Bcl-2, Bax and p53 expression in B-CLL in relation to in vitro survival and clinical progression

Abstract

Our previous data have shown that isolated leukemic cells from progressive chronic lymphocytic leukemia (B-CLL) patients respond to growth stimulation in vitro and express high levels of p53, immunoreactive with the configuration-specific antibody PAb 240. We have now analyzed the in vitro survival of B-CLL cells in relation to Bcl-2, Bax alpha and p53 expression and compared this with the clinical progression of the disease. Leukemic cells from patients with progressive disease demonstrated higher in vitro survival, compared with non-progressive B-CLL and normal B cells. All cells were sensitive to treatment with a combination of glucocorticoid and cAMP. Bcl-2 protein levels were not related to clinical progression, as measured by flow cytometry. Competitive PCR showed that Bcl-2 mRNA was over-expressed in most of the B-CLL samples and that p53 mRNA expression was similar between B-CLL groups and normal values and thus not related to clinical progression. However, since Bax alpha expression was lower in progressive than in non-progressive patients, the Bcl-2/Bax alpha ratio at the mRNA level was significantly higher in the progressive group. Our data suggest that the Bcl-2/Bax alpha ratio is important for the regulation of B-CLL cell survival, that p53 over-expression in progressive B-CLL is the result of post-transcriptional modifications and that a directed PKA activation may potentiate the cytolytic effect of glucocorticoids in vivo.