HA14-1 potentiates apoptosis in B-cell cancer cells sensitive to a peptide disrupting IP sub(3) receptor / Bcl-2 complexes

• Published in: The International journal of developmental biology Vol. 59; no. 7-9; pp. 391 - 398
• Main Authors: Akl, Haidar, La Rovere, Rita ML, Janssens, Ann, Vandenberghe, Peter, Parys, Jan B, Bultynck, Geert
• Format: Journal Article
• Language: English
• Published: 01.01.2015
• ISSN: 0214-6282; 1696-3547
• DOI: 10.1387/ijdb.150213gb

Anti-apoptotic B-cell lymphoma 2 (Bcl-2) is commonly upregulated in hematological cancers, including B-cell chronic lymphocytic leukemia (B-CLL) and diffuse large B-cell lymphoma (DLBCL), thereby protecting neoplastic cells from oncogenic-stress-induced apoptosis. Bcl-2 executes its anti-apoptotic function at two different sites in the cell. At the mitochondria, Bcl-2 via its hydrophobic cleft interacts with pro-apoptotic Bcl-2 family members to inhibit apoptosis. At the endoplasmic reticulum (ER), Bcl-2 via its Bcl-2 homology (BH)4 domain, prevents excessive Ca super(2+) signals by interacting with the inositol 1,4,5-trisphosphate receptor (IP sub(3) R), an intracellular Ca super(2+)-release channel. A peptide tool (BIRD-2) that targets the BH4 domain of Bcl-2 reverses Bcl-2's inhibitory action on IP sub(3) Rs and can trigger pro-apoptotic Ca super(2+) signals in B-cell cancer cells. Here, we explored whether HA14-1, a Bcl-2 inhibitor that also inhibits sarco/endoplasmic reticulum Ca super(2+)-ATPases (SERCA), could potentiate BIRD-2-induced cell death. We measured apoptosis in Annexin V/7-AAD stained cells using flow cytometry and intracellular Ca super(2+) signals in Fura2-AM-loaded cells using an automated fluorescent plate reader. HA14-1 potentiated BIRD-2-induced Ca super(2+) release from the ER and apoptosis in both BIRD-2-sensitive DLBCL cell lines (SU-DHL-4) and in primary B-CLL cells. BIRD-2-resistant DLBCL cells (OCI-LY-1) were already very sensitive to HA14-1. Yet, although BIRD-2 moderately increased Ca super(2+) levels in HA14-1-treated cells, apoptosis was not potentiated by BIRD-2 in these cells. These results further underpin the relevance of IP sub(3) R-mediated Ca super(2+) signaling as a therapeutic target in the treatment of Bcl-2-dependent B-cell malignancies and the advantage of combination regimens with HA14-1 to enhance BIRD-2-induced cell death.