Inhibition of epidermal growth factor receptor kinase induces protease-dependent apoptosis in human colon cancer
W E Karnes1, S G Weller, P N Adjei
1Division of Gastroenterology, Mayo Clinic, Rochester, Minnesota 55905, USA. karnes@ralph.mayo.edu
Background & Aims:
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.
Insights
The EGFR tyrosine kinase inhibitor PD 153035 effectively reduces colon cancer cell growth and induces apoptosis in EGFR ligand-dependent cell lines. This suggests potential for treating colorectal neoplasms.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- Epidermal Growth Factor Receptor (EGFR) is a key target in cancer therapy.
- Colon cancer cell lines exhibit varying dependence on autocrine EGFR stimulation.
- Investigating selective EGFR tyrosine kinase inhibitors is crucial for cancer treatment.
Purpose of the Study:
- To evaluate the effects of PD 153035, a selective EGFR tyrosine kinase inhibitor, on colon cancer cell proliferation and survival.
- To differentiate the drug's efficacy based on EGFR ligand dependency in colon cancer cell lines.
Main Methods:
- Utilized MTS growth assays, [3H]thymidine incorporation, and TUNEL assays to assess proliferation and apoptosis.
- Employed fluorescence microscopy, immunoblotting, and in vitro protease assays to analyze cellular mechanisms.
- Screened the effects of PD 153035 on five distinct colon cancer cell lines.
Main Results:
- PD 153035 induced dose-dependent cytostasis and apoptosis in EGFR ligand-dependent cell lines.
- Apoptosis was observed in ligand-independent cell lines, but without cytostasis.
- Apoptosis involved caspase activation, cleaving PARP, lamin B1, and Bcl-2, independent of p53 induction.
Conclusions:
- PD 153035 triggers cytostasis and caspase-dependent apoptosis in EGFR ligand-dependent colon cancer cells.
- These findings support further research into EGFR tyrosine kinase inhibitors for colorectal cancer treatment.
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