The endogenous soluble VEGF receptor-2 isoform suppresses lymph node metastasis in a mouse immunocompetent mammary cancer model.
BACKGROUND
Cancer metastasis contributes significantly to cancer mortality and is facilitated by lymphangiogenesis and angiogenesis. A new splicing variant, endogenous soluble vascular endothelial growth factor receptor-2 (esVEGFR-2) that we recently identified is an endogenous selective inhibitor of lymphangiogenesis. To evaluate the antimetastatic potential of esVEGFR-2, gene therapy with vector expressing esVEGFR-2 (pesVEGFR-2) or endostatin (pEndo) as a positive control was conducted on murine metastatic mammary cancer.


METHODS
Syngeneic inoculated metastatic mammary cancers received direct intratumoral injection of pesVEGFR-2, pEndo or pVec as control, once a week for six weeks. In vivo gene electrotransfer was performed on the tumors after each injection.


RESULTS
Deaths from metastasis were much lower in the pesVEGFR-2 and pEndo groups than in those of the pVec. Tumor volume was significantly lower in the pesVEGFR-2 and the pEndo groups throughout the study. Multiplicity of lymph node and lung metastatic nodules was significantly suppressed in the pesVEGFR-2 and pEndo groups. Moreover, the total number of overall metastasis including the other organs was also decreased in these groups. However, pesVEGFR-2 was not able to decrease the number of lungs, ovaries, kidneys and adrenals with metastasis as counted by unilateral or bilateral metastasis. The number of CD34+/Lyve-1⁻ blood microvessels was significantly decreased in the pEndo group, while the number of CD34⁻/Lyve-1+ lymphatic vessels was significantly decreased in the pesVEGFR-2 and pEndo groups. In addition, a significant reduction in the number of dilated lymphatic vessels containing intraluminal cancer cells was observed in the pesVEGFR-2 and pEndo groups. Levels of apoptosis were significantly increased in the pEndo group, whereas the rates of cell proliferation were significantly decreased in the pesVEGFR-2 and pEndo groups.


CONCLUSIONS
Our data demonstrate that esVEGFR-2 can inhibit mainly lymph node metastasis. The antimetastatic activity of esVEGFR-2 may be of high clinical significance in the treatment of metastatic breast cancer because lymph node involvement is a most important prognostic factor in cancer patients.
Department of Anatomy and Cell Biology, Osaka Medical College, Japan. shibatam@art.osaka-med.ac.jp
Masa-Aki
MA
Shibata
Jayakrishna
J
Ambati
Eiko
E
Shibata
Romulo J C
RJ
Albuquerque
Junji
J
Morimoto
Yuko
Y
Ito
Yoshinori
Y
Otsuki
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D015316:Genetic Therapy; D005822:Genetic Vectors; D007121:Immunocompetence; D008175:Lung Neoplasms / Q000556:secondary; D042583:Lymphangiogenesis / Q000187:drug effects* / Q000235:genetics; D008207:Lymphatic Metastasis / Q000235:genetics*; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D023421:Models, Animal; D009362:Neoplasm Metastasis; D020033:Protein Isoforms; D040262:Receptors, Vascular Endothelial Growth Factor / Q000235:genetics* / Q000494:pharmacology / Q000627:therapeutic use*; D047368:Tumor Burden / Q000187:drug effects; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000235:genetics* / Q000494:pharmacology / Q000627:therapeutic use*; D042442:Vascular Endothelial Growth Factors / Q000235:genetics*
D020033:Protein Isoforms; D042442:Vascular Endothelial Growth Factors; D040262:Receptors, Vascular Endothelial Growth Factor; D040301:Vascular Endothelial Growth Factor Receptor-2