P051 Inhibition of lymphangiogenesis via VEGFR-3 as a novel therapy for IBD-related colorectal cancer

Abstract

Background: Chronic intestinal inflammation that occurs in Inflammatory Bowel Disease (IBD) predisposes to colitisassociated colorectal cancer (CAC). Tumor-induced lymphangiogenesis is one of the mechanisms that promotes metastasis to regional lymph nodes, but no mechanistic data is available on the molecules involved in modulating lymphangiogenesis and tumor development in CAC. VEGF-C is a key molecule in lymphangiogenesis that signals through its cognat receptor VEGFR-3 and its blockade has been successful in several models of cancer and metastasis. We hypothesized that lymphatic vessel-directed therapy may be therapeutically effective in CAC. Methods: We addressed these issues in vivo by systemic inhibition of the VEGFR-3 or delivery of the lymphangiogenic factor VEGF-C in the AOM/DSS model of CAC by a blocking antibody or adenovirus transfer, respectively. Tumor density and size were measured at the end of the protocol by visual, endoscopical and histological inspection. Whole mounts of colons were stained with antibodies against LYVE-1 and CD31 to analyze area density and dimension of the lymphatic vessels within tumoral and peritumoral regions. Moreover, in vitro tubulogenesis assays were used to assess human tumor-isolated intestinal lymphatic endothelial cell (HILEC) organization into capillary tubules using a Matrigel system. Results: Systemic administration of an anti-VEGFR-3 antibody inhibited lymphangiogenesis in tumoral and peritumoral regions, reducing both area density (from 48±1.1 to 10±0.6 vessels/mm2) and lymphatic vessel dimension (from 78±1.8mm to 24±0.6mm, p < 0.01), while increasing inflammatory edema formation. In addition, it reduced tumor density (from 15±0.8 to 3±0.3 tumors/mouse, p < 0.01) and size (from 6.4±0.4mm to 2.3±0.1mm, p < 0.01), in comparison with untreated mice. In contrast, tumor density and growth was enhanced by systemic delivery of the lymphangiogenic factor VEGF-C, which in turn increased lymphangiogenesis within the same regions. HILEC isolated from colorectal cancer biopsies showed increased growth rate and capacity to undergo tubulogenesis in vitro (38±1.5 number of tumoral tubes vs 14±0.5 number of NL tubes, p < 0.01) compared to healthy control tissues. Conclusions: Our findings demonstrate that VEGFC/VEGFR3-dependent lymphangiogenesis plays a role not only in metastasis dissemination, but also in colitis-associated tumor growth. Therefore, the lymphatic vasculature may be a promising target for the prevention and the treatment of CAC.