Activating mutations of the ALK (Anaplastic lymphoma Kinase) gene have been identified in sporadic and familial cases of neuroblastoma, a cancer of early childhood arising from the sympathetic nervous system (SNS). To decipher ALK function in neuroblastoma predisposition and oncogenesis, we have characterized knock-in (KI) mice bearing the two most frequent mutations observed in neuroblastoma patients. A dramatic enlargement of sympathetic ganglia is observed in AlkF1178L mice from embryonic to adult stages associated with an increased proliferation of sympathetic neuroblasts from E14.5 to birth. In a MYCN transgenic context, the F1178L mutation displays a higher oncogenic potential than the R1279Q mutation as evident from a shorter latency of tumor onset. We show that tumors expressing the R1279Q mutation are sensitive to ALK inhibition upon crizotinib treatment. Furthermore, our data provide evidence that activated ALK triggers RET upregulation in mouse sympathetic ganglia at birth as well as in murine and human neuroblastoma. Using vandetanib, we show that RET inhibition strongly impairs tumor growth in vivo in both MYCN/KI AlkR1279Q and MYCN/KI AlkF1178L mice. Altogether, our findings demonstrate the critical role of activated ALK in SNS development and pathogenesis and identify RET as a therapeutic target in ALK mutated neuroblastoma.

Activation of thermogenic beige adipocytes has recently emerged as a promising therapeutic target in obesity and diabetes. Relevant human models for beige adipocyte differentiation are essential to implement such therapeutic strategies. We report a straightforward and efficient protocol to generate functional human beige adipocytes from human induced pluripotent stem cells (hiPSCs). Without overexpression of exogenous adipogenic genes, our method recapitulates an adipogenic developmental pathway through successive mesodermal and adipogenic progenitor stages. hiPSC-derived adipocytes are insulin sensitive and display beige-specific markers and functional properties, including upregulation of thermogenic genes, increased mitochondrial content, and increased oxygen consumption upon activation with cAMP analogs. Engraftment of hiPSC-derived adipocytes in mice produces well-organized and vascularized adipose tissue, capable of β-adrenergic–responsive glucose uptake. Our model of human beige adipocyte development provides a new and scalable tool for disease modeling and therapeutic screening.

Neurotensin receptor 1 (NTSR1) is overexpressed in human pancreatic ductal adenocarcinoma (PDAC). Specific noninvasive positron-emission tomography (PET) imaging probes may improve the diagnostic accuracy and the monitoring of therapy for patients with PDAC. Here, we report the use of the 68 Ga-labeled neurotensin (NTS) analogue DOTA-NT-20.3 to image human PDAC in animal models and to discriminate tumors from pancreatitis. In addition to the preclinical study, two tissue microarray slides, constructed by small core biopsies (2−5) from standard paraffin-embedded tumor tissues, were used to confirm the high (78%) positivity rate of NTSR1 expression in human PDAC. PET imaging, biodistribution, blocking, and histology studies were performed in subcutaneous AsPC-1 pancreatic tumor-bearing mice. 68 Ga-DOTA-NT-20.3 PET images showed rapid tumor uptake and high contrast between the tumor and background with a fast blood clearance and a moderate accumulation in the kidneys. Ex vivo biodistribution showed low uptake in normal pancreas (0.22% IA/g) and in the remaining organs at 1 h postinjection, kidney retention (5.38 ± 0.54% IA/g), and fast clearance from blood and confirmed high uptake in tumors (5.28 ± 0.93% IA/g), leading to a tumor-to-blood ratio value of 6 at 1 h postinjection. The significant decrease of tumor uptake in a blocking study demonstrated the specificity of 68 Ga-DOTA-N-T20.3 to target NTSR1 in vivo. PET imaging was also conducted in an orthotopic xenograft model that allows tumors to grow in their native microenvironment and in an experimental pancreatitis model generated by caerulein injections. As opposed to 2-[ 18 F]fluoro-deoxyglucose, 68 Ga-DOTA-NT-20.3 distinguishes PDAC from pancreatitis. Thus, 68 Ga-DOTA-NT-20.3 is a promising PET imaging probe for imaging PDAC in humans.

We describe the potentiality of a new liposomal formulation enabling positron emission tomography (PET) and magnetic resonance MR() imaging. The bimodality is achieved by coupling a Ga-based radiotracer on the bilayer of magnetic liposomes. In order to enhance the targeting properties obtained under a permanent magnetic field, a sugar moiety was added in the lipid formulation. Two new phospholipids were synthesized, one with a specific chelator ofGa (DSPE-PEG-NODAGA) and one with a glucose moiety (DSPE-PEG-glucose). The liposomes were produced according to a fast and safe process, with a high radiolabeling yield. MR and PET imaging were performed on mice bearing human glioblastoma tumors (U87MG) after iv injection. The accumulation of the liposomes in solid tumor is evidenced by MR imaging and the amount is evaluated in vivo and ex vivo according to PET imaging. An efficient magnetic targeting is achieved with these new magnetic liposomes.

Rationale: We aimed to predict the presence of vaccine-induced hypermetabolic lymph nodes (v-HLN) on 18 F-FDG PET/CT after Coronavirus disease 2019 (COVID-19) vaccination and determine their association with lymphocyte counts. Methods: In this retrospective single-center study, we included consecutive patients who underwent 18 F-FDG PET/CT imaging after mRNA-or viral vector-based COVID-19 vaccination between early March and late April 2021. Demographic, clinical parameters and absolute lymphocyte count (ALC) were collected and their association with the presence of v-HLN in the draining territory was studied by logistic regression.Results: Two hundred and sixty patients were eligible, including 209 (80%) women and 145 (56%) with breast cancer. The median age was 50 years (range, 23-96). Two hundred thirty-three patients (90%) received the mRNA vaccine. Ninety (35%) patients had v-HLN with a median SUVmax of 3.7 [range, 2.0-26.3] and 74 (44%) displayed lymphopenia with a median ALC of 1.4 G/L [range, 0.3-18.3]. Age ≤ 50 years (odds ratio [OR] 2.2, 95%CI 1.0-4.5), the absence of lymphopenia (OR 2.2, 95%CI 1.1-4.3) and the delay from the last vaccine injection to the date of 18 F-FDG PET/CT, if < 30 days (OR 2.6, 95%CI 1.3-5.6), were independent factors for v-HLN in multivariate analysis. In breast cancer patients, the absence of lymphopenia was the only independent factor significantly associated with v-HLN (OR 2.9, 95%CI 1.2-7.4).Conclusions: Patients with normal values of ALC after COVID-19 vaccine were more likely to have v-HLN on 18 F-FDG PET/CT, which might both be associated to a stronger immune response to vaccination. KEYWORDS 18 F-FDG PET/CT; COVID-19 vaccination; absolute lymphocyte count; hypermetabolic lymph nodes; immune response. KEY-POINTSQUESTION: Could we use lymphocyte count lymphocyte for predicting the presence of vaccineinduced hypermetabolic lymph node(s) in the drainage territory on 18 F-FDG PET/CT following COVID-19 vaccination?PERTINENT FINDINGS: This retrospective and monocentric study included 260 vaccinated patients who underwent 18 F-FDG PET/CT following mRNA based-or viral vector based-COVID-19 vaccination. Patients' absolute lymphocyte count (>lower limit of normal), along with patients' age (≤ 50 years) and the timing of last injection dose (< 30 days), significantly correlated with vaccine-induced hypermetabolic lymph node(s).IMPLICATIONS FOR PATIENT CARE: Patients displaying normal count of lymphocytes after COVID-19 vaccination are more likely to present vaccine-induced hypermetabolic lymph node(s) on 18 F-FDG PET/CT and could subsequently have higher seropositivity likelihood and antibody titers.