Echinacea purpurea and melatonin augment natural-killer cells in leukemic mice and prolong life span

Objective: We recently showed that daily dietary administration of Echinacea purpurea root extract to normal mice for as little as 1 week resulted in significant elevations of natural-killer (NK) cells (immune cells that are cytolytic to virus-containing cells and many tumor cells). Such boosting of this fundamental immune cell population suggests a prophylactic role for this herb in normal animals. Based on this evidence, our goal in the present work was to assess the role of dietary administration of this herbal extract to mice bearing leukemia, a type of tumor well known to be a target for NK cells. Design: A commercially available root extract of E. purpurea, which we have already shown to be highly effective in mice, was administered daily for 50 days from the onset of leukemia (day 0). Control leukemic mice received no extract. Other leukemic mice received the NK-enhancing neurohormone, melatonin, administered precisely as above. In all treatment and control categories, some mice were sampled at 9 days after tumor onset, others were sampled at 3 months, and still others were left to assess treatment effect on life span. Results: At 9 days (intermediate stage leukemia; death beginning by day 17-18), E. purpurea-treated mice had a 2.5-fold increase in the absolute numbers of NK cells in their spleens. By 3 months after leukemia onset, E. purpurea-treated mice still had 2-3 times the normal numbers of NK cells in their spleens. No leukemic, untreated (control) mice remained alive at 3 months, hence the comparison with normal animals. Moreover, at 3 months post-tumor onset, all the major hemopoietic and immune cell lineages in their bone marrow birth site, were recorded at normal numbers, in E. purpurea-consuming, leukemic mice. The survival advantage provided by administering these leukemic mice with E. purpurea was highly significant versus untreated, leukemic mice when analyzed by Kaplan-Meier survival statistics. Conclusion: The present study has provided the first systematic analysis, under controlled laboratory conditions, of the effect(s) of the botanical, E. purpurea, in vivo, in leukemic hosts. The profoundly positive effects of this herb in disease abatement observed in this study suggest the therapeutic potential of E. purpurea, at least with respect to leukemia, if not other tumors as well.