Western blot analysis was performed on whole cell extracts (30 µg lysate) of HEL 92.1.7 (Lane 1), Jurkat (Lane 2), HeLa (Lane 3), HeLa treated for 20 minutes with 200 mM of TPA (Lane 4), K562 (lane5), KARPAS-299 (Lane 6) and HT-29 (lane 7). The blots were probed with Anti-c-Fos Rabbit Polyclonal Antibody (Product # PA1-830, 1-3 µg/mL) and detected by chemiluminescence using Goat anti-Rabbit IgG (Heavy Chain) Superclonal™ Secondary Antibody, HRP conjugate (Product # A27036, 0.4 µg/mL, 1:2500 dilution). A 29 kDa band corresponding to c-Fos was observed across cell lines tested, A 40 kDa isoform was observed in TPA treated lysate. Known quantity of protein samples were electrophoresed using Novex® NuPAGE® 4-12 % Bis-Tris gel (Product # NP0321BOX), XCell SureLock™ Electrophoresis System (Product # EI0002) and Novex® Sharp Pre-Stained Protein Standard (Product # LC5800). Resolved proteins were then transferred onto a transferred onto a nitrocellulose membrane with Pierce™ Power Blotter System (22834). The membrane was probed with the relevant primary and secondary Antibody following blocking with 5 % skimmed milk. Chemiluminescent detection was performed using Pierce™ ECL Western Blotting Substrate (Product # 32106).