Metallopanstimulin / S27 Ribosomal Antigen Expression in Stages I and II Breast Cancer: its Relationship with Clinicopathologic Factors.

Metallopanstimulin (MPS-1)/S27 ribosomal protein is involved in cellular proliferation and oncogenesis. In this study, we have examined the expression of the MPS-1 protein in 120 stages I and II breast carcinomas to study its relationship with breast cancer prognosis. We also determined if there was any relationship of MPS-1 with other biological markers commonly used in breast cancer prognosis. The expression of MPS-1 protein was analyzed by immunohistochemistry using specific anti-MPS-1 antibodies. We found that there was greater expression of MPS-1 in tumors of greater size and in higher histological grades. Thus, in tumors with more histological aggressiveness there is more MPS-1. Both were frequently associated with a greater proliferative activity. There was also a significant association between the expression of MPS-1 with the expression of receptors for progesterone (p=0.004), estrogens (p=0.03), bcl-2 (p=0.002), and MIB-1 (p=0.03). After univariate logistic regression analysis, we found that overexpression of MPS-1 correlated with Disease Free Survival (DFS) (p=0.039), showing that MPS-1 positivity is associated with a greater incidence of recurrence and/or metastasis. There was no association between overexpression of MPS-1 and poor Overall Survival (OS) (p=0.146). The results presented here indicate a significant correlation between overexpression of MPS-1/S27 ribosomal protein and more aggressive breast cancer growth. These results suggest that the MPS-1 antigen may be a useful marker to understand better the biological behavior of breast cancer.