v-Ha-ras mitogenic signaling through superoxide and derived reactive oxygen species.
The ras proto-oncogene is frequently mutated in human tumors and functions to constitutively stimulate signal transduction cascades, resulting in unchecked proliferation and malignant transformation. In certain cells, superoxide functions as a signal-transduction messenger, mediating the downstream effects of ras and rac. We demonstrated previously that v-Ha-ras-transfected rat kidney epithelial cells (RECs) overproduced superoxide anion and that this superoxide production was mediated by ras. In the present study, we further demonstrated that v-Ha-ras overexpression transformed immortal nonmalignant RECs into malignant cancer cells; v-Ha-ras-transfected cells formed clones in soft agar, had high plating efficiency, and formed tumors in nude mice. Our data suggest that superoxide radical plays a role in ras-induced transformation; modulation of intracellular superoxide level by overexpression of manganese-containing superoxide dismutase or copper- and zinc-containing superoxide dismutase inhibited ras-induced transformation, as evidenced by in vitro studies of plating efficiency and by in vivo studies of tumor formation in nude mice. Overexpression of catalase (CAT) alone was found to have little effect on tumor cell growth, but overexpression of glutathione peroxidase 1 (GPx1) completely suppressed tumor cell growth in nude mice. This finding suggests that peroxides removed by GPx1, but not by CAT, are also involved in ras-induced transformation.
Yang
Ji-Qin
JQ
Free Radical and Radiation Biology Program, Department of Radiation Oncology, B180 Medical Laboratories, University of Iowa, Iowa City, Iowa, USA.
Buettner
Garry R
GR
Domann
Frederick E
FE
Li
Qiang
Q
Engelhardt
John F
JF
Weydert
Christine Darby
CD
Oberley
Larry W
LW
D000818:Animals; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D002460:Cell Line; D003114:Colony-Forming Units Assay; D011905:Genes, ras; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D007668:Kidney; D008934:Mitogens / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism; D015689:Oncogene Protein p21(ras) / Q000235:genetics / Q000378:metabolism; D000090063:Proto-Oncogene Mas; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014162:Transfection; D019459:Urothelium
C000715470:MAS1 protein, human; D008934:Mitogens; D016328:NF-kappa B; D000090063:Proto-Oncogene Mas; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D018808:Transcription Factor AP-1; D013481:Superoxides; D002374:Catalase; D013482:Superoxide Dismutase; D005982:Glutathione Transferase; D015689:Oncogene Protein p21(ras)