Constitutive IP3 signaling underlies the sensitivity of B-cell cancers to the Bcl-2/IP3 receptor disruptor BIRD-2

Abstract

Anti-apoptotic Bcl-2 proteins are upregulated in different cancers, including diffuse large B-cell lymphoma (DLBCL) and chronic lymphocytic leukemia (CLL), enabling survival by inhibiting pro-apoptotic Bcl-2-family members and inositol 1,4,5-trisphosphate (IP 3 ) receptor (IP 3 R)-mediated Ca 2+ -signaling. A peptide tool (Bcl-2/IP 3 R Disruptor-2; BIRD-2) was developed to abrogate the interaction of Bcl-2 with IP 3 Rs by targeting Bcl-2′s BH4 domain. BIRD-2 triggers cell death in primary CLL cells and in DLBCL cell lines. Particularly, DLBCL cells with high levels of IP 3 R2 were sensitive to BIRD-2. Here, we report that BIRD-2-induced cell death in DLBCL cells does not only depend on high IP 3 R2-expression levels, but also on constitutive IP 3 signaling, downstream of the tonically active B-cell receptor. The basal Ca 2+ level in SU-DHL-4 DLBCL cells was significantly elevated due to the constitutive IP 3 production. This constitutive IP 3 signaling fulfilled a prosurvival role, since inhibition of phospholipase C (PLC) using U73122 (2.5 µM) caused cell death in SU-DHL-4 cells. Milder inhibition of IP 3 signaling using a lower U73122 concentration (1 µM) or expression of an IP 3 sponge suppressed both BIRD-2-induced Ca 2+ elevation and apoptosis in SU-DHL-4 cells. Basal PLC/IP 3 signaling also fulfilled a pro-survival role in other DLBCL cell lines, including Karpas 422, RI-1 and SU-DHL-6 cells, whereas PLC inhibition protected these cells against BIRD-2-evoked apoptosis. Finally, U73122 treatment also suppressed BIRD-2-induced cell death in primary CLL, both in unsupported systems and in co-cultures with CD40L-expressing fibroblasts. Thus, constitutive IP 3 signaling in lymphoma and leukemia cells is not only important for cancer cell survival, but also represents a vulnerability, rendering cancer cells dependent on Bcl-2 to limit IP 3 R activity. BIRD-2 seems to switch constitutive IP 3 signaling from pro-survival into pro-death, presenting a plausible therapeutic strategy.

MKP1 reduces neuroinflammation via inhibiting endoplasmic reticulum stress and mitochondrial dysfunction

“…Notably, previous studies have argued that inflammation induces mitochondrial division, which is considered mitochondrial fission. Excessive mitochondrial fission causes the uneven distribution of mitochondrial DNA into daughter mitochondria, leading to the inability of mitochondria to produce sufficient ATP (Bittremieux et al, 2019;T. Chen et al, 2018).…”

Creating a New Cancer Therapeutic Agent by Targeting the Interaction between Bcl-2 and IP3Receptors

“…Importantly, the potential value of targeting Bcl-2/IP 3 R interaction using BIRD-2 has been extended in recent studies to nonlymphoid malignancies, including small-cell lung cancer and ovarian cancer (Xie et al 2018). Finally, further recent studies indicate that BIRD-2triggered cytosolic Ca 2+ signals and cell death are critically dependent on the constitutive IP 3 signaling that occurs downstream from the B cell receptor in B cell malignancies (Bittremieux et al 2018a). The cell death induced by BIRD-2 is dependent on Ca 2+ release from the ER via IP 3 Rs, but also requires the presence of extracellular Ca 2+ to maintain the cytosolic Ca 2+ signals to drive cells to point of cell death (Bittremieux et al 2018b).…”

PTEN inhibition attenuates endothelial cell apoptosis in coronary heart disease via modulating the AMPK–CREB–Mfn2‐mitophagy signaling pathway

“…To establish a stable cell line with PTEN deletion, lentiviral vectors of PTEN-siRNAs were infected into HUVECs following the manufacturer's protocols (Kanwar, Yu, & Zhou, 2018). HUVECs were incubated in enhanced infection solution with polybrene and lentivirus (Bittremieux et al, 2019). After 8 hr, the mixture was changed with Dulbecco's modified Eagle's medium (DMEM) medium with 10% FBS for 3 days, the transfection efficiency was identified via observing fluorescence intensity (Kazakov et al, 2018).…”