Multi-colour lineage tracing reveals intra-stage proliferative heterogeneity during mammary tumour progression

We have assessed clonal heterogeneity within individual primary tumours and metastasis and also during the distinct stages of malignant tumour progression using the Confetti lineage reporter in the background of the MMTV-PyMT mouse model of metastatic breast cancer. Comparative gene expression analysis of the clonal populations reveals a substantial level of heterogeneity across and also within the various stages of breast carcinogenesis. This intra-stage heterogeneity is manifested by differences in cell proliferation, where the fast-proliferating subclass is further enriched in oxidative phosphorylation and cell death. Outgrowth of clonal cell populations was analysed when the maximum tumour volume comprising all tumour stages (normal mammary gland, hyperplasia, adenoma, carcinoma, pulmonary metastases) had been reached in colour-induced MMTV-PyMT; R26-CBW; K8-CreERT2 mice. Zonal patches of clonal populations of the primary tumour as well as metastases were isolated by Laser Capture Microdissection (encircled regions) and samples obtained were subjected to RNA sequencing. n = 3.