Khz (Fusion of Ganoderma lucidum and Polyporus umbellatus Mycelia) Induces Apoptosis by Increasing Intracellular Calcium Levels and Activating JNK and NADPH Oxidase-Dependent Generation of Reactive Oxygen Species

Khz is a compound derived from the fusion of Ganoderma lucidum and Polyporus umbellatus mycelia that inhibits the growth of cancer cells. The results of the present study show that Khz induced apoptosis preferentially in transformed cells and had only minimal effects on non-transformed cells. Furthermore, Khz induced apoptosis by increasing the intracellular Ca²⁺ concentration (Ca²⁺]_i) and activating JNK to generate reactive oxygen species (ROS) via NADPH oxidase and the mitochondria. Khz-induced apoptosis was caspase-dependent and occurred via a mitochondrial pathway. ROS generation by NADPH oxidase was critical for Khz-induced apoptosis, and although mitochondrial ROS production was also required, it appeared to occur secondary to ROS generation by NADPH oxidase. Activation of NADPH oxidase was demonstrated by the translocation of regulatory subunits p47^phox and p67^phox to the cell membrane and was necessary for ROS generation by Khz. Khz triggered a rapid and sustained increase in Ca²⁺]_i, which activated JNK. JNK plays a key role in the activation of NADPH oxidase because inhibition of its expression or activity abrogated membrane translocation of the p47^phox and p67^phox subunits and ROS generation. In summary, these data indicate that Khz preferentially induces apoptosis in cancer cells, and the signaling mechanisms involve an increase in Ca²⁺]_i, JNK activation, and ROS generation via NADPH oxidase and mitochondria.