Dive into Single, Seek Out Multiple: Probing Cancer Metastases via Single-Cell Sequencing and Imaging Techniques.

Shang Su,Xiaohong Li

doi:10.3390/cancers13051067

Abstract

Simple SummaryTreating cancer metastasis is the biggest challenge in clinical practice. It is largely due to our limited understanding of the complex process, which involves not only the evolution and/or selection of heterogeneous primary tumor cells to metastatic tumors, but also interaction and/or adaption with various types of cells in different microenvironments, including temporally in the circulation system. These limitations are currently resolved by single-cell technologies. This review summarizes recent applications of single-cell technologies in metastatic studies, highlights the unique findings, and discusses the future directions. Metastasis is the cause of most cancer deaths and continues to be the biggest challenge in clinical practice and laboratory investigation. The challenge is largely due to the intrinsic heterogeneity of primary and metastatic tumor populations and the complex interactions among cancer cells and cells in the tumor microenvironment. Therefore, it is important to determine the genotype and phenotype of individual cells so that the metastasis-driving events can be precisely identified, understood, and targeted in future therapies. Single-cell sequencing techniques have allowed the direct comparison of the genomic and transcriptomic changes among different stages of metastatic samples. Single-cell imaging approaches have enabled the live visualization of the heterogeneous behaviors of malignant and non-malignant cells in the tumor microenvironment. By applying these technologies, we are achieving a spatiotemporal precision understanding of cancer metastases and clinical therapeutic translations.

Highlights

Published: 3 March 2021Metastasis is the leading cause of cancer death and has long been a major issue in cancer research [1,2]
Single-cell sequencing has provided unprecedented advantages and resolution in understanding cancer metastasis, including how individual cells of the metastatic tumor evolve, how heterogeneity forms, and how the cells differ in their physiological behavior or responses to therapies, spatially and temporally
Singlecell sequencing (SCS) is not being used as a tool to make treatment decisions just yet, it is paving the way for precision medicine and individualized treatment at a higher level with apparently improved detections at protein, RNA and gene levels

Summary

Introduction

Metastasis is the leading cause of cancer death and has long been a major issue in cancer research [1,2]. Cancer cells detach from the primary tumor mass and enter the circulation, i.e., intravasate primarily into the bloodstream but may enter the lymphatic system. These cancer cells are named circulating tumor cells (CTCs). The CTCs extravasate, i.e., exit from the vessels when they arrive at distant sites such as the bone, brain, lung, or liver These cells are named disseminated tumor cells (DTCs). Macrometastases may have already undergone some essential but transient events along the metastasis cascade from colonization to micrometastases Due to these unknown essentials, there is no precision therapy to prevent or target metastasis. This review will focus on the recent advances in applications of single-cell sequencing and imaging, separately or in combination, in studies of cancer metastases

The Overall Experiment Flow

Single-Cell Capture and Nucleic Acid Isolation

Library Preparation and Sequencing

Data Processing

Spatial Understanding

Temporal Understanding

Single-Cell Epigenomic Sequencing and Emerging Multi-Omics

Summary and Future Perspectives

Seeing Is Believing

Know Your Samples

Tissue Clearance

Transparent Animal Model