Choon Kiat Ong

Using large-scale exome sequencing, Andrew Futreal and colleagues have identified a second frequently mutated gene (after VHL) in clear cell renal cell carcinomas, the most frequent type of kidney cancer. PBRM1, a member of the SWI/SNF complex involved in transcriptional regulation, is mutated in about 40% of cases and is shown to function as a tumour suppressor gene. PBRM1 was independently found as a putative cancer gene involved in pancreatic cancer in a mouse transposon screen. These results — together with the fact that other components of the same complex are known cancer genes — unambiguously identify PBRM1 as a major cancer gene. Using large-scale exome sequencing, this study identifies a second (after VHL) frequently mutated gene in clear cell renal cell carcinomas, the most frequent type of kidney cancer. PBRM1, a member of the SWI/SNF complex involved in transcriptional regulation, is mutated in about 40% of cases and shown to function as tumour suppressor gene. PBRM1 was independently found as a putative cancer gene involved in pancreatic cancer in a mouse transposon screen. The genetics of renal cancer is dominated by inactivation of the VHL tumour suppressor gene in clear cell carcinoma (ccRCC), the commonest histological subtype. A recent large-scale screen of ∼3,500 genes by PCR-based exon re-sequencing identified several new cancer genes in ccRCC including UTX (also known as KDM6A)1, JARID1C (also known as KDM5C) and SETD2 (ref. 2). These genes encode enzymes that demethylate (UTX, JARID1C) or methylate (SETD2) key lysine residues of histone H3. Modification of the methylation state of these lysine residues of histone H3 regulates chromatin structure and is implicated in transcriptional control3. However, together these mutations are present in fewer than 15% of ccRCC, suggesting the existence of additional, currently unidentified cancer genes. Here, we have sequenced the protein coding exome in a series of primary ccRCC and report the identification of the SWI/SNF chromatin remodelling complex gene PBRM1 (ref. 4) as a second major ccRCC cancer gene, with truncating mutations in 41% (92/227) of cases. These data further elucidate the somatic genetic architecture of ccRCC and emphasize the marked contribution of aberrant chromatin biology.

Abstract Cholangiocarcinoma (CCA) is a hepatobiliary malignancy exhibiting high incidence in countries with endemic liver-fluke infection. We analyzed 489 CCAs from 10 countries, combining whole-genome (71 cases), targeted/exome, copy-number, gene expression, and DNA methylation information. Integrative clustering defined 4 CCA clusters—fluke-positive CCAs (clusters 1/2) are enriched in ERBB2 amplifications and TP53 mutations; conversely, fluke-negative CCAs (clusters 3/4) exhibit high copy-number alterations and PD-1/PD-L2 expression, or epigenetic mutations (IDH1/2, BAP1) and FGFR/PRKA-related gene rearrangements. Whole-genome analysis highlighted FGFR2 3′ untranslated region deletion as a mechanism of FGFR2 upregulation. Integration of noncoding promoter mutations with protein–DNA binding profiles demonstrates pervasive modulation of H3K27me3-associated sites in CCA. Clusters 1 and 4 exhibit distinct DNA hypermethylation patterns targeting either CpG islands or shores—mutation signature and subclonality analysis suggests that these reflect different mutational pathways. Our results exemplify how genetics, epigenetics, and environmental carcinogens can interplay across different geographies to generate distinct molecular subtypes of cancer. Significance: Integrated whole-genome and epigenomic analysis of CCA on an international scale identifies new CCA driver genes, noncoding promoter mutations, and structural variants. CCA molecular landscapes differ radically by etiology, underscoring how distinct cancer subtypes in the same organ may arise through different extrinsic and intrinsic carcinogenic processes. Cancer Discov; 7(10); 1116–35. ©2017 AACR. This article is highlighted in the In This Issue feature, p. 1047