Expression and significance of RKIP and E-cadherin in lung squamous cell carcinoma

The purpose of this study was to investigate the expression of Raf kinase inhibitor protein (RKIP) and epithelial cadherin (E-cadherin) in lung squamous cell carcinoma tissue and its correlation with the clinical pathology of lung squamous cell carcinoma. RKIP and E-cadherin mRNA (by RT-PCR) and protein (by western blotting) levels were monitored in carcinoma tissues and surrounding normal tissues from 86 lung squamous cell carcinoma cases, and their positive rates were calculated. The rates of positive RKIP and E-cadherin mRNA expression were significantly lower in lung squamous cell carcinoma than in the surrounding normal tissues (P < 0.05). The positive expression rates were significantly lower in those with lymph node metastasis than in those without (P < 0.05). The lower the degree of tumor differentiation, the lower the E-cadherin mRNA positive expression rate (P < 0.05). The rates of positive RKIP and E-cadherin mRNA expression were significantly lower in patients at advanced (III, IV) stages than in patients at early (I, II) stages (p < 0.05); this rate, however, was independent of gender, age, and tumor size (P > 0.05). The protein levels of RKIP and E-cadherin were significantly lower in lung squamous cell carcinoma than in the surrounding normal tissues (P < 0.05). The levels were significantly lower in patients with lymph node metastasis than in those without it (P < 0.05). The lower the degree of tumor differentiation, the lower the protein level of E-cadherin (P < 0.05). Both RKIP and E-cadherin are tumor suppressors, their low expression levels may be associated with initiation, invasion and/or metastasis, as well as with the inhibition of lung squamous cell carcinoma differentiation.