Multidrug Resistance Process Research Articles

Cellular resistance mechanisms in cancer and the new approaches to overcome resistance mechanisms chemotherapy.

Despite major advancements in cancer healing approaches over the last few decades, chemotherapy remains the most popular malignancy treatment. Chemotherapeutic drugs are classified into many kinds based on their mechanism of action. Multidrug resistance (MDR) is responsible for approximately 90% of fatalities in malignancy cases treated with standard chemotherapeutics or innovative targeted medicines. Many innovative prospective anti-cancer medicines displayed high anti-cancer efficacy in a single application. However, combining them with other medications improves cancer treatment efficacy. This supports the belief that a combination of drugs is significantly more effective than a single medicine. Due to the intricacy of MDR processes and the diversity of tumor illnesses, there will rarely be a single medicine that can be utilized to treat all types of cancer. Finding new medications that can reverse MDR in malignancy cells will augment efficacy of chemotherapeutic agents and allow us to treat cancers that are now incurable.

Inhibition of Wnt/β-catenin pathway reverses multi-drug resistance and EMT in Oct4+/Nanog+ NSCLC cells

Cancer drug resistance and epithelial-mesenchymal transition (EMT), a critical process of cancer invasion and metastasis, have recently been associated with the existence of cancer stem cells (CSCs). However, there are no appropriate CSC-markers of non-small cell lung cancer (NSCLC)-associated drug resistance and EMT. It is unknown if and how the drug-resistant and EMT phenotypes in NSCLC cells link to specific stemness-related pathways. Here, we found a significant elevated expression of both Oct4 and Nanog in gefitinib-resistant NSCLC cells, which displayed multi-drug resistance (MDR) properties and exhibited EMT phenotype. Ectopic co-expression of Oct4/Nanog empowered NSCLC cells with cancer stem cell properties, including self-renewal, drug resistance, EMT and high tumorigenic capacity. Following molecular mechanism investigation indicated Oct4/Nanog-regulated drug resistance and EMT change through Wnt/β-catenin signaling activation. Moreover, silencing β-catenin abrogated Oct4/Nanog-mediated MDR and EMT process in NSCLC cells. Our findings propose Wnt/β-catenin pathway as a promising therapeutic target for the treatment of progression and metastasis of NSCLC with CSC-like signatures and epithelial-mesenchymal transition phenotype.

Deciphering the metabolic role of AMPK in cancer multi-drug resistance.

Multi-drug resistance (MDR) is a curious bottleneck in cancer research and chemotherapy, whereby some cells rapidly adapt to the tumor microenvironment via a myriad of heterogeneous metabolic activities. Despite being a major impediment to treatment, there is a silver lining: control over metabolic regulation could be an effective approach to overcome or correct resistance pathways. In this critical review, we comprehensively and carefully curated and analyzed large networks of previously identified proteins associated with metabolic adaptation in MDR. We employed data and text mining to study and categorize more than 600 studies in PubMed, with particular focus on AMPK, a central and fundamental modulator in the energy metabolism network that has been specifically implicated in cancer MDR pathways. We have identified one protein set of metabolic adaptations with 137 members closely related to cancer MDR processes, and a second protein set with 165 members derived from AMPK-based networks, with 28 proteins found at the intersection between the two sets. Furthermore, according to genomics analysis of the cancer genome atlas (TCGA) provisional data, the highest alteration frequency (80.0%) of the genes encoding the intersected proteins (28 proteins), ranked three cancer types with quite remarkable significance across 166 studies. The hierarchical relationships of the entire identified gene and protein networks indicate broad correlations in AMPK-mediated metabolic regulation pathways, which we use decipher and depict the metabolic roles of AMPK and demonstrate the potential of metabolic control for therapeutic intervention in MDR.

Aptamers as targeting ligands and therapeutic molecules for overcoming drug resistance in cancers.

Traditional anticancer therapies are often unable to completely eradicate the tumor bulk due to multi-drug resistance (MDR) of cancers. A number of mechanisms such as micro-environmental stress and overexpression of drug efflux pumps are involved in the MDR process. Hence, therapeutic strategies for overcoming MDR are urgently needed to improve cancer treatment efficacy. Aptamers are short single-stranded oligonucleotides or peptides exhibiting unique three-dimensional structures and possess several unique advantages over conventional antibodies such as low immunogenicity and stronger tissue-penetration capacity. Aptamers targeting cancer-associated receptors have been explored to selectively deliver a therapeutic cargo (anticancer drugs, siRNAs, miRNAs and drug-carriers) to the intratumoral compartment where they can exert better tumor-killing effects. In this review, we summarize current knowledge of the multiple regulatory mechanisms of MDR, with a particular emphasis on aptamer-mediated novel therapeutic agents and strategies that seek to reversing MDR. The challenges associated with aptamer-based agents and approaches are also discussed.

Downregulation of leucine-rich repeats and immunoglobulin-like domains 1 by microRNA-20a modulates gastric cancer multidrug resistance.

Multidrug resistance (MDR) significantly restricts the clinical efficacy of gastric cancer (GC) chemotherapy, and it is critical to search novel targets to predict and overcome MDR. Leucine‐rich repeats and immunoglobulin‐like domains 1 (LRIG1) has been proved to be correlated with drug resistance in several cancers. The present study revealed that LRIG1 was overexpressed in chemosensitive GC tissues and decreased expression of LRIG1 predicted poor survival in GC patients. We observed that upregulation of LRIG1 enhanced chemosensitivity in GC cells. Interestingly, miR‐20a, which was overexpressed in GC MDR cell lines and tissues, was identified to regulate LRIG1 expression by directly targeting its 3′ untranslated region. We also found that inhibition of miR‐20a suppressed GC MDR, and upregulation showed opposite effects. Moreover, we demonstrated that the miR‐20a/LRIG1 axis regulated GC cell MDR through epidermal growth factor receptor (EGFR)‐mediated PI3K/AKT and MAPK/ERK signaling pathways. Finally, LRIG1 expression in human GC tissues is inversely correlated with miR‐20a and EGFR. Taken together, the newly identified miR‐20a/LRIG1/EGFR link provides insight into the MDR process of GC, and targeting this axis represents a novel potential therapeutic strategy to block GC chemoresistance.

Ciclosporin A as a Reversal Agent Against Concurrent Multidrug Resistance in Tumors with Nanobubbles.

The purpose of this work was to challenge the multidrug resistance (MDR) in tumor through nanobubbles (NB) co-loaded reversal agent and chemotherapeutic drug layer by layer. The core/shell NB structure contains Doxorubicin (Dox) as anticancer drug in the core and Ciclosporin A (CsA), a cyclic polypeptide composed of 11 amino acids, as a reversal agent in the shell. The drug was designed to work against concurrent MDR processes and was defined as CsA/Dox/NB. HL60/ADM cells with typical high expression of multidrug resistance associated protein 1 (MRP1) were assessed by flow cytometer, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, and Western blot analysis to observe the in vitro and in vivo anticancer efficacy and reversal ability of MDR. Results demonstrated that the function and expression of MRP1 could be successfully inhibited by CsA as a reversal agent from the pharmaceutical preparation, leading to dramatic increase of intracellular concentration of Dox. The accumulation of anticancer drug in the MDR cancer cells enhanced inhibition of cell proliferation through G2/M arrest and tumor growth of nude mice xenograft model. It was therefore concluded that the CsA/Dox/NB can be a promising drug candidate in overcoming tumor MDR.

Rhamnetin induces sensitization of hepatocellular carcinoma cells to a small molecular kinase inhibitor or chemotherapeutic agents

BackgroundThe rapid development of multi-drug resistance (MDR) process has hindered the effectiveness of advanced hepatocellular carcinoma (HCC) treatments. Notch-1 pathway, which mediates the stress-response, promotes cell survival, EMT (epithelial–mesenchymal transition) process and induces anti-apoptosis in cancer cells, would be a potential target for overcoming MDR process. This study investigated the potential application of rhamnetin, a specific inhibitor of Notch-1 pathway, in anti-tumor drug sensitization of HCC treatment. MethodsThe expression of miR-34a, proteins belonging to Notch-1 signaling pathway or MDR-related proteins was detected by quantitative polymerase chain reaction (qPCR) and western blot assay. To identify whether rhamnetin induces the chemotherapeutic sensitization in HCC cells, the MTT-assays, flow cytometry, soft agar, trans-well and nude mice assays were performed. ResultsThe endogenous expression of miR-34a was significantly increased and the expression of Notch-1 and Survivin was downregulated after rhamnetin treatment. Treatment of rhamnetin also reduced the expression of MDR related proteins P-GP (P-glycoprotein) and BCRP (breast cancer resistance protein). Rhamnetin increased the susceptibility of HCC cells and especially HepG2/ADR, a MDR HCC cell line, to a small molecular kinase inhibitor sorafenib or chemotherapeutic drugs etoposide and paclitaxel. The IC50 value of those drugs correspondingly decreased. ConclusionsTogether, our findings suggest that rhamnetin treatment may attenuate the MDR process in HCC cells. These findings may contribute to more effective strategies for HCC therapy. General significanceRhamnetin acts as a promising sensitizer to chemotherapy and may be a novel approach to overcome the MDR process of HCC.

EGFR/HER2 inhibitors effectively reduce the malignant potential of MDR breast cancer evoked by P-gp substrates in vitro and in vivo.

Multidrug resistance (MDR) induced by chemotherapy in breast cancer frequently leads to tumor invasion, metastasis and poor clinical outcome. We preliminarily found that the epidermal growth factor receptor (EGFR) is involved in enhancing the malignant potential of MDR breast cancer cells, but the mechanism remains unclear. In the present study, we demonstrated in vitro and in vivo that EGFR/HER2 promote the invasive and metastatic abilities of MDR breast cancer. More importantly, a new function of EGFR/HER2 inhibitors was revealed for the first time, which could improve the treatment efficacy of breast cancer by reversing the MDR process rather than by inhibiting tumor growth. Firstly, using quantitative real‑time PCR and western blot analysis, we found that overexpression of EGFR/HER2 in MCF7/Adr cells upregulated CD147 and MMP2/9 at both the transcription and protein expression levels, which promoted tumor cell migration, as determined using an in vitro invasion assay. Secondly, the upregulated levels of CD147 and MMP2/9 were decreased when EGFR/HER2 activity was inhibited, and therefore tumor invasion was also significantly inhibited. These phenomena were also demonstrated in nude mouse assays. Additionally, in MDR breast cancer patients, we found that overexpression of EGFR and P‑gp levels led to shorter overall survival (OS) and disease‑free survival (DFS) by IHC assays and Kaplan‑Meier survival analysis. In conclusion, EGFR/HER2 play a crucial role in enhancing CD147 and MMP expression to establish favorable conditions for invasion/metastasis in MDR breast cancer. The scope of application of EGFR/HER2 inhibitors may be expanded in EGFR/HER2‑positive patients. We suggest that MDR breast cancer patients may benefit from novel therapies targeting EGFR/HER2.

Reversal of Multidrug Resistance in Gastric Cancer Cells by E2F‐1 Downregulation In Vitro and In Vivo

Transcription Factor E2F-1 plays a critical role in cell cycle regulation and other biological processes in cells. However whether or not it is involved in the multi-drug resistance (MDR) process of gastric cancer has not been fully elucidated yet. To explore the role of E2F-1 in the MDR process of gastric cancer in vitro and in vivo, a cisplatin-resistant gastric cancer cell line with stable downregulation of E2F-1 was established. E2F-1 shRNA led to downregulation of endogenous E2F-1 mRNA and protein. It significantly promoted the sensitivity of SGC7901/DDP cells to cisplatin, doxorubicin, and fluorouracil. Flow cytometry confirmed that the percentage of apoptotic cells increased after E2F-1 downregulation. This notion was further supported by the observation that downregulation of E2F-1 blocked entry into the S-phase of the cell cycle. Furthermore, downregulation of E2F-1 significantly increased intracellular accumulation of doxorubicin. In addition, we determined the in vivo effects of E2F-1 small interfering RNA (shRNA) on tumor size, and apoptotic cells in tumor tissues were detected by deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and hematoxylin and eosin staining. In molecular studies, semiquantitative RT-PCR and western blotting revealed that E2F-1 downregulation could inhibit expression of MDR1, MRP, Bcl-2/Bax, c-Myc, Skp2, Survivin, and Cyclin D1. E2F-1 may be involved in regulating multiple signaling pathways in reversing MDR, suggesting that E2F-1 may represent a novel target for gastric cancer therapy.

Breast Cancer Resistance Protein (BCRP) in Adult Acute Lymphoblastic Leukemia Patients.

The transporter breast cancer resistance protein (BCRP) is a member of the ATP-binding cassette which has been recently described as a protein involved in the multidrug resistance (MDR) phenotype. There are currently no reports concerning the role of this protein in adult acute lymphoblastic leukemia (ALL). The aim of this study was to evaluate the frequency of BCRP expression, its correlation with other MDR-related proteins and their prognostic role in 93 untreated adult ALL patients enrolled in the GIMEMA protocols LAL 0496 and LAL 2000. BCRP protein expression was detected by flow cytometry using the monoclonal antibody BXP-34 (Kamiya, Seattle, WA) and the analysis was performed by the Kolmogorov-Smirnov (KS) statistic test (D-value). Detection of BCRP in the cell lines MCF7 pcDNA3 and MDA231 pcDNA3 showed a D-value of 0.12 ± 0.11 and 0.09 ± 0.06, respectively (negative controls). In contrast, the cell lines MCF7 pcDNA3 clone 8 and MDA231 pcDNA3 clone 23 overexpressed BCRP with a D-value of 0.44 ± 0.21 and 0.33 ± 0.11, respectively (positive controls). Analysis of primary ALL samples showed a BCRP expression (D-value >0.20) in 70/93 (75.3%) cases, with a mean value of 0.33 ± 0.19 (range 0.00-0.87, median 0.33) in the overall population analyzed. BCRP expression resulted higher (mean 0.34 ± 0.03) in samples from patients with WBC counts ≥100 x 109/L compared to the values (mean 0.26 ± 0.13) found in those with lower WBC counts (P=0.06). No significant difference was found between BCRP expression and the clinical characteristics of the patients. The analysis was then extended to the Multidrug Resistance Associated protein (MRP1) and to the MDR1/P-glycoprotein-170 (MDR1). A D-value ≥0.20 and ≥0.05 was found in 53.4% (39/73) and 30.2% (26/86) of cases, respectively. Samples analyzed for both BCRP and MRP1 expression (73/93) showed a significant correlation (R2 = 0.25; P=0.0001): 12.3% of samples were negative for both proteins, while 43.8% expressed both BCRP and MRP1 proteins. In addition, MRP1 negative samples showed lower BCRP levels (mean 0.30, range 0–0.60) compared to MRP1 positive cases (mean 0.38, range 0–0.87) (P=0.017). BCRP expression did not correlate with MDR1 expression. None of these MDR markers correlated separately with achievement of complete remission (CR). In contrast, BCRP/MRP1 co-expression correlated significantly (P=0.034) with failure to respond to induction treatment: 47.8% (11/23) of BCRP+/MRP1+ patients failed to achieve CR, while 78.4% (29/37) of cases negative for only one protein (BCRP-/MRP1+ or BCRP+/MRP1−) or for both (BCRP-/MRP1-) responded to induction treatment. Multivariate analysis (Backward method) confirmed the unfavorable prognostic role on CR of these two proteins concomitantly expressed (P=0.029; OR 0.27, 95% CI, 0.081–0.87). In conclusion, our study shows that BCRP is expressed in a significant proportion of adult ALL. The co-expression of BCRP and MRP1 plays an unfavorable prognostic role on achievement of CR in ALL. These data suggest that the resistance phenotype may be the result of the combined effects of several transporter proteins involved in the MDR process and therefore detection of all these proteins may better predict clinical response to induction treatment.

Imaging drug resistance with radiolabeled molecules.

A major obstacle to successful cancer chemotherapy is drug resistance. Multidrug resistance (MDR) is often seen with chemotherapeutic agents such as anthracycline derivatives, vinca alkaloids and taxanes. Multiple aspects of cellular biochemistry have been implicated in the MDR process. Cellular mechanisms of resistance are due to the presence of efflux pumps, P-glycoprotein (P-gp) and multiple resistance-associated protein (MRP), which belong to the ATP-binding cassette (ABC) family of transporters. Another form of drug resistance is involved in the chemotherapy of cancers with alkylating agents such as nitrosourea derivatives and nitrogen mustards. The cytotoxicity of these agents is primarily due to alkylation of the DNA guanine residues at their O6-position, which leads, via a cascade of events, to DNA strand breaks. The DNA repair protein, alkylguanine-DNA alkyl transferase (AGT) removes the alkyl groups from the lesions stoichiometrically to a cysteine in its active site. This process is irreversible and results in the degradation of the protein and its recovery is entirely from de novo synthesis. Noninvasive methodologies for monitoring the transport activity of these efflux pumps and determining tumor content of AGT could serve as critical tools for optimizing chemotherapeutic protocols on a patient-specific basis and gaining an understanding of the dynamics of resistance in living patients. In this review, we will describe the efforts made to date to synthesize radioactive probes of chemotherapy resistance and their use to quantitate these transporters and DNA repair protein by radionuclide imaging.