EGF-dependent induction of BCL-xL and p21CIP1/WAF1 is highly variable in HNSCC cells--implications for EGFR-targeted therapies.
The anti-apoptotic protein BCL-x(L) and the cell cycle inhibitor p21(CIP1/WAF1) were previously implicated in head and neck cancer. Several reports point to a role of the epidermal growth factor receptor (EGFR, ErbB-1, HER1) in regulating their expression. In the present study, we investigated the influence of EGFR on these tumor-associated factors. HNSCC cell lines were incubated with EGF or with the EGFR-specific kinase inhibitor AG1478. Western blot analysis and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were deployed to measure BCL-x(L) and p21(CIP1/WAF1) protein and mRNA levels. A dose-dependent rise of BCL-x(L) as well as p21(CIP1/WAF1) protein was noted after incubation with EGF, whereas inhibition with AG1478 reduced basal expression levels. No influence on BCL-2 was seen. Interestingly, qRT-PCR revealed that p21(CIP1/WAF1) but not BCL-x(L) transcript levels were induced after EGF treatment. Taken together, it can be stated that p21(CIP1/WAF1) and BCL-x(L) but not BCL-2 levels are tightly regulated by EGFR in HNSCC cell lines. BCL-x(L) induction appears to be due to protein stabilization rather than transcriptional activation, which is the likely cause of p21(CIP1/WAF1) induction. The noted variability in EGF response of HNSCC cells could reflect frequently observed variations in clinical response rates after implementation of anti-EGFR therapies.
Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Giessen and Marburg, Campus Marburg, D-35037 Marburg, Germany.
Jessica
J
Rüddel
Vanessa E
VE
Wennekes
Wolfgang
W
Meissner
Jochen A
JA
Werner
Robert
R
Mandic
D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000627:therapeutic use*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D006258:Head and Neck Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D011799:Quinazolines; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D020032:Tyrphostins / Q000494:pharmacology; D051020:bcl-X Protein / Q000235:genetics* / Q000378:metabolism
C494811:BCL2L1 protein, human; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004791:Enzyme Inhibitors; D011799:Quinazolines; D012333:RNA, Messenger; D020032:Tyrphostins; D051020:bcl-X Protein; C101044:RTKI cpd; D004815:Epidermal Growth Factor; C512478:EGFR protein, human; D066246:ErbB Receptors