Multidrug resistance (MDR) is a common problem when fighting cancer with chemotherapy. P-glycoprotein (P-gp, or MDR1) is an active pump responsible for the efflux of xenobiotics out of the cell, including anti-cancer drugs. It is a validated target against MDR. No crystal structure of the human P-gp is available to date, and only recently several cryo-EM structures have been solved. In this paper, we present a comprehensive computational approach that includes constructing the full-length three-dimensional structure of the human P-gp and its refinement using molecular dynamics. We assessed its flexibility and conformational diversity, compiling a dynamical ensemble that was used to dock a set of lignan compounds, previously reported as active P-gp inhibitors, and disclose their binding modes. Based on the statistical analysis of the docking results, we selected a system for performing the structure-based virtual screening of new potential P-gp inhibitors. We tested the method on a library of 87 natural flavonoids described in the literature, and 10 of those were experimentally assayed. The results reproduced the theoretical predictions only partially due to various possible factors. However, at least two of the predicted natural flavonoids were demonstrated to be effective P-gp inhibitors. They were able to increase the accumulation of doxorubicin inside the human promyelocytic leukemia HL60/MDR cells overexpressing P-gp and potentiate the antiproliferative activity of this anti-cancer drug.

• Keywords
• P-glycoprotein, flavonoids, molecular docking, molecular dynamics, multidrug resistance, natural compounds, structure-based virtual screening,
• Publication type
• Journal Article MeSH

Tumor suppressor p53 is mutated in about 50% of cancers. Most malignant melanomas carry wild-type p53, but p53 activity is often inhibited due to overexpression of its negative regulators Mdm2 or MdmX. We performed high throughput screening of 2448 compounds on A375 cells carrying p53 activity luciferase reporter construct to reveal compounds that promote p53 activity in melanoma. Albendazole and fenbendazole, two approved and commonly used benzimidazole anthelmintics, stimulated p53 activity and were selected for further studies. The protein levels of p53 and p21 increased upon the treatment with albendazole and fenbendazole, indicating activation of the p53-p21 pathway, while the levels of Mdm2 and MdmX decreased in melanoma and breast cancer cells overexpressing these proteins. We also observed a reduction of cell viability and changes of cellular morphology corresponding to mitotic catastrophe, i.e., G2/M cell cycle arrest of large multinucleated cells with disrupted microtubules. In summary, we established a new tool for testing the impact of small molecule compounds on the activity of p53 and used it to identify the action of benzimidazoles in melanoma cells. The drugs promoted the stability and transcriptional activity of wild-type p53 via downregulation of its negative regulators Mdm2 and MdmX in cells overexpressing these proteins. The results indicate the potential for repurposing the benzimidazole anthelmintics for the treatment of cancers overexpressing p53 negative regulators.

• Keywords
• Mdm2, MdmX, benzimidazoles, drug repurposing, melanoma, p53,
• MeSH
• Albendazole pharmacology   MeSH
• Benzimidazoles pharmacology   MeSH
• Down-Regulation MeSH
• Fenbendazole pharmacology   MeSH
• Nuclear Proteins metabolism   MeSH
• Humans MeSH
• Melanoma drug therapy   metabolism   MeSH
• MCF-7 Cells MeSH
• Cell Line, Tumor MeSH
• Tumor Suppressor Protein p53 metabolism   MeSH
• Drug Repositioning MeSH
• Cell Proliferation drug effects   MeSH
• Cell Cycle Proteins MeSH
• Proto-Oncogene Proteins c-mdm2 metabolism   MeSH
• Proto-Oncogene Proteins metabolism   MeSH
• Gene Expression Regulation, Neoplastic drug effects   MeSH
• High-Throughput Screening Assays MeSH
• Drug Screening Assays, Antitumor MeSH
• Cell Survival drug effects   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Albendazole MeSH
• Benzimidazoles MeSH
• Fenbendazole MeSH
• Nuclear Proteins MeSH
• MDM2 protein, human MeSH Browser
• MDM4 protein, human MeSH Browser
• Tumor Suppressor Protein p53 MeSH
• Cell Cycle Proteins MeSH
• Proto-Oncogene Proteins c-mdm2 MeSH
• Proto-Oncogene Proteins MeSH
• TP53 protein, human MeSH Browser

Escherichia albertii is a recently discovered species with a limited number of well characterized strains. The aim of this study was to characterize four of the E. albertii strains, which were among 41 identified Escherichia strains isolated from the feces of living animals on James Ross Island, Antarctica, and Isla Magdalena, Patagonia. Sequencing of 16S rDNA, automated ribotyping, and rep-PCR were used to identify the four E. albertii isolates. Phylogenetic analyses based on multi-locus sequence typing showed these isolates to be genetically most similar to the members of E. albertii phylogroup G3. These isolates encoded several virulence factors including those, which are characteristic of E. albertii (cytolethal distending toxin and intimin) as well as bacteriocin determinants that typically have a very low prevalence in E. coli strains (D, E7). Moreover, E. albertii protein extracts caused cell cycle arrest in human cell line A375, probably because of cytolethal distending toxin activity.

• Keywords
• Antarctica, Escherichia albertii, bacteriocins, cytolethal distending toxin,
• MeSH
• Charadriiformes microbiology   MeSH
• Escherichia genetics   isolation & purification   metabolism   MeSH
• Feces microbiology   MeSH
• Multilocus Sequence Typing veterinary   MeSH
• Polymerase Chain Reaction veterinary   MeSH
• Electrophoresis, Gel, Pulsed-Field veterinary   MeSH
• Ribotyping veterinary   MeSH
• RNA, Ribosomal, 16S genetics   MeSH
• Spheniscidae microbiology   MeSH
• Seals, Earless microbiology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Antarctic Regions MeSH
• Chile MeSH
• Names of Substances
• RNA, Ribosomal, 16S MeSH