New phosphorus ylide palladacyclic: Synthesis, characterization, X-Ray crystal structure, biomolecular interaction studies, molecular docking and in vitro cytotoxicity evaluations

Binuclear palladacycles with ionisable and non-ionisable tethers as anticancer agents

The search for novel anticancer agents to replace the current platinum-based treatments remains an ongoing process. Palladacycles have shown excellent promise as demonstrated by our previous work which yielded BTC2, a binuclear palladadycle with a non-ionisable polyethylene glycol (PEG) tether. Here, we explore the importance of the PEG-tether length on the anticancer activity of the binuclear palladacycles by comparing three analogous binuclear palladacycles, BTC2, BTC5 and BTC6, in the oestrogen receptor positive MCF7 and triple-negative MDA-MB-231 breast cancer cell lines. In addition, these are compared to another analogue with an ionisable morpholine tether, BTC7. Potent anticancer activity was revealed through cell viability studies (MTT assays) revealed that while BTC6 showed similar potent anticancer activity as BTC2, it was less toxic towards non-cancerous cell lines. Interestingly, BTC7 and BTCF were less potent than the PEGylated palladacycles but showed significantly improved selectivity towards the triple-negative breast cancer cells. Cell death analysis showed that BTC7 and BTCF significantly induced apoptosis in both the cancer cell lines while the PEGylated complexes induced both apoptosis and secondary necrosis. Furthermore, experimental and computational DNA binding studies indicated partial intercalation and groove binding as the modes of action for the PEGylated palladacycles. Similarly, experimental and computational BSA binding studies indicated and specific binding sites in BSA dependent on the nature of the tethers on the complexes.

Mechanistic insights into the anti-cancer activity of the PEGylated binuclear palladacycle, BTC2, against triple-negative breast cancer

Triple-negative breast cancer (TNBC) has a low five-year survival rate, especially if the cancer is diagnosed at a late stage and has already metastasized beyond the breast tissue. Current chemotherapeutic options for TNBC rely on traditional platinum-containing drugs like cisplatin, oxaliplatin and carboplatin. Unfortunately, these drugs are indiscriminately toxic, resulting in severe side effects and the development of drug resistance. Palladium compounds have shown to be viable alternatives to platinum complexes since they are less toxic and have displayed selectivity towards the TNBC cell lines. Here we report the design, synthesis, and characterization of a series of binuclear benzylidene palladacycles with varying phosphine bridging ligands. From this series we have identified BTC2 to be more soluble (28.38-56.77 μg/mL) and less toxic than its predecessor, AJ5, while maintaining its anticancer properties (IC₅₀ (MDA-MB-231) = 0.58 ± 0.012 μM). To complement the previous cell death pathway study of BTC2, we investigated the DNA and BSA binding properties of BTC2 through various spectroscopic and electrophoretic techniques, as well as molecular docking studies. We demonstrate that BTC2 displays multimodal DNA binding properties as both a partial intercalator and groove binder, with the latter being the predominant mode of action. BTC2 was also able to quench the fluorescence of BSA, thereby suggesting that the compound could be transported by albumin in mammalian cells. Molecular docking studies revealed that BTC2 is a major groove binder and binds preferentially to subdomain IIB of BSA. This study provides insight into the influence of the ligands on the activity of the binuclear palladacycles and provides much needed information on the mechanisms through which these complexes elicit their potent anticancer activity.

Experimental and theoretical studies of Palladium-hydrazide complexes' interaction with DNA and BSA, in vitro cytotoxicity activity and plasmid cleavage ability

New palladium complexes with general formula trans-[Pd(L)₂(OAc)₂] (1,2), (L = Benzhydrazide and 2-Furoic hydrazide) have been synthesized and characterized with various methods including elemental analysis, FT-IR, ¹HNMR and mass spectroscopy. Afterward their interactions with bovine serum albumin and calf thymus deoxyribonucleic acid have been investigated by UV-vis absorption, fluorescence emission and circular dichroism spectroscopy. Also, site-selective replacement experiments with site probes have been carried out. Analysis of fluorescence spectrum indicated static quenching mechanism. Spectroscopic measurements for DNA binding showed the groove binding to DNA for both complexes. Furthermore, cytotoxicity studies of complexes and cis-platin have been done against colon carcinoma (CT26) and breast cancer (4T1) cell lines. Evaluation of complexes (1) and (2) on induction of apoptosis in CT26 cells has been done. Finally, plasmid cleavage ability of (1) and (2) was investigated by gel electrophoresis that indicate the more activity of (1) than (2).

Human CD133-positive hematopoietic progenitor cells enhance the malignancy of breast cancer cells

BACKGROUND

Human CD133+ hematopoietic progenitor cells (HPCs) are a specific subset of cells that can regulate tumor malignancy. However, the mechanism by which CD133+ HPCs affect the malignancy of human breast cancer has not been reported.

METHODS

CD133+ HPCs were isolated and purified from human umbilical cord blood (UCB). We used in vitro culture of MCF-7 and MDA-MB-231 cell lines, and MCF-7 and MDA-MB-231 cells in nude mice to evaluate whether CD133+ HPCs affected the apoptosis, proliferation, invasion and epithelial mesenchymal transition EMT of breast cancer cells.

RESULTS

Co-culture with CD133+ HPCs, but not UCB CD133- cells, promoted the proliferation of human breast cancer MCF-7 and MDA-MB-231 cells, accompanied by reducing in vitro spontaneous apoptosis. Co-administration of these two lines with CD133+ HPCs significantly enhanced the growth of implanted breast cancer in vivo. Furthermore, co-culture with CD133+ HPCs, enhanced the invasion of breast cancer cells, N-cadherin and Vimentin expression, but reduced E-cadherin expression in breast cancer cells.

CONCLUSIONS

Our study demonstrated that CD133+ HPCs enhance the malignancy of breast cancer cells by attenuating spontaneous apoptosis and promoting the process of epithelial mesenchymal transition. These findings may provide new insights into the role of human CD133+ HPCs in breast cancer pathogenesis. Therefore, CD133+ HPCs may be a new therapeutic target for inhibiting the progression of breast cancer.

Characterization of binding interaction of triclosan and bovine serum albumin

Triclosan (TCS) is widely used in personal care products and acts as an antibacterial agent. Residues of TCS may have potential effects on the human health. In this article, the interaction between TCS and bovine serum albumin (BSA) has been characterized by using multi-spectroscopic approaches and molecular docking method under physiological conditions. Thermodynamic investigations revealed that TCS spontaneously bound to a binding site of BSA and hydrogen bonds played a dominant role in this process. The site marker competition experiments indicated that TCS bound at site II (subdomain IIIA) of BSA, which was well substantiated by molecular docking. The binding of TCS further led to changes of conformation and microenvironment of BSA. This work explored the interaction of TCS with BSA, which might be beneficial for evaluating the binding mechanism of other environmental pollutant at molecular level.

Synthesis, characterization, DNA/BSA interactions and in vitro cytotoxicity study of palladium(II) complexes of hispolon derivatives

Thirteen novel palladium(II) complexes of the general formula [Pd(bipy)(O,O'-dkt)](PF₆), (where bipy is 2,2'-bipyridine and O,O'-dkt is β-diketonate ligand hispolon or its derivative) have been prepared through a metal-ligand coordination method that involves spontaneous formation of the corresponding diketonate scaffold. The obtained palladium(II) complexes have been characterized by NMR spectroscopy, ESI-mass spectrometry as well as elemental analysis. The cytotoxicity analysis indicates that most of the obtained palladium(II) complexes show promising growth inhibition in three human cancer cell lines. Flow cytometry analysis shows complex 3e could promote intracellular reactive oxygen species (ROS) accumulation and lead cancer cell death. And the suppression of ROS accumulation and the rescue of cell viability in HeLa cells by N-acetyl-L-cysteine (NAC) suggest the possible link between the increase in ROS generation and cytotoxicity of complex 3e. Flow cytometry analysis also reveal that complex 3e cause cell cycle arrest in the G2/M phase and collapse of the mitochondrial membrane potential, promote the generation of ROS and lead to tumor cell apoptosis. The interactions of complex 3e with calf thymus DNA (CT-DNA) have been evaluated by UV-Vis spectroscopy, fluorescence quenching experiments and viscosity measurements, which reveal that the complex interact with CT-DNA through minor groove binding and/or electrostatic interactions. Further, the results of fluorescence titration and site marker competitive experiment on bovine serum albumin (BSA) suggest that complex 3e can quench the fluorescence of BSA via a static quenching process and bind to BSA in Sudlow's site II.