Surveillance of spontaneous breast cancer metastasis by TRAIL-expressing CD34⁺ cells in a xenograft model

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), delivered as a membrane-bound molecule expressed on the surface of adenovirus-transduced CD34+ cells (CD34-TRAIL+), was analyzed for its apoptotic activity in vitro on 12 breast cancer cell lines representing estrogen receptor-positive, HER2+ and triple-negative (TN) subtypes and for its effect on tumor growth, vascularization, necrosis, and lung metastasis incidence in NOD/SCID mice xenografted with the TN breast cancer line MDA-MB-231. Mesenchymal TN cell lines, which are the richest in putative tumor stem cells among the different breast cancer cell subtypes, were the most susceptible to apoptosis induced by CD34-TRAIL+ cel…