Effects of a combretastatin A4 analogous chalcone and its Pt-complex on cancer cells: A comparative study of uptake, cell cycle and damage to cellular compartments.

The combretastatin A4 analogous chalcone (2E)-3-(3-hydroxy-4-methoxyphenyl)-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one 1 and its dichloridoplatinum(II) (6-aminomethylnicotinate) complex 2 were previously found to be highly active against a variety of cancer cell lines while differing in their apoptosis induction and long-term regrowth retardation (Schobert et al. [1]). Further differences were identified now. The cellular uptake of complex 2, like that of oxaliplatin, occurred mainly via organic cation transporters (OCT-1/2; ∼32%) and copper transporter related proteins (Ctr1; ∼24%), whereas that of chalcone 1 was dependent on endocytosis (∼80%). Complex 2 was more tumour-specific than 1 concerning neural cells. This was apparent from the ratios of IC(50)(48h) values against primary astrocytes versus human glioma cells U87 (>7000 for complex 2; 55 for compound 1). In tubulin-rich neurons and 518A2 melanoma cells complex 2 disrupted microtubules and actin filaments. Cancer cells treated with 2 could repair the cytoskeletal damage but ceased to proliferate and perished. Complex 2 was particularly cytotoxic against P-gp-rich cells. It acted as a substrate for ABC-transporters of types BCRP, MRP3, and MRP1 and so was less active against the corresponding cancer cell lines. Complex 2 arrested the cell cycle of the melanoma cells in G(1) and G(2)/M phases. A fragmentation of their Golgi apparatus was observed by TEM for incubation with complex 2 but not with 1. In conclusion, unlike chalcone 1, its platinum complex 2 is highly cell line specific, is taken up via cell-controlled transporters and induces apoptosis by triggering multiple targets.