LINE-1 and Alu elements are non-LTR retrotransposons, constituting together over 30% of the human genome and they are frequently hypomethylated in human tumors. A relationship between global hypomethylation and genomic instability has been shown, however, there is little evidence to suggest active role for hypomethylation-mediated reactivation of retroelements in human cancer. In our study, we examined by Pyrosequencing the methylation levels of LINE-1 and Alu sequences in 48 primary nonsmall cell carcinomas and their paired adjacent tissues. We demonstrate a significant reduction of the methylation levels of both elements (p 5 7.7 3 10 214 and 9.6 3 10 27 , respectively). The methylation indices of the 2 elements correlated (p 5 0.006), suggesting a possible common mechanism for their methylation maintenance. Genomic instability was measured utilizing 11 fluorescent microsatellite markers located on lung cancer hot-spot regions such as 3p, 5q 9p, 13q and 17p. Hypomethylation of both transposable elements was associated with increased genomic instability (LINE, p 5 7.1 3 10 25 ; Alu, p 5 0.008). The reduction of the methylation index of LINE-1 and Alu following treatment of 3 lung cell lines with 5-aza-2 0 -deoxycitidine, consistently resulted in increased expression of both elements. Our study demonstrates the strong link between hypomethylation of transposable elements with genomic instability in non-small cell lung cancer and provides early evidence for a potential active role of these elements in lung neoplasia. As demethylating agents are now entering lung cancer trials, it is imperative to gain a greater insight into the potential reactivation of silent retrotransposons in order to advance for the clinical utilization of epigenetics in cancer therapy. ' 2008 Wiley-Liss, Inc.Key words: LINE-1; Alu; hypomethylation; genomic instability; lung cancer LINE-1 elements are autonomous non-LTR retrotransposons comprising almost 21% of the human genome. 1 Although most of these elements are inactive, mostly due to 5 0 truncations, there are a number of 80-100 intact LINE-1 elements that remain capable of retrotransposition. 2,3 The full length human LINE-1 retrotransposon is about 6 kb consisting of a 5 0 UTR, two open reading frames (ORF 1 and ORF2), and a 3 0 UTR with a functional polyadenylation signal and a variable length poly-A tail. 1 The bicistronic mRNA of LINE-1 is generated by an internal promoter at the 5 0 UTR region. ORF1 encodes for p40, a 40 kDa RNA-binding protein with cis preference for LINE-1 RNA, while ORF2 encodes for a 150 kDa protein with 3 conserved domains. 4 LINE-1 retrotransposition is undertaken with the help of both ORF1 and ORF2 proteins through a target-primed reverse transcription mechanism (TPRT). 2 In normal human cells, transcription and retrotransposition of LINE-1 is suppressed by a variety of control mechanisms including methylation, siRNAs and transcription regulators. [4][5][6] As a result, cells manage to protect themselves from a number of adverse effects exerted by LINE-1 ...

No abstract

Background: Recent in vitro studies provide evidence that the cell cycle molecules pRb, p53 and MDM2 form a tightly regulated protein network. In this study, we examined the relationship of this protein network in a series of non-small cell lung carcinomas (NSCLCs), with the kinetic parameters, including proliferative activity or proliferation index (PI) and apoptotic index (AI), and ploidy status of the tumors. Material and Methods: A total of 87 NSCLCs were examined using immunohistochemical and molecular methods in order to estimate the status of the pRb-p53-MDM2 network. The kinetic parameters and the ploidy status of the tumors were assessed by in situ assays. The possible associations between alterations of the network, kinetic parameters and ploidy status of the carcinomas were assessed with a series of statistical methods. Results: Aberrant expression of pRb (Ab) and overexpression of p53 (P) and MDM2 (P) proteins were observed in 39%, 57%, and 68% of the carcinomas, respectively. The comprehensive analysis revealed that concurrent alterations in all three cell cycle regulatory molecules were the most frequent pattern, pRb(Ab)/p53(P)/MDM2(P); this "full abnormal" phenotype represented approximately 27% of the cases. This immunoprofile obtained the highest

TNF is critically involved in the pathogenesis of psoriasis. TL1A is a TNF-like cytokine, which, after binding to death domain receptor DR3, provides costimulatory signals to lymphocytes, amplifies Th1- and Th17-mediated immune responses and induces apoptotic cell death. These functions are inhibited when TL1A associates to decoy receptor DcR3. In the present study, we investigated the expression profiles for TL1A, DR3 and DcR3 in the normal skin and in psoriatic skin lesions. By use of immunohistochemistry, we were able to demonstrate constitutive cutaneous expression of DR3 and DcR3 but not of TL1A in healthy skin. On the other hand, in patients with active psoriasis, we observed abundant immunostaining for TL1A and significant upregulation of its receptors (P < 0.05 in comparison to healthy skin). TL1A, DR3 and DcR3 proteins, as well as mRNA transcripts reflecting in situ production of TL1A and DcR3, were also specifically increased in lesional as compared to non-lesional skin from patients with psoriasis (P < 0.05). These proteins were upregulated in cell populations that are critically involved in the pathogenesis of chronic skin inflammation, such as keratinocytes, macrophages in deep dermis and cells at the perivascular/endothelial area. Finally, we provide evidence for the existence of nuclear localization of TL1A in inflammatory cells from psoriatic lesions. This was also observed in inflamed synovia from patients with rheumatoid arthritis, but not in neoplastic TL1A-expressing cell lines. We conclude that interactions between TL1A and its two receptors may be involved in the pathogenesis of chronic skin inflammation that takes place in psoriasis.