To further address the possible role of the intracellular but not extracellular form of CYTL1 in breast cancer metabolism, we constructed a plasmid encoding ΔCYTL1, in which the 1-22 aa signal peptide of CYTL1 is lacking (Supplementary Fig. S5).8,18 In contrast to full-length CYTL1, ΔCYTL1 displayed size of about 17 kDa, but was not detected in the supernatant, suggesting complete inhibition of CYTL1 secretion. Here, CYTL1 is linked to breast cancer.