title: HA14-1 potentiates apoptosis in B-cell cancer cells sensitive to a peptide disrupting IP 3 receptor / Bcl-2 complexes.
abstract: 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(2+) signals by interacting with the inositol 1,4,5-trisphosphate receptor (IP3R), an intracellular Ca(2+)-release channel. A peptide tool (BIRD-2) that targets the BH4 domain of Bcl-2 reverses Bcl-2's inhibitory action on IP3Rs and can trigger pro-apoptotic Ca(2+)signals in B-cell cancer cells. Here, we explored whether HA14-1, a Bcl-2 inhibitor that also inhibits sarco/endoplasmic reticulum Ca(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(2+) signals in Fura2-AM-loaded cells using an automated fluorescent plate reader. HA14-1 potentiated BIRD-2-induced Ca(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(2+) levels in HA14-1-treated cells, apoptosis was not potentiated by BIRD-2 in these cells. These results further underpin the relevance of IP3R-mediated Ca(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.
authors.affiliation: KU Leuven, Lab. Molecular and Cellular Signaling, Dept. Cellular and Molecular Medicine, Leuven, Belgium.
authors.forename: Haidar
authors.initials: H
authors.lastname: Akl
authors.forename: Rita M L
authors.initials: RM
authors.lastname: La Rovere
authors.forename: Ann
authors.initials: A
authors.lastname: Janssens
authors.forename: Peter
authors.initials: P
authors.lastname: Vandenberghe
authors.forename: Jan B
authors.initials: JB
authors.lastname: Parys
authors.forename: Geert
authors.initials: G
authors.lastname: Bultynck
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D001578:Benzopyrans / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D016403:Lymphoma, Large B-Cell, Diffuse / Q000378:metabolism / Q000473:pathology*; D009570:Nitriles / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*
chemical_list: C000595707:BCL2 protein, human; D001578:Benzopyrans; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009570:Nitriles; D019253:Proto-Oncogene Proteins c-bcl-2; C456800:ethyl 2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate