Single-step doxorubicin-selected cancer cells overexpress the ABCG2 drug transporter through epigenetic changes

The Effects of Photodynamic Therapy with Low-Level Diode Laser Compared with Doxorubicin on HT-29 Colorectal Adenocarcinoma Cells Viability

Background and Objective: Colorectal adenocarcinoma is considered one of the major causes of cancer-related lethality among other type of malignancies. Given the several limitations and adverse outcomes of conventional therapeutic regimens against colorectal cancer, the focus of many investigations has been attributed to the introduction of a novel combined regimen with harmless agents. The purpose of the present study was to investigate the effect of combined doxorubicin (DOX) treatment and photodynamic therapy (PDT) on colorectal adenocarcinoma cells. Material and Methods: HT-29 cells were exposed to different concentrations of DOX, low-level (630 nm) diode laser, and methylene blue (MB) as a photosensitizer substrate separately and a combination of them. The cytotoxic effect of the DOX, laser, MB, and their combination and the IC50 value for each treatment group were calculated by 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT). The malondialdehyde (MDA) content as a biomarker of the lipid peroxidation process and liberated lactate dehydrogenase (LDH) enzyme into supernatant was determined. Results: The results of our study evidenced that a combination of photodynamic light (laser plus MB) and DOX caused a significant reduction in the percentage of HT-29 viable cells compared with control and other treatment groups. In addition, this mentioned combination led to a considerable decrease in IC50 of DOX. Increased cell membrane lipid peroxidation and cell destruction processes in the combination therapy group were proven through significant elevation of MDA content and LDH activity in the medium, respectively. Conclusion: The findings of the present study suggested that DOX combined with PDT had a better therapeutic impact on HT-29 colorectal adenocarcinoma cells. Hence, the simultaneous application of PDT along with antineoplastic drugs improves the chemosensitivity of cancerous cells via the disruption of their membrane and triggering death processes that lead to the decrease of chemotherapeutic agents required doses and undesirable effects.

Growth Hormone Upregulates Melanoma Drug Resistance and Migration via Melanoma-Derived Exosomes

Drug resistance in melanoma is a major hindrance in cancer therapy. Growth hormone (GH) plays a pivotal role in contributing to the resistance to chemotherapy. Knocking down or blocking the GH receptor has been shown to sensitize the tumor cells to chemotherapy. Extensive studies have demonstrated that exosomes, a subset of extracellular vesicles, play an important role in drug resistance by transferring key factors to sensitize cancer cells to chemotherapy. In this study, we explore how GH modulates exosomal cargoes from melanoma cells and their role in drug resistance. We treated the melanoma cells with GH, doxorubicin, and the GHR antagonist, pegvisomant, and analyzed the exosomes released. Additionally, we administered these exosomes to the recipient cells. The GH-treated melanoma cells released exosomes with elevated levels of ABC transporters (ABCC1 and ABCB1), N-cadherin, and MMP2, enhancing drug resistance and migration in the recipient cells. GHR antagonism reduced these exosomal levels, restoring drug sensitivity and attenuating migration. Overall, our findings highlight a novel role of GH in modulating exosomal cargoes that drive chemoresistance and metastasis in melanoma. This understanding provides insights into the mechanisms of GH in melanoma chemoresistance and suggests GHR antagonism as a potential therapy to overcome chemoresistance in melanoma treatment.

Exploring the multifaceted role of obesity in breast cancer progression

Obesity is a multifaceted metabolic disorder characterized by excessive accumulation of adipose tissue. It is a well-established risk factor for the development and progression of breast cancer. Adipose tissue, which was once regarded solely as a passive energy storage depot, is now acknowledged as an active endocrine organ producing a plethora of bioactive molecules known as adipokines that contribute to the elevation of proinflammatory cytokines and estrogen production due to enhanced aromatase activity. In the context of breast cancer, the crosstalk between adipocytes and cancer cells within the adipose microenvironment exerts profound effects on tumor initiation, progression, and therapeutic resistance. Moreover, adipocytes can engage in direct interactions with breast cancer cells through physical contact and paracrine signaling, thereby facilitating cancer cell survival and invasion. This review endeavors to summarize the current understanding of the intricate interplay between adipocyte-associated factors and breast cancer progression. Furthermore, by discussing the different aspects of breast cancer that can be adversely affected by obesity, this review aims to shed light on potential avenues for new and novel therapeutic interventions.

CD74-AKT Axis Is a Potential Therapeutic Target in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) cells are often resistant to FAS (CD95)-mediated apoptosis, but the underlying molecular mechanism(s) is not fully understood yet. Notably, the expression of the type II transmembrane protein, CD74, is correlated with chemotherapy-resistant and more invasive forms of cancers via unknown mechanisms. Here, we analyzed gene expression pattern of cancer patients and/or patient-derived xenograft (PDX) models and found that mRNA and protein levels of CD74 are highly expressed in TNBC and correlated with cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT) properties. Mechanistically, we found that AKT activation is likely critical for maintaining CD74 expression and protein stability to favor its oncogenic functions. Physiologically, epidermal growth factor (EGF) along with CD74 could activate AKT signaling, likely through binding of phosphorylated AKT (S473) to CD74, whereas inhibition of AKT could impair stability of CD74. We also revealed that CD74 binds to FAS and interferes with the intrinsic signaling of FAS-mediated apoptosis. As such, selective targeting of the CD74/FAS complex using the AKT inhibitor along with the CD74-derived peptide could synergistically restore and activate FAS-mediated apoptosis. Therefore, our approach of mobilizing apoptosis pathways likely provides a rationale for TNBC treatment by targeting the CD74/FAS and CD74-AKT axes.

ABC transporters are predictors of treatment failure in acute myeloid leukaemia

INTRODUCTION

To date, no chemoresistance predictors are included in acute myeloid leukaemia (AML) prognostic scoring systems to distinguish responding and refractory AML patients prior to chemotherapy. ABC transporters have been described as altering AML chemosensitivity; however, a relevant study investigating their role at various molecular levels was lacking.

METHODS

Gene expression, genetic variants, methylation and activity of ABCA2, ABCA5, ABCB1, ABCB6, ABCC1, ABCC3 and ABCG2 were analysed in AML blasts and healthy myeloblasts. Differences between responding and refractory AML in a cohort of 113 patients treated with 3 + 7 induction therapy were explored.

RESULTS

ABCC3 variant rs2301837 (p = 0.049), ABCG2 variant rs11736552 (p = 0.044), higher ABCA2 (p = 0.021), ABCC1 (p = 0.017), and ABCG2 expression (p = 0.023) and a higher number of concurrently overexpressed transporters (p = 0.002) were predictive of treatment failure by multivariate analysis. Expression of ABCA5 (p = 0.003), ABCB6 (p = 0.001) and ABCC3 (p < 0.0001) increased significantly after chemotherapy. Higher ABCG2 promoter methylation correlated with lower ABCG2 expression (p = 0.0001). ABCC1 was identified as the most active transporter in AML blasts by functional analysis.

CONCLUSIONS

ABC transporters, especially ABCC1 seem to contribute substantially to AML chemoresistance. A detailed understanding of chemoresistance mechanisms and the clinical implications of chemosensitivity predictors may lead to alternative therapeutic approaches for AML patients with unveiled chemoresistance signatures.

I-CBP112 declines overexpression of ATP-binding cassette transporters and sensitized drug-resistant MDA-MB-231 and A549 cell lines to chemotherapy drugs

Despite extensive efforts and ongoing progress in personalized anticancer approaches, chemotherapy remains the first line or the only treatment for some tumors that may develop resistance to chemotherapeutics in time due to inter alia overexpression of ATP-binding cassette transporters. Using clinically-relevant resistant models of triple negative breast cancer (MDA-MB-231; TNBC) as well as non-small cell lung cancer (A549; NSCLC), we tested the efficacy of I-CBP112 - CBP/EP300 bromodomain inhibitor to overcome drug resistance by declining ABC gene transcription. I-CBP112 significantly reduced ABCB1, ABCC1, ABCC2, ABCC3, ABCC5 and ABCG2 in all resistant lines, as well as ABCC10 in TNBC and ABCC4 in paclitaxel-resistant NSCLC, thereby increasing intracellular drug accumulation and cytotoxicity in 2D and 3D cultures. This was phenocopied only by the joint effect of ABC inhibitors such as tariquidar (ABCB1 - P-glycoprotein and ABCG2) and MK-571 (ABCC), whereas single inhibition of ABCB1/ABCG2 or ABCC proteins did not affect drug accumulation, thereby implying the need of simultaneous deficiency in activity of majority of drug pumps for enhanced drug retention. I-CBP112 failed to directly inhibit activity of ABCB1, ABCG2 and ABCC subfamily members at the same time. Importantly, I-CBP112 treated cancer cells polarized human macrophages into proinflammatory phenotypes. Moreover, I-CBP112 remained non-toxic to primary cell lines, nor did it enhance anticancer drug toxicity to blood-immune cells. In silico assay of ADMET properties confirmed the desired pharmacokinetic features of I-CBP112. The results suggest that the CBP/p300 inhibitor is a promising co-adjuvant to chemotherapy in drug-resistant cancer phenotypes, capable of decreasing ABC transporter expression.

Carborane-Based ABCG2-Inhibitors Sensitize ABC-(Over)Expressing Cancer Cell Lines for Doxorubicin and Cisplatin

The ABCG2 transporter protein, as part of several known mechanisms involved in multidrug resistance, has the ability to transport a broad spectrum of substrates out of the cell and is, therefore, considered as a potential target to improve cancer therapies or as an approach to combat drug resistance in cancer. We have previously reported carborane-functionalized quinazoline derivatives as potent inhibitors of human ABCG2 which effectively reversed breast cancer resistance protein (BCRP)-mediated mitoxantrone resistance. In this work, we present the evaluation of our most promising carboranyl BCRP inhibitors regarding their toxicity towards ABCG2-expressing cancer cell lines (MCF-7, doxorubicin-resistant MCF-7 or MCF-7 Doxo, HT29, and SW480) and, consequently, with the co-administration of an inhibitor and therapeutic agent, their ability to increase the efficacy of therapeutics with the successful inhibition of ABCG2. The results obtained revealed synergistic effects of several inhibitors in combination with doxorubicin or cisplatin. Compounds DMQCa, DMQCc, and DMQCd showed a decrease in IC50 value in ABCB1- and ABCG2-expressing SW480 cells, suggesting a possible targeting of both transporters. In an HT29 cell line, with the highest expression of ABCG2 among the tested cell lines, using co-treatment of doxorubicin and DMQCd, the effective inhibitory concentration of the antineoplastic agent could be reduced by half. Interestingly, co-treatment of compound QCe with cisplatin, which is not an ABCG2 substrate, showed synergistic effects in MCF-7 Doxo and HT29 cells (IC50 values halved or reduced by 20%, respectively). However, a literature-known upregulation of cisplatin-effluxing ABC transporters and their effective inhibition by the carborane derivatives emerges as a possible reason.

Exposure to anticancer drugs modulates the expression of ACSL4 and ABCG2 proteins in adrenocortical carcinoma cells

Adrenocortical carcinoma (ACC) is a rare and malignant disease, with more than 50 % of patients developing hormone-secreting tumors. These tumors are genetically heterogeneous and potentially lethal, as metastasis is often underway at the time of diagnosis. While chemoresistance can be multifactorial, Acyl CoA synthetase 4 (ACSL4) is known to contribute to the generation of highly aggressive cellular phenotypes, while increased expression and activity of multidrug transporters such as ATP-binding cassette subfamily G member 2 (ABCG2) are known to play a key role. Therefore, the objective of this work was to determine changes in the expression of ACSL4 and ABCG2 in ACC cell lines after exposure to antitumor drugs. Bioinformatics analysis of public database GSE140818 revealed higher ACSL4 and ABCG2 expression in HAC15 cells resistant to mitotane when compared to wild type cells. In addition, our studies revealed an increase in ACSL4 and ABCG2 expression in lowly aggressive H295R cells undergoing early treatment with non-lethal concentrations of mitotane, doxorubicin and cisplatin. Comparable results were obtained in lowly aggressive breast cancer cells MCF-7. The increase in ACSL4 and ABCG2 expression favored tumor cell viability, proliferation and compound efflux, an effect partially offset by ACSL4 and ABCG2 inhibitors. These results provide relevant data on the undesired molecular effects of antitumor drugs and may fuel future studies on patients' early response to antitumor treatment.

Extracellular Vesicles and Cancer Multidrug Resistance: Undesirable Intercellular Messengers?

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

Resistance to TOP-1 Inhibitors: Good Old Drugs Still Can Surprise Us

Irinotecan (SN-38) is a potent and broad-spectrum anticancer drug that targets DNA topoisomerase I (Top1). It exerts its cytotoxic effects by binding to the Top1-DNA complex and preventing the re-ligation of the DNA strand, leading to the formation of lethal DNA breaks. Following the initial response to irinotecan, secondary resistance is acquired relatively rapidly, compromising its efficacy. There are several mechanisms contributing to the resistance, which affect the irinotecan metabolism or the target protein. In addition, we have demonstrated a major resistance mechanism associated with the elimination of hundreds of thousands of Top1 binding sites on DNA that can arise from the repair of prior Top1-dependent DNA cleavages. Here, we outline the major mechanisms of irinotecan resistance and highlight recent advancements in the field. We discuss the impact of resistance mechanisms on clinical outcomes and the potential strategies to overcome resistance to irinotecan. The elucidation of the underlying mechanisms of irinotecan resistance can provide valuable insights for the development of effective therapeutic strategies.

Non-uniformity in in vitro drug-induced cytotoxicity as evidenced by differences in IC50 values - implications and way forward

Cell lines have proven indispensable for in vitro experiments and their utility as experimental models range from understanding the fundamental cell functioning to drug discovery. One of the most common utility of cell lines is for in vitro drug testing. Drug testing involves determining the cytotoxic effects of the drugs and such a measurement is expressed as the IC₅₀ values of drugs. Although determination of IC₅₀ values of drugs on cell lines is one of the most common in vitro experimental approaches, a significant amount of variations can be observed in the results obtained from such studies. Although the variations in the IC₅₀ values of a drug on different cells lines can and should vary, the non-uniformity of such results reported from different studies using a particular drug on a specific cell line is a matter of concern. We present the IC₅₀ values of 5 most commonly used drugs 5-fluorouracil, bleomycin, cisplatin, doxorubicin and methotrexate obtained from several in vitro cell line-based studies. Some of the factors which contribute to the non-uniformity of the IC₅₀ values for a particular drug from different studies are discussed as three types of factors, the biological, non-biological and human factors. Also, ways in which such variations can be reduced to obtain universally common, reliable results are presented.

Characterization of a Potent, Selective, and Safe Inhibitor, Ac15(Az8)2, in Reversing Multidrug Resistance Mediated by Breast Cancer Resistance Protein (BCRP/ABCG2)

Overexpression of breast cancer resistance transporter (BCRP/ABCG2) in cancers has been explained for the failure of chemotherapy in clinic. Inhibition of the transport activity of BCRP during chemotherapy should reverse multidrug resistance. In this study, a triazole-bridged flavonoid dimer Ac15(Az8)2 was identified as a potent, nontoxic, and selective BCRP inhibitor. Using BCRP-overexpressing cell lines, its EC50 for reversing BCRP-mediated topotecan resistance was 3 nM in MCF7/MX100 and 72 nM in S1M180 in vitro. Mechanistic studies revealed that Ac15(Az8)2 restored intracellular drug accumulation by inhibiting BCRP-ATPase activity and drug efflux. It did not down-regulate the cell surface BCRP level to enhance drug retention. It was not a transport substrate of BCRP and showed a non-competitive relationship with DOX in binding to BCRP. A pharmacokinetic study revealed that I.P. administration of 45 mg/kg of Ac15(Az8)2 resulted in plasma concentration above its EC50 (72 nM) for longer than 24 h. It increased the AUC of topotecan by 2-fold. In an in vivo model of BCRP-overexpressing S1M180 xenograft in Balb/c nude mice, it significantly reversed BCRP-mediated topotecan resistance and inhibited tumor growth by 40% with no serious body weight loss or death incidence. Moreover, it also increased the topotecan level in the S1M180 xenograft by 2-fold. Our results suggest that Ac15(Az8)2 is a promising candidate for further investigation into combination therapy for treating BCRP-overexpressing cancers.

The effect of ciprofloxacin on doxorubicin cytotoxic activity in the acquired resistance to doxorubicin in DU145 prostate carcinoma cells

The present study aimed to assess the influence of ciprofloxacin (CIP) against the doxorubicin (DOX)-resistant androgen-independent prostate cancer DU145 cells. The DOX-resistant DU145 (DU145/DOX20) cells were established by exposing DU145 cells to the increasing concentrations of DOX. The antiproliferative effect of CIP was examined through employing MTT, colony formation, and 3D culture assays. DU145/DOX20 cells exhibited a twofold higher IC₅₀ value for DOX, an increased ABCB1 transporter activity, and some morphological changes accompanied by a decrease in spheroid size, adhesive and migration potential compared to DU145 cells. CIP (5 and 25 µg mL^-1) resulted in a higher reduction in the viability of DU145/DOX20 cells than in DU145 cells. DU145/DOX20 cells were more resistant to CIP in 3D culture compared to the 2D one. No spheroid formation was observed for DU145/DOX20 cells treated with DOX and CIP combination. CIP and DOX, alone or in combination, significantly reduced the growth of DU145 spheroids. CIP in combination with 20 nM DOX prevented the colony formation of DU145 cells. The clonogenicity of DU145/DOX20 cells could not be estimated due to their low adhesive potential. CIP alone caused a significant reduction in the migration of DU145 cells and resulted in a more severe decrease in the wound closure ability of DOX-exposed ones. We identified that CIP enhanced DOX sensitivity in DU145 and DU145/DOX20 cells. This study suggested the co-delivery of low concentrations of CIP and DOX may be a promising strategy in treating the DOX-resistant and -sensitive hormone-refractory prostate cancer.

Bioprinting Decellularized Breast Tissue for the Development of Three-Dimensional Breast Cancer Models

The tumor extracellular matrix (ECM) plays a vital role in tumor progression and drug resistance. Previous studies have shown that breast tissue-derived matrices could be an important biomaterial to recreate the complexity of the tumor ECM. We have developed a method for decellularizing and delipidating a porcine breast tissue (TDM) compatible with hydrogel formation. The addition of gelatin methacrylamide and alginate allows this TDM to be bioprinted by itself with good printability, shape fidelity, and cytocompatibility. Furthermore, this bioink has been tuned to more closely recreate the breast tumor by incorporating collagen type I (Col1). Breast cancer cells (BCCs) proliferate in both TDM bioinks forming cell clusters and spheroids. The addition of Col1 improves the printability of the bioink as well as increases BCC proliferation and reduces doxorubicin sensitivity due to a downregulation of HSP90. TDM bioinks also allow a precise three-dimensional printing of scaffolds containing BCCs and stromal cells and could be used to fabricate artificial tumors. Taken together, we have proven that these novel bioinks are good candidates for biofabricating breast cancer models.

ABC transporters in breast cancer: their roles in multidrug resistance and beyond

ATP-binding cassette (ABC) transporters are membrane-spanning proteins involved in cholesterol homeostasis, transport of various molecules in and out of cells and organelles, oxidative stress, immune recognition, and drug efflux. They are long implicated in the development of multidrug resistance in cancer chemotherapy. Existing clinical and molecular evidence has also linked ABC transporters with cancer pathogenesis, prognostics, and therapy. In this review, we aim to provide a comprehensive update on all ABC transporters and their roles in drug resistance in breast cancer (BC). For solid tumours such as BC, various ABC transporters are highly expressed in less differentiated subtypes and metastases. ABCA1, ABCB1 and ABCG2 are key players in BC chemoresistance. Restraining these transporters has evolved as a possible mechanism to reverse this phenomenon. Further, ABCB1 and ABCC1 are important in BC prognosis. Newer therapeutic approaches have been developed to target all these molecules to dysregulate their effect, reduce cell viability, induce apoptosis, and increase drug sensitivity. In the future, targeted therapy for specific genetic variations and upstream or downstream molecules can help improve patient prognosis.

Cellular irinotecan resistance in colorectal cancer and overcoming irinotecan refractoriness through various combination trials including DNA methyltransferase inhibitors: a review

Treatment with pharmacological drugs for colorectal cancer (CRC) remains unsatisfactory. A major cause of failure in pharmacotherapy is the resistance of colon cancer cells to the drugs, creating an urgent issue. In this review, we summarize previous studies on the resistance of CRC cells to irinotecan and discuss possible reasons for refractoriness. Our review presents the following five major causes of irinotecan resistance in human CRC: (1) cellular irinotecan resistance is induced mainly through the increased expression of the drug efflux transporter, ABCG2; (2) cellular irinotecan resistance is also induced in association with a nuclear receptor, pregnane/steroid X receptor (PXR/SXR), which is enriched in the CYP3A4 gene enhancer region in CRC cells by exposing the cells to SN-38; (3) irinotecan-resistant cells possess either reduced DNA topoisomerase I (Top1) expression at both the mRNA and protein levels or Top1 missense mutations; (4) alterations in the tumor microenvironment lead to drug resistance through intercellular vesicle-mediated transmission of miRNAs; and (5) CRC stem cells are the most difficult targets to successfully treat CRC. In the clinical setting, CRC gradually develops resistance to initially effective irinotecan-based therapy. To solve this problem, several clinical trials, such as irinotecan plus cetuximab vs. cetuximab monotherapy, have been conducted. Another clinical trial on irinotecan plus guadecitabine, a DNA-methyltransferase inhibitor, has also been conducted.

Modified Bovine Milk Exosomes for Doxorubicin Delivery to Triple-Negative Breast Cancer Cells

Biological nanoparticles, such as exosomes, offer an approach to drug delivery because of their innate ability to transport biomolecules. Exosomes are derived from cells and an integral component of cellular communication. However, the cellular cargo of human exosomes could negatively impact their use as a safe drug carrier. Additionally, exosomes have the intrinsic yet enigmatic, targeting characteristics of complex cellular communication. Hence, harnessing the natural transport abilities of exosomes for drug delivery requires predictably targeting these biological nanoparticles. This manuscript describes the use of two chemical modifications, incorporating a neuropilin receptor agonist peptide (iRGD) and a hypoxia-responsive lipid for targeting and release of an encapsulated drug from bovine milk exosomes to triple-negative breast cancer cells. Triple-negative breast cancer is a very aggressive and deadly form of malignancy with limited treatment options. Incorporation of both the iRGD peptide and hypoxia-responsive lipid into the lipid bilayer of bovine milk exosomes and encapsulation of the anticancer drug, doxorubicin, created the peptide targeted, hypoxia-responsive bovine milk exosomes, iDHRX. Initial studies confirmed the presence of iRGD peptide and the exosomes' ability to target the αvβ3 integrin, overexpressed on triple-negative breast cancer cells' surface. These modified exosomes were stable under normoxic conditions but fragmented in the reducing microenvironment created by 10 mM glutathione. In vitro cellular internalization studies in monolayer and three-dimensional (3D) spheroids of triple-negative breast cancer cells confirmed the cell-killing ability of iDHRX. Cell viability of 50% was reached at 10 μM iDHRX in the 3D spheroid models using four different triple-negative breast cancer cell lines. Overall, the tumor penetrating, hypoxia-responsive exosomes encapsulating doxorubicin would be effective in reducing triple-negative breast cancer cells' survival.

Toosendanin, a late-stage autophagy inhibitor, sensitizes triple-negative breast cancer to irinotecan chemotherapy

Background

Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer that develops resistance to chemotherapy frequently. Autophagy has been reported as a pro-survival response to chemotherapeutic drugs in TNBC, and suppression of autophagy can be a strategy to overcome drug resistance.

Methods

The efficacy of toosendanin (TSN) in blocking autophagy flux was measured by western blot analysis of autophagy markers, and the fluorescent imaging of RFP-GFP-LC3 probe. The co-localization of autophagosomes and lysosomes was analyzed by fluorescent imaging. Then, lysosome function was determined by measuring the lysosomal pH value and the activity of lysosomal hydrolytic proteases. For in vitro study, human triple-negative breast cancer MDA-MB-231 and MDA-MB-436 cell lines were used for evaluating the anti-proliferative effect. For in vivo study, the RFP-GFP-LC3 MDA-MB-231 xenograft nude mice received intraperitoneal injection of irinotecan (10 mg/kg), TSN (0.5 mg/kg) or a combination, and the autophagy activity and cell apoptosis were determined in tumor tissue. The degree of pathological injury of tissue was evaluated by liver index.

Results

The natural autophagy inhibitor TSN, a triterpenoid extracted from Melia toosenda Sieb. et Zucc, potently inhibited late-stage autophagy in TNBC cells. This effect was achieved via elevating lysosome pH rather than blocking the fusion of autophagosomes and lysosomes. We further investigated the effects of TSN on the in vitro and in vivo TNBC models, in combination with chemotherapeutic drug irinotecan (or its active metabolite 7-ethyl-10-hydroxycamptothecin), a topoisomerase I inhibitor showing therapeutic potential for TNBC. The data showed that TSN blocked 7-ethyl-10-hydroxycamptothecin (SN-38)/irinotecan-induced protective autophagy, and significantly induced apoptosis in TNBC cells and tumor xenograft models when compared to SN-38/irinotecan alone group.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-022-00605-8.

The Emerging Roles and Therapeutic Implications of Epigenetic Modifications in Ovarian Cancer

Ovarian cancer (OC) is one of the most lethal gynecologic malignancies globally. In spite of positive responses to initial therapy, the overall survival rates of OC patients remain poor due to the development of drug resistance and consequent cancer recurrence. Indeed, intensive studies have been conducted to unravel the molecular mechanisms underlying OC therapeutic resistance. Besides, emerging evidence suggests a crucial role for epigenetic modifications, namely, DNA methylation, histone modifications, and non-coding RNA regulation, in the drug resistance of OC. These epigenetic modifications contribute to chemoresistance through various mechanisms, namely, upregulating the expression of multidrug resistance proteins (MRPs), remodeling of the tumor microenvironment, and deregulated immune response. Therefore, an in-depth understanding of the role of epigenetic mechanisms in clinical therapeutic resistance may improve the outcome of OC patients. In this review, we will discuss the epigenetic regulation of OC drug resistance and propose the potential clinical implications of epigenetic therapies to prevent or reverse OC drug resistance, which may inspire novel treatment options by targeting resistance mechanisms for drug-resistant OC patients.

Genomic stability at the coding regions of the multidrug transporter gene ABCB1: insights into the development of alternative drug resistance mechanisms in human leukemia cells

AIM

Despite considerable efforts to reverse clinical multidrug resistance (MDR), targeting the predominant multidrug transporter ABCB1/P-glycoprotein (P-gp) using small molecule inhibitors has been unsuccessful, possibly due to the emergence of alternative drug resistance mechanisms. However, the non-specific P-gp inhibitor cyclosporine (CsA) showed significant clinical benefits in patients with acute myeloid leukemia (AML), which likely represents the only proof-of-principle clinical trial using several generations of MDR inhibitors. Nevertheless, the mutational mechanisms that may underlie unsuccessful MDR modulation by CsA are not elucidated because of the absence of CsA-relevant cellular models. In this study, our aims were to establish CsA-resistant leukemia models and to examine the presence or absence of ABCB1 exonic mutations in these models as well as in diverse types of human cancer samples including AMLs.

METHODS

Drug-resistant lines were established by stepwise drug co-selection and characterized by drug sensitivity assay, rhodamine-123 accumulation, [3H]-labeled drug export, ABCB1 cDNA sequencing, and RNase protection assay. The genomic stability of the ABCB1 coding regions was evaluated by exome sequencing analysis of variant allele frequencies in human populations. Moreover, the mutational spectrum of ABCB1 was further assessed in diverse types of cancer samples including AMLs in the Cancer Genome Atlas (TCGA) at the National Cancer Institute.

RESULTS

We report the development of two erythroleukemia variants, RVC and RDC, which were derived by stepwise co-selection of K562/R7 drug-resistant leukemia cells with the etoposide-CsA and doxorubicin-CsA drug combinations, respectively. Interestingly, both RVC and RDC cell lines, which retained P-gp expression, showed altered multidrug-resistant phenotypes that were resistant to CsA modulation. Strikingly, no mutations were found in the ABCB1 coding regions in these variant cells even under long-term stringent drug selection. Genomically, ABCB1 displayed relatively low variant allele frequencies in human populations when compared with several ABC superfamily members. Moreover, ABCB1 also exhibited a very low mutational frequency in AMLs compared with all types of human cancer. In addition, we found that CsA played a role in undermining the selection of highly drug-resistant cells via induction of low-level and unstable drug resistance.

CONCLUSION

Our data indicate that ABCB1 coding regions are genomically stable and relatively resistant to drug-induced mutations. Non-ABCB1 mutational mechanisms are responsible for the drug-resistant phenotypes in both RVC and RDC cell lines, which are also prevalent in clinical AML patients. Accordingly, we propose several relevant models that account for the development of alternative drug resistance mechanisms in the absence of ABCB1 mutations.

Normoxic Tumour Extracellular Vesicles Modulate the Response of Hypoxic Cancer and Stromal Cells to Doxorubicin In Vitro

Extracellular vesicles (EV) secreted in the tumour microenvironment (TME) are emerging as major antagonists of anticancer therapies by orchestrating the therapeutic outcome through altering the behaviour of recipient cells. Recent evidence suggested that chemotherapeutic drugs could be responsible for the EV-mediated tumour-stroma crosstalk associated with cancer cell drug resistance. Here, we investigated the capacity of tumour EV (TEV) secreted by normoxic and hypoxic (1% oxygen) C26 cancer cells after doxorubicin (DOX) treatment to alter the response of naïve C26 cells and RAW 264.7 macrophages to DOX. We observed that C26 cells were less responsive to DOX treatment under normoxia compared to hypoxia, and a minimally cytotoxic DOX concentration that mounted distinct effects on cell viability was selected for TEV harvesting. Homotypic and heterotypic pretreatment of naïve hypoxic cancer and macrophage-like cells with normoxic DOX-elicited TEV rendered these cells slightly less responsive to DOX treatment. The observed effects were associated with strong hypoxia-inducible factor 1-alpha (HIF-1α) induction and B-cell lymphoma-extra-large anti-apoptotic protein (Bcl-xL)-mediated anti-apoptotic response in normoxic DOX-treated TEV donor cells, being also tightly connected to the DOX-TEV-mediated HIF-1α induction, as well as Bcl-xL levels increasing in recipient cells. Altogether, our results could open new perspectives for investigating the role of chemotherapy-elicited TEV in the colorectal cancer TME and their modulatory actions on promoting drug resistance.

The Importance of Breast Adipose Tissue in Breast Cancer

Adipose tissue is a complex endocrine organ, with a role in obesity and cancer. Adipose tissue is generally linked to excessive body fat, and it is well known that the female breast is rich in adipose tissue. Hence, one can wonder: what is the role of adipose tissue in the breast and why is it required? Adipose tissue as an organ consists of adipocytes, an extracellular matrix (ECM) and immune cells, with a significant role in the dynamics of breast changes throughout the life span of a female breast from puberty, pregnancy, lactation and involution. In this review, we will discuss the importance of breast adipose tissue in breast development and its involvement in breast changes happening during pregnancy, lactation and involution. We will focus on understanding the biology of breast adipose tissue, with an overview on its involvement in the various steps of breast cancer development and progression. The interaction between the breast adipose tissue surrounding cancer cells and vice-versa modifies the tumor microenvironment in favor of cancer. Understanding this mutual interaction and the role of breast adipose tissue in the tumor microenvironment could potentially raise the possibility of overcoming breast adipose tissue mediated resistance to therapies and finding novel candidates to target breast cancer.

Targeting lysyl oxidase (LOX) overcomes chemotherapy resistance in triple negative breast cancer

Chemoresistance is a major obstacle in triple negative breast cancer (TNBC), the most aggressive breast cancer subtype. Here we identify hypoxia-induced ECM re-modeler, lysyl oxidase (LOX) as a key inducer of chemoresistance by developing chemoresistant TNBC tumors in vivo and characterizing their transcriptomes by RNA-sequencing. Inhibiting LOX reduces collagen cross-linking and fibronectin assembly, increases drug penetration, and downregulates ITGA5/FN1 expression, resulting in inhibition of FAK/Src signaling, induction of apoptosis and re-sensitization to chemotherapy. Similarly, inhibiting FAK/Src results in chemosensitization. These effects are observed in 3D-cultured cell lines, tumor organoids, chemoresistant xenografts, syngeneic tumors and PDX models. Re-expressing the hypoxia-repressed miR-142-3p, which targets HIF1A, LOX and ITGA5, causes further suppression of the HIF-1α/LOX/ITGA5/FN1 axis. Notably, higher LOX, ITGA5, or FN1, or lower miR-142-3p levels are associated with shorter survival in chemotherapy-treated TNBC patients. These results provide strong pre-clinical rationale for developing and testing LOX inhibitors to overcome chemoresistance in TNBC patients.

The development of chemoresistance is a major hurdle in triple negative breast cancer (TNBC). Here, the authors show that lysyl oxidase (LOX) is overexpressed in chemoresistant TNBCs, and when inhibited reduces collagen cross-linking, fibronectin fibril assembly, and downstream integrin signalling, overcoming resistance.

Germline variant burden in multidrug resistance transporters is a therapy-specific predictor of survival in breast cancer patients

Multidrug resistance due to facilitated drug efflux mediated by ATP-binding cassette (ABC) transporters is a main cause for failure of cancer therapy. Genetic polymorphisms in ABC genes affect the disposition of chemotherapeutics and constitute important biomarkers for therapeutic response and toxicity. Here we correlated germline variability in ABC transporters with disease-specific survival (DSS) in 960 breast cancer (BRCA), 314 clear cell renal cell carcinoma and 325 hepatocellular carcinoma patients. We find that variant burden in ABCC1 is a strong predictor of DSS in BRCA patients, whereas candidate polymorphisms are not associated with DSS. This association is highly drug-specific for subgroups treated with the MRP1 substrates cyclophosphamide (log-rank p = 0.0011) and doxorubicin (log-rank p = 0.0088) independent of age and tumor stage, whereas no association was found in individuals treated with tamoxifen (log-rank p = 0.13). Structural mapping of significant variants revealed multiple variants at residues involved in protein stability, cofactor stabilization or substrate binding. Our results demonstrate that BRCA patients with high variant burden in ABCC1 are less prone to respond appropriately to pharmacological therapy with MRP1 substrates, thus incentivizing the consideration of genomic germline data for precision cancer medicine.

CM082 Enhances the Efficacy of Chemotherapeutic Drugs by Inhibiting the Drug Efflux Function of ABCG2

The overexpression of ATP-binding cassette (ABC) transporters is one of the important mechanisms of multidrug resistance (MDR). Some tyrosine kinase inhibitors (TKIs) such as CM082 might be a potential ABC transporter inhibitor, thus potentially reversing MDR. We used a 3-(4,5-dimethylthiazol-2-yl)-2,5-dimethyltetrazolium bromide (MTT) assay to determine the cytotoxicity and reversal effect of CM082. A xenograft model was established to evaluate the reversal MDR efficacy in vivo. The intracellular accumulation and efflux of ABCG2 substrates were measured by flow cytometry. We investigated the binding sites of ABCG2 via photolabeling ABCG2 with [125I]-iodoarylazidoprazosin (IAAP). Quantitative real-time PCR and western blot were utilized to analyze mRNA and protein expression. We found that CM082 could enhance the efficacy of substrate in ABCG2-overexpressing cells both in vitro and in vivo. Furthermore, CM082 significantly increased intracellular accumulation of ABCG2 substrates by inhibiting the efflux activity. CM082 stimulated ABCG2 ATPase activity and competed with [125I]-IAAP photolabeling of ABCG2 in a concentration-dependent manner. However, CM082 did not alter ABCG2 expression at protein and mRNA levels or inhibit vascular endothelial growth factor (VEGF) downstream signaling of AKT and extracellular signal-regulated kinase (ERK). Further research is encouraged to confirm whether CM082 concomitant with anticancer drugs of ABCG2 substrates could improve the clinical outcomes of cancer treatment in cancer patients with ABCG2 overexpression.

ABC Transporters at the Blood-Brain Interfaces, Their Study Models, and Drug Delivery Implications in Gliomas

Drug delivery into the brain is regulated by the blood-brain interfaces. The blood-brain barrier (BBB), the blood-cerebrospinal fluid barrier (BCSFB), and the blood-arachnoid barrier (BAB) regulate the exchange of substances between the blood and brain parenchyma. These selective barriers present a high impermeability to most substances, with the selective transport of nutrients and transporters preventing the entry and accumulation of possibly toxic molecules, comprising many therapeutic drugs. Transporters of the ATP-binding cassette (ABC) superfamily have an important role in drug delivery, because they extrude a broad molecular diversity of xenobiotics, including several anticancer drugs, preventing their entry into the brain. Gliomas are the most common primary tumors diagnosed in adults, which are often characterized by a poor prognosis, notably in the case of high-grade gliomas. Therapeutic treatments frequently fail due to the difficulty of delivering drugs through the brain barriers, adding to diverse mechanisms developed by the cancer, including the overexpression or expression de novo of ABC transporters in tumoral cells and/or in the endothelial cells forming the blood-brain tumor barrier (BBTB). Many models have been developed to study the phenotype, molecular characteristics, and function of the blood-brain interfaces as well as to evaluate drug permeability into the brain. These include in vitro, in vivo, and in silico models, which together can help us to better understand their implication in drug resistance and to develop new therapeutics or delivery strategies to improve the treatment of pathologies of the central nervous system (CNS). In this review, we present the principal characteristics of the blood-brain interfaces; then, we focus on the ABC transporters present on them and their implication in drug delivery; next, we present some of the most important models used for the study of drug transport; finally, we summarize the implication of ABC transporters in glioma and the BBTB in drug resistance and the strategies to improve the delivery of CNS anticancer drugs.

ncRNAs associated with drug resistance and the therapy of digestive system neoplasms

Digestive system cancer remains a common cancer and the main cause of cancer-related death worldwide. Drug resistance is a major challenge in the therapy of digestive system cancer, and represents a primary obstacle in the treatment of cancer by restricting the efficiency of both traditional chemotherapy and biological therapies. Existing studies indicate that noncoding RNAs play an important role in the evolution and progression of drug resistance in digestive system cancer, mainly by modulating drug transporter-related proteins, DNA damage repair, cell-cycle-related proteins, cell apoptosis-related proteins, drug target-related proteins, and the tumor microenvironment. In this review, we address the potential mechanisms of ncRNAs underlying drug resistance in digestive system tumors and discuss the possible application of ncRNAs against drug resistance in digestive system tumors.

JAK-STAT signalling controls cancer stem cell properties including chemotherapy resistance in myxoid liposarcoma

Myxoid liposarcoma (MLS) shows extensive intratumoural heterogeneity with distinct subpopulations of tumour cells. Despite improved survival of MLS patients, existing therapies have shortcomings as they fail to target all tumour cells. The nature of chemotherapy‐resistant cells in MLS remains unknown. Here, we show that MLS cell lines contained subpopulations of cells that can form spheres, efflux Hoechst dye and resist doxorubicin, all properties attributed to cancer stem cells (CSCs). By single‐cell gene expression, western blot, phospho‐kinase array, immunoprecipitation, immunohistochemistry, flow cytometry and microarray analysis we showed that a subset of MLS cells expressed JAK–STAT genes with active signalling. JAK1/2 inhibition via ruxolitinib decreased, while stimulation with LIF increased, phosphorylation of STAT3 and the number of cells with CSC properties indicating that JAK–STAT signalling controlled the number of cells with CSC features. We also show that phosphorylated STAT3 interacted with the SWI/SNF complex. We conclude that MLS contains JAK–STAT‐regulated subpopulations of cells with CSC features. Combined doxorubicin and ruxolitinib treatment targeted both proliferating cells as well as cells with CSC features, providing new means to circumvent chemotherapy resistance in treatment of MLS patients.

What's new?

Despite improved survival of patients, existing therapies for Myxoid liposarcoma (MLS) present shortcomings as they fail to target all tumour cells. The nature of chemotherapy‐resistant cells in MLS remains unknown, however. Here, the authors show that myxoid liposarcomas are heterogeneous and contain subpopulations of cells with stem cell properties, including chemotherapy resistance. Moreover, JAK‐STAT signalling is active in MLS and regulates the size of the cancer stem cells‐like subpopulation via the SWI/SNF complex. The results shed light on the mechanisms of therapy resistance in MLS and point to JAK‐STAT inhibitors as a new avenue for targeted MLS therapies.

LS. Diverse Targeted Approaches to Battle Multidrug Resistance in Cancer

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The efficacy of successful cancer therapies is frequently hindered by the development of drug resistance in the tumor. The term ‘drug resistance’ is used to illustrate the decreased effectiveness of a drug in curing a disease or alleviating the symptoms of the patient. This phenomenon helps tumors to survive the damage caused by a specific drug or group of drugs. In this context, studying the mechanisms of drug resistance and applying this information to design customized treatment regimens can improve therapeutic efficacy as well as the curative outcome. Over the years, numerous Multidrug Resistance (MDR) mechanisms have been recognized and tremendous effort has been put into developing agents to address them. The integration of data emerging from the elucidation of molecular and biochemical pathways and specific tumor-associated factors has shown tremendous promise within the oncology community for improving patient outcomes. In this review, we provide an overview of the utility of these molecular and biochemical signaling processes as well as tumor-associated factors associated with MDR, for the rational selection of cancer treatment strategies.

Nanogel-mediated delivery of a cocktail of epigenetic drugs plus doxorubicin overcomes drug resistance in breast cancer cells

Epigenetic modifications (e.g., DNA methylation or histone deacetylation) are commonly implicated in cancer chemoresistance. We previously showed that pretreating resistant MCF-7/ADR breast cancer cells with a demethylating agent (5-aza-2'-deoxycytidine (DAC)) or with an inhibitor of histone deacetylase (suberoylanilide hydroxamic acid (SAHA)) sensitized resistant cells to doxorubicin (DOX) treatment. However, even with increasing doses of DOX, a fraction of resistant cells remained nonresponsive to this pretreatment (~ 25% pretreated with DAC, ~ 45% with SAHA). We hypothesized that pretreating resistant cells with a combination of epigenetic drugs (DAC + SAHA) could more effectively overcome drug resistance. We postulated that delivery of epigenetic drugs encapsulated in biodegradable nanogels (NGs) would further enhance their efficacy. MCF-7/ADR cells were first treated with a single drug vs. a combination of epigenetic drugs, either as solutions or encapsulated in NGs, then subjected to DOX, either in solution or in NGs. Antiproliferative data showed that pretreatment with epigenetic drugs in NGs, then with DOX in NGs, was most effective in overcoming resistance; this treatment inhibited cell growth by > 90%, even at low doses of DOX. Cell cycle analysis showed that a major fraction of cells treated with a cocktail of epigenetic drugs + DOX, all in NG formulations, remained in the G2/M cell cycle arrest phase for a prolonged period. The mechanism of better efficacy of epigenetic drugs in NGs could be attributed to their sustained effect. A similar strategy could be developed for other cancer cells in which drug resistance is due to epigenetic modifications.

miR-34a Regulates Multidrug Resistance via Positively Modulating OAZ2 Signaling in Colon Cancer Cells

Although aberrant expression of miR-34a, an essential tumor suppressor miRNA, has been frequently observed in colon cancer (CCa), whether miR-34a can regulate CCa progression by modulating other facets of this malignancy (such as multidrug resistance, MDR) remains unknown. Here, we report for the first time that miR-34a expression was significantly downregulated in clinical CCa samples from oxaliplatin-resistant patients and in experimentally established multidrug-resistant CCa cells. By using histoculture drug response assay, we further confirmed that clinical CCa samples with lower miR-34a expression appeared to be more resistant to chemotherapy. Functionally, ectopic expression of exogenous miR-34a resensitized multidrug-resistant HCT-8/OR cells to oxaliplatin treatment, whereas miR-34a inhibition augmented the oxaliplatin resistance in chemosensitive HCT-8 cells. Mechanistically, miR-34a positively regulated the mRNA stability of the ornithine decarboxylase antizyme 2 (OAZ2) by directly targeting its three prime untranslated region (3′UTR). Consequently, suppression of the expression of miR-34a/OAZ2 signaling by chemotherapeutic agents significantly enhanced the activation of MDR-associated ATP-binding cassette (ABC) transporters and antiapoptosis pathways, thus leading to MDR development in CCa cells. Collectively, our combined analysis reveals a critical role of miR-34a/OAZ2 cascade in conferring a proper cellular response to CCa chemotherapy.

Regulation of Human γδ T Cells by BTN3A1 Protein Stability and ATP-Binding Cassette Transporters

Activation of human Vγ9/Vδ2 T cells by "phosphoantigens" (pAg), the microbial metabolite (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP) and the endogenous isoprenoid intermediate isopentenyl pyrophosphate, requires expression of butyrophilin BTN3A molecules by presenting cells. However, the precise mechanism of activation of Vγ9/Vδ2 T cells by BTN3A molecules remains elusive. It is not clear what conformation of the three BTN3A isoforms transmits activation signals nor how externally delivered pAg accesses the cytosolic B30.2 domain of BTN3A1. To approach these problems, we studied two HLA haplo-identical HeLa cell lines, termed HeLa-L and HeLa-M, which showed marked differences in pAg-dependent stimulation of Vγ9/Vδ2 T cells. Levels of IFN-γ secretion by Vγ9/Vδ2 T cells were profoundly increased by pAg loading, or by binding of the pan-BTN3A specific agonist antibody CD277 20.1, in HeLa-M compared to HeLa-L cells. IL-2 production from a murine hybridoma T cell line expressing human Vγ9/Vδ2 T cell receptor (TCR) transgenes confirmed that the differential responsiveness to HeLa-L and HeLa-M was TCR dependent. By tissue typing, both HeLa lines were shown to be genetically identical and full-length transcripts of the three BTN3A isoforms were detected in equal abundance with no sequence variation. Expression of BTN3A and interacting molecules, such as periplakin or RhoB, did not account for the functional variation between HeLa-L and HeLa-M cells. Instead, the data implicate a checkpoint controlling BTN3A1 stability and protein trafficking, acting at an early time point in its maturation. In addition, plasma membrane profiling was used to identify proteins upregulated in HMB-PP-treated HeLa-M. ABCG2, a member of the ATP-binding cassette (ABC) transporter family was the most significant candidate, which crucially showed reduced expression in HeLa-L. Expression of a subset of ABC transporters, including ABCA1 and ABCG1, correlated with efficiency of T cell activation by cytokine secretion, although direct evidence of a functional role was not obtained by knockdown experiments. Our findings indicate a link between members of the ABC protein superfamily and the BTN3A-dependent activation of γδ T cells by endogenous and exogenous pAg.

Expression of some ATP-binding cassette transporters in acute myeloid leukemia

Hematopoietic cells express ATP binding cassette (ABC) transporters in relation to different degrees of differentiation. One of the known multidrug resistance mechanisms in acute myeloid leukemia (AML) is the overexpression of efflux pumps belonging to the superfamily of ABC transporters such as ABCB1, ABCG2 and ABCC1. Although several studies were carried out to correlate ABC transporters expression with drug resistance, little is known about their role as markers of diagnosis and progression of the disease. For this purpose we investigated the expression, by real-time PCR, of some ABC genes in bone marrow samples of AML patients at diagnosis and after induction therapy. At diagnosis, ABCG2 was always down-regulated, while an up regulated trend for ABCC1 was observed. After therapy the examined genes showed a different expression trend and approached the values of healthy subjects suggesting that this event could be considered as a marker of AML regression. The expression levels of some ABC transporters such as ABCC6, seems to be related to gender, age and to the presence of FLT3/ITD gene mutation.

Transforming doxorubicin into a cancer stem cell killer via EpCAM aptamer-mediated delivery

Chemotherapy-resistant cancer stem cells (CSCs) are a major obstacle to the effective treatment of many forms of cancer. To overcome CSC chemo-resistance, we developed a novel system by conjugating a CSC-targeting EpCAM aptamer with doxorubicin (Apt-DOX) to eliminate CSCs. Incubation of Apt-DOX with colorectal cancer cells resulted in high concentration and prolonged retention of DOX in the nuclei. Treatment of tumour-bearing xenograft mice with Apt-DOX resulted in at least 3-fold more inhibition of tumour growth and longer survival as well as a 30-fold lower frequency of CSC and a prolonged longer tumourigenic latency compared with those receiving the same dose of free DOX. Our data demonstrate that a CSC-targeting aptamer is able to transform a conventional chemotherapeutic agent into a CSC-killer to overcome drug resistance in solid tumours.

Molecular iodine impairs chemoresistance mechanisms, enhances doxorubicin retention and induces downregulation of the CD44+/CD24+ and E-cadherin+/vimentin+ subpopulations in MCF-7 cells resistant to low doses of doxorubicin

One of the most dreaded clinical events for an oncology patient is resistance to treatment. Chemoresistance is a complex phenomenon based on alterations in apoptosis, the cell cycle and drug metabolism, and it correlates with the cancer stem cell phenotype and/or epithelial-mesenchymal transition. Molecular iodine (I2) exerts an antitumor effect on different types of iodine-capturing neoplasms by its oxidant/antioxidant properties and formation of iodolipids. In the present study, wild-type breast carcinoma cells (MCF-7/W) were treated chronically with 10 nM doxorubicin (DOX) to establish a low-dose DOX-resistant mammary cancer model (MCF-7/D). MCF-7/D cells were established after 30 days of treatment when the culture showed a proliferation rate similar to that of MCF-7/W. These DOX-resistant cells also showed increases in p21, Bcl-2 and MDR-1 expression. Supplementation with 200 µM I2 exerted similar effects in both cell lines: it decreased the proliferation rate by ~40%, and I2 co-administration with DOX significantly increased the inhibitory effect (to ~60%) and also increased apoptosis (BAX/Bcl-2 index), principally by inhibiting Bcl-2 expression. The inhibition by I2 + DOX was also accompanied by impaired MDR-1 induction as well as by a significant increase in PPARγ expression. All of these changes could be attributed to enhanced DOX retention and differential down-selection of CD44+/CD24+ and E-cadherin+/vimentin+ subpopulations. I2 + DOX-selected cells showed a weak induction of xenografts in Foxn1nu/nu mice, indicating that the iodine supplements reversed the tumorogenic capacity of the MCF-7/D cells. In conclusion, I2 is able to reduce the drug resistance and invasive capacity of mammary cancer cells exposed to DOX and represents an anti-chemoresistance agent with clinical potential.

Effect of abemaciclib (LY2835219) on enhancement of chemotherapeutic agents in ABCB1 and ABCG2 overexpressing cells in vitro and in vivo

Multidrug resistance (MDR) is the major obstacle of the success in cancer chemotherapy. The overexpression of ATP-binding cassette (ABC) transporters, particularly ABCB1 and ABCG2, play a significant role in mediating MDR by pumping anticancer drugs out of cancer cells. Abemaciclib (LY2835219) is an orally bioavailable CDK4/6 inhibitor under phase III clinical trials. Here, we found that LY2835219 remarkably enhanced the efficacy of chemotherapeutic drugs in ABCB1 or ABCG2 over-expressing cancer cells in vitro and in vivo. Furthermore, LY2835219 significantly increased the intracellular accumulation of doxorubicin (DOX) and rhodamine 123 (Rho 123) by inhibiting ABCB1 or ABCG2-mediated drug efflux in the transporters-overexpressing cells. Mechanistically, LY2835219 is likely a competitive inhibitor of ABCB1 and ABCG2 for its competition with [125I]-iodoarylazidoprazosin for photo affinity labeling of the transporters. On the other hand, at the transporters-inhibiting concentrations, LY2835219 did not alter the expression level of ABCB1 and ABCG2, and the phosphorylation status of retinoblastoma (Rb) pathway in both parental and their resistant cells. In conclusion, these findings revealed a novel role of LY2835219 in reversing ABCB1 or ABCG2-mediated MDR, which may be benefit to the patients with MDR cancer for combinational therapy.

Tackling breast cancer chemoresistance with nano-formulated siRNA

Breast cancer is the leading cancer diagnosed in women and the second leading cause of cancer-related deaths in women. Current limitations to standard chemotherapy in the clinic are extensively researched, including problems arising from repeated treatments with the same drugs. The phenomenon that cancer cells become resistant toward certain chemo drugs is called chemotherapy resistance. In this review, we are focusing on nanoformulation of siRNA for the fight against breast cancer chemoresistance.

ATP-binding cassette transmembrane transporters and their epigenetic control in cancer: an overview

INTRODUCTION

Members of the ATP-binding cassette (ABC) transmembrane transporters control the passage of several substrates across cell membranes, including drugs. This means that ABC transporters may exert a significant influence on the kinetics and dynamics of pharmacological agents, being responsible for the occurrence of multidrug-resistant (MDR) phenotype. Pharmacogenetic analyses have shed light on gene expression and polymorphisms as possible markers predictive of transporter activity. However, a non-negligible part of the variability in drug pharmacokinetics and pharmacodynamics still remains. Further research has demonstrated that different epigenetic mechanisms exert a coordinated control over ABC genes, and on the corresponding MDR phenotype. Areas covered: DNA methylation and histone modifications (namely acetylation, methylation, phosphorylation, etc.) significantly impact gene expression, as well as noncoding RNA molecules that are involved in the post-transcriptional control of the ABC transporters ABCB1, ABCC1 and ABCG2. We describe the epigenetic mechanisms of gene expression control for ABC transporters and their relevant association with the MDR phenotype in human cancer. Expert opinion: The clinical meaning of those observations is discussed in the review, highlighting the importance of the epigenetic control of the ABC transporters for the clinical therapeutic outcomes that despite their effects and applications, requires further investigation.

A Salmonella nanoparticle mimic overcomes multidrug resistance in tumours

Salmonella enterica serotype Typhimurium is a food-borne pathogen that also selectively grows in tumours and functionally decreases P-glycoprotein (P-gp), a multidrug resistance transporter. Here we report that the Salmonella type III secretion effector, SipA, is responsible for P-gp modulation through a pathway involving caspase-3. Mimicking the ability of Salmonella to reverse multidrug resistance, we constructed a gold nanoparticle system packaged with a SipA corona, and found this bacterial mimic not only accumulates in tumours but also reduces P-gp at a SipA dose significantly lower than free SipA. Moreover, the Salmonella nanoparticle mimic suppresses tumour growth with a concomitant reduction in P-gp when used with an existing chemotherapeutic drug (that is, doxorubicin). On the basis of our finding that the SipA Salmonella effector is fundamental for functionally decreasing P-gp, we engineered a nanoparticle mimic that both overcomes multidrug resistance in cancer cells and increases tumour sensitivity to conventional chemotherapeutics.

Role of the Drug Transporter ABCC3 in Breast Cancer Chemoresistance

Increased expression of ABC-family of transporters is associated with chemotherapy failure. Although the drug transporters ABCG2, ABCB1 and ABCC1 have been majorly implicated in cancer drug resistance, recent studies have associated ABCC3 with multi drug resistance and poor clinical response. In this study, we have examined the expression of ABCC3 in breast cancers and studied its role in drug resistance and stemness of breast cancer cells in comparison with the more studied ABCC1. We observed that similar to ABCC1, the transcripts levels of ABCC3 was significantly high in breast cancers compared to adjacent normal tissue. Importantly, expression of both transporters was further increased in chemotherapy treated patient samples. Consistent with this, we observed that treatment of breast cancer cell lines with anti-cancer agents increased their mRNA levels of both ABCC1 and ABCC3. Further, similar to knockdown of ABCC1, knockdown of ABCC3 also significantly increased the retention of chemotherapeutic drugs in breast cancer cells and rendered them more chemo-sensitive. Interestingly, ABCC1 and ABCC3 knockdown cells also showed reduction in the expression of stemness genes, while ABCC3 knockdown additionally led to a reduction in the CD44high/CD24low breast cancer stem-like subpopulation. Consistent with this, their ability to form primary tumours was compromised. Importantly, down-modulation of ABCC3 rendered these cells increasingly susceptible to doxorubicin in xenograft mice models in vivo. Thus, our study highlights the importance of ABCC3 transporters in drug resistance to chemotherapy in the context of breast cancer. Further, these results suggest that combinatorial inhibition of these transporters together with standard chemotherapy can reduce therapy-induced resistance in breast cancer.

Imatinib Inhibits the Renewal and Tumorigenicity of CT-26 Colon Cancer Cells after Cytoreductive Treatment with Doxorubicin

Conventional anti-cancer drugs preferentially eliminate differentiated cancer cells but those cells that are spared (i.e. cancer stem cells: CSC), initiate recurrence. We tested whether drugs that target receptor tyrosine kinases (RTKs) involved in developmental signaling cascades and activated in CSC, could be used to silence and/or to eliminate colorectal cancer cells refractory to conventional treatment with cytoreductive drugs. A sequential treatment model was thereby developed with doxorubicin (DOX) and imatinib. CT-26 mouse colon carcinoma cells were pre-treated with DOX to select DOX-refractory cells with CSC properties, which were then subsequently treated with RTK inhibitor imatinib, where their regrowth was found to be inhibited. Under both normoxic and hypoxic conditions, imatinib potently inhibited clonogenicity of DOX-refractory CT-26 cells. Treatment with DOX did not eliminate tumorigenic CT-26 cells, since CT-26 cells pre-exposed to DOX in vitro, when inoculated subcutaneously, induced tumors in 90 % of mice, as opposed to a 100 % rate in the case of chemonaive CT-26 cells. In mice inoculated with chemonaive CT-26 cells, tumor formation was not prevented by imatinib. However, imatinib prevented tumor formation in 50 % of mice inoculated with CT-26 cells pre-exposed to DOX in vitro, with the remaining 50 % mice showing delayed tumor formation. These results suggest that the sequential use of the drug imatinib, as a drug targeting cancer cells expressing stem cell features after conventional cytoreductive treatment, is a promising future strategy for preventing tumor recurrence.

Immunotherapeutic approaches in prostate cancer: combinations and clinical integration

Despite multiple immunologic approaches with peptide, protein, and DNA vaccines, no single therapy has induced complete remission or maintained durability of response in patients with castration-resistant prostate cancer (CRPC). Historically, immunotherapy has had limited effect on solid tumors with the exception of melanoma and renal cell carcinomas, which have been deemed as immunologic cancers given their potential for remissions either spontaneously or after removal of the primary lesion. There is considerable excitement about using an immunotherapy in combination with biologic agents such as checkpoint inhibitors, cytokines, other vaccines, or chemotherapy. Sipuleucel-T represents one of several novel immunologic therapeutic approaches to treat prostate cancer in addition to other solid tumors. It is the first in its class of autologous cellular therapies to demonstrate safety and an overall survival benefit in patients with asymptomatic or minimally symptomatic CRPC and represents a unique treatment method that may be further enhanced with other agents. Although sipuleucel-T can be used as a foundation on which to build and enhance future immunologic clinical trials, other exciting strategies are in development that may be easily integrated into the algorithm of current care.

Phenotypic drug profiling in droplet microfluidics for better targeting of drug-resistant tumors

Acquired drug resistance is a key factor in the failure of chemotherapy. Due to intratumoral heterogeneity, cancer cells depict variations in intracellular drug uptake and efflux at the single cell level, which may not be detectable in bulk assays. In this study we present a droplet microfluidics-based approach to assess the dynamics of drug uptake, efflux and cytotoxicity in drug-sensitive and drug-resistant breast cancer cells. An integrated droplet generation and docking microarray was utilized to encapsulate single cells as well as homotypic cell aggregates. Drug-sensitive cells showed greater death in the presence or absence of Doxorubicin (Dox) compared to the drug-resistant cells. We observed heterogeneous Dox uptake in individual drug-sensitive cells while the drug-resistant cells showed uniformly low uptake and retention. Dox-resistant cells were classified into distinct subsets based on their efflux properties. Cells that showed longer retention of extracellular reagents also demonstrated maximal death. We further observed homotypic fusion of both cell types in droplets, which resulted in increased cell survival in the presence of high doses of Dox. Our results establish the applicability of this microfluidic platform for quantitative drug screening in single cells and multicellular interactions.

Ecdysteroids sensitize MDR and non-MDR cancer cell lines to doxorubicin, paclitaxel, and vincristine but tend to protect them from cisplatin

Ecdysteroids, analogs of the insect molting hormone, are known for their various mild, nonhormonal bioactivities in mammals. Previously, we reported that less-polar ecdysteroids can modulate the doxorubicin resistance of a multidrug resistant (MDR) mouse lymphoma cell line expressing the human ABCB1 transporter. Here, we describe the ability of 20-hydroxyecdysone (1) and its mono- (2) and diacetonide (3) derivatives to sensitize various MDR and non-MDR cancer cell lines towards doxorubicin, paclitaxel, vincristine, or cisplatin. Drug IC50 values with or without ecdysteroid were determined by MTT assay. Compound 3 significantly sensitized all cell lines to each chemotherapeutic except for cisplatin, whose activity was decreased. In order to overcome solubility and stability issues for the future in vivo administration of compound 3, liposomal formulations were developed. By means of their combination index values obtained via checkerboard microplate method, a formulation showed superior activity to that of compound 3 alone. Because ecdysteroids act also on non-ABCB1 expressing (sensitive) cell lines, our results demonstrate that they do not or not exclusively exert their adjuvant anticancer activity as ABCB1 inhibitors, but other mechanisms must be involved, and they opened the way towards their in vivo bioactivity testing against various cancer xenografts.

Epigenetics and miRNA as predictive markers and targets for lung cancer chemotherapy

Lung cancer cells show inherent and acquired resistance to chemotherapy. The lack of good predictive markers/novel targets and the incomplete understanding of the mechanisms of resistance limit the success of lung cancer response to chemotherapy. In the present study, we used an isogenic pair of lung adenocarcinoma cell lines; A549 (wild-type) and A549DOX11 (doxorubicin resistant) to study the role of epigenetics and miRNA in resistance/response of non-small cell lung cancer (NSCLC) cells to doxorubicin. Our results demonstrate differential expression of epigenetic markers whereby the level of HDACs 1, 2, 3 and4, DNA methyltransferase, acetylated H2B and acetylated H3 were lower in A549DOX11 compared to A549 cells. Fourteen miRNAs were dys-regulated in A549DOX11 cells compared to A549 cells, of these 14 miRNAs, 4 (has-mir-1973, 494, 4286 and 29b-3p) have shown 2.99 - 4.44 fold increase in their expression. This was associated with reduced apoptosis and higher resistance of A549DOX11cells to doxorubicin and etoposide. Sequential treatment with the epigenetic modifiers trichostatin A or 5-aza-2'-deoxycytidine followed by doxorubicin resulted in: (i) enhanced sensitivity of both cell lines to doxorubicin especially at low concentrations, (ii) enhanced doxorubicin-induced DNA damage in both cell lines, (iii) dysregulation of some miRNAs in A549 cells. In conclusion, A549DOX11 cells resistant to DNA damaging drugs have epigenetic profile and miRNA expression different from the sensitive cells. Moreover, epigenetic modifiers may reverse the resistance of certain NSCLC cells to DNA damaging agents by enhancing induction of DNA damage. This may open the door for using epigenetic profile/miRNA expression of some cancer cells as resistance markers/targets to improve response of resistant cells to doxorubicin and for the use of combination doxorubicin/epigenetic modifiers to reduce doxorubicin toxicity.