Recombinant human TNF Related Apoptosis Inducing Ligand (rhTRAIL) is an interesting tumor specific agent, inducing apoptosis in a wide variety of tumor cells via binding to its two death receptors DR4 and DR5. Combination of rhTRAIL with chemotherapeutic drugs including cisplatin has been shown to strongly potentate apoptosis induction in cancer cells. Still, there is ample room for improvement of antitumor effect of drug treatment for solid tumors. At least 50% of ovarian cancers carry wild type (wt) p53. The activity of wt p53 activity is tightly regulated by MDM2 in a negative feedbackloop. Inhibition of MDM2 by the small molecule Nutlin-3a then results in wt p53 activation. Since the expression of particularly DR5 can be induced by wt p53, we tested whether Nutlin-3a might be of interest to sensitize wt p53 expressing A2780 ovarian cancer cells to rhTRAIL. Nutlin-3a treatment induced a 1.7 fold upregulation of DR5 membrane expression, while the expression of the anti-apoptotic TRAIL receptor decoy receptor 2 was unaffected. Following cisplatin treatment, DR5 and DcR2 membrane expression were elevated. Both Nutlin-3a and cisplatin induced p53, p21 and MDM2 expression in A2780, but no apoptosis was observed with either drug. RhTRAIL only induced 5% apoptosis, but rhTRAIL in combination with Nutlin-3a or cisplatin induced apoptosis up to 15% and 30%, respectively. To further take advantage of DR5 upregulation, we treated cells with a DR5 selective TRAIL variant (D269H/E195R) as designed by van der Sloot et al. (PNAS 2006). Combination of Nutlin-3a with rhTRAIL resulted in a 3.3-fold increase in apoptosis levels to 20% (±1%) and with the DR5 selective variant in a 2.7-fold increase to 57% (±5%). Apoptosis induction was confirmed as cleavage of both caspase-8 and PARP were observed. Whether Nutlin-3a in combination with cisplatin can potentate rhTRAIL-induced apoptosis is under investigation. In conclusion, Nutlin-3a sensitized ovarian cancer cells carrying wt p53 to rhTRAIL-induced apoptosis, which effect can maximized by specific targeting of DR5. This research was performed within project T3.112 of the Dutch Top Institute Pharma.
|Number of pages||1|
|Issue number||Supplement 9|
|Publication status||Published - 1-May-2009|