Background: Ganoderma lucidum ( G . lucidum ) is a traditional Chinese herbal medicine that has shown potential as an alternative adjuvant therapy for cancer patients. However, the mechanisms and adjuvant therapeutic effects of G . lucidum in cancer treatment remain unclear.

Methods: In this work, G . lucidum spore oil (GanoOil), a newly developed oily G . lucidum spore extract was used to investigate the mechanisms and adjuvant therapeutic effects of GanoOil in conjunction with the chemotherapeutic drug cyclophosphamide (CTX) for preventing breast cancer metastasis.

Results: In the model of lung metastasis, orally administered GanoOil increased the population of CD8 + T cells and interleukin (IL)-6 cytokine levels in mouse blood, whereas also enhancing the activity of natural killer cells in the spleen. Furthermore, the combination of GanoOil and CTX effectively suppressed the lung metastasis of circulating breast cancer cells, alleviated CTX-induced weight loss, and reduced the ratio of lung and spleen weight to body weight in mice. Moreover, high concentrations of GanoOil exhibited no significant toxicity or side effects in both in vitro and in vivo experiments.

Conclusion: In conclusion, GanoOil is a safe drug that can enhance immune activity in mice to achieve therapeutic effects on cancer, and can also synergistically inhibit tumor metastasis with CTX.