Cistanche salsa extract induced apoptosis in the human Burkitt's lymphoma cell line Namalwa

Cistanche salsa (C.A. Meyer) G. Beck, Orobanchaceae is a parasitic plant that is used as an oriental medicinal tonic in Japan. In our preceding study, C. salsa extract dialysate (CSD) was shown to enhance IgM production in the human B cell line BALL-1 with the added effect of slightly inducing cell proliferation. In this study, we show that the CSD has the opposite effect on the human Burkitt's lymphoma cell line Namalwa. The CSD, which is prepared by removing the low-molecular-weight constituents from the extract using a 3,500 Da molecular-weight-cut-off dialysis membrane, inhibited cell growth in Namalwa. This growth inhibition was assessed by observing nuclear DNA fragmentation and measuring the percentage of sub-G₁ cells. The cells treated with the CSD showed the characteristic features for apoptosis. The nuclear DNA was shown to fragment into the characteristic “ladder” and the percentage of sub-G₁ cells was higher. These results suggest that the effect of the CSD on Namalwa is related to the activation of B cell and that apoptosis may be due to the lack of other signals, such as cytokines and cell-cell contact which is required for B cell differentiation.