Protein Isolation and Western Blot Analysis

Protein isolation and western blot analysis were performed as previously described [26 (link),37 (link)]. Briefly, protein was isolated by sonication of treated cancer cells or tumors in lysis buffer, followed by centrifugation. Protein concentration in isolated supernatant was quantified by a bicinchoninic acid assay (BCA) protein measurement method. Protein signals were detected by Super Signal West Pico Chemiluminescent substrate (Thermo Fisher Scientific) and were developed using Odyssey Fc 2800 (LI-COR Biosciences, Lincoln, NE, USA). Software ImageJ (NIH) was used quantify protein bands in Western blots. Cofilin was used as an internal protein loading control for normalizing protein signals, as cofilin’s levels were more stable than those of β-actin, under the eATP treatment.