Expression of the RNA-binding protein IMP1 correlates with poor prognosis in ovarian carcinoma.

The IMP (IGFII mRNA-binding protein) family comprises a group of three RNA-binding proteins involved in the regulation of cytoplasmic mRNA-fate. Recent studies identified IMP proteins as oncofetal factors in various neoplasias, but knowledge of a potential role in ovarian carcinomas is still lacking. The immunohistochemical analysis of 107 ovarian carcinomas, 30 serous borderline tumors of the ovary and five normal ovaries revealed de novo synthesis of IMP1 in 69% of ovarian carcinomas. Elevated IMP1 expression was observed preferentially in high-grade and high-stage cases and was a significant prognostic indicator for reduced recurrence-free and overall survival. Phenotypic studies in ovarian carcinoma-derived ES-2 cells demonstrated that IMP1 knockdown affects proliferation and cell survival. Reduced proliferation was associated with decreased c-myc mRNA half-life, suggesting IMP1 as an oncogenic factor that is involved in promoting elevated proliferation by stabilizing the c-myc mRNA in ovarian carcinoma cells.