Organic Moiety on Sn(IV) Does Matter for In Vitro Mode of Action: nBu3Sn(IV) Compounds with Carboxylato N-Functionalized 2-Quinolones Induce Anoikis-like Cell Death in A375 Cells

<b>Objectives:</b> New tributyltin(IV) complexes containing the carboxylate ligands 3-(4-methyl-2-oxoquinolin-1(2H)-yl)propanoic acid (<b>HL1</b>) and 2-(4-methyl-2-oxoquinolin-1(2H)-yl)acetic acid (<b>HL2</b>) have been synthesized. <b>Methods:</b> Their structures have been determined by elemental microanalysis, FT-IR and multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy and X-ray diffraction study. A solution state NMR analysis reveals a four-coordinated tributyltin(IV) complex in non-polar solvents, while an X-Ray crystallographic analysis confirms a five-coordinated trigonal-bipyramidal geometry around the tin atom due to the formation of 1D chains. A theoretical structural analysis was performed by optimization employing B3LYP-D3BJ functional and 6-311++G(d,p)/def2-TZVP(Sn) basis sets for H, C, N, O/Sn, respectively. The interactions between tin(IV) and surrounding atoms were examined by QTAIM approach. The in vitro antiproliferative activity of the synthesized compounds was evaluated by MTT and CV assays versus MCF-7 (human breast adenocarcinoma), HCT116 (human colorectal carcinoma), A375 (human melanoma), 4T1 (mouse breast carcinoma), CT26 (mouse colon carcinoma) and B16 (mouse melanoma) tumor cell lines. <b>Results:</b> Both synthesized compounds (<b><i>n</i>Bu₃SnL1</b> and <b><i>n</i>Bu₃SnL2</b>) exerted powerful micromolar IC₅₀ cytotoxicity values and demonstrated high selectivity toward malignant cells. Both experimental drugs affected cell adhesion and induced anchorage independent apoptosis, a favorable type of cell death with an essential role in cancer dissemination prevention. The BSA-binding affinity of the obtained organotin compounds was followed by spectrofluorometric titration and molecular docking simulations. <b>Conclusions:</b> The tributyltin(IV) compounds selectively induce anoikis-like cell death in A375 cells, also highlighting the importance of the organic moiety on the tin(IV) ion in the mechanism of action.