Aberrant methylation of trail decoy receptor genes is frequent in multiple tumor types

Abstract

TNF-related apoptosis-inducing ligand (TRAIL) selectively induces programmed cell death (apoptosis) in various cancer cells but not in normal cells. TRAIL is known to bind to 4 different receptors, 2 proapoptotic (DR4 andDR5Several members of the tumor necrosis factor receptor superfamily, which includes tumor necrosis factor receptor 1, Fas (Apo-1/CD95), and the decoy receptors for TRAIL (Apo-2L), regulate programmed cell death (apoptosis). Upon engagement by their respective ligands, tumor necrosis factor receptor 1 and Fas recruit adaptor molecules and activate a cascade of cysteine proteases (caspases), the proteolytic activity of which results in apoptosis. The TRAIL-activated DR4 (also TNFRSF10A, Apo-2, TRAIL-R1) 1,2 and DR5 (also TNFRSF10B, KILLER/DR5, TRICK2, TRAIL-R3) receptors 2-4 have also been shown to initiate a caspase-mediated apoptotic pathway. 4 Death inducing DR4 and DR5 and the decoy receptors DcR1 (also TNFRSF10C, TRID, TRAIL-R3) and DcR2 (also TNFRSF10D, TRUNDD, TRAIL-R4) are structurally related, especially in their extracellular domains and are all located at 8p 21-22. 5,6 Decoy receptor DcR1 completely lacks the intra-cellular death domain and DcR2 contains a truncated, nonfunctional death domain and appear unable to induce apoptosis. The extracellular domains of DcR1 or DcR2 compete with those of DR4 or DR5 for TRAIL binding. Thus, based on the current knowledge, DcR1 or DcR2 are believed to inhibit apoptosis induction mediated through DR4 and DR5. 5 Inactivation of genes may occur via point mutations, allelic loss (LOH), homozygous deletions or by aberrant methylation. 7-9 Aberrant methylation of 5Ј gene promoter regions associated with gene silencing is an epigenetic phenomenon involving many genes observed in almost all cancer types, including breast cancers, lung cancers and mesotheliomas. 9 -18 We have demonstrated loss of expression (at RNA and protein level) of DR4 and DR5 in lung cancer cell lines, although the mechanism was not via methylation. 19 Recently, 20 it was reported that DcR1 and DcR2 expression are frequently silenced by aberrant methylation of 5Ј regions of these genes in pediatric tumor cell lines and neuroblastomas. In our study, we examined the methylation and expression status of DcR1, DcR2, DR4 and DR5 in breast and lung cancers and malignant mesothelioma (MM). We also examined the methylation status of TRAIL receptor genes in many other types of malignancies. We tried to correlate methylation status with clinical features of patients including survival and histological type in lung breast MM and prostate cancer. MATERIAL AND METHODS Cell linesCell lines were initiated by AFG (breast, lung, some MMs) or HIP (most MMs). [21][22][23] Twenty-seven lung cancer cell lines and 23 breast cancer cell lines and were grown in RPMI-1640 medium (Life Technologies Inc., Rockville, MD) supplemented with 5% FBS and incubated in 5% CO 2 at 37°C. Four non-malignant mesothelial primary cell cultures (HCC3466, HCC3468, HCC3469,

Transformation-Dependent Silencing of Tumor-Selective Apoptosis-Inducing TRAIL by DNA Hypermethylation Is Antagonized by Decitabine

“…TRAIL is not the only gene of the TRAIL regulon that is epigenetically silenced. DNA methylation of both apoptogenic and decoy receptors of TRAIL and CASP8 has been reported for glioblastoma and small cell lung carcinomas (36)(37)(38). Moreover, gene-selective epigenetic silencing upon transformation by oncogenic Ras has been previously observed (39)(40)(41); and among these genes is PAR-4, which is required for TRAIL-induced apoptosis (42).…”

An apoptotic molecular network identified by microarray: On the TRAIL to new insights in epithelial ovarian cancer

“…In EOC, no mutations in Trail receptors were observed. 28 However, epigenetic silencing of TRAIL receptors was reported in different cancer types, including malignancies of the breast, lung, bladder, and cervix as well as lymphoma, leukemia, myeloma, neuroblastoma, and EOC [29][30][31][32] (for review, see Debatin and Krammer 9 ). Casp8, which is an effector of apoptosis, was inactivated by hypermethylation in a number of different tumors derived from neuroblastoma, brain tumors, Ewing sarcoma, and small lung cell carcinoma (for review, see Debatin and Krammer 9 ).…”

Modulation of death receptors by cancer therapeutic agents

“…In contrast to DcR3, DcR1 and DcR2 are generally downregulated in many types of cancer, largely due to gene methylation. 38,39 It is possible that DcR overexpressing tumors may gain a selective growth advantage by escaping from death ligand/death receptor-induced apoptosis. Given the frequent downregulation or loss of DcR1 and DcR2 expression in multiple cancers, which still express DR4 and/or DR5 or exhibit increased DR4 and DR5 expression, there may be an opportunity to treat these cancers with TRAIL or agonistic DR4 or DR5 antibodies via targeted induction of TRAIL/death receptor-mediated apoptosis of cancer cells.…”