p53-independent early and late apoptosis is mediated by ceramide after exposure of tumor cells to photon or carbon ion irradiation

Abstract

BackgroundTo determine whether ceramide is responsible for the induction of p53-independent early or late apoptosis in response to high- and low-Linear-Energy-Transfer (LET) irradiation.MethodsFour cell lines displaying different radiosensitivities and p53-protein status were irradiated with photons or 33.4 or 184 keV/μm carbon ions. The kinetics of ceramide production was quantified by fluorescent microscopy or High-Performance-Liquid-Chromatogaphy and the sequence of events leading to apoptosis by flow cytometry.ResultsRegardless of the p53-status, both low and high-LET irradiation induced an early ceramide production in radiosensitive cells and late in the radioresistant. This production strongly correlated with the level of early apoptosis in radiosensitive cells and delayed apoptosis in the radioresistant ones, regardless of radiation quality, tumor type, radiosensitivity, or p53-status. Inhibition of caspase activity or ceramide production showed that, for both types of radiation, ceramide is essential for the initiation of early apoptosis in radiosensitive cells and late apoptosis following mitotic catastrophe in radioresistant cells.ConclusionsCeramide is a determining factor in the onset of early and late apoptosis after low and high-LET irradiation and is the mediator of the p53-independent-apoptotic pathway. We propose that ceramide is the molecular bridge between mitotic catastrophe and the commitment phase of delayed apoptosis in response to irradiation.

Cellular and molecular portrait of eleven human glioblastoma cell lines under photon and carbon ion irradiation

“…Firstly, the cell lines presented a massive G2/M arrest 24 h after photon or carbon ion irradiation. This event was chronologically correlated with the appearance of abnormal nuclei and of micronuclei which is consistent with mitotic catastrophe occurrence [12,14,22]. Moreover, we have shown that ceramide-induced apoptosis 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 Table 2 Kinetics of cell distribution in the cell cycle for the 11 GBM cell lines after a 10 Gy photon or 5 Gy carbon ion irradiation.…”

“…The kinetics of ceramide release, which is a determining factor in the onset of early and late apoptoses after radiation exposure [14], was analyzed after both types of irradiation. The intracellular production of ceramide was delayed and started only 120 h after photon or carbon ion exposure, regardless of the cell line or its p53 status (Table 4).…”

Sphingolipids and mitochondrial apoptosis

“…Countless studies have since validated this initial discovery and indicate that cellular ceramide levels increase early in apoptosis in a variety of cell types and in response to a multitude of apoptotic stimuli including TNFα (Garcia-Ruiz et al 1997; Geilen et al 1997), UV-irradiation (Charruyer et al 2007; Chatterjee and Wu 2001; Deng et al 2002; Siskind et al 2010; Uchida et al 2010; Yao et al 2013), IL3 withdrawal (Siskind et al 2010), ionizing radiation (Alphonse et al 2013; Chmura et al 1997; Deng et al 2008; Haimovitz-Friedman et al 1994; Lu and Wong 2004; Mesicek et al 2010; Moeller et al 2009; Vit and Rosselli 2003), serum withdrawal (Caricchio et al 2002; Fernandez-Ayala et al 2000), etoposide (Chen et al 2006; Lin et al 2005; Perry et al 2000; Sawada et al 2000), staurosporine (Wiesner and Dawson 1996), daunorubicin (Bettaieb et al 1999; Bose et al 1995; Chen et al 2000; Come et al 1999; Jaffrezou et al 1996; Mansat et al 1997), taxol (Charles et al 2001), and cisplatin (Min et al 2007; Noda et al 2001; Siskind et al 2010). Thus, ceramide generation appears to be a common cellular response to apoptosis-inducing agents.…”

Radiation-induced acid ceramidase confers prostate cancer resistance and tumor relapse

“…Although we identified the cell death pathway following IR through de novo ceramide generation and apoptosis augmented by the inhibition of AC, we have not yet ruled out a contribution of mitotic catastrophe mediated by factors such as caspase-2. This mechanism of IR-induced cell damage/death is of great interest to us, as ceramide may be of importance to this process (73).…”