Six novel compounds of platinum(II) with pyrazole derivatives PtPz1–PtPz6 were synthesised and characterised (PtPz1 - [Pt2N-hydroksymethyl-3,5-dimethylpyrazole4(berenil)2]Cl4; PtPz2 - [Pt23,5-dimethylpyrazole4(berenil)2]Cl4; PtPz3 - [Pt23,4-dimethylpyrazole4(berenil)2]Cl4; PtPz4 - [Pt2pyrazole4(berenil)2]Cl4; PtPz5- [Pt25-methylpyrazole4(berenil)2]Cl4; PtPz6 - [Pt2N-ethylpyrazole4(berenil)2]Cl4). The cytotoxic activity of these complexes against MCF-7 and MDA-MB-231 breast cancer cell lines was determined using the MTT assay. Evaluation of apoptosis induction was done with the Annexin V-fluorescein isothiocyanate/propidium iodide assay. In addition, using a flow cytometer, we determined the influence of test compounds on the cell cycle and caspase-3, -8, and -9 activity. The obtained results of caspase activity were confirmed by cell imaging. Moreover, using the flow cytometer, the effects of the test compounds on mitochondrial potential change were assessed. The test results showed that novel pyrazole-platinum(II) complexes exhibited stronger anti-proliferative activity against two breast cancer cell lines than reference cisplatin. Compounds PtPz1, PtPz2, and PtPz3 with methyl substituents at the pyrazole ring showed stronger activity than pyrazole or ethylpyrazole containing complexes. Studies have shown that inhibition of cell survival occurs by arresting the G1 cell cycle and inducing apoptosis. Our analysis associated with the response of MCF-7 and MDA-MB-231 cells to treatment with PtPz1–PtPz6 showed that it leads the cells through the external and intrinsic (mitochondrial) apoptotic pathway via indirect DNA damage.

Novel transition metal complexes (Au, Pd, Pt) with berenil and 2-(1-methyl-5-nitroimidazol-2-yl)ethanol were obtained through two-step synthesis. The cytotoxicity assay against MCF-7 and MDA-MB-231 breast cancer cells revealed that novel platinum and palladium complexes cause a reduction on the viability of MCF-7 and MDA-MB-231 breast cancer cells to a greater extent than cisplatin. The complexes showed lower cytotoxicity on normal MCF-10A human breast epithelial cells than on tumor cells. Furthermore, we observed that these complexes selectively concentrate in tumor cell mitochondria due to the characteristic for these cells increased membrane potential that may explain their increased proapoptotic activity. The activity of the synthesized compounds against topoisomerase type IIα and their increased impact on DNA defragmentation also were documented. The novel complexes also induced autophagosome changes and inhibited tumor growth in xenograft models (established using breast cancer cells).

This study investigates the effect of three new platinum complexes: Pt2(2,4-dimethylpyridine)4(berenil)2 (Pt14), Pt2(3,4-dimethylpyridine)4(berenil)2 (Pt15) and Pt2(3,5-dimethylpyridine)4(berenil)2 (Pt16) on growth and viability of breast cancer cells and their putative mechanism(s) of cytotoxicity. Cytotoxicity was measured with MTT assay and inhibition of [3H]thymidine incorporation into DNA in both breast cancer cells. Results revealed that Pt14-Pt16 exhibit substantially greater cytotoxicity than cisplatin against MCF-7 and MDA-MB-231 breast cancer cells. In the case of human skin fibroblast cell, cytotoxicity assays demonstrated that these compounds are less toxic to normal cells than cisplatin. In addition, the effects of Pt14-Pt16 are investigated using the flow cytometry assessment of annexin V binding, analysis of mitochondrial potential, markers of apoptosis such as caspase-3, caspase-8, caspase-9, caspase-10 and defragmentation of DNA by TUNEL assay. These results indicate that Pt14-Pt16 induce apoptosis by the mitochondrial and external pathway.

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New strategy of cancer’s targeting treatment is combining monoclonal antibodies with chemotherapeutic agents. An important goal of targeted therapy appears to be a transmembrane glycoprotein type I—mucin 1 (MUC1), which is overexpressed in tumors of epithelial origin, especially in breast cancer. The goal of the study was to check the effect of monoclonal antibody against MUC1 with novel platinum(II) complex (Pt12) on selected aspects of apoptosis in human MDA-MB-231 breast cancer cells. The number of apoptotic and necrotic cells was measured using annexin V binding assay. The decrease of mitochondrial membrane potential (MMP) and DNA fragmentation was analyzed. Finally, the influence of novel platinum(II) complex (Pt12) used with anti-MUC1 on the concentration of selected markers of apoptosis such as Bax, caspase-8, -9, and caspase-3 was performed using ELISA. The results from combined treatment were compared with those obtained using monotherapy. In our study, we proved that anti-MUC1 used in combination with Pt12 strongly induced apoptosis in MDA-MB-231 breast cancer cell line. The effect was stronger than treatment with Pt12, cisplatin, anti-MUC1, and anti-MUC1 used with cisplatin. We also observed the highest decrease of MMP and the strongest DNA fragmentation after such a combined treatment. The results obtained from ELISA showed increased concentration of Bax, caspases-8, -9, -3 compared to monotherapy. Our study proved that Pt12 together with anti-MUC1 strongly induced apoptosis in estrogen-negative breast cancer cell line (MDA-MB-231). The apoptosis may go through extrinsic pathway associated with caspase-8 as well as intrinsic pathway connected with caspase-9.