Applying the spheroid assay as an indication of cancer stem cells, we found that MDA-MB-231-Hpa2 cells developed bigger (Fig. 6F, fourth panel) and more (Fig. 6F, lower panel) spheroids vs spheroids produced by control (Vo) cells, whereas smaller and fewer spheroids were formed by Hpa2-Nuc cells (Fig. 6F; p < 0.001 and p = 0.01 for Vo vs. Hpa2 and Vo vs. Nuc, respectively). Here, HPSE2 is linked to cancer.