Poster Presentation 27th Lorne Cancer Conference 2015

Quantitative assessment of intra-tumour heterogeneity in HER2 positive breast cancer as a predictor of patient response (#283)

Anne Trinh 1 2 , Inga Rye 3 4 , Aslaug Helland 3 4 5 , Hege Russnes 3 4 , Florian Markowetz 2
  1. Gonville and Caius College , Cambridge
  2. University of Cambridge, CRUK Cambridge Institute, Cambridge
  3. Department of Genetics, Institute for Cancer Research, Oslo
  4. K. G. Jebsen Centre for Breast Cancer Research, University of Oslo, Oslo
  5. Department of Cancer Treatment, Oslo University Hospital, Oslo

The targeted therapy trastuzumab has contributed to an increase in overall survival for HER2+ breast cancers patients, however, a large number of patients develop resistance to the drug and eventually relapse. This may be attributed to the presence of subpopulations within the tumour whose distinct genomic and phenotypic properties may give them a survival advantage in response to different selective pressures. 

To assess the contribution of cell-to-cell variability to patient response, 44 patients were assessed for genomic (HER2 and centromere 17) and phenotypic (HER2 and ER protein) differences using immunofluorescence in situ hybridisation (IFISH) before and after neoadjuvant therapy with FEC and trastuzumab. Biopsies were taken from multiple regions in the primary and surgically removed samples, allowing for the measurement of spatial heterogeneity. These images were quantitatively analysed using GoIFISH, a software developed to segment IFISH images and extract quantitative parameters including morphology, protein intensity, copy number and locational information at single cell level.

Our results reveal that greater cellular diversity is associated with partial-response to therapy.A higher degree of cellular diversity within the primary tumour in terms of HER2 copy number, membrane HER2 expression and cellular morphology was observed in partial-responders. In addition, following neoadjuvant therapy, this cell-to-cell diversity was more apparent in surgically removed tumours in the partial-responders, and in many cases ER positivity was observed.Moreover, global assessment of changes before and after therapy provides insight on the types of cells targeted by therapy. The spatial distributions of HER2 spots within nuclei were observed to be scattered following therapy, suggesting a selective pressure against cells containing HER2 amplification at the same locus. These quantitative studies may aid in determining features which may contribute to resistance in HER2+ breast cancers and thus assist in identifying patients at high-risk of relapse.