Structure activity relationship for anticancer activities of spirooxindole derivatives: A comprehensive review

Cancer remains one of the leading causes of mortality worldwide, necessitating the continuous search for novel therapeutic agents. Spirooxindole derivatives have recently emerged as a class of compounds with significant potential for cancer treatment owing to their diverse pharmacological activities and unique structural features. The structural diversity of spirooxindole derivatives enables a wide range of modifications, facilitating optimization of their pharmacokinetic and pharmacodynamic properties. Moreover, their ability to interact with multiple molecular targets involved in cancer progression, including kinases, receptors, and enzymes, makes them attractive candidates for multi-targeted therapy. In preclinical studies, numerous spirooxindole derivatives have demonstrated promising antiproliferative activity against various cancer cell lines, including breast, lung, colon, and prostate cancers. Mechanistic investigations have revealed their ability to induce cell cycle arrest and apoptosis and inhibit angiogenesis and metastasis, underscoring their potential as effective anticancer agents. However, challenges such as off-target effects, drug resistance, and limited bioavailability need to be addressed to maximize the therapeutic potential of these compounds. Continued research efforts to elucidate their molecular mechanisms, optimize their pharmacological properties, and conduct rigorous clinical evaluations are warranted to harness their full therapeutic benefits for cancer treatment. This review provides a comprehensive overview of recent advancements in developing spirooxindole derivatives as anticancer agents with structure-activity relationships.

Impact of ALDH1A1 and NQO1 gene polymorphisms on the response and toxicity of chemotherapy in Bangladeshi breast cancer patients

PURPOSE

Cyclophosphamide, Epirubicin/Doxorubicin, 5-fluorouracil (CEF or CAF) chemotherapy has long been a standard first-line treatment for breast cancer. The genetic variations of enzymes that are responsible for the metabolism of these drugs have been linked to altered treatment response and toxicity. Two drug-metabolizing enzymes ALDH1A1 and NQO1 are critically involved in the pathways of CEF/CAF metabolism. This study aimed to evaluate the effect of ALDH1A1 (rs13959) and NQO1 (rs1800566) polymorphisms on treatment response and toxicities caused by adjuvant (ACT) and neoadjuvant chemotherapy (NACT) where CEF/CAF combination was used to treat Bangladeshi breast cancer patients.

METHODS

A total of 330 patients were recruited from various hospitals, with 150 receiving neoadjuvant chemotherapy and 180 receiving adjuvant chemotherapy. To extract genomic DNA, a non-enzymatic simple salting out approach was adopted. The polymerase chain reaction-restriction fragment length polymorphism method was used to detect genetic polymorphisms. Unconditional logistic regression was used to derive odds ratios (ORs) with 95% confidence intervals (CIs) to study the association between genetic polymorphisms and clinical outcome and toxicity.

RESULTS

A statistically significant association was observed between ALDH1A1 (rs13959) polymorphism and treatment response (TT vs. CC: aOR = 6.40, p = 0.007; recessive model: aOR = 6.38, p = 0.002; allele model: p = 0.032). Patients with the genotypes TT and CT + TT of the NQO1 (rs1800566) polymorphism had a significantly higher risk of toxicities such as anemia (aOR = 0.34, p = 0.006 and aOR = 0.58, p = 0.021), neutropenia (aOR = 0.42, p = 0.044 and aOR = 0.57, p = 0.027), leukopenia (aOR = 0.33, p = 0.010 and aOR = 0.46, p = 0.005), and gastrointestinal toxicity (aOR = 0.30, p = 0.02 and aOR = 0.38, p = 0.006) when compared to the wild CC genotype, while patients with the genotype CT had a significant association with gastrointestinal toxicity (aOR = 0.42, p = 0.02) and leukopenia (aOR = 0.52, p = 0.010). The TT and CT + TT genotypes of rs13959 had a significantly higher risk of anemia (aOR = 2.00, p = 0.037 and aOR = 1.68, p = 0.029). There was no significant association between rs1800566 polymorphism and treatment response.

CONCLUSION

Polymorphisms in ALDH1A1 (rs13959) and NQO1 (rs1800566) may be useful in predicting the probability of treatment response and adverse effects from CEF or CAF-based chemotherapy in breast cancer patients.

In silico drug repurposing and lipid bilayer molecular dynamics puzzled out potential breast cancer resistance protein (BCRP/ABCG2) inhibitors

Multidrug resistance (MDR) is a fundamental reason for the fiasco of carcinoma chemotherapy. A wide variety of anticarcinoma drugs are expelled from neoplasm cells through the ATP-binding cassette (ABC) transporter superfamily, rendering the neoplasm cells resistant to treatment. The ATP-binding cassette transporter G2 (ABCG2, gene symbol BCRP) is an ABC efflux transporter that plays a key function in MDR to antineoplastic therapies. For these reasons, the identification of medicaments as BCRP inhibitors could assist in discovering better curative approaches for breast cancer therapy. Because of the deficiency of prospective BCRP inhibitors, the SuperDRUG2 database was virtually screened for inhibitor activity towards the BCRP transporter using molecular docking computations. The most potent drug candidates were then characterized utilizing molecular dynamics (MD) simulations. Furthermore, molecular mechanics-generalized Born surface area (MM-GBSA) binding affinities of the most potent drug candidates were estimated. Based on the MM-GBSA binding affinities throughout 150 ns MD simulations, three drugs-namely zotarolimus (SD002595), temsirolimus (SD003393), and glecaprevir (SD006009)-revealed greater binding affinities towards BCRP transporter compared to the co-crystallized BWQ ligand with ΔGbinding values of -86.6 ± 5.6, -79.5 ± 8.0, -75.8 ± 4.6 and -59.5 ± 4.1 kcal/mol, respectively. The steadiness of these promising drugs bound with BCRP transporter was examined utilizing their structural and energetical analyses throughout a 150 ns MD simulation. To imitate the physiological environment, 150 ns MD simulations for the identified drugs bound with BCRP transporter were conducted in the 1-palmitoyl-2-oleoyl-phosphatidylcholine lipid bilayer. These findings identify zotarolimus, temsirolimus and glecaprevir as auspicious anti-MDR drug leads that warrant further experimental assays.Communicated by Ramaswamy H. Sarma.

Targeting Cancer Stem Cells as the Key Driver of Carcinogenesis and Therapeutic Resistance

The emerging concept of cancer stem cells (CSCs) as the key driver behind carcinogenesis, progression, and diversity has displaced the prior model of a tumor composed of cells with similar subsequently acquired mutations and an equivalent capacity for renewal, invasion, and metastasis. This significant change has shifted the research focus toward targeting CSCs to eradicate cancer. CSCs may be characterized using cell surface markers. They are defined by their capacity to self-renew and differentiate, resist conventional therapies, and generate new tumors following repeated transplantation in xenografted mice. CSCs' functional capabilities are governed by various intracellular and extracellular variables such as pluripotency-related transcription factors, internal signaling pathways, and external stimuli. Numerous natural compounds and synthetic chemicals have been investigated for their ability to disrupt these regulatory components and inhibit stemness and terminal differentiation in CSCs, hence achieving clinical implications. However, no cancer treatment focuses on the biological consequences of these drugs on CSCs, and their functions have been established. This article provides a biomedical discussion of cancer at the time along with an overview of CSCs and their origin, features, characterization, isolation techniques, signaling pathways, and novel targeted therapeutic approaches. Additionally, we highlighted the factors endorsed as controlling or helping to promote stemness in CSCs. Our objective was to encourage future studies on these prospective treatments to develop a framework for their application as single or combined therapeutics to eradicate various forms of cancer.

Naturally occurring plant-based anticancerous candidates as prospective ABCG2 inhibitors: an in silico drug discovery study

ATP-binding cassette transporter G2 (ABCG2) is an efflux transporter related to the clinical multidrug resistance (MDR) phenomenon. Identifying ABCG2 inhibitors could help discover extraordinary curative strategies for carcinoma remediation. Hitherto, there is no medication drug inhibiting ABCG2 transporter, notwithstanding that a considerable number of drugs have been submitted to clinical-trial and investigational phases. In the search for unprecedented chemical compounds that could inhibit the ABCG2 transporter, an in silico screening was conducted on the Naturally Occurring Plant-based Anticancer Compound-Activity-Target (NPACT) database containing 1574 compounds. Inhibitor-ABCG2 binding affinities were estimated based on molecular docking and molecular minimization (MM) calculations and compared to a co-crystallized inhibitor (BWQ) acting as a reference inhibitor. Molecular dynamics (MD) simulations pursued by molecular mechanics-generalized Born surface area (MM-GBSA) binding energy estimations were further executed for compounds with MM-GBSA//MM binding energies lower than BWQ (calc. - 60.5 kcal/mol). NPACT00968 and NPACT01545 demonstrated auspicious inhibitory activities according to binding affinities (ΔGbinding) over the 100 ns MD simulations that were nearly one and a half folds compared to BWQ (- 100.4, - 94.7, and - 62.9 kcal/mol, respectively). Throughout the 100 ns MD simulations, structural and energetical analyses unveiled outstanding stability of the ABCG2 transporter when bound with NPACT00968 and NPACT01545. In silico calculations hold a promise for those two inhibitors as drug candidates of ABCG2 transporter and emphasize that further in vitro and in vivo experiments are guaranteed.

Impact of DNA methylation on ADME gene expression, drug disposition and efficacy

Interindividual differences in drug response have always existed in clinical treatment. Genes involved in drug absorption, distribution, metabolism, and excretion (ADME) play an important role in the process of pharmacokinetics. The effects of genetic polymorphism and nuclear receptors on the expression of drug metabolism enzymes and transporters can only explain some individual differences in clinical treatment. Several key ADME genes have been demonstrated to be regulated by epigenetic mechanisms that can potentially affect interindividual variability in medical treatment. Emerging studies have focused on the importance of DNA methylation for ADME gene expression and for drug response. Among them, the most studied is anti-tumor drugs, and followed by anti-tuberculous and anti-platelet drugs. Therefore, we provide an epigenetics perspective on variability in drug response. The review summarizes the correlation between ADME gene expression and DNA methylation, including the exact methylation locations, and focuses on the corresponding drug disposition and effects to illuminate interindividual differences in clinical medication.

Controlled release of 5-fluorouracil to melanoma cells using a hydrogel/micelle composites based on deoxycholic acid and carboxymethyl chitosan

5-Fluorouracil (5-FU) is an antimetabolite drug widely used for the treatment of skin cancer. Despite its proven efficacy in treating malignancies, its systemic administration is limited due to severe side effects. To address this issue, topical delivery of 5-FU has been proposed as an alternative approach for the treatment of skin cancer, however, the poor permeability of 5-FU through the skin is still a challenge. Here, we introduced a pH-responsive micellar hydrogel system based on deoxycholic acid micelle (DCA Mic) and carboxymethyl chitosan hydrogel (CMC Hyd) to enhance 5-FU efficacy against skin cancer and reduce its systemic side effects by improving its delivery into the skin. The properties of the Mic/Hyd system were determined by Fourier-transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), zeta sizer, atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Drug release studies showed pH-dependent properties of the Hyd. The final formulation was demonstrated to have enhanced anticancer activity than 5-FU against the growth of melanoma cells. The 5-FU@Mic-Hyd could be a promising delivery platform with enhanced efficacy in the management of skin cancer without systemic toxicity.

Identification of Atypical Circulating Tumor Cells with Prognostic Value in Metastatic Breast Cancer Patients

Simple Summary

In this study we have isolated and analyzed atypical cells found in the blood of metastatic breast cancer patients using a micro-filtration technic. This technic, being very easy to implement, was also extremely useful for studying circulating tumors cells’ (CTCs) heterogeneity in cancer patients. We highlighted three subsets of CTCs, with different independent unfavorable prognostic values for progression-free and overall survival. We demonstrated that these cells can further be analyzed by immunofluorescence to narrow their molecular profiles and identify specific characteristics. Moreover, we identified a subset of CTCs, for which positivity might be a useful stratification tool to select patients more susceptible to benefit from early clinical trials testing novel therapeutics, which frequently enroll late-stage, already heavily pre-treated and thus poor-responder patients.

Abstract

Circulating tumor cells have a strong potential as a quasi-non-invasive tool for setting up a precision medicine strategy for cancer patients. Using a second-generation “filtration-based” technology to isolate CTCs, the Screencell™ technology (Sarcelles, France), we performed a large and simultaneous analysis of all atypical circulating tumor cells (aCTCs) isolated from the blood of metastatic breast cancer (mBC) patients. We correlated their presence with clinicopathological and survival data. We included 91 mBC patients from the PERMED-01 study. The median number of aCTCs was 8.3 per mL of blood. Three subsets of aCTCs, absent from controls, were observed in patients: single (s-aCTCs), circulating tumor micro-emboli (CTM), and giant-aCTCs (g-aCTCs). The presence of g-aCTCs was associated with shorter progression free survival and overall survival. This study highlights the heterogeneity of aCTCs in mBC patients both at the cytomorphological and molecular levels. In addition, it suggests the usefulness of the g-aCTC subset as a prognostic factor and a potential stratification tool to treat late-stage mBC patients and improve their chances of benefiting from early clinical trials.

Gambogenic Acid Inhibits Basal Autophagy of Drug-Resistant Hepatoma Cells and Improves Its Sensitivity to Adriamycin

Gambogenic acid (GNA) is extracted from plant Gamboge, has a wide range of anti-tumor effects. In this paper, we study the inhibitory effect of GNA on the BEL-7402/ADM of hepatoma resistant cell lines and further study the mechanism of action. Cell viability test represented that GNA could improve the sensitivity of hepatoma drug-resistant cell line BEL-7402/ADM to Adriamycin (ADM), and further study by 4',6-diamidino-2-phenylindole (DAPI) staining and flow cytometry found that GNA could improve the effect of ADM on promoting apoptosis in BEL-7402/ADM cells, and the activation of apoptosis-related protein was significantly increased, and the ratio of Bax to Bcl-2 was significantly increased. Monodansylcadaverine staining and transmission electron microscopy showed that the basal autophagy level of BEL-7402/ADM cells was higher than that of BEL-7402 cells. Further detection of protein expression found that the intracellular LC3-II to LC3-I ratio and Beclin 1 protein expression increased in the combination of GNA and ADM, but the protein level of p62 increased significantly. GNA inhibit protective autophagy in BEL-7402/ADM cells and promote the role of ADM in inducing apoptosis, thereby increasing ADM sensitivity to BEL-7402/ADM cells, and the effect of GNA inhibition of autophagy may be achieved by inhibiting the degradation of autophagosomes.

Evaluation of diffusion coefficient of P-glycoprotein molecules labeled with green fluorescent protein in living cell membrane

The movement of individual molecules inside living cells has recently been resolved by single particles tracking (SPT) method which is a powerful tool for probing the organization and dynamics of the plasma membrane constituents. Effective treatment of metastatic cancers requires the toxic chemotherapy, however this therapy leads to the multidrug resistance phenomenon of the cancer cells, in which the cancer cells resist simultaneously to different drugs with different targets and chemical structures. P-glycoprotein molecules which are responsible for multidrug resistance of many cancer cells have been studied by cancer biologists during past haft of century. Recently, advances in laser and detector technologies have enabled single fluorophores to be visualized in aqueous solution. The development of the total internal reflection fluorescent microscope (TIRFM) provided means to monitor dynamic molecular localization in living cells. In this paper, P-glycoproteins (PGP) were labeled with green fluorescent protein (GFP) in living cell membrane of Madin-Darby canine kidney (MDCK) and the TIRFM method was used to characterize the dynamics of individual protein molecules on the surface of living cells. An evanescent field was produced by a totally internally reflected and a laser beam was illuminated the glass-water interface. GFP-PGP proteins that entered the evanescent field appeared as individual spots of light which were slighter than background fluorescence. We obtained high-resolution images and diffusion maps of membrane proteins on cell surface and showed the local diffusion properties of specific proteins on single cells. We also determined the diffusion coefficient, the mean square displacement and the average velocity of the tracked particles, as well as the heterogeneity of the cell environment. This study enabled us to understand single-molecule features in living cell and measure the diffusion kinetics of membrane-bound molecules.

LncRNA as a multifunctional regulator in cancer multi-drug resistance

BACKGROUND

Malignant tumors have become the most dangerous disease in recent years. Chemotherapy is the most effective treatment for this disease; however, the problem of drug resistance has become even more common, which leads to the poor prognosis of patients suffering from cancers. Thus, necessary measures should be taken to address these problems at the earliest. Many studies have demonstrated that drug resistance is closely related to the abnormal expressions of long non-coding RNAs (lncRNAs).

METHODS AND RESULTS

This review aimed to summarize the molecular mechanisms underlying the association of lncRNAs and the development of drug resistance and to find potential strategies for the clinical diagnosis and treatment of cancer drug resistance. Studies showed that lncRNAs can regulate the expression of genes through chromatin remodeling, transcriptional regulation, and post-transcriptional processing. Furthermore, lncRNAs have been reported to be closely related to the occurrence of malignant tumors. In summary, lncRNAs have gained attention in related fields during recent years. According to previous studies, lncRNAs have a vital role in several different types of cancers owing to their multiple mechanisms of action. Different mechanisms have different functions that could result in different consequences in the same disease.

CONCLUSIONS

LncRNAs closely participated in cancer drug resistance by regulating miRNA, signaling pathways, proteins, cancer stem cells, pro- and ant-apoptosis, and autophagy. lncRNAs can be used as biomarkers of the possible treatment target in chemotherapy, which could provide solutions to the problem of drug resistance in chemotherapy in the future.

Identification of a lathyrane-type diterpenoid EM-E-11-4 as a novel paclitaxel resistance reversing agent with multiple mechanisms of action

P-glycoprotein (P-gp) and βIII-tubulin overexpression-mediated drug resistance leads to clinical therapy failure for paclitaxel. However, the development of paclitaxel-resistance reversal agents has not had much success. In this study, EM-E-11-4, a lathyrane-type diterpenoid extracted from Euphorbia micractina, demonstrated good anti-MDR (multidrug resistance) activity in paclitaxel-resistant tumor cells overexpressing either P-gp or βIII-tubulin. EM-E-11-4 was able to recover the effects of paclitaxel in inducing arrest at G₂/M phase and apoptosis in both A549/Tax (P-gp overexpression) and Hela/βIII (βIII-tubulin overexpression) cells, respectively, at a non-cytotoxic dose. EM-E-11-4 could enable Flutax-1 and Rhodamine 123 be accumulated intracellularly at an accelerating rate in A549/Tax cells by inhibiting the activity of P-gp ATPase, rather than affecting the expression of P-gp. In addition, it also strengthened the effects of paclitaxel in promoting tubulin polymerization and the binding of paclitaxel to microtubules in vitro. It inhibited the expression of βIII-tubulin in Hela/βIII cells in a dose-dependent manner while not exerting influence on the other β-tubulin subtypes. As far as we know, this is the first study to report that a small molecule natural product could specifically inhibit the expression of βIII-tubulin. These results suggest EM-E-11-4 may serve as a promising MDR reversal agent, particularly for patients bearing tumors with high expression of P-gp and βIII-tubulin.

Enhancing Antitumor Efficacy of Nucleoside Analog 5-Fluorodeoxyuridine on HER2-Overexpressing Breast Cancer by Affibody-Engineered DNA Nanoparticle

BACKGROUND

Chemotherapy, as an adjuvant treatment strategy for HER2-positive breast cancer, can effectively improve clinical symptoms and overcome the drug resistance of therapeutic monoclonal antibodies. Nucleoside analogues are a class of traditional chemotherapeutic drugs that are widely applied in adjuvant therapy. However, there are many critical issues that limit their clinical efficiency, including poor selectivity and stability, severe side effects and suboptimal therapeutic efficacy. Hence, this work aims to develop a new DNA nanocarrier for targeted drug delivery to solve the above problems.

METHODS

Four 41-mer DNA strands were synthesized and 10 FUdR molecules were attached to 5' end of each DNA strand by DNA solid-phase synthesis. An affibody molecule was connected to the end of polymeric FUdR through a linker in one of the four strands. The affibody-FUdR-tetrahedral DNA nanostructures (affi-F/TDNs) were self-assembled through four DNA strands, in which one vertex was connected to an affibody at the end of a polymeric FUdR tail and three vertices were only polymeric FUdR tails. In vitro cellular uptake of affi-F/TDNs was examined visually with confocal fluorescence microscopy and flow cytometry, and the cytotoxicity of affi-F/TDNs against cancer cells was investigated with MTT assay. Cell apoptosis was detected by Annexin V-FITC/PI double staining method. Using NOD/SCID (Mus Musculus) mice model, the targeted killing efficacy of affi-F/TDNs was also evaluated.

RESULTS

The drug-loading of FUdR in affi-TDNs was 19.6% in mole ratio. The in vitro results showed that affi-F/TDNs had high selectivity and inhibition (81.2%) for breast cancer BT474 cells overexpressing HER2 and low toxicity in MCF-7 cells with low HER2 expression. During the in vivo application, affi-F/TDNs displayed good stability in the blood circulation, achieved specific accumulation in tumor region and the best antitumor efficacy (inhibition ratio of 58.1%), and showed excellent biocompatibility.

CONCLUSIONS

The affibody-DNA tetrahedrons, as a simple and effective active targeting delivery nanocarrier, provided a new avenue for the transport of nucleoside antitumor drugs.

Nanodelivery and anticancer effect of a limonoid, nimbolide, in breast and pancreatic cancer cells

Introduction

Nimbolide (Nim), a limonoid obtained from the neem tree, Azadirachta indica, has several pharmacological properties, including anticancer effects in different type of cancers. No drug-delivery system has been reported for enhancing the therapeutic application of this novel hydrophobic molecule.

Methods

In the present research, poly(lactic-co-glycolic acid) (PLGA) nanoparticles of Nim (Nim-nano) were formulated by nanoprecipitation, characterized for physicochemical properties, and screened for anticancer potential in breast (MCF-7 and MDA-MB-231) and pancreatic (AsPC-1) cancer cell lines.

Results

The Nim-nano had a particle size of 183.73±2.22 nm and 221.20±11.03 nm before and after lyophilization, respectively. Cryoprotectants (mannitol and sucrose) significantly inhibited growth in particle size due to lyophilization. The ζ-potential of the Nim-nano was −22.40±4.40 mV. Drug loading and encapsulation efficiency of Nim-nano were 5.25%±1.12% and 55.67%±12.42%, respectively. The Nim-nano exhibited sustained release of Nim for more than 6 days in PBS (pH 7.4) and showed two- to three-fold enhanced cytotoxicity in breast and pancreatic cancer cell lines compared with free Nim.

Conclusion

The Nim-nano formulation has great potential for treatment of cancers, such as pancreatic and breast cancer. Further, the PLGA-polymer surface can be modified by conjugation with polyethylene glycol, receptor-binding ligands (eg, folic acid), and other that which may lead to targeted delivery of Nim in the treatment of cancer.

Synthesis and Cytotoxicity of 7,9-O-Linked Macrocyclic C-Seco Taxoids

A series of novel 7,9-O-linked macrocyclic taxoids together with modification at the C2 position were synthesized, and their cytotoxicities against drug-sensitive and P-glycoprotein and βIII-tubulin overexpressed drug-resistant cancer cell lines were evaluated. It is demonstrated that C-seco taxoids conformationally constrained via carbonate containing-linked macrocyclization display increased cytotoxicity on drug-resistant tumors overexpressing both βIII and P-gp, among which compound 22b, bearing a 2-m-methoxybenzoyl group together with a five-atom linker, was identified as the most potent. Molecular modeling suggested the improved cytotoxicity of 22b results from enhanced favorable interactions with the T7 loop region of βIII.

A Novel Synthetic Dihydroindeno[1,2-b] Indole Derivative (LS-2-3j) Reverses ABCB1- and ABCG2-Mediated Multidrug Resistance in Cancer Cells

10-oxo-5-(3-(pyrrolidin-1-yl) propyl)-5,10-dihydroindeno [1,2-b] indol-9-yl propionate (LS-2-3j) is a new chemically synthesized indole compound and some related analogues are known to be inhibitors (such as alectinib and Ko143) of ATP-binding cassette (ABC) transporters, especially the ABC transporter subfamily B member 1 (ABCB1) and the ABC transporter subfamily G member 2 (ABCG2). This study aimed to evaluate the multidrug resistance (MDR) reversal effects and associated mechanisms of LS-2-3j in drug-resistant cancer cells. The inhibition of cell proliferation in tested agents was evaluated by the 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide (MTT) assay. Accumulation or efflux of chemotherapy drugs was analyzed by flow cytometry. The ATPase activity was measured using an ATPase activity assay kit. The mRNA transcripts and protein expression levels were detected by real-time PCR and Western blot, respectively. In this connection, LS-2-3j significantly enhanced the activity of chemotherapeutic drugs in MDR cells and could significantly increase the intracellular accumulation of doxorubicin (DOX) and mitoxantrone (MITX) by inhibiting the function of the efflux pumps in ABCB1- or ABCG2-overexpressing cells. Furthermore, reduced ATPase activity, mRNA transcription, and protein expression levels of ABCB1 and ABCG2 were observed in a concentration dependent manner in MDR cancer cells.

Expression of LRP Gene in Breast Cancer Patients Correlated with MRP1 as Two Independent Predictive Biomarkers in Breast Cancer

Background:

Breast cancer is the most common malignancy in women. Multidrug resistance (MDR) is still a great obstacle of breast cancer chemotherapy. We have previously shown that multidrug resistance-associated protein 1 (MRP1) is associated with response to neoadjuvant chemotherapy. The lung resistance-related protein (LRP) is identified as a prognostic marker and response to treatment factor which has been studied mainly in hematological malignancy and leukemia. In this study, we aimed to analyze LRP expression and possible correlation between the expression level of this gene with MRP1 as a candidate marker for chemotherapy resistance.

Materials and Methods:

We collected 54 breast tumors and adjacent normal tissues from Iranian breast cancer patients and Real time RT-PCR was employed to measure the gene expression level in our samples.

Results:

MRP1 and LRP expression level were significantly lower in tumor tissues of the patients responding to chemotherapy compared to non-responding patients. No relation between the expression level of either of these genes and clinicopathology markers was found.

Conclusion:

Our results suggest that LRP gene expression is correlated to MRP1 in human breast cancer cells and may affect the clinical response to treatment.

Aiming for the Insulin-like Growth Factor-1 system in breast cancer therapeutics

Despite the major discoveries occurred in oncology the recent years, breast malignancies remain one of the most common causes of cancer-related deaths for women in developed countries. Development of HER2-targeting drugs has been considered a breakthrough in anti-cancer approaches and alluded to the potential of targeting growth factors in breast cancer (BrCa) therapeutics. More than twenty-five years have passed since the Insulin-like Growth Factor-1 (IGF-1) system was initially recognized as a potential target candidate in BrCa therapy. To date, a growing body of studies have implicated the IGF-1 signaling with the BrCa biology. Despite the promising experimental evidence, the impression from clinical trials is rather disappointing. Several reasons may account for this and the last word regarding the efficacy of this system as a target candidate in BrCa therapeutics is probably not written yet. Herein, we provide the theoretical basis, as well as, a comprehensive overview of the current literature, regarding the different strategies targeting the various components of the IGF-1/IGF-1R axis in several pathophysiological aspects of BrCa, including the tumor micro-environment and cancer stemness. In addition, we review the rationale for targeting the IGF-1 system in the different BrCa molecular subtypes and in treatment resistant breast tumors with a focus on both the molecular mechanisms and on the clinical perspectives of such approaches in specific population subgroups. We also discuss the future challenges, as well as, the development of novel molecules and strategies targeting the system and suggest potential improvements in the field.

Augmenter of liver regeneration potentiates doxorubicin anticancer efficacy by reducing the expression of ABCB1 and ABCG2 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is highly chemoresistant and therefore challenges both physicians and patients. Augmenter of liver regeneration (ALR), previously also known as 'hepatic stimulator substance', is reported to inhibit the epithelial-mesenchymal transition (EMT) in HCC, one of the frequent events that occur in cancer metastasis, suggesting that ALR is involved in HCC. In this study, we report for the first time that the transfection of ALR enhances the antitumor effect of chemotherapy with doxorubicin, a typical anticancer drug, on HCC in vitro and in vivo. The efflux of doxorubicin from ALR-transfected HCC cells is efficiently suppressed. This implies the intracellular retention of doxorubicin in tumor cells, which is at least partly attributable to the effective inhibition of ABCB1 and ABCG2 transporter expression in ALR-expressing cells. The downregulation of ALR expression by short hairpin RNA diminishes the antitumor effect of ALR. We further demonstrate that ALR inhibits the AKT/Snail signaling pathway, resulting in the downregulation of ABCB1 and ABCG2 expression. In conclusion, our results suggest that ALR is a potential chemotherapeutic agent against HCC.

Bafetinib (INNO-406) reverses multidrug resistance by inhibiting the efflux function of ABCB1 and ABCG2 transporters

ATP-Binding Cassette transporters are involved in the efflux of xenobiotic compounds and are responsible for decreasing drug accumulation in multidrug resistant (MDR) cells. Discovered by structure-based virtual screening algorithms, bafetinib, a Bcr-Abl/Lyn tyrosine kinase inhibitor, was found to have inhibitory effects on both ABCB1- and ABCG2-mediated MDR in this in-vitro investigation. Bafetinib significantly sensitized ABCB1 and ABCG2 overexpressing MDR cells to their anticancer substrates and increased the intracellular accumulation of anticancer drugs, particularly doxorubicin and [³H]-paclitaxel in ABCB1 overexpressing cells; mitoxantrone and [³H]-mitoxantrone in ABCG2 overexpressing cells, respectively. Bafetinib stimulated ABCB1 ATPase activities while inhibited ABCG2 ATPase activities. There were no significant changes in the expression level or the subcellular distribution of ABCB1 and ABCG2 in the cells exposed to 3 μM of bafetinib. Overall, our study indicated that bafetinib reversed ABCB1- and ABCG2-mediated MDR by blocking the drug efflux function of these transporters. These findings might be useful in developing combination therapy for MDR cancer treatment.

Association between the concentration of imatinib in bone marrow mononuclear cells, mutation status of ABCB1 and therapeutic response in patients with chronic myelogenous leukemia

Low concentrations of imatinib (IM) in bone marrow cells have been linked with poor prognosis in patients with chronic myeloid leukemia (CML), which may be caused by the emergence of ATP-binding cassette transporter B1 (ABCB1) mutations. The aim of present study was to investigate how clinical outcomes vary among patients with different single nucleotide polymorphisms (SNPs) of ABCB1. A total of 48 adult patients with CML and higher than median ABCB1 mRNA levels were selected for testing of ABCB1 SNPs. In 28 of the 48 patients, the IM concentration and expression levels of human organic cation transporter 1 (hOCT1) and ABCB1 in bone marrow mononuclear cells (BMMCs) were also tested. Correlations between treatment outcomes and IM concentration or the SNP status of ABCB1 were analyzed. Patients were classified by therapeutic response as major molecular response (MMR) (n=11), complete cytogenetic response (CCyR) (n=19) and non-CCyR (n=18) groups. It was found that the concentration of IM in BMMCs of the CCyR group was significant higher than that of the resistant groups (P=0.013). In addition, the IM concentration was positively correlated with the expression of hOCT1 mRNA (R=0.456, P=0.033), but negatively correlated with the expression of ABCB1 mRNA (R=-0.491, P=0.015). Furthermore, the mRNA expression level of ABCB1 was not associated with therapeutic response, but SNPs of the ABCB1 gene were associated with the response to IM. In conclusion, the concentration of IM in BMMCs may be regulated by the ABCB1 gene, and SNPs of the ABCB1 gene predict the therapeutic response to IM in patients with CML.

Co-delivery of Se nanoparticles and pooled SiRNAs for overcoming drug resistance mediated by P-glycoprotein and class III β-tubulin in drug-resistant breast cancers

Drug resistance mediated by P-glycoprotein (P-gp) and class III β-tubulin (β-tubulin III) is a major barrier in microtubule-targeting cancer chemotherapy. In this study, layered double hydroxide nanoparticles (LDHs) were employed to simultaneously deliver selenium (Se) and pooled small interfering RNAs (siRNAs) to achieve therapeutic efficacy. LDH-supported Se nanoparticles (Se@LDH) were compacted with siRNAs (anti-P-gp and anti-β-tubulin III) via electrostatic interactions, which could protect siRNA from degradation. Se@LDH showed excellent abilities to deliver siRNA into cells, including enhancing siRNA internalization, and promoting siRNA escape from endosomes. siRNA transfection experiments further confirmed a higher gene silencing efficiency of Se@LDH than LDH. Interestingly, we found Se@LDH may be a microtubule (MT) stabilizing agent which could inhibit cell proliferation by blocking cell cycle at G2/M phase, disrupting normal mitotic spindle formation and inducing cell apoptosis. When complexed with different specific siRNAs, Se@LDH/siRNA nanoparticles, especially the Se@LDH-pooled siRNAs, exhibit an efficient gene-silencing effect that significantly downregulate the expression of P-gp and β-tubulin III. Moreover, Se@LDH-pooled siRNAs could induce cell apoptosis, change cell morphology and increase cellular ROS levels through change the expression of Bcl-2/Bax, activation of caspase-3, PI3K/AKT/mTOR and MAPK/ERK pathways. These results suggested that co-delivery of Se and pooled siRNAs may be a promising strategy for overcoming the drug resistance mediated by P-gp and β-tubulin III in drug-resistant breast cancers.

Survivin family proteins as novel molecular determinants of doxorubicin resistance in organotypic human breast tumors

Introduction

The molecular determinants of breast cancer resistance to first-line anthracycline-containing chemotherapy are unknown.

Methods

We examined the response to doxorubicin of organotypic cultures of primary human breast tumors ex vivo with respect to cell proliferation, DNA damage and modulation of apoptosis. Samples were analyzed for genome-wide modulation of cell death pathways, differential activation of p53, and the role of survivin family molecules in drug resistance. Rational drug combination regimens were explored by high-throughput screening, and validated in model breast cancer cell types.

Results

Doxorubicin treatment segregated organotypic human breast tumors into distinct Responder or Non Responder groups, characterized by differential proliferative index, stabilization of p53, and induction of apoptosis. Conversely, tumor histotype, hormone receptor or human epidermal growth factor receptor-2 (HER2) status did not influence chemotherapy sensitivity. Global analysis of cell death pathways identified survivin and its alternatively spliced form, survivin-ΔEx3 as uniquely overexpressed in Non Responder breast tumors. Forced expression of survivin-ΔEx3 preserved cell viability and prevented doxorubicin-induced apoptosis in breast cancer cell types. High-throughput pharmacologic targeting of survivin family proteins with a small-molecule survivin suppressant currently in the clinic (YM155) selectively potentiated the effect of doxorubicin, but not other chemotherapeutics in breast cancer cell types, and induced tumor cell apoptosis.

Conclusions

Survivin family proteins are novel effectors of doxorubicin resistance in chemotherapy-naive breast cancer. The incorporation of survivin antagonist(s) in anthracycline-containing regimens may have improved clinical activity in these patients.

Interaction of immunosuppressive drugs with human organic anion transporter (OAT) 1 and OAT3, and multidrug resistance-associated protein (MRP) 2 and MRP4

Renal proximal tubule transporters can play a key role in excretion, pharmacokinetic interactions, and toxicity of immunosuppressant drugs. Basolateral organic anion transporters (OATs) and apical multidrug resistance-associated proteins (MRPs) contribute to the active tubular uptake and urinary efflux of these drugs, respectively. We studied the interaction of 12 immunosuppressants with OAT1- and OAT3-mediated [(3)H]-methotrexate (MTX) uptake in cells, and adenosine triphosphate-dependent [(3)H]-MTX transport in membrane vesicles isolated from human embryonic kidney 293 cells overexpressing human MRP2 and MRP4. Our results show that at a clinically relevant concentration of 10 μM, mycophenolic acid inhibited both OAT1- and OAT3-mediated [(3)H]-MTX uptake. Cytarabine, vinblastine, vincristine, hydrocortisone, and mitoxantrone inhibited only OAT1, whereas tacrolimus, azathioprine, dexamethasone, cyclosporine, and 6-mercaptopurine had no effect on both transporters. Cyclophosphamide stimulated OAT1, but did not affect OAT3. With regard to the apical efflux transporters, mycophenolic acid, cyclophosphamide, hydrocortisone, and tacrolimus inhibited MRP2 and MRP4, whereas mitoxantrone and dexamethasone stimulated [(3)H]-MTX transport by both transporters. Cyclosporine, vincristine, and vinblastine inhibited MRP2 only, whereas 6-mercaptopurine inhibited MRP4 transport activity only. Cytarabine and azathioprine had no effect on either transporter. In conclusion, we charted comprehensively the differences in inhibitory action of various immunosuppressive agents against the 4 key renal anion transporters, and we provide evidence that immunosuppressant drugs can modulate OAT1-, OAT3-, MRP2-, and MRP4-mediated transport of MTX to different extents. The data provide a better understanding of renal mechanisms underlying drug-drug interactions and nephrotoxicity concerning combination regimens with these compounds in the clinic.

Reversal of multidrug resistance by the anti-malaria drug artesunate in the esophageal cancer Eca109/ABCG2 cell line

The overexpression of ATP-binding cassette (ABC) transporters confers multidrug resistance (MDR) to tumor cells. ABCG2 is a member of the ABC superfamily. The present study aimed to investigate the correlation between ABCG2 expression and the MDR of esophageal cancer and to estimate the therapeutic benefit of downregulating ABCG2 expression and reversing chemoresistance in esophageal cells using artesunate (Art). The Eca109/ABCG2 cell line was established by transfecting the ABCG2 gene into Eca109 cells. The Eca109/ABCG2 esophageal cancer cells with ABCG2 gene overexpression were resistant to adriamycin (ADM), daunorubicin (DNR) and mitoxantrone (MIT), which indicated that ABCG2 may be associated with drug resistance in esophageal cancer. Art is a noteworthy antimalarial agent, particularly in severe and drug-resistant cancer cases, as Art is able to reverse drug resistance. In the present study, Art also exerted profound anticancer activity. The mechanism for the reversal of multidrug resistance by Art in esophageal carcinoma was analyzed using cellular experiments, but still remains largely unknown.

A semisynthetic taxane Yg-3-46a effectively evades P-glycoprotein and β-III tubulin mediated tumor drug resistance in vitro

Tumor resistance, especially that mediated by P-glycoprotein (P-gp) and β-III tubulin, is a major obstacle to the efficacy of most microtubule-targeting anticancer drugs in clinics. A novel semisynthetic taxane, 2-debenzoyl-2-(3-azidobenzyl)-10-propionyldocetaxel (Yg-3-46a) was shown to be highly cytotoxic to breast cancer cell lines MCF-7 and MCF/ADR which overexpressed P-gp via long term culture with doxorubicin, and cervical cancer cell lines Hela and Hela/βIII which overexpressed βIII-tubulin via stable transfection with TUBB3 gene. siRNA transfection experiments also confirmed that Yg-3-46a can circumvent P-gp and β-III tubulin mediated drug resistance. In addition, its cytotoxicity was lower than that of paclitaxel in the human mammary cell line HBL-100 and the human telomerase-immortalized retinal pigment epithelium cell line (hTERT-RPE1), suggesting a better safety margin for this compound in vivo. It exhibited more potent microtubule polymerization ability than paclitaxel in vitro, and also induced G2/M phase arrest in MCF-7/ADR cells. Moreover, it was found to induce apoptosis in MCF-7/ADR cells through the caspase-dependent death-receptor pathway by enhancing levels of Fas and FasL, and activating caspase-8 and 3. Yg-3-46a was found to be a poorer substrate of P-gp compared to paclitaxel, in both binding and ATPase experiments, which is likely responsible for its ability to circumvent P-gp mediated multidrug resistance (MDR). All of these results indicate that Yg-3-46a is a novel microtubule-stabilizing agent that has the potential to evade drug resistance mediated by P-gp and β-III tubulin overexpression.

Chemotherapy in Patients with Anthracycline- and Taxane-Pretreated Metastatic Breast Cancer: An Overview

Anthracyclines and taxanes are cytotoxic agents that are commonly used for the treatment of breast cancer, including in the adjuvant, neoadjuvant, and metastatic setting. Each drug class of is associated with cumulative and potentially irreversible toxicity, including cardiomyopathy (anthracyclines) and neuropathy (taxanes). This may either limit the duration of therapy for advanced disease, or prevent retreatment for recurrence if previously used as component of adjuvant or neoadjuvant therapy. Several classes of cytotoxic agents have been evaluated in patients with anthracycline and taxane-pretreated metastatic breast cancer (MBC), including other antitubulins (vinorelbine, ixabepilone, eribulin), antimetabolites (capecitabine, gemcitabine), topoisomerase I inhibitors (irinotecan), platinum analogues (cisplatin, carboplatin), and liposomal doxorubicin preparations. No trials have shown an overall survival advantage for combination chemotherapy in this setting, indicating that single cytotoxic agents should usually be used, expect perhaps in patients with rapidly progressive disease and/or high tumor burden.

Single molecule tracking of P-glycoprotein in live cells reveals dynamic heterogeneity

P-glycoprotein transports chemotherapy drugs from the plasma membrane and allows cancer cells to survive treatment. We transiently transfected PGP labeled with enhanced green fluorescent protein (PGP-EGFP) into MES-SA cells and used single molecule tracking techniques to characterize the dynamics on the surface of live cells. PGP exhibits freely diffusive behavior at short times and is confined at long times with a transition to anomalous diffusion at 0.7 s.

miR-200c sensitizes breast cancer cells to doxorubicin treatment by decreasing TrkB and Bmi1 expression

Acquired resistance to classical chemotherapeutics is a major obstacle in cancer treatment. Doxorubicin is frequently used in breast cancer therapy either as single-agent or in combination with other drugs like docetaxel and cyclophosphamide. All these chemotherapies have in common that they are administered sequentially and often result in chemoresistance. Here, we mimicked this pulse therapy of breast cancer patients in an in vitro cell culture model, where the epithelial breast cancer cell line BT474 was sequentially treated with doxorubicin for several treatment cycles. In consequence, we obtained chemoresistant cells displaying a mesenchymal-like phenotype with decreased levels of miR-200c. To investigate the involvement of miR-200c in resistance formation, we inhibited and overexpressed miR-200c in different cell lines. Thereby, the cells were rendered more resistant or susceptible to doxorubicin treatment. Moreover, the receptor tyrosine kinase TrkB and the transcriptional repressor Bmi1 were identified as miR-200c targets mediating the drug resistance. Hence, we provide a mechanism of acquired resistance to doxorubicin that is caused by the loss of miR-200c. Along with this, our study demonstrates the complex network of microRNA mediated chemoresistance highlighting the challenges in cancer therapy and the importance of novel microRNA-modulating anticancer agents.

Loperamide, an FDA-approved antidiarrhea drug, effectively reverses the resistance of multidrug resistant MCF-7/MDR1 human breast cancer cells to doxorubicin-induced cytotoxicity

Loperamide is an FDA-approved antidiarrhea drug which acts on the μ-opioid receptors in the mesenteric plexus of large intestine and exhibits limited side effects. We hypothesized that loperamide might reverse the multidrug resistance (MDR) of human cancer cells to chemotherapeutic agents. MCF-7/MDR1 cells express high level of MDR1 and are resistant to doxorubicin. We found that loperamide significantly enhanced the cytotoxicity of doxorubicin to MCF-7/MDR1 cells in a dose-dependent manner. In conclusion, loperamide reversed the resistance of MCF-7/MDR1 cells to doxorubicin, suggesting that chemotherapy in combination with loperamide may benefit patients with MDR tumors once applied in clinic.

Pgp inhibition by UIC2 antibody can be followed in vitro by using tumor-diagnostic radiotracers, 99mTc-MIBI and 18FDG

P-glycoprotein (Pgp, ABCB1) is one of the active efflux pumps that are able to extrude a large variety of chemotherapeutic drugs from the cells, causing the phenomenon of multidrug resistance. It has been shown earlier that the combined application of a class of Pgp modulators (e.g. cyclosporine A and SDZ PSC 833) used at low concentrations and UIC2 antibody is a novel, specific, and effective way of blocking Pgp function (Goda et al., 2007). In the present work we study the UIC2 antibody mediated Pgp inhibition in more detail measuring the accumulation of tumor diagnostic radiotracers, 2-[(18)F]fluoro-2-deoxy-d-glucose ((18)FDG) and [(99m)Tc]hexakis-2-methoxybutyl isonitrile ((99m)Tc-MIBI), into Pgp(+) (A2780AD) and Pgp(-) (A2780) human ovarian carcinoma cells. Co-incubation of cells with UIC2 and cyclosporine A (CSA, 2μM) increased the binding of UIC2 more than 3-fold and reverted the rhodamine 123 (R123), daunorubicin (DNR) and (99m)Tc-MIBI accumulation of the Pgp(+) 2780AD cells to approx. the same level as observed in Pgp(-) cells. Similarly, 50μM paclitaxel (Pacl) increased UIC2 binding, and consequently reinstated the uptake of R123, DNR and (99m)Tc-MIBI into the Pgp(+) cells. Blocking Pgp by combined treatments with CSA+UIC2 or Pacl+UIC2 also decreased the glucose metabolic rate of the A2780AD Pgp(+) cells measured in (18)FDG accumulation experiments suggesting that the maintenance of Pgp activity requires a considerable amount of energy. Similar treatments of the A2780 Pgp(-) cells did not result in significant change in the R123, DNR, (99m)Tc-MIBI and (18)FDG accumulation demonstrating that the above effects are Pgp-specific. Thus, combined treatment with the UIC2 antibody and Pgp modulators can completely block the function of Pgp in human ovarian carcinoma cells and this effect can be followed in vitro by using tumor-diagnostic radiotracers, (99m)Tc-MIBI and (18)FDG.

N-(3,4-dimethoxyphenethyl)-4-(6,7-dimethoxy-3,4-dihydroisoquinolin-2[1H]-yl)-6,7-dimethoxyquinazolin-2-amine (CP-100,356) as a "chemical knock-out equivalent" to assess the impact of efflux transporters on oral drug absorption in the rat

The utility of the diaminoquinazoline derivative CP-100,356 as an in vivo probe to selectively assess MDR1/BCRP-mediated drug efflux was examined in the rat. CP-100,356 was devoid of inhibition (IC(50) >50 microM) against major human P450 enzymes including P4503A4. In human MDR1-transfected MDCKII cells, CP-100,356 inhibited acetoxymethyl calcein (calcein-AM) uptake (IC(50) approximately 0.5 +/- 0.07 microM) and digoxin transport (IC(50) approximately 1.2 +/- 0.1 microM). Inhibition of prazosin transport (IC(50) approximately 1.5 +/- 0.3 microM) in human BCRP-transfected MDCKII cells by CP-100,356 confirmed the dual MDR1/BCRP inhibitory properties. CP-100,356 was a weak inhibitor of OATP1B1 (IC(50) approximately 66 +/- 1.1 microM) and was devoid of MRP2 inhibition (IC(50) >15 microM). In vivo inhibitory effects of CP-100,356 in rats were examined after coadministration with MDR1 substrate fexofenadine and dual MDR1/BCRP substrate prazosin. Coadministration with increasing doses of CP-100,356 resulted in dramatic increases in systemic exposure of fexofenadine (36- and 80-fold increase in C(max) and AUC at a CP-100,356 dose of 24 mg/kg). Significant differences in prazosin pharmacokinetics were also discernible in CP-100,356-pretreated rats as reflected from a 2.6-fold increase in AUC. Coadministration of CP-100,356 and P4503A substrate midazolam did not result in elevations in systemic exposure of midazolam in the rat. The in vivo methodology should have utility in drug discovery in selective and facile assessment of the role of MDR1 and BCRP efflux transporters in oral absorption of new drug candidates.

Pharmacokinetic and pharmacodynamic implications of P-glycoprotein modulation

Modulation of P-glycoprotein (Pgp)-mediated transport has significant pharmacokinetic implications for Pgp substrates. Pharmacokinetic alterations may be at the systemic (blood concentrations), regional (organ or tissue concentrations), or local (intracellular concentrations) level. Regardless of the particular location of Pgp modulation, changes in substrate pharmacokinetics will have the potential to alter the magnitude and duration of pharmacologic effect (pharmacodynamics). It is important to understand each of the aspects of Pgp modulation for a given Pgp substrate in order to predict the degree to which Pgp modulation may affect that substrate, to minimize untoward effects associated with that modulation, or to exploit that modulation for specific therapeutic advantage.

Prolonged disease control in a patient with anthracycline- and taxane-resistant breast cancer

Resistance to chemotherapy is a complex and very frequent problem in the treatment of breast cancer. It is associated with a poor prognosis and short overall survival. We report a patient with advanced breast cancer without response to anthracyclines or taxanes but who controlled the disease for 15 months with the combination of ixabepilone and capecitabine.

Management of advanced breast cancer with the epothilone B analog, ixabepilone

Despite the activity of standard chemotherapies in advanced breast cancer, disease progression remains inevitable. Most patients exposed to anthracyclines and taxanes develop resistance and a significant subset shows primary resistance. The increasing use of these agents as adjuvant therapy may result in more anthracycline- and taxane-resistant patients in the metastatic setting; few treatment options are available for patients with metastatic breast cancer (MBC) resistant to multiple chemotherapies. The heterogeneity of breast cancer represents another therapeutic challenge. Breast cancers may be classified as luminal, human epidermal growth factor 2 (HER2)-positive, or estrogen receptor-, progesterone receptor-, and human epidermal growth factor 2-negative (ER/PR/HER2-negative, triple negative). HER2-positive and ER/PR/HER2-negative tumors are associated with poor prognosis owing to aggressive disease and poor long-term response to therapy. The epothilone B analog ixabepilone has low susceptibility to multiple mechanisms of resistance and has demonstrated activity in patients with MBC resistant to anthracyclines, taxanes, and/or capecitabine. Ixabepilone is the first epothilone to be approved, as monotherapy or in combination with capecitabine, for treatment of resistant/refractory MBC or locally advanced breast cancer. Treatment with ixabepilone is an option for patients with ER/PR/HER2-negative or HER2-positive disease and/or primary resistance to taxanes.

A novel doxorubicin-mitomycin C co-encapsulated nanoparticle formulation exhibits anti-cancer synergy in multidrug resistant human breast cancer cells

Anthracycline-containing treatment regimens are currently the most widely employed regimens for the management of breast cancer. These drug combinations are often designed based on non-cross resistance and minimal overlapping toxicity rather than drug synergism. Moreover, aggressive doses are normally used in chemotherapy to achieve a greater therapeutic benefit at the cost of more acute and long-term toxic effects. To increase chemotherapeutic efficacy while decreasing toxic effects, rational design of drug synergy-based regimens is needed. Our previous work showed a synergistic effect of doxorubicin (DOX) and mitomycin C (MMC) on murine breast cancer cells in vitro and improved efficacy and reduced systemic toxicity of DOX-loaded solid polymer-lipid hybrid nanoparticles (PLN) in animal models of breast cancer. Herein we have demonstrated true anticancer synergy of concurrently applied DOX and MMC, and have rationally designed PLN to effectively deliver this combination to multidrug resistant (MDR) MDA435/LCC6 human breast cancer cells. DOX-MMC co-loaded PLN were effective in killing MDR cells at 20-30-fold lower doses than the free drugs. This synergistic cell killing was correlated with enhanced induction of DNA double strand breaks that preceded apoptosis. Importantly, co-encapsulation of dual agents into a nanoparticle formulation was much more effective than concurrent application of single agent-containing PLN, demonstrating the requirement of simultaneous uptake of both drugs by the same cells to enhance the drug synergy. The rationally designed combination chemotherapeutic PLN can overcome multidrug resistance at a significantly lower dose than free drugs, exhibiting the potential to enhance chemotherapy and reduce the therapeutic limitations imposed by systemic toxicity.

Recent progress in tumor pH targeting nanotechnology

pH-sensitive polymeric micelles and nanogels have recently been developed to target slightly acidic extracellular pH environment of solid tumors. The pH targeting approach is regarded as a more general strategy than conventional specific tumor cell surface targeting approaches, because the acidic tumor microclimate is most common in solid tumors. When nanosystems are combined with triggered release mechanisms by endosomal or lysosomal acidity plus endosomolytic capability, the nanocarriers demonstrated to overcome multidrug resistance of various tumors. This review highlights recent progress of the pH-sensitive nanotechnology developed in Bae research group.