In vitro cultures of circulating tumor cells: a potential tool to unravel drug sensitivity

Fast and efficient isolation of murine circulating tumor cells using screencell technology for pre-clinical analyzes

Circulating tumor cells (CTCs) represent a rare and heterogeneous population of cancer cells that are detached from the tumor site and entered blood or lymphatic circulation. Once disseminated in distant tissues, CTCs could remain dormant or create a tumor mass causing serious danger for patients. Many technologies exist to isolate CTCs from patients' blood samples, mostly based on microfluidic systems or by sorting them according to their surface antigens, notably EpCAM, and/or cytokeratins for carcinoma. ScreenCell has developed an easy-to-use, antigen-independent, rapid, cost-effective, and efficient technology that isolates CTCs according to their bigger size compared to the blood cells. This study provides the technical information necessary to isolate and characterize CTCs from mouse blood. By using blood samples from transgenic mice with breast cancer or from WT mice in which we spiked cancer cells, we showed that ScreenCell technology is compatible with standard EDTA blood collection tubes. Furthermore, the ScreenCell Cyto kit could treat up to 500 µl and the ScreenCell MB kit up to 200 µl of mouse blood. As the ScreenCell MB kit captures unaltered live CTCs, we have shown that their DNA could be efficiently extracted, and the isolated cells could be grown in culture. In conclusion, ScreenCell provides a rapid, easy, antigen-independent, cost-effective, and efficient technology to isolate and characterize CTCs from the blood samples of cancer patients and murine models. Thanks to this technology CTCs could be captured fixed or alive. Murine cancer models are extensively used in pre-clinical studies. Therefore, this study demonstrates the crucial technical points necessary while manipulating mouse blood samples using ScreenCell technology.

Circulating Tumor Cells in Cancer Diagnostics and Prognostics by Single-Molecule and Single-Cell Characterization

Circulating tumor cells (CTCs) represent an interesting source of biomarkers for diagnosis, prognosis, and the prediction of cancer recurrence, yet while they are extensively studied in oncobiology research, their diagnostic utility has not yet been demonstrated and validated. Their scarcity in human biological fluids impedes the identification of dangerous CTC subpopulations that may promote metastatic dissemination. In this Perspective, we discuss promising techniques that could be used for the identification of these metastatic cells. We first describe methods for isolating patient-derived CTCs and then the use of 3D biomimetic matrixes in their amplification and analysis, followed by methods for further CTC analyses at the single-cell and single-molecule levels. Finally, we discuss how the elucidation of mechanical and morphological properties using techniques such as atomic force microscopy and molecular biomarker identification using nanopore-based detection could be combined in the future to provide patients and their healthcare providers with a more accurate diagnosis.

Embryonated Chicken Tumor Xenografts Derived from Circulating Tumor Cells as a Relevant Model to Study Metastatic Dissemination: A Proof of Concept

Simple Summary

Circulating Tumor Cells (CTCs) are heterogeneous and rare in the bloodstream, but responsible for cancer metastasis. Their in vitro or in vivo expansion remains a major challenge. The chicken Chorioallantoic Membrane (CAM) assay has proven to be a reliable alternative to the murine model, notably for tumor xenografts. We have developed a promising model of CTC-derived xenografts in the chicken CAM and demonstrated the feasibility of Next Generation Sequencing (NGS) analysis in this assay, with a genomic concordance between the in ovo tumor and the original patient’s tumor. We also evidenced metastatic dissemination from the xenograft in the chicken embryo’s distant organs. Further characterization of the in ovo tumors and metastases may provide new insights into the mechanisms of tumor dissemination. The development of a xenograft from a given patient’s CTCs, in a time frame compatible with managing the patient’s treatment, could also be a step forward towards personalized medicine.

Abstract

Patient-Derived Xenografts (PDXs) in the Chorioallantoic Membrane (CAM) are a representative model for studying human tumors. Circulating Tumor Cells (CTCs) are involved in cancer dissemination and treatment resistance mechanisms. To facilitate research and deep analysis of these few cells, significant efforts were made to expand them. We evaluated here whether the isolation of fresh CTCs from patients with metastatic cancers could provide a reliable tumor model after a CAM xenograft. We enrolled 35 patients, with breast, prostate, or lung metastatic cancers. We performed microfluidic-based CTC enrichment. After 48–72 h of culture, the CTCs were engrafted onto the CAM of embryonated chicken eggs at day 9 of embryonic development (EDD9). The tumors were resected 9 days after engraftment and histopathological, immunochemical, and genomic analyses were performed. We obtained in ovo tumors for 61% of the patients. Dedifferentiated small tumors with spindle-shaped cells were observed. The epithelial-to-mesenchymal transition of CTCs could explain this phenotype. Beyond the feasibility of NGS in this model, we have highlighted a genomic concordance between the in ovo tumor and the original patient’s tumor for constitutional polymorphism and somatic alteration in one patient. Alu DNA sequences were detected in the chicken embryo’s distant organs, supporting the idea of dedifferentiated cells with aggressive behavior. To our knowledge, we performed the first chicken CAM CTC-derived xenografts with NGS analysis and evidence of CTC dissemination in the chicken embryo.