Retinoblastoma Gene Product and P21 (WAF1, CIP1) Protein Expression in Non Hodgkin's Lymphomas: A Multivariate Survival Analysis

Abstract

We evaluated immunohistochemically the expression of two negative regulators of the cell cycle, namely retinoblastoma gene product (pRb) and WAF1/Cip1 gene product (p21), in paraffin sections from 93 patients with non-Hodgkin's lymphomas (NHL) and related it to clinicopathological parameters, proliferative fraction, p53 expression and survival. Patients were followed until death (n=33) or for an average of 52 months (60–160). Rb labelling index (LI) increased with malignancy grade and proliferative activity but was unrelated to other clinicopathological parameters. In 33% of cases, especially those of the aggressive groups, we observed diminished pRb expression (i.e. low pRb/Ki-67 ratio). p21 expression on the other hand correlated only with histological grade, Rb LI and p53 LI. In multivariate analysis, Rb LI was a negative predictor of disease-free survival but was linked to a higher probability of complete response. However, diminished pRb expression as well as p21 expression were not statistically significant prognostic indicators. Our results suggest that pRb as a cell cycle related molecule may play an important role in determining prognosis and therapeutic response in NHL patients.

Key Words:

• NHL
• retinoblastoma gene product
• pRb
• p21 protein
• WAF1
• Cip1