A profound cytotoxic action of the antimalarial, artesunate (ART), was identified against 55 cancer cell lines of the U.S. National Cancer Institute (NCI). The 50% inhibition concentrations (IC 50 values) for ART correlated significantly to the cell doubling times (P ϭ 0.00132) and the portion of cells in the G 0 /G 1 (P ϭ 0.02244) or S cell cycle phases (P ϭ 0.03567). We selected mRNA expression data of 465 genes obtained by microarray hybridization from the NCI data base. These genes belong to different biological categories (drug resistance genes, DNA damage response and repair genes, oncogenes and tumor suppressor genes, apoptosis-regulating genes, proliferation-associated genes, and cytokines and cytokine-associated genes). The constitutive expression of 54 of 465 (ϭ12%) genes correlated significantly to the IC 50 values for ART. Hierarchical cluster analysis of these 12 genes allowed the differentiation of clusters with ART-sensitive or ART-resistant cell lines (P ϭ 0.00017). For exemplary validation, cell lines transduced with 3 of the 12 genes were used to prove a causative relationship. The cDNAs for a deletion-mutated epidermal growth factor receptor (EGFR) and for ␥-glutamylcysteine synthetase increased resistance to ART. The conditional expression of the CDC25A gene using a tetracycline repressor expression vector increased sensitivity toward ART. Multidrug-resistant cells differentially expressing the MDR1, MRP1, or BCRP genes were not cross-resistant to ART. ART acts via p53-dependent andindependent pathways in isogenic p53ϩ/ϩ p21 WAF1/CIP1 ϩ/ϩ, p53Ϫ/Ϫ p21 WAF1/CIP1 ϩ/ϩ, and p53ϩ/ϩ p21 WAF1/CIP1

Antiviral therapy of primary and recurrent infections with human cytomegalovirus is reserved for severe manifestations and faces several limitations. Presently candidates for novel drugs with lower adverse side effects and a minimized frequency of resistance formation are under investigation. Here we demonstrate that artesunate, an antimalaria drug with highly valuable pharmacological properties, possesses antiviral activity. A concentration-dependent inhibition of the replication of human cytomegaloviruses with wild-type phenotype was demonstrated in several cell lines. Inhibition was quantified using recombinant green fluorescent protein expressing virus variants. The IC50 values were in the same range for ganciclovir-sensitive and ganciclovir-resistant human cytomegalovirus, as calculated with 5.8+/-0.4 microM and 6.9+/-0.2 microM, respectively. This indicated a strong antiviral potential and a lack of cross-resistance. The optimal antiviral concentrations of artesunate were separable from those inducing cytotoxicity. In addition, the replication of viruses from three genera was seen to be artesunate-sensitive to varying degrees. This suggests a mechanism linked to cellular activation pathways. Both the protein levels and the DNA binding activity of the two virus-induced cellular transcription factors Sp1 and NF-kappaB were found to be markedly reduced in the presence of artesunate. We also analyzed the cellular signaling kinase phosphoinositide 3-kinase, required for the activation of factors such as Sp1 and NF-kappaB in infected fibroblasts. The phosphorylation of two downstream effectors of phosphoinositide 3-kinase, Akt and p70S6K, was markedly inhibited in the presence of artesunate. Thus, artesunate possesses attractive antiviral characteristics which are suggestively based on the interference with essential steps in the host cell kinase cascades.

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