Randi Wise1, Anna Zolkiewska2. 1. Department of Biochemistry and Molecular Biophysics, Kansas State University, 141 Chalmers Hall, Manhattan, KS, 66506, USA. 2. Department of Biochemistry and Molecular Biophysics, Kansas State University, 141 Chalmers Hall, Manhattan, KS, 66506, USA. zolkiea@ksu.edu.
Abstract
PURPOSE: The CD44+/CD24- cell phenotype is enriched in triple negative breast cancers, is associated with tumor invasive properties, and serves as a cell surface marker profile of breast cancer stem-like cells. Activation of Epidermal Growth Factor Receptor (EGFR) promotes the CD44+/CD24- phenotype, but the specific signaling pathway downstream of EGFR responsible for this effect is not clear. The purpose of this study was to determine the role of the MEK/ERK pathway in the expansion of CD44+/CD24- populations in TNBC cells in response to EGFR activation. METHODS: Representative TNBC cell lines SUM159PT (claudin-low) and SUM149PT (basal) were used to evaluate cell surface expression of CD44 and CD24 by flow cytometry in response to EGFR and MEK inhibition or activation. EGFR and ERK phosphorylation levels were analyzed by Western blotting. The relationship between EGFR phosphorylation and MEK activation score in basal and claudin-low tumors from the TCGA database was examined. RESULTS: Inhibition of ERK activation with selumetinib, a MEK1/2 inhibitor, blocked EGF-induced expansion of CD44+/CD24- populations. Sustained activation of ERK by overexpression of constitutively active MEK1 was sufficient to expand CD44+/CD24- populations in cells in which EGFR activity was blocked by either erlotinib, an EGFR kinase inhibitor, or BB-94, a metalloprotease inhibitor that prevents generation of soluble EGFR ligands. In basal and claudin-low tumors from the TCGA database, there was a positive correlation between EGFR_pY1068 and MEK activation score in tumors without genomic loss of DUSP4, a negative regulator of ERK, but not in tumors harboring DUSP4 deletion. CONCLUSION: Our results demonstrate that ERK activation is a key event in EGFR-dependent regulation of CD44+/CD24- populations. Furthermore, our findings highlight the role of ligand-mediated EGFR signaling in the control of MEK/ERK pathway output in TNBC tumors without DUSP4 loss.
PURPOSE: The CD44+/CD24- cell phenotype is enriched in triple negative breast cancers, is associated with tumor invasive properties, and serves as a cell surface marker profile of breast cancer stem-like cells. Activation of Epidermal Growth Factor Receptor (EGFR) promotes the CD44+/CD24- phenotype, but the specific signaling pathway downstream of EGFR responsible for this effect is not clear. The purpose of this study was to determine the role of the MEK/ERK pathway in the expansion of CD44+/CD24- populations in TNBC cells in response to EGFR activation. METHODS: Representative TNBC cell lines SUM159PT (claudin-low) and SUM149PT (basal) were used to evaluate cell surface expression of CD44 and CD24 by flow cytometry in response to EGFR and MEK inhibition or activation. EGFR and ERK phosphorylation levels were analyzed by Western blotting. The relationship between EGFR phosphorylation and MEK activation score in basal and claudin-low tumors from the TCGA database was examined. RESULTS: Inhibition of ERK activation with selumetinib, a MEK1/2 inhibitor, blocked EGF-induced expansion of CD44+/CD24- populations. Sustained activation of ERK by overexpression of constitutively active MEK1 was sufficient to expand CD44+/CD24- populations in cells in which EGFR activity was blocked by either erlotinib, an EGFR kinase inhibitor, or BB-94, a metalloprotease inhibitor that prevents generation of soluble EGFR ligands. In basal and claudin-low tumors from the TCGA database, there was a positive correlation between EGFR_pY1068 and MEK activation score in tumors without genomic loss of DUSP4, a negative regulator of ERK, but not in tumors harboring DUSP4 deletion. CONCLUSION: Our results demonstrate that ERK activation is a key event in EGFR-dependent regulation of CD44+/CD24- populations. Furthermore, our findings highlight the role of ligand-mediated EGFR signaling in the control of MEK/ERK pathway output in TNBC tumors without DUSP4 loss.
Entities:
Keywords:
Breast cancer; CD24; CD44; Cancer stem cells; Epidermal growth factor receptor; Metalloproteases; Mitogen-activated protein kinase pathway
Authors: Ricardo Costa; Ami N Shah; Cesar A Santa-Maria; Marcelo R Cruz; Devalingam Mahalingam; Benedito A Carneiro; Young Kwang Chae; Massimo Cristofanilli; William J Gradishar; Francis J Giles Journal: Cancer Treat Rev Date: 2017-01-05 Impact factor: 12.111
Authors: Chandra Bartholomeusz; Xuemei Xie; Mary Kathryn Pitner; Kimie Kondo; Ali Dadbin; Jangsoon Lee; Hitomi Saso; Paul D Smith; Kevin N Dalby; Naoto T Ueno Journal: Mol Cancer Ther Date: 2015-09-17 Impact factor: 6.261
Authors: Justin M Balko; Luis J Schwarz; Neil E Bhola; Richard Kurupi; Phillip Owens; Todd W Miller; Henry Gómez; Rebecca S Cook; Carlos L Arteaga Journal: Cancer Res Date: 2013-08-21 Impact factor: 12.701
Authors: José Baselga; Patricia Gómez; Richard Greil; Sofia Braga; Miguel A Climent; Andrew M Wardley; Bella Kaufman; Salomon M Stemmer; António Pêgo; Arlene Chan; Jean-Charles Goeminne; Marie-Pascale Graas; M John Kennedy; Eva Maria Ciruelos Gil; Andreas Schneeweiss; Angela Zubel; Jutta Groos; Helena Melezínková; Ahmad Awada Journal: J Clin Oncol Date: 2013-06-03 Impact factor: 44.544
Authors: Gillian Farnie; Robert B Clarke; Katherine Spence; Natasha Pinnock; Keith Brennan; Neil G Anderson; Nigel J Bundred Journal: J Natl Cancer Inst Date: 2007-04-18 Impact factor: 13.506