Regulation of interferon-inducible proteins by doxorubicin via IFN-alpha-JAK-STAT signaling in tumor cells

Activation of the immune system is a way for host tissue to defend itself against tumor growth. Hence, treatment strategies that are based on immunomodulation are on the rise. Conventional cytostatic drugs such as the anthracycline doxorubicin can also activate immune cell functions of macrophages and natural killer cells. In addition, cytotoxicity of doxorubicin can be enhanced by combining this drug with the cytokine IFN-alpha. Although doxorubicin is one of the most applied cytostatics, the molecular mechanisms of its immunomodulation ability are not investigated thoroughly. In microarray analyses of HeLa cells, a set of 19 genes related to interferon signaling was significantly overrepresented among genes regulated by doxorubicin exposure including STAT-1, -2, IRF9, NMI, and caspase 1. Regulation of these genes by doxorubicin was verified with Real-Time PCR and immunoblotting. An enhanced secretion of IFN-alpha was observed when HeLa cells were exposed to doxorubicin as compared to untreated cells. IFN-alpha neutralizing antibodies and inhibitors of JAK-STAT signaling (ATA and AG490) significantly abolished doxorubicin-stimulated expression of interferon signaling-related genes. Furthermore, inhibition of JAK-STAT signaling significantly reduced doxorubicin induced caspase 3 activation and desensitized HeLa cells to doxorubicin cytotoxicity. In conclusion, we demonstrate that doxorubicin induces interferon-responsive genes via IFN-alpha-JAK-STAT1 signaling and that this pathway is relevant for doxorubicins cytotoxicity in HeLa cells. As immunomodulation is a promising strategy in anticancer treatment, this novel mode of action of doxorubicin may help to further improve the use of this drug among different types of anticancer treatment strategies.

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Hussner J, Ameling S, Hammer E, Herzog S, Steil L, Schwebe M, Niessen J, Schroeder HW, Kroemer HK, Ritter CA, Völker U, Bien S