Indirubin 3′-Epoxide Induces Caspase-Independent Cell Death in Human Neuroblastoma

Abstract

Indirubin inhibits cyclin-dependent kinases by binding to their ATP-binding site, thereby exerting potent cytotoxicity on some tumor cells. We examined the anti-tumor effect of indirubin 3'-epoxide on human neuroblastoma cell lines (IMR-32, SK-N-SH, and NB-39). The results revealed potent cytotoxicity of indirubin 3'-epoxide against the IMR-32 (IC50: 0.16 µM) and SK-N-SH (IC50: 0.07 µM) cells. Furthermore, it also induced an increase of the sub-G1 population in the IMR-32 cells. Examination by Hoechst 33342 staining revealed apoptosis characterized by cell shrinkage, nuclear condensation and nuclear fragmentation in a concentration-dependent manner. Furthermore, annexin V-propidium iodide (PI) double-staining revealed an increase in the percentage of early apoptotic cells following treatment of the cells with indirubin 3'-epoxide without activation of caspases. In addition, significant decreases in the protein level of survivin and poly(ADP-ribose)polymerase (PARP), and increase in that of apoptosis-inducing factor (AIF) were found in the nuclei of the cells. These results suggest that indirubin 3'-epoxide induced caspase-independent apoptosis through mechanisms involving DNA fragmentation and inhibition of DNA repair.

Effects of indirubin and isatin on cell viability, mutagenicity, genotoxicity and BAX/ERCC1 gene expression

“…In addition, it was shown that indirubin-3 0 -monoxime is an inhibitor of death-associated protein kinases (DAPKs) (Jung et al 2016). Recently, a study using Hoechst 33342 and annexin-V-propidium iodide staining revealed that the indirubin derivative indirubin-3 0 -epoxide induces caspase-independent apoptosis in human neuroblastoma cells, probably due to a DNA fragmentation and impairment of DNA repair (Kurita et al 2016). In addition to these mechanisms, indirubins can induce antiproliferative activities by binding the aryl hydrocarbon receptors (AhR), a ligand-activated transcription factor mainly involved in the regulation of xenobioticmetabolizing enzymes (Adachi et al 2001;Knockaert et al 2004).…”

The Fundamental Role of Oxime and Oxime Ether Moieties in Improving the Physicochemical and Anticancer Properties of Structurally Diverse Scaffolds

“…The authors concluded that the sulfur-halogen interaction forces the oxirane moiety close to Cys-199, thereby accelerating the covalent bond formation between the oxirane and the thiol [76,86,87]. In addition, Kurita et al [98] demonstrated that these indirubin-3 -(O-oxiran-2-ylmethyl)-oxime derivatives possess potent cytotoxicity against human neuroblastoma IMR-32 and SK-N-SH cell lines, with IC 50 values of 0.16 and 0.07 µM, respectively. These molecules induce caspase-independent apoptosis by inhibiting DNA repair and causing DNA fragmentation in IMR-32 cells [76,98].…”

Antitumoral Activity of 1,2-Diaminocyclohexane Derivatives in Breast, Colon and Skin Human Cancer Cells

“…Indirubin, a CDK inhibitor, induces caspase-independent cell death in human neuroblastoma [46], while other indirubin derivatives induce cell death through the intrinsic caspase-9 pathway and/or activation of caspase-8 in breast cancer cells [47]. (±)-trans-7 and 9) and macrocycle meso-10 provoke a G 0 /G 1 cell-cycle arrest in the A375 cell lines after 48 h of treatment.…”