CAPG and GIPC1: Breast Cancer Biomarkers for Bone Metastasis Development and Treatment

Jules A Westbrook, David A Cairns, Jianhe Peng, Valerie Speirs, Andrew M Hanby, Ingunn Holen, Steven L Wood, Penelope D Ottewell, Helen Marshall, Rosamonde E Banks, Peter J Selby, Robert E Coleman, Janet E Brown

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BACKGROUND: Bone is the predominant site of metastasis from breast cancer, and recent trials have demonstrated that adjuvant bisphosphonate therapy can reduce bone metastasis development and improve survival. There is an unmet need for prognostic and predictive biomarkers so that therapy can be appropriately targeted.

METHODS: Potential biomarkers for bone metastasis were identified using proteomic comparison of bone-metastatic, lung-metastatic, and nonmetastatic variants of human breast cancer MDA-MB-231 cells. Clinical validation was performed using immunohistochemical staining of tumor tissue microarrays from patients in a large randomized trial of adjuvant zoledronic acid (zoledronate) (AZURE-ISRCTN79831382). We used Cox proportional hazards regression, the Kaplan-Meier estimate of the survival function, and the log-rank test to investigate associations between protein expression, clinical variables, and time to distant recurrence events. All statistical tests were two-sided.

RESULTS: Two novel biomarker candidates, macrophage-capping protein (CAPG) and PDZ domain-containing protein GIPC1 (GIPC1), were identified for clinical validation. Cox regression analysis of AZURE training and validation sets showed that control patients (no zoledronate) were more likely to develop first distant recurrence in bone (hazard ratio [HR] = 4.5, 95% confidence interval [CI] = 2.1 to 9.8, P < .001) and die (HR for overall survival = 1.8, 95% CI = 1.01 to 3.24, P = .045) if both proteins were highly expressed in the primary tumor. In patients with high expression of both proteins, zoledronate had a substantial effect, leading to 10-fold hazard ratio reduction (compared with control) for first distant recurrence in bone (P = .008).

CONCLUSIONS: The composite biomarker, CAPG and GIPC1 in primary breast tumors, predicted disease outcomes and benefit from zoledronate and may facilitate patient selection for adjuvant bisphosphonate treatment.

Original languageEnglish
JournalJournal of the National Cancer Institute
Issue number4
Early online date12 Jan 2016
Publication statusPublished - Apr 2016
Externally publishedYes

Bibliographical note

This work was supported by Cancer Research UK (grant number: C18605/A 10048) through a Clinician Scientist Fellowship (to JEB). DAC was supported by a UK Medical Research Council Career Development Fellowship (G0802416).
The authors are solely responsible for the design of the study; the collection, analysis and interpretation of the data; the writing of the manuscript; and the decision to submit the manuscript for publication. All authors read and approved the final article.

The authors are especially grateful to Professor Joan Massagué for kindly providing the bone- and lung-homing variants of MDA-MB-231 cells used in this study. We also particularly thank the AZURE trial patients and investigators, Mr. Mike Shires and the staff of the Sheffield and Leeds Experimental Cancer Medicine Centres for infrastructure support


  • Adaptor Proteins, Signal Transducing
  • Biomarkers, Tumor
  • Bone Density Conservation Agents
  • Bone Neoplasms
  • Breast Neoplasms
  • Cell Line, Tumor
  • Diphosphonates
  • Disease Progression
  • Female
  • Humans
  • Imidazoles
  • Immunohistochemistry
  • Kaplan-Meier Estimate
  • Lung Neoplasms
  • Microfilament Proteins
  • Molecular Targeted Therapy
  • Nuclear Proteins
  • Odds Ratio
  • Predictive Value of Tests
  • Proportional Hazards Models
  • Randomized Controlled Trials as Topic
  • Reproducibility of Results
  • Editorial
  • Research Support, Non-U.S. Gov't


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