From ancient herb to modern drug: Artemisia annua and artemisinin for cancer therapy

Artemisia annua L. is used throughout Asia and Africa as tea and press juice to treat malaria and related symptomes (fever, chills). Its active ingredient, artemisinin (ARS), has been developed as antimalarial drug and is used worldwide. Interestingly, the bioactivity is not restricted to malaria treatment. We and others found that ARS-type drugs also reveal anticancer in vitro and in vivo. In this review, we give a systematic overview of the literature published over the past two decades until the end of 2016. Like other natural products, ARS acts in a multi-specific manner against tumors. The cellular response of ARS and its derivatives (dihydroartemisinin, artesunate, artemether, arteether) towards cancer cells include oxidative stress response by reactive oxygen species and nitric oxide, DNA damage and repair (base excision repair, homologous recombination, non-homologous end-joining), various cell death modes (apoptosis, autophagy, ferroptosis, necrosis, necroptosis, oncosis), inhibition of angiogenesis and tumor-related signal transduction pathways (e.g. Wnt/β-catenin pathway, AMPK pathway, metastatic pathways, and others) and signal transducers (NF-κB, MYC/MAX, AP-1, CREBP, mTOR etc). ARS-type drugs are at the stairways to the clinics. Several published case reports and pilot phase I/II trials indicate clinical anticancer activity of these compounds. Because of unexpected cases of hepatotoxicity, combinations of ARS-type drugs with complementary and alternative medicines are not recommended, until controlled clinical trials will prove the safety of non-approved combination treatments.