Cancer stem cells (CSCs) are potential targets for innovative anticancer
therapies that involve natural products with potential chemopreventive effects. We therefore analyzed the
antineoplastic activity of
rooperol, the aglycone of the
plant-derived compound hypoxoside, on a model of Oct4-expressing
cancer stem-like cell, i.e. the human
embryonal carcinoma (EC) cell NT2/D1.
Rooperol selectively inhibited the proliferation of NT2/D1 cells in a concentration-dependent manner and had no effect on either normal embryonic fibroblasts which are more restrictive pluripotent stem cells or on NCCIT p53-mutant EC cells. Accordingly,
rooperol only eliminates colon
carcinoma cells expressing p53.
Rooperol treatment triggered cell death on NT2/D1 cells through the alteration of mitochondrial membrane potential and production of
reactive oxygen species (ROS).
Rooperol-induced apoptosis was associated with activation of p53 and concentration-dependent changes of the expression levels of both
caspase 3 and
poly ADP ribose polymerase type 1 cleaved subunits. These modifications were accompanied by a downregulation of Oct4 and its two partners involved in the maintenance of cell pluripotency and self-renewal, Nanog and Sox2.Treatment with intracellular membrane permeant O2 (-) scavengers prevented
rooperol-induced apoptosis and upregulation of the expression of p53 and active
caspase-3. Our findings indicate that
rooperol mediates its growth inhibitory effects on CSCs via a mitochondrial redox-sensitive mechanism. We propose that abrogating the expression of the stemness regulators is a prerequisite for
rooperol to fully exert its pro-apoptotic properties on wild-type p53-bearing CSCs.