Jan Pencik

STAT3 regulated ARF expression suppresses prostate cancer metastasis.

Prostate cancer (PCa) is the most prevalent cancer in men. Hyperactive STAT3 is thought to be oncogenic in PCa. However, targeting of the IL-6/STAT3 axis in PCa patients has failed to provide therapeutic benefit. Here we show that genetic inactivation of Stat3 or IL-6 signalling in a Pten-deficient PCa mouse model accelerates cancer progression leading to metastasis. Mechanistically, we identify p19ARF as a direct Stat3 target. Loss of Stat3 signalling disrupts the ARF–Mdm2–p53 tumour suppressor axis bypassing senescence. Strikingly, we also identify STAT3 and CDKN2A mutations in primary human PCa. STAT3 and CDKN2A deletions co-occurred with high frequency in PCa metastases. In accordance, loss of STAT3 and p14ARF expression in patient tumours correlates with increased risk of disease recurrence and metastatic PCa. Thus, STAT3 and ARF may be prognostic markers to stratify high from low risk PCa patients. Our findings challenge the current discussion on therapeutic benefit or risk of IL-6/STAT3 inhibition.

JAK-STAT signaling in cancer: From cytokines to non-coding genome

In the past decades, studies of the Janus kinases (JAKs) and signal transducers and activators of transcription (STATs) signaling have uncovered highly conserved programs linking cytokine signaling to the regulation of essential cellular mechanisms such as proliferation, invasion, survival, inflammation and immunity. Inhibitors of the JAK/STAT pathway are used for treatment of autoimmune diseases, such as rheumatoid arthritis or psoriasis. Aberrant JAK/STAT signaling has been identified to contribute to cancer progression and metastatic development. Targeting of JAK/STAT pathway is currently one of the most promising therapeutic strategies in prostate cancer (PCa), hematopoietic malignancies and sarcomas. Notably, newly identified regulators of JAK/STAT signaling, the non-coding RNAs transcripts and their role as important targets and potential clinical biomarkers are highlighted in this review. In addition to the established role of the JAK/STAT signaling pathway in traditional cytokine signaling the non-coding RNAs add yet another layer of hidden regulation and function. Understanding the crosstalk of non-coding RNA with JAK/STAT signaling in cancer is of critical importance and may result in better patient stratification not only in terms of prognosis but also in the context of therapy.

Increased survival and cell cycle progression pathways are required for EWS/FLI1-induced malignant transformation

Ewing sarcoma (ES) is the second most frequent childhood bone cancer driven by the EWS/FLI1 (EF) fusion protein. Genetically defined ES models are needed to understand how EF expression changes bone precursor cell differentiation, how ES arises and through which mechanisms of inhibition it can be targeted. We used mesenchymal Prx1-directed conditional EF expression in mice to study bone development and to establish a reliable sarcoma model. EF expression arrested early chondrocyte and osteoblast differentiation due to changed signaling pathways such as hedgehog, WNT or growth factor signaling. Mesenchymal stem cells (MSCs) expressing EF showed high self-renewal capacity and maintained an undifferentiated state despite high apoptosis. Blocking apoptosis through enforced BCL2 family member expression in MSCs promoted efficient and rapid sarcoma formation when transplanted to immunocompromised mice. Mechanistically, high BCL2 family member and CDK4, but low P53 and INK4A protein expression synergized in Ewing-like sarcoma development. Functionally, knockdown of Mcl1 or Cdk4 or their combined pharmacologic inhibition resulted in growth arrest and apoptosis in both established human ES cell lines and EF-transformed mouse MSCs. Combinatorial targeting of survival and cell cycle progression pathways could counteract this aggressive childhood cancer.

STAT5BN642H is a driver mutation for T cell neoplasia

STAT5B is often mutated in hematopoietic malignancies. The most frequent STAT5B mutation, Asp642His (N642H), has been found in over 90 leukemia and lymphoma patients. Here, we used the Vav1 promoter to generate transgenic mouse models that expressed either human STAT5B or STAT5BN642H in the hematopoietic compartment. While STAT5B-expressing mice lacked a hematopoietic phenotype, the STAT5BN642H-expressing mice rapidly developed T cell neoplasms. Neoplasia manifested as transplantable CD8+ lymphoma or leukemia, indicating that the STAT5BN642H mutation drives cancer development. Persistent and enhanced levels of STAT5BN642H tyrosine phosphorylation in transformed CD8+ T cells led to profound changes in gene expression that were accompanied by alterations in DNA methylation at potential histone methyltransferase EZH2-binding sites. Aurora kinase genes were enriched in STAT5BN642H-expressing CD8+ T cells, which were exquisitely sensitive to JAK and Aurora kinase inhibitors. Together, our data suggest that JAK and Aurora kinase inhibitors should be further explored as potential therapeutics for lymphoma and leukemia patients with the STAT5BN642H mutation who respond poorly to conventional chemotherapy.

Breaking a paradigm: IL-6/STAT3 signaling suppresses metastatic prostate cancer upon ARF expression

ABSTRACT Interleukin 6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) signaling is considered to have important oncogenic functions in prostate cancer (PCa). However, a recent study highlighted the central role of IL-6/STAT3 signaling in regulation of the ARF–MDM2–p53 senescence axis. This reversal of the postulated oncogenic properties of IL-6/STAT3 signaling in PCa has important therapeutic implications.

IL-6/STAT3/ARF: the guardians of senescence, cancer progression and metastasis in prostate cancer.

Prostate cancer is one of the most prevalent forms of cancer in men worldwide. It remains a clinical challenge to identify lethal metastatic prostate cancers, which escape standard therapeutic intervention. Aberrant interleukin-6 (IL-6) / signal transducer and activator of transcription-3 (STAT3) signalling and loss of p53 occur during prostate cancer progression to metastatic disease. The abnormality of the IL-6/STAT3/p53 axis is frequently accompanied by other genetic alterations; however, its potential role as an important mediator of oncogenic reprogramming, invasion and metastatic transformation remains unknown. The failure of anti-IL-6 treatments is still unexplained and may be due to an incomplete understanding of the mechanism of the in vivo role of IL-6/STAT3 in prostate cancer. The identification of the alternative reading frame protein (ARF) / murine double minute protein (MDM2) / p53 tumour suppressor pathway potentially involving the IL-6/STAT3 axis as a restricting factor in prostate cancer deficient in the tumour suppressor phosphatase and tensin homologue (PTEN) opened new avenues to currently available therapies. This review summarises the current knowledge on the role of crucial pathways driving prostate cancer progression as well as metastatic disease and discusses the potential use of novel specific target molecules and how it can be exploited to avoid overtreatment and increase quality of life.

A rare castration-resistant progenitor cell population is highly enriched in Pten-null prostate tumours

Castration‐resistant prostate cancer is a lethal disease. The cell type(s) that survive androgen deprivation remain poorly described, despite global efforts to understand the various mechanisms of therapy resistance. We recently identified in wild‐type (WT) mouse prostates a rare population of luminal progenitor cells that we called LSCmed according to their FACS profile (Lin−/Sca‐1+/CD49fmed). Here, we investigated the prevalence and castration resistance of LSCmed in various mouse models of prostate tumourigenesis (Pb‐PRL, Ptenpc−/−, and Hi‐Myc mice). LSCmed prevalence is low (∼8%, similar to WT) in Hi‐Myc mice, where prostatic androgen receptor signalling is unaltered, but is significantly higher in the two other models, where androgen receptor signalling is decreased, rising up to more than 80% in Ptenpc−/− prostates. LSCmed tolerate androgen deprivation and persist or are enriched 2–3 weeks after castration. The tumour‐initiating properties of LSCmed from Ptenpc−/− mice were demonstrated by regeneration of tumours in vivo. Transcriptomic analysis revealed that LSCmed represent a unique cell entity as their gene expression profile is different from luminal and basal/stem cells, but shares markers of each. Their intrinsic androgen signalling is markedly decreased, explaining why LSCmed tolerate androgen deprivation. This also illuminates why Ptenpc−/− tumours are castration‐resistant since LSCmed represent the most prevalent cell type in this model. We validated CK4 as a specific marker for LSCmed on sorted cells and prostate tissues by immunostaining, allowing for the detection of LSCmed in various mouse prostate specimens. In castrated Ptenpc−/− prostates, there was significant proliferation of CK4+ cells, further demonstrating their key role in castration‐resistant prostate cancer progression. Taken together, this study identifies LSCmed as a probable source of prostate cancer relapse after androgen deprivation and as a new therapeutic target for the prevention of castrate‐resistant prostate cancer. Copyright

Erratum: STAT3 regulated ARF expression suppresses prostate cancer metastasis.

Nature Communications 6: Article number:7736 (2015); Published: 22 July 2015; Updated: 26 October 2015 The affiliation details for Jan Pencik are incorrect in this Article. The correct affiliation details for this author are given below: Ludwig Boltzmann Institute for Cancer Research, Waehringerstrasse 13A, 1090 Vienna, Austria.

Abstract 3138: IL-6/Stat3 signaling is an indispensable modulator of oncogene-induced cellular senescence

IL-6/Stat3 signaling plays a role as a proto-oncogene in various tumors including prostate cancer, where IL-6 has been explored as therapeutic target. Deficiency of Pten, one of the most commonly mutated genes in cancer, directly triggers a senescence program critically depending on the p19Arf-p53 fail-safe pathway. We identified a novel and unexpected tumor suppressive role of IL-6/Stat3 signaling in a Pten-deficient murine prostate cancer model. Our data provide evidence that activation of IL-6/Stat3 signaling axis is implicated in oncogene-induced senescence (OIS). Strikingly, genetic ablation of IL-6 strongly promoted prostate cancer initiation, progression and metastasis in Pten-deficient mice. Mechanistically, IL6/Stat3 signaling regulates p19Arf-p53-induced senescence by modulating expression of the ubiquitin ligase MDM2 in pre-neoplastic cells. Critically, in prostate cancer patients low expression of Stat3 or p14Arf, the human homologue of p19Arf, correlates with poor survival. Therefore, the IL-6/Stat3 signaling axis may represent a novel molecular target for senescence-based cancer therapies. Citation Format: Jan Pencik, Michaela Schlederer, Melanie Hassler, Wolfgang Gruber, Fritz Aberger, Richard Kennedy, Stephen Walker, Stephan Rose-John, Valeria Poli, Robert Eferl, Harald Esterbauer, Osman Aksoy, Merima Herac, Peter Mazal, Andrea Haitel, Martin Susani, Richard Moriggl, Zoran Culig, Lukas Kenner. IL-6/Stat3 signaling is an indispensable modulator of oncogene-induced cellular senescence. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3138. doi:10.1158/1538-7445.AM2014-3138

Abstract 61: A mouse model for small round cell tumors induced by the Ewing sarcoma oncogene EWS/FLI1

Ewing Sarcoma is a malignant bone tumor in children and young adults. Upon current multimodal therapy only ∼60% of patients are long term survivors. Due to the rarity of the disease, however, only few novel agents can be tested in clinical trials. An animal model closely recapitulating the human disease would be highly needed to more rapidly explore new therapies. Ewing sarcoma is driven by the EWS/FLI1 (EF) chimeric oncogene, an aberrant Ets transcription factor that is toxic to many cell types, but tolerated by mesenchymal stem cells (MSC). Ewing sarcoma is postulated to develop from mesenchymal progenitor cells (MPC), but transgenic approaches tolerating EF expression lack behind. EF expression was shown to induce a differentiation block in MSC but does not drive full transformation. Thus, it was hypothesized that cooperating mutations are required for sarcomagenesis. We challenged this concept in a conditional mouse model in which EWS/FLI1 is activated early during endochondral bone formation by a Prx1-driven Cre recombinase (EFPrx1). EFPrx1 mice follows Mendelian ratio, but newborns suffocated due to a malformed rib cage. Bone formation was blocked at an early chondrocytic stage. EFPrx1 mice lacked limb bones, had reduced calvaria, craniofacial abnormalities and polydactyly. We found that EF expression blocked differentiation of MSC at the pre-hypertrophic chondrocyte stage due to blocked TGF-β and enhanced Hedgehog signaling (down regulated tgfβrI/II, smad1/5, dlx5 and upregulated gli1/2 and caspase 3 mRNA expression). Moreover, EF expression blocked sox9, runx2 and osterix expression. These genes are important for bone differentian. We established MSC-like cells (MSCL) from EFPrx1 mice that self-renewed, but full transformation was absent. We ought to test if the timing of EF induction plays a role, therefor we tested many time points later that the time point described before and we found that when Prx1Cre expression and consequently EWS/FLI1 induction was delayed to a time point after birth using a tamoxifen inducible system, a significant fraction of mice developed solid tumors up to 4 months after Tamoxifen induction. The histo-pathology of the tumors resembled PAS and VIMENTIN positive small round cell tumors, and genetically an EWS/FLI1 signature was seen similar to a patient-derived Ewing sarcoma gene expression pattern. These data suggest that EWS/FLI1 can drive oncogenesis without the need for additional genetic aberrations. We propose that this transgenic mouse model could resemble a faithful model for a solid EWS/FLI1 induced tumor phenocopying human Ewing sarcoma. Citation Format: Tahereh Javaheri, Barbara Sax, Harini Nivarthi, Eleni Tomazou, Mario Mikula, Jan Pencik, Zahra Kazemi, Maximilian Kauer, Marc Wiedner, Jan Tuckermann, Michaela Schlederer, Lukas Kenner, Reinhold Erben, Malkolm Logan, Christine Hartmann, Heinrich Kovar, Richard Moriggl. A mouse model for small round cell tumors induced by the Ewing sarcoma oncogene EWS/FLI1. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 61. doi:10.1158/1538-7445.AM2014-61