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. This evidence concerns the gene CYTL1 and breast carcinoma.