Significance of retinoblastoma and mdm2 gene expression as prognostic markers for soft-tissue sarcoma

The growth regulatory function of the retinoblastoma protein (RB) can be suppressed by mdm2 via RB/mdm2 interaction by perturbation of the RB suppression of the E2F function. The goal of this study was to examine the clinical value of immunohistochemical (IHC) RB detection and its relationship to mdm2 overexpression in a cohort of 198 adult primary soft-tissue sarcomas (STS). RB overexpression reveals, multivariately, a correlation with survival (RR=1.59, P=0.037) as well as mdm2 positivity (RR=2.32, P=0.0035). Stratification of RB results to mdm2 staining shows a prognostic graduation in four levels. Patients with positivity for both antibodies have the highest risk (RR=3.30, P=0.002) and the poorest prognosis (projected 5-year survival rate, 18.6%); those with negativity for both antibodies show the most favourable prognosis (projected 5-year survival rate, 63.4%). Intermediately, an isolated RB overexpression (projected 5-year survival rate, 46.1%) is more favourable than an isolated mdm2 positivity (projected 5-year survival rate, 33.5%). To sum up, this study proves that RB and mdm2 overexpression have an individual and also an additive effect on prognosis in STS.