EGFR regulates the side population in head and neck squamous cell carcinoma.
OBJECTIVE
To identify the presence of side population (SP) cells in established head and neck squamous carcinoma cell (HNSCC) lines and to determine the role of EGFR in the regulation of the side population of these cells.


METHODS
SP cells were identified using flow cytometry analysis by the ability of these cells to extrude the Hoechst 33342 dye via the drug transporter BCRP1/ABCG2. Effect of EGFR on the side population was determined also by difference in Hoechst extrusion and by immunofluorescence. Immunohistochemical staining was performed to show the presence of the BCRP1/ABCG2 transporter and the phosphorylated form of EGFR in HNSCC tissue.


RESULTS
SP cells are present in HNSCC cell lines. With the Hoechst 33342 extrusion assay, SP cells were found to comprise an average of 0.69% of the UMSCC10B cells and 0.91% of HN12 cells. Addition of the EGF ligand increased the SP population while inactivation of the EGFR kinase by Iressa significantly decreased SP.


CONCLUSIONS
In established head and neck squamous cell carcinoma cell lines, SP cells were found using methods that determine expression and function of the drug transporter BCRP1/ABCG2. Activation of EGFR, a gene implicated in tumorigenesis in HNSCC leads to increased SP, and conversely, inhibition of EGFR leads to decrease in SP. This finding could help explain the role of EGFR in regulating cancer stem cells and thus tumorigenesis in HNSCC.
Division of Head and Neck Surgery, Department of Surgery, University of California, San Diego, San Diego, California 92093, USA.
Jocelyn S
JS
Chen
Francisco S
FS
Pardo
Jessica
J
Wang-Rodriguez
Theresa S
TS
Chu
Jay Patrick
JP
Lopez
Joseph
J
Aguilera
Xabier
X
Altuna
Robert A
RA
Weisman
Weg M
WM
Ongkeko
D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D000077156:Gefitinib; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology*; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D009363:Neoplasm Proteins / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology
C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D009363:Neoplasm Proteins; D011799:Quinazolines; D066246:ErbB Receptors; D000077156:Gefitinib