DAPK2 is a novel modulator of TRAIL-induced apoptosis

Abstract

Targeting molecules involved in TRAIL-mediated signalling has been hailed by many as a potential magic bullet to kill cancer cells efficiently, with little side effects on normal cells. Indeed, initial clinical trials showed that antibodies against TRAIL receptors, death receptor (DR)4 and DR5, are well tolerated by cancer patients. Despite efficacy issues in the clinical setting, novel approaches to trigger TRAIL-mediated apoptosis are being developed and its clinical potential is being reappraised. Unfortunately, as observed with other cancer therapies, many patients develop resistance to TRAIL-induced apoptosis and there is thus impetuous for identifying additional resistance mechanisms that may be targetable and usable in combination therapies. Here, we show that the death-associated protein kinase 2 (DAPK2) is a modulator of TRAIL signalling. Genetic ablation of DAPK2 using RNA interference causes phosphorylation of NF-jB and its transcriptional activity in several cancer cell lines. This then leads to the induction of a variety of NF-jB target genes, which include proapoptotic DR4 and DR5. DR4 and DR5 protein expression is correspondingly increased on the cell surface and this leads to the sensitisation of resistant cells to TRAILinduced killing, in a p53-independent manner. As DAPK2 is a kinase, it is imminently druggable, and our data thus offer a novel avenue to overcome TRAIL resistance in the clinic. Despite the effort and resources invested in cancer research, cancer remains a serious public health problem. Most patients are treated surgically, with chemotherapeutic drugs and/or antibodies and small molecule inhibitors. Patients generally respond well to the initial therapy but frequently develop resistance to it. This poses a challenge to their treatment and calls for alternative approaches to be developed. Indeed, much excitement was generated in the mid-1990s when tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) was identified. [1][2][3][4] TRAIL is a death receptor (DR) ligand that signals through DR4 and DR5, two members of the TNF receptor family. 5-7 DR5 has two isoforms that differ by 29 amino acids and which are functionally indistinguishable. 5,8 TRAIL ligation activates primarily the extrinsic apoptotic pathway. The formation of ligand/receptor complexes leads to the assembly of a multiprotein death-inducing signalling complex (DISC), which in the case of TRAIL is typically composed of the adaptor Fasassociated death domain, caspase-8, caspase-10 and/or c-FLIP. These initiator caspases proteolytically cleave effector caspases such as caspase-3, caspase-6 and/or caspase-7 thereby activating them. This leads to the destruction of key cellular components and the appearance of typical features of apoptosis. TRAIL can also activate intrinsic apoptotic pathways via BID and thus involve mitochondria. By virtue of preferentially killing tumour cells, TRAIL is seen by many as a 'magic bullet' against cancer cells. Some cancer cells, however, are resistant, or develop resistanc...

Identification of Novel Death-Associated Protein Kinase 2 Interaction Partners by Proteomic Screening Coupled with Bimolecular Fluorescence Complementation

“…Overexpression of DAPK2 results in morphological changes reminiscent of apoptosis in adherent cells, such as membrane blebbing and condensation of nuclei (5,6), and in reduced viability and survival in suspension cells (12,13). In line with these findings, restoration of DAPK2 activity through fusion of a constitutively active DAPK2 to CD30 in Hodgkin lymphoma cells resulted in selective apoptosis in tumor cells in vitro and in prolonged survival in a Hodgkin lymphoma mouse model (14), and depletion of DAPK2 sensitizes resistant cells to TRAIL-induced killing (15). DAPK2 also induces autophagy and autophagic cell death by directly interacting with mTORC1, one of the negative regulators of autophagy, and by suppressing its activity through phosphorylation (3,11).…”

Silencing the epigenetic silencer KDM4A for TRAIL and DR5 simultaneous induction and antitumor therapy

“…However, no significant KDM5 ChIP signal was detected at the DR5 promoter (Figure 5a; Supplementary Figure S7a). DR5 is transcriptionally regulated by factors including p53, NF-κB and the CEBP family member CHOP/DDIT3/GADD153 21 (Supplementary Figure S7b). As shown in Figures 1 and 2, inhibition of KDM4A induced DR5 expression in the p53-null H1299 cell line, indicating a lack of p53 involvement in the DR5 induction.…”

“…Although NF-kappaB is well documented to mediate TRAIL resistance by up-regulation of a number of antiapoptotic genes, 18,19 in certain context, NF-kappaB can also stimulate expression of TRAIL and other proapoptotic ligands. 20,21 Interferons can stimulate TRAIL expression in cancer cells through STAT1 or IRF-1. Interestingly, these Abbreviations: TRAIL/TNFSF10TNF-related apoptosis-inducing ligand/tumor necrosis factor superfamily member 10; TNFRSF10A/DR4, TNF receptor superfamily member 10a/death receptor 4; TNFRSF10B/DR5, TNF receptor superfamily member 10b/death receptor 5; KDM4A/JMJD2A, lysine demethylase 4 A; KDM4B, lysine demethylase 4B; C-4, compound-4/ NSC636819; FOXO3a, forkhead box O3A; DDIT3/CHOP, DNA damage inducible transcript 3; HDAC, histone deacetylase; NCoR, nuclear receptor co-repressor; AR, androgen receptor; ER, estrogen receptor; IHC, Immunohistochemistry…”

“…Although NF-kappaB is well documented to mediate TRAIL resistance by up-regulation of a number of antiapoptotic genes, 18,19 in certain context, NF-kappaB can also stimulate expression of TRAIL and other proapoptotic ligands. 20,21 Interferons can stimulate TRAIL expression in cancer cells through STAT1 or IRF-1. Interestingly, these factors were also shown to regulate the expression of DR4 and/or DR5.…”

Synergistic effect of TRAIL and irradiation in elimination of glioblastoma stem-like cells

“…The modulation mechanisms of DR5 expression are still obscure at present. Previous reports have suggested that activation of NF-κB pathway could up-regulate DR5 expression [35]; therefore, irradiation possibly increases the expression of DR5 through activation of NF-κB pathway. This is possibly one mechanism of up-regulation of DR5 after irradiation in GSLCs.…”