Structure elucidation and quantification of the reduction products of anticancer Pt(iv) prodrugs by electrochemistry/mass spectrometry (EC-MS).

Pt(iv) prodrugs are a class of promising anticancer agents, which are activated by reduction to the active Pt(ii) species. Consequently, the reduction process is a crucial parameter. Herein, a new approach using electrochemistry (EC) coupled to liquid chromatography (LC) and electrospray ionization-mass spectrometry (ESI-MS) or inductively coupled plasma (ICP)-MS was applied. This enabled getting insights into the differences in the reduction and ligand release of platinum(iv) complexes with varying equatorial core structures.

Multi-scale imaging of anticancer platinum(iv) compounds in murine tumor and kidney.

Nano-scale secondary ion mass spectrometry (NanoSIMS) enables trace element and isotope analyses with high spatial resolution. This unique capability has recently been exploited in several studies analyzing the subcellular distribution of Au and Pt anticancer compounds. However, these studies were restricted to cell culture systems. To explore the applicability to the in vivo setting, we developed a combined imaging approach consisting of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), NanoSIMS and transmission electron microscopy (TEM) suitable for multi-scale detection of the platinum distribution in tissues. Applying this approach to kidney and tumor samples upon administration of selected platinum(iv) anticancer prodrugs revealed uneven platinum distributions on both the organ and subcellular scales. Spatial platinum accumulation patterns were quantitatively assessed by LA-ICP-MS in histologically heterogeneous organs (e.g., higher platinum accumulation in kidney cortex than in medulla) and used to select regions of interest for subcellular-scale imaging with NanoSIMS. These analyses revealed cytoplasmic sulfur-rich organelles accumulating platinum in both kidney and malignant cells. Those in the tumor were subsequently identified as organelles of lysosomal origin, demonstrating the potential of the combinatorial approach for investigating therapeutically relevant drug concentrations on a submicrometer scale.

Triapine-mediated ABCB1 induction via PKC induces widespread therapy unresponsiveness but is not underlying acquired triapine resistance.

Although triapine is promising for treatment of advanced leukemia, it failed against solid tumors due to widely unknown reasons. To address this issue, a new triapine-resistant cell line (SW480/tria) was generated by drug selection and investigated in this study. Notably, SW480/tria cells displayed broad cross-resistance against several known ABCB1 substrates due to high ABCB1 levels (induced by promoter hypomethylation). However, ABCB1 inhibition did not re-sensitize SW480/tria cells to triapine and subsequent analysis revealed that triapine is only a weak ABCB1 substrate without significant interaction with the ABCB1 transport function. Interestingly, in chemo-naive, parental SW480 cells short-time (24 h) treatment with triapine stimulated ABCB1 expression. These effects were based on activation of protein kinase C (PKC), a known response to cellular stress. In accordance, SW480/tria cells were characterized by elevated levels of PKC. Together, this led to the conclusion that increased ABCB1 expression is not the major mechanism of triapine resistance in SW480/tria cells. In contrast, increased ABCB1 expression was found to be a consequence of triapine stress-induced PKC activation. These data are especially of importance when considering the choice of chemotherapeutics for combination with triapine.

Enhanced anticancer activity and circumvention of resistance mechanisms by novel polymeric/ phospholipidic nanocarriers of doxorubicin.

Severe toxic side effects and drug resistance are the major limitations of doxorubicin (Dox), one of the most potent anticancer agents in clinical use. Nanocarrier preparations offer the opportunity to overcome these drawbacks, which is reflected in the clinical approval of two liposomal Dox preparations. Additionally, there are many attempts to enhance the activity of Dox against multi-drug resistant (MDR) cancer cells. However, most of these strategies resulted in the increased uptake of Dox in resistant cells, only, while it remained unchanged in chemo-sensitive cells. Here, we present a new polymeric-phospholipidic hybrid delivery system which distinctly enhanced the accumulation and activity of Dox in all tested cancer cell lines including several MDR cell models. Notably, the resistance levels against Dox were reduced from about 6-fold to about 2-fold. Moreover, the new nanocarriers were shown to rapidly (within 10 min) and effectively transport Dox into resistant as well as sensitive cancer cells. Consequently, treatment with the new Dox-containing nanocarriers resulted in effective cell cycle arrest in G2/M phase and ROS-induced cell death induction. Finally, the new nanocarriers were tested against NK/Ly lymphoma and L1210 leukemia cells in vivo. In both cell models, the nanoformulation of Dox resulted in 100% cured animals already at low concentrations (0.1 mg/kg), while free Dox solely extended survival time. This indicates that the incorporation of phospholipids into PEGylated polymeric nanocarriers is a promising strategy to enhance efficacy and reduce toxicity of Dox treatment against both sensitive and resistant cancer models in vitro and in vivo.

Nanoformulation improves activity of the (pre)clinical anticancer ruthenium complex KP1019.

Ruthenium anticancer drugs belong to the most promising non-platinum anticancer metal compounds in clinical evaluation. However, although the clinical results are promising regarding both activity and very low adverse effects, the clinical application is currently hampered by the limited solubility and stability of the drug in aqueous solution. Here, we present a new nanoparticle formulation based on polymer-based micelles loaded with the anticancer lead ruthenium compound KP1019. Nanoprepared KP1019 was characterised by enhanced stability in aqueous solutions. Moreover, the nanoparticle formulation facilitated cellular accumulation of KP1019 (determined by ICP-MS measurements) resulting in significantly lowered IC50 values. With regard to the mode of action, increased cell cycle arrest in G2/M phase (PI-staining), DNA damage (Comet assay) as well as enhanced levels of apoptotic cell death (caspase 7 and PARP cleavage) were found in HCT116 cells treated with the new nanoformulation of KP1019. Summarizing, we present for the first time evidence that nanoformulation is a feasible strategy for improving the stability as well as activity of experimental anticancer ruthenium compounds.