Purpose: Oral squamous cell carcinoma (OSCC) is a fairly common malignancy in Taiwan and most countries of South Asia due to the popularity of areca quid use. In vitro studies have indicated that Rac proteins, a member of ras-related small GTPase protein family, can regulate cytoskeletal structures and activate signaling cascade and have the potential to transform cultured cells. However, Rac alteration during oral carcinogenesis in vivo has yet to be shown. The present study was conducted to investigate the importance of Rac-1 in oral tumorigenesis in vivo. Patients and Methods: Expression level of Rac-1 protein and mRNA in OSCC together with noncancerous match tissue (NCMT) was explored using immunohistochemistry and reverse transcription-polymerase chain reaction analysis. Results: The immunoreactivity of Rac-1 was shown in a significantly higher fraction of OSCC (74%) relative to the 48% in NCMT (P = .03). Eight of 14 (57%) available tissue pairs also showed overexpression of Rac-1 mRNA in OSCC than that in NCMT. The Rac-1 immunoreactivity did not differ significantly in accord with clinicopathologic parameters including areca quid use. However, 3 of 4 recurrent OSCC studied lacked the Rac-1 immunoreactivity. Conclusions: Our results presented novel findings: Rac-1 overexpression is a frequent occurrence in OSCC, highlighting the involvement of GTPase elements in the neoplastic growth of OSCC.
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