Poster Presentation 14th International Biennial Conference on Metastasis Research 2012

3D quantitative analysis of local invasiveness and lymphovascular dissemination of human oral squamous cell carcinoma xenografts in mouse tongue microenvironment (#123)

Yoshihito Shimazu 1 , Yuuichi Soeno 1 , Kazuya Fujita 1 , Yuji Taya 1 , Kayo Nakau 1 , Kaori Sato 1 , Takaaki Aoba 1
  1. Department of Pathology, School of Life Dentistry at Tokyo, Nippon Dental University School of Life Dentistry at Tokyo, Tokyo, Japan

Squamous cell carcinoma (SCC) in tongue exhibits aggressive progression and early-stage lymphnode metastasis. The present study aimed at elucidating a putative linkage between SCC cell phenotypes and lymphovascular metastasis in a mouse xenograft model. Five tongue and oral floor-derived SCC cell-lines (OSC19, OSC20, HSC2, KOSC2, HO-1u1) were used. Each cell-line grown in culture was transplanted into BALB/c nude mouse tongue. Phenotypic plasticity of SCC cells with growth of primary xenograft tumors and nodal metastasis were examined immunohistochemically. We also conducted 3D reconstruction of the primary tumors using serial histological images to assess quantitatively the local invasiveness of SCC cells, the density of blood/lymphatic vasculature, and the location and frequency of lymphovascular tumor invasion. All five cell-lines gave rise to visible tumor masses in the tongue within 2-3 weeks, but individual tumor cells showed diversities in Ki67-positive proliferation activity, intra- and peritumor vascular densities, and EMT-like phenotypes. 3D visualization of the primary tumor architecture disclosed discrete invasion modes from massive growth with pushing border (OSC20, OSC19) to branching (HSC2, KOSC2) and fingering infiltration (HO-1u1). EMT-like cells showing loss of E-cadherin and up-regulation of vimentin accumulated at the peripheral region of tumor mass, resulting in segregation of individual tumor cells from mother cell population, although lymphovascular invasion by single and/or a few EMT-like cells were only occasionally seen. In contrast, the majority of lymphovascular invasion took place in a form of penetration of cohesive tumor cell clusters through the lymphatic vessel wall, giving rise to large tumor emboli retaining epithelial phenotypes (cytokeratins and E-cadherin) and Ki67-positive proliferation activity. Similar SCC phenotypes including persistent E-cadherin expression were also seen in nodal metastasis. The results indicate that EMT-like phenotypic plasticity of SCC cells is responsible for their local invasive properties but not prerequisite for lymphovascular dissemination.