Abstract 4602: Recurrent pathway mutations of multiple components of cohesin complex in myeloid neoplasms.

Abstract

Abstract Recent genetic studies have revealed a number of novel gene mutations in myeloid malignancies, unmasking an unexpected role of deregulated histone modification and DNA methylation in myeloid neoplasms. However, our knowledge about the spectrum of gene mutations in myeloid neoplasms is still incomplete. So, we analyzed 50 paired tumor-normal samples of myeloid neoplasms using whole exome sequencing, among which we identified recurrent mutations involving STAG2, a core cohesin component, and two other cohesin components, including STAG1 and PDS5B. Cohesin is a multimeric protein complex which is composed of four core subunits (SMC1, SMC3, RAD21 and STAG proteins), and is engaged in cohesion of sister chromatids, DNA repair and transcriptional regulation. To extend the findings in the whole-exome analysis, an additional 534 primary samples of various myeloid neoplasms was examined for mutations and deletions in a total of 9 components of the cohesin complexes, using high-throughput sequencing and SNP arrays. In total, mutations/deletions were found in a variety of myeloid neoplasms, including AML (22/131), CMML (15/86), MDS (26/205), in a mutually exclusive manner. Cohesin mutations frequently coexisted with other common mutations in myeloid neoplasms, significantly associated with spliceosome mutations. Deep sequencing of these mutant alleles revealed that majority of the cohesin mutations existed in the major tumor populations, indicating their early origin during leukemogenesis. Next, we examined several myeloid leukemia cell lines with or without cohesin mutations for expression of each cohesin component and their chromatin-bound fractions. Interestingly, the chromatin-bound fraction of several components of cohesin was significantly reduced in cell lines having mutated or defective cohesin components, suggesting substantial loss of cohesin-bound sites on chromatin. Finally, we introduced the wild-type RAD21 allele into RAD21-mutated cell lines (Kasumi-1), which effectively suppressed the proliferation of Kasumi-1, supporting a leukemogenic role of compromised cohesin functions. Less frequent mutations of cohesin components have been described in other cancers, where impaired cohesion and consequent aneuploidy were implicated in oncogenic action. However, about half of cohesin-mutated cases in our cohort had completely normal karyotypes, suggesting that cohesin-mutated cells were not clonally selected because of aneuploidy. Of note, the number of mutations determined by our whole exome analysis was significantly higher in cohesin-mutated cases compared to non-mutated cases. Since cohesin participates in post-replicative DNA repair, this may suggest that compromised cohesin function could induce DNA hypermutability and contribute to leukemogenesis. In conclusion, our findings highlight a possible role of compromised cohesin functions in myeloid leukemogenesis. Citation Format: Ayana Kon, Lee-Yung Shih, Masashi Minamino, Masashi Sanada, Yuichi Shiraishi, Yasunobu Nagata, Kenichi Yoshida, Yusuke Okuno, Masashige Bando, Shunpei Ishikawa, Aiko Sato-Otsubo, Genta Nagae, Aiko Nishimoto, Claudia Haferlach, Daniel Nowak, Yusuke Sato, Tamara Alpermann, Teppei Shimamura, Hiroko Tanaka, Kenichi Chiba, Ryo Yamamoto, Tomoyuki Yamaguchi, Makoto Otsu, Naoshi Obara, Mamiko Sakata-Yanagimoto, Tsuyoshi Nakamaki, Ken Ishiyama, Florian Nolte, Wolf-Karsten Hofmann, Shuichi Miyawaki, Shigeru Chiba, Hiraku Mori, Hiromitsu Nakauchi, H. Phillip Koeffler, Hiroyuki Aburatani, Torsten Haferlach, Katsuhiko Shirahige, Satoru Miyano, Seishi Ogawa. Recurrent pathway mutations of multiple components of cohesin complex in myeloid neoplasms. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4602. doi:10.1158/1538-7445.AM2013-4602