Suppression of vascular endothelial growth factor receptor 3 (VEGFR3) and vascular endothelial growth factor C (VEGFC) inhibits hypoxia-induced lymph node metastases in cervix cancer

Abstract

Objectives: We have examined the role of VEGFC/VEGFR3 signaling in lymph node metastasis and growth of orthotopic human ME180 and SiHa cervical xenograft models following exposure to hypoxia. Our previous studies showed that growth of these tumors under conditions of cyclic hypoxia increased nodal metastasis.

Methods: Mice bearing orthotopic tumors were subjected to cyclic hypoxia at 7% O(2)/air 10min cycles 4h/day/2weeks. Knockdown of vegfc was carried out by shRNA and inhibition of VEGFR3 was conducted by blocking antibodies for the mouse and human proteins. VEGFR3 protein expression was detected by Western blotting. Immunohistochemical staining was used to assess CA9, CD31, LYVE1 and Ki67 labeling. Gene expression was determined by real time PCR.

Results: Knock down of vegfc or inhibition of VEGFR3 with blocking antibody reduced metastases under normoxic and cyclic hypoxia conditions. A reduction in lymphatics and blood vessel formation and a decrease in tumor cell proliferation was observed following vegfc knockdown and VEGFR3 inhibition. VEGFR3 expression was upregulated at the mRNA and protein levels following hypoxia.

Conclusions: Collectively, our results indicate that anti-VEGFR3 antibody inhibits vegfc-induced tumor lymphangiogenesis and metastasis and that vegfc knockdown in the tumor cells causes a similar inhibitory effect on lymph node metastasis. These results suggest that the effects of vegfc/VEGFR3 on the progression of tumor cells to form lymph node metastases occur primarily under an hypoxic tumor microenvironment.