Role of ABCB1 in mediating chemoresistance of triple-negative breast cancers

Nanodiamond-Protein hybrid Nanoparticles: LHRH receptor targeted and co-delivery of doxorubicin and dasatinib for triple negative breast cancer therapy

Triple Negative Breast Cancer (TNBC) is an aggressive type of breast cancer that is difficult to treat with conventional therapies. This study aimed to develop a novel therapeutic approach using a multifunctional protein-nanodiamond nanocomposite to co-deliver doxorubicin (DOX) and dasatinib (DAS) to cancer cells via luteinising hormone-releasing hormone receptors. Nanodiamonds help retain DOX in targeted cells, while α-lactalbumin efficiently encapsulates DAS, reducing side effects. We successfully formulated the nanocomposite with over 80 % drug loading efficiency for both drugs. The imine Schiff-base bond in the nanocomposite hydrolyzes in the acidic pH tumor environment, triggering approximately 65 % drug release after 72 h, compared to less than 20 % in neutral pH. In vitro studies showed enhanced uptake of DOX and DAS in TNBC cell lines, potentially overcoming drug resistance. The combined delivery showed enhanced synergistic cytotoxic effects in drug-resistant TNBC cell models. For example, in the MDA-MB-231 cell line, the IC50 of DOX dropped to 45.63 ng/ml, while in MDA-MB-468, DAS decreased to 35.85 ng/ml with nanoparticle therapy. In vivo experiments utilizing a TNBC mouse model demonstrated the therapeutic effectiveness of the nanocomposite, leading to a 55 % reduction in tumor growth and enhanced survival rates. All mice given the nanocomposite survived after 44 days, but most treated with the DOX/DAS mixture died by day 28. This research showcases multifunctional nanocomposites as targeted drug delivery systems for TNBC, improving drug uptake and cytotoxicity. This strategy presents a promising method for treating drug-resistant breast cancer, with potential clinical applications and synergy with other therapies.

The role of the mTOR pathway in breast cancer stem cells (BCSCs): mechanisms and therapeutic potentials

Breast cancer remains the most frequently diagnosed cancer globally, exerting a profound impact on women's health and healthcare systems. Central to its pathogenesis and therapeutic resistance are breast cancer stem cells (BCSCs), which possess unique properties such as self-renewal, differentiation, and resistance to conventional therapies, contributing to tumor initiation, metastasis, and recurrence. This comprehensive review elucidates the pivotal role of the mechanistic target of rapamycin (mTOR) pathway in regulating BCSCs and its implications for breast cancer progression and treatment resistance. We explore the cellular mechanisms by which mTOR influences metastasis, metabolism, autophagy, and ferroptosis in BCSCs, highlighting its contribution to epithelial-to-mesenchymal transition (EMT), metabolic reprogramming, and survival under therapeutic stress. On a molecular level, mTOR interacts with key signaling pathways including PI3K/Akt, Notch, IGF-1R, AMPK, and TGF-β, as well as regulatory proteins and non-coding RNAs, orchestrating a complex network that sustains BCSC properties and mediates chemoresistance and radioresistance. The review further examines various therapeutic strategies targeting the mTOR pathway in BCSCs, encompassing selective PI3K/Akt/mTOR inhibitors, monoclonal antibodies, natural products, and innovative approaches such as nanoparticle-mediated drug delivery. Clinical trials investigating mTOR inhibitors like sirolimus and combination therapies with agents such as everolimus and trastuzumab are discussed, underscoring their potential in eradicating BCSCs and improving patient outcomes. Additionally, natural compounds and repurposed drugs offer promising adjunctive therapies by modulating mTOR activity and targeting BCSC-specific vulnerabilities. In conclusion, targeting the mTOR pathway presents a viable and promising avenue for enhancing breast cancer treatment efficacy by effectively eliminating BCSCs, reducing tumor recurrence, and improving overall patient survival. Continued research and clinical validation of mTOR-targeted therapies are essential to translate these insights into effective clinical interventions, ultimately advancing personalized cancer management and therapeutic outcomes for breast cancer patients.

Application of drug-induced growth rate inhibition and intracellular drug exposures for comprehensive evaluation of cellular drug sensitivity

In vitro cellular assays are indispensable tools for preclinical understanding of therapeutic candidates. Herein, we have outlined methods for robust determination of cellular sensitivities by adapting drug-induced growth-rate inhibition analysis combined with intracellular drug exposure measurements. Using two auristatins as tool molecules, we demonstrate wide variety of cellular response in sensitive versus resistant cancer cells, as well as in a toxicity-relevant cell type. Cellular response analysis generates metrics describing efficacious extracellular concentrations of drug, as well as the phenotype of response-cytotoxic versus cytostatic. Cell associated drug measurements bridge the gap between extracellular drug concentrations and exposure at intracellular sites required for a desired pharmacodynamic response. Such methods can complement rational drug design by providing thorough understanding of the drug mechanism of action, guide mechanistic selection of target indication and inform exposure-response analysis at various stages of drug discovery.

DNA methylation and immune evasion in triple-negative breast cancer: challenges and therapeutic opportunities

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer characterized by the lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Chemotherapy remains the primary treatment option, yet TNBC frequently develops resistance, leading to relapse and metastasis. Emerging evidence highlights the potential of combining DNA methylation inhibitors with immune checkpoint inhibitors (ICIs). DNA methylation contributes to immune escape by silencing immune-regulatory genes, thereby reducing the tumor's visibility to immune cells. Reversing this epigenetic modification can reinvigorate immune surveillance and enhance the efficacy of immunotherapies. This review discusses the role of DNA methylation in TNBC progression and immune evasion, focusing on recent advances in combination therapies involving DNA methylation inhibitors and ICIs. We discuss the underlying mechanisms that enable these therapeutic synergies, preclinical and clinical evidence supporting the approach, and the challenges posed by tumor heterogeneity, drug resistance, and toxicity. Finally, we explore the potential for personalized treatment strategies incorporating multi-omics data to optimize therapeutic outcomes. The integration of epigenetic therapies and immunotherapy offers a promising avenue for improving survival in TNBC patients.

Network pharmacology and in silico approach to study the mechanism of quercetin against breast cancer

Breast cancer is a significant health concern among females with an estimated 2.3 million cases reported worldwide in 2022. Traditional treatment methods have now developed resistance and various adverse effects, highlighting an urgent need for attention. Therefore, it is advisable to substitute these conventional therapies with innovative medications. Quercetin is a flavonoid, commonly found in various vegetables and fruits and have been shown to possess anti-cancer properties. Network pharmacology is a comprehensive approach that has significantly assisted in investigating the potential of quercetin as a therapeutic option for breast cancer. The first step includes target fishing for quercetin-targeted genes in breast cancer through various online available databases. All intersecting genes were analysed for the phenotypic- genotypic correlation via online VarElect analysis tool. Using the result from the result the GO enrichment and pathway enrichment analysis was done on 52 common genes; followed by PPI network construction and based on topological parameters top 8 genes were filtered. Based on theVenny2.1 and then GEPIA and HPA analysis the key target were identifies as ABCC1, ABCC4, AKT1, ABCB1, CYP1B1, CYP19A1, ABCB4 and ABCG2. Further, Molecular docking was done to investigate the possible interaction of the identified gene with quercetin. Our finding shows quercetin is the potential natural drug that can treat breast cancer effectively. Quercetin interacts with ABCC1, ABCC4, AKT1, ABCB1, CYP1B1, CYP19A1, ABCB4, and ABCG2 at cellular as well as molecular level. The ADMET analysis suggests the bioavaibility of quercetin is around 0.55. Suggesting that quercetin satisfies drug-likeness rules but may face challenges like low bioavailability, which can be enhanced through structural modifications or formulations (e.g., nanoparticles). The molecular docking result assures the interaction of quercetin with the ABCC1, ABCC4, AKT1, ABCB1, CYP1B1, CYP19A1, ABCB4, and ABCG2 with the binding affinity of - 7.2, - 10.1, - 10.4, - 8.0, - 8.2, - 8.2, - 9.0 and - 8.9 respectively. These results suggest quercetin has a stable interaction with the ABCC4 gene. Considering this interaction the quercetin molecules can rescue the cellular condition by inducing apoptosis, inhibiting proliferation, and suppressing metastasis. Quercetin, a natural compound found in fruits and vegetables, has been found to have significant therapeutic roles in treating breast cancer. It inhibits cell cycle arrest, promotes apoptosis, and reduces blood vessel formation. It also reverses drug resistance and has antioxidant and anti-inflammatory properties. This study concludes that the therapeutic influence of quercetin plays a significant role in treating breast cancer and aids in the advancement of the clinical application of quercetin in future studies.

Graphical Abstract

Triple-Negative Breast Cancer Progression and Drug Resistance in the Context of Epithelial-Mesenchymal Transition

Triple-negative breast cancer (TNBC) is one of the most difficult subtypes of breast cancer to treat due to its distinct clinical and molecular characteristics. Patients with TNBC face a high recurrence rate, an increased risk of metastasis, and lower overall survival compared to other breast cancer subtypes. Despite advancements in targeted therapies, traditional chemotherapy (primarily using platinum compounds and taxanes) continues to be the standard treatment for TNBC, often with limited long-term efficacy. TNBC tumors are heterogeneous, displaying a diverse mutation profile and considerable chromosomal instability, which complicates therapeutic interventions. The development of chemoresistance in TNBC is frequently associated with the process of epithelial-mesenchymal transition (EMT), during which epithelial tumor cells acquire a mesenchymal-like phenotype. This shift enhances metastatic potential, while simultaneously reducing the effectiveness of standard chemotherapeutics. It has also been suggested that EMT plays a central role in the development of cancer stem cells. Hence, there is growing interest in exploring small-molecule inhibitors that target the EMT process as a future strategy for overcoming resistance and improving outcomes for patients with TNBC. This review focuses on the progression and drug resistance of TNBC with an emphasis on the role of EMT in these processes. We present TNBC-specific and EMT-related molecular features, key EMT protein markers, and various signaling pathways involved. We also discuss other important mechanisms and factors related to chemoresistance in TNBC within the context of EMT, highlighting treatment advancements to improve patients' outcomes.

Identifying ADME-related gene signature for immune landscape and prognosis in KIRC by single-cell and spatial transcriptome analysis

Kidney renal clear cell carcinoma (KIRC) is the most prevalent subtype of kidney cancer. Although multiple therapeutic agents have been proven effective in KIRC, their clinical application has been hindered by a lack of reliable biomarkers. This study focused on the prognostic value and function of drug absorption, distribution, metabolism, and excretion- (ADME-) related genes (ARGs) in KIRC to enhance personalized therapy. The critical role of ARGs in KIRC microenvironment was confirmed by single cell RNA-seq analysis and spatial transcriptome sequencing analysis for the first time. Then, an ADME-related prognostic signature (ARPS) was developed by the bulk RNA-seq analysis. The ARPS, created through Cox regression, LASSO, and stepAIC analyses, identified eight ARGs that stratified patients into high-risk and low-risk groups. High-risk patients had significantly poorer overall survival. Multivariate analysis confirmed the independent predictive ability of ARPS, and an ARPS-based nomogram was constructed for clinical application. Gene ontology and KEGG pathway analyses revealed immune-related functions and pathways enriched in these groups, with low-risk patients showing better responses to immunotherapy. Finally, the expression of ARGs was validated by qRT-PCR and Western blotting experiments. These findings underscore the prognostic significance of ARPS in KIRC and its potential application in guiding personalized treatment strategies.

Enhancement of Doxorubicin Efficacy by Bacopaside II in Triple-Negative Breast Cancer Cells

BACKGROUND

Triple-negative breast cancer (TNBC) is an aggressive subtype with limited treatment options and high resistance to chemotherapy. Doxorubicin is commonly used, but its efficacy is limited by variable sensitivity and resistance. Bacopaside II, a saponin compound, has shown anti-cancer potential. This study evaluates the effects of doxorubicin and bacopaside II, both individually and in combination, across TNBC subtypes to explore mechanisms of resistance and enhanced drug efficacy.

METHODS

The growth-inhibitory effects of doxorubicin and bacopaside II were assessed in four TNBC cell lines. IC50 values were determined using dose-response assays, and doxorubicin accumulation was measured via spectral flow cytometry. ATP-binding cassette (ABC) transporter expression (ABCB1, ABCC1, ABCC3, and ABCG2) was analyzed for correlations with drug sensitivity. In silico docking assessed the binding affinity of bacopaside II to ABC transporters. A 3D culture model simulated drug-resistant TNBC, and combination effects were evaluated with live-cell imaging.

RESULTS

Doxorubicin sensitivity varied across TNBC molecular subtypes, correlating to intracellular accumulation. Bacopaside II inhibited growth across subtypes, inducing apoptosis in sensitive cells and necrosis in resistant cells. Bacopaside II increased doxorubicin accumulation, independent of P-glycoprotein (ABCB1), possibly through interactions with other ABC transporters. In drug-resistant 3D cultures, bacopaside II maintained efficacy and enhanced doxorubicin accumulation, counteracting ABC transporter-mediated resistance. The doxorubicin and bacopaside II combination showed synergistic growth inhibition.

CONCLUSIONS

Bacopaside II enhances doxorubicin efficacy in TNBC by increasing drug accumulation and overcoming ABC transporter-mediated resistance, suggesting its potential as an adjuvant in TNBC treatment. These findings support further investigation of bacopaside II, particularly for resistant TNBC subtypes.

Diagnostic and Therapeutic Advances of RNAs in Precision Medicine of Gastrointestinal Tumors

Gastrointestinal tumors present a significant challenge for precision medicine due to their complexity, necessitating the development of more specific diagnostic tools and therapeutic agents. Recent advances have positioned coding and non-coding RNAs as emerging biomarkers for these malignancies, detectable by liquid biopsies, and as innovative therapeutic agents. Many RNA-based therapeutics, such as small interfering RNA (siRNA) and antisense oligonucleotides (ASO), have entered clinical trials or are available on the market. This review provides a narrative examination of the diagnostic and therapeutic potential of RNA in gastrointestinal cancers, with an emphasis on its application in precision medicine. This review discusses the current challenges, such as drug resistance and tumor metastasis, and highlights how RNA molecules can be leveraged for targeted detection and treatment. Additionally, this review categorizes specific diagnostic biomarkers and RNA therapeutic targets based on tissue type, offering a comprehensive analysis of their role in advancing precision medicine for gastrointestinal tumors.

A BPTF Inhibitor That Interferes with the Multidrug Resistance Pump to Sensitize Murine Triple-Negative Breast Cancer Cells to Chemotherapy

Triple-negative breast cancer (TNBC) is associated with a generally poor prognosis due to its highly aggressive and metastatic nature, lack of targetable receptors, as well as the frequent development of resistance to chemotherapy. We previously reported that AU1, a small molecule developed as an inhibitor of BPTF (bromodomain PHD finger-containing transcription factor), was capable of sensitizing preclinical models of TNBC to chemotherapy in part via the promotion of autophagy. In studies reported here, we identify an additional property of this compound, specifically that sensitization is associated with the inhibition of the P-glycoprotein (P-gp) efflux pump. In silico molecular docking studies indicate that AU1 binds to active regions of the efflux pump in a manner consistent with the inhibition of the pump function. This work identifies a novel chemical structure that can influence multidrug efflux, an established mechanism of drug resistance in TNBC, that has not yet been successfully addressed by clinical efforts.

Solid Lipid Nanoparticles, an Alternative for the Treatment of Triple-Negative Breast Cancer

Within the field of nanomedicine, which is revolutionizing cancer treatment, solid lipid nanoparticles (SLNs) have shown advantages over conventional chemotherapy when tested on cancer cells in preclinical studies. SLNs have proven to be an innovative strategy for the treatment of triple-negative breast cancer cells, providing greater efficiency than existing treatments in various studies. The encapsulation of antineoplastic drugs in SLNs has facilitated a sustained, controlled, and targeted release, which enhances therapeutic efficiency and reduces adverse effects. Moreover, the surface of SLNs can be modified to increase efficiency. For instance, the coating of these particles with polyethylene glycol (PEG) decreases their opsonization, resulting in a longer life in the circulatory system. The creation of positively charged cationic SLNs (cSLNs), achieved by the utilization of surfactants or ionic lipids with positively charged structural groups, increases their affinity for cell membranes and plasma proteins. Hyaluronic acid has been added to SLNs so that the distinct pH of tumor cells would stimulate the release of the drug and/or genetic material. The current review summarizes the recent research on SLNs, focusing on the encapsulation and transport of therapeutic agents with a cytotoxic effect on triple-negative breast cancer.

Overcoming Cancer Drug Resistance with Nanoparticle Strategies for Key Protein Inhibition

Drug resistance remains a critical barrier in cancer therapy, diminishing the effectiveness of chemotherapeutic, targeted, and immunotherapeutic agents. Overexpression of proteins such as B-cell lymphoma 2 (Bcl-2), inhibitor of apoptosis proteins (IAPs), protein kinase B (Akt), and P-glycoprotein (P-gp) in various cancers leads to resistance by inhibiting apoptosis, enhancing cell survival, and expelling drugs. Although several inhibitors targeting these proteins have been developed, their clinical use is often hampered by systemic toxicity, poor bioavailability, and resistance development. Nanoparticle-based drug delivery systems present a promising solution by improving drug solubility, stability, and targeted delivery. These systems leverage the Enhanced Permeation and Retention (EPR) effect to accumulate in tumor tissues, reducing off-target toxicity and increasing therapeutic efficacy. Co-encapsulation strategies involving anticancer drugs and resistance inhibitors within nanoparticles have shown potential in achieving coordinated pharmacokinetic and pharmacodynamic profiles. This review discusses the mechanisms of drug resistance, the limitations of current inhibitors, and the advantages of nanoparticle delivery systems in overcoming these challenges. By advancing these technologies, we can enhance treatment outcomes and move towards more effective cancer therapies.

Overcoming ABCB1 mediated multidrug resistance in castration resistant prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-related death in American men. PCa that relapses after hormonal therapies, referred to as castration resistant PCa (CRPC), often presents with metastases (mCRPC) that are the major cause of mortality. The few available therapies for mCRPC patients include taxanes docetaxel (DTX) and cabazitaxel (CBZ). However, development of resistance limits their clinical use. Mechanistically, resistance arises through upregulation of multidrug resistance (MDR) proteins such as MDR1/ABCB1, making ABCB1 an attractive therapeutic target. Yet, ABCB1 inhibitors failed to be clinically useful due to low specificity and toxicity issues. To study taxanes resistance, we produced CBZ resistant C4-2B cells (RC4-2B) and documented resistance to both CBZ and DTX in cell culture and in 3D prostaspheres settings. RNAseq identified increased expression of ABCB1 in RC4-2B, that was confirmed by immunoblotting and immunofluorescent analysis. ABCB1-specific inhibitor elacridar reversed CBZ and DTX resistance in RC4-2B cells, confirming ABCB1-mediated resistance mechanism. In a cell-based screen using a curated library of cytotoxic drugs, we found that DNA damaging compounds Camptothecin (CPT) and Cytarabine (Ara-C) overcame resistance as seen by similar cytotoxicity in parental C4-2B and resistant RC4-2B. Further, these compounds were cytotoxic to multiple PC cells resistant to taxanes with high ABCB1 expression and, therefore, can be used to conquer the acquired resistance to taxanes in PCa. Finally, inhibition of cyclin-dependent kinases 4/6 (CDK4/6) with small molecule inhibitors (CDK4/6i) potentiated cytotoxic effect of CPT or Ara-C in both parental and resistant cells. Overall, our findings indicate that DNA damaging agents CPT and Ara-C alone or in combination with CDK4/6i can be suggested as a new treatment regimen in CRPC patients, including those that are resistant to taxanes.

Exploring the potential of P-glycoprotein inhibitors in the targeted delivery of anti-cancer drugs: A comprehensive review

Due to the high prevalence of cancer, progress in the management of cancer is the need of the hour. Most cancer patients develop chemotherapeutic drug resistance, and many remain insidious due to overexpression of Multidrug Resistance Protein 1 (MDR1), also known as Permeability-glycoprotein (P-gp) or ABCB1 transporter (ATP-binding cassette subfamily B member 1). P-gp, a transmembrane protein that protects vital organs from outside chemicals, expels medications from malignant cells. The blood-brain barrier (BBB), gastrointestinal tract (GIT), kidneys, liver, pancreas, and cancer cells overexpress P-gp on their apical surfaces, making treatment inefficient and resistant. Compounds that compete with anticancer medicines for transportation or directly inhibit P-gp may overcome biological barriers. Developing nanotechnology-based formulations may help overcome P-gp-mediated efflux and improve bioavailability and cell chemotherapeutic agent accumulation. Nanocarriers transport pharmaceuticals via receptor-mediated endocytosis, unlike passive diffusion, which bypasses ABCB1. Anticancer drugs and P-gp inhibitors in nanocarriers may synergistically increase drug accumulation and chemotherapeutic agent toxicity. The projection of desirable binding and effect may be procured initially by molecular docking of the inhibitor with P-gp, enabling the reduction of preliminary trials in formulation development. Here, P-gp-mediated efflux and several possible outcomes to overcome the problems associated with currently prevalent cancer treatments are highlighted.

LncRNA FTH1P3: A New Biomarker for Cancer-Related Therapeutic Development

Cancer is a persistent and urgent health problem that affects the entire world. Not long ago, regulatory biomolecules referred to as long noncoding RNAs (lncRNAs) might have value for their innate abundance and stability. These single-stranded RNAs potentially interfere with several physiological and biochemical cellular processes involved in many human pathological situations, particularly cancer diseases. Ferritin heavy chain1 pseudogene 3 (FTH1P3), a lncRNA that is ubiquitously transcribed and belongs to the ferritin heavy chain (FHC) family, represents a novel class of lncRNAs primarily found in oral squamous cell carcinoma. Further research has shown that FTH1P3 is involved in other malignancies such as uveal melanoma, glioma, esophageal squamous cell carcinoma, non-small cell lung cancer, breast cancer, laryngeal squamous cell carcinoma, and cervical cancer. Accordingly, FTH1P3 significantly enhances cancer symptoms, including cell proliferation, invasion, metastasis, chemoresistance, and inhibition of apoptosis through many specific mechanisms. Notably, the clinical data significantly demonstrated the association of FTH1P3 overexpression with poor prognosis and poor overall survival within the examined samples. Here, we summarize all the research published to date (13 articles) on FTH1P3, focusing on the biological function underlying the regulatory mechanism and its possible clinical relevance.

Suppression of TNBC metastasis by doxazosin, a novel dual inhibitor of c-MET/EGFR

BACKGROUND

Triple-negative breast cancer (TNBC) is characterized by aggressive growth and a high propensity for recurrence and metastasis. Simultaneous overexpression of c-MET and EGFR in TNBC is associated with worse clinicopathological features and unfavorable outcomes. Although the development of new c-MET inhibitors and the emergence of 3rd-generation EGFR inhibitors represent promising treatment options, the high costs involved limit the accessibility of these drugs. In the present study, we sought to investigate the therapeutic potential of doxazosin (DOXA), a generic drug for benign prostate hyperplasia, in targeting TNBC.

METHODS

The effect of DOXA on TNBC cell lines in vitro was evaluated in terms of cell viability, apoptosis, c-MET/EGFR signaling pathway, molecular docking studies and impact on cancer stem cell (CSC)-like properties. An in vivo metastatic model with CSCs was used to evaluate the efficacy of DOXA.

RESULTS

DOXA exhibits notable anti-proliferative effects on TNBC cells by inducing apoptosis via caspase activation. Molecular docking studies revealed the direct interaction of DOXA with the tyrosine kinase domains of c-MET and EGFR. Consequently, DOXA disrupts important survival pathways including AKT, MEK/ERK, and JAK/STAT3, while suppressing CSC-like characteristics including CD44high/CD24low subpopulations, aldehyde dehydrogenase 1 (ALDH1) activity and formation of mammospheres. DOXA administration was found to suppress tumor growth, intra- and peri-tumoral angiogenesis and distant metastasis in an orthotopic allograft model with CSC-enriched populations. Furthermore, no toxic effects of DOXA were observed in hepatic or renal function.

CONCLUSIONS

Our findings highlight the potential of DOXA as a therapeutic option for metastatic TNBC, warranting further investigation.

Tumor microenvironment-induced tumor cell plasticity: relationship with hypoxic stress and impact on tumor resistance

The role of tumor interaction with stromal components during carcinogenesis is crucial for the design of efficient cancer treatment approaches. It is widely admitted that tumor hypoxic stress is associated with tumor aggressiveness and thus impacts susceptibility and resistance to different types of treatments. Notable biological processes that hypoxia functions in include its regulation of tumor heterogeneity and plasticity. While hypoxia has been reported as a major player in tumor survival and dissemination regulation, the significance of hypoxia inducible factors in cancer stem cell development remains poorly understood. Several reports indicate that the emergence of cancer stem cells in addition to their phenotype and function within a hypoxic tumor microenvironment impacts cancer progression. In this respect, evidence showed that cancer stem cells are key elements of intratumoral heterogeneity and more importantly are responsible for tumor relapse and escape to treatments. This paper briefly reviews our current knowledge of the interaction between tumor hypoxic stress and its role in stemness acquisition and maintenance. Our review extensively covers the influence of hypoxia on the formation and maintenance of cancer stem cells and discusses the potential of targeting hypoxia-induced alterations in the expression and function of the so far known stem cell markers in cancer therapy approaches. We believe that a better and integrated understanding of the effect of hypoxia on stemness during carcinogenesis might lead to new strategies for exploiting hypoxia-associated pathways and their targeting in the clinical setting in order to overcome resistance mechanisms. More importantly, at the present time, efforts are oriented towards the design of innovative therapeutical approaches that specifically target cancer stem cells.

Advances in drug resistance of triple negative breast cancer caused by pregnane X receptor

Breast cancer is the most common malignancy in women worldwide. Triple-negative breast cancer (TNBC), refers breast cancer negative for estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2, characterized by high drug resistance, high metastasis and high recurrence, treatment of which is a difficult problem in the clinical treatment of breast cancer. In order to better treat TNBC clinically, it is a very urgent task to explore the mechanism of TNBC resistance in basic breast cancer research. Pregnane X receptor (PXR) is a nuclear receptor whose main biological function is to participate in the metabolism, transport and clearance of allobiological agents in PXR. PXR plays an important role in drug metabolism and clearance, and PXR is highly expressed in tumor tissues of TNBC patients, which is related to the prognosis of breast cancer patients. This reviews synthesized the important role of PXR in the process of high drug resistance to TNBC chemotherapeutic drugs and related research progress.

Gibberellin derivative GA-13315 overcomes multidrug resistance in breast cancer by up-regulating BMP6 expression

Chemoresistance represents a major obstacle in breast cancer treatment. Bone morphogenetic protein 6 (BMP6) was reported to participate in the occurrence and development of various tumors. In the present study, the results of transcriptome sequencing, qRT-PCR and western blot analysis revealed that BMP6 was down-regulated in multidrug resistant MCF-7/Adr breast cancer cells and BMP6 overexpression sensitized MCF-7/Adr cells to chemotherapeutic drugs, indicating that BMP6 downregulation was involved in the mechanisms of multidrug resistance (MDR) of MCF-7/Adr breast cancer cells. GA-13315 (GA5) is a new tetracyclic diterpenoid selected from a series of gibberellin derivatives. Here, we found that GA5 exhibited more potent anti-tumor activity in multidrug resistant MCF-7/Adr breast cancer cells and xenografts, indicating that GA5 could overcome MDR. Mechanistically, GA5 increased BMP6 expression, and BPM6 knockdown partially reversed the inhibitory effect of GA5 on cell proliferation. Furthermore, we found that ERK phosphorylation and P-gp expression were increased in MCF-7/Adr cells when compared with MCF-7 cells. Either overexpression of BMP6 or treatment the cells with GA5 significantly decreased ERK phosphorylation and P-gp expression, indicating that GA5 reversed MDR of MCF-7/Adr cells by upregulating BMP6, thereby inhibiting the activation of ERK signaling pathway and reducing P-gp expression. Collectively, our present study demonstrated that the MDR of MCF-7/Adr cells was closely related to the low expression of BMP6, and revealed the molecular mechanisms by which GA5 overcame MDR in breast cancer, providing evidence in supporting the development of GA5 to be a promising agent for overcoming MDR in clinical cancer therapy in the future.

Combating Drug Resistance by Exploiting miRNA-200c-Controlled Phase II Detoxification

Acquired drug resistance constitutes a serious obstacle to the successful therapy of cancer. In the process of therapy resistance, microRNAs can play important roles. In order to combat resistance formation and to improve the efficacy of chemotherapeutics, the mechanisms of the multifaceted hsa-miR-200c on drug resistance were elucidated. Upon knockout of hsa-miR-200c in breast carcinoma cells, a proteomic approach identified altered expression of glutathione S-transferases (GSTs) when cells were treated with the chemotherapeutic drug doxorubicin. In different hsa-miR-200c expression systems, such as knockout, inducible sponge and inducible overexpression, the differential expression of all members of the GST family was evaluated. Expression of hsa-miR-200c in cancer cells led to the repression of a multitude of these GSTs and as consequence, enhanced drug-induced tumor cell death which was evaluated for two chemotherapeutic drugs. Additionally, the influence of hsa-miR-200c on the glutathione pathway, which is part of the phase II detoxification mechanism, was investigated. Finally, the long-term effects of hsa-miR-200c on drug efficacy were studied in vitro and in vivo. Upon doxycycline induction of hsa-miR-200c, MDA-MB 231 xenograft mouse models revealed a strongly reduced tumor growth and an enhanced treatment response to doxorubicin. A combined treatment of these tumors with hsa-miR-200c and doxorubicin resulted in complete regression of the tumor in 60% of the animals. These results identify hsa-miR-200c as an important player regulating the cellular phase II detoxification, thus sensitizing cancer cells not expressing this microRNA to chemotherapeutics and reversing drug resistance through suppression of GSTs.

A comparative study of the ability of recombinant oncolytic adenovirus, doxorubicin and tamoxifen to inhibit the proliferation of breast cancer cells

In this study, we compared the inhibitory effects of recombinant oncolytic adenovirus (Ad‐apoptin‐hTERTp‐E1a, Ad‐VT) with that of doxorubicin (DOX), a first‐line chemotherapy drug, and tamoxifen (TAM), an endocrine therapy drug, on the proliferation of breast cancer cells. We found that Ad‐VT could effectively inhibit the proliferation of breast cancer cells (p < 0.01); the inhibition rate of Ad‐VT on normal mammary epithelial MCF‐10A cells was less than 20%. DOX can effectively inhibit the proliferation of breast cancer cells and also has a strong inhibitory effect on MCF‐10A cells (p < 0.01). TAM also has a strong inhibitory effect on breast cancer cells, among which the oestrogen‐dependent MCF‐7 cell inhibition was stronger (p < 0.01), At higher concentrations, TAM also had a high rate of inhibition (>70%) on the proliferation of MCF‐10A cells. We also found that both recombinant adenovirus and both drugs could successfully induce tumour cell apoptosis. Further Western blot results showed that the recombinant adenovirus killed breast cancer cells through the endogenous apoptotic pathway. Analysis of the nude mouse subcutaneous breast cancer model showed that Ad‐VT significantly inhibited tumour growth (the luminescence rate of cancer cells was reduced by more than 90%) and improved the survival rate of tumour‐bearing mice (p < 0.01). Compared with DOX and TAM, Ad‐VT has a significant inhibitory effect on breast cancer cells, but almost no inhibitory effect on normal breast epithelial cells, and this inhibitory effect is mainly through the endogenous apoptotic pathway. These results indicate that Ad‐VT has significant potential as a drug for the treatment of breast cancer.

A natural product, voacamine, sensitizes paclitaxel-resistant human ovarian cancer cells

Most women with ovarian cancer are treated with chemotherapy before or after surgery. Unfortunately, chemotherapy treatment can cause negative side effects and the onset of multidrug resistance (MDR). The aim of this study is to evaluate the chemosensitizing effect of a natural compound, voacamine (VOA), in ovarian (A2780 DX) and colon (LoVo DX) cancer drug-resistant cell lines which overexpress P-glycoprotein (P-gp), in combination with paclitaxel (PTX), or doxorubicin (DOX) or 5-fluorouracil (5-FU). VOA, a bisindole alkaloid extracted from Peschiera fuchsiaefolia, has already been shown to be effective in enhancing the effect of doxorubicin, because it interferes with the P-gp function. Ovarian cancer cytotoxicity test shows that single treatments with VOA, DOX and PTX do not modify cell viability, while pretreatment with VOA, and then PTX or DOX for 72 h, induces a decrease. In colon cancer, since 5-FU is not a-substrate for P-gp, VOA has no sensitizing effect while in VOA + DOX there is a decrease in viability. Annexin V/PI test, cell cycle analysis, activation of cleaved PARP1 confirm that VOA plus PTX induce apoptotic cell death. Confocal microscopy observations show the different localization of NF-kB after treatment with VOA + PTX, confirming the inhibition of nuclear translocation induced by VOA pretreatment. Our data show the specific effect of VOA which only works on drugs known to be substrates of P-gp.