Expansion of Typical Values for Paediatric Patients in Ireland and Comparison with Published DRLs - Experiences of a Single Institution.

INTRODUCTION: To reduce the risks involved with ionising radiation exposure, typical values (TVs) and diagnostic reference levels (DRLs) have been established to help keep radiation doses 'as low as reasonably practicable. TVs/DRLs provide standardised radiation dose metrics that can be used for comparative purposes. However, for paediatrics, such values should consider the size of the child instead of their age. This study aimed to establish and compare paediatric TVs for chest, abdomen and pelvis radiography. METHODS: Study methods followed processes for establishing paediatric DRLs as outlined by the Health Information and Quality Authority (HIQA). Kerma-area product (KAP) values, excluding rejected images, were retrospectively acquired from the study institution's Picture Archiving and Communications System (PACS). Paediatric patients were categorised into the following weight-based groupings (5 to <15 kg, 15 to <30 kg, 30 to <50 kg, 50 to 80 kg) and stratified based on the examination that was performed (chest, abdomen, and pelvis), and where it was performed (the different X-ray rooms). Anonymised data were inputted into Microsoft Excel for analysis. Median and 3rd quartile KAP values were reported together with graphical illustrations. RESULTS: Data from 407 X-ray examinations were analysed. For the previously identified weight categories (5 to <15 kg, 15 to <30 kg, 30 to <50 kg, 50 to 80 kg), TVs for the chest were 0.10, 0.19, 0.37 and 0.53 dGy.cm2, respectively. For the abdomen 0.39, 1.04, 3.51 and 4.05 dGy.cm2 and for the pelvis 0.43, 0.87, 3.50 and 7.58 dGy.cm2. Between X-ray rooms TVs varied against the institutional TVs by -60 to 119 % (chest), -50 to 103 % (abdomen) and -14 and 24 %% (pelvis). CONCLUSION: TVs in this study follow established trends with patient weight and examination type and are comparable with published literature. Variations do exist between individual examination rooms and reasons are multifactorial. Given that age and size do not perfectly correlate further work should be undertaken around weight-based TVs/DRLs in the paediatric setting.

Association between psoas major muscle mass and CPET performance and long-term survival following major colorectal surgery: A retrospective cohort study.

OBJECTIVES: To evaluate whether computed tomography (CT)-derived psoas major muscle measurements could predict preoperative cardiopulmonary exercise testing (CPET) performance and long-term mortality in patients undergoing major colorectal surgery and to compare predictive performance of psoas muscle measurements using 2D approach and 3D approach. METHODS: A retrospective cohort study compliant with STROCSS standards was conducted. Consecutive patients undergoing major colorectal surgery between January 2011 and January 2017 following CPET as part of their preoperative assessment were included. Regression analyses were modelled to investigate association between the CT-derived psoas major muscle mass variables [total psoas muscle area (TPMA), total psoas muscle volume (TPMV) and psoas muscle index (PMI)] and CPET performance and mortality (1-year and 5-year). Discriminative performances of the variables were evaluated using Receiver Operating Characteristic (ROC) curve analysis. RESULTS: A total of 457 eligible patients were included. The median TPMA and TPMV were 21 â€‹cm2 (IQR: 15-27) and 274 â€‹cm3 (IQR: 201-362), respectively. The median PMI measured via 2D and 3D approaches were 7 â€‹cm2/m2 (IQR: 6-9) and 99 â€‹cm3/m2 (IQR: 76-120), respectively. The risks of 1-year and 5-year mortality were 7.4% and 27.1%, respectively. Regression analyses showed TPMA, TPMV, and PMI can predict preoperative CPET performance and long-term mortality. However, ROC curve analyses showed no significant difference in predictive performance amongst TPMA, TPMV, and PMI. CONCLUSION: Radiologically-measured psoas muscle mass variables may predict preoperative CPET performance and may be helpful with informing more objective selection of patients for preoperative CPET and prehabilitation.

Symmetry-breaking malachite green as a near-infrared light-activated fluorogenic photosensitizer for RNA proximity labeling.

Cellular RNA is asymmetrically distributed in cells and the regulation of RNA localization is crucial for proper cellular functions. However, limited chemical tools are available to capture dynamic RNA localization in complex biological systems with high spatiotemporal resolution. Here, we developed a new method for RNA proximity labeling activated by near-infrared (NIR) light, which holds the potential for deep penetration. Our method, termed FAP-seq, utilizes a genetically encoded fluorogen activating protein (FAP) that selectively binds to a set of substrates known as malachite green (MG). FAP binding restricts the rotation of MG and rapidly activates its fluorescence in a wash-free manner. By introducing a monoiodo modification to MG, we created a photosensitizer (MG-HI) with the highest singlet oxygen generation ability among various MG derivatives, enabling both protein and RNA proximity labeling in live cells. New insights are provided in the transcriptome analysis with FAP-seq, while a deeper understanding of the symmetry-breaking structural arrangement of FAP-MG-HI was obtained through molecular dynamics simulations. Overall, our wash-free and NIR light-inducible RNA proximity labeling method (FAP-seq) offers a powerful and versatile approach for investigating complex mechanisms underlying RNA-related biological processes.

Comparison of distortion correction preprocessing pipelines for DTI in the upper limb.

PURPOSE: DTI characterizes tissue microstructure and provides proxy measures of nerve health. Echo-planar imaging is a popular method of acquiring DTI but is susceptible to various artifacts (e.g., susceptibility, motion, and eddy currents), which may be ameliorated via preprocessing. There are many pipelines available but limited data comparing their performance, which provides the rationale for this study. METHODS: DTI was acquired from the upper limb of heathy volunteers at 3T in blip-up and blip-down directions. Data were independently corrected using (i) FSL's TOPUP & eddy, (ii) FSL's TOPUP, (iii) DSI Studio, and (iv) TORTOISE. DTI metrics were extracted from the median, radial, and ulnar nerves and compared (between pipelines) using mixed-effects linear regression. The geometric similarity of corrected b = 0 images and the slice matched T1-weighted (T1w) images were computed using the Sörenson-Dice coefficient. RESULTS: Without preprocessing, the similarity coefficient of the blip-up and blip-down datasets to the T1w was 0·80 and 0·79, respectively. Preprocessing improved the geometric similarity by 1% with no difference between pipelines. Compared to TOPUP & eddy, DSI Studio and TORTOISE generated 2% and 6% lower estimates of fractional anisotropy, and 6% and 13% higher estimates of radial diffusivity, respectively. Estimates of anisotropy from TOPUP & eddy versus TOPUP were not different but TOPUP reduced radial diffusivity by 3%. The agreement of DTI metrics between pipelines was poor. CONCLUSIONS: Preprocessing DTI from the upper limb improves geometric similarity but the choice of the pipeline introduces clinically important variability in diffusion parameter estimates from peripheral nerves.

Responsible AI practice and AI education are central to AI implementation: a rapid review for all medical imaging professionals in Europe.

Artificial intelligence (AI) has transitioned from the lab to the bedside, and it is increasingly being used in healthcare. Radiology and Radiography are on the frontline of AI implementation, because of the use of big data for medical imaging and diagnosis for different patient groups. Safe and effective AI implementation requires that responsible and ethical practices are upheld by all key stakeholders, that there is harmonious collaboration between different professional groups, and customised educational provisions for all involved. This paper outlines key principles of ethical and responsible AI, highlights recent educational initiatives for clinical practitioners and discusses the synergies between all medical imaging professionals as they prepare for the digital future in Europe. Responsible and ethical AI is vital to enhance a culture of safety and trust for healthcare professionals and patients alike. Educational and training provisions for medical imaging professionals on AI is central to the understanding of basic AI principles and applications and there are many offerings currently in Europe. Education can facilitate the transparency of AI tools, but more formalised, university-led training is needed to ensure the academic scrutiny, appropriate pedagogy, multidisciplinarity and customisation to the learners' unique needs are being adhered to. As radiographers and radiologists work together and with other professionals to understand and harness the benefits of AI in medical imaging, it becomes clear that they are faced with the same challenges and that they have the same needs. The digital future belongs to multidisciplinary teams that work seamlessly together, learn together, manage risk collectively and collaborate for the benefit of the patients they serve.

Current abdominal X-rays practice in accident and emergency.

INTRODUCTION: Previous literature reviews revealed that abdominal X-rays (AXR) performed for the accident and emergency department (A&E), had low sensitivity, high further imaging and non-alignment rate to the Royal College of Radiologists (RCR) guidelines. A study was performed to investigate the current practice with the aim of making recommendations to improve practice, which can reduce patients' radiation exposures, while can re-routing resources to other priorities. METHODS: A study was performed in one of the UK's largest A&Es, in accordance with the RCR guidelines. All the AXR requests from A&E, regardless of the patient's age, within a 28-day period, were retrospectively assessed. Non-A&E patients and abandoned examinations due to uncooperative patients were excluded. The total number of AXR requests received by the A&E imaging department was 169, with 28/169 falling into the exclusion criteria. RESULTS: Of the 141 included requests, five unjustified requests were correctly rejected. The remaining 136 requests were accepted and performed, though only 115/136 (84.6%) of these were justified. The most common justified and unjustified indications were obstruction and renal stones, respectively. Only 4% of reported AXR had pathological abnormalities, while 45/136 patients had further imaging. CONCLUSIONS: The small proportion of significant findings echoed previous studies, suggesting an AXR overuse. Over 80% of non-compliant requests were performed, and awareness of the justification guidelines can be increased by clinical governance, posters, or an algorithm previously presented. The 32.4% further imaging rate recorded in this study, as opposed to the 73.7% reported in previous literature, merits attention. IMPLICATIONS TO PRACTICE: Stopping the overuse of AXR can minimise the radiation dose received and relieve the mounting pressure in imaging and reporting, which can serve other patients who would benefit from the services otherwise.

The application of Aptamer in biomarker discovery.

Biomarkers are detectable molecules that can reflect specific physiological states of cells, organs, and organisms and therefore be regarded as indicators for specific diseases. And the discovery of biomarkers plays an essential role in cancer management from the initial diagnosis to the final treatment regime. Practically, reliable clinical biomarkers are still limited, restricted by the suboptimal methods in biomarker discovery. Nucleic acid aptamers nowadays could be used as a powerful tool in the discovery of protein biomarkers. Nucleic acid aptamers are single-strand oligonucleotides that can specifically bind to various targets with high affinity. As artificial ssDNA or RNA, aptamers possess unique advantages compared to conventional antibodies. They can be flexible in design, low immunogenicity, relative chemical/thermos stability, as well as modifying convenience. Several SELEX (Systematic Evolution of Ligands by Exponential Enrichment) based methods have been generated recently to construct aptamers for discovering new biomarkers in different cell locations. Secretome SELEX-based aptamers selection can facilitate the identification of secreted protein biomarkers. The aptamers developed by cell-SELEX can be used to unveil those biomarkers presented on the cell surface. The aptamers from tissue-SELEX could target intracellular biomarkers. And as a multiplexed protein biomarker detection technology, aptamer-based SOMAScan can analyze thousands of proteins in a single run. In this review, we will introduce the principle and workflow of variations of SELEX-based methods, including secretome SELEX, ADAPT, Cell-SELEX and tissue SELEX. Another powerful proteome analyzing tool, SOMAScan, will also be covered. In the second half of this review, how these methods accelerate biomarker discovery in various diseases, including cardiovascular diseases, cancer and neurodegenerative diseases, will be discussed.

Efficacy of Artificial Intelligence in the Categorisation of Paediatric Pneumonia on Chest Radiographs: A Systematic Review.

This study aimed to systematically review the literature to synthesise and summarise the evidence surrounding the efficacy of artificial intelligence (AI) in classifying paediatric pneumonia on chest radiographs (CXRs). Following the initial search of studies that matched the pre-set criteria, their data were extracted using a data extraction tool, and the included studies were assessed via critical appraisal tools and risk of bias. Results were accumulated, and outcome measures analysed included sensitivity, specificity, accuracy, and area under the curve (AUC). Five studies met the inclusion criteria. The highest sensitivity was by an ensemble AI algorithm (96.3%). DenseNet201 obtained the highest level of specificity and accuracy (94%, 95%). The most outstanding AUC value was achieved by the VGG16 algorithm (96.2%). Some of the AI models achieved close to 100% diagnostic accuracy. To assess the efficacy of AI in a clinical setting, these AI models should be compared to that of radiologists. The included and evaluated AI algorithms showed promising results. These algorithms can potentially ease and speed up diagnosis once the studies are replicated and their performances are assessed in clinical settings, potentially saving millions of lives.

Mussel-inspired monomer - A new selective protease inhibitor against dentine collagen degradation.

OBJECTIVES: To evaluate the inhibitory effect of a novel mussel-inspired monomer (N-(3,4-dihydroxyphenethyl)methacrylamide (DMA) on the soluble and matrix-bound proteases. METHODS: The inhibitory effect of DMA (0, 1, 5, and 10 mM) and 1 mM chlorhexidine (CHX) dissolved in 50% ethanol/water on soluble recombinant human matrix metalloproteinases (rhMMP-2, -8, and -9), as well as cysteine cathepsins (B and K) were evaluated using both fluorometric assay kits and molecular docking. The effect of CHX and DMA on matrix-bound proteases was examined by in situ zymography, and the fluorescence intensity and relative area were calculated by Image J software. All data obtained were analyzed by one-way ANOVA followed by Tukey test (α = 0.05). RESULTS: The anti-proteolytic ability of DMA increased in a dose-dependent manner except that of rhMMP-9. Inhibitory effect of 1 mM DMA against rhMMP-2, - 8, - 9, as well as cathepsin B and K was all significantly lower than 1 mM CHX (p < 0.05). The molecular docking analysis was in good agreement with the experimental results, that the binding energy of DMA was lower than CHX for all proteases. In situ zymography revealed that all DMA- and CHX-treated groups significantly inactivated the matrix-bound proteases, with a dramatic reduction of the fluorescence intensity and relative area compared with the control group (p < 0.05). SIGNIFICANCE: Under the prerequisite condition that the overall inhibitory performance on matrix-bound proteases was comparable by DMA and CHX, the more selective property of DMA could avoid inducing potential negative effects by suppressing MMP-9 when applied in dental treatment compared with CHX.

Inhibition of FAK kinase activity preferentially targets cancer stem cells.

Because cancer stem cells (CSCs) have been implicated in chemo-resistance, metastasis and tumor recurrence, therapeutic targeting of CSCs holds promise to address these clinical challenges to cancer treatment. VS-4718 and VS-6063 are potent inhibitors of focal adhesion kinase (FAK), a non-receptor tyrosine kinase that mediates cell signals transmitted by integrins and growth factor receptors. We report here that inhibition of FAK kinase activity by VS-4718 or VS-6063 preferentially targets CSCs, as demonstrated by a panel of orthogonal CSC assays in cell line models and surgically resected primary breast tumor specimens cultured ex vivo. Oral administration of VS-4718 or VS-6063 to mice bearing xenograft models of triple-negative breast cancer (TNBC) significantly reduced the proportion of CSCs in the tumors, as evidenced by a reduced tumor-initiating capability upon re-implantation in limiting dilutions of cells prepared from these tumors. In contrast, the cytotoxic chemotherapeutic agents, paclitaxel and carboplatin, enriched for CSCs, consistent with previous reports that these cytotoxic agents preferentially target non-CSCs. Importantly, VS-4718 and VS-6063 attenuated the chemotherapy-induced enrichment of CSCs in vitro and delayed tumor regrowth following cessation of chemotherapy. An intriguing crosstalk between FAK and the Wnt/ß-catenin pathway was revealed wherein FAK inhibition blocks ß-catenin activation by reducing tyrosine 654 phosphorylation of ß-catenin. Furthermore, a constitutively active mutant form of ß-catenin reversed the preferential targeting of CSCs by FAK inhibition, suggesting that this targeting is mediated, at least in part, through attenuating ß-catenin activation. The preferential targeting of cancer stem cells by FAK inhibitors provides a rationale for the clinical development of FAK inhibitors aimed to increase durable responses for cancer patients.

Pyk2 promotes tumor progression in multiple myeloma.

Proline-rich tyrosine kinase 2 (Pyk2) is a member of the focal adhesion kinase family that has been recently linked to tumor development. However, its role in modulating multiple myeloma (MM) biology and disease progression remains unexplored. We first demonstrated that patients with MM present with higher expression of Pyk2 compared with healthy individuals. By using loss-of-function approaches, we found that Pyk2 inhibition led to reduction of MM tumor growth in vivo as well as decreased cell proliferation, cell-cycle progression, and adhesion ability in vitro. In turn, overexpression of Pyk2 promoted the malignant phenotype, substantiated by enhanced tumor growth and reduced survival. Mechanistically, inhibition of Pyk2 reduced activation of Wnt/ß-catenin signaling by destabilizing ß-catenin, leading to downregulation of c-Myc and Cyclin D1. Furthermore, treatment of MM cells with the FAK/Pyk2 inhibitor VS-4718 effectively inhibited MM cell growth both in vitro and in vivo. Collectively, our findings describe the tumor-promoting role of Pyk2 in MM, thus providing molecular evidence for a novel tyrosine kinase inhibitor as a new therapeutic option in MM.

STAT5 is crucial to maintain leukemic stem cells in acute myelogenous leukemias induced by MOZ-TIF2.

MOZ-TIF2 is a leukemogenic fusion oncoprotein that confers self-renewal capability to hematopoietic progenitor cells and induces acute myelogenous leukemia (AML) with long latency in bone marrow transplantation assays. Here, we report that FLT3-ITD transforms hematopoietic cells in cooperation with MOZ-TIF2 in vitro and in vivo. Coexpression of FLT3-ITD confers growth factor independent survival/proliferation, shortens disease latency, and results in an increase in the number of leukemic stem cells (LSC). We show that STAT5, a major effector of aberrant FLT3-ITD signal transduction, is both necessary and sufficient for this cooperative effect. In addition, STAT5 signaling is essential for MOZ-TIF2-induced leukemic transformation itself. Lack of STAT5 in fetal liver cells caused rapid differentiation and loss of replating capacity of MOZ-TIF2-transduced cells enriched for LSCs. Furthermore, mice serially transplanted with Stat5(-/-) MOZ-TIF2 leukemic cells develop AML with longer disease latency and finally incomplete penetrance when compared with mice transplanted with Stat5(+/+) MOZ-TIF2 leukemic cells. These data suggest that STAT5AB is required for the self-renewal of LSCs and represents a combined signaling node of FLT3-ITD and MOZ-TIF2 driven leukemogenesis. Therefore, targeting aberrantly activated STAT5 or rewired downstream signaling pathways may be a promising therapeutic option.

Adenosine A2A and beta-2 adrenergic receptor agonists: novel selective and synergistic multiple myeloma targets discovered through systematic combination screening.

The use of combination drug regimens has dramatically improved the clinical outcome for patients with multiple myeloma. However, to date, combination treatments have been limited to approved drugs and a small number of emerging agents. Using a systematic approach to identify synergistic drug combinations, combination high-throughput screening (cHTS) technology, adenosine A2A and ß-2 adrenergic receptor (ß2AR) agonists were shown to be highly synergistic, selective, and novel agents that enhance glucocorticoid activity in B-cell malignancies. Unexpectedly, A2A and ß2AR agonists also synergize with melphalan, lenalidomide, bortezomib, and doxorubicin. An analysis of agonists, in combination with dexamethasone or melphalan in 83 cell lines, reveals substantial activity in multiple myeloma and diffuse large B-cell lymphoma cell lines. Combination effects are also observed with dexamethasone as well as bortezomib, using multiple myeloma patient samples and mouse multiple myeloma xenograft assays. Our results provide compelling evidence in support of development of A2A and ß2AR agonists for use in multi-drug combination therapy for multiple myeloma. Furthermore, use of cHTS for the discovery and evaluation of new targets and combination therapies has the potential to improve cancer treatment paradigms and patient outcomes.

Musashi-2 regulates normal hematopoiesis and promotes aggressive myeloid leukemia.

RNA-binding proteins of the Musashi (Msi) family are expressed in stem cell compartments and in aggressive tumors, but they have not yet been widely explored in the blood. Here we demonstrate that Msi2 is the predominant form expressed in hematopoietic stem cells (HSCs), and its knockdown leads to reduced engraftment and depletion of HSCs in vivo. Overexpression of human MSI2 in a mouse model increases HSC cell cycle progression and cooperates with the chronic myeloid leukemia-associated BCR-ABL1 oncoprotein to induce an aggressive leukemia. MSI2 is overexpressed in human myeloid leukemia cell lines, and its depletion leads to decreased proliferation and increased apoptosis. Expression levels in human myeloid leukemia directly correlate with decreased survival in patients with the disease, thereby defining MSI2 expression as a new prognostic marker and as a new target for therapy in acute myeloid leukemia (AML).

Adenosine A2A receptor agonists and PDE inhibitors: a synergistic multitarget mechanism discovered through systematic combination screening in B-cell malignancies.

Using a combination high-throughput screening technology, multiple classes of drugs and targeted agents were identified that synergize with dexamethasone (Dex) in multiple myeloma (MM) cells. Performing combination screening with these enhancers, we discovered an unexpected synergistic interaction between adenosine receptor agonists and phosphodiesterase (PDE) inhibitors that displays substantial activity in a panel of MM and diffuse large B-cell lymphoma (DLBCL) cell lines and tumor cells from MM patients. We have used selective adenosine receptor agonists, antagonists, and PDE inhibitors as well as small interfering RNAs targeting specific molecular isoforms of these proteins to dissect the molecular mechanism of this synergy. The adenosine A2A receptor and PDE2, 3, 4, and 7 are important for activity. Drug combinations induce cyclic AMP (cAMP) accumulation and up-regulate PDE4B. We also observe rigorous mathematical synergy in 3-way combinations containing A2A agonists, PDE inhibitors, and Dex at multiple concentrations and ratios. Taken together, these data suggest that A2A agonist/PDE inhibitor combinations may be attractive as an adjunctive to clinical glucocorticoid containing regiments for patients with MM or DLBCL and confer benefit in both glucocorticoid-sensitive and -resistant populations.

Id1 is a common downstream target of oncogenic tyrosine kinases in leukemic cells.

Oncogenic tyrosine kinases, such as BCR-ABL, TEL-ABL, TEL-PDGFbetaR, and FLT3-ITD, play a major role in the development of hematopoietic malignancy. They activate many of the same signal transduction pathways. To identify the critical target genes required for transformation in hematopoietic cells, we used a comparative gene expression strategy in which selective small molecules were applied to 32Dcl3 cells that had been transformed to factor-independent growth by these respective oncogenic alleles. We identified inhibitor of DNA binding 1 (Id1), a gene involved in development, cell cycle, and tumorigenesis, as a common target of these oncogenic kinases. These findings were prospectively confirmed in cell lines and primary bone marrow cells engineered to express the respective tyrosine kinase alleles and were also confirmed in vivo in murine models of disease. Moreover, human AML cell lines Molm-14 and K562, which express the FLT3-ITD and BCR-ABL tyrosine kinases, respectively, showed high levels of Id1 expression. Antisense and siRNA based knockdown of Id1-inhibited growth of these cells associated with increased p27(Kip1) expression and increased sensitivity to Trail-induced apoptosis. These findings indicate that Id1 is an important target of constitutively activated tyrosine kinases and may be a therapeutic target for leukemias associated with oncogenic tyrosine kinases.

Can FLT3 inhibitors overcome resistance in AML?

The identification of FLT3 mutations across a range of the cytogenetic subgroups of AML has opened up the possibility of a targeted therapeutic approach with broad applicability. Four agents are currently in clinical trials, at least 3 of which have both sufficient activity against AML and sufficiently acceptable toxicity profiles to support continued efforts to refine their inclusion into therapeutic regimens for AML. Better understanding of the genetics of inherent and acquired resistance is needed to guide development of second-generation agents. Optimizing the integration of FLT3 inhibitor therapy with chemotherapy has the potential both to decrease toxicity and improve response.

Mechanism of sorting proopiomelanocortin and proenkephalin to the regulated secretory pathway of neuroendocrine cells.

Proopiomelanocortin (POMC) and proenkephalin (PE) are synthesized at the endoplasmic reticulum and transported to the trans-Golgi network (TGN) where they are sorted and packaged into dense-core granules of the regulated secretory pathway (RSP). The mechanism of sorting POMC and PE to the RSP in neuroendocrine cells was investigated. Consensus sorting signals comprising two acidic residues and two hydrophobic residues exposed on the surface of N-POMC(1-26) and N-PE(1-32) were identified and shown to be sufficient and necessary for targeting POMC and PE to the RSP in PC12, Neuro2a, and AtT-20 cells. The acidic residues of these sorting signals bind specifically to basic residues on the sorting receptor membrane, carboxypeptidase E (CPE), to effect sorting to the RSP. Analysis of POMC and PE sorting in Neuro2a cells depleted of CPE by CPE antisense RNA, and Cpe(fat/fat) mouse pituitary cells lacking CPE showed missorting of both these molecules to the constitutive pathway in vivo. Thus, POMC and PE are sorted to the RSP at the TGN by a mechanism involving the interaction of a specific sorting signal on these molecules with the sorting receptor, CPE.