Background and objectives: Fatty acid binding protein 4 (FABP4) is an intracellular lipid chaperone molecules that are expressed and involved in functions of adipocyte, macrophage, and dendritic cell. However, little is known about the expression and role of FABP4 on tumor cells, especially squamous cell carcinoma (SCC). We, therefore, investigated the expression and the role of FABP4 in human SCC of tongue.
Methods: Samples of SCC located in the tongue were obtained from surgical resection tissue specimens at Osaka University Dental Hospital with informed consent. The patients, who received no therapy including chemotherapy and irradiation, were randomly selected. The expression of FABP4 within tissues was detected by a FABP4-specific polyclonal antibody using standard immunohistochemical technique. To clarify the role of FABP4 on SCC, we designed FABP4-specific small interfering RNA (siRNA) and applied it to cultured SCC cell line, SAS, established from human tongue SCC.
Results: Ectopic expressions of FABP4 were observed in tumor areas of SCC primary tissues on all cases. In contrast, the expressions of FABP4 were slightly observed in non-tumor areas of same tissue sections. Statistically significant difference of FABP4 expression between the tumor and non-tumor areas was confirmed. In vitro study using cultured tumor cell line, the suppression of FABP4 expression by siRNA caused the inhibition of cell growth, resulted in the decrease in the number of adherent living cells of SCC.
Conclusions: It is suggested that the ectopic expression of FABP4 in tumor cells of human tongue SCC may play an important role on cell growth of human SCC.
Key words: fatty acid binding protein 4; squamous cell carcinoma; cellular proliferation