Electrophysiological characterisation of ion channel activity in tumour slices

Research output: Contribution to conferenceAbstract

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Conference

ConferenceUK Interdisciplinary Breast Cancer Symposium
CountryUnited Kingdom
CityManchester
Conference date(s)15/01/1816/01/18

Publication details

DatePublished - 15 Jan 2018
Number of pages1
Original languageEnglish

Abstract

Voltage-gated sodium channels (VGSCs) are up-regulated in breast cancer compared to normal breast tissue, and their expression correlates with a worse prognosis. Blocking VGSCs with ranolazine or phenytoin, or knocking down the VGSC pore-forming subunit Nav1.5, reduces tumour growth and metastasis in mouse xenografts. Also, upregulating the VGSC β1 subunit increases tumour growth in mice. The mechanisms by which VGSCs promote metastasis are not yet understood. Cancer cells have a relatively depolarised membrane potential (Vm) compared to normal cells, and Vm can control cell cycle progression and cellular migration. We hypothesise that VGSCs functionally contribute to breast cancer progression by regulating the Vm. We generated tumours by implanting GFP-expressing metastatic MDA-MB-231 cells in the mammary fat pad of gc-/-rag2-/- mice. We took tissue slices from primary tumours and lungs of these mice for electrophysiological recording. We also made slices from human tumour samples from the Breast Cancer Now Tissue Bank. We used whole cell patch clamp recording to measure the ionic currents and Vm from cells within these slices. We found that sodium currents were similar in primary tumours and lung metastases from the mouse model, and that larger sodium currents did not appreciably change the Vm. We compared control MDA-MB-231 xenograft tumours with those in which the VGSC β1 subunit was upregulated. β1 increases the sodium currents of MDA-MB-231 cells in vitro, so we hypothesized that we would find a similar effect in mouse xenografts. However, we found no difference in sodium currents or Vm between the control and β1-overexpressing tumours. Human tissue slices are more difficult to record from than xenograft slices as they are less cellular and of more heterogeneous composition. So far, we have detected outward (likely K+) currents in two human tumours. Our data show that it is possible to take electrophysiological recordings from mouse and human breast tumours to assess ion channel function.

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