The evolving concept of pro-oxidative mechanism-based antitumor activity of
emodin (1,3,8-trihydroxy-6-methyl anthraquinone), derived mainly from in vitro studies, needs to be defined for in vivo
tumor models. The present article describes apoptosis and regression of Dalton's
lymphoma (DL) in mice by
emodin vis a vis modulations of
hydrogen peroxide (H2O2) metabolizing
antioxidant enzymes in the
tumor cells in vivo. A non-toxic dose (40 mg/kg bw) of
emodin, given intraperitoneally to the DL bearing mice daily up to 12th post DL
transplantation day, caused a significant decline (P < 0.05) in the number of viable DL cells and could significantly increase life span of the DL mice (P < 0.01). A significant decline in Bcl2/Bax ratio consistent with the release of mitochondrial
cytochrome c release in DL cells from
emodin-treated DL mice suggested that
emodin could induce mitochondrial pathway of apoptosis in the DL cells in vivo. Apoptosis of DL cells by
emodin was further confirmed by the appearance of smaller
DNA fragments on
DNA ladder analysis. Over activation of both, the Cu-Zn-
superoxide dismutases (SOD1) and
Mn-SOD (SOD2), has been found correlated with the
tumor suppression.
Emodin caused significant increases in the expression and activity of SOD1 and SOD2 in the DL cells. H2O2 produced by SODs is degraded by
catalase and
glutathione peroxidase in the cells. Both these
enzymes were observed to be declined significantly with a concomitant increment in H2O2 concentration (P < 0.01) in the DL cells from
emodin-treated DL mice. It is concluded that
emodin is able to induce mitochondrial pathway of apoptosis in the DL cells in vivo via reciprocal modulations of H2O2 producing and degrading
antioxidant enzymes.