Pancreatic cancer is a malignancy with high mortality and steeply rising incidence. A major contributor to poor outcomes is its frequent late detection in the metastatic phase of the disease. The treatment of pancreatic cancer remains challenging and often ineffective, making the development of new compounds targeting novel molecular targets crucial. One promising target is the Kv1.3 ion channel, which is associated with chronic inflammation and cancer progression. Inhibition of Kv1.3 on the inner mitochondrial membrane induces apoptosis in cancer cells, since cancer cells generally exhibit a higher (more negative) mitochondrial membrane potential compared to healthy cells. This property enables targeted delivery of compounds with lipophilic cationic chemical groups for mitochondrial targeting (MTM). Among these, the triphenylphosphonium cation is considered the gold standard; however, its conjugates with lipophilic compounds non-specifically inhibit mitochondrial function independently of Kv1.3 inhibition, which could lead to adverse effects.
At the Faculty of Pharmacy, colleagues therefore developed two new MTMs based on pyridine, which were conjugated via a linker to psoralen, resulting in two new inhibitors of mitochondrial Kv1.3 (compounds EID-58 and EID-63). The aim of this master’s thesis was to evaluate their uptake into mitochondria and their effects on cell survival and cell death in pancreatic ductal adenocarcinoma COLO-357 cells, in comparison with a known psoralen-based inhibitor of mitochondrial Kv1.3 containing triphenylphosphonium as the MTM (PAPTP, compound EID-6). Additionally, their effects on the mitochondrial respiration were investigated. The effects of the Kv1.3 inhibitors bearing the new MTMs were also compared with those of their decyl analogues, used as model conjugates of the new MTMs with an otherwise inert cargo of comparable lipophilicity (compounds EID-111 and EID-112), in order to distinguish specific effects due to Kv1.3 inhibition from non-specific inhibitory effects of lipophilic conjugates bearing the new MTMs.
We found that the total cellular uptake of both Kv1.3 inhibitors with the new MTMs strongly depends on the mitochondrial membrane potential, indicating their substantial mitochondrial accumulation. The fraction of mitochondrial membrane potential dependent uptake for EID-63, and especially EID-58, was significantly lower than that of EID-6, which is consistent with their lower potency in cell viability and cell death assays. Nevertheless, both Kv1.3 inhibitors with the new MTMs reduced cell viability and induced apoptosis, inhibiting cell survival at significantly lower concentrations compared to their decyl analogues. Both the new Kv1.3 inhibitors and their decyl analogues strongly inhibited mitochondrial respiration; however, unlike EID-6, they did not exhibit an observable uncoupling effect. The new MTMs thus effectively deliver Kv1.3 inhibitors to mitochondria but also exert a strong inhibitory effect on mitochondria and their respiration, necessitating further study.
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