The peptidic β-lactone proteasome inhibitors (PIs) cystargolides A and B were used to conduct structure-activity relationship (SAR) studies in order to assess their anticancer potential. A total of 24 different analogs were designed, synthesized and ...
The peptidic β-lactone proteasome inhibitors (PIs) cystargolides A and B were used to conduct structure-activity relationship (SAR) studies in order to assess their anticancer potential. A total of 24 different analogs were designed, synthesized and evaluated for proteasome inhibition, for cytotoxicity towards several cancer cell lines, and for their ability to enter intact cells. X-ray crystallographic analysis and subunit selectivity was used to determine the specific subunit binding associated with the structural modification of the β-lactone (P 1 ), peptidic core, (P x and P y ), and end-cap (P z ) of our scaffold. The cystargolide derivative 5k, structurally unique at both P y and P 1 , exhibited the most promising inhibitory activity for the β5 subunit of human proteasomes (IC 50 = 3.1 nM) and significant cytotoxicity towards MCF-7 (IC 50 = 416 nM), MDA-MB-231 (IC 50 = 74 nM) and RPMI 8226 (IC 50 = 41 nM) cancer cell lines. Cellular infiltration assays revealed that minor structural modifications have significant effects on the ability of our PIs to inhibit intracellular proteasomes, and we identified 5k as a promising candidate for continued therapeutic studies. Our novel drug lead 5k is a more potent proteasome inhibitor than carfilzomib with mid-to-low nanomolar IC 50 measurements and it is cytotoxic against multiple cancer cell lines at levels approaching those of carfilzomib.
Organizational Affiliation:
Department of Biology, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA.,Department of Chemistry, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA.,Department of Chemistry, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA; Department of Biology, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA.,Department of Chemistry, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA. Electronic address: rodolfo.tello-aburto@nmt.edu.,Center for Integrated Protein Science at the Department Chemie, Technische Universitat München, Lichtenbergstraße 4, 85748 Garching, Germany.
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