The role of galectin-1 in the modulation of radioresistance as a function of Trk receptor expression in neuroblastoma

Das Neuroblastom ist der häufigste extrakranielle solide Tumor im Kindesalter, welcher sich insbesondere durch eine starke Heterogenität in der Ausprägung und im Verlauf der Erkrankung auszeichnet. Die aggressivste Form des Neuroblastoms ist durch eine MYCN-Amplifikation und eine hohe Expression der Rezeptor-Tyrosin-KinaseTrkB und dessen Zielgen Gal-1 charakterisiert. Gal-1, welches auch in anderen Tumorentitäten hochreguliert ist, ist ein multifunktionales Protein und spielt vor allem in der Zell-Zell- sowie Zell-Matrix-Kommunikation eine Rolle. Des Weiteren wird Gal-1 Einfluss auf das Immunsystem, die Angiogenese und die Strahlenantwort zugeschrieben. Wir konnten zeigen, dass die humanen Neuroblastomzellen Kelly und SY5Y mit einer erhöhten Expression von Gal-1 auf ionisierende Strahlen reagieren. Ein shRNA vermittelter knock-down von Gal-1 hat einen negativen Einfluss auf die Zellviabilität und das Kurzzeitüberleben in murinen NHO2A-Zellen, nicht jedoch auf das Langzeitüberleben, im Koloniebildungstest nach Bestrahlung. Daher können parakrine statt autokrine Effekte von Gal-1 auf die Strahlenantwort postuliert werden. Um das Tumormikroumfeld miteinzubeziehen, wurden Gal-1 abhängige Bestrahlungseffekte beim CAM (Chorion-Allantois-Membran)-Assay und im TH-MYCN Mausmodell für das Neuroblastom untersucht. Im CAM-Assay konnten keine Unterschiede in der Proliferation nach Bestrahlung in Abhängigkeit der Gal-1 Expression festgestellt werden. Eine Behandlung tumortragender TH-MYCN Tiere mit OTX008, einem Gal-1 Inhibitor, zeigte eine Reduktion des Endothelzellmarkers CD31+, welche bereits bei doppel-transgenen TH-MYCN Tieren mit Gal-1 knock-out beschrieben wurde. Die lokale Bestrahlung tumortragender TH-MYCN x Gal-1 Tiere zeigte in ersten Versuchen ein geringeres Tumorgewicht nach Bestrahlung von Tieren mit mindestens einer Gen-Kopie von Gal-1. Passend dazu wurde bei Tumoren von Gal-1 knock-out nach Bestrahlung eine reduzierte Infiltration von CD45+ Leukozyten und eine erhöhte Infiltration von CD11c+ dendritischen Zellen im Tumor gemessen, sodass wir die bereits beschriebene Rolle von Gal-1 bei der Immunantwort bestätigen konnten. Wir vermuten demnach, dass die verminderte Angiogenese in Gal-1 knock-out Tieren zu einer geringeren Infiltration von Leukozyten führt, was wiederum einen negativen Einfluss auf den Erfolg einer Bestrahlungstherapie hat. Diese Ergebnisse liefern wichtige Erkenntnisse für die Optimierung einer kombinierten Behandlung aus Bestrahlung und Gal-1 Inhibition in der Tumortherapie über das Neuroblastom hinaus.Neuroblastoma (NB) is the most common extracranial solid tumour of childhood, which shows remarkable heterogeneity with respect to outcome and progression. The most aggressive subgroup of NB is characterised by an amplification of the MYCN oncogene as well as by high expression of the receptor tyrosine kinase TrkB and its target Gal-1. Gal-1, which is also upregulated in other tumour entities, is a multifunctional protein, which plays a role in cell-cell and cell-matrix communication. Furthermore, it has been shown that Gal-1 has a direct impact on the immune system, tumour angiogenesis and on the radiation response. We could show that human neuroblastoma cell lines, Kelly and SY5Y, respond to ionizing radiation with an increased expression of Gal-1. An shRNA mediated knock-down of Gal-1 reduces cell viability and short term survival in murine NHO2A cells. However, long term survival assessed by colony formation assay was unaffected by Gal-1 expression levels. Based on that, we postulated a paracrine rather than an autocrine effect of Gal-1 on the radiation response. To therefore evaluate a Gal-1 dependent modulation of the radiation response in vivo, we took advantage of the established TH-MYCN mouse model of NB. Here, treatment of tumour bearing mice with a Gal-1 specific inhibitor, OTX008, reduced tumour angiogenesis as deduced from staining for the endothelial cell marker, CD31+. This was in line with results obtained from genetic depletion of Gal-1 in TH-MYCN x Gal-1-/- mice. Local irradiation of abdominal tumours in TH-MYCN revealed reduced of tumour burden after irradiation in the presence of at least one copy of the Gal-1 gene. In the same setting, Gal-1 knock-out resulted in a reduced infiltration of CD45+ leukocytes and an increased infiltration of CD11c+ dendritic cells, in line with our previous findings. We postulate that reduced angiogenesis in Gal-1 knock-out animals is concomitant with impaired leukocyte infiltration of tumours. This in turn might explain reduced effectivity of radiotherapy in the absence of Gal-1. Further experiments are needed to identify the optimal combination of Gal-1 inhibition and radiotherapy in NB and other tumours

TrkB-target Galectin-1 impairs immune activation and radiation responses in neuroblastoma: implications for tumour therapy

Galectin-1 (Gal-1) has been described to promote tumour growth by inducing angiogenesis and to contribute to the tumour immune escape. We had previously identified up-regulation of Gal-1 in preclinical models of aggressive neuroblastoma (NB), the most common extracranial tumour of childhood. While Gal-1 did not confer a survival advantage in the absence of exogenous stressors, Gal-1 contributed to enhanced cell migratory and invasive properties. Here, we review these findings and extend them by analyzing Gal-1 mediated effects on immune cell regulation and radiation resistance. In line with previous results, cell autonomous effects as well as paracrine functions contribute to Gal-1 mediated pro-tumourigenic functions. Interfering with Gal-1 functions in vivo will add to a better understanding of the role of the Gal-1 axis in the complex tumour-host interaction during immune-, chemo- and radiotherapy of neuroblastoma

TrkB-Target Galectin-1 Impairs Immune Activation and Radiation Responses in Neuroblastoma: Implications for Tumour Therapy

Galectin-1 (Gal-1) has been described to promote tumour growth by inducing angiogenesis and to contribute to the tumour immune escape. We had previously identified up-regulation of Gal-1 in preclinical models of aggressive neuroblastoma (NB), the most common extracranial tumour of childhood. While Gal-1 did not confer a survival advantage in the absence of exogenous stressors, Gal-1 contributed to enhanced cell migratory and invasive properties. Here, we review these findings and extend them by analyzing Gal-1 mediated effects on immune cell regulation and radiation resistance. In line with previous results, cell autonomous effects as well as paracrine functions contribute to Gal-1 mediated pro-tumourigenic functions. Interfering with Gal-1 functions in vivo will add to a better understanding of the role of the Gal-1 axis in the complex tumour-host interaction during immune-, chemo- and radiotherapy of neuroblastoma

The GSK461364 PLK1 inhibitor exhibits strong antitumoral activity in preclinical neuroblastoma models

Polo-like kinase 1 (PLK1) is a serine/threonine kinase that promotes G2/M-phase transition, is expressed in elevated levels in high-risk neuroblastomas and correlates with unfavorable patient outcome. Recently, we and others have presented PLK1 as a potential drug target for neuroblastoma, and reported that the BI2536 PLK1 inhibitor showed antitumoral actvity in preclinical neuroblastoma models. Here we analyzed the effects of GSK461364, a competitive inhibitor for ATP binding to PLK1, on typical tumorigenic properties of preclinical in vitro and in vivo neuroblastoma models. GSK461364 treatment of neuroblastoma cell lines reduced cell viability and proliferative capacity, caused cell cycle arrest and massively induced apoptosis. These phenotypic consequences were induced by treatment in the low-dose nanomolar range, and were independent of MYCN copy number status. GSK461364 treatment strongly delayed established xenograft tumor growth in nude mice, and significantly increased survival time in the treatment group. These preclinical findings indicate PLK1 inhibitors may be effective for patients with high-risk or relapsed neuroblastomas with upregulated PLK1 and might be considered for entry into early phase clinical trials in pediatric patients