Involvement of c-Jun NH2-Terminal Kinase Activation and c-Jun in the Induction of Apoptosis by the Ether Phospholipid 1-O-Octadecyl-2-O-methyl-rac-glycero-3-phosphocholine

Abstract

The ether phospholipid 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3; edelfosine) is a potent inducer of apoptosis in human tumor cells. We show that ET-18-OCH3-induced apoptosis is associated with activation of the c-Jun NH2-terminal kinase (JNK) signaling. The addition of ET-18-OCH3 to distinct human leukemic cells (HL-60, U937, and Jurkat), which undergo rapid apoptosis on treatment with ET-18-OCH3, induced a dramatic and sustained increase in the of c-jun mRNA level that was associated with activation of activator protein-1 transcription factor. We found that ET-18-OCH3 induced a persistent activation of JNK in HL-60 cells that was detected before the onset of apoptosis, the latter being assessed by DNA fragmentation and by the appearance of phosphatidylserine on the external leaflet of the plasma membrane. The inductions of JNK after HL-60 monocyte/macrophage differentiation and ET-18-OCH3-mediated apoptosis were distinguished by the different activation patterns, transient versus persistent, respectively. ET-18-OCH3 analogues unable to induce apoptosis failed to activate JNK. ET-18-OCH3-dependent JNK activation was not detected in K562 cells, which did not undergo apoptosis on treatment with ET-18-OCH3. Phorbol myristate acetate inhibited both ET-18-OCH3-induced apoptosis and sustained JNK activation; thus, persistent JNK activation by ET-18-OCH3 is associated with the capacity of this ether phospholipid to induce apoptosis. Furthermore, antisense oligonucleotides directed against c-jun blocked ET-18-OCH3-induced apoptosis, indicating a role for c-Jun in this apoptotic response. These data indicate that JNK activation and c-Jun are involved in the induction of apoptosis by ET-18-OCH3.

Proapoptotic role of Hsp90 by its interaction with c-Jun N-terminal kinase in lipid rafts in edelfosine-mediated antileukemic therapy

“…Previous studies have shown a critical role for persistent JNK activation in EDLF-mediated apoptosis (Gajate et al, 1998;Ruiter et al, 1999), EDLF being a rapid and potent JNK activator (Gajate et al, 1998;Ruiter et al, 1999) as well as a strong inducer of c-jun upregulation in leukemic cells (Mollinedo et al, 1994).…”

“…Because Hsp90 and JNK were recruited in lipid rafts, and EDLF-induced apoptosis is dependent on sustained JNK activation (Gajate et al, 1998;Ruiter et al, 1999), we hypothesized that Hsp90 might interact with unusual client proteins when present in a new scenario, favoring apoptosis and JNK activation. Persistent JNK activation is associated with apoptosis, whereas transient JNK activation is linked to proliferating and differentiating responses (Chen et al, 1996).…”

“…This has led to the notion that Fas/CD95 concentration in lipid rafts is a novel mode of action for anti-cancer drugs and a potential target in cancer chemotherapy . In addition, EDLF-induced apoptosis is mediated by c-Jun N-terminal kinase (JNK) persistent activation (Gajate et al, 1998;Ruiter et al, 1999).…”

Antitumor alkyl-lysophospholipid analog edelfosine induces apoptosis in pancreatic cancer by targeting endoplasmic reticulum

“…At 20 mM, we found that ALPs ranked edelfosine>perifosineberucylphosphocholineXmiltefosine in their capacity to induce apoptosis in the pancreatic BxPC-3, Capan-2, CFPAC-1 and HuP-T4 cancer cells (Figure 1b). We included in our analysis the structurally related inactive edelfosine analog 1-O-octadecylrac-glycero-3-phosphocholine (ET-18-OH) (Mollinedo et al, 1997;Gajate et al, 1998), in which the methoxy group in the sn-2 position was replaced by an OH group. We found that, unlike edelfosine and perifosine, the other ALPs rendered low figures of apoptosis similar to ET-18-OH (Figure 1b).…”

“…Protein kinase assays were carried out using a fusion protein between glutathione S-transferase and c-Jun (amino acids 1-223) as a substrate of JNK, as previously described (Gajate et al, 1998(Gajate et al, , 2000a.…”