Electrotaxis of Glioblastoma and Medulloblastoma Spheroidal Aggregates

Abstract

Treatment of neuroepithelial cancers remains a daunting clinical challenge, particularly due to an inability to address rampant invasion deep into eloquent regions of the brain. Given the lack of access, and the dispersed nature of brain tumor cells, we explore the possibility of electric fields inducing directed tumor cell migration. In this study we investigate the properties of populations of brain cancer undergoing electrotaxis, a phenomenon whereby cells are directed to migrate under control of an electrical field. We investigate two cell lines for glioblastoma and medulloblastoma (U87mg & DAOY, respectively), plated as spheroidal aggregates in Matrigel-filled electrotaxis channels, and report opposing electrotactic responses. To further understand electrotactic migration of tumor cells, we performed RNA-sequencing for pathway discovery to identify signaling that is differentially affected by the exposure of direct-current electrical fields. Further, using selective pharmacological inhibition assays, focused on the PI3K/mTOR/AKT signaling axis, we validate whether there is a causal relationship to electrotaxis and these mechanisms of action. We find that U87 mg electrotaxis is abolished under pharmacological inhibition of PI3Kγ, mTOR, AKT and ErbB2 signaling, whereas DAOY cell electrotaxis was not attenuated by these or other pathways evaluated.

Voltage-gated ion channels mediate the electrotaxis of glioblastoma cells in a hybrid PMMA/PDMS microdevice

“…Both T98G cells and U-251MG cells are categorized as mesenchymal type glioblastoma 37,38 , however, their electrotactic responses are completely different. Similar results are reported in the electrotaxis of glioblastoma cells and spheroids 15,16,19,39 and lung adenocarcinoma 51 , showing that although molecular and surface marker makeups of the cell lines are similar, their electrotaxis responses can be completely different. The opposite electrotaxis results may reflect the fundamental heterogeneity among glioblastoma cells which has been speculated to contribute to the recurrence and therapeutic resistance after anti-tumor therapy [52][53][54][55][56] .…”

“…A weak endogenous electric current has been shown to serve as a guidance cue for neuroblast migration from the subventricular zone in mouse 13 , a region speculated as the origin of glioma tumorigenesis 14 . Thus, the physiological a) amy.shen@oist.jp electric fields in the brain may play an important role in mediating the glioma tumorigenesis and invasion [15][16][17][18][19] . Cells sense the electric field by bioelectrical activation of voltage-sensitive proteins, mechanosensing due to electrokinetic phenomena, or activated chemical signaling due to electrokinetically polarized membrane receptors ( Supplementary FIG.…”

Glioblastoma Cell Migration is Directed by Electrical Signals

“…Recently, Lyon and colleagues identified putative electrotactic signalling pathways with transciptomic analyses in differentiated U87MG spheroid aggregates, and subsequently finding PI3K, Akt, mTOR, ErbB2, ErbB3, Src/Abl, but not MEK, HGF/VEGF, ROCK1/2 inhibition attenuates cathodal migration [49]. However, PI3K inhibition with LY294002 did not affect cathodal migration, although BEZ235 abolished directed migration, which may be non-specifically accrued to its duel activity on PI3K/mTOR and more efficient downregulation of Akt [49,50]. addition to anti-proliferative, pro-differentiation of GSC and pro-apoptotic effects reported previously [52].…”

Hub Proteins Involved in RAW 264.7 Macrophages Exposed to Direct Current Electric Field

“…A series of studies have been performed on the effect of dcEFs on cell gene expression. With the help of various devices, researchers have applied various types of current stimulation to cells, including the human adult dermal fibroblast cell line (HDF-a) (dcEF: 100 mV/mm, 1 h) [47], human adult epidermal keratinocytes (dcEF: 100 mV/mm, 1 h) [48], the human lung cancer cell line (CL1-5) (dcEF: 300 mV/mm, 2 h) [49], the human glioblastoma cell line (U87 mg), and the medulloblastoma cell line (DAOY) (dcEF: 250 mV/mm, 8 h) [50]. The results of gene expression profiling have shown that the expression characteristics of genes in cells are so diverse that we could not find a common gene that was regulated in all these studies.…”

“…In 2015, a dcEF (100-400 mV/mm, 2 h) was applied to NIH 3T3 fibroblasts in order to investigate the correlation between ROS production and EF-induced cell migration [52]. In addition, the human lung cancer cell line (CL1-5) (dcEF: 300 mV/mm, 2 h) [49], the human glioblastoma cell line (U87 mg), and the medulloblastoma cell line (DAOY) (dcEF: 250 mV/mm, 8 h) were used to study the effect of electric field stimulation on cellular gene expression [50].…”