Oncogenic K-Ras regulates proliferation and cell junctions in lung epithelial cells through induction of cyclooxygenase-2 and activation of metalloproteinase-9.
Expression of oncogenic K-Ras is frequently observed in non-small-cell lung cancer. However, oncogenic K-Ras is not sufficient to transform lung epithelial cells and requires collaborating signals that have not been defined. To examine the biological effects of K-Ras in nontransformed lung epithelial cells, stable transfectants were generated in RL-65 cells, a spontaneously immortalized lung epithelial cell line. Expression of K-Ras resulted in extracellular signal-regulated kinase (ERK) activation, which mediated induction of cyclooxygenase (COX)-2 and increased prostaglandin E(2) production. Epithelial cells expressing oncogenic K-Ras showed increased proliferation in two- and three-dimensional tissue culture and delayed formation of hollow acinar structures in three-dimensional matrigel cultures. These affects were mediated through COX-2-dependent activation of beta-catenin signaling and inhibition of apoptosis. ERK activation also led to induction of metalloproteinase (MMP)-9 and cleavage of E-cadherin at two specific sites. This resulted in partial disruption of adherens junctions as determined by decreased transepithelial resistance (TER), and disruption of E-cadherin/beta-catenin interactions. An MMP-9 inhibitor reversed the decrease in TER and inhibited beta-catenin signaling. These data indicate that although expression of oncogenic K-Ras does not transform lung epithelial cells, it alters the phenotype of the cells by increasing proliferation and decreasing cell-cell contacts characteristic of epithelial cells.
Wang
Xue-Qing
XQ
Department of Medicine, University of Colorado Denver, Denver, CO 80262, USA.
Li
Howard
H
Van Putten
Vicki
V
Winn
Robert A
RA
Heasley
Lynn E
LE
Nemenoff
Raphael A
RA
D000595:Amino Acid Sequence; D000818:Animals; D015820:Cadherins / Q000737:chemistry / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology / Q000473:pathology; D018929:Cell Culture Techniques; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000096:biosynthesis*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D017097:Electric Impedance; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D007365:Intercellular Junctions / Q000187:drug effects / Q000201:enzymology*; D008168:Lung / Q000166:cytology* / Q000201:enzymology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D008969:Molecular Sequence Data; D055550:Protein Stability / Q000187:drug effects; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D051176:beta Catenin / Q000378:metabolism
D015820:Cadherins; D016861:Cyclooxygenase Inhibitors; C528430:Kras protein, rat; D051176:beta Catenin; D051546:Cyclooxygenase 2; C489691:Ptgs2 protein, rat; D020780:Matrix Metalloproteinase 9; D016283:Proto-Oncogene Proteins p21(ras)