Tumor-induced lymphangiogenesis in cervical lymph nodes in oral melanoma-bearing mice

Ryuki Ozasa,Teruaki Iwahashi,Kunihisa Taniguchi,Jun Ohno

doi:10.1186/1756-9966-31-83

Abstract

BackgroundMetastasis via the lymphatic system is promoted by lymphangiogenesis. Alterations of the lymphatic channels during the progression of metastasis to regional lymph nodes (LNs) remain unexplored. To examine whether tumor-induced LN lymphangiogenesis controls metastasis to regional LNs, we investigated cervical LN metastasis in a mouse model of oral melanoma.MethodsInjection of B16F10 melanoma cells into mouse tongues replicated spontaneous cervical LN metastasis. We performed histological, immunofluorescent, and histomorphometric analyses of tumor-reactive lymphadenopathy and lymphangiogenesis in tumor-associated LNs. We investigated the expression of vascular endothelial growth factor (VEGF)-C and its receptor, VEGF receptor-3 (VEGFR-3), in tumor cells and tissues, and LNs by reverse transcription polymerase chain reaction and immunofluorescence.ResultsTumor-associated LNs comprised sentinel LNs (SLNs) before and after tumor cell invasion (tumor-bearing SLNs), and LNs adjacent or contralateral to tumor-bearing SLNs. Extensive lymphangiogenesis appeared in SLNs before evidence of metastasis. After metastasis was established in SLNs, both LNs adjacent and contralateral to tumor-bearing SLNs demonstrated lymphangiogenesis. Interaction between VEGF-C-positive melanoma cells and VEGFR-3-positive lymphatic vessels was evident in tumor-associated LNs.ConclusionsLN lymphangiogenesis contributes a progression of tumor metastasis from SLNs to other regional LNs.

Highlights

Metastasis via the lymphatic system is promoted by lymphangiogenesis
Tumor-associated Lymph node (LN) enlargement B16F10 melanoma cells reliably underwent metastasis to the tumor-draining cervical LNs following their injection into the tongues of syngeneic C57BL/6 mice (Figure 1) [21]
After metastasis was established in Sentinel lymph node (SLN), lymphangiogenesis expanded to LNs adjacent or contralateral to metastatic SLNs

Summary

Introduction

Alterations of the lymphatic channels during the progression of metastasis to regional lymph nodes (LNs) remain unexplored. To examine whether tumor-induced LN lymphangiogenesis controls metastasis to regional LNs, we investigated cervical LN metastasis in a mouse model of oral melanoma. Tumor cell dissemination to lymph nodes (LNs) through the lymphatic system is common and early event in human malignant tumors. Lymphatic metastasis was considered a passive process, where detached tumor cells entered LNs via pre-existing lymphatic vessels proximate to the primary tumors [2]. LNs to receive cells and fluid from primary tumors through lymphatic vessels [3]. Malignant cells at SLNs were believed to enter the blood stream via high endothelial venules or continue through the lymphatic drainage system, exiting into the blood stream via anastomoses such as the thoracic duct [4]

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Discussion

Conclusion