Tuberous sclerosis-associated neoplasms express activated p42/44 mitogen-activated protein (MAP) kinase, and inhibition of MAP kinase signaling results in decreased in vivo tumor growth.
OBJECTIVE
Tuberous sclerosis (TS) is a common autosomal disorder attributable to inactivation of the tumor suppressor genes tuberin and hamartin. To determine whether mitogen-activated protein (MAP) kinase signaling plays a role in the pathogenesis of TS, we stained human TS-associated neoplasms with antibodies directed against activated MAP kinase, and observed high-level expression.


METHODS
To determine whether MAP kinase is functionally important for the development of neoplasia in TS, we established a murine model of TS-associated neoplasia (Tsc2Ang1 cells) from a tumor arising in a mouse heterozygous for tuberin. Tsc2Ang1 cells demonstrate tumorigenesis in vivo and high-level expression of activated MAP kinase in vitro. The functionality of MAP kinase signaling was assessed by inactivating MAP kinase using a dominant-negative MAP kinase kinase in tsc2ang1 cells and assessing the effect of this intervention on in vivo tumorigenicity and production of the potent angiogenic factor vascular endothelial growth factor (VEGF).


RESULTS
Human TS-related neoplasms demonstrate high-level expression of activated MAP kinase, as does a tumor arising in a mouse heterozygous for tuberin. The inhibition of MAP kinase signaling by the introduction of a dominant-negative MAP kinase kinase leads to the inhibition of tumor growth in vivo and decreased production of VEGF.


CONCLUSIONS
MAP kinase is activated in TS-related neoplasia in mice and humans. Inhibition of MAP kinase leads to decreased tumor growth in vivo. Pharmacological inhibition of MAP kinase may be a therapeutic target in the prevention and treatment of TS-related tumors.
Govindarajan
Baskaran
B
Department of Dermatology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Mizesko
Melissa C
MC
Miller
Mark Steven
MS
Onda
Hiroaki
H
Nunnelley
Matthew
M
Casper
Katherine
K
Brat
Daniel
D
Cohen
Cynthia
C
Arbiser
Jack L
JL
Nunnelly
Matthew
M
D042501:Angiogenic Proteins / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D004247:DNA / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005091:Exons; D017353:Gene Deletion; D005799:Genes, Dominant; D006579:Heterozygote; D007150:Immunohistochemistry; D020935:MAP Kinase Signaling System; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000096:biosynthesis*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000096:biosynthesis*; D009369:Neoplasms / Q000201:enzymology*; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012509:Sarcoma / Q000378:metabolism; D015398:Signal Transduction; D014402:Tuberous Sclerosis / Q000150:complications* / Q000473:pathology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D042501:Angiogenic Proteins; D004791:Enzyme Inhibitors; D042461:Vascular Endothelial Growth Factor A; D004247:DNA; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases