Targeting p21-activated kinase 1 inhibits growth and metastasis via Raf1/MEK1/ERK signaling in esophageal squamous cell carcinoma cells

Liang Chen,Songqiang Xie,Chaojie Wang,Zhijun Zhao,Jiuzhou Hou,Shuning Bi

doi:10.1186/s12964-019-0343-5

Abstract

Backgroundp21-activated kinase 1 (PAK1) plays a fundamental role in promoting the development and progression of several cancers and is a potential therapeutic target. However, the biological function and underlying mechanism of PAK1 in esophageal squamous cell carcinoma (ESCC) remain unclear.MethodsThe expression of PAK1 was detected in both ESCC cell lines and clinical samples. Cell growth was measured by MTT, focus formation and soft agar assays. Cell migration and invasion were detected by wound healing and transwell assays. Animal models of subcutaneous tumourigenicity and tail vein metastasis were performed to determine the inhibitory effect of pharmacological inhibitor IPA-3 on tumor growth and metastasis of ESCC cells.ResultsWe found that PAK1 was frequently overexpressed in ESCC. Ectopic expression of PAK1 promoted cellular growth, colony formation and anchorage-independent growth. Overexpressing PAK1 also enhanced migration, invasion and the expression of MMP-2 and MMP-9 in ESCC cells. In contrast, silencing PAK1 by lentiviral knockdown or a specific inhibitor IPA-3 resulted in a contrary effect. Subsequent investigations revealed that Raf1/MEK1/ERK signaling pathway was involved in PAK1-mediated effect. Enhanced expression of Raf1 attenuated the inhibitory functions of PAK1 shRNA. Whereas blocking of Raf1 by shRNA or specific inhibition of MEK1 by U0126 antagonized the oncogenetic effect of PAK1 on ESCC cells. More importantly, Pharmacological inhibition of PAK1 by IPA-3 significantly suppressed tumor growth and lung metastasis of ESCC cells in vivo.ConclusionsThese data support that PAK1 is an ideal target for the development of potential therapeutic drugs for ESCC patients even with metastasis.

Highlights

Esophageal cancer is one of the most common gastrointestinal cancer and ranks as the sixth leading cause of cancer mortalities worldwide, with an estimated 456,000 new cases and 400,000 deaths in 2012 [1, 2]
We found that inhibition of p21-activated kinase 1 (PAK1) by using short-hairpin RNA (shRNA) and a small-molecule inhibitor (IPA-3) remarkably suppressed esophageal squamous cell carcinoma (ESCC) cell proliferation, colony formation, migration and invasion in vitro, and tumor growth and lung metastasis in vivo, at least in part, via down-regulating the Raf1/MEK1/Extracellular regulated protein kinases (ERK) signaling pathway
Subsequent investigations revealed that Raf1/MEK/ERK signaling pathway was involved in PAK1-mediated effect

Summary

Introduction

Esophageal cancer is one of the most common gastrointestinal cancer and ranks as the sixth leading cause of cancer mortalities worldwide, with an estimated 456,000 new cases and 400,000 deaths in 2012 [1, 2]. Yang et al reported that overexpression of PAK1 correlates with aberrant expression of EMT markers and poor prognosis in non-small cell lung cancer [14]. All these findings indicate that PAK1 may play a central role in regulating tumorigenesis and metastasis. Knockdown of PAK1 by pharmacological inhib ition and using short-hairpin RNA (shRNA) can signifi cantly in hibit human cancer cell proliferation, anchorage-independent growth, migration and invasion in vitro and reduce tumor growth and metastasis in animal models [10, 11, 16,17,18]. Whether PAK1 is involved in ESCC development, progression and the underpinning molecular mechanisms remain unclear

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Discussion

Conclusion