No abstract

Hodgkin/Reed-Sternberg lymphoma (HL) is a clonal B-cell-related malignancy. Although many patients with HL can be cured by the current regimen of high-dose multi-agent chemotherapy, the treatment causes high risks of later pathologies including secondary malignancies. This fact highlights the demand to develop rational treatment for HL. Survival and growth of HL cells are largely dependent on their microenvironment. In this study, using the HL cell lines L1236 and KM-H2 as model systems, we investigated the role of IL-4/IL-13 signaling in regulation of drug sensitivity and resistance in HL. We show that specific blocking of IL-4 and IL-13-mediated STAT6 activation by either an IL-4-binding fusion protein APG598 or an IL-4R antagonist APG201 (R121D/Y124D) renders HL cells more prone to apoptotic killing by chemotherapeutic drugs such as Mitomycin C, 5-Fluorouracil, Etopside, Doxorubicin and Paclitaxel. This effect is due to inhibition of STAT6-mediated elevation of expression of the anti-apoptotic Bcl-2 family protein Bcl-xL. Employing ChIP analysis in combination with APG201 or STAT6-specific siRNA we identified a defined STAT6-binding site in the Bcl-xL promoter region from 21967 to 21957 of the transcription start site. Our data demonstrate that the IL-4/IL-13-STAT6-Bcl-xL axis may be an important target for HL treatment. This study also suggests that combination of classical chemotherapeutic drugs with the IL-4/IL-13 antagonists may enhance efficacy and reduce risks of toxicity from high dose of drugs in HL treatment.The current treatment of Hodgkin lymphoma (HL) involves multi-drug chemotherapy and/or radiotherapy.1 Although 80-90% of HL patients can be salvaged by using such treatment, one major risk is that HL patients are more likely to die from late treatment-related toxicities than from HL itself.2,3 This fact highlights the demand to develop rational treatment for HL.Targeting specific cancer survival pathways would be a promising approach to improve HL therapy. It has been evidenced that cytokine-mediated Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) signaling plays a fundamental role in tumor development and progression. Abnormal activation of STAT proteins, in particular STAT3 and STAT6, has been found with high frequency in a wide variety of human cancers including HL.4,5 Consequently, inhibition of the JAK/STAT pathway results in reduction of tumor proliferation and survival. 6,7 STAT6 is specifically activated in response to binding of interleukin 13 (IL-13) to its cognate receptors on the cell surface. Accumulating evidence demonstrates that co-expression of IL-13 and its specific receptor IL-13Ra1 is a common feature of HL cells. 8 In addition, STAT6 may also be activated due to high frequency of genetic lesions in the suppressors of cytokine signaling-1 (SOCS1) in HL. 9,10 Growth of HL cells has been shown to be dependent on STAT3 and STAT6 activation, as abrogation of their activation by neutralizing antibodies, JAK/STAT blockers or siRNAs against STAT3 and STAT6 re...

The pleiotropic cytokine tumor necrosis factor alpha (TNF-alpha) can induce apoptosis but also supports cell survival pathways. Among the possible anti-apoptotic mechanisms of TNF-alpha is the activation of the transcription factor NF-kappaB. Since reactive oxygen species (ROS) are assumed to contribute to TNF-alpha mediated cytotoxicity but can also facilitate NF-kappaB activation this study investigates the relationship between TNF-alpha treatment, NF-kappaB activation and the expression of the anti-oxidative enzyme catalase. TNF-alpha treatment caused downregulation of catalase expression in MCF-7, Caco-2 and Hct-116 cancer cell lines. Overexpression of catalase in MCF-7 cells, resulting in lower intracellular ROS levels upon challenge with H(2)O(2), caused a transient nuclear p65 translocation upon TNF-alpha treatment as compared to the sustained NF-kappaB activation in wild type cells. This was due to a lack of sufficient H(2)O(2) to co-stimulate NF-kappaB activation as demonstrated by the observation that addition of exogenous H(2)O(2) led to a second increase of NF-kappaB activity. The rapid decline of nuclear translocation of NF-kappaB in the catalase overexpressing cells resulted in a slower increase of NF-kappaB mediated reporter gene expression. These results indicate that TNF-alpha mediated downregulation of catalase expression and accordingly sufficient H(2)O(2) is required for appropriate function of the NF-kappaB dependent survival pathway.