Anti-vascular endothelial growth factor receptor 2 antibody reduces tumorigenicity and metastasis in orthotopic prostate cancer xenografts via induction of endothelial cell apoptosis and reduction of endothelial cell matrix metalloproteinase type 9 production.
OBJECTIVE
Vascular endothelial growth factor (VEGF), which is produced by tumor cells, is a potent endothelial cell mitogen. The aim of the present study was to evaluate the response of orthotopic prostate cancer xenografts and prostate cancer bone metastasis to anti-VEGF receptor (flk-1) antibody (DC101) treatment.


METHODS
Orthotopic prostate cancer models (PC-3M-MM2 and LNCaP-LN3 prostate carcinoma cells) and a prostate cancer bone metastasis model (PC-3M-MM2) were used for these experiments. Early and established tumors were treated with saline, paclitaxel, DC101, or a DC101-plus-paclitaxel combination for 5 weeks (PC-3M-MM2) and 12 weeks (LNCaP-LN3). At the end of therapy, tumors were removed and weighed. Apoptosis, tumor cell proliferation, and angiogenesis- and metastasis-related gene expression were evaluated using immunohistochemistry, in situ hybridization, and terminal deoxynucleotidyl transferase-ediated nick end labeling (TUNEL).


RESULTS
After treatment of early tumors (PC-3M-MM2), median prostate tumor weights (+/-SE) were 1230 +/- 210 mg in untreated controls, 482 +/- 121 mg in mice treated with paclitaxel (P = 0.009), 148 +/- 27 mg in mice treated with DC101 (P < 0.001), and 48 +/- 10 mg in mice treated with the combination of DC101 and paclitaxel (P < 0.001). Lymph node metastasis occurred in 7 of the 9 control mice, 5 of the 9 paclitaxel-treated animals, 5 of the 12 DC101-treated animals, and 2 of the 11 animals in the combination therapy group. Treatment with DC101 alone or in combination with paclitaxel reduced tumor-induced neovascularity measured by microvessel density and tumor cell proliferation (by proliferating cell nuclear antigen) and enhanced apoptosis (measured by TUNEL) in tumor cells and endothelial cells compared with controls. In the tibial prostate cancer metastasis model, significant inhibition of tumor growth was observed. In the LNCaP-LN3 orthotopic prostate cancer model, tumors occurred in 7 of the 10 control mice, 4 of the 10 paclitaxel-treated animals, 5 of the 10 DC101-treated animals, and 2 of the 11 animals in the combination therapy group (P < 0.05). The efficacy of DC101 was much greater in the treatment of early tumors, which suggests that tumor burden may be a critical factor in determining the response to DC101. In vitro and in vivo analysis of endothelial cell function showed reduced matrix metalloproteinase type 9 production in endothelial cells treated with DC101.


CONCLUSIONS
This study confirms the principle of tumor growth inhibition by targeting angiogenesis within tumors and supports the use of anti-VEGF receptor agents.
Sweeney
Paul
P
Department of Urology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Karashima
Takashi
T
Kim
Sun-Jin
SJ
Kedar
Daniel
D
Mian
Badar
B
Huang
Samuel
S
Baker
Cheryl
C
Fan
Zhen
Z
Hicklin
Daniel J
DJ
Pettaway
Curtis A
CA
Dinney
Colin P N
CP
D000818:Animals; D000906:Antibodies / Q000627:therapeutic use*; D017209:Apoptosis; D002455:Cell Division; D004727:Endothelium / Q000166:cytology / Q000473:pathology*; D006801:Humans; D020287:In Situ Nick-End Labeling; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis*; D051379:Mice; D008819:Mice, Nude; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D009693:Nucleic Acid Hybridization; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000276:immunology*
D000906:Antibodies; D012333:RNA, Messenger; D040301:Vascular Endothelial Growth Factor Receptor-2; D020780:Matrix Metalloproteinase 9