Open AccessEpidermal growth factor receptor lacking C‐terminal autophosphorylation sites retains signal transduction and high sensitivity to epidermal growth factor receptor tyrosine kinase inhibitor
Author(s) -
Maegawa Mari,
Arao Tokuzo,
Yokote Hideyuki,
Matsumoto Kazuko,
Kudo Kanae,
Tanaka Kaoru,
Kaneda Hiroyasu,
Fujita Yoshihiko,
Ito Fumiaki,
Nishio Kazuto
Publication year - 2009
Publication title -
cancer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.035
H-Index - 141
eISSN - 1349-7006
pISSN - 1347-9032
DOI - 10.1111/j.1349-7006.2008.01071.x
Subject(s) - autophosphorylation , hek 293 cells , epidermal growth factor receptor , tyrosine kinase , proto oncogene tyrosine protein kinase src , cancer research , tyrosine , phosphorylation , microbiology and biotechnology , tyrosine kinase inhibitor , erbb3 , epidermal growth factor , receptor tyrosine kinase , signal transduction , chemistry , biochemistry , biology , medicine , receptor , protein kinase a , cancer
Constitutively active mutations of epidermal growth factor receptor (EGFR) (delE746_A750) activate downstream signals, such as ERK and Akt, through the phosphorylation of tyrosine residues in the C‐terminal region of EGFR. These pathways are thought to be important for cellular sensitivity to EGFR tyrosine kinase inhibitors (TKI). To examine the correlation between phosphorylation of the tyrosine residues in the C‐terminal region of EGFR and cellular sensitivity to EGFR TKI, we used wild‐type (wt) EGFR, as well as the following constructs: delE746_A750 EGFR; delE746_A750 EGFR with substitution of seven tyrosine residues to phenylalanine in the C‐terminal region; and delE746_A750 EGFR with a C‐terminal truncation at amino acid 980. These constructs were transfected stably into HEK293 cells and designated HEK293/Wt, HEK293/D, HEK293/D7F, and HEK293/D‐Tr, respectively. The HEK293/D cells were found to be 100‐fold more sensitive to EGFR TKI (AG1478) than HEK293/Wt. Surprisingly, the HEK293/D7F and HEK293/D‐Tr cells, transfected with EGFR lacking the C‐terminal autophosphorylation sites, retained high sensitivity to EGFR TKI. In these three high‐sensitivity cells, the ERK pathway was activated without ligand stimulation, which was inhibited by EGFR TKI. In addition, although EGFR in the HEK293/D7F and HEK293/D‐Tr cells lacked significant tyrosine residues for EGFR signal transduction, phosphorylation of Src homology and collagen homology (Shc) was spontaneously activated in these cells. Our results indicate that tyrosine residues in the C‐terminal region of EGFR are not required for cellular sensitivity to EGFR TKI, and that an as‐yet‐unknown signaling pathway of EGFR may exist that is independent of the C‐terminal region of EGFR. ( Cancer Sci 2009; 100: 552–557)