Lysosome trafficking is necessary for EGF-driven invasion and is regulated by p38 MAPK and Na+/H+ exchangers

Samantha S Dykes,Joshua J Steffan,James A Cardelli

doi:10.1186/s12885-017-3660-3

Abstract

BackgroundTumor invasion through a basement membrane is one of the earliest steps in metastasis, and growth factors, such as Epidermal Growth Factor (EGF) and Hepatocyte Growth Factor (HGF), stimulate this process in a majority of solid tumors. Basement membrane breakdown is one of the hallmarks of invasion; therefore, tumor cells secrete a variety of proteases to aid in this process, including lysosomal proteases. Previous studies demonstrated that peripheral lysosome distribution coincides with the release of lysosomal cathepsins.MethodsImmunofluorescence microscopy, western blot, and 2D and 3D cell culture techniques were performed to evaluate the effects of EGF on lysosome trafficking and cell motility and invasion.ResultsEGF-mediated lysosome trafficking, protease secretion, and invasion is regulated by the activity of p38 mitogen activated protein kinase (MAPK) and sodium hydrogen exchangers (NHEs). Interestingly, EGF stimulates anterograde lysosome trafficking through a different mechanism than previously reported for HGF, suggesting that there are redundant signaling pathways that control lysosome positioning and trafficking in tumor cells.ConclusionsThese data suggest that EGF stimulation induces peripheral (anterograde) lysosome trafficking, which is critical for EGF-mediated invasion and protease release, through the activation of p38 MAPK and NHEs. Taken together, this report demonstrates that anterograde lysosome trafficking is necessary for EGF-mediated tumor invasion and begins to characterize the molecular mechanisms required for EGF-stimulated lysosome trafficking.

Highlights

Tumor invasion through a basement membrane is one of the earliest steps in metastasis, and growth factors, such as Epidermal Growth Factor (EGF) and Hepatocyte Growth Factor (HGF), stimulate this process in a majority of solid tumors
Since many solid tumors exhibit Epidermal growth factor receptor (EGFR)-driven growth independent of c-Met activation, this study investigates the role of EGF/EGFR signaling in anterograde lysosome trafficking
Only p38 inhibition, and not inhibition of PI3K/AKT or MEK/extracellular signal-regulated kinase (ERK), blocked EGFmediated cell scattering. This suggests that HGF/c-Met and EGF/EGFR regulate cell motility via different downstream pathways and that p38 mitogen activated protein kinase (MAPK) activity is necessary for EGF/EGFR-mediated scattering

Summary

Introduction

Tumor invasion through a basement membrane is one of the earliest steps in metastasis, and growth factors, such as Epidermal Growth Factor (EGF) and Hepatocyte Growth Factor (HGF), stimulate this process in a majority of solid tumors. Tumor cell invasion is driven by many factors, including cell surface receptor tyrosine kinases, which are often highly expressed or hyper-activated in cancers [1]. Epidermal growth factor receptor (EGFR) and hepatocyte growth factor receptor (c-Met) are two receptor tyrosine kinases known to contribute to tumor progression [2]. While both c-Met and EGFR drive tumor cell growth and invasion, many tumors exhibit EGFR-driven growth independent of c-Met activation. Organelle fusion, or lysosome integrity, will cause growth factor receptors to recycle back to the plasma membrane for continued signaling events in

Methods

Results

Discussion

Conclusion