Development of Novel Patient-Derived Xenografts from Breast Cancer Brain Metastases

Abstract

Brain metastases are an increasing burden among breast cancer patients, particularly for those with HER2+ and triple negative (TN) subtypes. Mechanistic insight into the pathophysiology of brain metastases and preclinical validation of therapies has relied almost exclusively on intracardiac injection of brain-homing cells derived from highly aggressive TN MDA-MB-231 and HER2+ BT474 breast cancer cell lines. Yet, these well characterized models are far from representing the tumor heterogeneity observed clinically and, due to their fast progression in vivo, their suitability to validate therapies for established brain metastasis remains limited. The goal of this study was to develop and characterize novel human brain metastasis breast cancer patient-derived xenografts (BM-PDXs) to study the biology of brain metastasis and to serve as tools for testing novel therapeutic approaches. We obtained freshly resected brain metastases from consenting donors with breast cancer. Tissue was immediately implanted in the mammary fat pad of female immunocompromised mice and expanded as BM-PDXs. Brain metastases from 3/4 (75%) TN, 1/1 (100%) estrogen receptor positive (ER+), and 5/9 (55.5%) HER2+ clinical subtypes were established as transplantable BM-PDXs. To facilitate tracking of metastatic dissemination using BM-PDXs, we labeled PDX-dissociated cells with EGFP-luciferase followed by reimplantation in mice, and generated a BM-derived cell line (F2-7). Immunohistologic analyses demonstrated that parental and labeled BM-PDXs retained expression of critical clinical markers such as ER, progesterone receptor, epidermal growth factor receptor, HER2, and the basal cell marker cytokeratin 5. Similarly, RNA sequencing analysis showed clustering of parental, labeled BM-PDXs and their corresponding cell line derivative. Intracardiac injection of dissociated cells from BM-E22-1, resulted in magnetic resonance imaging-detectable macrometastases in 4/8 (50%) and micrometastases (8/8) (100%) mice, suggesting that BM-PDXs remain capable of colonizing the brain at high frequencies. Brain metastases developed 8–12 weeks after ic injection, located to the brain parenchyma, grew around blood vessels, and elicited astroglia activation characteristic of breast cancer brain metastasis. These novel BM-PDXs represent heterogeneous and clinically relevant models to study mechanisms of brain metastatic colonization, with the added benefit of a slower progression rate that makes them suitable for preclinical testing of drugs in therapeutic settings.

LncRNA CamK-A Regulates Ca2+-Signaling-Mediated Tumor Microenvironment Remodeling

“…In Vivo Human PDX Model Based Therapeutic Study Patient-derived xenograft (PDX) models were performed to assess the clinical benefits of targeting CamK-A. PDX models were obtained as previously published reports (Contreras-Zá rate et al, 2017;Ju et al, 2017). Randomization was conducted.…”

Novel Breast Cancer Brain Metastasis Patient-Derived Orthotopic Xenograft Model for Preclinical Studies

“…In general, the engraftment rate for PDX generation varies from 4% to 80% [21,38,39]. With our novel method using a pipette with a 10-µL tip, tumors could be prepared and implanted in mouse brain to achieve 100% engraftment and tumor growth without any post-operative mortality.…”

Comparing the Fate of Brain Metastatic Breast Cancer Cells in Different Immune Compromised Mice with Cellular Magnetic Resonance Imaging

“…NSG mice are the most immunodeficient mouse strains to date, lacking T cells, B cells, NK cells, and have defective macrophages and dendritic cells [24–26]. Even fewer PDX models have been developed specific to breast cancer brain metastasis, including the novel F2-7 and E22-1 PDX cell lines [27], as well as others who have established low passage PDX models of breast cancer brain metastasis and those that implant fresh tumor tissue directly into the rodent brain [28].…”