Oral Presentation COSA 2015 ASM

Epithelial-Mesenchymal Plasticity Status in Circulating Tumour Cells of Breast Cancer Xenograft Models (#28)

Erik W Thompson 1 2 3 , Anh Viet-Phuong Le 1 4 , Anthony Tachtsidis 1 2 , Tony Blick 1 , Devika Gunasinghe 1 , Mark Waltham 2 , Alexander Dobrovic 4 5 6
  1. Department of Surgery, University of Melbourne, Melbourne, VIC, Australia
  2. St. Vincent’s Institute, Melbourne, Australia
  3. Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology, Brisbane, QLD, Australia
  4. Olivia Newton-John Cancer Research Institute, Melbourne, VIC, Australia
  5. Department of Pathology, University of Melbourne, Melbourne, VIC, Australia
  6. School of Cancer Medicine, La Trobe University Bundoora, Melbourne, VIC, Australia

Metastasis is the major cause of cancer mortality. A strong link between invasive metastatic tumours and epithelial-mesenchymal plasticity (EMP) has been demonstrated in human breast cancer (BC). EMP can provide carcinoma cells with the invasive ability to leave the primary tumour, enter into the circulation as circulating tumour cells (CTCs), arrive at a distant organ and ultimately form a metastasis. To investigate EMP in BC CTCs, the expression profiles of forty-three genes including EMP markers, BC stem cell markers, hormonal receptors, hypoxia and cellular metabolism genes, were characterised in pooled CTCs and in primary tumours of two human BC xenograft-bearing mouse models, MDA-MB-468 and ED03, in two replicate experiments of at least 10 mice. Gene expression of CTCs was also performed at a single cell level. A human-specific tandem nested RT-qPCR method, which can detect as little as a single cell, was developed and used. In pooled CTCs relative to primary tumours, a significant increase in expression of mesechymal markers (SNAIL1 and VIM), and surprisingly of a prototypic epithelial marker CDH1 were observed. A decrease/loss of EpCAM was reproducibly observed in CTCs of both models, while decreased CD24 and EGFR in CTCs were only seen in the MDA-MB-468 model. Genes associating with hypoxia (HIF1A, BNIP3 and APLN) and cellular metabolism (PPARGC1A) were also significantly elevated in CTCs of both models (n=1). Preliminary analysis of single CTCs revealed the general concordance with the results obtained with the pooled CTCs. In conclusion, alteration in expression of several genes observed in one model was also present in the other model. The mixed alteration in both epithelial and mesenchymal markers in CTCs across both models is suggestive of a ‘hybrid’ phenotype, and EMP. Further studies will shed more light onto the nature of the gene expression changes and the role of EMP in CTCs.
This work was supported by the NHMRC ##1027527 and by the EMPathy Breast Cancer Network, a National Collaborative Research Program of the National Breast Cancer Foundation