Bcl-2 family of proteins in indolent B-cell non-Hodgkin's lymphoma: study of 116 cases

The bcl-2 family of proteins comprises both antagonists and agonists of apoptosis. We have investigated whether subsets of indolent B-cell non-Hodgkin's lymphoma (IB-NHL) differ in the expression of the bcl-2 family members; 116 cases of IB-NHL, composed of chronic lymphocytic leukemia (CLL, n = 48), follicular lymphoma (FL, n = 38), marginal zone B-cell lymphoma (MZBCL, n = 15), and mantle cell lymphoma (MCL, n = 15), were investigated for expression of bcl-2, bcl-X, mcl-1, bax, and bak proteins by immunohistochemistry. Expression of bcl-2 and bcl-X proteins was moderate/high among most IB-NHLs. Expression of mcl-1 was low/absent in most cases of CLL and MCL and low/moderate in most cases of FL and MZBCL. Most MCLs did not express bax protein. Bax expression was absent/low among most cases of CLL and low/moderate among most cases of FL and MZBCL. Expression of bak was moderate/low among most cases of CLL, MZBCL, and MCL but was absent/low among most cases of FL. The different subsets of IB-NHLs differ in their expression of mcl-1, bax, and bak proteins.