P21-Activated Kinase 1 Promotes Breast Tumorigenesis via Phosphorylation and Activation of the Calcium/Calmodulin-Dependent Protein Kinase II.

Héctor Iván Saldívar-Cerón ,Laura Padierna-Mota,Jonathan Chernoff,Alonso Vivar-Sierra,Genaro Patiño-López,Alejandro López-Saavedra,José Esparza-López,Marco A Loza-Mejía,Luis E Arias-Romero,Claire M Wells,Clara M Rivera-Pazos,Paola Briseño-Díaz,Olga Villamar-Cruz,Mayra Montecillo-Aguado,Alfonso Leon-Del-Rio,Federica Spaggiari,Rosaura Hernández‐Rivas ,Marı́a De Jesús Ibarra-Sánchez ,İbrahim Oğuz ,Sara Huerta-Yépez ,Alejandro Zentella‐Dehesa

doi:10.3389/fcell.2021.759259

Abstract

p21-Activated kinase-1 (Pak1) is frequently overexpressed and/or amplified in human breast cancer and is necessary for transformation of mammary epithelial cells. Here, we show that Pak1 interacts with and phosphorylates the Calcium/Calmodulin-dependent Protein Kinase II (CaMKII), and that pharmacological inhibition or depletion of Pak1 leads to diminished activity of CaMKII. We found a strong correlation between Pak1 and CaMKII expression in human breast cancer samples, and combined inhibition of Pak1 and CaMKII with small-molecule inhibitors was synergistic and induced apoptosis more potently in Her2 positive and triple negative breast cancer (TNBC) cells. Co-adminstration of Pak and CaMKII small-molecule inhibitors resulted in a dramatic reduction of proliferation and an increase in apoptosis in a 3D cell culture setting, as well as an impairment in migration and invasion of TNBC cells. Finally, mice bearing xenografts of TNBC cells showed a significant delay in tumor growth when treated with small-molecule inhibitors of Pak and CaMKII. These data delineate a signaling pathway from Pak1 to CaMKII that is required for efficient proliferation, migration and invasion of mammary epithelial cells, and suggest new therapeutic strategies in breast cancer.

Highlights

Breast cancer is one of the most common malignancies among women and is the fifth leading cause of cancer-related deaths (Siegel et al, 2012; Sung et al, 2021)
Recent reports indicate that p21-Activated kinase-1 (Pak1) overexpression is associated with poor prognosis in a number of different solid tumors, with higher Pak1 expression linked to poor outcome including shortened progression free and overall survival (Fang et al, 2016)
Our results indicate that Pak1 and Calmodulin-dependent Protein Kinase II (CaMKII) expression is correlated in human breast cancer specimens, and our analysis of the METABRIC study showed significantly worse overall survival in breast cancer patients with co-expression of Pak1 and CaMKII

Summary

INTRODUCTION

Breast cancer is one of the most common malignancies among women and is the fifth leading cause of cancer-related deaths (Siegel et al, 2012; Sung et al, 2021). Some of the most prominent signaling networks affected in breast cancer include, the phosphoinositide 3-kinase (PI3K)/Akt/ mTOR, Ras/RAF/MEK/ERK, and Src/Fak pathways (Marcotte and Muller, 2008). We show that Pak1-deficient breast cancer cells showed a dramatic reduction in CaMKII phosphorylation at residue T287, which is important for the activity of this kinase. We demonstrated that the combination of small molecule inhibitors targeting Pak and CaMKII significantly delayed the tumorigenesis of TNBC cells in a xenograft setting. These data delineate a signaling pathway from Pak to CaMKII that is required for efficient proliferation, migration and invasion of mammary epithelial cells, and suggest new therapeutic avenues for the treatment of TNBC

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ETHICS STATEMENT