Expression of RCAS1 is significantly associated with the progression and prognosis of oral squamous cell carcinomas in Taiwan

This study used an immunohistochemical technique to examine the expression of receptor-binding cancer antigen expressed on SiSo cells (RCAS1) in 84 specimens of oral squamous cell carcinoma (OSCC), 106 specimens of oral epithelial dysplasia (OED, 32 mild, 44 moderate, and 30 severe OED cases), and 20 specimens of normal oral mucosa (NOM). We found that the mean RCAS1 labeling indices (LIs) increased significantly from NOM (12 ± 5%) through mild OED (31 ± 13%), moderate OED (44 ± 17%), and severe OED (56 ± 18%) to OSCC samples (68 ± 20%, p < 0.001). A significant correlation was found between the higher mean RCAS1 LI and OSCCs with larger tumor size (p = 0.001), positive lymph node metastasis (p < 0.001), or more advanced clinical stages (p < 0.001). Positive lymph node metastasis (p = 0.0073) and RCAS1 LI ≧ 60% (p = 0.048) were identified as independent unfavorable prognosis factors by multivariate analyses with Cox regression model. Kaplan-Meier curve showed that OSCC patients with a RCAS1 LI ≧ 60% had a significantly poorer cumulative survival than those with a RCAS1 LI < 60% (log-rank test, p = 0.0113). We conclude that the expression of RCAS1 is an early event in oral carcinogenesis. The RCAS1 LI in OSCC samples can predict the progression of OSCCs and the survival of OSCC patients.