Unlike XTEN-Killin-6S-IDCC, XTEN-Killin without coupled fluorescence dye dramatically decreased growth of the cancer cell line HT-1080 in a concentration-dependent manner and induced strong apoptosis as determined by flow cytometry (Fig 4): 10 and 5 μM concentration of XTEN-Killin caused stable growth arrest of seeded cells (about 5% of control within 24 h) and rising apoptosis, which peaked (> 40%) within 48 h. This evidence concerns the gene KLLN and cancer.