Claudin-1 expression in squamous cell carcinomas of different organs: comparative study of cancerous tissues and normal controls.

Claudins are the main sealing proteins of the intercellular tight junctions and play an important role in cancer cell progression and dissemination. This study examined and compared the expression of claudin-1 by immunohistochemistry in 60 squamous cell carcinomas of different tissue types and normal 33 controls, arranged in 2 tissue microarray slides. A score was generated to classify claudin-1 expression into negative, low, medium, and high. Most squamous cell carcinomas (91.67%) showed positive membranous staining. Medium to high claudin-1 expression was prevalent in carcinomas from the head-neck, skin, and genitourinary regions and was less frequent in other locations. An inverse correlation was noted between claudin-1 expression and tumor grade in tumors of the genitourinary and breast-gynecologic regions. Of the normal organs, significant claudin-1 expression was present mainly in the skin whereas other epithelial tissues had only minimal to low expression levels. Claudin-1 expression in squamous cell carcinoma varies in organ-specific manner reflecting influence of local factors and different mechanisms of claudin-1 expression. Knowledge of this fact is important in planning biologic therapy targeting claudin-1.