Involvement of Ras activation in human breast cancer cell signaling, invasion, and anoikis.
Although mutated forms of ras are not associated with the majority of breast cancers (<5%), there is considerable experimental evidence that hyperactive Ras can promote breast cancer growth and development. Therefore, we determined whether Ras and Ras-responsive signaling pathways were activated persistently in nine widely studied human breast cancer cell lines. Although only two of the lines harbor mutationally activated ras, we found that five of nine breast cancer cell lines showed elevated active Ras-GTP levels that may be due, in part, to HER2 activation. Unexpectedly, activation of two key Ras effector pathways, the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase and phosphatidylinositol 3'-kinase/AKT signaling pathways, was not always associated with Ras activation. Ras activation also did not correlate with invasion or the expression of proteins associated with tumor cell invasion (estrogen receptor alpha and cyclooxygenase 2). We then examined the role of Ras signaling in mediating resistance to matrix deprivation-induced apoptosis (anoikis). Surprisingly, we found that ERK and phosphatidylinositol 3'-kinase/AKT activation did not have significant roles in conferring anoikis resistance. Taken together, these observations show that Ras signaling exhibits significant cell context variations and that other effector pathways may be important for Ras-mediated oncogenesis, as well as for anoikis resistance, in breast cancer. Additionally, because ERK and AKT activation are not strictly associated with Ras activation, pharmacological inhibitors of these two signaling pathways may not be the best approach for inhibition of aberrant Ras function in breast cancer treatment.
Eckert
Lynn B
LB
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7295, USA.
Repasky
Gretchen A
GA
Ulkü
Aylin S
AS
McFall
Aidan
A
Zhou
Hong
H
Sartor
Carolyn I
CI
Der
Channing J
CJ
D023102:Anoikis / Q000235:genetics / Q000502:physiology*; D001943:Breast Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2; D047628:Estrogen Receptor alpha; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology; D008565:Membrane Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009361:Neoplasm Invasiveness; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D011960:Receptors, Estrogen / Q000096:biosynthesis; D015398:Signal Transduction / Q000502:physiology; D018631:ras Proteins / Q000235:genetics / Q000502:physiology*
D051546:Cyclooxygenase 2; D047628:Estrogen Receptor alpha; D007527:Isoenzymes; D008565:Membrane Proteins; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D011451:Prostaglandin-Endoperoxide Synthases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D018631:ras Proteins; C496540:PTGS2 protein, human; C494918:AKT1 protein, human