De, S.; Djamgoz, M. B. A.

The plasma membrane voltage (Vm) is well known to have significant involvement in a wide range of cellular functions including cancer progression. Voltage imaging revealed that Vm of MDA-MB-231 breast cancer cells is \'bistable\' with hyperpolarising voltage transients (HVTs). Here, we formulate a model of Vm incorporating the ion channels Nav1.5, Cav3.2, and KCa1.1. Vm is governed by the Hodgkin-Huxley formalism coupled to intracellular Ca2+ dynamics, via Ca2+ influx through Cav3.2 and Ca2+-dependent efflux of K+ through KCa1.1. Stochastic fluctuations--arising from sparse ion channel expression and Ca2+-induced Ca2+ release (CICR)--drive Vm transitions between the otherwise stable depolarised and hyperpolarised states. The model qualitatively reproduces the key experimental observations of HVTs, and their suppression by specific inhibitors of Nav1.5 or KCa1.1. It is predicted that inhibition of CICR should also lead to suppression of HVTs. Our model promises to help the understanding of the dynamic electrical activity of the MDA-MB-231 cell model and its functional consequences, and may inspire future bioelectricity-based cancer diagnosis and therapy.