NON‐CONTACT ELECTRIC FIELDS POTENTLY HINDER EGF PROMOTED BREAST CANCER MOTILITY BY DOWNREGULATING EGFR PHOSPHORYLATION

Abstract

The objective of the proposed study is to assess the therapeutic potential of non‐contact inductive E‐fields (iEFs) in inhibiting breast cancer motility. Normal breast ducts are lined with monolayer of epithelial cells that have asymmetric distribution of ion channels resulting in a charge separation between the luminal and the basal sides giving rise to trans‐epithelial potentials (TEP). These TEPs are responsible for endogenous E‐fields that are directed radially from luminal to basal side. Consequently, the sites of invasion in breast tumors are depolarized, which suggest that that cell migration in late‐stage tumors occurs in absence of endogenous E‐fields. Furthermore, breast cancer cells in‐vitro have been shown to migrate towards the positive electrodes under the influence of externally applied direct current electric fields (1–10 V/cm). Therefore, we hypothesize that E‐fields applied in the direction of migrating breast cancer cells potently inhibit cell motility. To test our hypothesis, we used a panel of three breast cell lines, 1) normal MCF10A, 2) MCF10CA1a(MIV) (a malignant variant of MCF10A cells with H‐Ras mutation), and 3) triple negative breast cancer (TNBC) cells MDA‐MB‐231 in conjunction with a custom Bi‐directional Microtrack Assay (BMA). The BMA consists of an array of parallel‐aligned tracks that measure 700 μm in length and with a cross‐section of 20 μm × 20 μm. These microtracks mimic the topological cues encountered by migrating tumor cells that have detached from the primary tumor site during invasion. Inductive Electric Fields (iEFs ~ 60 μV/cm), which mimic the endogenous E‐fields in the breast duct, were applied using a custom‐designed air‐cored Helmholtz coils. iEFs applied anti‐parallel to the direction of migration and in absence of a pro‐migratory epidermal growth factor (EGF) gradient on cancer cells significantly increased migration speeds (Fig A) but had no effect on the control epithelial cells which maintained their non‐migratory phenotype. In presence of a stable EGF gradient, iEFs applied parallel in the direction of migration significantly reduce migration speeds for both the cancerous cell lines whereas it has no effect on migration speeds of MCF10A cells. Actin aggregation at the leading and/or trailing edges is a characteristic of migratory cells and for cancer cells that showed significant speed reduction the intracellular actin was uniformly distributed (Fig B) rather aggregating on the tips indicating a possible mechanism controlled through the EGFR/EGF pathway. Furthermore, we verified using Western Blotting techniques that iEFs significantly reduced phosphorylation of EGFR in EGF‐treated MDA‐MB‐231 cells (Fig C) whereas they downregulated the expression of EGFR in EGF‐treated MCF10CA1a(MIV) cells. For each case, the protein levels had a one‐to‐one correlation with the migration speeds for each cell line. Moreover, we also found that a combinatorial treatment of MK2206 (Akt inhibitor) with iEFs significantly reduced migration speeds of these breast cancer cells (Fig A) below the level of their respective controls. Thus, iEFs selectively hindered cancer cells with no adverse effects on normal epithelial cells, making them a potential candidate for cancer control and intervention. From a therapeutic standpoint, iEFs may help augment current therapeutic approaches to hinder the metastasis of breast cancer and confer survival benefit, including in TNBC, which currently lack any targeted therapies.Support or Funding InformationFunding for JWS: American Cancer Society and Institute for Materials Research at The Ohio State University. JWS acknowledge support from Pelotonia.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.