Summary.-Lewis lung carcinoma cells were implanted in the foot-pads of mice and the effects of the plasminogen-plasmin inhibitor tranexamic acid (t-AMCHA) and of the plasminogen activator urokinase on metastasis were examined by electron microscopy. The intravascular tumour cells were not associated with thrombus formation in either control or urokinase -treated mice. Polymerized fibrin deposition around tumour cells and thrombi composed of fibrin and platelets was observed only in the mice given t-AMCHA. This suggests that the inhibition of fibrinolysis by tACC caused fibrin deposition and thrombus formation around intravascular tumour cells, which prevented release of the cells from primary foci to form secondary tumours. On the other hand, fibrinolysis induced by urokinase prevented thrombus formation, and accelerated cell release from primary foci.

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Head and neck cancer is one of the most common cancers worldwide, and an innovating therapy is awaited. We attempted to identify proteins associated with cancer stem cell phenotypes, and found an EF-hand protein S100A10 is highly expressed in the stem cell population. Together with its binding partner, Annexin-A2, S100A10 regulates a spectrum of dynamic membrane-related events, such as actin cytoskeleton control, vesicle formation and intercellular interaction. Immunohistochemical analysis using clinical head and neck cancer specimens showed that elevated S100A10 expression is typically present in the invasion front of tumors, and S100A10-high cases were associated with poor prognosis. S100A10 knockdown and knockout resulted in significant reduction of cell migration and invasion in vitro. Cell movement was slowed down by S100A10 knockdown. Accordingly, in vivo tumor formation was impaired by S100A10 depletion. Cell cycle progression was delayed by the depletion, suggesting its potential role in proliferation controls. These results suggest that S100A10 has a significant role in head and neck cancer cell proliferation and invasion. Citation Format: Nobuyukit Tanaka, Taketo Nishikawaji, Naoko Ogama. S100A10 contributes to cancer stemness, invasion and metastasis of head and neck cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1109.