Triple-negative breast cancer (TNBC) liver
metastasis is associated with poor prognosis and low patient survival. It occurs when
tumor cells disseminate from primary
tumors, circulate in blood/lymph [
circulating tumor cells (CTCs)], and acquire distinct characteristics during
disease progression toward the metastatic phenotype. The purpose of this study was to decipher the genomic/transcriptomic properties of TNBC liver
metastasis and its recurrence for potential therapeutic targeting. We employed a negative depletion strategy to isolate and interrogate CTCs from the blood of patients with TNBC, and to establish sequential generations of CTC-derived xenografts (CDXs) through injection of patient CTCs in immunodeficient mice. The isolation and validation of CDX-derived cell populations [analyses of CTCs were paired with bone marrow-resident cells (BMRTCs) and liver tissue cells obtained from the same animal] were performed by multiparametric flow cytometry, immune phenotyping, and genomic sequencing of putative CTCs. Comprehensive characterization of gene expression arrays from sequentially generated CDX-derived cell populations, online gene expression arrays, and TCGA databases were employed to discover a CTC-driven, liver
metastasis-associated TNBC signature. We discovered a distinct transcriptomic signature of TNBC patient-isolated CTCs from primary TNBCs, which was consistent throughout sequential CDX modeling. We established a novel TNBC liver
metastasis-specific CDX model that selectively recapitulates CTC biology for four sequential generations of mice. The evaluation of online databases and CDX-derived populations revealed 597 genes specific to the TNBC liver
metastasis signatures. Further investigation of the TNBC liver
metastasis signature predicted 16 hub genes, 6
biomarkers with clinically available drugs, and 22 survival genes. The sequential interrogation of CDX-CTCs is an innovative liquid biopsy-based approach for the discovery of organ
metastasis-specific signatures of CTCs. This represents the first step for mechanistic and analytical validation in their application as prognostic indicators and therapeutic targets. Targeting CTC drug candidate
biomarkers along with combination
therapy can improve the clinical outcome of TNBC patients in general and recurrence of liver
metastasis in particular.