Faculty Bibliography

Although only 1.5% of the human genome appears to code for proteins, much effort in cancer research has been devoted to this minimal fraction of our DNA. However, the last few years have witnessed the realization that a large class of non-coding RNAs (ncRNAs), named microRNAs, contribute to cancer development and progression by acting as oncogenes or tumor suppressor genes. Recent studies have also shown that epigenetic silencing of microRNAs with tumor suppressor features by CpG island hypermethylation is a common hallmark of human tumors. Thus, we wondered whether there were other ncRNAs undergoing aberrant DNA methylation-associated silencing in transformed cells. We focused on the transcribed-ultraconserved regions (T-UCRs), a subset of DNA sequences that are absolutely conserved between orthologous regions of the human, rat and mouse genomes and that are located in both intra- and intergenic regions. We used a pharmacological and genomic approach to reveal the possible existence of an aberrant epigenetic silencing pattern of T-UCRs by treating cancer cells with a DNA-demethylating agent followed by hybridization to an expression microarray containing these sequences. We observed that DNA hypomethylation induces release of T-UCR silencing in cancer cells. Among the T-UCRs that were reactivated upon drug treatment, Uc.160+, Uc283+A and Uc.346+ were found to undergo specific CpG island hypermethylation-associated silencing in cancer cells compared with normal tissues. The analysis of a large set of primary human tumors (n=283) demonstrated that hypermethylation of the described T-UCR CpG islands was a common event among the various tumor types. Our finding that, in addition to microRNAs, another class of ncRNAs (T-UCRs) undergoes DNA methylation-associated inactivation in transformed cells supports a model in which epigenetic and genetic alterations in coding and non-coding sequences cooperate in human tumorigenesis.

Viruses are associated with 15-20% of human cancers worldwide. In the last century, many studies were directed towards elucidating the molecular mechanisms and genetic alterations by which viruses cause cancer. The importance of epigenetics in the regulation of gene expression has prompted the investigation of virus and host interactions not only at the genetic level but also at the epigenetic level. In this study, we summarize the published epigenetic information relating to the genomes of viruses directly or indirectly associated with the establishment of tumorigenic processes. We also review aspects such as viral replication and latency associated with epigenetic changes and summarize what is known about epigenetic alterations in host genomes and the implications of these for the tumoral process. The advances made in characterizing epigenetic features in cancer-causing viruses have improved our understanding of their functional mechanisms. Knowledge of the epigenetic changes that occur in the genome of these viruses should provide us with markers for following cancer progression, as well as new tools for cancer therapy.

BACKGROUND:Th1 and Th17 cells have been implicated in Crohn's disease (CD) pathophysiology and may play a role in disease persistence. Aim To determine Th1 and Th17 responses in intestine and peripheral blood of early (<32 weeks since initial symptoms) and late (>2 years) CD patients. METHODS:Cytokine mRNA in intestinal biopsies was determined by RT-PCR. Cytokine concentration in culture was measured by ELISA and cytokine-producing cells were identified by intracellular staining. RESULTS:The inflamed mucosa showed significantly increased IL-17 mRNA levels compared with non-inflamed areas, both in early and late CD patients. However, only patients with late (n = 12), but not early (n = 9), active disease showed increased IL-17 production, as well as a significantly higher percentage of IL-17(+)CD4(+) cells in blood, compared with controls (n = 12) or patients in remission (n = 13). Moreover, cultured peripheral CD4(+) cells from late active CD patients presented significantly higher percentages of IL-17(+), IL-22(+) and IFN-gamma(+) and a significantly increased production of IL-17 and IL-22, but not IFN-gamma(+). CONCLUSIONS:Increased IL-17 gene transcription is common to early and late CD mucosa. However, exacerbated Th17 responses in the peripheral blood appear only in late disease. We propose that this population may constitute a mechanism of perpetuating the disease.