Distribution of Collagen Type IV α1-6 Chains and MMP in Carcinogenesis in Oral Squamous Cell Carcinoma

Destruction of basement membrane is an important element in invasion of cancer cells. Type IV collagen, the major component of basement membrane, has six distinct a chains. Matrix metalloproteinases (MMPs) are enzymes that resolve extracellular matrix. Oral squamous cell carcinoma occurs through precancerous lesion epithelial dysplasia and carcinoma in situ. We investigated localization of six a chains and MMPs in normal oral mucosal tissue, precancerous lesions, early squamous cell carcinoma immunohistochemically. In normal oral mucosal tissue and epithelial dysplasia, α1 (IV), α2 (IV), α5 (IV) and α6 (IV) chains were detected continuously along basement membrane. In carcinoma in situ and early squamous cell carcinoma, either α5 (IV) and α6 (IV) chains or all a chains were not stained. In contrast, MMP-2 and MMP-9 that are members of type IV collagenase were stained at the parts of disappearance of a chains. This study suggested that the disappearance of a chains is an important element in carcinogenesis of oral squamous cell carcinoma.