Antagonistic interactions safeguard mitotic propagation of genetic and epigenetic information in zebrafish.

The stability of cellular phenotypes in developing organisms depends on error-free transmission of epigenetic and genetic information during mitosis. Methylation of cytosine residues in genomic DNA is a key epigenetic mark that modulates gene expression and prevents genome instability. Here, we report on a genetic test of the relationship between DNA replication and methylation in the context of the developing vertebrate organism instead of cell lines. Our analysis is based on the identification of hypomorphic alleles of dnmt1, encoding the DNA maintenance methylase Dnmt1, and pole1, encoding the catalytic subunit of leading-strand DNA polymerase epsilon holoenzyme (Pole). Homozygous dnmt1 mutants exhibit genome-wide DNA hypomethylation, whereas the pole1 mutation is associated with increased DNA methylation levels. In dnmt1/pole1 double-mutant zebrafish larvae, DNA methylation levels are restored to near normal values, associated with partial rescue of mutant-associated transcriptional changes and phenotypes. Hence, a balancing antagonism between DNA replication and maintenance methylation buffers against replicative errors contributing to the robustness of vertebrate development.

Initial results with [18F]FAPI-74 PET/CT in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic fibrosing interstitial lung disease with a poor prognosis. 68Ga-labeled FAP ligands exhibited highly promising results due to the crucial role of activated fibroblasts in fibrosis imaging of the lung. However, 18F-labeled FAP ligands might provide qualitatively much higher imaging results with accompanying economic benefits due to large-scale production. Thus, we sought to investigate the potential of [18F]FAPI-74 prospectively in a small patient cohort. METHODS: Eight patients underwent both [18F]FAPI-74-PET/CT and HRCT scans and were then compared with a control group without any fibrosing pulmonary disease. The tracer uptake of fibrotic lung areas was analyzed in synopsis with radiological and clinical parameters. RESULTS: We observed a positive correlation between the fibrotic active volume, the Hounsfield scale, as well as the vital and diffusing capacity of the lung. CONCLUSION: The initial results confirm our assumption that [18F]FAPI-74 offers a viable non-invasive assessment method for pulmonary fibrotic changes in patients with IPF.

Head-to-Head Intra-Individual Comparison of Biodistribution and Tumor Uptake of [18F]FAPI-74 with [18F]FDG in Patients with PDAC: A Prospective Exploratory Study.

BACKGROUND: Radiolabeled fibroblast activation protein (FAP) ligands, a novel class of tracers for PET/CT imaging, have demonstrated very promising results in various oncological, as well as in some benign, diseases with long-term potential to supplant the current pan-cancer agent [18F]FDG in some cancer types. Pancreatic ductal carcinoma (PDAC) belongs to the group of epithelial malignancies with a strong so-called "desmoplastic reaction", leading to a prominent tumor stroma with cancer-associated fibroblasts that exhibit a marked overexpression of fibroblast activation protein (FAP). The first clinical experiences in PDAC with 68Ga-labeled FAP ligands suggested superior sensitivity to [18F]FDG. However, there is limited data with 18F-labeled FAP derivatives, i.e. [18F]FAPI-74, yet prospective single- and multicenter trials are already ongoing. In this proof-of-concept study, we sought to evaluate the biodistribution, tumor uptake, and lesion detectability in patients with PDAC using [18F]FAPI-74 PET/CT as compared to [18F]FDG PET/CT scans for staging. METHODS: This study includes 7 patients (median age 69) who underwent both [18F]FDG PET/CT with contrast-enhancement and [18F]FAPI-74 PET with low-dose CT for primary staging (n = 3) and therapy response control after neoadjuvant (n = 1) or re-staging after palliative therapy (n = 3). The mean interval between PET scans was 11 ± 4 days (range 1-15 days). The [18F]FDG and [18F]FAPI-74 PET/CT scans were acquired at 64 ± 4.1 min (range 61-91 min) and 66.4 ± 6.3 min (range 60-76 min), respectively, after administration of 200 ± 94 MBq (range 79-318 MBq) and 235 ± 88 MBq (range 90-321 MBq), respectively. Quantification of tracer uptake was determined with SUVmax and SUVmean. Furthermore, the tumor-to-background ratio (TBR) was derived by dividing the SUVmax of tumor lesions by the SUVmax of adipose tissue, skeletal muscle, and blood pool. RESULTS: Overall, 32 lesions were detected in 7 patients including primary (n = 7), lung (n = 7), bone (n = 3), lymph node (n = 13), and peritoneal metastases (n = 2). [18F]FAPI-74 detected 22% more lesions compared with [18F]FDG with a better TBR and visual lesion delineation. In one patient the primary lesion could be detected unequivocally with [18F]FAPI-74 but was missed by [18F]FDG imaging. Altogether, most of the lesions demonstrated markedly elevated uptake of [18F]FAPI-74 with a simultaneous lower uptake in the background, providing a very high visual contrast. CONCLUSION: To the best of our knowledge, this is the first, prospective, intra-individual investigation comparing [18F]FAPI-74 with [18F]FDG imaging in PDAC with encouraging results. These pivotalresults supporta larger, multicentric, prospective study to determine the value of [18F]FAPI-74 in detecting and staging PDAC in comparison with current standard of care imaging.

Al[18F]F-NOTA-Octreotide Is Comparable to [68Ga]Ga-DOTA-TATE for PET/CT Imaging of Neuroendocrine Tumours in the Latin-American Population.

PET imaging of neuroendocrine tumours (NET) is well established for staging and therapy follow-up. The short half-life, increasing costs, and regulatory issues significantly limit the availability of approved imaging agents, such as [68Ga]Ga-DOTA-TATE. Al[18F]F-NOTA-Octreotide provides a similar biodistribution and tumour uptake, can be produced on a large scale and may improve access to precision imaging. Here we prospectively compared the clinical utility of [68Ga]Ga-DOTA-TATE and Al[18F]F-NOTA-Octreotide in the Latin-American population. Our results showed that in patients with stage IV NETs [68Ga]Ga-DOTA-TATE presents higher physiological uptake than Al[18F]F-NOTA-Octreotide in the liver, hypophysis, salivary glands, adrenal glands (all p < 0.001), pancreatic uncinated process, kidneys, and small intestine (all p < 0.05). Nevertheless, despite the lower background uptake of Al[18F]F-NOTA-Octreotide, comparative analysis of tumour-to-liver (TLR) and tumour-to-spleen (TSR) showed no statistically significant difference for lesions in the liver, bone, lymph nodes, and other tissues. Only three discordant lesions in highly-metastases livers were detected by [68Ga]Ga-DOTA-TATE but not by Al[18F]F-NOTA-Octreotide and only one discordant lesion was detected by Al[18F]F-NOTA-Octreotide but not by [68Ga]Ga-DOTA-TATE. Non-inferiority analysis showed that Al[18F]F-NOTA-Octreotide is comparable to [68Ga]Ga-DOTA-TATE. Hence, our results demonstrate that Al[18F]F-NOTA-Octreotide provided excellent image quality, visualized NET lesions with high sensitivity and represents a highly promising, clinical alternative to [68Ga]Ga-DOTA-TATE.

Unraveling the complex link between vitamin D levels and cancer: A crucial understanding for designing future supplementation approaches

Abstract Numerous studies have underscored the essential role of sunlight in vitamin D synthesis, while other studies have examined the association between dietary supplementation and vitamin D levels in different oncologic indications. In certain oncologic types, low levels of vitamin D correlate with a higher risk of cancer progression or poorer outcomes. On the contrary, the protective role of vitamin D remains ambiguous for some cancers. Given that the majority of cancer patients exhibit vitamin D deficiency or insufficiency, there have been suggestions to adopt supplementation strategies. However, vitamin D modulates and interacts with several molecular pathways. Therefore, it is crucial to contextualize the level and circumstances in which the action of vitamin D is observed. Distinct outcomes may emerge based on factors such as the method of assessing vitamin D levels, the size of the study populations, their genetic background, and the specific cancer type under investigation. In this article, we summarize some of the relevant studies examining the relationship between vitamin D levels and cancer. We further briefly outline the process of vitamin D synthesis and its effects on specific cellular pathways involved in cancer progression, highlighting essential considerations for future vitamin D assessments and supplementation approaches.

Imaging GRPr Expression in Metastatic Castration-Resistant Prostate Cancer with [68Ga]Ga-RM2-A Head-to-Head Pilot Comparison with [68Ga]Ga-PSMA-11.

BACKGROUND: The gastrin-releasing peptide receptor (GRPr) is highly overexpressed in several solid tumors, including treatment-naïve and recurrent prostate cancer. [68Ga]Ga-RM2 is a well-established radiotracer for PET imaging of GRPr, and [177Lu]Lu-RM2 has been proposed as a therapeutic alternative for patients with heterogeneous and/or low expression of PSMA. In this study, we aimed to evaluate the expression of GRPr and PSMA in a group of patients diagnosed with castration-resistant prostate cancer (mCRPC) by means of PET imaging. METHODS: Seventeen mCRPC patients referred for radio-ligand therapy (RLT) were enrolled and underwent [68Ga]Ga-PSMA-11 and [68Ga]Ga-RM2 PET/CT imaging, 8.8 ± 8.6 days apart, to compare the biodistribution of each tracer. Uptake in healthy organs and tumor lesions was assessed by SUV values, and tumor-to-background ratios were analyzed. RESULTS: [68Ga]Ga-PSMA-11 showed significantly higher uptake in tumor lesions in bone, lymph nodes, prostate, and soft tissues and detected 23% more lesions compared to [68Ga]Ga-RM2. In 4/17 patients (23.5%), the biodistribution of both tracers was comparable. CONCLUSIONS: Our results show that in our cohort of mCRPC patients, PSMA expression was higher compared to GRPr. Nevertheless, RLT with [177Lu]Lu-RM2 may be an alternative treatment option for selected patients or patients in earlier disease stages, such as biochemical recurrence.

Genetic landscape of T cells identifies synthetic lethality for T-ALL.

To capture the global gene network regulating the differentiation of immature T cells in an unbiased manner, large-scale forward genetic screens in zebrafish were conducted and combined with genetic interaction analysis. After ENU mutagenesis, genetic lesions associated with failure of T cell development were identified by meiotic recombination mapping, positional cloning, and whole genome sequencing. Recessive genetic variants in 33 genes were identified and confirmed as causative by additional experiments. The mutations affected T cell development but did not perturb the development of an unrelated cell type, growth hormone-expressing somatotrophs, providing an important measure of cell-type specificity of the genetic variants. The structure of the genetic network encompassing the identified components was established by a subsequent genetic interaction analysis, which identified many instances of positive (alleviating) and negative (synthetic) genetic interactions. Several examples of synthetic lethality were subsequently phenocopied using combinations of small molecule inhibitors. These drugs not only interfered with normal T cell development, but also elicited remission in a model of T cell acute lymphoblastic leukaemia. Our findings illustrate how genetic interaction data obtained in the context of entire organisms can be exploited for targeted interference with specific cell types and their malignant derivatives.

Evaluation of Safety and Dosimetry of 177Lu-DOTA-ZOL for Therapy of Bone Metastases.

Palliative treatment of bone metastasis using radiolabeled bisphosphonates is a well-known concept proven to be safe and effective. A new therapeutic radiopharmaceutical for bone metastasis is 177Lu-DOTA-zoledronic acid (177Lu-DOTA-ZOL). In this study, the safety and dosimetry of a single therapeutic dose of 177Lu-DOTA-ZOL were evaluated on the basis of a series of SPECT/CT images and blood samples. Methods: Nine patients with exclusive bone metastases from metastatic castration-resistant prostate cancer (mCRPC) (70.8 ± 8.4 y) and progression under conventional therapies participated in this prospective study. After receiving 5,780 ± 329 MBq 177Lu-DOTA-ZOL, patients underwent 3-dimensional whole-body SPECT/CT imaging and venous blood sampling over 7 d. Dosimetric evaluation was performed for main organs and tumor lesions. Safety was assessed by blood biomarkers. Results:177Lu-DOTA-ZOL showed fast uptake and high retention in bone lesions and fast clearance from the bloodstream in all patients. The average retention in tumor lesions was 0.02% injected activity per gram at 6 h after injection and approximately 0.01% at 170 h after injection. In this cohort, the average absorbed doses in bone tumor lesions, kidneys, red bone marrow, and bone surfaces were 4.21, 0.17, 0.36, and 1.19 Gy/GBq, respectively. The red marrow was found to be the dose-limiting organ for all patients. A median maximum tolerated injected activity of 6.0 GBq may exceed the defined threshold of 2 Gy for the red bone marrow in individual patients (4/8). Conclusion:177Lu-DOTA-ZOL is safe and has a favorable therapeutic index compared with other radiopharmaceuticals used in the treatment of osteoblastic bone metastases. Personalized dosimetry, however, should be considered to avoid severe hematotoxicity for individual patients.

[18F]PR04.MZ PET/CT Imaging for Evaluation of Nigrostriatal Neuron Integrity in Patients With Parkinson Disease.

INTRODUCTION: Degeneration of dopaminergic, nigrostriatal neurons is the hallmark of Parkinson disease (PD), and PET quantification of dopamine transporters is a widely accepted method for differential diagnosis between idiopathic PD and essential tremor. [18F]PR04.MZ is a new PET tracer with excellent imaging properties allowing for precise quantification of striatal and extrastriatal dopamine transporter. Here we describe our initial experience with [18F]PR04.MZ PET/CT in a larger cohort of healthy controls and PD patients as a proof-of-concept study for this tracer. METHODS: Eighteen healthy subjects, 19 early PD patients (Hoehn-Yahr I-II), and 13 moderate-advanced PD patients (Hoehn-Yahr III-IV) underwent static PET/CT scans 60 to 90 minutes after injection of 5.16 ± 1.03 mCi (191 ± 38 MBq) [18F]PR04.MZ. Specific binding ratios (SBRs) were calculated for caudate nucleus, anterior putamen, posterior putamen, substantia nigra (SNpc), compared between different groups and correlated with clinical ratings. RESULTS: [18F]PR04.MZ showed very high and specific uptake in the putamen, caudate, and substantia nigra pars compacta and very low nonspecific binding in other brain regions, and SBR values for the control group were 22.3 ± 4.1, 19.1 ± 3.5, and 5.4 ± 1.2, respectively. A reduction of SBR values was observed in all regions and in both initial and moderate PD, ranging from 35% to 89% (P < 0.001). The observed pattern of reduction was posterior putamen > anterior putamen > substantia nigra pars compacta > caudate, with contralateral posterior putamen being the most affected region. Rostrocaudal depletion gradient was evident in all PD patients and progression correlated with motor manifestations. CONCLUSIONS: [18F]PR04.MZ PET/CT is a highly sensitive imaging modality for the detection of dopaminergic deficit in nigrostriatal pathways in PD.

Biodistribution and dosimetry of a single dose of albumin-binding ligand [177Lu]Lu-PSMA-ALB-56 in patients with mCRPC.

INTRODUCTION: PSMA-targeted radionuclide therapy with lutetium-177 has emerged as an effective treatment option for metastatic, castration-resistant prostate cancer (mCRPC). Recently, the concept of modifying PSMA radioligands with an albumin-binding entity was demonstrated as a promising measure to increase the tumor uptake in preclinical experiments. The aim of this study was to translate the concept to a clinical setting and evaluate the safety and dosimetry of [177Lu]Lu-PSMA-ALB-56, a novel PSMA radioligand with albumin-binding properties. METHODS: Ten patients (71.8 ± 8.2 years) with mCRPC received an activity of 3360 ± 393 MBq (120-160 µg) [177Lu]Lu-PSMA-ALB-56 followed by whole-body SPECT/CT imaging over 7 days. Volumes of interest were defined on the SPECT/CT images for dosimetric evaluation for healthy tissue and tumor lesions. General safety and therapeutic efficacy were assessed by measuring blood biomarkers. RESULTS: [177Lu]Lu-PSMA-ALB-56 was well tolerated, and no severe adverse events were observed. SPECT images revealed longer circulation of [177Lu]Lu-PSMA-ALB-56 in the blood with the highest uptake in tumor lesions at 48 h post injection. Compared with published data for other therapeutic PSMA radioligands (e.g. PSMA-617 and PSMA I&T), normalized absorbed doses of [177Lu]Lu-PSMA-ALB-56 were up to 2.3-fold higher in tumor lesions (6.64 ± 6.92 Gy/GBq) and similar in salivary glands (0.87 ± 0.43 Gy/GBq). Doses to the kidneys and red marrow (2.54 ± 0.94 Gy/GBq and 0.29 ± 0.07 Gy/GBq, respectively) were increased. CONCLUSION: Our data demonstrated that the concept of albumin-binding PSMA-radioligands is feasible and leads to increased tumor doses. After further optimization of the ligand design, the therapeutic outcomes may be improved for patients with prostate cancer.

Diagnostic Accuracy of 18F-PSMA-1007 PET/CT Imaging for Lymph Node Staging of Prostate Carcinoma in Primary and Biochemical Recurrence.

Prostate-specific membrane antigen (PSMA)-ligand PET/CT is performed on patients with prostate cancer to stage the disease initially or to identify sites of recurrence after definitive therapy. On the basis of clinical results, 18F-PSMA-1007 is a promising PSMA PET tracer, but detailed histologic confirmation has been lacking. Methods: Ninety-six patients with prostate cancer underwent 18F-PSMA-1007 PET/CT followed by either radical prostatectomy with lymphadenectomy or salvage lymphadenectomy. The histologic findings of PSMA PET-positive nodes were analyzed retrospectively. A lesion-based and patient-based analysis was performed comparing all positive lesions and only lesions larger than 3 mm on histopathology. Results: Of the patients, 90.6% received 18F-PSMA-1007 PET/CT for staging before the primary treatment, whereas 9.4% underwent imaging for biochemical recurrence. In 34.4% of the cohort, positive lymph nodes were present on imaging. In total, 1,746 lymph nodes were dissected in 96 patients. 18F-PSMA-1007 PET had a lesion-based sensitivity of 81.7%, a specificity of 99.6%, a positive predictive value of 92.4%, and a negative predictive value of 98.9% for detecting positive lymph nodes larger than 3 mm. In the analysis of all malignant nodes regardless of size, the overall sensitivity, specificity, positive predictive value, and negative predictive value on lesion-based analysis were 71.2%, 99.5%, 91.3%, and 97.9%, respectively. The patient-based analysis showed a sensitivity of 85.9% and a specificity of 99.5% for lymph nodes larger than 3 mm. Conclusion:18F-PSMA-1007 PET/CT reliably detects malignant lymph nodes and has an exceptional specificity of more than 99% for nodal metastases.

Characterization of the serotonin 2A receptor selective PET tracer (R)-[18F]MH.MZ in the human brain.

PURPOSE: The serotonin receptor subtype 2A antagonist (5-HT2AR) (R)-[18F]MH.MZ has in preclinical studies been identified as a promising PET imaging agent for quantification of cerebral 5-HT2ARs. It displays a very similar selectivity profile as [11C]MDL 100907, one of the most selective compounds identified thus far for the 5-HT2AR. As [11C]MDL 100907, (R)-[18F]MH.MZ also displays slow brain kinetics in various animal models; however, the half-life of fluorine-18 allows for long scan times and consequently, a more precise determination of 5-HT2AR binding could still be feasible. In this study, we aimed to evaluate the potential of (R)-[18F]MH.MZ PET to image and quantify the 5-HT2AR in the human brain in vivo. METHODS: Nine healthy volunteers underwent (R)-[18F]MH.MZ PET at baseline and four out of these also received a second PET scan, after ketanserin pretreatment. Regional time-activity curves of 17 brain regions were analyzed before and after pretreatment. We also investigated radiometabolism, time-dependent stability of outcomes measures, specificity of (R)-[18F]MH.MZ 5-HT2AR binding, and performance of different kinetic modeling approaches. RESULTS: Highest uptake was determined in 5-HT2AR rich regions with a BPND of approximately 1.5 in cortex regions. No radiometabolism was observed. 1TCM and 2TCM resulted in similar outcome measure, whereas reference tissue models resulted in a small, but predictable bias. (R)-[18F]MH.MZ binding conformed to the known distribution of 5-HT2AR and could be blocked by pretreatment with ketanserin. Moreover, outcomes measures were stable after 100-110 min. CONCLUSION: (R)-[18F]MH.MZ is a suitable PET tracer to image and quantify the 5-HT2AR system in humans. In comparison with [11C]MDL 100907, faster and more precise outcome measure could be obtained using (R)-[18F]MH.MZ. We believe that (R)-[18F]MH.MZ has the potential to become the antagonist radiotracer of choice to investigate the human 5-HT2AR system.

Pharmacokinetic evaluation of [18F]PR04.MZ for PET/CT imaging and quantification of dopamine transporters in the human brain.

PURPOSE: Dopamine transporters (DAT) modulate pre-synaptic dopamine and physiological functions such as movement and reward. DAT also mirrors disease state in neurological disorders, rendering it an essential diagnostic target. [18F]PR04.MZ is a new PET imaging agent for DAT with an improved affinity and selectivity profile, for which we here describe the complete pharmacokinetic evaluation in healthy controls. METHODS: Thirty-two healthy subjects underwent T1-weighted MRI and dynamic PET scans for 180 min with arterial blood sampling (n = 5) or 90 min without blood sampling (n = 25) after injection of 197.6 ± 12.2 MBq [18F]PR04.MZ. Blood and plasma metabolite analysis were performed. MRI-based normalization of brain images, delineation of VOIs, and kinetic modeling was conducted to determine distribution volumes (Vt) and binding potentials (BPnd). The impact of scan duration was evaluated and repeated PET scans were performed to assess test-retest variability (n = 5). A static imaging protocol has been validated for clinical applications. RESULTS: [18F]PR04.MZ showed rapid metabolization in circulation, very high uptake in striatum and midbrain, and very low non-specific binding. The two-tissue compartment model 2TCM provided best fits for measured time-activity-curves and calculated Vts in putamen, caudate, substantia nigra pars compacta (SNpc), and cerebellar cortex were 11.83, 9.73, 2.12, and 0.57, respectively. All non-invasive models correlated well with BPnd values derived from 2TCM but underestimated DAT availability by about 28-33%. Of those, simplified reference tissue model (SRTM) provided the best fits, lowest Akaike Information Criteria values, and BPnd values of 14.82, 11.95, and 2.63 in putamen, caudate, and SNpc, respectively. BPnd estimates for striatal regions and SNpc were stable between 90 and 130 min post-injection. Test-retest results were excellent, showing low variability in all and excellent reliability in most relevant regions. Static imaging from 60 to 90-min post-injection is a viable alternative for quantification. CONCLUSIONS: [18F]PR04.MZ is a PET tracer with very high affinity, selectivity, and specific uptake in striatum and midbrain. 2TCM and SRTM provide good fits, high and stable Vts or BPnds, and good test-retest reliability for precise quantification of DAT in human subjects.

Oncogenic role of arsenic exposure in lung cancer: A forgotten risk factor.

Several drinkable water sources worldwide have been highly contaminated with arsenic, which means that an estimated 160 million people have been exposed to this chemical agent. If we analyse exposure by region, we will find a high correlation between arsenic contamination and the incidence of lung cancer (among other malignancies). In order to determine what the risks of these exposures are, we need to understand how this chemical is processed in our body and how it is linked to cancer. In this article we reviewed how biotransformation of ingested arsenic may lead to cancer by modulating the activation of several essential signalling pathways such as EGFR, PI3K/AKT, RTK/Ras/PI3K, JNK/STAT3 and Nrf2-KEAP1; by producing epigenetics modifications and by disrupting normal expression of miRNAs. In order to design effective health policies, educational strategies, decontaminations plans and effective medical treatments are necessary to understand the impact of arsenic pollution and the relevance of the environment in our health.

Evidence of response to pembrolizumab in a patient with Lynch syndrome-related metastatic colon cancer.

Patients with Lynch Syndrome (LS) are at high risk of developing colorectal cancer at an early age. Germline mutations in DNA mismatch repair genes and microsatellite instability are clear signatures of this autosomal dominant disorder. Here, we report the clinical history of a 38-year-old patient with LS-related metastatic colon cancer treated in Chile with immunotherapy (pembrolizumab). The patient exhibited a pathogenic deletion in Epithelial cell Adhesion Molecule (EPCAM) and mutS homolog 2 (MSH2) genes, and after diagnosis received 12 cycles of FOLFOX. The tumor mass, however, continued to grow, and a new metastatic mucinous adenocarcinoma of 13 mm appeared at the level of the 11th right dorsal vertebra. To treat these lesions, the patient received immunotherapy scheme with pembrolizumab (200 mg every 21 days). After only four cycles, the patient's symptoms improved and the lesions showed less metabolic activity. After 12 cycles with pembrolizumab, the patient started palliative radiation and systemic second-line treatment with FOLFIRI and Avastin. The immunotherapy scheme with pembrolizumab was capable of delaying the second-line treatment for at least 8 months, becoming a useful therapeutic option for this patient. Thus, our study highlights the importance of implementing immunotherapy treatment programs for LS-colorectal cancer patients in South American countries.

Forward Genetic Screens in Zebrafish Identify Pre-mRNA-Processing Pathways Regulating Early T Cell Development.

Lymphocytes represent basic components of vertebrate adaptive immune systems, suggesting the utility of non-mammalian models to define the molecular basis of their development and differentiation. Our forward genetic screens in zebrafish for recessive mutations affecting early T cell development revealed several major genetic pathways. The identification of lineage-specific transcription factors and specific components of cytokine signaling and DNA replication and/or repair pathways known from studies of immunocompromised mammals provided an evolutionary cross-validation of the screen design. Unexpectedly, however, genes encoding proteins required for pre-mRNA processing were enriched in the collection of mutants identified here. In both zebrafish and mice, deficiency of the splice regulator TNPO3 impairs intrathymic T cell differentiation, illustrating the evolutionarily conserved and cell-type-specific functions of certain pre-mRNA-processing factors for T cell development.

Stochastic Regulation of her1/7 Gene Expression Is the Source of Noise in the Zebrafish Somite Clock Counteracted by Notch Signalling.

The somite segmentation clock is a robust oscillator used to generate regularly-sized segments during early vertebrate embryogenesis. It has been proposed that the clocks of neighbouring cells are synchronised via inter-cellular Notch signalling, in order to overcome the effects of noisy gene expression. When Notch-dependent communication between cells fails, the clocks of individual cells operate erratically and lose synchrony over a period of about 5 to 8 segmentation clock cycles (2-3 hours in the zebrafish). Here, we quantitatively investigate the effects of stochasticity on cell synchrony, using mathematical modelling, to investigate the likely source of such noise. We find that variations in the transcription, translation and degradation rate of key Notch signalling regulators do not explain the in vivo kinetics of desynchronisation. Rather, the analysis predicts that clock desynchronisation, in the absence of Notch signalling, is due to the stochastic dissociation of Her1/7 repressor proteins from the oscillating her1/7 autorepressed target genes. Using in situ hybridisation to visualise sites of active her1 transcription, we measure an average delay of approximately three minutes between the times of activation of the two her1 alleles in a cell. Our model shows that such a delay is sufficient to explain the in vivo rate of clock desynchronisation in Notch pathway mutant embryos and also that Notch-mediated synchronisation is sufficient to overcome this stochastic variation. This suggests that the stochastic nature of repressor/DNA dissociation is the major source of noise in the segmentation clock.