Figure 7: Ferrichrome-induced apoptosis is mediated by the ER stress-responsive-JNK pathway.

The expression levels of cleaved caspase-3 and PARP in SW620 cells were increased by ferrichrome treatment in a dose-dependent manner (a). TUNEL-positive cells in SW620 cells were increased by ferrichrome treatment (0.1 μg ml⁻¹). The photographs were taken under a high-power view (× 200) (b). DDIT3 expression was assessed using a quantitative RT–PCR (c) and western blotting (d). DDIT3 was found to be highly induced (in a dose-dependent manner) in ferrichrome-treated SW620 cells. A western blotting analysis revealed the activation of the JNK signal transduction pathway in ferrichrome-treated (0.1 μg ml⁻¹) SW620 cells (e). The tumour-suppressive effect was reduced by the inhibition of JNK activation (f). A Western blotting analysis showed the elimination of cleaved caspase-3 and the induction of PARP in ferrichrome-treated (0.1 μg ml⁻¹) SW620 cells by the treatment of SP600125 (g) or siRNA of JNK (h). *P<0.05 by Student’s t-test. The error bars show the s.d. (a–e and g, n=3; f, n=5). The original unprocessed scans of the Western blots are shown in Supplementary Fig. 2.