Abstract 1525: Vortex technology for label-free enrichment of CTC from mouse xenograft models

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Abstract Background Non-invasive liquid biopsies, such as CTCs, have been of growing interest due to their potential use in cancer detection, prognosis, and monitoring of therapeutic resistance [1]. Beyond enumeration, characterization of CTCs could help guide treatment selection and the development of targeted cancer therapy. Here, we show that Vortex technology can be used successfully for the size-based capture of CTCs in a preclinical mouse model of breast cancer. Method To establish that human epithelial cancer cells can be reliably detected in small volumes of mice blood, 50-100 MDA-MB231 and MCF7 breast cancer cells were spiked in 500 μL mice blood, diluted 20 fold, and processed through Vortex chip [2]. Recovered cells were immunostained (CK, CD45, DAPI), and enumerated. For breast cancer xenograft model, 8×106 MDA-MB-231-fLuc/GFP cells were implanted orthotopically into the mammary fat pad of NOD-SCID Gamma mice (n = 35). Tumors were measured in 2 dimensions 3 times/week and tumor volume calculated. Blood from cardiac puncture (500 μl) and lateral saphenous vein (100 μl) was collected starting 1 week post implantation, diluted 40X and processed. Mice were euthanized, organs harvested, formalin fixed, paraffin embedded and H&E stained. Results Spiking of MCF7 cells in mouse blood resulted in a capture efficiency of 56.9±13% and a purity of 80.1± 9% (n = 3), with the flow-through from each cycle being re-processed for a total of 4 cycles. Recycling the flow-through led to capture efficiency of 36.7%, 23.4%, 5.2% and 7.9% during cycles 1, 2, 3 and 4 respectively. Similar results were obtained for MDA-MB-231, with a capture efficiency of 54.4% and a purity of 41.3%. In an orthotopic tumor xenograft model of breast cancer, CTCs were successfully recovered from cardiac puncture as early as day 7. CTC counts, ranging from 0.4-3649 CTCs/100 μl, increased over time and correlated with tumor burden. CTC clusters were also captured from day 7 (6 clusters/100 μl; frequency 1/3), with number and frequency increasing over time up to 147-485 clusters/100 μl by day 42. No CTC were recovered from lateral saphenous vein blood until day 28 post implantation, and their number remained low (mean 2.15±0.65). Microscopic metastases were evident in lung of all mice starting at day 28 and in liver of all mice starting at day 35. Conclusion CTCs were isolated in a label-free manner from mice blood with both high capture efficiency and purity. In a preclinical model of metastatic breast cancer, CTC counts correlated well with primary tumor volume and metastases occurrence. Thus the Vortex chip appears to be well suited for the enrichment of CTCs from murine xenograft models. Future works will focus on mice implanted with patient derived xenograft (PDX) and their therapeutic response. Information gathered from these studies should facilitate discovery of new therapeutic targets and the development of personalized medicine. [1] Ignatiadis et al. Clin Cancer Res 2015. [2] Sollier et al. Lab Chip 2014.[K.H. and M.T. contributed equally to this work.] Citation Format: Kyra Heirich, Melanie M. Triboulet, Corinne M. Renier, Vishnu C. Ramani, Elodie Sollier, Stefanie S. Jeffrey. Vortex technology for label-free enrichment of CTC from mouse xenograft models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1525.