Bcl-2 family gene modulation during spontaneous apoptosis of B-chronic lymphocytic leukemia cells.

Malignant cell accumulation in B-cell chronic lymphocytic leukemia (B-CLL) is primarily caused by defective apoptosis rather than increased proliferation. To further understand the role of Bcl-2 family members, known regulators of apoptosis, in the abnormal B-CLL survival, we have measured their mRNA levels in fresh B-CLL cells and in cultures undergoing spontaneous apoptosis. Using RNA protection assays we found constitutive expression of most bcl-2 members with high levels of bcl2, bcl-w, bad, bak, bax, and the bcl-2/bax ratio, compared to normal PBL.

Involvement of p53 in alpha4beta1 integrin-mediated resistance of B-CLL cells to fludarabine.

We recently showed that alpha4beta1 integrin induces B-cell chronic lymphocytic leukemia (B-CLL) cell resistance to fludarabine-induced apoptosis via upregulation of Bcl-xL. We have now studied whether p53 was involved in this response. Cells from five B-CLL patients with wild-type p53 determined by DNA sequencing, or from the EHEB cell line, cultured on the alpha4beta1 ligand H/89 during fludarabine treatment, showed significantly higher viability (P View Article and Find Full Text PDF

Engagement of alpha4beta1 integrin by fibronectin induces in vitro resistance of B chronic lymphocytic leukemia cells to fludarabine.

B-cell chronic lymphocytic leukemia is characterized by the accumulation of malignant B lymphocytes as a result of abnormal survival signals operating in vivo. Previously, we showed that adhesion of B-CLL cells to the fibronectin fragment H89, a ligand for alpha4beta1 integrin, prevents their spontaneous apoptosis in vitro. We have now studied whether alpha4beta1/H89 interaction affected the response of B-CLL cells to the therapeutic drug fludarabine.