The genomic complexity of profound copy number aberrations has prevented effective molecular stratification of ovarian cancers. Here, to decode this complexity, we derived copy number signatures from shallow whole-genome sequencing of 117 high-grade serous ovarian cancer (HGSOC) cases, which were validated on 527 independent cases. We show that HGSOC comprises a continuum of genomes shaped by multiple mutational processes that result in known patterns of genomic aberration. Copy number signature exposures at diagnosis predict both overall survival and the probability of platinum-resistant relapse. Measurement of signature exposures provides a rational framework to choose combination treatments that target multiple mutational processes.

DeRossi, C. et al. Ablation of mouse phosphomannose isomerase (Mpi) causes mannose 6-phosphate accumulation, toxicity, and embryonic lethality.

Mounting evidence suggests that aberrant methylation of CpG islands is a major pathway leading to the inactivation of tumor suppressor genes and the development of cancer. Recent studies on colorectal and gastric cancer have defined a CpG island methylator phenotype (CIMP), which involves the targeting of multiple genes by promoter hypermethylation. To determine the role of methylation in ovarian cancer, we have investigated the methylation status of 93 primary ovarian tumors at ten loci using methylationspecific polymerase chain reaction (MSP). Seven of the loci (BRCA1, HIC1, MINT25, MINT31, MLH1, p73 and hTR) were found to be methylated in a significant proportion of the ovarian tumors, and methylation of at least one of these was found in the majority (71%) of samples. Although concurrent methylation of multiple genes was commonly seen, this did not seem to be due to a single CIMP phenotype. Instead the results suggest the presence of at least three groups of tumors, two CIMP-positive groups, each susceptible to methylation of a different subset of genes, and a further group of tumors not susceptible to CpG island methylation, at least at the loci studied. In human genomic DNA the CpG dinucleotide is generally underrepresented and the majority exhibit methylation at the 5Ј position of the cytosine.

The secretome of cancer and stromal cells generates a microenvironment that contributes to tumour cell invasion and angiogenesis. Here we compare the secretome of human mammary normal and cancer-associated fibroblasts (CAFs). We discover that the chloride intracellular channel protein 3 (CLIC3) is an abundant component of the CAF secretome. Secreted CLIC3 promotes invasive behaviour of endothelial cells to drive angiogenesis and increases invasiveness of cancer cells both in vivo and in 3D cell culture models, and this requires active transglutaminase-2 (TGM2). CLIC3 acts as a glutathione-dependent oxidoreductase that reduces TGM2 and regulates TGM2 binding to its cofactors. Finally, CLIC3 is also secreted by cancer cells, is abundant in the stromal and tumour compartments of aggressive ovarian cancers and its levels correlate with poor clinical outcome. This work reveals a previously undescribed invasive mechanism whereby the secretion of a glutathione-dependent oxidoreductase drives angiogenesis and cancer progression by promoting TGM2-dependent invasion.

Clear cell carcinoma of the ovary (CCC) is a histologic subtype of epithelial ovarian cancer with a distinct clinical behavior. There are marked geographic differences in the prevalence of CCC. The CCC is more likely to be detected at an early stage than high-grade serous cancers, and when confined within the ovary, the prognosis is good. However, advanced disease is associated with a very poor prognosis and resistance to standard treatment. Cytoreductive surgery should be performed for patients with stage II, III, or IV disease. An international phase III study to compare irinotecan/cisplatin and paclitaxel/carboplatin as adjuvant chemotherapy for stage IIV CCC has completed enrollment (GCIG/JGOG3017). Considering the frequent PIK3CA mutation in CCC, dual inhibitors targeting PI3K, AKT in the mTOR pathway, are promising. Performing these trials and generating the evidence will require considerable international collaboration.