[Methylation and expression of gene p16INK4a and RB in gastric carcinomas]

To investigate the promoter methylation status of gene p16INK4a and RB and their expressions at protein level in gastric carcinomas, and their correlation with clinical and pathological parmeters.

A series of 81 gastric carcinomas and 10 normal gastric tissues was examined for the promoter methylation of p16INK4a or RB by methylation-specific PCR method. The expression of p16INK4a and pRb was detected by immunohistochemistry.

Methylation of p16INK4a and RB was found in 37% (30/81) and 42% (34/81) of gastric carcinomas, respectively, and positive immunostaining for p16INK4a and pRb was detected in 54% (44/81) and 90% (73/81) of the tumors, respectively. In addition, promoter methylation of p16INK4a was significantly associated with negative immunostaining of p16INK4a (P < 0.001), but was not associated with differentiation status, lymph node metastasis, sex and age. RB methylation was not correlated with pRb expression, differentiation status, sex and age, but was associated with lymph node metastasis.

Methylation of p16INK4a or RB is a common event in gastric carcinomas and may play a role in the development of gastric carcinomas. Methylation of RB is correlated with lymph node metastasis, suggesting that RB methylation may predict lymph node metastasis. Promoter methylation of p16INK4a is an important mechanism for its inactivation.