Cancer is both a genetic and an epigenetic disease. Inactivation of tumour-suppressor genes by epigenetic changes is frequently observed in human cancers, particularly as a result of the modifications of histones and DNA methylation. It is therefore important to understand how these damaging changes might come about. By studying tumorigenesis in the Drosophila eye, here we identify two Polycomb group epigenetic silencers, Pipsqueak and Lola, that participate in this process. When coupled with overexpression of Delta, deregulation of the expression of Pipsqueak and Lola induces the formation of metastatic tumours. This phenotype depends on the histone-modifying enzymes Rpd3 (a histone deacetylase), Su(var)3-9 and E(z), as well as on the chromodomain protein Polycomb. Expression of the gene Retinoblastoma-family protein (Rbf) is downregulated in these tumours and, indeed, this downregulation is associated with DNA hypermethylation. Together, these results establish a mechanism that links the Notch-Delta pathway, epigenetic silencing pathways and cell-cycle control in the process of tumorigenesis.

Control of growth determines the size and shape of organs. Localized signals known as 'organizers' and members of the Pax family of proto-oncogenes are both elements in this control. Pax proteins have a conserved DNA-binding paired domain, which is presumed to be essential for their oncogenic activity. We present evidence that the organizing signal Notch does not promote growth in eyes of D. melanogaster through either Eyeless (Ey) or Twin of eyeless (Toy), the two Pax6 transcription factors. Instead, it acts through Eyegone (Eyg), which has a truncated paired domain, consisting of only the C-terminal subregion. In humans and mice, the sole PAX6 gene produces the isoform PAX6(5a) by alternative splicing; like Eyegone, this isoform binds DNA though the C terminus of the paired domain. Overexpression of human PAX6(5a) induces strong overgrowth in vivo, whereas the canonical PAX6 variant hardly effects growth. These results show that growth and eye specification are subject to independent control and explain hyperplasia in a new way.

Inactivation of MLH1 due to promoter hypermethylation strongly suggests a sporadic origin , providing exclusion criteria for Lynch syndrome. The aim of this study is to compare the utility of methylation analysis of MLH1 and BRAF V600E mutations for the selection of patients with MLH1 negative colorectal cancer for genetic testing. MLH1 methylation status was evaluated by MethyLight and methylation-specific MLPA (MS-MLPA) in tumor DNA from 73 colorectal cancer patients with loss of MLH1 protein expression. These tumors were analyzed for BRAF V600E mutations , and genetic testing for germline MLH1 mutations was performed in all corresponding patients. Ten patients had germline mutations in MLH1 and none of their tumors showed significant MLH1 methylation or BRAF V600E mutation. MLH1 genetic testing excluded patients by MethyLight in 47 patients (64%) , by MS-MLPA in 49 (67%) , and BRAF V600E mutation in only 25 patients (34%) ( 2 P ‫؍‬ 0.00001). Specificity was 75% for MethyLight , 78% for MS-MLPA and 40% for BRAF V600E mutation. The use of MethyLight or MS-MLPA instead of BRAF mutation resulted in a cost reduction of 41% and 45% , respectively , per every MLH1 mutation detected. Taken together , methylation analysis of MLH1 shows better performance characteristics than BRAF V600E mutation in the selection of patients for genetic testing of MLH1 , especially when using

In many animal systems, the local activation of patterning signals in spatially confined regions (organizers) is crucial for promoting the growth of developing organs. Nevertheless, how organizers are set up and how their activity influences global organ growth remains poorly understood. In the Drosophila eye, local Notch activation establishes a conserved dorsal–ventral organizer that promotes growth. The dorsal selector Iroquois complex defines the position of the organizer at the mid‐first instar, and through its ligand, unpaired, the Janus kinase (JAK)/signal transducers and activator of transcription (STAT) pathway is thought to mediate global growth downstream of the organizer. However, here we show that the unpaired/JAK/STAT pathway is actually a fundamental element in the spatial control of the organizer, upstream from Notch activation. Furthermore, we identify four‐jointed, a target of the Fat and Hippo tumour‐suppressor pathways, as a mediator of the growth controlled by the organizer. These findings redefine the process of organizer formation and function, and they identify four‐jointed as a regulatory node, integrating multiple growth‐control pathways.