Single cell analysis of MCF7-derived multi-organ metastases

Bone metastases can disseminate to secondary sites and promote breast cancer progression creating additional clinical challenges. The mechanisms contributing to secondary metastasis are barely understood. Here, we evaluate the prediction power of Her2+ circulating tumor cells (CTCs) after analyzing over 13,000 CTCs from a cohort of 137 metastatic breast cancer (MBC) patients with initial HR+/Her2- status and employed preclinical models of bone metastasis (BM) to validate the role of Her2+ CTCs in multi-organ metastases. While Her2+ expression was higher in patients with bone metastasis, experimental analyses revealed that a majority of these Her2+ CTCs derived from bone lesions were more dependent on Her2 activity and more susceptible to anti-Her2 treatment. Targeting the bone-mediated Her2 induction reduces CTC detection and abrogates secondary metastasis from bone. Overall, we elucidate that Her2+ CTCs can serve as a non-invasive biomarker for BM formation with high therapeutic benefit for HR+ MBC patients. Multi-organ metastasis model of MCF7 cells: Single cell analysis. 5x105 luciferase- and RFP-expressing MCF7 were injected simultaneously to the right hind limb of nude mice via intra-iliac artery inject and in the mammary fat pad of nude mice. This led to multi-organ metastasis formation in various organs including ovaries and lung. Following bioluminescence ex vivo imaging validation, various organs were enzymatically dissociated, and expanded in vitro in regular DMEM (10% FBS, 1x Pen/Strep) media for a few weeks. Cancer cells which were purified through Cell sorting based on RFP expression. Samples were sequenced using a CellPlex multiplexing approach from 10X Genomics