Development Of Multidrug Resistance Research Articles

Characterization of site-specific glycosylation of secreted proteins associated with multi-drug resistance of gastric cancer.

Multi-drug resistance (MDR) remains a great obstacle to effective chemotherapy for gastric cancer. A number of secreted glycoproteins have been reported to be involved in the development of MDR in gastric cancer. However, whether glycosylation of secreted glycoproteins changes during MDR of gastric cancer is unclear. Our present work manifested that N-glycosites and site-specific glycoforms of secreted proteins in drug-resistant cell lines were distinctly different from those in the parental cell line for the first time. Further characterization highlighted the significance of some aberrantly glycosylated secretory proteins in MDR, suggesting that manipulating the glycosylation of specific glycoproteins could be a potential target for overcoming multi-drug resistance in gastric cancer.

Critical involvement of the α(1,2)-fucosyltransferase in multidrug resistance of human chronic myeloid leukemia.

The fucosyltransferases are key enzymes in cell surface antigen synthesis during multidrug resistance (MDR) development. The aim of the present study was to analyze the alteration of α(1,2)-fucosyltransferase involved in MDR development in human chronic myeloid leukemia (CML). FUT1 was overexpressed in three CML/MDR cell lines and peripheral blood mononuclear cells (PBMC) of CML patients. However, no significant changes of FUT2 were observed. The altered levels of FUT1 had a significant impact on the phenotypic variation of MDR of K562 and K562/ADR cells, the activity of EGFR/MAPK pathway and P-glycoprotein (P-gp) expression. Blocking the EGFR/MAPK pathway by its specific inhibitor PD153035 or EGFR small interfering RNA (siRNA) resulted in the reduced MDR of K562/ADR cells. This study indicated that α(1,2)-fucosyltransferase involved in the development of MDR of CML cells probably through FUT1 regulated the activity of EGFR/MAPK signaling pathway and the expression of P-gp.

EXPRESSION OF GENES RESPONSIBLE FOR MULTIDRUG RESISTANCE IN RELAPSED/REFRACTORY MULTIPLE MYELOMA PATIENTS

Background: Multidrug resistance (MDR) is a natural phenomenon in development of solid and hematologic tumors. This phenomenon significantly influences both immediate and remote outcome of treatment. In this connection, an interest arises to studying this problem in multiple myeloma (MM) patients with expressed clinical signs of tumorous progression, the main of them being an absence or loss of the response to antitumor treatment. Aim: To study the expression of messenger RNA (mRNA) of a series of MDR genes, namely MDR1, MRP1, LRP, BCRP responsible for MDR development in the bone marrow aspirate of resistant patients prior to bortezomib-containing chemotherapy. Materials and methods: Study group included 19 relapsed/refractory multiple myeloma patients. Investigation of MDR genes expression was carried out on the cells of the bone marrow mononuclear fraction containing plasmocytes. The mRNA level was analyzed by semiquantitative RT-PCR (polymerase chain reaction with reverse transcription). Patients were treated with bortezomib-containing chemotherapy hereafter. Results: mRNA expression of genes MDR1, MRP1, BCRP was revealed in all (100%) patients, and that of gene LRP – in 81% of myeloma samples. The levels of MDR genes mRNA expression were different. On this basis, two groups of patients were identified: with the levels of MDR genes expression above and beyond the average. Conclusion: 100%-expression of MDR genes (MDR1, MRP1, BCRP) mRNA was revealed in drug resistant MM patients. The median survival in group of patients with higher levels of MDR genes mRNA expression versus lower levels of MDR genes mRNA expression was statistically significant.

Vitamin E derivative-based multifunctional nanoemulsions for overcoming multidrug resistance in cancer

The multidrug resistance (MDR), including intrinsic and acquired multidrug resistance, is a major problem in tumor chemotherapy. Here, we proposed a strategy for modulating intrinsic and/or acquired multidrug resistance by altering the levels of Bax and Bcl-2 expression and inhibiting the transport function of P-gp, increasing the intracellular concentration of its substrate anticancer drugs. Vitamin E derivative-based nanoemulsions containing paclitaxel (MNEs-PTX) were fabricated in this study, and in vitro anticancer efficacy of the nanoemulsion system was evaluated in the paclitaxel-resistant human ovarian carcinoma cell line A2780/Taxol. The MNEs-PTX exhibited a remarkably enhanced antiproliferation effect on A2780/Taxol cells than free paclitaxel (PTX) (p < 0.01). Compared with that in the Taxol group, MNEs-PTX further decreased mitochondrial potential. Vitamin E derivative-based multifunctional nanoemulsion (MNEs) obviously increased intracellular accumulation of rhodamine 123 (P-gp substrate). Overexpression of Bcl-2 is generally associated with tumor drug resistance, we found that MNEs could reduce Bcl-2 protein level and increase Bax protein level. Taken together, our findings suggest that anticancer drugs associated with MNEs could play a role in the development of MDR in cancers.

Role of miR-27a, miR-181a and miR-20b in gastric cancer hypoxia-induced chemoresistance

ABSTRACTDespite the search for new therapeutic strategies for gastric cancer (GC), there is much evidence of progression due to resistance to chemotherapy. Multidrug resistance (MDR) is the ability of cancer cells to survive after exposure to chemotherapeutic agents. The involvement of miRNAs in the development of MDR has been well described but miRNAs able to modulate the sensitivity to chemotherapy by regulating hypoxia signaling pathways have not yet been fully addressed in GC. Our aim was to analyze miR-20b, miR-27a and miR-181a expression with respect to (epirubicin/oxaliplatin/capecitabine (EOX)) chemotherapy regimen in a set of GC patients, in order to investigate whether miRNAs deregulation may influence GC MDR also via hypoxia signaling modulation. Cancer biopsy were obtained from 21 untreated HER2 negative advanced GC patients, retrospectively analyzed. All patients received a first-line chemotherapy (EOX) regimen. MirWalk database was used to identify miR-27a, miR-181a and miR-20b target genes. The expression of miRNAs and of HIPK2, HIF1A and MDR1 genes were detected by real-time PCR. HIPK2 localization was assessed by immunohistochemistry. Our data showed the down-regulation of miR-20b, miR-27a, miR-181a concomitantly to higher levels of MDR1, HIF1A and HIPK2 genes in GC patients with a progressive disease respect to those with a disease control rate. Moreover, immunohistochemistry assay highlighted a higher cytoplasmic HIPK2 staining, suggesting a different role for it. We showed that aberrant expression of miR-20b, miR27a and miR-181a was associated with chemotherapeutic response in GC through HIF1A, MDR1 and HIPK2 genes modulation, suggesting a possible novel therapeutic strategy.

Isolation and epidemiology of multidrug resistant Escherichia coli from goats in Cox's Bazar, Bangladesh

Objective: The investigation was undertaken to measure the epidemiological features and antimicrobial sensitivity patterns of Escherichia coli among different breeds of goats in Cox’s Bazar, Bangladesh. Materials and methods: A total of 150 rectal swab samples were collected from selected goats. The samples were subjected for the isolation of E. coli through a series of conventional bacteriological and biochemical techniques. The isolated E. coli were used for assessing antimicrobial susceptibility by disk diffusion method. Besides prevalence study, nine risk factors were studied; the risk factors were- breed, age, hygienic status, sex, history of recent transportation, season, diarrhea, body condition score, and source of drinking water. Results: The overall prevalence of E. coli in the rectal swabs of goats was 52% (n=78/150). The young goats were highly susceptible (65.0%; n=52/80) to E. coli infection as compared to adults (37.1%; n=26/70). The prevalence was higher (66.7%; n=42/63) in the goats that was reared in poor hygienic condition as compared to the goats that were reared under good hygienic condition. The influence of the source of drinking water on E. coli prevalence was found to be higher both in pond (63.6%; n=7/11) and municipality (61.4%; n=51/83) supplied water as compared to tube-well (35.7%; n=20/56). The goats having recent transportation history showed higher prevalence (64.8%; n=35/54). The prevalence was higher in diarrheic goats (62.0%; n=49/79) than non-diarrheic goats. Among the E. coli isolates (n=78), 31 were found to be multidrug resistant (MDR) to 3 to 8 subclasses of antimicrobials. Conclusion: Presence of MDR E. coli in the studied goats suggest the probable acquisition, development and transmission of MDR E. coli through a number of influencing factors to other animals and potentially to human.

Prevalence of Rifampicin Resistance and Associated Risk Factors among Suspected Multidrug Resistant Tuberculosis Cases in TB Centers Mogadishu-Somalia: Descriptive Study

Introduction and Background: Multidrug-resistant tuberculosis (MDR-TB) has emerged as a significant global health concern. Patients who had failed previous TB treatment, relapsed after treatment, contacted known MDRTB patients or defaulted during previous treatment, and HIV patients are considered to be suspected and at high risk for developing drug resistant TB specially MDR-TB. However, there is little data available on the prevalence and trends of MDR tuberculosis in national level but luck of it in Mogadishu is our main concern. Methodology: This was a crosssectional, descriptive study involving all suspected MDR TB patients attended at the Mogadishu three Tb centers. Results: A total of 138 cases of suspected MDRTB patients were included in the study. Of these, 70 patients (51%) had rifampicin resistant-TB. Of the 138 study participants, 94 (68.62%) were between 21 - 40 years old that indicates the dominance of productive age group (21 - 40 years). Previous Tuberculosis treatment has been noted to be a major risk factor for development of multidrug resistance tuberculosis. MDR-TB prevalence is significantly higher in male than female patients. Conclusion and Interpretation: The prevalence of Rifampicin resistance among these high risk groups was significant. The high association of previous TB treatment to MDR-TB might be explained due to inappropriate anti-tubercular regimens, sub-optimal drugs, inadequate or irregular drug supply, unsatisfactory patient or clinician compliance, lack of supervision of treatment and absence of infection control measures in healthcare facilities. As the prevalence of MDRTB is high and yet the cases remain un-isolated in the community we recommend the MOH/NTP and funding agencies to facilitate establishment of MDRTB management centers earlier in Mogadishu in order to treat the MDRTB case otherwise it might Amplify of the incidence of this Emerging Disease.

New Approaches With Natural Product Drugs for Overcoming Multidrug Resistance in Cancer.

Resistance to chemotherapeutic drugs is one of the main obstacles to effective cancer treatment. Multidrug resistance (MDR) is defined as resistance to structurally and/or functionally unrelated drugs, and has been extensively investigated for the last three decades. There are two types of MDR: intrinsic and acquired. Tumor microenvironment selection pressure leads to the development of intrinsic MDR, while acquired resistance is a consequence of the administered chemotherapy. A central issue in chemotherapy failure is the existence of heterogeneous populations of cancer cells within one patient and patient-to-patient variability within each type of cancer. Numerous genes and pathways contribute to the development of MDR in cancer. Point mutations, gene amplification or other genetic or epigenetic changes all affect biological functions and may lead to the occurrence of MDR phenotype. Similar to the characteristics of cancerogenesis, the main features of MDR include abnormal tumor vasculature, regions of hypoxia, aerobic glycolysis, and a lower susceptibility to apoptosis. In order to achieve a lethal effect on cancer cells, drugs need to reach their intracellular target molecules. The overexpression of the efflux transporter P-glycoprotein (P-gp) in MDR cancer cells leads to decreased uptake of the drug and intracellular drug accumulation, minimising drug-target interactions. New agents being or inspired by natural products that successfully target these mechanisms are the main subject of this review. Two key approaches in combating MDR in cancer are discussed (i) finding agents that preserve cytotoxicity toward MDR cancer cells; (ii) developing compounds that restore the cytotoxic activity of classic anticancer drugs.

Inhibition of human 67-kDa laminin receptor sensitizes multidrug resistance colon cancer cell line SW480 for apoptosis induction.

The adhesion mediated drug resistance in cancer cells resulted from adhesion of the extracellular matrix is a major cause for multidrug resistance (MDR) and leads chemotherapeutic failure for colon cancer. In this study, we explored the role of 67-kDa laminin receptor (67LR) in chemotherapeutic drug resistance in colon cancer cells. SiRNA-mediated knockdown of 67LR decreased the cell adhesion when laminins were applied. Moreover, 67LR knockdown increased the expression of pro-apoptotic gene Bax but inhibited the expression of anti-apoptotic gene Bcl-2. Enhanced apoptosis was observed in 67LR siRNA-transfected SW480 cell when the cell was treated with doxorubicin for apoptosis induction. Furthermore, MTT assay revealed that the IC50 of chemotherapeutic toward SW480 cell adhesion to laminins was reduced after 67LR knockdown, indicating there was a significant increase of drug sensitivity in SW480 cell. In conclusion, our study demonstrated that 67LR plays a considerable role in the development of colon cancer MDR.

Multidrug-Resistance Related Long Non-Coding RNA Expression Profile Analysis of Gastric Cancer.

The effect of chemotherapy of gastric cancer (GC) remains very poor because of multidrug resistance (MDR). However, the mechanisms underlying MDR of GC remains far from fully understood. The aim of this study is to illustrate the potential mechanisms of the MDR of GC at mainly the long non-coding RNA (lncRNA) level. In this study, GC cell line, SGC7901, and two MDR sublines, SGC7901/VCR and SGC7901/ADR were subjected to an lncRNA microarray analysis. Bioinformatics and verification experiments were performed to investigate the potential lncRNAs involved in the development of MDR. Pathway analysis indicated that 15 pathways corresponded to down-regulated transcripts and that 20 pathways corresponded to up-regulated transcripts (p-value cut-off is 0.05). GO analysis showed that the highest enriched GOs targeted by up-regulated transcripts were “system development” and the highest esenriched GOs targeted by the down-regulated transcripts were “sterol biosynthetic process”. Our study is the first to interrogate differentially expressed lncRNAs in human GC cell line and MDR sublines and indicates that lncRNAs are worthwhile for further study to be the novel candidate biomarkers for the clinical diagnosis of MDR and potential targets for further therapy.

Abstract 3048: Study of mitochondria in multi-drug resistance and Polyphyllin D anti-cancer effect in hepatocellular carcinoma

Abstract Liver cancer, being the sixth common cancer, causes approximately 700,000 deaths worldwide annually. Major treatment relies on chemotherapies because of the late diagnosis in many cases of liver cancer. However, the results are not satisfactory since the cancer cells develop multi-drug resistance (MDR), which greatly hampers the efficacy of multiple kinds of structurally different drugs, during the course of treatment. Several mechanisms of MDR were identified, the most notable one is the over-expression of ATP-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp) and multi-drug resistance protein 1 (MRP-1), on plasma membrane. These transporters act as efflux pump of various types of chemo-drugs to accentuate the MDR phenotype. Nevertheless, the complete picture of MDR formation is yet to be explored. As mitochondria contribute vitally in apoptosis and energy production, in which both criteria are substantially altered in cancer context, we hypothesized that the organelle also takes part in the development of MDR in liver cancer. In our study, with the support of conventional assays such as western blotting and confocal imaging analysis, we adopted a novel approach by making use of the tunable resistive pulse sensing (TRPS) technique to characterize isolated mitochondria of HepG2 and R-HepG2, which corresponds to the native and multi-drug resistant liver cancer cell lines respectively. We identified a difference in volume and amount of mitochondria present in HepG2 and R-HepG2, plus the expression of P-gp and MRP-1 on mitochondria of R-HepG2. These suggest a potential role of mitochondria in MDR. On the other hand, a drug candidate Polyphyllin D (PD) was found to exert selective potency against R-HepG2. However, the mechanism is not lucid. We investigated the possible participation of mitochondria in this phenomenon and identified PD causes stronger swelling and membrane potential depolarization to isolated mitochondria of R-HepG2. Future attempt in elucidating pathways involved in PD toxicity will bring insight on designing therapeutics against cancer cells with MDR phenotype. This study also suggested future research in mitochondria can aid the discovery of more mechanisms in MDR development. Citation Format: Brandon Ho Ngai, Jacky Fong Chuen Loo, Siu Kai Kong. Study of mitochondria in multi-drug resistance and Polyphyllin D anti-cancer effect in hepatocellular carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3048. doi:10.1158/1538-7445.AM2015-3048

Abstract 4419: Design, synthesis and biological evaluation of N-aryl-3,3,3-trifluoro-2-hydroxy-2-methylpropionamide analog as a promising inhibitor of the multidrug resistance-linked ABCG2 transporter

Abstract Abstract: Despite the current advances in cancer drug discovery, cancer cells often develop resistance to chemotherapeutic agents leading to poor clinical outcomes. The phenomenon of multidrug resistance (MDR) is prevalent among tumor populations; wherein cancer cells are rendered resistant to structurally and mechanistically unrelated drugs. Of the several factors responsible for the development of MDR, the overexpression of ATP-binding cassette (ABC) efflux transporters poses a serious threat towards attaining a successful chemotherapeutic outcome. The second member of the G sub-family of ABC transporters (ABCG2) is one such efflux transporter that renders the cancer cells resistant to several chemotherapeutic drugs, in turn limiting their intracellular accumulation. The blockade of this efflux pump offers a strategic approach towards increasing the efficiency of chemotherapy. Here we demonstrate the biological activity of a novel N-aryl-3,3,3-trifluoro-2-hydroxy-2-methylpropionamide analog, CCTA-1650 that blocks the efflux function of ABCG2 in vitro and in vivo in a preclinical tumor xenograft nude mouse model. Cell cytotoxicity assays performed by combining the chemotherapeutic agents with CCTA-1650 at concentrations of up to 5 μM significantly increased the sensitivity of resistant cancer cells overexpressing both the wild-type and mutant variants of ABCG2. CCTA-1650 inhibits the function of the transporter by decreasing the efflux of substrate chemotherapeutic agents as evident from accumulation and efflux studies with [3H]-mitoxantrone. Furthermore CCTA-1650 at concentrations of up to 5 μM did not affect the expression of ABCG2 transporter upon treatment with CCTA-1650. In addition, CCTA-1650 increased the ATPase activity of ABCG2 in a concentration-dependent manner. CCTA-1650 also displayed inhibition of function of the ABCG2 transporter in an in vivo tumor xenograft nude mouse model. CCTA-1650 at a dose of 30 mg/kg significantly sensitized the resistant tumors to doxorubicin. This effect obtained with combining chemotherapeutic agents with an inhibitor of ABCG2 function both in vitro and in vivo demonstrates the usefulness of CCTA-1650 for the treatment of drug-resistant tumors in the clinic. Citation Format: Atish S. Patel, Tianwen Li, Nagaraju Anreddy, Yufen Zhao, Rishil J. Kathawala, Yijun Wang, Suresh V. Ambudkar, Zhe-Sheng Chen, Changmei Cheng. Design, synthesis and biological evaluation of N-aryl-3,3,3-trifluoro-2-hydroxy-2-methylpropionamide analog as a promising inhibitor of the multidrug resistance-linked ABCG2 transporter. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4419. doi:10.1158/1538-7445.AM2015-4419

Abstract 4422: TTT-28, a newly synthesized thiazole-valine peptide, antagonizes multidrug resistance by inhibiting the efflux activity of the ABCB1 transporter

Abstract Cancer cells often exhibit either intrinsic or acquired resistance to chemotherapy through a phenomenon known as multidrug resistance (MDR). Different mechanisms contribute to the development of MDR, preeminent among them being the accelerated drug efflux mediated by overexpression of ATP-binding cassette (ABC) transporters. Currently, it has been found that some small molecule tyrosine kinase inhibitors (TKIs), such as motesanib, linsitinib, masitinib and nilotinib, were able to modulate the activity of ABC transporters. Thus, the aim of this study was to determine whether TTT-28, a newly synthesized thiazole-valine peptide, could reverse ABCB1-mediated MDR. The results showed that TTT-28 significantly sensitized both ABCB1-transfected and drug-selected cell lines overexpressing this transporter to its substrate anticancer drugs. Using calcein-AM efflux assay, we identified TTT-28 (IC50 = 1.0 μM) carrying 3,4,5-trimethoxybenzoyl and 2-aminobenzophenone groups, respectively, at the amino and carboxyl termini of the monothiazole zwitterion. TTT-28 significantly increased the accumulation of [3H]-paclitaxel in ABCB1 overexpressing cells by blocking the efflux function of ABCB1 transporter. Furthermore, TTT-28 inhibited the photolabeling of ABCB1 with [125I]-iodoarylazidoprazosin with IC50 = 0.75 μM and stimulated the basal ATP hydrolysis of ABCB1 in a concentration-dependent manner (EC50 ATPase = 0.027 μM). Consistent with these findings, biochemical and docking studies showed site-1 to be the preferable binding site for TTT-28 within the drug-binding pocket of human ABCB1. Therefore, we report that TTT-28 antagonizes MDR by inhibiting the efflux activity of the ABCB1 transporter. These findings reveal high clinical values for the co-administration of TTT-28 and ABCB1 substrate chemotherapeutic drugs in cancer patients that overexpress ABCB1 and stimulate further research on circumventing the ABCB1-mediated MDR in cancers. Citation Format: Yi-Jun Wang, Nagaraju Anreddy, Bhargav A. Patel, Eduardo E. Chufan, Satyakam Singh, Guan-Nan Zhang, Yun-Kai Zhang, Anna Maria Barbuti, Suresh V. Ambudkar, Tanaji T. Talele, Zhe-Sheng Chen. TTT-28, a newly synthesized thiazole-valine peptide, antagonizes multidrug resistance by inhibiting the efflux activity of the ABCB1 transporter. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4422. doi:10.1158/1538-7445.AM2015-4422

Autophagy-related genes Raptor, Rictor, and Beclin1 expression and relationship with multidrug resistance in colorectal carcinoma

This study aims to evaluate the relationship between the expressions of autophagy-related genes Raptor, Rictor, and Beclin1 and the expression of multidrug resistance (MDR) gene in colorectal cancer (CRC) patients. Immunohistochemistry and real-time polymerase chain reaction were used to detect the protein and messenger RNA expressions of mammalian target of rapamycin (mTOR), Raptor, Rictor, Beclin1, light chain 3 (LC3), and MDR-1 in 279 CRC specimens. Patients were followed up annually by telephone or at an outpatient clinic. Results revealed that the protein and messenger RNA expressions of Beclin1, LC3, mTOR, Raptor, Rictor, and MDR-1 in CRC are significantly higher than in adjacent tissues. LC3 expression in poorly differentiated CRC is higher than that in well-differentiated CRC, and the expression of mTOR, Raptor, Rictor, and LC3 in lymph node metastasis is higher than that obtained in the absence of lymph node metastasis. The expression of LC3 is positively correlated with those of Beclin1 and Rictor and negatively correlated with Raptor and mTOR in CRC. The expression of Raptor is negatively correlated with Rictor. The expression of MDR-1 is positively correlated with those of Beclin1, LC3, and Rictor and negatively correlated with Raptor and mTOR. Kaplan-Meier analysis revealed that the 5-year survival rate of patients without lymph node metastasis; positive expression of Rictor, Beclin1, and LC3; and negative expression of Raptor and mTOR were higher than those with these characteristics. To conclude, the expressions of Beclin1, Raptor, and Rictor are related to the development and progression of colorectal carcinoma and MDR. ( 2014-009-01.).

Development of Fourth Generation ABC Inhibitors from Natural Products: A Novel Approach to Overcome Cancer Multidrug Resistance

Multidrug resistance (MDR) in cancer caused due to overexpression of ABC drug transporters is a major problem in modern chemotherapy. Molecular investigations on MDR have revealed that the resistance is due to various transport proteins of the ABC superfamily which include Phosphoglycoprotein (P-gp/MDR1/ ABCB1), multidrug resistance-associated protein-1 (MRP1), and the breast cancer resistance protein (BCRP). They have been characterized functionally and are considered as major players in the development of MDR in cancer cells. These ATP-dependent transporter proteins cause MDR either by decreased uptake of the drug or increased efflux of the drug from the target organelles. Several MDR-reversing agents are being developed and are in various stages of clinical trials. The first three generations of ABC modulators such as quinine, verapamil, cyclosporine-A, tariquitor, PSC 833, LY335979, and GF120918 required to be administered in high doses to reverse MDR and were associated with adverse effects. Additionally, these modulators non-selectively inhibit ABC and adversely accumulate chemotherapeutic drugs in brain and kidney. Currently, research has stepped up towards reversing MDR by using natural products which exhibitted potential as chemosensitizers. Globally, there is a rich biodiversity of natural products which can be sourced for developing drugs. These products may provide more lead compounds with superior activity, foremost to the development of more effective therapies for MDR cancer cells. Here, we briefly review the status of natural products for reversing MDR modulators, and discuss the long term goal of MDR strategies in current clinical settings.

Overexpression of long non-coding RNA PVT1 in gastric cancer cells promotes the development of multidrug resistance

BackgroundThe development of multidrug resistance (MDR) is a crucial problem of therapy failure in gastric cancer, which results in disease recurrence and metastasis. Plasmacytoma variant translocation 1 (PVT-1), a long non-coding RNA (lncRNA), was previously found to be increased in gastric cancer patients and regulated the chemotherapy sensitivity in pancreatic cancer cells. However, the role of PVT1 in multidrug resistant Gastric cancer remains largely unexplored. MethodsIn this study, the mRNA levels of PVT1 in gastric cancer tissues of cisplatin-resistant patients and two kinds of cisplatin-resistant cells BGC823/DDP and SGC7901/DDP were detected by qRT-PCR. The influence of PVT1 knockdown or overexpression on anticancer drug resistance was assessed by measuring the cytotoxicity of cisplatin and the rate of apoptosis detected by CCK-8 assay and flow cytometry, respectively. Further, we investigated the expression levels of MDR1, MRP, mTOR and HIF-1α by qRT-PCR and western blotting. ResultsPVT-1 was highly expressed in gastric cancer tissues of cisplatin-resistant patients and cisplatin-resistant cells. In addition, BGC823/DDP and SGC7901/DDP cells transfected with PVT-1 siRNA and treated with cisplatin exhibited significant lower survival rate and high percentage of apoptotic tumor cells. While, PVT1 overexpression exhibit the anti-apoptotic property in BGC823 and SGC7901 cells transfected with LV-PVT1-GFP and treated with cisplatin. Moreover, qRT-PCR and western blotting revealed that PVT1 up-regulation increased the expression of MDR1, MRP, mTOR and HIF-1α. ConclusionsOverexpression of LncRNA PVT1 in gastric carcinoma promotes the development of MDR, suggesting an efficacious target for reversing MDR in gastric cancer therapy.

MiR-218 targets survivin and regulates resistance to chemotherapeutics in breast cancer

Multidrug resistance (MDR) remains one of the most significant obstacles in breast cancer treatment, and this process often involves dysregulation of a great number of microRNAs (miRNAs). Some miRNAs are indicators of drug resistance and confer resistance to chemotherapeutic drugs, although our understanding of this complex process is still incomplete. We have used a combination of miRNA profiling and real-time PCR in two drug-resistant derivatives of MCF-7 and Cal51 cells. Experimental modulation of miR expression has been obtained by retroviral transfection. Taxol and doxorubicin IC50 values were obtained by short-term drug sensitivity assays. Apoptosis was determined by flow cytometry after annexin V staining, by caspase 3/7 and caspase 9 activity assays and the levels of apoptosis-related proteins bcl-2 and bax by real-time PCR and Western blot. miR target was studied using transient transfection of luciferase constructs with the 3' untranslated regions (UTR) of target mRNAs. Small interfering RNA-mediated genetic knock-down was performed in MDR cells and its modulatory effect on apoptosis examined. The effect of miRNA on tumorigenicity and tumor drug response was studied in mouse xenografts. miRNA profiling of two drug-resistant breast cancer cell models indicated that miR-218 was down-regulated in both MCF-7/A02 and CALDOX cells. Ectopic expression of miR-218 resensitized both drug-resistant cell lines to doxorubicin and taxol due to an increase in apoptosis. miR-218 binds survivin (BIRC5) mRNA 3'-UTR and down-regulated reporter luciferase activity. Experimental down-regulation of survivin by RNA interference in drug-resistant cells did mimic the sensitization observed when miRNA-218 was up-regulated. In addition, resensitization to taxol was also observed in mouse tumor xenografts from cells over-expressing miR-218. miR-218 is involved in the development of MDR in breast cancer cells via targeting survivin and leading to evasion of apoptosis. Targeting miR-218 and survivin may thus provide a potential strategy for reversing drug resistance in breast cancer.

NSC23925 prevents the emergence of multidrug resistance in ovarian cancer in vitro and in vivo

ObjectiveThe development of multidrug resistance (MDR) remains the significant clinical challenge in ovarian cancer therapy; however, relatively little is known about how to prevent the emergence of MDR during chemotherapy treatment. NSC23925 previously has been shown to prevent the development of MDR in osteosarcoma cells in vitro. The purpose of this study was to evaluate the effects of NSC23925 on the prevention of MDR in ovarian cancer, especially in vivo. MethodsHuman ovarian cancer cells were treated with paclitaxel alone or in combination with NSC23925 in vitro and in vivo. MDR ovarian cancer cells were established both in cultured cells and mouse models. The expression levels of Pgp and MDR1 were evaluated in various selected cell sublines by Western blot and real-time PCR. Pgp activity was also determined. ResultsPaclitaxel treated cells eventually developed MDR with overexpression of Pgp and MDR1, and with high activity of Pgp, while paclitaxel–NSC23925 co-treated cells remained sensitive to chemotherapeutic agents in both in vitro and in vivo models. There was no observed increase in expression level and activity of Pgp in paclitaxel–NSC23925 co-treated cells. Additionally, there were no changes in the sensitivity to chemotherapeutic agents, nor expression of Pgp, in cells cultured with NSC23925. ConclusionOur findings suggest that NSC23925 can prevent the emergence of MDR in ovarian cancer both in vitro and in vivo. The clinical use of NSC2395 at the onset of chemotherapy may prevent the development of MDR and improve the clinical outcome of patients with ovarian cancer.

α-2,8-Sialyltransferase Is Involved in the Development of Multidrug Resistance via PI3K/Akt Pathway in Human Chronic Myeloid Leukemia.

Cell surface sialylation is emerging as an important feature of cancer cell multidrug resistance (MDR). We have focused on the influence of 2,8-sialyltransferases in key steps of the development of MDR in chronic myeloid leukemia (CML). The expressional profiles of six α-2,8-sialyltransferases were generated in three pairs of CML cell lines and peripheral blood mononuclear cells (PBMC) of CML patients. Cellular MDR phenotype positively correlated with ST8SIA4 and ST8SIA6 levels. Furthermore, ST8SIA4 mediated the activity of phosphoinositide-3 kinase (PI3K)/Akt signal pathway and the expression of P-glycoprotein (P-gp). Targeting the PI3K/Akt pathway by its specific inhibitor LY294002, or by Akt RNA interfering reversed the MDR phenotype of K562/ADR cells. Inhibition of PI3K/Akt pathway also attenuated the effects caused by the overexpression of ST8SIA4 on MDR. Therefore this study indicated that α-2,8-sialyltransferases involved in the development of MDR of CML cells probably through ST8SIA4 regulating the activity of PI3K/Akt signaling and the expression of P-gp.

A critical dose of doxorubicin is required to alter the gene expression profiles in MCF-7 cells acquiring multidrug resistance.

Cellular mechanisms of multidrug resistance (MDR) are related to ABC transporters, apoptosis, antioxidation, drug metabolism, DNA repair and cell proliferation. It remains unclear whether the process of resistance development is programmable. We aimed to study gene expression profiling circumstances in MCF-7 during MDR development. Eleven MCF-7 sublines with incremental doxorubicin resistance were established as a valued tool to study resistance progression. MDR marker P-gp was overexpressed only in cells termed MCF-7/ADR-1024 under the selection dose approaching 1024 nM. MCF-7/ADR-1024 and authentic MCF-7/ADR shared common features in cell morphology and DNA ploidy status. MCF-7/ADR-1024 and authentic MCF-7/ADR down regulated repair genes BRCA1/2 and wild type p53, apoptosis-related gene Bcl-2 and epithelial-mesenchymal transition (EMT) epithelial marker gene E-cadherin. While detoxifying enzymes glutathione-S transferase-π and protein kinase C-α were up-regulated. The genes involving in EMT mesenchymal formation were also overexpressed, including N-cadherin, vimentin and the E-cadherin transcription reppressors Slug, Twist and ZEB1/2. PI3K/AKT inhibitor wortmannin suppressed expression of Slug, Twist and mdr1. Mutant p53 with a deletion at codons 127-133 markedly appeared in MCF-7/ADR-1024 and authentic MCF-7/ADR as well. In addition, MCF-7/ADR-1024 cells exerted CSC-like cell surface marker CD44 high/CD24 low and form mammospheres. Overall, results suggest that resistance marker P-gp arises owing to turn on/off or mutation of the genes involved in DNA repair, apoptosis, detoxifying enzymes, EMT and ABC transporters at a turning point (1.024 μM doxorubicin challenge). Behind this point, no obvious alterations were found in most tested genes. Selection for CSC-like cells under this dose may importantly attribute to propagation of the population presenting invasive properties and drug resistance. We thereby suggest two models in the induction of drug resistance. Model 1: Selection for CSC-like cells. Model 2: Mutations for gain-of resistance. Either model 1 or model 2 requires doxorubicin dose approaching 1 μM to alter gene regulation.