Inhibition of epidermal growth factor receptor kinase induces protease-dependent apoptosis in human colon cancer cells.
OBJECTIVE
The epidermal growth factor receptor (EGFR) is under investigation as a therapeutic target for cancers. Colon cancer cell lines are variably dependent on autocrine stimulation of EGFR. We therefore examined the effects of a selective EGFR tyrosine kinase inhibitor, PD 153035, on proliferation and survival of five colon cancer cell lines whose autonomous proliferation is either EGFR ligand dependent or EGFR ligand independent.


METHODS
Effects of inhibitors were screened by MTS growth assays, [3H]thymidine incorporation, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay, fluorescence microscopy, immunoblotting, and in vitro protease assays.


RESULTS
PD 153035 caused dose-dependent cytostasis (200 nmol/L to 1 micromol/L) and apoptosis (>10 micromol/L) in ligand-dependent cell lines and caused variable apoptosis (>10 micromol/L) but no cytostasis in ligand-independent cell lines. Apoptosis induced by 10 micromol/L PD 153035 was not associated with induction of p53 protein expression but was accompanied by activation of caspases that cleave poly(ADP-ribose) polymerase, lamin B1, and Bcl-2. Inhibition of caspase 3-like protease activity by DEVD-fluoromethylketone significantly delayed the onset of PD 153035-induced apoptosis.


CONCLUSIONS
The EGFR tyrosine kinase inhibitor PD 153035 induces cytostasis and caspase-dependent apoptosis in EGFR ligand-dependent colon cancer cell lines. These observations encourage further investigation of EGFR tyrosine kinase inhibitors for treatment of colorectal neoplasms.
Karnes
W E
WE
Division of Gastroenterology, Mayo Clinic, Rochester, Minnesota 55905, USA. karnes@ralph.mayo.edu
Weller
S G
SG
Adjei
P N
PN
Kottke
T J
TJ
Glenn
K S
KS
Gores
G J
GJ
Kaufmann
S H
SH
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D003110:Colonic Neoplasms / Q000473:pathology / Q000503:physiopathology*; D010450:Endopeptidases / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D011480:Protease Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D004791:Enzyme Inhibitors; D008024:Ligands; D011480:Protease Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D011799:Quinazolines; D016159:Tumor Suppressor Protein p53; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D010450:Endopeptidases; C088860:4-((3-bromophenyl)amino)-6,7-dimethoxyquinazoline