Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Cancer and Leukemia Group B conducted a phase 3 trial of the P-glycoprotein modulator PSC-833 in untreated acute myeloid leukemia patients aged 60 years and older. Patients were randomized to 1 of 2 regimens, with doses determined in a prior phase 1 study, consisting of cytarabine 100 mg/m(2)/d by 7-day infusion, with daunorubicin 60 mg/m(2) and etoposide 100 mg/m(2) daily for 3 days (ADE), or daunorubicin 40 mg/m(2) and etoposide 60 mg/m(2) for 3 days with PSC-833, 2.8 mg/kg over 2 hours, and then 10 mg/kg/d by 3-day infusion (ADEP). The ADEP arm was closed after randomization of 120 patients (61 to ADE and 59 to ADEP) because of excessive early mortality. Rates of complete remission, nonresponse, and death were 46%, 34%, and 20% for ADE, versus 39%, 17%, and 44% for ADEP (P =.008). Nevertheless, disease-free survival (median 7 vs 8 months; P =.38) and overall survival (approximately 33% alive at 1 year) did not differ and were similar to historical results. Although the number of patients was limited, ADE patients whose pretreatment cells exhibited PSC-833-modulated dye efflux in vitro (n = 22) had worse outcomes than those without efflux (n = 11) (complete remission, nonresponse, and death rates of 41%, 41%, and 18%, compared with 91%, 9%, and 0%; P =.03), but with ADEP outcomes were nearly identical. Moreover, for patients with PSC-833-modulated efflux, median disease-free survival was 5 months with ADE and 14 months with ADEP (P =.07). Further modulation trials in older patients must await the design of less-toxic regimens.
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PMID:Phase 3 study of the multidrug resistance modulator PSC-833 in previously untreated patients 60 years of age and older with acute myeloid leukemia: Cancer and Leukemia Group B Study 9720. 1214 2

ATP-binding cassette (ABC) transporters represent one of the largest families of proteins, and transport a variety of substrates ranging from ions to amphipathic anticancer drugs. The functional unit of an ABC transporter is comprised of two transmembrane domains and two cytoplasmic ABC ATPase domains. The energy of the binding and hydrolysis of ATP is used to transport the substrates across membranes. An ABC domain consists of conserved regions, the Walker A and B motifs, the signature (or C) region and the D, H and Q loops. We recently described the A-loop (Aromatic residue interacting with the Adenine ring of ATP), a highly conserved aromatic residue approximately 25 amino acids upstream of the Walker A motif that is essential for ATP-binding. Here, we review the mutational analysis of this subdomain in human P-glycoprotein as well as homology modeling, structural and data mining studies that provide evidence for a functional role of the A-loop in ATP-binding in most members of the superfamily of ABC transporters.
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PMID:The A-loop, a novel conserved aromatic acid subdomain upstream of the Walker A motif in ABC transporters, is critical for ATP binding. 1641 22

Cancer and Leukemia Group B 19808 (CALGB 19808) is the only randomized trial of a second-generation P-glycoprotein (Pgp) modulator in untreated patients with acute myeloid leukemia (AML) younger than age 60 years. We randomly assigned 302 patients to receive induction chemotherapy regimens consisting of cytosine arabinoside (Ara-C; A), daunorubicin (D), and etoposide (E), without (ADE) or with (ADEP) PSC-833 (P). The incidence of complete remission was 75% with both regimens. Reversible grade 3 and 4 liver and mucosal toxicities were significantly more common with ADEP. Therapy-related mortality was 7% and did not differ by induction arm. Excess cardiotoxicity was not seen with high doses of D in ADE. The median disease-free survival was 1.34 years in the ADE arm and 1.09 years in the ADEP arm (P = .74, log-rank test); the median overall survival was 1.86 years in the ADE arm and 1.69 years in the ADEP arm (P = .82). There was no evidence of a treatment difference within any identifiable patient subgroup. Inhibition of Pgp-mediated drug efflux by PSC-833 did not improve clinical outcomes in younger patients with untreated AML. This trial was registered at www.clinicaltrials.gov as #NCT00006363.
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PMID:P-glycoprotein inhibition using valspodar (PSC-833) does not improve outcomes for patients younger than age 60 years with newly diagnosed acute myeloid leukemia: Cancer and Leukemia Group B study 19808. 2052 9

Adenine triphosphate (ATP)-binding cassette (ABC) transporter proteins, such as ABCB1/P-glycoprotein (P-gp) and ABCG2/breast cancer resistance protein (BCRP), transport various structurally unrelated compounds out of cells. ABCG2/BCRP is referred to as a "half-type" ABC transporter, functioning as a homodimer, and transports anticancer agents such as irinotecan, 7-ethyl-10-hydroxycamptothecin (SN-38), gefitinib, imatinib, methotrexate, and mitoxantrone from cells. The expression of ABCG2/BCRP can confer a multidrug-resistant phenotype on cancer cells and affect drug absorption, distribution, metabolism, and excretion in normal tissues, thus modulating the in vivo efficacy of chemotherapeutic agents. Clarification of the substrate preferences and structural relationships of ABCG2/BCRP is essential for our understanding of the molecular mechanisms underlying its effects in vivo during chemotherapy. Its single-nucleotide polymorphisms are also involved in determining the efficacy of chemotherapeutics, and those that reduce the functional activity of ABCG2/BCRP might be associated with unexpected adverse effects from normal doses of anticancer drugs that are ABCG2/BCRP substrates. Importantly, many recently developed molecular-targeted cancer drugs, such as the tyrosine kinase inhisbitors, imatinib mesylate, gefitinib, and others, can also interact with ABCG2/BCRP. Both functional single-nucleotide polymorphisms and inhibitory agents of ABCG2/BCRP modulate the in vivo pharmacokinetics and pharmacodynamics of these molecular cancer treatments, so the pharmacogenetics of ABCG2/BCRP is an important consideration in the application of molecular-targeted chemotherapies.
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PMID:Human ABC transporter ABCG2/BCRP expression in chemoresistance: basic and clinical perspectives for molecular cancer therapeutics. 2452 96