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LGR5 in breast cancer and ductal carcinoma in situ: a diagnostic and prognostic biomarker and a therapeutic target.

  • Author(s): Hagerling, Catharina;
  • Owyong, Mark;
  • Sitarama, Vaishnavi;
  • Wang, Chih-Yang;
  • Lin, Charlene;
  • van den Bijgaart, Renske JE;
  • Koopman, Charlotte D;
  • Brenot, Audrey;
  • Nanjaraj, Ankitha;
  • Wärnberg, Fredrik;
  • Jirström, Karin;
  • Klein, Ophir D;
  • Werb, Zena;
  • Plaks, Vicki
  • et al.
Abstract

Background

Novel biomarkers are required to discern between breast tumors that should be targeted for treatment from those that would never become clinically apparent and/or life threatening for patients. Moreover, therapeutics that specifically target breast cancer (BC) cells with tumor-initiating capacity to prevent recurrence are an unmet need. We investigated the clinical importance of LGR5 in BC and ductal carcinoma in situ (DCIS) to explore LGR5 as a biomarker and a therapeutic target.

Methods

We stained BC (n = 401) and DCIS (n = 119) tissue microarrays with an antibody against LGR5. We examined an LGR5 knockdown ER- cell line that was orthotopically transplanted and used for in vitro colony assays. We also determined the tumor-initiating role of Lgr5 in lineage-tracing experiments. Lastly, we transplanted ER- patient-derived xenografts into mice that were subsequently treated with a LGR5 antibody drug conjugate (anti-LGR5-ADC).

Results

LGR5 expression correlated with small tumor size, lower grade, lymph node negativity, and ER-positivity. ER+ patients with LGR5high tumors rarely had recurrence, while high-grade ER- patients with LGR5high expression recurred and died due to BC more often. Intriguingly, all the DCIS patients who later died of BC had LGR5-positive tumors. Colony assays and xenograft experiments substantiated a role for LGR5 in ER- tumor initiation and subsequent growth, which was further validated by lineage-tracing experiments in ER- /triple-negative BC mouse models. Importantly, by utilizing LGR5high patient-derived xenografts, we showed that anti-LGR5-ADC should be considered as a therapeutic for high-grade ER- BC.

Conclusion

LGR5 has distinct roles in ER- vs. ER+ BC with potential clinical applicability as a biomarker to identify patients in need of therapy and could serve as a therapeutic target for high-grade ER- BC.

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