Caveolin-1 (CAV1), an essential structural constituent of caveolae that plays an important role in cellular processes such as transport and signaling, has been implicated in the development of human cancers. However, it is unclear whether CAV1 is acting like an oncogene or tumor suppressor gene. We found that CAV1 expression was reduced or absent in 95% of small cell lung cancers (SCLCs; n ‫؍‬ 21 lines), whereas it was retained in 76% of non-small cell lung cancers (NSCLCs; n ‫؍‬ 25 lines) compared with normal human lung epithelial cultures, where it was abundantly expressed. CAV1 expression was tightly linked to the ability to grow attached to the plastic cell culture surface, whereas CAV1-nonexpressing lung cancers of both SCLC and NSCLC type grew as suspension cultures. In addition, attached lung cancer cultures expressed phosphorylated focal adhesion kinase, whereas suspension cultures did not. Lack of CAV1 expression was tightly associated with CAV1 promoter methylation (P < 0.0001) such that CAV1 methylation was found in 93% of SCLCs (n ‫؍‬ 15) and 9% of NSCLCs (n ‫؍‬ 11), whereas 5-aza-2deoxycy-tidine treatment restored CAV1 expression in SCLCs. Exogenous CAV1 expression in SCLCs significantly inhibited soft-agar colony formation but did not lead to attachment. By contrast, CAV1 knockdown in NSCLCs mediated by small interfering RNA against CAV1 led to inhibition of cellular proliferation and soft-agar and liquid colony formation. Importantly, CAV1 knockdown led to reduced phospho-focal adhesion kinase and RalA, but not RalB, levels in NSCLC cells. These results suggest different roles for CAV1 in SCLC, where CAV1 acts like a tumor suppressor gene, and NSCLC, where it appears required for survival and growth.

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,

Purpose: Aberrant methylation of 5 gene promoter regions is an epigenetic phenomenon that is a major mechanism for silencing of tumor suppressor genes in many cancer types. There is limited information about the molecular changes involved in the pathogenesis of gallbladder carcinoma (GBC), including methylation status.Experimental Design: We investigated the aberrant promoter methylation profile of 24 known or suspected tumor suppressor genes in 50 GBCs and compared those results with the findings in 25 chronic cholecystitis (CC) specimens without cancer. The methylation-specific polymerase chain reaction and combined restriction analysis methods were used to detect methylation, and the results were confirmed by sequencing of cloned polymerase chain reaction products.Results: In GBC, gene methylation frequencies varied from 0% to 80%. Ten genes demonstrated relatively high frequencies of aberrant methylation: SHP1 (80%), 3-OST-2 (72%), CDH13 (44%), P15 INK4B (44%), CDH1 (38%), RUNX3 (32%), APC (30%), RIZ1 (26%), P16 INK4A (24%), and HPP1 (20%). Eight genes (P73, RAR␤2, SOCS-1, DAPK, DcR2, DcR1, HIN1, and CHFR) showed low frequencies (2-14%) of methylation, and no methylation of the remaining six genes (TIMP-3, P57, RASSF1A, CRBP1, SYK, and NORE1) was detected. In CC, methylation was detected for seven genes: SHP1 (88%), P15 INK4B (28%), 3-OST-2 (12%), CDH1 (12%), CDH13 (8%), DcR2 (4%), and P16 INK4A (4%). Significantly higher frequencies of methylation in GBC compared with CC were detected for eight genes (3-OST-2, CDH13, CDH1, RUNX3, APC, RIZ1, P16INK4A , and HPP1). Of those, four genes showed frequent methylation (>30%) in GBCs. The mean methylation index, an expression of the amount of methylated genes by case, was significantly higher in GBC (0.196 ؎ 0.013) compared with CC (0.065 ؎ 0.008; P < 0.001).Conclusions: Our study constitutes the most comprehensive methylation profile report available in GBC and demonstrates that this neoplasm has a distinct pattern of abnormal gene methylation. Whereas gallbladders from healthy individual were not available, our finding of methylation in CC cases without cancer suggests that this phenomenon represents an early event in the pathogenesis of GBC.

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Malignant mesothelioma (MM) is associated with asbestos exposure and the presence of SV40 viral sequences. Recently, we reported that SV40 infection of human mesothelial cells (HM) causes aberrant methylation of the tumor suppressor gene (TSG) RASSF1A. We investigated methylation of 12 genes by methylation-specific PCR in 63 MMs, six MM cell lines, and two foci of SV40-infected HM. Methylation percentages of the tested genes ranged from 3 to 65%. The frequencies of HPP1, RASSF1A, Cyclin D2, and RRAD methylation, and the value of the methylation index, were significantly higher in SV40 sequence-positive MMs than in SV40-negative MMs. Methylation of TMS1 and HIC-1 was associated with shortened survival. SV40-infected HM showed progressive aberrant methylation of seven genes (RASS-F1A, HPP1, DcR1, TMS1, CRBP1, HIC-1, and RRAD) during serial passage. Our results demonstrate a relationship between SV40 and methylation of multiple genes in MM, indicating that the virus plays a role in the pathogenesis of MM.