# Stiff matrix promotes lung cancer cell migration through down-regulating the Piezo1 channel expression to facilitate Ca2+-dependent filopodia formation

## TL;DR

Stiff environments help lung cancer cells move by reducing a specific channel's activity, which lowers calcium levels and promotes cell movement structures.

## Contribution

This study reveals a novel mechanism where stiff matrix down-regulates Piezo1 to enhance lung cancer cell migration via calcium and cofilin regulation.

## Key findings

- Stiff substrates promote lung cancer cell migration and filopodia formation.
- Down-regulation of Piezo1 reduces intracellular calcium levels and enhances cofilin phosphorylation.
- Piezo1 inhibition or reduced calcium levels increase cell migration and filopodia formation.

## Abstract

Matrix stiffening profoundly influences cancer cell functions and cancer progression, and the mechanosensitive Piezo1 channel is implicated in these processes. Different from what is observed in most solid tumors, the Piezo1 channel in lung cancer is down-regulated and negatively regulates cancer cell migration, but the underlying mechanism is still unclear. Herein, we investigated the role of Piezo1 channel in matrix stiffness regulation of lung cancer cell migration and the mechanisms in A549 cells growing on polyacrylamide (PA) hydrogels with different stiffness. Compared with soft substrate, stiff substrate promoted cell migration, down-regulated Piezo1 expression, favored filopodia formation, as well as restraining the rise in intracellular calcium concentration ([Ca2+]i). Additionally, blockade or knockdown of Piezo1 channel promoted, whereas its activation suppressed, cell migration and filopodia formation. Furthermore, reducing the [Ca2+]i promoted cell migration and filopodia formation. Finally, stiff substrate induced cofilin phosphorylation, which was enhanced by inhibiting the Piezo1 channel or reducing the [Ca2+]i and, conversely, suppressed by activating the Piezo1 channel. Collectively, our study has revealed that stiff matrix down-regulates the Piezo1 channel expression and thereby restrains the rise in the [Ca2+]i to facilitate cofilin phosphorylation and filopodia formation, leading to an increase in lung cancer cell migration. These findings broaden our understanding of the molecular mechanism by which the Piezo1 channel functions in lung cancer differently from in other cancers.

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