Furthermore, we found that the detection of extracellular PKCδ and its suppression by E-Syt1 knockdown were confirmed under physiological conditions (10% FBS) in a cell-based assay using the HiBiT system [9] (Figure 2C), indicating that E-Syt1-mediated unconventional secretion in cancer constitutively occurs. This evidence concerns the gene ESYT1 and cancer.