Prognostic significance of MUC1, MUC2 and MUC5AC expressions in gastric carcinoma

The aim of this study was to investigate the expressions of some of the Mucus Core Proteins (MUC) MUC1, MUC2 and MUC5AC in gastric carcinomas, to assess their prognostic values and their relations with the clinicopathological characteristics.MUC1, MUC2 and MUC5AC expressions were investigated immunohistochemically in 257 patients with gastric carcinomas.MUC1 was strongly expressed in normal gastric epithelium; however, the expression rate decreased with the loss of tumor differentiation (92.6% in well differentiated tumors, 83.7% in poorly differentiated tumors), with an increase in the number of metastatic lymph nodes (98.4% in tumors with no metastatic lymph nodes, 67.9% in tumors with lymph node metastasis-pN3), and with the progression in the tumor stage (100% in stage 1 tumors, 75.6% in stage 4 tumors). MUC1 expression was lower in distant metastatic tumors (83.3% in distant metastatic tumors and 90.8% in nonmetastatic tumors). There was no staining with MUC2 in normal gastric epithelium; however, de novo expressions appeared in tumoral tissues. In diffuse gastric carcinomas (mucinous and signet ring cell carcinomas), MUC2 expression was higher (97.5% in diffuse type and 89.4% in intestinal type). All of the mucinous carcinomas were MUC2-positive. The expression rate decreased with an increase in the number of metastatic lymph nodes and with the progression in the TNM stages of the cases. All of the tumors with intestinal metaplasia were MUC2-positive. MUC5AC was strongly expressed in normal gastric epithelium; however, the expression rate decreased with the loss of tumor differentiation, with an increase in the tumor invasion depth, and with an increase in the number of metastatic lymph nodes. MUC5AC expression was higher in intestinal type carcinoma (48.4%) than in the diffuse type (10%). The lowest expression rate was in the diffuse type according to the Borrmann's macroscopic classification. All of these results were statistically significant (p<0.05).When each of these three markers is evaluated, in the light of clinical and pathological parameters, MUC1 and MUC5AC may be accepted as significant prognostic parameters and may be useful in showing the progression of the tumors; MUC2 may be used in determining the mucinous carcinomas.