Multiple oncogenic changes (K-RAS(V12), p53 knockdown, mutant EGFRs, p16 bypass, telomerase) are not sufficient to confer a full malignant phenotype on human bronchial epithelial cells.
We evaluated the contribution of three genetic alterations (p53 knockdown, K-RAS(V12), and mutant EGFR) to lung tumorigenesis using human bronchial epithelial cells (HBEC) immortalized with telomerase and Cdk4-mediated p16 bypass. RNA interference p53 knockdown or oncogenic K-RAS(V12) resulted in enhanced anchorage-independent growth and increased saturation density of HBECs. The combination of p53 knockdown and K-RAS(V12) further enhanced the tumorigenic phenotype with increased growth in soft agar and an invasive phenotype in three-dimensional organotypic cultures but failed to cause HBECs to form tumors in nude mice. Growth of HBECs was highly dependent on epidermal growth factor (EGF) and completely inhibited by EGF receptor (EGFR) tyrosine kinase inhibitors, which induced G1 arrest. Introduction of EGFR mutations E746-A750 del and L858R progressed HBECs toward malignancy as measured by soft agar growth, including EGF-independent growth, but failed to induce tumor formation. Mutant EGFRs were associated with higher levels of phospho-Akt, phospho-signal transducers and activators of transcription 3 [but not phospho-extracellular signal-regulated kinase (ERK) 1/2], and increased expression of DUSP6/MKP-3 phosphatase (an inhibitor of phospho-ERK1/2). These results indicate that (a) the HBEC model system is a powerful new approach to assess the contribution of individual and combinations of genetic alterations to lung cancer pathogenesis; (b) a combination of four genetic alterations, including human telomerase reverse transcriptase overexpression, bypass of p16/RB and p53 pathways, and mutant K-RAS(V12) or mutant EGFR, is still not sufficient for HBECs to completely transform to cancer; and (c) EGFR tyrosine kinase inhibitors inhibit the growth of preneoplastic HBEC cells, suggesting their potential for chemoprevention.
Hamon Center for Therapeutic Oncology Research, The University of Texas Southwestern Medical Center, Dallas 75390-8593, USA.
Mitsuo
M
Sato
Melville B
MB
Vaughan
Luc
L
Girard
Michael
M
Peyton
Woochang
W
Lee
David S
DS
Shames
Ruben D
RD
Ramirez
Noriaki
N
Sunaga
Adi F
AF
Gazdar
Jerry W
JW
Shay
John D
JD
Minna
D000368:Aged; D001980:Bronchi / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D048708:Cell Growth Processes / Q000187:drug effects / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D054642:Dual Specificity Phosphatase 6; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000069347:Erlotinib Hydrochloride; D005260:Female; D000077156:Gefitinib; D018773:Genes, erbB-1; D019942:Genes, p16; D016158:Genes, p53; D011905:Genes, ras; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009857:Oncogenes / Q000502:physiology*; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology; D034622:RNA Interference; D050796:STAT3 Transcription Factor / Q000378:metabolism; D019098:Telomerase / Q000235:genetics; D014162:Transfection; D015854:Up-Regulation
D011799:Quinazolines; D050796:STAT3 Transcription Factor; D004815:Epidermal Growth Factor; D000069347:Erlotinib Hydrochloride; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D020929:Mitogen-Activated Protein Kinase Kinases; D019098:Telomerase; C517035:DUSP6 protein, human; D054642:Dual Specificity Phosphatase 6; D017027:Protein Tyrosine Phosphatases; D000077156:Gefitinib