| Popis: |
Bioelectricity represents endogenous electrical signaling via ion channels and pumps at the plasma membrane, which shapes unique patterns of voltage potentials across the membranes. Resting membrane potential (Vm) is a functional determinant of cell behaviour. There is a functional relationship between resting membrane potential (Vm) and cell proliferation and differentiation, which can be seen in many cells including normal stem cells and various tumors. Sundelacruz et al have shown that Vm depolarization promotes maintenance of mesenchymal stem cells in an undifferentiated stage. We postulated that depolarized Vm may also help to maintain a population of cancer stem cells (CSCs) in undifferentiated, but highly invasive state. Cancer stem cells (CSCs) represent a subpopulation of cancer cells responsible for tumor formation, relapse and metastasis. The breast CSC model used in this study consists of cells with up-regulated Twist expression (HMLETwist), which are showing markers of CSCs and have functional CSC properties. Therefore, Vm was measured by Nystatin-perforated Patch-Clamp method in a breast CSC model. Also, we measured Vm of SUM159 and MCF7, two breast cancer cell lines with high and low percentage of CSCs among whole population, respectively. Furthermore, we used proprietary potassium ionophores, previously shown to be highly cytotoxic for breast CSC model cells, to modulate membrane potential. Membrane potential after treatment with compounds was estimated using the cationic dye DioC6(3). It was indeed shown that SUM 159 cells are more depolarized than MCF7. Regarding breast CSC model, there was no difference in Vm between HMLEtwist and control HMLE cells, pointing to potential limitations of this model. Two highly cytotoxic proprietary potassium ionophores modulated membrane potential in breast CSC model. Although related by structure, one depolarized, while other hyperpolaryzed cells. Compound 613 causes severe depolarization in HMLEtwist cells. Electrophysiological measurements pointed that compound at first hyperpolarizes cells, which is followed by depolarization. Mode of action of both compounds is under investigation. Measurements of resting potential in CSCs with and without modulators will be further investigated. |
