Inhibition of epidermal growth factor receptor signaling decreases p63 expression in head and neck squamous carcinoma cells.
OBJECTIVE
Both the epidermal growth factor receptor (EGFR) and the p53 homologue p63 are overexpressed in a significant number of cases of head and neck squamous cell carcinoma (HNSCC). Epidermal growth factor receptor and p63 both possess oncogenic properties, including the potential to increase cell proliferation and antagonize apoptosis. ZD1839 ("Iressa") is an adenosine triphosphate-competitive inhibitor specific to the EGFR tyrosine kinase currently under evaluation as a chemotherapeutic agent in HNSCC. The objective was to investigate whether p63 expression is decreased after treatment of HNSCC cells with ZD1839. Downregulation of p63 by ZD1839 would identify a potential molecular relationship between EGFR signaling and p63 and could provide insight into the mechanism of action of ZD1839.


METHODS
In vitro examination of p63 expression after ZD1839 treatment.


METHODS
A human HNSCC cell line, SCC-012, was treated with varying doses of ZD1839. p63 protein and messenger RNA levels were analyzed by Western and Northern blot analyses. The effect of ZD1839 on SCC-012 cell cycle was analyzed by flow cytometric analysis.


RESULTS
In SCC-012 cells there was a dose-dependent decrease in p63 protein and messenger RNA levels over the course of ZD1839 treatment. Levels of phosphorylated MAPK decreased and p27KIP-1 levels increased after ZD1839 treatment. ZD1839 treatment induced a twofold increase in G1-phase cells and a 3.5-fold decrease in S-phase cells consistent with growth arrest.


CONCLUSIONS
ZD1839 downregulates p63 expression at the messenger RNA level, suggesting that p63 is a downstream target of EGFR signaling.
Matheny
Keith E
KE
Vanderbilt Bill Wilkerson Department of Otolaryngology-Head and Neck Surgery, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Barbieri
Christopher E
CE
Sniezek
Joseph C
JC
Arteaga
Carlos L
CL
Pietenpol
Jennifer A
JA
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D015152:Blotting, Northern; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000502:physiology; D005434:Flow Cytometry; D000077156:Gefitinib; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D016147:Genes, Tumor Suppressor; D006801:Humans; D008565:Membrane Proteins; D009062:Mouth Neoplasms / Q000235:genetics* / Q000473:pathology; D010750:Phosphoproteins / Q000235:genetics*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011799:Quinazolines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000473:pathology; D025521:Tumor Suppressor Proteins
D000970:Antineoplastic Agents; C081876:CKAP4 protein, human; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D011799:Quinazolines; D012333:RNA, Messenger; C115051:TP63 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D000077156:Gefitinib