Abstract 3433: Characterization of co-occurring clonal hematopoiesis to identify high risk clones associated with hematologic cancer risk
Authors: Barnao Kara M. , Hubbard Aubrey K. , Zhou Weiyin , Chan Irenaeus , Tran Duc , Cao Yin , Chanock Stephen J. , Bolton Kelly L. , Machiela Mitchell J. 
Published: March 2024

Abstract
Clonal hematopoiesis (CH) is the age-related clonal expansion of hematopoietic cells as a result of acquired mutations in driver genes, commonly referred to as clonal hematopoiesis of indeterminate potential (CHIP), or due to large-scale mosaic chromosomal alterations (mCAs). While the type and genomic location of CH exhibits varying associations with hematological parameters as well as lymphoid and myeloid malignancy risk, few studies have examined the co-occurrence of CH types. We characterized the frequency of co-occurring CH and examined the association of co-occurring CH with various cancer-related phenotypes to identify potential high-risk clones associated with hematologic cancer risk.
We analyzed sequencing and genotyping array data from 453,807 participants in the UK Biobank to detect CHIP and mCAs. In total, 83,240 (18.3%) individuals had at least one detectable type of CH, with increasing age strongly associated with increasing frequency of CH (P &lt; 2 × 10−16). The most common type of CH was mCAs (N= 67,081 (14.7%)), with mosaic loss of the Y (mLOY) and X (mLOX) chromosomes being most frequently observed in males and females, respectively. We noted inverse associations between mLOY or mLOX with autosomal mCAs, but positive associations between some autosomal mCAs (e.g., chr3 and chr18 mCAs). CHIP was detected in 20,354 (4.5%) individuals, with mutations in DNMT3A, TET2, and ASXL1 most common. Similar to mCAs, some forms of CHIP were inversely associated (e.g., DNMT3A CHIP with most other CHIP mutations) while others displayed positive associations (e.g., JAK2 CHIP with NFE2 CHIP), suggesting both instances of mutual exclusivity as well as cooperation. We likewise noted several instances of CHIP and mCAs co-occurring (e.g., MYD88 and chr18 mCAs) and overlapping (e.g., JAK2 and 9p24 mCAs) more frequently than expected.
Compared to those with no CH, participants with CH had notable alterations in blood cell counts, leukocyte telomere length (LTL), and elevated hematologic cancer risk even after adjusting for age, sex, smoking, and genetic ancestry. Furthermore, co-occurring CH had more pronounced associations, with the greatest alterations and hematologic cancer risk generally noted in participants with overlapping CHIP and mCAs (e.g., MYD88 and 3p22 mCAs). These findings highlight substantial enrichment in CH co-occurrences, particularly in the positional overlap of CHIP and mCAs, and indicate an increased risk of hematological malignancies when CH types overlap (HR = 29.5, 95% CI [24.0, 36.3], P &lt; 2 × 10−16). Overall, this study details the landscape of co-occurring CH and nominates high risk co-occurrences with strong implications for future hematological malignancy risk.
Citation Format: Kara M. Barnao, Aubrey K. Hubbard, Weiyin Zhou, Irenaeus Chan, Duc Tran, Yin Cao, Stephen J. Chanock, Kelly L. Bolton, Mitchell J. Machiela. Characterization of co-occurring clonal hematopoiesis to identify high risk clones associated with hematologic cancer risk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3433.