Differentielle Expression und epigenetische Regulation des Insulinähnlichen Wachstumsfaktors 2 (IGF2) im humanen Prostatakarzinom

IGF2 wird als hauptsächlicher fetaler Wachstumsfaktor angesehen, eine Überexpression und veränderte Regulierung von IGF2, dessen Rezeptoren und Signalwege spielen in verschiedenen Krebserkrankungen und anderen Syndromen eine große Rolle. Zielgerichtete Therapien gegen dieses System wurden bereits entwickelt und in klinischen Studien auf ihre Wirkung untersucht. IGF2 ist im Gesunden streng differentiell reguliert und wird gewebe- und zeitabhängig exprimiert. Mechanismen der Regulation beinhalten epigenetische Phänomene wie Imprinting und Methylierung. Ein Verlust des Imprintings wurde in der alternden Prostata gehäuft beschrieben, die genauen Mechanismen dieses Verlusts und die Relevanz von IGF2 im Prostatakarzinom waren jedoch bisher nicht vollständig geklärt. Nach gängiger Vorstellung resultiert aus einem Verlust des Imprintings eine höhere, weil biallelische Expression. Allerdings fanden wir in den meisten untersuchten Tumorproben eine Reduktion der IGF2-Expression im Vergleich zum umliegenden Nicht-Tumorgewebe. Zudem fanden wir in Tumorgewebe im Gegensatz zu Normalgewebe keinen Zusammenhang zwischen Imprintingstatus und Genexpression. Stattdessen zeigte sich ein spezifischer Zusammenhang mit der differentiellen Aktivität der vier verschiedenen IGF2-Promotoren und deren Methylierung. So war im Normalgewebe und Tumorgewebe die Expression v.a. durch Promotor 3 und 4 gesteuert. Ein Teil der untersuchten Patienten zeigte eine in T erhöhte IGF2-Expression, was sich ebenfalls durch eine differentielle Methylierung in einem Teilbereich des Promotors 4 erklären ließ. Diese Patienten wiesen einen Trend zu jüngerem Alter zum Zeitpunkt der Prostatektomie auf. Die Kontrolle des Imprintings soll nach bisher gängigem Modell durch Methylierung einer Imprinting-Kontroll-Region erfolgen. Es konnten an dieser jedoch keine Unterschiede zwischen Proben mit Verlust des Imprintings und erhaltenem Imprinting festgestellt werden. Allerdings fanden sich bei Karzinomen mit Verlust des Imprintings häufiger Tumoreinbrüche in Lymphgefäße. Zusammenfassend zeigte die Mehrzahl der Prostatakarzinome eine verminderte IGF2-Expression, die sich durch differentielle Promotormethylierung und -aktivität erklären lässt. Die Unabhängigkeit von Imprinting und die fehlenden Methylierungsunterschiede zwischen erhaltenem und verlorenem Imprinting nähren zudem Zweifel an der Vollständigkeit und Relevanz des bisherigen Modells der IGF2-Imprintingkontrolle zumindest beim Prostatakarzinom. IGF2 und Verlust des Imprintings bieten jedoch Potential als Biomarker des Prostatakarzinoms, was in größeren Studien validiert werden sollte

A multicenter phase 4 geriatric assessment directed trial to evaluate gemcitabine +/− nab-paclitaxel in elderly pancreatic cancer patients (GrantPax)

Background: In the group of elderly patients (≥70 years) with metastatic pancreatic ductal adenocarcinoma (mPDAC), it is not known who benefits from intensive 1st line nab-paclitaxel/gemcitabine (nab-p/gem) combination chemotherapy or who would rather suffer from increased toxicity. We aim to determine whether treatment individualization by comprehensive geriatric assessments (CGAs) improves functional outcome of the patients. Methods/Design: GrantPax is a multicenter, open label phase 4 interventional trial. We use a CGA to stratify elderly patients into three parallel treatment groups (n = 45 per arm): 1) GOGO (nab-p/gem), 2) SLOWGO (gem mono) or 3) FRAIL (best supportive care). After the 1st cycle of chemotherapy (or 4 weeks in FRAIL group) another CGA and safety assessment is performed. CGA-stratified patients may not decline in their CGA performance in response to the first cycle of chemotherapy (primary objective), measured as a loss of 5 points or less in Barthels activities of daily living. Based on the second CGA, patients are re-assigned to their definite treatment arm and undergo further CGAs to monitor the course of treatment. Secondary endpoints include CGA scores during the course of therapy (CGA1–4), response rates, safety and survival rates. Discussion: GrantPax is the first trial implementing a CGA-driven treatment to personalize therapy for elderly patients with pancreatic cancer. This may lead to standardization of therapy decisions for elderly patients and may optimize standard of care for this increasing group of patients. Trial registration: NCT02812992 , registered 24.06.2016

A multicenter open-label phase II trial to evaluate nivolumab and ipilimumab for 2nd line therapy in elderly patients with advanced esophageal squamous cell cancer (RAMONA)

Background: Advanced esophageal squamous cell cancer (ESCC) is frequently diagnosed in elderly patients. The impact of 2nd line chemotherapy is poorly defined. Recent data demonstrated effectiveness of checkpoint inhibitors in different squamous cell carcinomas. Therefore, we assess combined nivolumab/ipilimumab as 2nd line therapy in elderly ESCC patients. Methods: RAMONA is a multicenter open-label phase II trial. The primary objective is to demonstrate a significant survival benefit of nivolumab/ipilimumab in advanced ESCC compared to historical data of standard chemotherapy. Primary endpoint is therefore overall survival (OS). Major secondary objective is the evaluation of tolerability. Time to QoL deterioration will thus be determined as key secondary endpoint. Further secondary endpoints are tumor response, PFS and safety. We aim to recruit a total of n = 75 subjects that have to be > 65 years old. Eligibility is determined by the geriatric status (G8 screening and Deficit Accumulation Frailty Index (DAFI)). A safety assessment will be performed after a 3 cycle run-in phase of nivolumab (240 mg Q2W) to justify escalation for eligible patients to combined nivolumab (240 mg Q2W) and ipilimumab (1 mg/kg Q6W), while the other patients will remain on nivolumab only. RAMONA also includes translational research sub-studies to identify predictive biomarkers, including PD-1 and PD-L1 evaluation at different time points, establishment of organoid cultures and microbiome analyses for response prediction. Discussion: The RAMONA trial aims to implement checkpoint inhibitors for elderly patients with advanced ESCC as second line therapy. Novel biomarkers for checkpoint-inhibitor response are analyzed in extensive translational sub-studies. Trial registration: EudraCT Number 2017–002056-86; NCT03416244, registered: 31.1.2018

Insulin‐like growth factor 2 expression in prostate cancer is regulated by promoter‐specific methylation

Deregulation of the insulin‐like growth factor (IGF) axis and dysbalance of components of the IGF system as potential therapeutic targets have been described in different tumor types. IGF2 is a major embryonic growth factor and an important activator of IGF signaling. It is regulated by imprinting in a development‐ and tissue‐dependent manner and has been implicated in a broad range of malignancies including prostate cancer (PCa). Loss of imprinting (LOI) usually results in bi‐allelic gene expression and increased levels of IGF2. However, the regulatory mechanisms and the pathophysiological impact of altered IGF2 expression in PCa remain elusive. Here, we show that in contrast to many other tumors, IGF2 mRNA and protein levels were decreased in 80% of PCa in comparison with non‐neoplastic adjacent prostate and were independent of LOI status. Instead, IGF2 expression in both tumors and adjacent prostate depended on preferential usage of the IGF2 promoters P3 and P4. Decreased IGF2 expression in tumors was strongly related to hypermethylation of these two promoters. Methylation of the A region in promoter P4 correlated specifically with IGF2 expression in the 20% of PCa where IGF2 was higher in tumors than in adjacent prostate. We conclude that IGF2 is downregulated in most PCa and may be particularly relevant during early stages of tumor development or during chemotherapy and androgen deprivation. PCa differs from other tumors in that IGF2 expression is mainly regulated through methylation of promoter‐specific and not by imprinting. Targeting of promoter‐specific regions may have relevance for the adjuvant treatment of PCa

Subcellular compartmentalization of docking protein-1 contributes to progression in colorectal cancer

Full-length (FL) docking protein-1 (DOK1) is an adapter protein which inhibits growth factor and immune response pathways in normal tissues, but is frequently lost in human cancers. Small DOK1 variants remain in cells of solid tumors and leukemias, albeit, their functions are elusive. To assess the so far unknown role of DOK1 in colorectal cancer (CRC), we generated DOK1 mutants which mimic the domain structure and subcellular distribution of DOK1 protein variants in leukemia patients. We found that cytoplasmic DOK1 activated peroxisome-proliferator-activated-receptor-gamma (PPARγ) resulting in inhibition of the c-FOS promoter and cell proliferation, whereas nuclear DOK1 was inactive. PPARγ-agonist increased expression of endogenous DOK1 and interaction with PPARγ. Forward translation of this cell-based signaling model predicted compartmentalization of DOK1 in patients. In a large series of CRC patients, loss of DOK1 protein was associated with poor prognosis at early tumor stages (*p = 0.001, n = 1492). In tumors with cytoplasmic expression of DOK1, survival was improved, whereas nuclear localization of DOK1 correlated with poor outcome, indicating that compartmentalization of DOK1 is critical for CRC progression. Thus, DOK1 was identified as a prognostic factor for non-metastatic CRC, and, via its drugability by PPARγ-agonist, may constitute a potential target for future cancer treatments

Myotubularin-related protein 7 activates peroxisome proliferator-activated receptor-gamma

Peroxisome proliferator-activated receptor-gamma (PPARγ) is a transcription factor drugable by agonists approved for treatment of type 2 diabetes, but also inhibits carcinogenesis and cell proliferation in vivo. Activating mutations in the Kirsten rat sarcoma viral oncogene homologue (KRAS) gene mitigate these beneficial effects by promoting a negative feedback-loop comprising extracellular signal-regulated kinase 1/2 (ERK1/2) and mitogen-activated kinase kinase 1/2 (MEK1/2)-dependent inactivation of PPARγ. To overcome this inhibitory mechanism, we searched for novel post-translational regulators of PPARγ. Phosphoinositide phosphatase Myotubularin-Related-Protein-7 (MTMR7) was identified as cytosolic interaction partner of PPARγ. Synthetic peptides were designed resembling the regulatory coiled-coil (CC) domain of MTMR7, and their activities studied in human cancer cell lines and C57BL6/J mice. MTMR7 formed a complex with PPARγ and increased its transcriptional activity by inhibiting ERK1/2-dependent phosphorylation of PPARγ. MTMR7-CC peptides mimicked PPARγ-activation in vitro and in vivo due to LXXLL motifs in the CC domain. Molecular dynamics simulations and docking predicted that peptides interact with the steroid receptor coactivator 1 (SRC1)-binding site of PPARγ. Thus, MTMR7 is a positive regulator of PPARγ, and its mimicry by synthetic peptides overcomes inhibitory mechanisms active in cancer cells possibly contributing to the failure of clinical studies targeting PPARγ.ISSN:2157-902