Correlation between apoptosis, proliferation and bcl-2 expression in malignant non-Hodgkin's lymphoma.

Aim-To investigate whether clinical features of non-Hodgkin's lymphomas, at the time of first biopsy, correlate with studies of cell proliferation and cell death as well as with the level of bcl-2 expression.Methods-Bcl-2 expression, determined by immunocytochemistry, was compared with cell proliferation, measured using in situ hybridisation for histone mRNA, and cell death by apoptosis, measured using in situ end labelling for DNA cleavage.Results-Histone mRNA staining gave a labelling index of 30% of cells for reactive germinal centres, 5.2-13.5% of cells for low grade non-Hodgkin's lymphoma and 12.1-50.5% of cells for high grade non-Hodgkin's lymphoma. In situ end labelling gave a labelling index of 5.0-10.0% of cells for reactive germinal centres, 1.0-3.7% of cells for low grade non-Hodgkin's lymphoma and 4.7-13.5% of cells for high grade non-Hodgkin's lymphoma. There was a positive correlation between apoptotic index and proliferation index. More cases of low grade than high grade non-Hodgkin's lymphoma expressed bcl-2. There was no correlation between apoptotic index and bcl-2 expression for high grade non-Hodgkin's lymphoma.Conclusions-The molecular mechanisms controlling cell proliferation and death in non-Hodgkin's lymphoma are complex, probably involving a range of genes, including bcl-2. A better understanding of resistance to cell death is needed if the clinical goal of tailoring cancer treatment to individual tumours is to be achieved.