5-Phenylselenyl- and 5-methylselenyl-methyl-2′-deoxyuridine induce oxidative stress, DNA damage, and caspase-2-dependent apoptosis in cancer cells

Abstract

In the present study, we investigated the signaling pathways implicated in the induction of apoptosis by two modified nucleosides, 5-phenylselenyl-methyl-2'-deoxyuridine (PhSe-T) and 5-methylselenyl-methyl-2'-deoxyuridine (MeSe-T), using human cancer cell lines. The induction of apoptosis was associated with proteolytic activation of caspase-3 and -9, PARP cleavage, and decreased levels of IAP family members, including c-IAP-1 and c-IAP-2, but had no effect on XIAP and survivin. PhSe-T and MeSe-T also enhanced the activities of caspase-2 and -8, Bid cleavage, and the conformational activation of Bax. Additionally, nucleoside derivative-induced apoptosis was inhibited by the selective inhibitors of caspase-2, -3, -8, and -9 and also by si-RNAs against caspase-2, -3, -8, and -9; however, inhibition of caspase-2 and -3 was more effective at preventing apoptosis than inhibition of caspase-8 and -9. Moreover, the inhibition of caspase-2 activation by the pharmacological inhibitor z-VDVAD-fmk or by the knockdown of protein expression using siRNA suppressed nucleoside derivative-induced caspase-3 activation, but not vice versa. PhSe-T and MeSe-T also induced a Δψ(m) loss via a CsA-insensitive mechanism, ROS production, and DNA damage, including strand breaks. Moreover, ROS scavengers such as NAC, tiron, and quercetin inhibited nucleoside derivative-induced ROS generation and apoptosis by blocking the sequential activation of caspase-2 and -3, indicating the role of ROS in caspase-2-mediated apoptosis. Taken together, these results indicate that caspase-2 acts upstream of caspase-3 and that caspase-2 functions in response to DNA damage in both PhSe-T- and MeSe-T-induced apoptosis. Our results also suggest that ROS are critical regulators of the sequential activation of caspase-2 and -3 in nucleoside derivative-treated cancer cells.

Transfection of poly(I:C) can induce reactive oxygen species-triggered apoptosis and interferon-β-mediated growth arrest in human renal cell carcinoma cells via innate adjuvant receptors and the 2-5A system

“…Poly(I:C) transfection induced cleaved forms of caspase-3, -8, -9, -2, and poly (ADP-ribose) polymerase (PARP), a caspase substrate, in these cell lines (Figure 4a). We included caspase-2 because this caspase has been suggested to be involved in ROS-mediated apoptosis [15]. As shown in Figure 4b, adding of z-VAD-fmk, a pan-caspase inhibitor, apparently inhibited the increase in the percentages of Annexin V + cells in poly(I:C)-transfected RCC cells.…”

“…Intriguingly, some reports suggest that DNA damage induces ROS production [15, 38]. Both DNA damage and ROS production may mutually affect this process, leading to augmentation of apoptosis.…”

“…Importantly, ROS activate caspase-2, and DNA damage also induces cleavage of caspase-2 [39]. Caspase-2 is activated in response to DNA damage and provides an important link between DNA damage and engagement of the apoptotic pathway [15, 38]. Additionally, ROS trigger caspase-2 activation and induce apoptosis in a human leukemic T cell line [40].…”

“…Alternatively, reactive oxygen species (ROS) induce intrinsic apoptosis by triggering DNA damage [14]. Notably, caspase-2 has been suggested to participate in ROS-mediated cellular apoptosis [15], but the precise roles of this “orphan” caspase in cancer cell apoptosis have not been fully explained [16]. …”

A new synthetic 2′-hydroxy-2,4,6-trimethoxy-5′,6′-naphthochalcone induces G2/M cell cycle arrest and apoptosis by disrupting the microtubular network of human colon cancer cells

“…ROS are known to activate caspase-2 [29]. To determine whether HMNC-74 triggered ROS generation, we measured intracellular ROS levels using a fluorescent probe, H2-DCF-DA.…”