IGF-1R inhibition enhances radiosensitivity and delays double-strand break repair by both non-homologous end-joining and homologous recombination.

Inhibition of type 1 insulin-like growth factor receptor (IGF-1R) enhances tumor cell sensitivity to ionizing radiation. It is not clear how this effect is mediated, nor whether this approach can be applied effectively in the clinic. We previously showed that IGF-1R depletion delays repair of radiation-induced DNA double-strand breaks (DSBs), unlikely to be explained entirely by reduction in homologous recombination (HR) repair. The current study tested the hypothesis that IGF-1R inhibition induces a repair defect that involves non-homologous end joining (NHEJ). IGF-1R inhibitor AZ12253801 blocked cell survival and radiosensitized IGF-1R-overexpressing murine fibroblasts but not isogenic IGF-1R-null cells, supporting specificity for IGF-1R. IGF-1R inhibition enhanced radiosensitivity in DU145, PC3 and 22Rv1 prostate cancer cells, comparable to effects of Ataxia Telangiectasia Mutated inhibition. AZ12253801-treated DU145 cells showed delayed resolution of γH2AX foci, apparent within 1 h of irradiation and persisting for 24 h. In contrast, IGF-1R inhibition did not influence radiosensitivity or γH2AX focus resolution in LNCaP-LN3 cells, suggesting that radiosensitization tracks with the ability of IGF-1R to influence DSB repair. To differentiate effects on repair from growth and cell-survival responses, we tested AZ12253801 in DU145 cells at sub-SF50 concentrations that had no early (⩽48 h) effects on cell cycle distribution or apoptosis induction. Irradiated cultures contained abnormal mitoses, and after 5 days IGF-1R-inhibited cells showed enhanced radiation-induced polyploidy and nuclear fragmentation, consistent with the consequences of entry into mitosis with incompletely repaired DNA. AZ12253801 radiosensitized DNA-dependent protein kinase (DNA-PK)-proficient but not DNA-PK-deficient glioblastoma cells, and did not radiosensitize DNA-PK-inhibited DU145 cells, suggesting that in the context of DSB repair, IGF-1R functions in the same pathway as DNA-PK. Finally, IGF-1R inhibition attenuated repair by both NHEJ and HR in HEK293 reporter assays. These data indicate that IGF-1R influences DSB repair by both major DSB repair pathways, findings that may inform clinical application of this approach.

CUTL1 promotes tumor cell migration by decreasing proteasome-mediated Src degradation.

Recently, we identified the homeodomain transcription factor CUTL1 as important mediator of cell migration and tumor invasion downstream of transforming growth factor beta (TGFbeta). The molecular mechanisms and effectors mediating the pro-migratory and pro-invasive phenotype induced by CUTL1 have not been elucidated so far. Therefore, the aim of this study was to identify signaling pathways downstream of CUTL1 which are responsible for its effects on tumor cell migration. We found that the reduced motility seen after knock down of CUTL1 by RNA interference is accompanied by a delay in tumor cell spreading. This spreading defect is paralleled by a marked reduction of Src protein levels. We show that CUTL1 leads to Src protein stabilization and activation of Src-regulated downstream signaling molecules such as RhoA, Rac1, Cdc42 and ROCK. In addition, we demonstrate that CUTL1 decreases proteasome-mediated Src protein degradation, possibly via transcriptionally upregulating C-terminal Src kinase (Csk). Based on experiments using Src knockout cells (SYF), we present evidence that Src plays a crucial role in CUTL1-induced tumor cell migration. In conclusion, our findings linking the pro-invasive transcription factor CUTL1 and the Src pathway provide important new insights in the molecular effector pathways mediating CUTL-induced migration and invasion.

The effects of iron-containing superoxide dismutases on haemodynamic parameters in spontaneously hypertensive rats.

The product of FeSOD activity is hydrogen peroxide (H2O2). Furthermore, FeSOD can modify the chemical versatility of NO into its redox-active forms: nitrosonium cation (NO+) and nitroxyl anion (NO-). All of these low molecular weight species are vasoactive and, in particular, NO- induces calcitonin gene-related peptide (CGRP) synthesis (known to be the most potent relaxation-promoting peptide). In this study the effects of bolus infusions of iron-containing superoxide dismutase (FeSOD) and of superoxide dismutase containing both iron and manganese (FeMnSOD) on the arterial blood pressure (MAP), the arterial blood pressure (CO) and the total vascular resistance (TVR) in spontaneously hypertensive (SH) rats were determined. Bolus infusion of FeSOD induced a biphasic response in the MAP (an initial increase was followed by a significant decrease). At the end of the experiment the MAP returned to its basal value. FeMnSOD (the enzymatically inactive form of FeSOD) had no effect on the MAP in these experiments. Bolus infusions of FeSOD and of FeMnSOD had no effect either on the both the CO or on the TVR in SH rats. Our results indicate that arterial relaxation changes mediated by NO- may be important for regulation of blood pressure in SH rats.

[Personal experience in embolization of liver hemangiomas]. / Nase iskustvo u embolizaciji hemangioma jetre.

INTRODUCTION: Cavernous haemangioma is the most often found benign liver tumour. Its size usually does not change, although there are cases in which it grows. Large haemangiomas can cause hepatomegaly, pain in the right subcostal area, and spontaneous ruptures. By modern diagnostic procedures they are detected more often and therefore gained more diagnostic importance. Cavernous haemangiomas, especially giant ones, can be treated surgically (enucleation or resection of a part of the liver), by embolization or by other procedures. The aim of the study was to determine the important role of embolization in the treatment of symptomatic haemangiomas with risk of rupture. MATERIAL AND METHODS: Over a period of 5 years, at the Department of Gastroenterology and Hepatology, haemangioma was discovered in 35 of 178 patients with focal liver lesions. Eighteen (51%) patients were males and 17 (49%) females. In 21 (60%) patients, the size of the tumour was 2-4 cm, in 10 (29%) 5-10 cm, and in 4 more than 10 cm. Ultrasonography, computerized tomography, celiacography, scintigraphy with blood pool and ultrasound guided liver biopsy were used to diagnose haemangiomas. Polyvinyl-alcohol (Ivalon) was used for embolization. Through femoral catheter truncus coeliacus was reached, a. hepatica was catheterized, contrast was injected, and then microembolization of peripheral branches was performed. In 10 patients, because of the size of haemangioma, symptoms or localization, and a high risk of bleeding, embolization was performed. Biochumoral parameters were analyzed on the first, the second and the seventh day after the intervention. Within the period of five years, control ultrasound examinations were performed in all patients, and results were compared. In 9 patients control liver scintigraphy with blood pool was carried out. RESULTS: Embolization was performed with polyvinyl-alcohol. During angiography which followed, avascular zones were seen. There was no statistically significant difference between biochumoral parameters before and after embolization. Five years after the embolization, a reduced size of haemangioma was found in 8 patients. The echosonographic appearance of the tumour was changed in almost all patients. All clinical symptoms disappeared. There was no bleeding. In 8 of 9 patients liver scintigraphy with blood pool was performed, and there were no "warm fields." DISCUSSION: Due to modern diagnostic procedures, haemangiomas are now more often detected. However, ultrasonography is not always specific in discovering haemangiomas. Liver scintigraphy does not always reveal the typical shape of these tumours. Every procedure has its advantages and disadvantages. Once haemangioma is detected, it is the question how to treat it. Experience of most hepatologists suggests that interventions should be performed only in case of symptomatic haemangiomas, progressively growing haemangiomas, and in case of the high risk of bleeding. Embolization of the hepatic artery, previously used only as the first part of surgical procedures is now used as the only procedure in the treatment of these tumours. Some authors reported pain and fever after this intervention, which were also noticed in our patients. The reported agranulomatous arteritis with eosinophilic infiltration was not found in our patients. There were no significant changes in biochumoral analysis; this finding confirmed that there was no necrosis around embolized haemangioma. On the basis of the follow-up of our patients we came to the conclusion that embolization of haemangioma, performed by an experienced radiologist, is a very useful procedure in the therapy of symptomatic haemangiomas and haemangiomas with a high risk of bleeding.