In breast cancer patients on a fluorouracil-epirubicin (EPI)-cyclophosphamide (FEC) regimen and intravenous fosaprepitant (FAP) during chemotherapy, infusion-site adverse events such as vascular pain and induration and/or phlebitis are observed. In the present study, adverse events induced by the FEC regimen and FAP, a prodrug of aprepitant (AP), were studied based on the vascular tissue distribution of EPI in rats. Rats were treated with intravenous FAP (3 mg/kg, 10 min-constant rate infusion) or oral AP (3 mg/kg) and then intravenous EPI (1 mg/kg, 5 min-constant rate infusion) as follows: FAP-S Group, FAP and then EPI was infused from the same site on the jugular vein; FAP-D Group, FAP and then EPI was infused from different jugular veins (left and right); and AP Group, AP was administered orally and EPI was infused from the jugular vein. Concentrations of EPI in vascular tissue at the EPI infusion sites and opposite sites of the jugular vein (left and right, respectively) were measured at 30 min and 24 h after EPI infusion. Histological observation of the EPI infusion site was also made separately. In rats, the tissue concentrations of EPI at the infusion site in the FAP-S group were higher than those in the FAP-D and AP groups. Inflammation and necrosis were observed at the EPI infusion-site vascular tissue of the FAP-S group, but not of the FAP-D and AP groups. These findings could aid the development of an approach to avoid infusion-site adverse events in anthracycline-based chemotherapy in the clinical practice.

The encapsulation of anticancer drugs in a liposome structure protects the drug during circulation and increases drug accumulation in the cancer tissue and antitumor activity while decreasing drug toxicity. This paper presents a new method of active drug loading based on a vitamin C pH/ion gradient. Formulations were characterized in terms of the following parameters: optimal external pH, time and drug-to-lipid ratio for the purpose of remote loading, and in vitro stability. In the case of the selected drug, epirubicin (EPI), its coencapsulation increases its anticancer activity through a possibly synergistic effect previously reported by other groups for a free nonencapsulated drug/vitamin C cocktail. The method also has another advantage over other remote-loading methods: it allows faster drug release through liposome destabilization at the tumor site, thanks to the very good solubility of the EPI vitamin C salt, as seen on cryogenic transmission electron microscopy images. This influences the drug-release process and increases the anticancer activity of the liposome formulation. The liposomes are characterized as stable, with very good pharmacokinetics (half-life 18.6 hours). The antitumor activity toward MCF-7 and 4T-1 breast cancer cells was higher in the case of EPI loaded via our gradient than via an ammonium sulfate gradient. Finally, the EPI liposomal formulation and the free drug were tested using the murine 4T-1 breast cancer model. The antitumor activity of the encapsulated drug was confirmed (tumor-growth inhibition over 40% from day 16 until the end of the experiment), and the free drug was shown to have no anticancer activity at the tested dose.

This study aimed to examine the efficacy of epirubicin-loaded gelatin hydrogel (EPI-H) in the treatment of superficial urothelium carcinoma. Hydrogel was prepared by Schiff base-crosslinking of gelatin with glutaraldehyde. EPI-H exhibited high entrapment efficiency (59.87% ± 0.51%). EPI-H also increased epirubicin accumulation in AY-27 cells when compared with the effect of aqueous solutions of epirubicin (EPI-AQ); respective epirubicin-positive cell counts were 69.0% ± 7.6% and 38.3% ± 5.8%. EPI-H also exhibited greater cytotoxicity against AY-27 cells than that of EPI-AQ; IC50 values were 13.1 ± 1.1 and 7.5 ± 0.3 μg/mL, respectively. Cystometrograms showed that EPI-H reduced peak micturition, threshold pressures, and micturition duration, and that it increased bladder compliance more so than EPI-AQ. EPI-H enhanced epirubicin penetration into basal cells of urothelium in vivo, whereas EPI-AQ did so only to the umbrella cells. EPI-H inhibited tumor growth upon intravesical instillation to tumor-bearing bladder of F344 rats, inducing higher levels of caspase-3 expression than that observed with EPI-AQ treatment; the number of caspase-3 positive cells in treated urothelium carcinoma was 13.9% ± 4.0% (EPI-AQ) and 34.1% ± 1.0%, (EPI-H). EPI-H has value as an improved means to administer epirubicin in intravesical instillation treatments for bladder cancer.

Chemotherapy Related Cognitive Impairment (CRCI), also called chemobrain, diminishes cancer patient's life quality. Breast cancer (BC) patients have been described to be importantly affected, however, the mechanism leading to CRCI has not been fully elucidated. Recent research proposes microglia as the main architect of CRCI, thus dysregulations in these cells could trigger CRCI. The aim of this research was to evaluate the effects of two drugs commonly used against breast cancer, cyclophosphamide (CTX) and epirubicin (EPI), on the microglia cell line SIM-A9, using the BC cell line, 4T1, as a control. Our results show that CTX and EPI decrease microglia-cell viability and increase cell death on a concentration-dependent manner, being 5 and 2 times more cytotoxic to microglia cell line than to breast cancer 4T1cells, respectively. Both chemotherapies induce cell cycle arrest and a significant increase in p53, p16 and γ-H2AX in breast cancer and microglia cells. Furthermore, mitochondrial membrane potential (ΔΨm) diminishes as cell death increases, and both chemotherapies induce reactive oxygen species (ROS) production on SIM-A9 and 4T1. Moreover, caspase activation increases with treatments and its pharmacological blockade inhibits CTX and EPI induced-cell death. Finally, low concentrations of CTX and EPI induce γ-H2AX, and EPI induces cytokine release, NO production and Iba-1 overexpression. These findings indicate that microglia cells are more sensitive to CTX and EPI than BC cells and undergo DNA damage and cell cycle arrest at very low concentrations, moreover EPI induces microglia activation and a pro-inflammatory profile.

Two anthracyclines, doxorubicin and epirubicin have been widely used alone or in combination with other antitumor reagents in the chemotherapeutic treatment of various malignancies. Although therapeutic efficacy of anthracyclines has been studied extensively, precise cytotoxic mechanism of these drugs is not been completely elucidated. Here we show that epirubicin-induced degradation of transmembrane protein gp130 contributes to antitumor effect of epirubicin. gp130 is degraded by epirubicin in a proteasome- and autophagy-dependent manner. Epirubicin induces activation of p38-MK2 signaling pathway to phosphorylate gp130 at Ser 782, which results in gp130 internalization and degradation by lysosome. Although mutation of Ser 782 to Ala or Cys in gp130 upregulates global epirubicin-induced autophagy, reduced degradation of gp130 accompanied with enhanced Stat3 phosphorylation at tyrosine 705 is observed. We also show that epirubicin-resistant tumor cells express higher level of gp130. Altogether, our results indicate that degradation of gp130 and subsequent reduction of gp130-Stat3 signaling contributes to epirubicin-induced tumor cell death.

The combinatory use of high-intensity focused ultrasound (HIFU) and epirubicin (EPI)-conjugated polymeric micellar nanoparticles (NC-6300) is thought to be a less invasive and more efficient method of cancer therapy. To investigate the mechanism underlying the combination effect, we examined the effect of trigger-pulsed HIFU (TP-HIFU) and NC-6300 from the perspective of reactive oxygen species (ROS) generation, which is considered the primary function of sonodynamic therapy (SDT), and changes in drug characteristics. TP-HIFU is an effective sequence for generating hydroxyl radicals to kill cancer cells. EPI was susceptible to degradation by TP-HIFU through the production of hydroxyl radicals. In contrast, EPI degradation of NC-6300 was suppressed by the hydrophilic shell of the micelles. NC-6300 also exhibited a sonosensitizer function, which promoted the generation of superoxide anions by TP-HIFU irradiation. The amount of ROS produced by TP-HIFU reached a level that caused structural changes to the cellular membrane. In conclusion, drug-conjugated micellar nanoparticles are more desirable for SDT because of accelerated ROS production and drug protection from ROS. Furthermore, a combination of NC-6300 and TP-HIFU is useful for minimally invasive cancer therapy with cooperative effects of HIFU-derived features, antitumor activity of EPI, and increased ROS generation to cause damage to cancer cells.

Chemoresistance is a primary cause of treatment failure in cancer and a common property of tumor-initiating cancer stem cells. Overcoming mechanisms of chemoresistance, particularly in cancer stem cells, can markedly enhance cancer therapy and prevent recurrence and metastasis. This study demonstrates that the delivery of Epirubicin by nanodiamonds is a highly effective nanomedicine-based approach to overcoming chemoresistance in hepatic cancer stem cells. The potent physical adsorption of Epirubicin to nanodiamonds creates a rapidly synthesized and stable nanodiamond-drug complex that promotes endocytic uptake and enhanced tumor cell retention. These attributes mediate the effective killing of both cancer stem cells and noncancer stem cells in vitro and in vivo. Enhanced treatment of both tumor cell populations results in an improved impairment of secondary tumor formation in vivo compared with treatment by unmodified chemotherapeutics. On the basis of these results, nanodiamond-mediated drug delivery may serve as a powerful method for overcoming chemoresistance in cancer stem cells and markedly improving overall treatment against hepatic cancers.

Vascular endothelial injury is important in anthracycline-induced cardiotoxicity. Anthracyclines seriously damage the mitochondrial function and mitochondrial homeostasis. In this study, we investigated the damage of epirubicin to vascular endothelial cells and the protective role of metformin from the perspective of mitochondrial homeostasis. We found that epirubicin treatment resulted in DNA double-strand breaks (DSB), elevated reactive oxygen species (ROS) production, and excessive Angiotensin II release in HUVEC cells. Pretreatment with metformin significantly mitigated the injuries caused by epirubicin. In addition, inhibited expression of Mitochondrial transcription factor A (TFAM) and increased mitochondria fragmentation were observed in epirubicin-treated cells, which were partially resumed by metformin pretreatment. In epirubicin-treated cells, knockdown of TFAM counteracted the attenuated DSB formation due to metformin pretreatment, and inhibition of mitochondrial fragmentation with Mdivi-1 decreased DSB formation but increased TFAM expression. Furthermore, epirubicin treatment promoted mitochondrial fragmentation by stimulating the expression of Dynamin-1-like protein (DRP1) and inhibiting the expression of Optic atrophy-1(OPA1) and Mitofusin 1(MFN1), which could be partially prevented by metformin. Finally, we found metformin could increase TFAM expression and decrease DRP1 expression in epirubicin-treated HUVEC cells by upregulating the expression of calcineurin/Transcription factor EB (TFEB). Taken together, this study provided evidence that metformin treatment was an effective way to mitigate epirubicin-induced endothelial impairment by maintaining mitochondrial homeostasis.

The aim of this study was to investigate the benefit of weekly epirubicin in the treatment of metastatic hormone-resistant prostate cancer. One hundred and forty-eight patients with metastatic hormone-resistant prostate cancer received weekly 30-min intravenous infusions of epirubicin 30 mg m(2) of body surface area. The primary end-point was palliative response, defined as a reduction in pain intensity and an improvement in performance status. The secondary end-points were the duration of the palliative response, quality of life and survival. Fifty-seven (44%) of the 131 evaluable patients met the primary criterion of palliative response after six treatment cycles and 73 (56%) after 12 cycles; the median duration of the response was 9 months (range 1-11). The median global quality of life improved in 52% of the patients after six cycles and in 68% after 12 cycles. The 12- and 18-month survival rates were respectively 56 and 31%, with a median survival of 13+ months (range 1-36). The treatment was well tolerated: grade 3 neutropenia was observed in 8% of the patients, grade 3 anaemia in 7%, and grade 3 thrombocytopenia in 3%. None of the patients developed grade 4 toxicity or congestive heart failure. Weekly epirubicin chemotherapy can lead to a rapid and lasting palliative result in patients with metastatic HRPC, and have a positive effect on the quality of life and survival.

The design and study of efficient polymer-based drug delivery systems for the controlled release of anticancer drugs is one of the pillars of nanomedicine. The fight against metastatic and invasive cancers demands therapeutic candidates with increased and selective toxicity towards malignant cells, long-term activity and reduced side effects. In this sense, polyphosphazene nanocarriers were synthesized for the sustained release of the anticancer drugs camptothecin (CPT) and epirubicin (EPI). Linear poly(dichloro)phosphazene was modified with lipophilic tocopherol or testosterone glycinate, with antioxidant and antitumor activity, and with hydrophilic Jeffamine M1000 to obtain different polyphosphazene nanocarriers. It allowed us to encapsulate the lipophilic CPT and the more hydrophilic EPI. The encapsulation process was carried out via solvent exchange/precipitation, attaining a 9.2-13.6 wt% of CPT and 0.3-2.4 wt% of EPI. CPT-loaded polyphosphazenes formed 140-200 nm aggregates in simulated body physiological conditions (PBS, pH 7.4), resulting in an 80-100-fold increase of CPT solubility. EPI-loaded polyphosphazenes formed 250 nm aggregates in an aqueous medium. CPT and EPI release (PBS, pH 7.4, 37 °C) was monitored for 202 h, being almost linear during the first 8 h. The slow release of testosterone and tocopherol was also sustained for 150 h in PBS (pH 7.4 and 6.0) at 37 °C. The co-delivery of testosterone or tocopherol and the anticancer drugs from the nanocarriers was expected. Cells of the human breast cancer cell line MCF-7 demonstrated good uptake of anticancer-drug-loaded nanocarriers after 6 h. Similarly, MCF-7 spheroids showed good uptake of the anticancer-drug-loaded aggregates after 72 h. Almost all anticancer-drug-loaded polyphosphazenes exhibited similar or superior toxicity against MCF-7 cells and spheroids when compared to raw anticancer drugs. Additionally, cell-cycle arrest in the G2/M phase was increased in response to the drug-loaded nanocarriers. Almost no toxicity of anticancer-drug-loaded aggregates against primary human lung fibroblasts was observed. Furthermore, the aggregates displayed no hemolytic activity, which is in contrast to the parent anticancer drugs. Consequently, synthesized polyphosphazene-based nanocarriers might be potential nanomedicines for chemotherapy.

Epirubicin is a chemotherapy agent for hepatocellular carcinoma (HCC). However, the outcome of HCC patients receiving epirubicin remains unsatisfactory. Moreover, our previous study indicated that celecoxib suppresses HCC progression and liver cancer stemness. This study evaluated the potential of celecoxib to serve as a complementary therapy during epirubicin treatment. Cell proliferation, apoptosis, invasiveness, and anchorage-independent growth were analyzed in hepatoma cells. Therapeutic efficacy was validated in rat orthotopic Novikoff hepatoma. After animal sacrifice, the antitumor mechanism of celecoxib and epirubicin combined therapy was investigated by histological analysis. Celecoxib enhanced the cytotoxic activity of epirubicin in HCC cells by promoting apoptosis. Besides, celecoxib potentiated the antineoplastic function of epirubicin in inhibiting the invasiveness and anchorage-independent growth of HCC cells. Ultrasound monitoring showed that combined therapy was more potent than either therapy alone in perturbing HCC progression. Consistently, the size and weight of dissected HCC tissues from rats receiving combined therapy were smallest among all groups. HCC treated with combined therapy exhibited the highest prevalence of apoptotic cells, which was accompanied by reduced proliferating and angiogenic activities in tumor tissues. Moreover, the expression levels of cancer stemness markers (CD44 and CD133) and drug transporter MDR-1 were significantly diminished in rats receiving combined therapy. Besides, celecoxib treatment increased the infiltration of cytotoxic T lymphocytes (CTLs) and reduced the number of regulatory T cells (Tregs), tumor-associated macrophages (TAMs), and the expression of immune checkpoint PD-L1 in HCC tissues during epirubicin therapy. Celecoxib augmented the therapeutic efficacy while modulated cancer stemness and antitumor immunity. Thus, celecoxib may serve as complementary therapy to improve the outcome of patients with advanced HCC during epirubicin treatment.

Although epirubicin has significantly improved outcome in breast cancer (BC) patients, it is responsible for myocardial dysfunction that affects patients' quality of life. The use of 2D global longitudinal strain (GLS) has been reported to detect early myocardial dysfunction. The aim of this study was to evaluate how GLS changes can predict cardiotoxicity.

To develop a biodegradable polymeric drug delivery system for the treatment of ovarian cancer with the capacity for non-invasive fate monitoring, we designed and synthesized N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-epirubicin (EPI) conjugates. The polymer backbone was labeled with acceptor fluorophore Cy5, while donor fluorophores (Cy3 or EPI) were attached to HPMA copolymer side chains via an enzyme-cleavable GFLG linker. This design allows elucidating separately the fate of the drug and of the polymer backbone using fluorescence resonance energy transfer (FRET). The degradable diblock conjugate (2P-EPI) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using a bifunctional chain transfer agent (Peptide2CTA). The pharmacokinetics (PK) and therapeutic effect of 2P-EPI (Mw ~100 kDa) were determined in mice bearing human ovarian carcinoma A2780 xenografts. Compared to 1st generation conjugate (P-EPI, Mw <50 kDa), 2P-EPI demonstrated remarkably improved PK such as fourfold terminal half-life (33.22 ± 3.18 h for 2P-EPI vs. 7.55 ± 3.18 h for P-EPI), which is primarily attributed to the increased molecular weight of the polymer carrier. Notably, complete tumor remission and long-term inhibition of tumorigenesis (100 days) were achieved in mice (n=5) treated with 2P-EPI. Moreover, in vitro cell uptake and intracellular drug release were determined via FRET intensity changes. The results establish a solid foundation for future in vivo tracking of drug delivery and chain scission of polymeric conjugates by FRET imaging.

FOXM1 is implicated in genotoxic drug resistance but its mechanism of action remains elusive. We show here that FOXM1-depletion can sensitize breast cancer cells and mouse embryonic fibroblasts (MEFs) into entering epirubicin-induced senescence, with the loss of long-term cell proliferation ability, the accumulation of γH2AX foci, and the induction of senescence-associated β-galactosidase activity and cell morphology. Conversely, reconstitution of FOXM1 in FOXM1-deficient MEFs alleviates the accumulation of senescence-associated γH2AX foci. We also demonstrate that FOXM1 regulates NBS1 at the transcriptional level through an forkhead response element on its promoter. Like FOXM1, NBS1 is overexpressed in the epirubicin-resistant MCF-7Epi(R) cells and its expression level is low but inducible by epirubicin in MCF-7 cells. Consistently, overexpression of FOXM1 augmented and FOXM1 depletion reduced NBS1 expression and epirubicin-induced ataxia-telangiectasia mutated (ATM)phosphorylation in breast cancer cells. Together these findings suggest that FOXM1 increases NBS1 expression and ATM phosphorylation, possibly through increasing the levels of the MRN(MRE11/RAD50/NBS1) complex. Consistent with this idea, the loss of P-ATM induction by epirubicin in the NBS1-deficient NBS1-LBI fibroblasts can be rescued by NBS1 reconstitution. Resembling FOXM1, NBS1 depletion also rendered MCF-7 and MCF-7Epi(R) cells more sensitive to epirubicin-induced cellular senescence. In agreement, the DNA repair-defective and senescence phenotypes in FOXM1-deficent cells can be effectively rescued by overexpression of NBS1. Moreover, overexpression of NBS1 and FOXM1 similarly enhanced and their depletion downregulated homologous recombination (HR) DNA repair activity. Crucially, overexpression of FOXM1 failed to augment HR activity in the background of NBS1 depletion, demonstrating that NBS1 is indispensable for the HR function of FOXM1. The physiological relevance of the regulation of NBS1 expression by FOXM1 is further underscored by the strong and significant correlation between nuclear FOXM1 and total NBS1 expression in breast cancer patient samples, further suggesting that NBS1 as a key FOXM1 target gene involved in DNA damage response, genotoxic drug resistance and DNA damage-induced senescence.

We sought to investigate the effects of epirubicin-nanogold compounds (EPI-AuNP) on hepatocellular carcinoma xenograft growth in nude mice. EPI-AuNP was prepared and hepatoma xenograft model was established in nude mice. The mice were then randomly divided into four groups: the control group with injection of saline, the AuNP treatment group, the EPI treatment group and the EPI-AuNP treatment group. After two weeks, the hepatoma weight and volume of the xenografts were assessed. Our transmission electron microscopy revealed that epirubicin-gold nanoparticles caused significantly more structural changes of hepatocellular carcinoma cells HepG2. The tumor weight in the Epi-AuNP treatment group (0.80±0.11g) was significantly lower than that of the control group (2.48±0.15 g), the AuNP treatment group (1.67±0.17 g), and the EPI treatment group (1.39±0.10g) (P<0.01). Furthermore, the tumor volume of mice in the EPI-AuNP treatment group (0.27±0.06 cm³) was significantly smaller than that of the control group (2.23±0.34 cm³), the AuNP treatment group (1.21±0.25 cm³) and the EPI treatment group (0.81±0.11 cm³) (P<0.01). In conclusion, epirubicin-nanogold compounds (EPI-AuNP) have significant inhibitory effects on the growth of hepatocellular carcinoma cells in vivo.

Polysaccharide based copolymers have been the focus of several research, particularly for the development of drug delivery systems. This study reports on the preparation of nanoparticles from an amphiphilic copolymer obtained by the poly(ε-caprolactone) graft in the structure of cashew gum, via ring-opening polymerization. The synthesis of copolymers was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The copolymers exhibit self-organization capability in water, with critical association concentration of 42 and 50 μg mL-1. The nanoparticle hydrodynamic diameters (212 and 202 nm) revealed a decreasing trend with increasing poly(ε-caprolactone) graft percentage. Epirubicin was used as an anticancer drug model and incorporated into the nanoparticles. The encapsulation efficiency reached 50% and 5.0% drug load. Nanoparticles showed an epirubicin controlled release profile, with maximum release of 93.0 ± 4.0% in 72 h, as well as excellent biocompatibility, according to hemolysis and cytotoxicity assays.

Purpose: Cancer is an example of the most important growing diseases in human society and scientists are trying to treat it without considerable side effects on patient's health. Solid lipids are colloidal nanoparticles that were used in drug delivery due to their several advantages. Methods: In this work, surface modified targeted solid lipid nanoparticles (SLNs) were fabricated by nano-homogenizer using tripalmitin glyceride and stearic acid as lipid constituents. The size of nanoparticles and morphological evaluations were surveyed using particle size analyzer, scanning electron microscopy; Fourier transforms infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). Results: The particle size of 148.5 and appropriate polydispersity index were achieved for lipid nanoparticles with an entrapment efficiency of 86.1%. The FT-IR analysis confirmed the coupling of lysine to the free functional group of SLNs. DSC proved the conjugation of amino acid to the surface of carriers. The in vitro epirubicin (EPI) release test exhibited the further controlled release phenomenon for the lysine conjugated nanoparticles. The cytotoxicity assay showed lower IC50 of lysine conjugated SLNs of EPI on the investigated cell line. Conclusion: These studies showed that the fabricated targeted carrier has a very remarkable anticancer effect on breast cancer cell lines in comparison with pure drug.

Epirubicin/cyclophosphamide (EC) and docetaxel (D) are commonly used in a sequential regimen in the neoadjuvant treatment of early, high-risk or locally advanced breast cancer (BC). Novel approaches to increase the response rate combine this treatment with immunotherapies such as PD-1 inhibition. However, the expected stimulatory effect on lymphocytes may depend on the chemotherapy backbone. Therefore, we separately compared the immunomodulatory effects of EC and D in the setting of a randomized clinical trial.

AXL receptor tyrosine kinase is overexpressed in esophageal adenocarcinoma (EAC) and several other types of malignancies; hence, it may be a valuable therapeutic target. Herein, we investigated the role of AXL in regulating c-MYC expression and resistance to the chemotherapeutic agent epirubicin in EAC. Using in vitro EAC cell models, we found that AXL overexpression enhances epirubicin resistance in sensitive cells. Conversely, genetic knockdown or pharmacological inhibition of AXL sensitizes resistant cells to epirubicin. Notably, we showed that inhibition or knockdown of c-MYC markedly sensitizes AXL-dependent resistant cells to epirubicin, and our data demonstrated that AXL promotes epirubicin resistance through transcriptional upregulation of c-MYC. We showed that AXL overexpression significantly increased transcriptional activity, mRNA, and protein levels of c-MYC. Conversely, AXL knockdown reversed these effects. Mechanistic investigations indicated that AXL upregulates c-MYC expression through activation of the AKT/β-catenin signaling pathway. Data from a tumor xenograft mouse model indicated that inhibition of AXL with R428 in combination with epirubicin synergistically suppresses tumor growth and proliferation. Our results demonstrate that AXL promotes epirubicin resistance through transcriptional upregulation of c-MYC in EAC. Our findings support future clinical trials to assess the therapeutic potential of R428 in epirubicin-resistant tumors with overexpression of AXL and activation of c-MYC.

Background: Gastric cancer is one of the most common malignancies worldwide. Epirubicin (EPI) is used extensively in the treatment of multiple cancers despite its tendency to induce multidrug resistance though overexpression of the ABCB1 efflux pump. However, this overexpression can be disrupted using short interfering RNAs (siRNAs). Objective and Methods: The aim of this study was to explore approaches to reverse EPI resistance and thus increase the success of chemotherapy treatment in an EPI-resistant gastric cancer cell subline (AGS/EPI). Methods: The study focused on effects of ABCB1 knockdown by siRNA technology using TaqMan gene expression assays with quantitative real-time reverse-transcription PCR (qRT-PCR). MTT assays were performed to evaluate viability and prolifer in subline. ABCB1 protein localization and EPI intracellular fluorescence intensity in AGS/EPI cells were detected by confocal microscopy. Results: The siRNA efficiently downregulated ABCB1 mRNA in AGS/EPI cells. Thus MDR reversal was clearly demonstrated in the AGS/EPI cells, offering the possibility of future in vitro chemoresistance assays for the GC field. Conclusions: ABCB1 knockdown decreased EPI efflux and increased EPI sensitivity in AGS/EPI cells. This result provides a novel strategy for targeted gene therapy to reverse EPI resistance in gastric cancer.