Inhibition of MAPK kinase signaling pathways suppressed renal cell carcinoma growth and angiogenesis in vivo.
The mitogen-activated protein kinase (MAPK) signaling pathways play essential roles in cell proliferation and differentiation. Recent studies also show the activation of MAPK signaling pathways in tumorigenesis, metastasis, and angiogenesis of multiple human malignancies, including renal cell carcinoma (RCC). To assess the role of this pathway in regulating the proliferation and survival of RCC cells, we first examined the expression of MAPK kinase (MKK) and MAPK in clear cell RCC and confirmed the overexpression of MKK1 and extracellular signal-regulated kinase 2 (ERK2) in these tumors. We then tested the effects of pharmacologic inhibition of MKK on human RCC cell lines, both in vitro and in vivo, using anthrax lethal toxin (LeTx), which cleaves and inactivates several MKKs. Western blotting showed that the phosphorylation levels of ERK, c-Jun-NH(2) kinase, and p38 MAPK decreased after 72 h of LeTx treatment. Exposure to LeTx for 72 h reduced cell proliferation by 20% without significant effects on cell cycle distribution and apoptosis. Anchorage-independent growth of RCC cells was dramatically inhibited by LeTx. In vivo studies showed that tumor growth of RCC xenografts could be suppressed by LeTx. Extensive necrosis and decreased tumor neovascularization were observed after LeTx treatment. LeTx also showed direct inhibition of proliferation of endothelial cells in vitro. Our results suggest that suppression of one or more MAPK signaling pathways may inhibit RCC growth through the disruption of tumor vasculature.
Huang
Dan
D
Laboratory of Cancer Genetics, Van Andel Research Institute, Grand Rapids, Michigan 49503, USA.
Ding
Yan
Y
Luo
Wang-Mei
WM
Bender
Stephanie
S
Qian
Chao-Nan
CN
Kort
Eric
E
Zhang
Zhong-Fa
ZF
VandenBeldt
Kristin
K
Duesbery
Nicholas S
NS
Resau
James H
JH
Teh
Bin Tean
BT
D000818:Animals; D000942:Antigens, Bacterial / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000494:pharmacology*; D002292:Carcinoma, Renal Cell / Q000098:blood supply* / Q000201:enzymology / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D007680:Kidney Neoplasms / Q000098:blood supply* / Q000201:enzymology* / Q000473:pathology; D051379:Mice; D008815:Mice, Inbred Strains; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000201:enzymology*; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
D000942:Antigens, Bacterial; D000970:Antineoplastic Agents; D001427:Bacterial Toxins; C030325:anthrax toxin; D020929:Mitogen-Activated Protein Kinase Kinases