Multidrug resistance in the chronic lymphoproliferative disorders

Role and Regulation of Hepatobiliary ATP-Binding Cassette Transporters during Chemical-Induced Liver Injury

Severity of drug-induced liver injury (DILI) ranges from mild, asymptomatic, and transient elevations in liver function tests to irreversible liver damage, often needing transplantation. Traditionally, DILI is classified mechanistically as high-frequency intrinsic DILI, commonly dose dependent or DILI that rarely occurs and is idiosyncratic in nature. This latter form is not dose dependent and has a pattern of histopathological manifestation that is not always uniform. Currently, a third type of DILI called indirect hepatotoxicity has been described that is associated with the pharmacological action of the drug. Historically, DILI was primarily linked to drug metabolism events; however, the impact of transporter-mediated rates of drug uptake and excretion has gained greater prominence in DILI research. This review provides a comprehensive view of the major findings from studies examining the contribution of hepatic ATP-binding cassette transporters as key contributors to DILI and how changes in their expression and function influence the development, severity, and overall toxicity outcome. SIGNIFICANCE STATEMENT: Drug-induced liver injury (DILI) continues to be a focal point in drug development research. ATP-binding cassette (ABC) transporters have emerged as important determinants of drug detoxification, disposition, and safety. This review article provides a comprehensive analysis of the literature addressing: (a) the role of hepatic ABC transporters in DILI, (b) the influence of genetic mutations in ABC transporters on DILI, and (c) new areas of research emphasis, such as the influence of the gut microbiota and epigenetic regulation, on ABC transporters.

Effects of ABCB1 rs1045642 polymorphisms on the efficacy and safety of amlodipine therapy in Caucasian patients with stage I-II hypertension

PURPOSE

The aim of this study was to determine the impact of ABCB1 (MDR1) rs1045642 polymorphisms on the efficacy and safety of amlodipine in Caucasian patients.

PATIENTS AND METHODS

The 12-week study included 100 patients. Patients with the newly diagnosed stage I-II hypertension (HT) were recruited to complete genotyping of the rs1045642 single-nucleotide polymorphism (SNP). The study design did not include a control group. Before treatment, all patients either did not undergo antihypertensive treatment at all or did not receive regular antihypertensive therapy. The initial dose was 5 mg/day. Four office blood pressure measurements, two 24-hour noninvasive ambulatory blood pressure measurements, and questionnaires of Tsvetov were used to evaluate the efficacy and safety of amlodipine.

RESULTS AND CONCLUSION

The highest antihypertensive effect in combination with the lowest incidence of adverse reactions was observed in the TT group, while patients with the CC genotype showed a low antihypertensive effect and the highest incidence of adverse effects. Patients with the CC genotype presented with adverse effects predominantly in the form of edema. A total of 33 patients reached the target blood pressure (SBP <140 mmHg; DBP <90 mmHg): two patients with the CC genotype (12%); 18 patients with the CT genotype (34%); and 13 patients with the TT genotype (43%). The intergroup differences were: CC vs CT, P=0.02; CC vs TT, P=0.02; and CT vs TT, P=0.05. The results of this study indicate the potential of pharmacogenetic testing for rs1045642 SNP when prescribing amlodipine for the first time in Caucasian patients with stage I-II arterial HT.

Co-expression of ATP binding cassette transporters is associated with poor prognosis in acute myeloid leukemia

Chemotherapy failure remains a challenge when treating patients with acute myeloid leukemia (AML), who often suffer from persistent or relapsed disease. The multidrug resistance (MDR) mediated by efflux transporters of the ATP binding cassette (ABC) superfamily is a major obstacle for successful chemotherapy. The present study aimed to elucidate whether the expression of ABC transporters was associated with prognostic factors and responses to chemotherapy in patients with AML, with particular focus on whether co-expression of multiple ABC transporters resulted in a worse prognosis. In the present study, the mRNA expression levels of ABC transporters ABCB1, ABCB4, ABCC1, ABCC4 and ABCG2 in bone marrow (BM) mononuclear cell (MNC) samples from 96 de novo patients with AML and in the peripheral blood (PB) MNC samples from 22 normal individuals were investigated using reverse transcription-quantitative polymerase chain reaction analysis. It was revealed that ABCB1, ABCC1, ABCC4 and ABCG2 were expressed at higher levels in patients with AML compared with normal individuals, whereas ABCB4 had a lower expression level. The expression of ABCB4 in patients with AML was significantly lower than in normal individuals (P<0.001). Patients risk status was associated with ABCB1 (P=0.037), ABCC1 (P=0.047), ABCC4 (P=0.015) and ABCG2 (P=0.027). The 4 genes were expressed a significantly higher levels in the poor response group compared with the good response group (ABCB1, P=0.014; ABCC1, P=0.021; ABCC4, P=0.005; ABCG2, P=0.009). The overexpression of the 4 ABC transporters and the complete remission rate were inversely correlated (P<0.001). These results suggest that the co-expression of multiple ABC transporters may contribute to a worse prognosis in AML.

Annexin A5 as a potential marker in tumors

Annexin A5 (Anxa5) promotes pancreatic adenocarcinoma, sarcoma, tumorigenesis and progression of breast cancer and prostate cancer stem cells. It is involved with metastasis, invasion and development of squamous cell carcinoma, and facilitates nodal progression of bladder cancer and angiogenesis and progression of glioma. Anxa5 de-regulation is associated with drug resistance in nasopharyngeal carcinoma and gastric cancer. Although Anxa5 protein up-regulation promotes cervical cancer progression, it is markedly suppressed in cervical carcinoma cells. Anxa5 is negatively correlated with thyroid cancer malignancy. In this review, we explore the mechanisms of Anxa5 action in tumors. Anxa5 could be a predictive biomarker for tumor development, metastasis and invasion, and be of diagnostic, prognostic and therapeutic significance in cancer.

Identification of proteins interacting with multidrug resistance protein in gastric cancer

AIM: To identify proteins interacting with multidrug resistance protein (MRP) in gastric cancer cells and to evaluate their effect on tumor cell drug resistance.

METHODS: Proteins interacting with MRP were identified using immunoprecipitation and mass spectrometry. Of the proteins identified, Annexin A5 was chosen to further study its role in drug resistance of gastric cancer cells. The expression of MRP and Annexin A5 protein in SGC-7901cells and drug-resistant cell line SGC-7901/DDP was evaluated by Western blot.The impact of Annexin A5 knockdown on MRP expression and drug resistance of gastric cancer cells was evaluated using siRNA interference technology.

RESULTS: In total, 14 proteins interacting with MRP were identified. The protein expression of MRP and Annexin A5 in drug-resistant cell line SGC-7901/DDP was higher than that in SGC-7901 cell line. SiRNA-mediated silencing of the Annexin A5 gene in SGC-7901/DDP cells down-regulated the expression of MRP. The expression of Annexin A5 showed no significant difference between SGC-7901 cells and SGC-7901/DDP cells transfected with Annexin A5-specific siRNA. In addition, siRNA-mediated silencing of the Annexin A5 gene significantly reduced the IC₅₀ values of cisplatin, paclitaxel and 5-Fu in gastric cancer cells, and increased cell sensitivity to these drugs by 36, 17 and 4 folds, respectively.

CONCLUSION: Annexin A5 is a MRP-interacting protein that may be related with tumor drug resistance in gastric cancer.

Association between P-glycoprotein and lymphoid antigen expression on myeloblasts versus therapy response and survival in de novo acute myeloid leukemia: long-term follow-up results

P-glycoprotein (PGP) over-expression on malignant cells is associated with poor prognosis and treatment outcome due to the development of a multidrug resistance phenotype. In this study, we analyzed the correlation between expression of PGP and lymphoid antigens (Ly) on leukemic myeloblasts versus response to therapy and survival in acute myeloid leukemia (AML). Fifty-one consecutive patients, aged 16-75 (median age 44.6 years), diagnosed with de novo AML between 1997 and 2000, and who received at least one induction chemotherapy course, were enrolled in the study. Expression of PGP on ≥ 10% of the myeloblasts (PGP(+)AML) at the time of diagnosis was observed in 21 patients (41%). The complete remission rate did not differ between PGP(+) (13/21) and PGP(-) (20/30) patients (62 vs. 67%). Twelve of the 51 patients (24%) were still alive after a median follow-up time of 11.5 years (range 10.7-13.1). The Ly(+)AML patients showed significantly better overall survival compared with Ly(-)AML patients (8/18 vs. 4/33 patients alive at the last follow-up, P = 0.003). The subgroup of patients with co-expression of PGP and Ly also showed better overall survival compared with PGP(+)AML patients without Ly expression (4/8 vs. 0/13 patients alive at the last follow-up; P = 0.04). Our results suggest that expression of lymphoid antigens on PGP(+) myeloblasts in AML can positively affect survival in AML patients, mainly due to a decreased relapse risk and better survival. Although the small number of patient may be perceived as a limitation of the study, the long follow-up period strengthens its value. Further prospective trials are needed to obtain more information concerning the association between PGP and lymphoid antigens in AML, which would put our results in their ultimate proper context.

Enhanced invasiveness in multidrug resistant leukemic cells is associated with overexpression of P-glycoprotein and cellular inhibitor of apoptosis protein

Multidrug resistance (MDR) and multi-organ infiltration are the major obstacles to the successful treatment of leukemia. It is known that the drug efflux protein, P-glycoprotein (P-gp), and inhibitors of apoptosis proteins (IAPs) are involved in the MDR of leukemic cells, but their roles in leukemia infiltration have not been clearly elucidated. In this study, leukemic cell lines K562 and HL60 and their MDR variants K562R and HL60R have been used to analyze their infiltrative ability. MDR variants display enhanced invasion compared with parental cells. Results from xenografts in SCID (severe combined immunodeficiancy) mice are consistent with these in vitro observations. Furthermore, P-gp and cIAP are overexpressed and co-localize with protein kinase C-ε (PKC-ε) in MDR variants. Our study shows that overexpression of P-gp and cIAP may enhance the infiltration of leukemic cells.