In Vitro Evaluation of Antiproliferative Properties of Novel Organotin(IV) Carboxylate Compounds with Propanoic Acid Derivatives on a Panel of Human Cancer Cell Lines

Abstract

The synthesis of novel triphenyltin(IV) compounds, Ph₃SnLn (n = 1-3), with oxaprozin (3-(4,5-diphenyloxazol-2-yl)propanoic acid), HL1, and the new propanoic acid derivatives 3-(4,5-bis(4-methoxylphenyl)oxazol-2-yl)propanoic acid, HL2, and 3-(2,5-dioxo-4,4-diphenylimidazolidin-1-yl)propanoic acid, HL3, has been performed. The ligands represent commercial drugs or their derivatives and the tin complexes have been characterized by standard analytical methods. The in vitro antiproliferative activity of both ligands and organotin(IV) compounds has been evaluated on the following tumour cell lines: human prostate cancer (PC-3), human colorectal adenocarcinoma (HT-29), breast cancer (MCF-7), and hepatocellular cancer (HepG2), as well as on normal mouse embryonic fibroblast cells (NIH3T3) with the aid of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-12 diphenyltetrazolium bromide) and CV (crystal violet) assays. Contrary to the inactive ligand precursors, all organotin(IV) carboxylates showed very good activity with IC₅₀ values ranging from 0.100 to 0.758 µM. According to the CV assay (IC₅₀ = 0.218 ± 0.025 µM), complex Ph₃SnL1 demonstrated the highest cytotoxicity against the caspase 3 deficient MCF-7 cell line. Inductively coupled plasma mass spectrometry (ICP-MS) analysis indicated a two-fold lower concentration of tin in MCF-7 cells in comparison to platinum. To investigate the mechanism of action of the compound Ph₃SnL1 on MCF-7 cells, morphological, autophagy and cell cycle analysis, as well as the activation of caspase and ROS/RNS and NO production, has been performed. Results suggest that Ph₃SnL1 induces caspase-independent apoptosis in MCF-7 cells.

Keywords: ICP-MS; apoptosis; breast cancer; cytotoxicity; triphenyltin(IV).

Scheme 1

Synthesis of compounds Ph₃SnL1, HL2, Ph₃SnL2, HL3 and Ph₃SnL3.

Scheme 1

Synthesis of compounds Ph₃SnL1, HL2, Ph₃SnL2, HL3 and Ph₃SnL3.

Figure 1

Platinum and tin uptake in treated MCF-7 cells with cisplatin (at IC₅₀ = 15.83 µM) and Ph₃SnL1 (at IC₅₀ = 0.218 µM) after 24 h of action.

Figure 2

Fluorescent micrographs of MCF-7 cells. (A,F)—control (untreated cells), (B,G)—cisplatin (IC₅₀), (C,H)—cisplatin (2 × IC₅₀), (D,I)—Ph₃SnL1 (IC₅₀), (E,J)—Ph₃SnL1 (2 × IC₅₀); AO = acridine orange; DAPI = 4′,6-diamidino-2-phenylindole.

Figure 3

Flow cytometry results: (a)—caspase activation (apostat), (b)—autophagy (AO).

Figure 4

Effects of Ph₃SnL1 and cisplatin on cell cycle phase distribution: MCF-7 cells were exposed to IC₅₀ doses for 48 h.

Figure 5

Flow cytometry results: (a)—ROS/RNS activation (DHR), (b)—NO activation (DAF-FM).