Objectives: Defects in the apoptotic pathway are a general cause for drug resistance. Chemotherapy in combination with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has proven to be an effective strategy to induce apoptosis in vitro in ovarian tumor cells. Systemic TRAIL administration might be a therapeutic option, since no toxicity was observed in nonhuman primates. In the present study, expression of TRAIL and its apoptosis-inducing death receptors (DR4 and DR5) and inhibitory decoy receptor (DcR1) was studied in normal ovaries and in malignant ovarian tumors before and after chemotherapy to investigate the therapeutic potential of TRAIL.
Methods: DR4, DR5, DcR1, and TRAIL were studied immunohistochemically in 5 normal ovaries, 15 stages I/II, and 26 stages III/IV primary ovarian cancers, including 19 paired tumor samples (pre- and post-chemotherapy).
Results: Surface epithelium of normal ovaries expressed TRAIL and its receptors; ovarian stromal cells expressed only DcR1. Of the ovarian cancers, 73% expressed DR4, 51% DR5, 46% DcR1, and 34% TRAIL. Most primary ovarian cancers (88%) expressed at least one death receptor. TRAIL expression was lower in stage III/IV than in stage I/II tumors (P<0.05). In paired samples, DR5 immunostaining was more frequently (P=0.05) and stronger (P<0.01) expressed in residual tumors.
Conclusion: Early stage tumors expressed TRAIL more frequently than advanced stage tumors. Most primary and residual ovarian tumors expressed at least one TRAIL death receptor, while in residual tumors following chemotherapy, DR5 was more frequently expressed. Therefore, human recombinant TRAIL administration might be an interesting treatment option.