Aromatic 2-(thio)ureidocarboxylic acids as a new family of modulators of multidrug resistance-associated protein 1: synthesis, biological evaluation, and structure-activity relationships.

Four series of aromatic carboxylic acids were prepared with a urea or thiourea moiety at the neighboring position to the carboxyl group and benzene or thiophene as aromatic scaffold. Using a calcein AM assay, these compounds were evaluated as inhibitors of multidrug resistance-associated protein 1 (MRP1) and selected compounds were examined toward P-glycoprotein (P-gp) as well as breast cancer resistance protein (BCRP) to assess selectivity for MRP1. Two 2-thioureidobenzo[b]thiophene-3-carboxylic acids (48, 49) were identified as particularly potent inhibitors of MRP1, with IC50 values of around 1 microM.

Phenylnannolones A-C: biosynthesis of new secondary metabolites from the myxobacterium Nannocystis exedens.

Myxobacteria are gliding bacteria that belong to the delta-Proteobacteria and are known for their unique biosynthetic capabilities. Among myxobacteria, Nannocystis spp. are most closely related to marine myxobacteria and their secondary metabolism has hardly been investigated.

A 4-aminobenzoic acid derivative as novel lead for selective inhibitors of multidrug resistance-associated proteins.

We present a novel lead for inhibitors of multidrug resistance-associated proteins (MRPs). Compound 1 (4-[(5,6,7,8-tetrahydro-4-oxo-4H-[1]benzothieno[2,3-d][1,3]thiazin-2-yl)amino]benzoic acid) was about six times more potent than the known inhibitor MK571 at MRP1, while at MRP2 its effect was similar to that of MK571. Structural analogs were also evaluated.

Relevance of drug uptake and efflux for cisplatin sensitivity of tumor cells.

Platinum sensitivity and platinum resistance may involve altered activity of transport proteins. In order to assess the role of drug uptake and efflux in this phenomenon, we compared the expression of three copper transporters, intracellular platinum accumulation, DNA platination and cytotoxicity of cisplatin in two cisplatin-sensitive and -resistant tumor cell line pairs (ovarian A2780/A2780cis and cervical HeLa/HeLaCK cells). Gene expression of importer CTR1, and ATP7A and ATP7B efflux transporters (with and without cisplatin treatment) was investigated using quantitative real-time PCR and platinum concentrations were determined by flameless atomic absorption spectrometry.