Incidence of apoptosis and cell proliferation in multiple myeloma - Correlation with bcl-2 protein expression and serum levels of interleukin-6 (IL-6) and soluble IL-6 receptor

We evaluated the in vivo incidence of apoptosis and cell proliferation in multiple myeloma (MM) and investigated the correlation of both cellular events with histological tumour stage and grade, bcl-2 protein expression, serum IL-6 and sIL-6R. Material and methods: The TUNEL method was used to assess apoptosis and immunohistochemistry to assess the expression of proliferating cell nuclear antigen (PCNA) and bcl-2 protein in 30 bone marrow biopsy specimens. The apoptotic index (AI) and proliferative index (PI) were defined as the percentage of TUNEL and PCNA positive plasma cells, respectively. Results: The mean AI was 0.162% and the mean PI 27.44%. A positive correlation between AI and PI was found (r=0.44, P=0.017). PI was also correlated with tumour grade (P=0.015). The mean bcl-2 protein expression was 70% and did not correlate with AI or PI, but was higher in specimens taken at first diagnosis than in specimens taken after response to treatment (P=0.035). The mean serum IL-6 and sIL-6R values were 9.43 pg mL(-1) and 47.27 ng mL(-1), respectively. These parameters did not correlate with AI or PI. Conclusions: The results indicate that MM might be among the malignancies with very low incidence of apoptosis. Proliferative activity increased in parallel with tumour histological grade. A positive correlation between apoptosis and proliferation was observed, but the incidence of these two cellular events seems not to be related to the bcl-2 protein expression and the serum levels of IL-6 and sIL-6R