Reduced expression of CD9 in oral squamous cell carcinoma: CD9 expression inversely related to high prevalence of lymph node metastasis

Because CD9 is implicated in cell growth, cell adhesion and cell motility, altered CD9 expression might be involved in cancer invasion and metastasis. We have studied the immunolocalization of CD9 in oval squamous cell carcin oma (SCC). Sections prepared from paraffin-embedded specimens from patients with SCC of the oral cavity were stained with a monoclonal anti-CDS antibo dy by means of the streptoavidin biotin method. Significant reduction or co mplete loss of CD9 expression was observed in cancer cells at the periphery of the cancer nests in the advancing front of invading tumor. Among 78 cas es of oral SCCs examined, 46 (59.0%) cases were completely negative for CD9 expression. Loss of CD9 expression in cancer tissue strongly correlated wi th a high incidence of cervical lymph node metastasis and poorer prognosis (P=0.001). Thus a close examination of CD9 in SCC tissue would be useful fo r the prognosis of patients with oral carcinoma.