Isolation and <i>In vitro</i> Propagation of Tumorigenic Breast Cancer Cells with Stem/Progenitor Cell Properties

TLDR

Breast cancer‑initiating cells, identified as CD44⁺/CD24⁻/low stem‑like cells, have been recognized in breast carcinoma, yet evidence for their in‑vitro propagation remains lacking. The study aims to isolate and propagate breast cancer‑initiating cells from patient lesions and a cell line. Cells were isolated from three breast cancer lesions and an established carcinoma cell line and cultured in vitro to generate self‑renewing, nonadherent spherical clusters. The resulting cultures contained CD44⁺/CD24⁻, Cx43⁻ cells that overexpressed neoangiogenic and cytoprotective factors, expressed Oct‑4, differentiated into ductal and myoepithelial lineages, and formed tumors from as few as 10³ cells in SCID mice, demonstrating a long‑term in‑vitro model of tumorigenic stem/progenitor cells.

Abstract

Breast cancer-initiating cells have been recently identified in breast carcinoma as CD44+/CD24(-/low) cells, which exclusively retain tumorigenic activity and display stem cell-like properties. However, at present, direct evidence that breast cancer-initiating cells can be propagated in vitro is still lacking. We report here the isolation and in vitro propagation of breast cancer-initiating cells from three breast cancer lesions and from an established breast carcinoma cell line. Our breast carcinoma-derived cultures encompassed undifferentiated cells capable of self-renewal, extensive proliferation as clonal nonadherent spherical clusters, and differentiation along different mammary epithelial lineages (ductal and myoepithelial). Interestingly, cultured cells were CD44+/CD24- and Cx43-, overexpressed neoangiogenic and cytoprotective factors, expressed the putative stem cell marker Oct-4, and gave rise to new tumors when as few as 10(3) cells were injected into the mammary fat pad of SCID mice. Long-term cultures of breast tumorigenic cells with stem/progenitor cell properties represent a suitable in vitro model to study breast cancer-initiating cells and to develop therapeutic strategies aimed at eradicating the tumorigenic subpopulation within breast cancer.