K_Ca3.1 (IK) modulates pancreatic cancer cell migration, invasion and proliferation: anomalous effects on TRAM-34

In the recent decades, ion channels became the focus of cancer biologists, as many channels are overexpressed in tumour tissue and functionally they are linked to abnormal cell behaviour with processes including apoptosis, chemo- and radioresistance, proliferation and migration. K_Ca3.1 is a Ca²⁺-activated K⁺ channel that plays a central role in tumour progression in many cancer types. Therefore, the aim of the present study was to investigate K_Ca3.1 expression in pancreatic cancer cells and assess possible implications to disease progression. Using qPCR technique, we found abundant expression of K_Ca3.1 in pancreatic cancer cell lines. Patch clamp measurements on MiaPaCa-2 cells revealed a Ca²⁺-activated K⁺ current that matched biophysical characteristics as described for K_Ca3.1. Moreover, the current was sensitive to the commonly used channel modulators TRAM-34, clotrimazole and DC-EBIO, and it was abolished following transient gene knockdown of K_Ca3.1. We utilized both pharmacology and RNAi to assess a possible role of the channel in tumour cell behaviour. We found that the channel supported MiaPaCa-2 cell proliferation. Using RNAi protocols, we also identified K_Ca3.1 as important entity in cell invasion. However, TRAM-34 had unexpected stimulatory effects on cell migration and invasion estimated in various assays. Moreover, TRAM-34 increased intracellular Ca²⁺. In conclusion, we found prominent functional expression of K_Ca3.1 in pancreatic cancer cells. We provide evidence that the channel has a key role in cell proliferation and for the first time identify K_Ca3.1 as important entity in PDAC cell migration. We further reveal anomalous effects of TRAM-34.