It is important to notice that although there was an important reduction in leukemic cell viability in all samples analyzed, a small cell number remained after each treatment, and it was possible that this population may include LIC with CD34+CD38+CD19+ or CD34+CD38−CD19+ cells, since a similar observation was made in 10 primary samples of T-ALL cells treated with PTL, where this cell resistance was associated with the soluble molecules produced by mesenchymal stem cells in the microenvironment [28]. The gene discussed is CD38; the disease is acute lymphoblastic leukemia.