Abstract 4444: The role of small GTPase Rab7 in the secretion of extracellular microvesicles by head and neck squamous cells carcinoma

Abstract

Abstract Head and neck squamous cell carcinoma (HNSCC) is an epithelial malignant tumor that shows its highest incidence in the upper aerodigestive tract and is considered one of the six most common malignancies worldwide. Among the processes involved in the poor prognosis of HNSCC, local invasion and subsequent metastasis are the most important events. Recent evidences have shown that metastasis can be the result of extracellular microvesicles (MVEs) being released from the tumor cells to the blood or lymphatic system. The molecular mechanisms involved in MVEs biogenesis and secretion are, however, poorly understood. Herein, we have performed a screen targeting for the components of MVEs biogenesis in three HNSCC cell lines (SCC-9, Cal27 and FaDu) through western blotting. MVEs were quantified using Nanoparticle Tracking Analysis (NTA - NanoSight®) and the lysosomal compartment was followed in the cell lines through immunofluorescence. Comparing the three cell lines, FaDu cells presented higher expression of proteins responsible for MVEs formation (p<0.05), such as Flotilin-1, Tsg101, VPS36 and also Rab7, a small GTPase that directs vesicles to lysosomes. However, FaDu cells secreted less MVEs than SCC-9 and Cal27. Immunofluorescence experiments showed the presence of numerous perinuclear clusters positive to LAMP-1 (lysosome marker) in FaDu cells, while SCC-9 and Cal27 showed LAMP1-positive organelles dispersed throughout their cytoplasms. Taken together, the results highlight a role for Rab7 protein in the negative regulation of MVEs secretion by HNSCC cell lines, which may provide important information related to tumor progression, treatment response, and especially the development of metastasis. Supported by São Paulo Research Foundation (FAPESP) Citation Format: Fernanda S. Giudice, Bruna R. Rodrigues, Marcos V. S. Dias, Antuani R. Baptistella, Tonielli Cristina S. Lacerda, Luiz P. Kowalski, Vilma R. Martins. The role of small GTPase Rab7 in the secretion of extracellular microvesicles by head and neck squamous cells carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4444. doi:10.1158/1538-7445.AM2014-4444