Quantifiable and Inexpensive Cell-Free Fluorescent Method to Confirm the Ability of Novel Compounds to Chelate Iron.

Cancer cells require large amounts of iron to maintain their proliferation. Iron metabolism is considered a hallmark of cancer, making iron a valid target for anti-cancer approaches. The development of novel compounds and the identification of leads for further modification requires that proof of mechanism assays be carried out. There are many assays to evaluate the impact on proliferation; however, the ability to chelate iron is an important and sometimes overlooked end-point measure due to the high costs of equipment and the challenge to quickly and reproducibly quantify the strength of chelation. Here, we describe a quantifiable and inexpensive cell-free fluorescent method to confirm the ability of novel compounds to chelate iron. Our assay relies on the commercially available inexpensive fluorescent dye Calcein, whose fluorescence can be quantified on most fluorescent microtiter plate readers. Calcein is a weak iron chelator, and its fluorescence is quenched when it binds Fe2+/3+; fluorescence is restored when a novel chelator outcompetes Calcein for bound Fe2+/3+. The removal of fluorescent quenching and the resulting increase in fluorescence allows the chelation ability of a novel putative chelator to be determined. Therefore, we offer an inexpensive, high-throughput assay that allows the rapid screening of novel candidate chelator compounds.

Novel Iron Chelator SK4 Drives Cytotoxicity through Inhibiting Mitochondrial Metabolism in Ovarian and Triple Negative Breast Cancer Cell Lines.

Anti-cancer therapy by iron chelation has been shown to inhibit many cellular processes including DNA replication, mitochondrial metabolism and oncogenic signalling pathways (e.g., EGFR). Iron chelator SK4 represents a double pronged approach towards treating cancer. SK4 enters through LAT1, a commonly overexpressed amino acid transporter in tumours, thus targeting iron addiction and LAT1 overexpression. The aim of this study was to characterise the mode of action of SK4 through proteomics, metabolomics, lipidomics and seahorse real-time analysis in ovarian cell line SKOV3 and triple negative breast cancer cell line MDA MB 231. Pathway enrichment of proteomics data showed an overrepresentation of metabolism related pathways. Metabolic change after SK4 exposure have been confirmed in investigations of changes in basal and maximal mitochondrial respiration using seahorse real-time analysis of mitochondrial metabolism. Metabolomics also showed an increase in AMP and glucose-1-phosphate. Interestingly, our lipidomics data show a decrease in phospholipid synthesis in the SKOV3 cells which is in contrast with previous data which showed an upregulation of ceramide driven apoptosis. In summary, our data highlight impairment of energy metabolism as a mechanism of action underlying SK4 apoptosis, but also suggest a potential role of ceramide induction in the phenotypic outcome of the cell model.

Circadian rhythm gene regulation in the housefly Musca domestica.

The circadian mechanism appears remarkably conserved between Drosophila and mammals, with basic underlying negative and positive feedback loops, cycling gene products, and temporally regulated nuclear transport involving a few key proteins. One of these negative regulators is PERIOD, which in Drosophila shows very similar temporal and spatial regulation to TIMELESS. Surprisingly, we observe that in the housefly, Musca domestica, PER does not cycle in Western blots of head extracts, in contrast to the TIM protein. Furthermore, immunocytochemical (ICC) localization using enzymatic staining procedures reveals that PER is not localized to the nucleus of any neurons within the brain at any circadian time, as recently observed for several nondipteran insects. However, with confocal analysis, immunofluorescence reveals a very different picture and provides an initial comparison of PER/TIM-containing cells in Musca and Drosophila, which shows some significant differences, but many similarities. Thus, even in closely related Diptera, there is considerable evolutionary flexibility in the number and spatial organization of clock cells and, indeed, in the expression patterns of clock products in these cells, although the underlying framework is similar.