Both are based on the ability of the purging agent (in this case, a virus that does not infect normal human HSPCs) to distinguish the disease-inducing cells (either contaminating cancer cells in autologous grafts or resident alloreactive donor T lymphocytes in allogeneic grafts) from the normal stem cells whose immune-reconstituting functions must be maintained (in this case CD34+ HSPCs). This evidence concerns the gene CD34 and cancer.