PURPL and neoplasm: As the tumor-suppressive effect after PURPL depletion may indicate PURPL regulates one of the above two types of autophagy, we performed fluorescence-activated cell sorting (FACS) analysis with Annexin V-FITC/PI double staining and found that a large portion of cells are clustered in the first quadrant, which is quite different from the death induced by apoptotic inducer staurosporine in A375 cells (Fig. 5a) and in SK-MEL-28 cells (Supplementary Fig. S2e).