Novel Strategy for Lineage Tracing of Cancer Stem Cells

Abstract

The cancer stem cell (CSC) theory hypothesizes a subset of the tumorigenic cells able to self‐renew and wholly reconstitute original tumors by lineage restriction. We developed a lentiviral barcoding system as a means of genetic lineage tracing of cell subpopulations sorted by surface marker expression to investigate the proliferation kinetics, plasticity and clonality of tumor‐initiating cells (TICs). The abundance of each barcode in the reconstituted tumor reflects the frequency of TIC progeny in individual cell fractions. We determined that the CD29H/CD24H subfraction consistently out‐competes other subfractions while forming populations of different immune‐profiles, indicating that this subfraction retains the two cardinal features of self‐renewal and ability to give rise to progeny through lineage restriction ascribed to TICs, and suggests that not a lot of plasticity happens between non‐TICs and TICs. Also, iPCR was successfully applied into the lentiviral barcoding system, enabling the analysis of the TIC's clonality over serial transplant passages to understand the CSC's hierarchy. This novel lentiviral barcoding strategy provides future framework for defining specific biomarkers and evaluating therapeutics directed towards CSCs. This lineage tracing methodology should be applicable not only to genetically engineered mouse models but also to primary human breast cancer xenografts.