Retracted: Studies of proteasome inhibition and antitumor activity by novel amino acid-polypyridine-copper complexes

Five innovative ternary copper (II) complexes [Cu (OH-PIP)(Phe)Cl]( 1 ), [Cu (OH-PIP)(Gly)(H 2 O)]NO 3 ·2H 2 O ( 2 ), [Cu (OH-PIP)(Ala)(Cl)]·H 2 O ( 3 ), [Cu (OH-PIP)(Met)]PF 6 ·2H 2 O ( 4 ), and [Cu (OH-PIP)(Gln)(H 2 O)]Cl·3H 2 O ( 5 ) have been synthesized and characterized by infrared spectroscopy, elemental analysis, and single crystal X-ray diffraction analysis. X-ray crystallography showed that all Cu atoms were five-coordinated in a square-pyramidal configuration. They are screened for in vitro cytotoxicity against a panel of human cancer cell lines CAL-51, MDA-MB-231, HeLa, MCF-7, SGC-7901, A549, K562, and SMMC-7721. The most promising results were achieved for complexes 1 to 5 , with the IC 50 values in the range of 0.082μM to 0.69μM (against CAL-51 cell lines). The anticancer activities against CAL-51, MDA-MB-231, and MCF-7 were higher than that of Carboplatin. The mechanism studies showed that complexes 1 to 5 could inhibit proteasome activity, induce apoptosis, and inhibit cell proliferation, indicating their great potential as proteasome inhibitors for triple-negative breast cancer therapy.