Glucosylceramide synthase inhibitor PDMP sensitizes chronic myeloid leukemia T315I mutant to Bcr‐Abl inhibitor and cooperatively induces glycogen synthase kinase‐3‐regulated apoptosis

Abstract

Inactivation of glycogen synthase kinase (GSK)-3 has been implicated in cancer progression. Previously, we showed an abundance of inactive GSK-3 in the human chronic myeloid leukemia (CML) cell line. CML is a hematopoietic malignancy caused by an oncogenic Bcr-Abl tyrosine kinase. In Bcr-Abl signaling, the role of GSK-3 is not well defined. Here, we report that enforced expression of constitutively active GSK-3 reduced proliferation and increased Bcr-Abl inhibition-induced apoptosis by nearly 1-fold. Bcr-Abl inhibition activated GSK-3 and GSK-3-dependent apoptosis. Inactivation of GSK-3 by Bcr-Abl activity is, therefore, confirmed. To reactivate GSK-3, we used glucosylceramide synthase (GCS) inhibitor PDMP to accumulate endogenous ceramide, a tumor-suppressor sphingolipid and a potent GSK-3 activator. We found that either PDMP or silence of GCS increased Bcr-Abl inhibition-induced GSK-3 activation and apoptosis. Furthermore, PDMP sensitized the most clinical problematic drug-resistant CML T315I mutant to Bcr-Abl inhibitor GNF-2-, imatinib-, or nilotinib-induced apoptosis by >5-fold. Combining PDMP and GNF-2 eliminated transplanted-CML-T315I-mutants in vivo and dose dependently sensitized primary cells from CML T315I patients to GNF-2-induced proliferation inhibition and apoptosis. The synergistic efficacy was Bcr-Abl restricted and correlated to increased intracellular ceramide levels and acted through GSK-3-mediated apoptosis. This study suggests a feasible novel anti-CML strategy by accumulating endogenous ceramide to reactivate GSK-3 and abrogate drug resistance.

Lactosylceramide Mediates the Expression of Adhesion Molecules in TNF-α and IFNγ-stimulated Primary Cultured Astrocytes

“…Earlier studies reported the involvement of sphingolipids such as ceramide and psychosine in the cytokine-mediated inflammatory disease of CNS, such as Krabbe disease and spinal cord injury [4][5][6][7]. Recent studies showed that PDMP increased imatinib-induced cell death in drug-sensitive and drug-resistant chronic myeloid leukemia cells via enhancing ceramide accumulation [30,31]. These data also suggest the potential utility of inhibiting GSL biosynthesis pathways in CNS disease as well as other diseases.…”

Inhibition of GSK3β by pharmacological modulation of sphingolipid metabolism occurs independently of ganglioside disturbance in a cellular model of Alzheimer's disease

“…However, as our results show, both PDMP enantiomers strongly and equally reduced the ceramide content, specifically the long-chain ceramide species (≤18C), while NB-DNJ did not. At first sight, this could be surprising because D-PDMP is usually described as a ceramide-accumulating agent (Bieberich et al, 1999, Huang et al, 2011, Radin et al, 1993, Takasugi et al, 2015, Yu et al, 2012. Indeed, when blocking the conversion of ceramides to GlcCer, it could be expected that an accumulation of ceramides may have occurred.…”

Major apoptotic mechanisms and genes involved in apoptosis

“…In chronic myeloid leukemia (CML) cell lines, increase in serine palmitoyltransferase levels via BCR/ ABL inhibition result in activation of apoptotic signals [205]. GCS inhibition in CML cell lines bearing T315I mutation results in apoptosis via activating GSK-3 [206]. Another study reported that ceramide triggers apoptosis via activating p38, caspase-8, and c-Jun N-terminal kinase (JNK) in K562 CML cells [207].…”