Metastases at distant sites are the main cause of death from breast cancer but there are few cell lines derived from distant organs that represent the spectrum of normal breast cancer metastasis patterns. We have successfully established a breast cancer cell line from a bone metastatic lesion of a breast cancer patient, which we have designated as BCBM1 (Breast Cancer Bone Metastasis 1), and have performed expression and copy number profiling on it, and the matched primary tumour.
The BCBM1 cell line grows as an adherent monolayer and can be maintained continuously in vitro. Phase contrast microscopy identifies a heterogeneous population where most cells have a spindle-like epithelial morphology, some have fibroblast-like morphology and others are giant, multinucleated cells. Immunofluorescence shows BCBM1 cells are triple negative for oestrogen receptor, progesterone receptor and HER2. Cells are heterogeneously positive for epidermal growth factor, have low expression of cytokeratins 8/18 and 19 but are 100% positive for vimentin. Flow cytometry analysis shows BCBM1 cultures are predominantly CD44+/CD49f+/EpCAM-, consistent with a primitive, mesenchymal-like phenotype. BCBM1 retains copy number alterations that were present in the matched primary tumour but also contains additional alterations, some of which may be involved in metastasis. Homozygous deletions detected in the cell line that were also evident in the primary tumour were found in regions that contained known tumour suppressor genes (CDKN2A, CDKN2B and CDKN1B) and 23 putative tumour suppressors: MTAP, C9orf53, CDKN2B-AS1, DMRTA1, ELAVL2, TUSC1, C9orf82, IFT74, PLAA, LRRC19, TEK, C9orf11, IFNK, MOBKL2B, C9orf72, LINGO2, ACO1, CREBL2, GPR19, APOLD1, APAF1, HTA and ZFHX3. Cell line specific gene amplification, coupled with over-expression, identified 23 genes with potential pro-metastatic function: PDCD10, TMEM106B, HOXA13, ADAM9, GOLGA7, GINS4, MED27, DDX31, SURF6, PFKP, KLF6, ITIH5, PFKPB3, PRKCQ, UPF2, NUDT5, CDC123, HSPA14, ARL5B, MLLT10, MASTL, MKX and CDK8. Tail-vein injection of BCBM1 cells into BALBc/nude mice produced metastases in the bone, brain and lung.
The BCBM1 is a new addition to the breast cancer cell line resource that can be used in pre-clinical therapeutic trials and to improve understanding of breast cancer cell biology.