Notch tumor suppressor function

Cancer development results from deregulated control of stem cell populations and alterations in their surrounding environment. Notch signaling is an important form of direct cell-cell communication involved in cell fate determination, stem cell potential and lineage commitment. The biological function of this pathway is critically context dependent. Here we review the pro-differentiation role and tumor suppressing function of this pathway, as revealed by loss-of-function in keratinocytes and skin, downstream of p53 and in cross-connection with other determinants of stem cell potential and/or tumor formation, such as p63 and Rho/CDC42 effectors. The possibility that Notch signaling elicits a duality of signals, involved in growth/differentiation control and cell survival will be discussed, in the context of novel approaches for cancer therapy

Embryonic vascular endothelial cells are malleable to reprogramming via Prox1 to a lymphatic gene signature.

BACKGROUND: In vivo studies demonstrate that the Prox1 transcription factor plays a critical role in the development of the early lymphatic system. Upon Prox1 expression, early lymphatic endothelial cells differentiate from the cardinal vein and begin to express lymphatic markers such as VEGFR-3, LYVE-1 and Podoplanin. Subsequent in vitro studies have found that differentiated vascular endothelial cells can be reprogrammed by Prox1 to express a lymphatic gene profile, suggesting that Prox1 can initiate the expression of a unique gene signature during lymphangiogenesis. While the in vitro data suggest that gene reprogramming occurs upon Prox1 expression, it is not clear if this is a direct result of Prox1 in vascular endothelial cells in vivo. RESULTS: Overexpression of Prox1 in vascular endothelial cells during embryonic development results in the reprogramming of genes to that of a more lymphatic signature. Consequent to this overexpression, embryos suffer from gross edema that results in embryonic lethality at E13.5. Furthermore, hemorrhaging and anemia is apparent along with clear defects in lymph sac development. Alterations in junctional proteins resulting in an increase in vascular permeability upon Prox1 overexpression may contribute to the complications found during embryonic development. CONCLUSION: We present a novel mouse model that addresses the importance of Prox1 in early embryonic lymphangiogenesis. It is clear that there needs to be a measured pattern of expression of Prox1 during embryonic development. Furthermore, Prox1 reprograms vascular endothelial cells in vivo by creating a molecular signature to that of a lymphatic endothelial cell.

Frequency and Type of Side Effects of Immunomodulating Medication in the Swiss Inflammatory Bowel Disease Cohort

Background: Medical treatment of inflammatory bowel disease (IBD) is becoming more and more complex, as several classes of immuno-modulating drugs (IMD) are often used simultaneously. Thus, the probability of adverse effects is greatly increased. Most studies reporting on adverse effects focus on single therapy, and studies providing a global survey of side effects for multiple treatments are lacking. Aim: To assess the type and frequency of adverse events in IBD patients treated with single and multiple IMD therapy. Methods: Analysis of data from the Swiss IBD Cohort Study (SIBDCS) that collects data on a large sample of IBD patients from hospitals and private practices across Switzerland. The following IMD categories were analyzed: 5-ASA, azathioprine (Aza), 6-mercaptopurine (6-MP), methotrexate (MTX), anti-TNF (infliximab, adalimumab, certolizumab-pegol), cyclosporine, tacrolimus, and steroids. The following side effects were assessed: hepatitis, pancreatitis, leucopenia, thrombopenia, nephritis, allergic reaction, pneumonitis, infections (including tuberculosis), osteoporosis, abdominal pain/diarrhea (unrelated to IBD activity), cataract, diabetes, exanthema, hirsutism, lupus-like syndrome, myalgias, depression/psychosis, tumor development. Results: A total of 1,961 patients were analyzed (977 [50%] female, mean age 42.1 ± 14.4 years): 1,119 with Crohn's disease (CD), 800 with ulcerative colitis (UC), and 42 with indeterminate colitis (IC). Three-hundred eighteen (16.2%) patients were not treated with any of the above-mentioned medications, while 650 (33.2%), 569 (29%) and 424 (21.6%) patients had one-, two-, and three- or more- IMD therapy, respectively. Of the 1,643 patients treated with IMD, 535 (32.6%) patients reported at least one side effect. We found a significant correlation between the number of drugs used by a patient and the frequency of side effects (17.4% side effects for one drug, 29% for 2 drugs, and 60.6% for three or more drugs, p < 0.001). The frequency of side effects for the different IMD classes were as follows: 5-ASA (n = 980 treated patients) 10.8%, Aza/6-MP (n = 636) 51.9% (pancreatitis in 57 = 9%, hepatitis in 17 = 2.7% of treated patients), MTX (n = 146) 42.5% (hepatitis in 4 = 2.7% of treated patients), anti-TNF (n = 255) 23.1%, cyclosporine (n = 49) 10.2%, tacrolimus (n = 5) 20%, steroids (systemic or topical, n = 1,150) 9.6%. Conclusion: IBD treatment is associated with a significant number of side effects. A direct correlation between the number of IMD used simultaneously and the frequency of side effects was observed. The results of this study indicate that treating physicians should be vigilant for the occurrence of side effects in IBD patients under single and/or multiple drug therapy.

Demographic and clinical predictors of leptomeningeal collaterals in stroke patients.

BACKGROUND: Leptomeningeal collaterals improve outcome after stroke, including reduction of hemorrhagic complications after thrombolytic or endovascular therapy, smaller infarct size, and reduction in symptoms at follow-up evaluation. The purpose of this study was to determine the demographic and clinical variables that are associated with a greater degree of cerebral collaterals. METHODS: Clinical data of patients presenting with M1 occlusions of the middle cerebral artery (MCA) and associated computed tomography angiography studies after admission from 3 separate institutions were retrospectively compiled (n = 82). Occluded hemispheres were evaluated against the intact hemisphere for degree of collateralization in the MCA territory. Regression analysis of variance was conducted between clinical variables and collateral score to determine which variables associate with greater collateral development. RESULTS: Smaller infarct size corresponded to greater collateral scores, whereas older age and statin use corresponded to lower collateral scores (P < .001). CONCLUSIONS: Cerebral collateralization is influenced by age and statin use and influences infarct size.

Diploid males support a two-step mechanism of endosymbiont-induced thelytoky in a parasitoid wasp.

BACKGROUND: Haplodiploidy, where females develop from diploid, fertilized eggs and males from haploid, unfertilized eggs, is abundant in some insect lineages. Some species in these lineages reproduce by thelytoky that is caused by infection with endosymbionts: infected females lay haploid eggs that undergo diploidization and develop into females, while males are very rare or absent. It is generally assumed that in thelytokous wasps, endosymbionts merely diploidize the unfertilized eggs, which would then trigger female development. RESULTS: We found that females in the parasitoid wasp Asobara japonica infected with thelytoky-inducing Wolbachia produce 0.7-1.2 % male offspring. Seven to 39 % of these males are diploid, indicating that diploidization and female development can be uncoupled in A. japonica. Wolbachia titer in adults was correlated with their ploidy and sex: diploids carried much higher Wolbachia titers than haploids, and diploid females carried more Wolbachia than diploid males. Data from introgression lines indicated that the development of diploid individuals into males instead of females is not caused by malfunction-mutations in the host genome but that diploid males are most likely produced when the endosymbiont fails to activate the female sex determination pathway. Our data therefore support a two-step mechanism by which endosymbionts induce thelytoky in A. japonica: diploidization of the unfertilized egg is followed by feminization, whereby each step correlates with a threshold of endosymbiont titer during wasp development. CONCLUSIONS: Our new model of endosymbiont-induced thelytoky overthrows the view that certain sex determination mechanisms constrain the evolution of endosymbiont-induced thelytoky in hymenopteran insects. Endosymbionts can cause parthenogenesis through feminization, even in groups in which endosymbiont-diploidized eggs would develop into males following the hosts' sex determination mechanism. In addition, our model broadens our understanding of the mechanisms by which endosymbionts induce thelytoky to enhance their transmission to the next generation. Importantly, it also provides a novel window to study the yet-poorly known haplodiploid sex determination mechanisms in haplodiploid insects.

Tacrolimus and cyclosporine have differential effects on the risk of development of bronchiolitis obliterans syndrome: results of a prospective, randomized international trial in lung transplantation.

BACKGROUND: Chronic lung allograft dysfunction, which manifests as bronchiolitis obliterans syndrome (BOS), is recognized as the primary cause of morbidity and mortality after lung transplantation. In this study we assessed the efficacy and safety of two de novo immunosuppression protocols to prevent BOS. METHODS: Our study approach was a multicenter, prospective, randomized (1:1) open-label superiority investigation of de novo tacrolimus vs cyclosporine, with both study arms given mycophenolate mofetil and prednisolone after lung transplantation. Cytolytic induction therapy was not employed. Patients were stratified at entry for cystic fibrosis. Primary outcome was incidence of BOS 3 years after transplant (intention-to-treat analysis). Secondary outcomes were survival and incidence of acute rejection, infection and other adverse events. RESULTS: Group demographic data were well matched: 110 of 124 tacrolimus vs 74 of 125 cyclosporine patients were treated per protocol (p < 0.01 by chi-square test). Cumulative incidence of BOS Grade ≥1 at 3 years was 11.6% (tacrolimus) vs 21.3% (cyclosporine) (cumulative incidence curves, p = 0.037 by Gray's test, pooled over strata). Univariate proportional sub-distribution hazards regression confirmed cyclosporine as a risk for BOS (HR 1.97, 95% CI 1.04 to 3.77, p = 0.039). Three-year cumulative incidence of acute rejection was 67.4% (tacrolimus) vs 74.9% (cyclosporine) (p = 0.118 by Gray's test). One- and 3-year survival rates were 84.6% and 78.7% (tacrolimus) vs 88.6% and 82.8% (cyclosporine) (p = 0.382 by log-rank test). Cumulative infection rates were similar (p = 0.91), but there was a trend toward new-onset renal failure with tacrolimus (p = 0.09). CONCLUSIONS: Compared with cyclosporine, de novo tacrolimus use was found to be associated with a significantly reduced risk for BOS Grade ≥1 at 3 years despite a similar rate of acute rejection. However, no survival advantage was detected.

Does CRP Play a Causal Role in the Development of Coronary Heart Disease: Results of a Mendelian Randomisation Experiment Involving 128,935 People

Background: C-reactive protein (CRP) is associated with risk of coronary heart disease (CHD). Whether CRP is causally associated with CHD or merely a marker of underlying atherosclerosis is uncertain. Methods: We used a Mendelian randomisation design to investigate the causal relationship of CRP with CHD. We identified three genetic variants in the CRP locus (rs7553007, rs1130864 and rs1205) which influence CRP levels. We tested the three SNPs for association with CHD amongst 28,112 CHD cases and 100,823 controls. We then compared the observed relationship between the SNPs and CHD, with that predicted from the association of SNPs with CRP levels, and of CRP levels with CHD. Results: SNPs in the CRP locus were not associated with CHD: rs7553007, OR 0.98 (95% CI, 0.94-1.01); rs1130864, OR 1.00 (95% CI, 0.86-1.15); rs1205, OR 1.03 (95% CI, 0.99-1.07); combined OR for all three SNPs, 1.00 (95% CI, 0.97-1.02), per 20% lower CRP (figure). In contrast, the predicted OR for CHD from a 20% lower CRP level is 0.94 (95% CI, 0.94- 0.95), based on meta-analysis of observational studies. Conclusions: Though CRP variants are associated with CRP levels, and CRP levels with risk of CHD, we observed that CRP variants are not associated with CHD risk. Our Mendelian randomisation experiment strongly argues against a causal association of CRP with CHD.

Aspirin and statin use and the subsequent development of depression in men and women: Results from a longitudinal population-based study.

OBJECTIVE: Low-grade chronic inflammation is one potential mechanism underlying the well-established association between major depressive disorder (MDD) and increased cardiovascular morbidity. Both aspirin and statins have anti-inflammatory properties, which may contribute to their preventive effect on cardiovascular diseases. Previous studies on the potentially preventive effect of these drugs on depression have provided inconsistent results. The aim of the present paper was to assess the prospective association between regular aspirin or statin use and the incidence of MDD. METHOD: This prospective cohort study included 1631 subjects (43.6% women, mean age 51.7 years), randomly selected from the general population of an urban area. Subjects underwent a thorough physical evaluation as well as semi-structured interviews investigating DSM-IV mental disorders at baseline and follow-up (mean duration 5.2 years). Analyses were adjusted for a wide array of potential confounders. RESULTS: Our main finding was that regular aspirin or statin use at baseline did not reduce the incidence of MDD during follow-up, regardless of sex or age (hazard ratios, aspirin: 1.19; 95%CI, 0.68-2.08; and statins: 1.25; 95%CI, 0.73-2.14; respectively). LIMITATIONS: Our study is not a randomized clinical trial and could not adjust for all potential confounding factors, information on aspirin or statin use was collected only for the 6 months prior to the evaluations, and the sample was restricted to subjects between 35 and 66 years of age. CONCLUSION: Our data do not support a large scale preventive treatment of depression using aspirin or statins in subjects aged from 35 to 66 years from the community.

Results of An International Study of Quantitative BCR/ABL Assays Using Defined RNA Samples

Molecular monitoring of BCR/ABL transcripts by real time quantitative reverse transcription PCR (qRT-PCR) is an essential technique for clinical management of patients with BCR/ABL-positive CML and ALL. Though quantitative BCR/ABL assays are performed in hundreds of laboratories worldwide, results among these laboratories cannot be reliably compared due to heterogeneity in test methods, data analysis, reporting, and lack of quantitative standards. Recent efforts towards standardization have been limited in scope. Aliquots of RNA were sent to clinical test centers worldwide in order to evaluate methods and reporting for e1a2, b2a2, and b3a2 transcript levels using their own qRT-PCR assays. Total RNA was isolated from tissue culture cells that expressed each of the different BCR/ABL transcripts. Serial log dilutions were prepared, ranging from 100 to 10-5, in RNA isolated from HL60 cells. Laboratories performed 5 independent qRT-PCR reactions for each sample type at each dilution. In addition, 15 qRT-PCR reactions of the 10-3 b3a2 RNA dilution were run to assess reproducibility within and between laboratories. Participants were asked to run the samples following their standard protocols and to report cycle threshold (Ct), quantitative values for BCR/ABL and housekeeping genes, and ratios of BCR/ABL to housekeeping genes for each sample RNA. Thirty-seven (n=37) participants have submitted qRT-PCR results for analysis (36, 37, and 34 labs generated data for b2a2, b3a2, and e1a2, respectively). The limit of detection for this study was defined as the lowest dilution that a Ct value could be detected for all 5 replicates. For b2a2, 15, 16, 4, and 1 lab(s) showed a limit of detection at the 10-5, 10-4, 10-3, and 10-2 dilutions, respectively. For b3a2, 20, 13, and 4 labs showed a limit of detection at the 10-5, 10-4, and 10-3 dilutions, respectively. For e1a2, 10, 21, 2, and 1 lab(s) showed a limit of detection at the 10-5, 10-4, 10-3, and 10-2 dilutions, respectively. Log %BCR/ABL ratio values provided a method for comparing results between the different laboratories for each BCR/ABL dilution series. Linear regression analysis revealed concordance among the majority of participant data over the 10-1 to 10-4 dilutions. The overall slope values showed comparable results among the majority of b2a2 (mean=0.939; median=0.9627; range (0.399 - 1.1872)), b3a2 (mean=0.925; median=0.922; range (0.625 - 1.140)), and e1a2 (mean=0.897; median=0.909; range (0.5174 - 1.138)) laboratory results (Fig. 1-3)). Thirty-four (n=34) out of the 37 laboratories reported Ct values for all 15 replicates and only those with a complete data set were included in the inter-lab calculations. Eleven laboratories either did not report their copy number data or used other reporting units such as nanograms or cell numbers; therefore, only 26 laboratories were included in the overall analysis of copy numbers. The median copy number was 348.4, with a range from 15.6 to 547,000 copies (approximately a 4.5 log difference); the median intra-lab %CV was 19.2% with a range from 4.2% to 82.6%. While our international performance evaluation using serially diluted RNA samples has reinforced the fact that heterogeneity exists among clinical laboratories, it has also demonstrated that performance within a laboratory is overall very consistent. Accordingly, the availability of defined BCR/ABL RNAs may facilitate the validation of all phases of quantitative BCR/ABL analysis and may be extremely useful as a tool for monitoring assay performance. Ongoing analyses of these materials, along with the development of additional control materials, may solidify consensus around their application in routine laboratory testing and possible integration in worldwide efforts to standardize quantitative BCR/ABL testing.

Role of cytokines in secondary lymphoid organ development

Summary Secondary lymphoid organs are sites of antigen presentation, clonal expansion of B and lymphocytes, and affinity maturation of B lymphocytes. In the intestine, these immune functions occur mainly in Peyer's patches (PP). PP develop through the interplay of two main cell types, haematopoietic cells and meserichyrnal cells. One particular haematopoietic cell type was identified as the inductive cell type in the formation of both PP and lymph nodes and was therefore designated as lymphoid tissue inducer cell. For a successful PP organogenesis, the crucial molecular components involved in the crosstalk of inducer cells and their mesenchymal target cells are adhesion molecules, lymphotoxin (LT) family members, and cytokines. In particular, the interleukin 7 receptor (IL-7R) expressed on inducer cells is absolutely required. To investigate the contribution of the ligand for the IL-7R. the cytokine IL-7, in the process of PP formation, we analyzed double transgenic (TG) mice. These mice resulted from an interbreeding of an IL-7TG mouse strain where the transgene is under the control of the MHC class II promoter with a second transgenic mouse strain, which overexpresses a transactivator for MHC class II genes. Double TG offsprings revealed higher levels of IL-7 mRNA occuring earlier in embryogenesis. Consequently, double TG mice showed a striking phenotype with a 3- to 5-fold increase in PP numbers compared to single IL-7TG or control littermates. Analysis of embryonic double TG intestines demonstrated that the process of PP development was already elevated during development as early as the embryonic day 16.5. Importantly, inducer cells were significantly increased in numbers in these embryonic intestines. Furthermore, the expression of LT? mRNA, which at this early time point is exclusively expressed by inducer cells, was also increased in double TG animals. These data clearly indicate a direct influence of IL-7 on the expansion of lymphoid tissue inducer cells and on the availability of LT? leading to a higher frequency of developing PP in fetal life. Interestingly, in addition to an enhanced frequency of PP development, in double TG mice, three additional phenotypic differences were observed. i) Lymphocyte infiltration in various non-lymphoid organs, such as stomach, salivary gland, and liver. Subsequent analysis demonstrated that B lymphocytes were predominant within these tertiary lymphoid structures. ii) Ectopic lymph node-like structures containing both B and T lymphocytes were found near the inguinal lymph node. iii) Double TG mice had a severe bone resorption syndrome most likely as a consequence of the pro-osteoclastic effect of IL-7. Taken together, these results show that IL-7 plays a key role in the homeostasis of inducer cells, in the generation of PP in the gut, in the formation of ectopic lymphoid tissue, and in bone resorption. Résumé Les organes lymphoïdes secondaires sont les lieux de présentation des antigènes aux lymphocytes, permettant l'expansion des lymphocytes B et T et la maturation d'affinité des lymphocytes B. Dans l'intestin, ces fonctions immunitaires se déroulent dans les plaques de Peyer (PP). Ces plaques se développent grâce à l'interaction des cellules hématopoïétiques avec des cellules mésenchymales. Un type particulier de cellules hématopoïétiques a été identifié comme cellule inductrice dans la formation des PP et des ganglions lymphatiques et de ce fait a été désigné cellule inductrice des tissus lymphoïdes. Durant l'organogénèse des PP, les composants moléculaires cruciaux impliqués dans l'interaction des cellules inductrices et des cellules mésenchymales sont les molécules d'adhésion, les membres de la famille des lymphotoxines (LT) et les cytokines. En particulier, le récepteur de l'interleukine 7 (IL-7R) exprimé par les cellules inductrices est absolument nécessaire. Pour étudier le rôle du ligand de l'IL-7R, l'interleukine IL-7, dans la formation des PP, nous avons croisé une lignée de souris transgénique (TG) surexprimant IL-7 sous contrôle du promoteur MHC class Il avec une lignée de souris transgénique surexprimant un transactivateur des genes MHC class II. Les souris doubles TG présentent une concentration élevée d'ARNm de l'IL-7 durant l'embryogénèse, ce qui résulte en une augmentation du nombre de PP de 3 à 5 fois en comparaison aux souris ayant seul le transgène IL-7 et aux souris contrôles. L'analyse des intestins des souris doubles TG démontre que le processus de développement des PP était élevé dès le jour 16.5 du développement embryonnaire. L'augmentation du nombre des cellules inductrices dans ces intestins embryonnaires est signilicative. De plus l'expression de l'ARNm LT?, qui à ce stade précoce est exclusivement exprimé dans les cellules inductrices, est également augmenté dans les doubles TG. Ces résultats indiquent clairement une influence directe d'IL-7 sur l'expansion des cellules inductrices des tissues lymphoïdes et sur la synthèse de LT? induisant une augmentation des PP se développant durant la vie foetale. En plus du développement accru des PP dans les souris doubles TG, trois différences phénotypiques ont été observées. i) L'infiltration lymphocytaire dans différents organes non-lymphoïdes, comme l'estomac, les glandes salivaires et le foie. Des analyses complémentaires ont demontré que les lymphocytes B étaient prédominants dans ces structures lymphoïdes tertiaires. ii) Des structures de ganglions lymphatiques ectopiques contenant des lymphocytes B et T ont été trouvées près des ganglions lymphatiques inguinaux. iii) Les souris doubles TG présentent un syndrome de résorption osseuse sévère probablement dû à l'effet pro-osteoclaste d'IL-7. Globalement, ces résultats montrent que IL-7 joue un rôle clé dans l'homéostasie des cellules inductrices dans la génèse de PP de l'intestin, dans la formation des tissus lymphoïdes ectopiques et dans la résorption osseuse.

Glutathione deficit during development induces anomalies in the rat anterior cingulate GABAergic neurons: Relevance to schizophrenia.

A series of studies in schizophrenic patients report a decrease of glutathione (GSH) in prefrontal cortex (PFC) and cerebrospinal fluid, a decrease in mRNA levels for two GSH synthesizing enzymes and a deficit in parvalbumin (PV) expression in a subclass of GABA neurons in PFC. GSH is an important redox regulator, and its deficit could be responsible for cortical anomalies, particularly in regions rich in dopamine innervation. We tested in an animal model if redox imbalance (GSH deficit and excess extracellular dopamine) during postnatal development would affect PV-expressing neurons. Three populations of interneurons immunolabeled for calcium-binding proteins were analyzed quantitatively in 16-day-old rat brain sections. Treated rats showed specific reduction in parvalbumin immunoreactivity in the anterior cingulate cortex, but not for calbindin and calretinin. These results provide experimental evidence for the critical role of redox regulation in cortical development and validate this animal model used in schizophrenia research.

Multi-phase post-mortem CT angiography: development of a standardized protocol.

The objective of this work was to develop an easily applicable technique and a standardized protocol for high-quality post-mortem angiography. This protocol should (1) increase the radiological interpretation by decreasing artifacts due to the perfusion and by reaching a complete filling of the vascular system and (2) ease and standardize the execution of the examination. To this aim, 45 human corpses were investigated by post-mortem computed tomography (CT) angiography using different perfusion protocols, a modified heart-lung machine and a new contrast agent mixture, specifically developed for post-mortem investigations. The quality of the CT angiographies was evaluated radiologically by observing the filling of the vascular system and assessing the interpretability of the resulting images and by comparing radiological diagnoses to conventional autopsy conclusions. Post-mortem angiography yielded satisfactory results provided that the volumes of the injected contrast agent mixture were high enough to completely fill the vascular system. In order to avoid artifacts due to the post-mortem perfusion, a minimum of three angiographic phases and one native scan had to be performed. These findings were taken into account to develop a protocol for quality post-mortem CT angiography that minimizes the risk of radiological misinterpretation. The proposed protocol is easy applicable in a standardized way and yields high-quality radiologically interpretable visualization of the vascular system in post-mortem investigations.

Development of CBCT-based prostate setup correction strategies and impact of rectal distension.

BACKGROUND: Cone-beam computed tomography (CBCT) image-guided radiotherapy (IGRT) systems are widely used tools to verify and correct the target position before each fraction, allowing to maximize treatment accuracy and precision. In this study, we evaluate automatic three-dimensional intensity-based rigid registration (RR) methods for prostate setup correction using CBCT scans and study the impact of rectal distension on registration quality. METHODS: We retrospectively analyzed 115 CBCT scans of 10 prostate patients. CT-to-CBCT registration was performed using (a) global RR, (b) bony RR, or (c) bony RR refined by a local prostate RR using the CT clinical target volume (CTV) expanded with 1-to-20-mm varying margins. After propagation of the manual CT contours, automatic CBCT contours were generated. For evaluation, a radiation oncologist manually delineated the CTV on the CBCT scans. The propagated and manual CBCT contours were compared using the Dice similarity and a measure based on the bidirectional local distance (BLD). We also conducted a blind visual assessment of the quality of the propagated segmentations. Moreover, we automatically quantified rectal distension between the CT and CBCT scans without using the manual CBCT contours and we investigated its correlation with the registration failures. To improve the registration quality, the air in the rectum was replaced with soft tissue using a filter. The results with and without filtering were compared. RESULTS: The statistical analysis of the Dice coefficients and the BLD values resulted in highly significant differences (p<10(-6)) for the 5-mm and 8-mm local RRs vs the global, bony and 1-mm local RRs. The 8-mm local RR provided the best compromise between accuracy and robustness (Dice median of 0.814 and 97% of success with filtering the air in the rectum). We observed that all failures were due to high rectal distension. Moreover, the visual assessment confirmed the superiority of the 8-mm local RR over the bony RR. CONCLUSION: The most successful CT-to-CBCT RR method proved to be the 8-mm local RR. We have shown the correlation between its registration failures and rectal distension. Furthermore, we have provided a simple (easily applicable in routine) and automatic method to quantify rectal distension and to predict registration failure using only the manual CT contours.