Identifying biomarkers of breast cancer micrometastatic disease in bone marrow using a patient-derived xenograft mouse model

Abstract

BackgroundDisseminated tumor cells (DTCs) found in the bone marrow (BM) of patients with breast cancer portend a poor prognosis and are thought to be intermediaries in the metastatic process. To assess the clinical relevance of a mouse model for identifying possible prognostic and predictive biomarkers of these cells, we have employed patient-derived xenografts (PDX) for propagating and molecularly profiling human DTCs.MethodsPreviously developed mouse xenografts from five breast cancer patients were further passaged by implantation into NOD/SCID mouse mammary fat pads. BM was collected from long bones at early, serial passages and analyzed for human-specific gene expression by qRT-PCR as a surrogate biomarker for the detection of DTCs. Microarray-based gene expression analyses were performed to compare expression profiles between primary xenografts, solid metastasis, and populations of BM DTCs. Differential patterns of gene expression were then compared to previously generated microarray data from primary human BM aspirates from patients with breast cancer and healthy volunteers.ResultsHuman-specific gene expression of SNAI1, GSC, FOXC2, KRT19, and STAM2, presumably originating from DTCs, was detected in the BM of all xenograft mice that also developed metastatic tumors. Human-specific gene expression was undetectable in the BM of those xenograft lines with no evidence of distant metastases and in non-transplanted control mice. Comparative gene expression analysis of BM DTCs versus the primary tumor of one mouse line identified multiple gene transcripts associated with epithelial-mesenchymal transition, aggressive clinical phenotype, and metastatic disease development. Sixteen of the PDX BM associated genes also demonstrated a statistically significant difference in expression in the BM of healthy volunteers versus the BM of breast cancer patients with distant metastatic disease.ConclusionUnique and reproducible patterns of differential gene expression can be identified that presumably originate from BM DTCs in mouse PDX lines. Several of these identified genes are also detected in the BM of patients with breast cancer who develop early metastases, which suggests that they may be clinically relevant biomarkers. The PDX model may also provide a clinically relevant system for analyzing and targeting these intermediaries of metastases.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-017-0927-1) contains supplementary material, which is available to authorized users.

Differential Proteome Analysis of Human Neuroblastoma Xenograft Primary Tumors and Matched Spontaneous Distant Metastases

“…These attempts, however, do not reflect the entire complexity of metastasis formation as outlined above as they circumvent, e.g ., relevant steps at the primary tumor site. Therefore, we and others started to develop mouse models of spontaneous metastasis formation of human tumors, in which the single steps of the metastatic cascade are largely reflected 13 – 15 , and to characterize the tumor cells at the molecular ( e.g ., genomic) level at different metastatic stages 16 .…”

Breast cancer animal models and applications

“…These xenografts are very close to patients in terms of genetic abnormalities, gene expression profiles, pathological parameters, metastatic potential, and drug response ( DeRose et al, 2011 ). PDX models are used to identify biomarkers for personalized drug selection and to overcome the limitations of CDX transplantation in clinical treatment ( Cho et al, 2016 ; Pillai et al, 2018 ). Many institutions now build their own PDX model libraries.…”

Mouse models of breast cancer in preclinical research

“…Resulting tumors have characteristics that are similar to those of the original patients' tumors with respect to histology, genomic signature, and heterogeneity, as well as high predictive drug response [142829303132]. These models are used to identify biomarkers for personalized drug selection, and to overcome the limitation of CDX transplantation in clinical therapies [33]. While subcutaneous PDX transplantation models have been used in studies to measure primary tumor growth, orthotopic PDX transplantation models are suitable for mechanistic studies of metastasis and therapeutic resistance [34].…”