K-Ras promotes angiogenesis mediated by immortalized human pancreatic epithelial cells through mitogen-activated protein kinase signaling pathways.
Activating point mutations in the K-Ras oncogene are among the most common genetic alterations in pancreatic cancer, occurring early in the progression of the disease. However, the function of mutant K-Ras activity in tumor angiogenesis remains poorly understood. Using human pancreatic duct epithelial (HPDE) and K-Ras4B(G12V)-transformed HPDE (HPDE-KRas) cells, we show that activated K-Ras significantly enhanced the production of angiogenic factors including CXC chemokines and vascular endothelial growth factor (VEGF). Western blot analysis revealed that K-Ras activation promoted the phosphorylation of Raf/mitogen-activated protein kinase kinase-1/2 (MEK1/2) and expression of c-Jun. MEK1/2 inhibitors, U0126 and PD98059, significantly inhibited the secretion of both CXC chemokines and VEGF, whereas the c-Jun NH(2)-terminal kinase inhibitor SP600125 abrogated only CXC chemokine production. To further elucidate the biological functions of oncogenic K-Ras in promoting angiogenesis, we did in vitro invasion and tube formation assays using human umbilical vein endothelial cells (HUVEC). HUVEC cocultured with HPDE-KRas showed significantly enhanced invasiveness and tube formation as compared with either control (without coculture) or coculture with HPDE. Moreover, SB225002 (a CXCR2 inhibitor) and 2C3 (an anti-VEGF monoclonal antibody) either alone or in a cooperative manner significantly reduced the degree of both Ras-dependent HUVEC invasiveness and tube formation. Similar results were obtained using another pair of immortalized human pancreatic duct-derived cells, E6/E7/st and its oncogenic K-Ras variant, E6/E7/Ras/st. Taken together, our results suggest that angiogenesis is initiated by paracrine epithelial secretion of CXC chemokines and VEGF downstream of activated oncogenic K-Ras, and that this vascular maturation is in part dependent on MEK1/2 and c-Jun signaling.
Matsuo
Yoichi
Y
Department of Gastroenterology, The University of Texas M. D. Anderson Cancer Center, Houston, USA.
Campbell
Paul M
PM
Brekken
Rolf A
RA
Sung
Bokyung
B
Ouellette
Michel M
MM
Fleming
Jason B
JB
Aggarwal
Bharat B
BB
Der
Channing J
CJ
Guha
Sushovan
S
D021441:Carcinoma, Pancreatic Ductal / Q000098:blood supply / Q000201:enzymology / Q000235:genetics; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D019743:Chemokines, CXC / Q000096:biosynthesis / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D011905:Genes, ras; D006801:Humans; D020935:MAP Kinase Signaling System; D009389:Neovascularization, Pathologic / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000098:blood supply* / Q000201:enzymology / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D019743:Chemokines, CXC; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D048049:Extracellular Signal-Regulated MAP Kinases; D018631:ras Proteins