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Germline APOBEC3B deletion increases somatic hypermutation in Asian breast cancer that is associated with Her2 subtype, PIK3CA mutations and immune activation
Author(s) -
Pan JiaWern,
Zabidi Muhammad Mamduh Ahmad,
Chong BoonKeat,
Meng MeiYee,
Ng PeiSze,
Hasan Siti Norhidayu,
Sandey Bethan,
Bahnu Saira,
Rajadurai Pathmanathan,
Yip ChengHar,
Rueda Oscar M.,
Caldas Carlos,
Chin SuetFeung,
Teo SooHwang
Publication year - 2021
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.33463
Subject(s) - apobec , somatic hypermutation , biology , germline , germline mutation , breast cancer , genetics , cancer research , somatic cell , allele , mutation , cancer , gene , b cell , antibody , genome
Abstract A 30‐kb deletion that eliminates the coding region of APOBEC3B ( A3B ) is >5 times more common in women of Asian descent compared to European descent. This polymorphism creates a chimera with the APOBEC3A ( A3A ) coding region and A3B 3′UTR, and it is associated with an increased risk for breast cancer in Asian women. Here, we explored the relationship between the A3B deletion polymorphism with tumour characteristics in Asian women. Using whole exome and whole transcriptome sequencing data of 527 breast tumours, we report that germline A3B deletion polymorphism leads to expression of the A3A‐B hybrid isoform and increased APOBEC‐associated somatic hypermutation. Hypermutated tumours, regardless of A3B germline status, were associated with the Her2 molecular subtype and PIK3CA mutations. Compared to nonhypermutated tumours, hypermutated tumours also had higher neoantigen burden, tumour heterogeneity and immune activation. Taken together, our results suggest that the germline A3B deletion polymorphism, via the A3A‐B hybrid isoform, contributes to APOBEC mutagenesis in a significant proportion of Asian breast cancers. In addition, APOBEC somatic hypermutation, regardless of A3B background, may be an important clinical biomarker for Asian breast cancers.