Inhibition of Akt Signaling by the Lignan Matairesinol Sensitizes Prostate Cancer Cells to TRAIL-Induced Apoptosis
Total Page：16
File Type：pdf, Size：1020Kb
Oncogene (2010) 29, 898–908 & 2010 Macmillan Publishers Limited All rights reserved 0950-9232/10 $32.00 www.nature.com/onc ORIGINAL ARTICLE Inhibition of Akt signaling by the lignan matairesinol sensitizes prostate cancer cells to TRAIL-induced apoptosis E Peuhu1,2, A Rivero-Mu¨ller1,3,7, H Stykki1,2,7, E Torvaldson1,2, T Holmbom4, P Eklund5, M Unkila6, R Sjo¨holm5 and JE Eriksson1,2 1Turku Centre for Biotechnology, University of Turku and A˚bo Akademi University, Biocity, Turku, Finland; 2Department of Biology, A˚bo Akademi University, Tykisto¨katu, Turku, Finland; 3Institute of BioMedicine, University of Turku, Kiinamyllynkatu, Turku, Finland; 4Laboratory of Fiber and Cellulose Technology, A˚bo Akademi University, Porthansgatan 3, Turku/A˚bo, Finland; 5Laboratory of Organic Chemistry, A˚bo Akademi University, Biskopsgatan 8, Turku/A˚bo, Finland and 6Hormos Medical Ltd, Ita¨inen Pitka¨katu 4b, Turku, Finland Tumor necrosis factor-related apoptosis-inducing ligand et al., 2008). Chemotherapy and androgen withdrawal are (TRAIL) has been shown to be selectively pro-apoptotic in used for slowing down the spread of the disease but cancer cells, with minimal toxicity to normal tissues. currently there are no effective treatments for advanced Although this feature makes TRAIL a promising anti- prostate cancer. Therefore, better understanding of cancer cancer agent, not all cancer cell types are sensitive to cell survival mechanisms and more efficient therapy forms TRAIL-induced apoptosis despite abundant expression of are required for treatment of prostate cancer. In this TRAIL receptors. Thus, combinatorial treatments to regard, death receptor ligands, with capacity to activate sensitize tumor cells to TRAIL-induced apoptosis have apoptosis or programmed cell death specifically in cancer been in the focus of extensive research. Dietary lignans cells, have been suggested as one possible treatment have shown cancer preventive and antitumorigenic activ- approach (reviewed by Fulda and Debatin, 2004). ity, but the mechanisms behind these effects are poorly Activation of the tumor necrosis factor family death known. Here we observed that of the three tested lignan receptors, such as the Fas receptor (CD95/APO-1/ molecules, matairesinol (MAT) was the most effective as DR6) and the tumor necrosis factor-related apoptosis- a death receptor-sensitizing agent. MAT sensitized the inducing ligand (TRAIL) receptors 1 and 2 (DR4 and androgen-dependent LNCaP cells to TRAIL-induced DR5), initiates apoptosis through the extrinsic signal- apoptosis both in the presence and absence of androgens. ing pathway. The cytoplasmic death-inducing signal- Treatment with MAT markedly decreased Akt activity, ing complex (DISC) that is formed to the activated which has been implicated as a key signaling mechanism in death receptors serves as a platform for activation of the TRAIL resistance of LNCaP prostate cancer cells. the initiator cysteine proteases caspase-8 and caspase- The involvement of the pathway in the MAT-mediated 10 (Kischkel et al., 1995; Muzio et al., 1996; Vincenz sensitization was shown in rescue experiments using and Dixit, 1997). The proteolytic activity of the ectopic expression of constitutively active Akt. Owing to downstream effector caspasesleadstoapoptosisof the high activity of phosphatidylinositol 3-kinase/Akt the cell. Various damaging stresses trigger the so-called signaling in cancer, targeting this survival pathway with intrinsic pathway of apoptosis. This signaling pathway MAT could markedly benefit TRAIL-based tumor involves the Bcl-2 family proteins that control mito- therapies, including those aimed at prostate cancer. chondrial integrity, cytochrome c release and activa- Oncogene (2010) 29, 898–908; doi:10.1038/onc.2009.386; tion of caspase-9 (Danial and Korsmeyer, 2004). The published online 23 November 2009 death receptor-mediated extrinsic and the mitochon- drial intrinsic apoptosis pathways are connected Keywords: matairesinol; lignans; apoptosis; TRAIL through Bid, a member of the Bcl-2 family proteins, which is a substrate for caspase-8. When Bid becomes cleaved by activated caspase-8, its truncated form (tBid) translocates to the mitochondria in which it induces the release of cytochrome c and other pro- Introduction apoptotic factors (reviewed in Sprick and Walczak, 2004). The main site of death ligand expression is the Prostate cancer is the most common malignancy and the immune system in which NK and T cells use them for second leading cause of cancer mortality in men (Jemal killing transformed or infected cells (reviewed in Schaefer et al.,2007).TRAILorFas ligand-induced Correspondence: Professor JE Eriksson, Department of Biology, A˚bo apoptosis is thereby an important mechanism in the Akademi University, Tykisto¨katu 6B, Turku, 20520, Finland. immune surveillance against transformed, potentially E-mail: john.eriksson@abo.fi 7These authors contributed equally to this work. carcinogenic cells and, consequently, successful cancer Received 28 April 2009; revised 25 September 2009; accepted 2 October cells usually develop resistance against death receptor 2009; published online 23 November 2009 stimulation. Lignans sensitize prostate cancer cells to TRAIL E Peuhu et al 899 The use of Fas ligand as a potential anti-neoplastic inhibition of Akt activity is a key molecular mechanism agent has got into a halt because of induction of severe by which lignans exert their anticancer effects. The liver damage (Ogasawara et al., 1993). However, the presented concept of cancer therapy could be practicable focus has turned to TRAIL because it has been shown to in developing therapies against androgen-dependent induce apoptosis in a range of different tumor cell lines prostate tumors. with minimal pro-apoptotic effects in normal cells. This has lead to extensive research to use TRAIL in treatment of cancer. Several studies have now shown that TRAIL-based therapies show selective antitumor Results activity in mouse models of colon, glioma, lung and prostate cancer, and multiple myeloma (reviewed in Lignans sensitize LNCaP prostate cancer cells to TRAIL-induced apoptosis Koschny et al., 2007). More importantly, recombinant human TRAIL and human monoclonal agonistic Earlier reports show that androgen-dependent LNCaP TRAIL receptor antibodies are currently analysed in prostate cancer cells are TRAIL resistant (Nesterov et al. et al. phase Ib/II clinical trials for cancer therapy. The early , 2001; Thakkar , 2001), although treatment clinical trials are promising and no toxicity has been with the ENL lignan inhibited their proliferation et al. observed in human patients treated with TRAIL or (McCann , 2008) and induced cell death after et al. agonistic antibodies (reviewed by Mahalingam et al., prolonged exposure (Chen , 2007). As it is well 2008). However, targeting of TRAIL receptors alone documented that plant lignans also have potent appears not to be potent enough to kill all cancer cell antitumorigenic activity with minimal side effects et al. et al. types and combination with other sensitizing agents (Thompson , 1996; Bylund , 2005; Saarinen et al. might be needed to induce efficient tumor cell apoptosis. , 2008), we tested whether this activity could Prostate tumors express frequently TRAIL receptors involve sensitization to death receptor signaling. on the cell surface, but these receptors are often not able A number of closely related lignans (Figure 1a) were to trigger TRAIL-induced apoptosis because of in- tested in a non-toxic concentration for their capacity to creased pro-survival signaling (Bucur et al., 2006). sensitize LNCaP prostate cancer cells to TRAIL Research is now focused on discovering combinatorial receptor-mediated apoptosis in the prescence or absence therapies with agents that reduce TRAIL resistance but of androgen. When comparing the effects of hydro- do not harm normal tissues. Lignans are dietary xymatairesinol, ENL and MAT, the results of nuclear phytoestrogens (reviewed by Adlercreutz, 2007) that fragmentation assay showed that both ENL and have shown cancer preventive and antitumorigenic especially MAT were efficient in sensitizing the cells to activity, and thereby may show potential as TRAIL- TRAIL receptor signaling (Figure 1b). Hydroxymatair- esinol had no effect on TRAIL-induced apoptosis. The sensitizing agents. It has been shown that lignans inhibit proliferation and are cytotoxic to prostate cancer cell sensitizing effect of MAT was more pronounced in androgen-deprived cells but observable also in the lines (Lin et al., 2001, Chen et al., 2007). Moreover, androgen-supplied samples that show stronger resis- lignans can prevent tumor growth and induce apoptosis in vivo in prostate cancer xenografts or chemically tance toward TRAIL treatment. At 40 mM, none of the used compounds induced apoptosis in 20 h when induced mammary tumors (Bylund et al., 2005; Saarinen administered alone. We also consistently observed et al., 2008; Thompson et al., 1996) and can also reduce inhibition of cell proliferation by MAT, which corro- experimental metastasis (Li et al., 1999). Plant-derived borates previous work by McCann et al. (2008) (data lignans, such as matairesinol (MAT), are metabolized by not shown). Furthermore, longer pretreatment (24 h) mammalian gut microflora resulting in enterolactone with 40–100 mM MAT was able to some extent enhance (ENL) or enterodiol (Axelson et al., 1982). As a result of TRAIL-induced apoptosis in leukemic Jurkat T cells their promising antitumorigenic effects, we wanted