Further evidence that altered p16/CDKN2 gene expression is associated with lymph node metastasis in squamous cell carcinoma of the esophagus.

Esophageal squamous cell carcinoma (ESCC) has high malignant potential with a poor outcome. Lymph node metastasis is the most useful indicator for predicting the outcome of ESCC. The p16/MTS1/CDKN2 gene and the cyclin D1/PRAD-1 gene cooperatively regulate CDK4-mediated phosphorylation of RB protein in the cell cycle. We immunohistochemically detected p16, cyclin D1, and RB expressions in both primary lesions and metastatic lymph nodes in ESCC. Among the 50 ESCC primary lesions, 24 (48%) were positive for p16, while 26 (52%) were negative for p16. Sixteen (32%) were p16-positive, 34 (68%) were p16-negative among the 50 ESCC metastatic lymph nodes. Eight cases (16%) were p16-positive in primary lesion and p16-negative in lymph node, however, no cases that was p16-negative in the primary tumor exhibited p16-positivity in metastatic lymph nodes (p < 0.0001). Seventeen (34%) of the 50 ESCC primary lesions were cyclin D1-positive, while 33 (66%) were cyclin D1-negative. Twenty-four (48%) were cyclin D1-positive, 26 (52%) were cyclin D1-negative among the 50 metastatic lymph nodes. Five cases (10%) were cyclin D1-positive in primary lesion and cyclin D1-negative in lymph node, and 12 cases (24%) were cyclin D1-negative in primary lesion and cyclin D1-positive in lymph nodes. Nine cases (18%) were RB-negative in 50 primary lesions, and the rate of loss of RB expression in metastatic lymph nodes was not markedly higher than in primary lesions. Thirty-nine (78%) of 50 primary lesions and 46 (92%) of 50 metastatic lymph nodes had altered expression of at least one of the three G1 control genes. Tumor cell with disruption of these cell cycle regulators can get a growth advantage and metastatic potential during tumor progression, especially p16/CDKN2 alterations may be associated with lymph node metastasis in ESCC. These results also suggest that tumor cells in metastatic lymph nodes may have more aggressive proliferation and higher malignant potential than tumor cells in primary lesions.