Treatment of A375 cells with PA (15 μM) for different time points iTRAQ Labeling Pool, SCX, Desalting and Offline 2DLC MS/MS analysis Cell Lysis, Reduction, Alkylation, and Tryptic Digestion 0 h 4 h12h24h 0 h4 h12h24h Biological replicate 1Biological replicate 2 Data Analysis Supporting Information Figure S1. (A) Schematic representation of the experimental design of the iTRAQ-based quantitative proteomics study. (B) Schematic representation of the data analysis pipeline of the proteomics results. A B Supporting Information Figure S1

Supporting Information Figure S2 (A) Cell viabilities of A375 melanoma cells after 24 h treatment with PA as determined by MTT assay. (B) Accumulation of vesicles on PA-treated A375 cells observed under inverted light microscope. (C) Real-time growth profile of A375 cells in response to treatment with PA. 60 µM 30 µM 15 µM 7.5 µM 3.75 µM 1.88 µM Untreated Control A B CTRLPA (15 μM) C Supporting Information Figure S2

Supporting Information Figure S3. (A) Enlargement of mitochondria of PA-treated SK-MEL-28 melanoma cells. Arrows showing vesicles accumulated upon PA treatment. Images were acquired using Cellomics ArrayScan HCS Reader. (B) Decrease abundance of COX IV and loss of MMP in PA-treated SK-MEL-28 melanoma cells. Representative images of three independent experiments were shown. Average fluorescent intensities of COX IV and MMP dye were quantified using CHP algorithm on the HCS platform. (C) Upregulation of HSPA5 and CHOP protein in PA-treated SK-MEL-28 melanoma cells. Data are expressed as means ± SEM of three independent experiments. Statistical significance is expressed as ***, P < 0.001; **, P < 0.01 versus untreated control. Supporting Information Figure S3

Supporting Information Figure S4. (A) Correlation plot for the two biological replicates of 0 h control (N=4092). (B) Correlation plot for the two biological replicates of 0 h control (N=296). Supporting Information Figure S4

Supporting Information Figure S5. Correlation plots for the two biological replicates of (A) 4 h post-treatment with PA (N=35). (B) 12 h post-treatment with PA (N=145). (C) 24 h post-treatment with PA (N=245). Supporting Information Figure S5