Liliana Greger

BACKGROUND: DNA methylation constitutes a key epigenetic mechanism by which cells regulate gene transcription. Among its roles are the dynamic regulation of gene expression, for example, as part of an evolving immune response, and cell differentiation in specialized tissues. Here our aim was to study the impact of differences in methylation patterns in the intestine with regard to inflammatory bowel disease (IBD) susceptibility and activity. METHODS: Having extracted DNA from rectal biopsies, we conducted genome-wide methylation profiling using the HumanMethylation27 BeadChip microarray to identify genes showing evidence of differential methylation between cases of ulcerative colitis and Crohn's disease and healthy controls. Selected methylation signals were validated in an independent replication panel by pyrosequencing. Correlation with gene expression was sought by quantitative real-time polymerase chain reaction (RT-PCR). RESULTS: Multiple genes showed significant evidence of differential methylation, several appearing in both ulcerative colitis and Crohn's disease comparisons including THRAP2, FANCC, GBGT1, DOK2, TNFSF4, TNFSF12, and FUT7. Many more than expected by chance overlapped with genes previously implicated as playing a role in IBD susceptibility in genome-wide association scans, including CARD9, ICAM3, and IL8RB (P < 0.001). Correlation between methylation and gene expression was identified for selected transcripts. CONCLUSIONS: Consistent differences in DNA methylation between IBD cases and controls at regulatory sites within these genes suggest that their altered transcription contributes to IBD pathogenesis.

BACKGROUND AND AIMS: Although aberrant methylation of key genes in the progression of colorectal neoplasia has been reported, no model-based analysis of the incremental changes through the intermediate adenoma stage has been described. In addition, the biological drivers for these methylation changes have yet to be defined. Linear mixed-effects modelling was used in this study to understand the onset and patterns of the methylation changes of SFRP2, IGF2 DMR0, H19, LINE-1 and a CpG island methylator phenotype (CIMP) marker panel, and they were correlated with DNA methyltransferase 3B (DNMT3B) levels of expression in a sample set representative of colorectal neoplastic progression. METHODS: Methylation of the above CpG islands was measured using quantitative pyrosequencing assays in 261 tissue samples. This included a prospective collection of 44 colectomy specimens with concurrent normal mucosa, adenoma and invasive cancer tissues. Tissue microarrays from a subset of 64 cases were used for immunohistochemical analysis of DNMT3B expression. RESULTS: It is shown that the onset and pattern of methylation changes during colorectal neoplastic progression are locus dependent. The CIMP marker RUNX3 was the earliest CpG island showing significant change, followed by the CIMP markers NEUROG1 and CACNA1G at the hyperplastic polyp stage. SFRP2 and IGF2 DMR0 showed significant methylation changes at the adenomatous polyp stage, followed by the CIMP markers CDKN2A and hMLH1 at the adenocarcinoma stage. DNMT3B levels of immunohistochemical expression increased significantly (p < 0.001) from normal to hyperplastic and from adenomatous polyps to carcinoma samples. DNMT3B expression correlated positively with SFRP2 methylation (r = 0.42, p < 0.001, 95% CI 0.25 to 0.56), but correlated negatively with IGF2 DMR0 methylation (r = 0.26, p = 0.01, 95% CI -0.45 to -0.05). A subset of the CIMP panel (NEUROG1, CACNA1G and CDKN2A) positively correlated with DNMT3B levels of expression (p < 0.05). CONCLUSION: Hierarchical epigenetic alterations occur at transition points during colorectal neoplastic progression. These cumulative changes are closely correlated with a gain of DNMT3B expression, suggesting a causal relationship.

Oncogenic fusion genes that involve kinases have proven to be effective targets for therapy in a wide range of cancers. Unfortunately, the diagnostic approaches required to identify these events are struggling to keep pace with the diverse array of genetic alterations that occur in cancer. Diagnostic screening in solid tumours is particularly challenging, as many fusion genes occur with a low frequency. To overcome these limitations, we developed a capture enrichment strategy to enable high-throughput transcript sequencing of the human kinome. This approach provides a global overview of kinase fusion events, irrespective of the identity of the fusion partner. To demonstrate the utility of this system, we profiled 100 non-small cell lung cancers and identified numerous genetic alterations impacting fibroblast growth factor receptor 3 (FGFR3) in lung squamous cell carcinoma and a novel ALK fusion partner in lung adenocarcinoma.