory effects of the enhanced nano-bio interface at the MAG site on eradicating CSCs, thus preventing cancer metastasis and recurrence.

Modeling 5-FU-Induced Chemotherapy Selection of a Drug-Resistant Cancer Stem Cell Subpopulation.

(1) Background: Cancer stem cells (CSCs) are a subpopulation of cells in a tumor that can self-regenerate and produce different types of cells with the ability to initiate tumor growth and dissemination. Chemotherapy resistance, caused by numerous mechanisms by which tumor tissue manages to overcome the effects of drugs, remains the main problem in cancer treatment. The identification of markers on the cell surface specific to CSCs is important for understanding this phenomenon. (2) Methods: The expression of markers CD24, CD44, ALDH1, and ABCG2 was analyzed on the surface of CSCs in two cancer cell lines, MDA-MB-231 and HCT-116, after treatment with 5-fluorouracil (5-FU) using flow cytometry analysis. A machine learning model (ML)-genetic algorithm (GA) was used for the in silico simulation of drug resistance. (3) Results: As evaluated through the use of flow cytometry, the percentage of CD24-CD44+ MDA-MB-231 and CD44, ALDH1 and ABCG2 HCT-116 in a group treated with 5-FU was significantly increased compared to untreated cells. The CSC population was enriched after treatment with chemotherapy, suggesting that these cells have enhanced drug resistance mechanisms. (4) Conclusions: Each individual GA prediction model achieved high accuracy in estimating the expression rate of CSC markers on cancer cells treated with 5-FU. Artificial intelligence can be used as a powerful tool for predicting drug resistance.

Nanomedicine as a multimodal therapeutic paradigm against cancer: on the way forward in advancing precision therapy.

Recent years have witnessed dramatic improvements in nanotechnology-based cancer therapeutics, and it continues to evolve from the use of conventional therapies (chemotherapy, surgery, and radiotherapy) to increasingly multi-complex approaches incorporating thermal energy-based tumor ablation (e.g. magnetic hyperthermia and photothermal therapy), dynamic therapy (e.g. photodynamic therapy), gene therapy, sonodynamic therapy (e.g. ultrasound), immunotherapy, and more recently real-time treatment efficacy monitoring (e.g. theranostic MRI-sensitive nanoparticles). Unlike monotherapy, these multimodal therapies (bimodal, i.e., a combination of two therapies, and trimodal, i.e., a combination of more than two therapies) incorporating nanoplatforms have tremendous potential to improve the tumor tissue penetration and retention of therapeutic agents through selective active/passive targeting effects. These combinatorial therapies can correspondingly alleviate drug response against hypoxic/acidic and immunosuppressive tumor microenvironments and promote/induce tumor cell death through various multi-mechanisms such as apoptosis, autophagy, and reactive oxygen-based cytotoxicity, e.g., ferroptosis, etc. These multi-faced approaches such as targeting the tumor vasculature, neoangiogenic vessels, drug-resistant cancer stem cells (CSCs), preventing intra/extravasation to reduce metastatic growth, and modulation of antitumor immune responses work complementary to each other, enhancing treatment efficacy. In this review, we discuss recent advances in different nanotechnology-mediated synergistic/additive combination therapies, emphasizing their underlying mechanisms for improving cancer prognosis and survival outcomes. Additionally, significant challenges such as CSCs, hypoxia, immunosuppression, and distant/local metastasis associated with therapy resistance and tumor recurrences are reviewed. Furthermore, to improve the clinical precision of these multimodal nanoplatforms in cancer treatment, their successful bench-to-clinic translation with controlled and localized drug-release kinetics, maximizing the therapeutic window while addressing safety and regulatory concerns are discussed. As we advance further, exploiting these strategies in clinically more relevant models such as patient-derived xenografts and 3D organoids will pave the way for the application of precision therapy.

Hormone Metabolites and Herbal Bioactive Agents: Potential Drug Candidates for the Luminal A Breast Cancer subtype

Background: Hormone receptor positive, human epidermal growth factor receptor negative Luminal A breast cancer subtype responds to targeted endocrine therapy, signal transduction inhibitors and cyclin dependent kinase inhibitors. Estrogen and progesterone receptor mediated signal transduction involves receptor-DNA binding and transcriptional activation of downstream target genes. In addition to hormone receptor signaling, cellular metabolism of estradiol and progesterone exhibit distinct roles in cancer growth modulation. Targeted therapy is associated with systemic toxicity, therapy resistance and emergence of chemo-resistant cancer initiating stem cells. These limitations emphasize identification of testable drug candidates for therapy resistant breast cancer. Cellular metabolism of ovarian steroid hormones generates oxidative metabolites with distinct growth modulating effects. Anti-proliferative metabolites may represent potential drug candidates. Objectives: The objectives of the present review are to provide i) Systematic discussion of published evidence relevant to the role of ovarian steroid hormone metabolism in growth modulatory effects on cancer progression, ii) Evidence for applicability of Luminal A breast cancer and drug-resistant cancer stem cell models to identify mechanistic leads for efficacy of anti-proliferative hormone metabolites, and iii) Future research directions for clinical translatability of patient derived preclinical data. Conclusions: Collectively, present evidence validates experimental approaches to identify hormone metabolites as potential drug candidates for therapy-resistant breast cancer. .

Manuka honey's anti-metastatic impact on colon cancer stem-like cells: unveiling its effects on epithelial-mesenchymal transition, angiogenesis and telomere length.

Colorectal cancer often leads to metastasis, with cancer stem cells (CSCs) playing a pivotal role in this process. Two closely linked mechanisms, epithelial-mesenchymal transition and angiogenesis, contribute to metastasis and recent research has also highlighted the impact of telomere replication on this harmful tumor progression. Standard chemotherapy alone can inadvertently promote drug-resistant CSCs, posing a challenge. Combining chemotherapy with other compounds, including natural ones, shows promise in enhancing effectiveness while minimizing side effects. This study investigated the anti-metastatic potential of Manuka honey, both alone and in combination with 5-fluorouracil, using a 3D model of colonospheres enriched with CSC-like cells. In summary, it was observed that the treatment reduced migration ability by downregulating the transcription factors Slug, Snail, and Twist, which are key players in epithelial-mesenchymal transition. Additionally, Manuka honey downregulated pro-angiogenic factors and shortened CSC telomeres by downregulating c-Myc - demonstrating an effective anti-metastatic potential. This study suggests new research opportunities for studying the impact of natural compounds when combined with pharmaceuticals, with the potential to enhance effectiveness and reduce side effects.

Natural products as drug candidates for breast cancer (Review).

Progression of early-stage breast cancer to advanced-stage metastatic disease represents a major cause of death in women. Long-term conventional and targeted therapy for breast cancer includes multi-drug combinations of cytotoxic chemotherapeutics and pathway-selective small molecule inhibitors. These treatment options are frequently associated with systemic toxicity, intrinsic/acquired therapy resistance and emergence of a drug-resistant cancer stem cell population. This stem cell population has a chemo-resistant, cancer-initiating, premalignant phenotype that is accompanied by cellular plasticity and metastatic potential. These limitations emphasize an unmet need to identify testable alternatives against therapy-resistant metastatic breast cancer. Natural products such as dietary phytochemicals, nutritional herbs and their constitutive bioactive agents have documented human consumption, and lack detectable systemic toxicity and resultant off-target unfavorable side effects. Because of these advantages, natural products may represent testable alternatives for therapy-resistant breast cancer. The present review discusses published evidence for growth inhibitory efficacy of natural products on cellular models for molecular subtypes of clinical breast cancer and development of drug-resistant stem cell models. Collectively, this evidence validates mechanism-based experimental approaches to screen and prioritize efficacious bioactive agents from natural products as novel drug candidates that may function as therapeutic alternatives for breast cancer.

MiR-548 K regulatory effect on the ABCG2 gene expression in MDR breast cancer cells.

multidrug resistance (MDR) is One of the foremost challenges in overcoming breast cancer. Various molecular processes are involved in the development of MDR in breast cancer cells, including over expression of ABC transporters such as ABCG2 (BCRP), increase breast cancer stem cells drug resistance, and epithelial mesenchymal transition. In the present study, we used bioinformatics and experimental analysis to investigate the role of miR-548 K, in the modulating of ABCG2, in MDR breast cancer cells. In silico inspections introduce 14 microRNAs targeting 3'-UTR region of ABCG2 transcripts, which are probably involved in breast cancer drug resistance. An association was highlighted between miR-548 k with ABC transporter family. The expression level of ABCG2 gene in MCF7-MX cell lines was significantly more than MCF7 cell lines. On the other hand, we increased the expression of miR-548 K in MCF7-MX and MCF7 cell lines through its transfection, which dramatically coincided with decreasion in the ABCG2 transcripts level. Additional studies on patient samples revealed that the expression of ABCG2 showed an increase in ABCG2 level in neoadjuvant chemotherapy drugs resistance (NCDR) patients compared to primary pre-operative chemotherapy drugs response (PCDR) patients. Also, a reduction in the expression of miR-548 K in NCDR patients was revealed. The results of our study suggest that miR-548 K may be involved in modulating the expression of ABCG2 in MDR breast cancer cells.

First-Line Combination Treatment with Low-Dose Bipolar Drugs for ABCB1-Overexpressing Drug-Resistant Cancer Populations.

Tumors include a heterogeneous population, of which a small proportion includes drug-resistant cancer (stem) cells. In drug-sensitive cancer populations, first-line chemotherapy reduces tumor volume via apoptosis. However, it stimulates drug-resistant cancer populations and finally results in tumor recurrence. Recurrent tumors are unresponsive to chemotherapeutic drugs and are primarily drug-resistant cancers. Therefore, increased apoptosis in drug-resistant cancer cells in heterogeneous populations is important in first-line chemotherapeutic treatments. The overexpression of ABCB1 (or P-gp) on cell membranes is an important characteristic of drug-resistant cancer cells; therefore, first-line combination treatments with P-gp inhibitors could delay tumor recurrence. Low doses of bipolar drugs showed P-gp inhibitory activity, and their use as a combined therapy sensitized drug-resistant cancer cells. FDA-approved bipolar drugs have been used in clinics for a long period of time, and their toxicities are well reported. They can be easily applied as first-line combination treatments for targeting resistant cancer populations. To apply bipolar drugs faster in first-line combination treatments, knowledge of their complete information is crucial. This review discusses the use of low-dose bipolar drugs in sensitizing ABCB1-overexpressing, drug-resistant cancers. We believe that this review will contribute to facilitating first-line combination treatments with low-dose bipolar drugs for targeting drug-resistant cancer populations. In addition, our findings may aid further investigations into targeting drug-resistant cancer populations with low-dose bipolar drugs.

Phytochemicals Treatment Decreases Drug-Resistant Breast Cancer Stem Cell Viability and Invasiveness by Blocking the HPI/AMF Surviving Pathway

The advent of natural phytochemicals for interfering with the HPI/AMF (erythrose, Ery) and TGF-ß (sulforaphane, SP) signaling pathways appears as a promising therapeutic strategy against Breast Cancer Stem Cells (BCSC). The BCSC viability, drug resistance, apoptosis evasion, invasiveness and HPI/AMF signaling axe were analyzed with Ery or SP. HPI/AMF, its downstream targets (H-Ras, p-Akt, p-Erk, NF-kB, p-NF-kB, Wnt/ß-catenin), XIAP, cytokines secretion and the glycoprotein- P increased their contents (2-83 times) in BCSC vs. parental MCF-7 cells. The incubation of BCSC with Ery (80nM/24h) significantly decreased (>85%) the HPI/AMF level, glycoprotein-P, XIAP and the secretion of HPI-AMF/TGF-ß vs. non treated-BCSC, which in turn affected cellular invasiveness. SP (150μM/24h) was unable to affect HPI/AMF axe, although invasiveness was affected (>80%). Ery in combination with SP decreased BCSC viability after 3 days of treatment. These results showed that these phytochemicals are a promising nutrition strategy prompting the design of treatments to blocking cancer relapse induced by CSC.

Polyherbal formulation conjugated to gold nanoparticles induced ferroptosis in drug-resistant breast cancer stem cells through ferritin degradation.

Aim: Due to their minimal side effects, the anti-cancer properties of the polyherbal formulation are being investigated. However, due to their low absorption potential, the administration of polyherbal formulations is restricted. Loading the polyherbal formulation into gold nanoparticles enhances the bioavailability of the polyherbal formulation (PHF) accompanied by reducing the concentration of doxorubicin (dox). Ferroptosis is one of the novel pathways that specifically target cancer stem cells due to high ferritin levels. Hence, in the present study, we conjugated polyherbal formulation with gold nanoparticles and studied its effect on inducing ferroptosis in drug-resistant breast cancer cell lines. Materials and methods: PHF and dox conjugated to gold nanoparticles were characterized using FTIR, UV-Vis spectrophotometer, DLS, particle size analyzer, and XRD. The drug entrapment and efficiency studies were performed to assess the biodegradable potential of the synthesized gold nanoparticles. Paclitaxel-resistant breast cancer stem cells were generated, and an MTT assay was performed to evaluate the cytotoxicity potential of AuNP-PHF and AuNP-dox. Scratch assay and clonogenic assay were performed to assess the migration and proliferation of the cells after treatment with chosen drug combinations. The ability of PHF and dox conjugated to gold nanoparticles to induce ferritinophagy was evaluated by RT-PCR. Finally, image analysis was performed to check apoptosis and cellular ROS using inverted fluorescent microscope. The ability to induce cell cycle arrest was assessed by cell cycle analysis using flow cytometer. Results and conclusion: PHF and dox conjugated to gold nanoparticles showed high stability and showed to induce ferritin degradation in drug resistant breast cancer stem cells through ferritin degradation. AuNP-PHF in combination with low dose of AuNP-Dox nanoconjugate could be used as an effective cancer therapeutic agent, by targeting the autophagy necroptosis axis.

Cold plasma and inhibition of STAT3 selectively target tumorigenicity in osteosarcoma

Osteosarcoma (OS) is a malignant type of bone cancer that arises in periods of increased bone formation. Curative strategies for these types of tumors have remained essentially unchanged for decades and the overall survival for most advanced cases is still dismally low. This is in part due to the existence of drug resistant Cancer Stem Cells (CSC) with progenitor properties that are responsible for tumor relapse and metastasis. In the quest for therapeutic alternatives for OS, Cold Atmospheric Plasmas and Plasma-Treated Liquids (PTL) have come to the limelight as a source of Reactive Oxygen and Nitrogen Species displaying selectivity towards a variety of cancer cell lines. However, their effects on CSC subpopulations and in vivo tumor growth have been barely studied to date. By employing bioengineered 3D tumor models and in vivo assays, here we show that low doses of PTL increase the levels of pro-stemness factors and the self-renewal ability of OS cells, coupled to an enhanced in vivo tumor growth potential. This could have critical implications to the field. By proposing a combined treatment, our results demonstrate that the deleterious pro-stemness signals mediated by PTL can be abrogated when this is combined with the STAT3 inhibitor S3I-201, resulting in a strong suppression of in vivo tumor growth. Overall, our study unveils an undesirable stem cell-promoting function of PTL in cancer and supports the use of combinatorial strategies with STAT3 inhibitors as an efficient treatment for OS avoiding critical side effects. We anticipate our work to be a starting point for wider studies using relevant 3D tumor models to evaluate the effects of plasma-based therapies on tumor subpopulations of different cancer types. Furthermore, combination with STAT3 inhibition or other suitable cancer type-specific targets can be relevant to consolidate the development of the field.

Gain-of-glycosylation in breast multi-drug-resistant MCF-7 adenocarcinoma cells and cancer stem cells characterized by site- and structure-specific N-glycoproteomics

N-linked glycosylation (N-glycosylation) is a common protein post-translational modification, occurring on more than half of mammalian proteins; in striking contract with small molecule modifications (such as methylation, phosphorylation) with only single structures, N-glycosylation has multiple dimensional structural features (monosaccharide composition, sequence, linkage, anomer), which generates enormous N-glycan structures; and these structures widely regulate protein structure and functions. For the modification site, N-glycosylation occurs on the Asn residue among the consensus N-X-S/T/C (X≠P) motif; mutation-originated amino acid change may lead to loss of such an original motif and thus loss-of-glycosylation (LoG) or gain of such a new motif and thus gain-of-glycosylation (GoG). Both LoG and GoG generates new structures and functions of glycoproteins, which has been observed in the S protein of SARS-Cov-2 as well as malignant diseases. Here we report our glycoproteome-wide qualitative N-glycoproteomics characterization of GoGs in breast cancer Adriamycin drug resistance (ADR) cells (MCF-7/ADR) and cancer stem cells (MCF-7/ADR CSCs); comprehensive N-glycosite and N-glycan structure information at the intact N-glycopeptide level were reported.

When cancer drug resistance meets metabolomics (bulk, single-cell and/or spatial): Progress, potential, and perspective.

Resistance to drug treatment is a critical barrier in cancer therapy. There is an unmet need to explore cancer hallmarks that can be targeted to overcome this resistance for therapeutic gain. Over time, metabolic reprogramming has been recognised as one hallmark that can be used to prevent therapeutic resistance. With the advent of metabolomics, targeting metabolic alterations in cancer cells and host patients represents an emerging therapeutic strategy for overcoming cancer drug resistance. Driven by technological and methodological advances in mass spectrometry imaging, spatial metabolomics involves the profiling of all the metabolites (metabolomics) so that the spatial information is captured bona fide within the sample. Spatial metabolomics offers an opportunity to demonstrate the drug-resistant tumor profile with metabolic heterogeneity, and also poses a data-mining challenge to reveal meaningful insights from high-dimensional spatial information. In this review, we discuss the latest progress, with the focus on currently available bulk, single-cell and spatial metabolomics technologies and their successful applications in pre-clinical and translational studies on cancer drug resistance. We provide a summary of metabolic mechanisms underlying cancer drug resistance from different aspects; these include the Warburg effect, altered amino acid/lipid/drug metabolism, generation of drug-resistant cancer stem cells, and immunosuppressive metabolism. Furthermore, we propose solutions describing how to overcome cancer drug resistance; these include early detection during cancer initiation, monitoring of clinical drug response, novel anticancer drug and target metabolism, immunotherapy, and the emergence of spatial metabolomics. We conclude by describing the perspectives on how spatial omics approaches (integrating spatial metabolomics) could be further developed to improve the management of drug resistance in cancer patients.

Childhood Obesity: A Potential Key Factor in the Development of Glioblastoma Multiforme.

Glioblastoma multiforme (GBM) is a malignant primary tumor type of the central nervous system (CNS). This type of brain tumor is rare and is responsible for 12–15% of all brain tumors. The typical survival rate of GBM is only 12 to 14 months. GBM has a poor and unsatisfactory prognosis despite advances in research and therapeutic interventions via neurosurgery, radiation, and chemotherapy. The molecular heterogeneity, aggressive nature, and occurrence of drug-resistant cancer stem cells in GB restricts the therapeutic efficacy. Interestingly, the CNS tumors in children are the second most usual and persistent type of solid tumor. Since numerous research studies has shown the association between obesity and cancer, childhood obesity is one of the potential reasons behind the development of CNS tumors, including GBM. Obesity in children has almost reached epidemic rates in both developed and developing countries, harming children’s physical and mental health. Obese children are more likely to face obesity as adults and develop non-communicable diseases such as diabetes and cardiovascular disease as compared to adults with normal weight. However, the actual origin and cause of obesity are difficult to be pointed out, as it is assumed to be a disorder with numerous causes such as environmental factors, lifestyle, and cultural background. In this narrative review article, we discuss the various molecular and genetic drivers of obesity that can be targeted as potential contributing factors to fight the development of GBM in children.

A Gold Nanoparticle Bioconjugate Delivery System for Active Targeted Photodynamic Therapy of Cancer and Cancer Stem Cells.

Simple SummaryCancer stem cells (CSCs) play a crucial role in tumor development, metastasis, therapy resistance, and relapse due to their self-renewal and proliferative potential. In this review, we summarized the application of gold nanoparticle (AuNPs) bioconjugates in enhancing the efficiency of photodynamic therapy (PDT) in cancer and CSCs. We also highlighted the challenges facing the translation of AuNPs application in clinical settings.Cancer stem cells (CSCs), also called tumor-initiating cells, are a subpopulation of cancer cells believed to be the leading cause of cancer initiation, growth, metastasis, and recurrence. Presently there are no effective treatments targeted at eliminating CSCs. Hence, an urgent need to develop measures to target CSCs to eliminate potential recurrence and metastasis associated with CSCs. Cancer stem cells have inherent and unique features that differ from other cancer cells, which they leverage to resist conventional therapies. Targeting such features with photodynamic therapy (PDT) could be a promising treatment for drug-resistant cancer stem cells. Photodynamic therapy is a light-mediated non-invasive treatment modality. However, PDT alone is unable to eliminate cancer stem cells effectively, hence the need for a targeted approach. Gold nanoparticle bioconjugates with PDT could be a potential approach for targeted photodynamic therapy of cancer and CSCs. This approach has the potential for enhanced drug delivery, selective and specific attachment to target tumor cells/CSCs, as well as the ability to efficiently generate ROS. This review examines the impact of a smart gold nanoparticle bioconjugate coupled with a photosensitizer (PS) in promoting targeted PDT of cancer and CSC.

The TH1902 Docetaxel Peptide-Drug Conjugate Inhibits Xenografts Growth of Human SORT1-Positive Ovarian and Triple-Negative Breast Cancer Stem-like Cells

Background: Breast and ovarian cancer stem cells (CSC) can contribute to the invasive and chemoresistance phenotype of tumors. TH1902, a newly developed sortilin (SORT1)-targeted peptide-docetaxel conjugate is currently in phase-1 clinical trial. Whether TH1902 impacts the chemoresistance phenotype of human triple-negative breast CSC (hTNBCSC) and ovarian CSC (hOvCSC) is unknown. Methods and Results: Immunophenotyping of hTNBCSC and hOvCSC was performed by flow cytometry and confirmed the expression of SORT1, and of CSC markers CD133, NANOG, and SOX2. Western blotting demonstrated the expression of the drug efflux pumps from the P-gp family members, ABCB1 and ABCB5. The cellular uptake of the fluorescent Alexa488-peptide from TH1902 was inhibited upon siRNA-mediated repression of SORT1 or upon competition with SORT1 ligands. In contrast to docetaxel, TH1902 inhibited in vitro migration, induced cell apoptosis and lead to G2/M cell cycle arrest of the hTNBCSC. These events were unaffected by the presence of the P-gp inhibitors cyclosporine A or PSC-833. In vivo, using immunosuppressed nude mice xenografts, TH1902 significantly inhibited the growth of hTNBCSC and hOvCSC xenografts (~80% vs. ~35% for docetaxel) when administered weekly as intravenous bolus for three cycles at 15 mg/kg, a dose equivalent to the maximal tolerated dose of docetaxel. Therapeutic efficacy was further observed when carboplatin was combined to TH1902. Conclusions: Overall, TH1902 exerts a superior anticancer activity than the unconjugated docetaxel, in part, by circumventing the CSC drug resistance phenotype that could potentially reduce cancer recurrence attributable to CSC.

Synthetic Retinoid Kills Drug-Resistant Cancer Stem Cells via Inducing RARγ-Translocation-Mediated Tension Reduction and Chromatin Decondensation.

A recently developed synthetic retinoid abrogates proliferation and induces apoptosis of drug-resistant malignant-cancer-stem-cell-like cells. However, the underlying mechanisms of how the synthetic retinoid induces cancer-stem-cell-like cell tumor-repopulating cell (TRC) apoptosis are elusive. Here, it is shown that although the retinoid and conventional anticancer drugs cisplatin, all-trans retinoic acid, and tazarotene all inhibit cytoskeletal tension and decondense chromatin prior to inducing TRC apoptosis, half-maximal inhibitory concentration of the retinoid is 20-fold lower than those anticancer drugs. The synthetic retinoid induces retinoic acid receptor gamma (RARγ) translocation from the nucleus to the cytoplasm, leading to reduced RARγ binding to Cdc42 promoter and Cdc42 downregulation, which decreases filamentous-actin (F-actin) and inhibits cytoskeletal tension. Elevating F-actin or upregulating histone 3 lysine 9 trimethylation decreases retinoid-induced DNA damage and apoptosis of TRCs. The combinatorial treatment with a chromatin decondensation molecule and the retinoid inhibits tumor metastasis in mice more effectively than the synthetic retinoid alone. These findings suggest a strategy of lowering cell tension and decondensing chromatin to enhance DNA damage to abrogate metastasis of cancer-stem-cell-like cells with high efficacy.

Reversal of epithelial-mesenchymal transition and inhibition of tumor stemness of breast cancer cells through advanced combined chemotherapy

The abnormal activation of the Wnt/β-catenin signaling pathway and epithelial-mesenchymal transition (EMT) in drug-resistant tumor cells and cancer stem cells (CSCs) stimulate tumor metastasis and recurrence. Here, a promising combined chemotherapeutic strategy of salinomycin (SL) and doxorubicin (DOX) with specific inhibition of tumor stemness by a targeted co-delivery nanosystem was developed to overcome this abnormal progression. This strategy could be benefit drugs to effectively penetrate and infiltrate into spheres of 3D-cultured breast cancer stem cells (BCSCs). The expression of the Wnt/β-catenin signaling pathway-related genes (β-catenin, LRP6, LEF1, and TCF12) and target genes (Cyclin D1, Cmyc, and Fibronectin) as well as CSC stemness-related genes (Oct4, Nanog, and Hes1) was downregulated by redox-sensitive co-delivery micelles decorated with oligohyaluronic acid as the active targeting moiety. The changes in EMT-associated gene expression (E-cadherin and Vimentin) in vitro showed that the EMT process was also effectively inverted. This strategy achieved a strong inhibitory effect on solid tumor growth and an effective reduction in the risk of tumor metastasis in 4T1 tumor-bearing mice in vivo and effectively alleviated splenomegaly caused by the malignant tumor. Immunohistochemical staining analysis of E-cadherin, Vimentin, and β-catenin confirmed that the inversion of the EMT was also achieved in solid tumors. These results highlight the potential of SL and DOX combined chemotherapeutic strategy for eliminating breast carcinoma. Statement of significanceCancer stem cells (CSCs), as an important part of tumor heterogeneity, can survive against conventional chemotherapy and initiate tumorigenesis, recurrence, and metastasis. Moreover, non-CSCs can convert into the CSC state through the abnormal Wnt/β-catenin pathway, which is closely related to the epithelial-mesenchymal transition (EMT) process. Here, redox-degradable binary drug-loaded micelles (PPH/DOX+SL) were designed to target CSCs and overcome drug resistance of breast cancer cells. The combined chemotherapy of salinomycin (SL) and doxorubicin (DOX) reversed drug resistance, while the PPH/DOX+SL micelles enhanced the intracellular accumulation and drug penetration of BCSC spheres. The introduction of SL downregulated the expression of tumor stemness genes and the Wnt/β-catenin pathway-related genes and inverted the EMT process. PPH/DOX+SL continuously inhibited tumor growth and invasion in vivo.

Stem Cell Models for Breast and Colon Cancer: Experimental Approach for Drug Discovery.

The progression of the early stages of female breast and colon cancer to metastatic disease represents a major cause of mortality in women. Multi-drug chemotherapy and/or pathway selective targeted therapy are notable for their off-target effects and are associated with spontaneous and/or acquired chemotherapy resistance and the emergence of premalignant chemo-resistant cancer-initiating stem cells. The stem cell populations are responsible for the evolution of therapy-resistant metastatic disease. These limitations emphasize an unmet need to develop reliable drug-resistant cancer stem cell models as novel experimental approaches for therapeutic alternatives in drug discovery platforms. Drug-resistant stem cell models for breast and colon cancer subtypes exhibit progressive growth in the presence of cytotoxic chemo-endocrine therapeutics. The resistant cells exhibit upregulated expressions of stem cell-selective cellular and molecular markers. Dietary phytochemicals, nutritional herbs and their constituent bioactive compounds have documented growth inhibitory efficacy for cancer stem cells. The mechanistic leads for the stem cell-targeted efficacy of naturally occurring agents validates the present experimental approaches for new drug discovery as therapeutic alternatives for therapy-resistant breast and colon cancer. The present review provides a systematic discussion of published evidence on (i) conventional/targeted therapy for breast and colon cancer, (ii) cellular and molecular characterization of stem cell models and (iii) validation of the stem cell models as an experimental approach for novel drug discovery of therapeutic alternatives for therapy-resistant cancers.