Crosstalk of signaling pathways in inflammation and cancer

The development of castration resistant prostate cancer (CRPC) remains one major challenge during androgen ablation therapy (ADT) of prostate cancer patients. Besides the Androgen Receptor (AR) and Phosphatase tensin homologue (PTEN), it has been shown that the NF-B signaling pathway and the genomic gene fusion TMPRSS2-ERG have an important role for the development of CRPC. Moreover, these four factors share a significant amount of crosstalk. Our data indicates that the activation of the AR signaling pathway leads to a down-regulation of NF-B mediated signaling. Additional data indicates that the molecular mechanism does involve post-translational modification(s) of p65, which is mediated by the acetyl-transferase p300. Furthermore, PTEN deficiency appears associated with an up-regulation of NF-B signaling. Finally, our results suggest that up-regulation of TMPRSS2-ERG through AR might represent a hitherto unknown bypass mechanism, which could substitute for low NF-B activity in the presence of active AR. In the present study, we want to further investigate the crosstalk of AR, PTEN, NF-B and TMRPSS2- ERG mediated signaling in cell culture and mouse models for prostate cancer and link the results to data obtained from patient material. In particular, we want to test whether modulation of AR activity is correlated with the acetylation/de-acetylation status of p65 and the activity of NF-B in vitro and in vivo. To that end we intend to perform a series of experiments including reporter gene assays, Avidin Biotin complex DNA (ABCD) assays and androgen ablation experiments in prostate cancer cells, NF-B reporter mice and mouse models for prostate cancer. Additionally, we want to determine the influence of PTEN deficiency in regards to AR and NF-B signaling. We further intend to perform a series of in vitro and in vivo experiments in the presence of the p300 inhibitor C646. This approach should unveil whether p300 is an important downstream mediator of AR signaling and whether it is necessary for acetylation status of p65 and NF-B activity in that context. Finally we want to unravel whether the TMPRSS2-ERG gene fusion can bypass the AR mediated down-regulation of the NF-B pathway. Since we have shown already that TMPRSS2-ERG can directly bind to NF-B consensus binding sites, we would like to perform chromatin immunoprecipitation experiments followed by sequencing analysis (ChIPseq), to identify common TMPRSS2-ERG and NF- B dependent target genes in prostate cancer cells. We further intend to analyze compound transgenic mice characterized by a combination of ERG over-expression and an enhanced NF-B activity in the prostate. We are convinced that this approach will shed light on the complex relations of AR, PTEN, NF-B and TMRPSS2-ERG during the development of prostate cancer and will help to build up new drug combination strategies for therapy.

Prostate cancer is one of the leading causes of cancer death in men. Primary prostate cancer is usually treated through surgery or radiation therapy. In case that the cancer does progresses to an advanced or metastatic disease, standard therapy normally involves blocking of androgen receptor signaling, which is essential for proliferation of prostate epithelial cells, either by using androgen- receptor antagonists or by interfering with the synthesis of androgens. This treatment is referred to as androgen-deprivation therapy (ADT). After an initial regression of the cancer (usually 18-24 months), the therapy almost inevitably leads to the development of castration resistant prostate cancer (CRPC). CRPC is characterized by a relapse of tumor growth, new metastatic spread and represents a lethal form of the disease. There is an established link between ADT, cardiovascular diseases (CVD) and thrombosis. CVDs are a major cause of non-cancer-related mortality in men with prostate cancer. Furthermore, it has previously been shown that ADT increase the rate of venous thromboembolism (VTE) in prostate cancer patients. We could now could show that ADT induces Tissue Factor expression in prostate epithelial cells, which might account for elevated VTE rates in prostate cancer patients. Furthermore, we established a novel signaling hub involving the prostate cancer specific TMPRSS2-ERG gene fusion the MAPK pathway and Tissue factor.