The estrogen receptor-alpha S118P variant does not affect breast cancer incidence or response to endocrine therapies

Berry Button, Sarah Croessmann, David Chu, D. Marc Rosen, Daniel J. Zabransky, W. Brian Dalton, Karen Cravero, Kelly Kyker-Snowman, Ian Waters, Swathi Karthikeyan, Eric S. Christenson, Josh Donaldson, Tasha Hunter, Lauren Dennison, Cody Ramin, Betty May, Richard Roden, Dana Petry, Deborah K. Armstrong, Kala VisvanathanBen Ho Park

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Purpose: Estrogen receptor-alpha (ER) is a therapeutic target of ER-positive (ER+) breast cancers. Although ER signaling is complex, many mediators of this pathway have been identified. Specifically, phosphorylation of ER at serine 118 affects responses to estrogen and therapeutic ligands and has been correlated with clinical outcomes in ER+ breast cancer patients. We hypothesized that a newly described germline variant (S118P) at this residue would drive cellular changes consistent with breast cancer development and/or hormone resistance. Methods: Isogenic human breast epithelial cell line models harboring ER S118P were developed via genome editing and characterized to determine the functional effects of this variant. We also examined the frequency of ER S118P in a case–control study (N = 536) of women with and without breast cancer with a familial risk. Results: In heterozygous knock-in models, the S118P variant demonstrated no significant change in proliferation, migration, MAP Kinase pathway signaling, or response to the endocrine therapies tamoxifen and fulvestrant. Further, there was no difference in the prevalence of S118P between women with and without cancer relative to population registry databases. Conclusions: This study suggests that the ER S118P variant does not affect risk for breast cancer or hormone therapy resistance. Germline screening and modification of treatments for patients harboring this variant are likely not warranted.

Original languageEnglish (US)
Pages (from-to)401-412
Number of pages12
JournalBreast Cancer Research and Treatment
Issue number2
StatePublished - Apr 15 2019


  • Breast cancer
  • ESR1
  • Endocrine resistance

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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