Activation of CD95 (APO-1/Fas) signaling by ceramide mediates cancer therapy-induced apoptosis

Abstract

We report here that anticancer drugs such as doxorubicin lead to induction of the CD95 (APO‐1/Fas) system of apoptosis and the cellular stress pathway which includes JNK/SAPKs. Ceramide, which accumulates in response to different types of cellular stress such as chemo‐ and radiotherapy, strongly induced expression of CD95‐L, cleavage of caspases and apoptosis. Antisense CD95‐L as well as dominant‐negative FADD inhibited ceramide‐ and cellular stress‐induced apoptosis. Fibroblasts from type A Niemann–Pick patients (NPA), genetically deficient in ceramide synthesis, failed to up‐regulate CD95‐L expression and to undergo apoptosis after γ‐irradiation or doxorubicin treatment. In contrast, JNK/SAPK activity was still inducible by doxorubicin in the NPA cells, suggesting that activation of JNK/SAPKs alone is not sufficient for induction of the CD95 system and apoptosis. CD95‐L expression and apoptosis in NPA fibroblasts were restorable by exogenously added ceramide. In addition, NPA fibroblasts undergo apoptosis after triggering of CD95 with an agonistic antibody. These data demonstrate that ceramide links cellular stress responses induced by γ‐irradiation or anticancer drugs to the CD95 pathway of apoptosis.

Stress signals for apoptosis: ceramide and c-Jun kinase

“…Stresses and cytokines may initiate signaling through the JNK cascade via receptor-associated adaptor molecules, SMase-mediated ceramide generation, or unknown mechanisms. JNK activation results in transcriptional upregulation of pro-apoptotic TNF superfamily members (Herr et al, 1997;Debatin, personal communication), but may also act directly to phosphorylate and inactivate Bcl-2 to promote apoptosis. Ceramide can also signal transcriptionally-independent apoptosis through mitochondria dysfunction, which, in one report, occurs by suppression of Akt kinase via a pathway regulated through Ras and Raf-1…”

“…In some instances, ceramide generation and JNK activation may occur independently yet act coordinately to signal apoptosis. In this regard, Debatin and co-workers (Herr et al, 1997) showed that daunorubicin-induced ceramide generation was required for Fas-ligand upregulation and apoptosis as both events were inhibited in NPD cells. In contrast, daunorubicin-induced JNK stimulation was not attenuated in NPD cells although a requirement for JNK activation in induction of apoptosis was not evaluated in these studies.…”

“…Ceramide signaling of JNK activation is similarly pro-apoptotic Herr et al, 1997;Huang et al, 1997;Shirakabe et al, 1997;Verheij et al, 1996). Verheij et al showed that diverse environmental stresses (UV, ionizing radiation, oxidative stress, heat, cytokine) that signal JNK activation also signal rapid SMase-mediated ceramide generation in primary cultures of bovine endothelial and U937 cells.…”

Caspase-8/FLICE functions as an executioner caspase in anticancer drug-induced apoptosis

“…It has been demonstrated that chemotherapeutic drugs induce the expression of CD95 and CD95L. Therefore, it was proposed that drug-induced apoptosis is mediated in a paracrine or autocrine loop via CD95/CD95L interaction, analogously to T cell receptor-mediated cell death (Friesen et al, 1996;Fulda et al, 1997aFulda et al, , 1998MuÈ ller et al, 1997;Herr et al, 1998;Dhein et al, 1995). However, there are also reports indicating that anticancer drugs induce apoptosis independently of death receptors Wesselborg et al, 1999;Eischen et al, 1997;Gamen et al, 1997;Villunger et al, 1997;Fulda et al, 1997b;Tolomeo et al, 1998).…”

Apoptosis mediated by lentiviral TRAIL transfer involves transduction-dependent and -independent effects

“…31 Experiments were performed at least three times in triplicate and values given are the mean of triplicates7standard deviation. Surface stainings of TRAIL receptors were carried out as described, 24 except that biotinylated anti-mouse-IgG and streptavidin-APC were used according to the manufacturer's recommendations.…”