Activation of Mechanosensitive Ion Channels Induces Autocrine and Paracrine Networks in Craniocervical Squamous Cell Carcinoma Cell via Endothelin Signaling.

Abstract

Endothelin (ET) is a peptide comprising 21 amino acids, and its G-protein coupled ETA and ETB receptors are expressed in both cancer cells and cancer-associated cells. Cancer cells excessively express ETA and ETB receptors, and mechanical stimulation promotes the growth and migration of these cells. The autocrine and paracrine signaling of ET is involved in several cancer metabolic pathways, but how this is mediated by the ET-axis (ET and its receptors) remains to be clarified. This study investigated ET-axis-mediated autocrine/paracrine communication in rat squamous cell carcinoma (SCC) in response to direct mechanical stimulation of such cells. Intracellular free Ca²⁺ concentration ([Ca²⁺]_i) was determined using fura-2/AM from a rat SCC cell line (SCC-158). Direct mechanical stimulation of the SCC-158 cells using glass micropipettes to compress the cell membrane to 8 μm for 4 sec induced a transient increase in [Ca²⁺]_i. This increase was also observed in the neighboring cells of the stimulated SCC-158 cells. Treatment with 10 μM Gd³⁺ or 1 μM GsMTx4 almost completely inhibited the mechanical stimulation-induced increase in [Ca²⁺]_i in the SCC-158 cells. Application of 1 μM BQ-123 (an ETA receptor antagonist) inhibited the increase in [Ca²⁺]_i in the stimulated SCC-158 and neighboring cells, whereas that of BQ-788 (an ETB receptor antagonist) had no such effect. These findings suggest that rat SCC cells express the Piezo1 channel. Activation of the Piezo1 channel induced endothelin release from the mechanically stimulated SCC-158 cells. Released ET activated ETA receptors in neighboring SCC-158 cells. These findings also suggest that intercellular paracrine communication among SCC-158 cells through ET signaling plays an important role in the development and metabolism of SCC cells.