High-grade malignant non-Hodgkin's lymphomas differ from low-grade lymphomas in the extent of apoptosis and their expression of bcl-2, mcl-1, bax and p53

Abstract

In this study, we investigated the extent of apoptosis in 82 non-Hodgkin's lymphoma and 4 reactive follicular hyperplasias and correlated the findings with the extent of apoptosis as determined by the 3'-end labelling method of the apoptotic DNA. To study the influence of apoptosis-regulating proteins bcl-2, bax, mcl-1 and p53 on the extent of apoptosis, we also immunostained the samples with antibodies to them. The results show that there is a significant difference in the extent of apoptosis between low- and high-grade non-Hodgkin's lymphomas, the latter on average showing considerably more apoptotic cells (0.38 +/- 0.30 and 1.44 +/- 1.35%, respectively; p = 0.001). In line with this difference, high-grade lymphomas had significantly more cases with a weak expression of bcl-2 and strong expression of bax (p = 0.00008 and p = 0.016, respectively). They also showed significantly more cases with a positive p53 immunoreactivity (p < 0.00001) and strong mcl-1 immunoreactivity (p = 0.018). The results suggest that apoptosis-affecting genes bcl-2, bax, mcl-1 and p53 all take part in the regulation of apoptosis in malignant non-Hodgkin's lymphomas and contribute to a different level of apoptosis between high- and low-grade non-Hodgkin's lymphomas.