Techniques to develop three-dimensional cell culture models are rapidly expanding to bridge the gap between conventional cell culture and animal models. Organoid and spheroid cultures have distinct and overlapping purposes and differ in cellular sources and protocol for establishment. Spheroids are of lower complexity structurally but are simple and popular models for drug screening. Organoids histologically and genetically resemble the original tumor from which they were derived. Ease of generation, ability for long-term culture and cryopreservation make organoids suitable for a wide range of applications. Organoids-on-chip models combine organoid methods with powerful designing and fabrication of micro-chip technology. Organoid-chip models can emulate the dynamic microenvironment of tumor pathophysiology as well as tissue–tissue interactions. In this review, we outline different tumor spheroid and organoid models and techniques to establish them. We also discuss the recent advances and applications of tumor organoids with an emphasis on tumor modeling, drug screening, personalized medicine and immunotherapy.

Imaging agents for nicotinic α4β2 receptors in the brain have been underway for studying various CNS disorders. Previous studies from our laboratories have reported the successful development of agonist, 18F-nifene. In attempts to develop potential antagonists, 18F-nifrolidine and 18F-nifzetidine were previously reported. Further optimization of these fluoropropyl derivatives has now been carried out resulting in 3-(2-(S)-3,4-dehydropyrrolinylmethoxy)-5-(3′-Fluoropropyl)pyridine (nifrolene) as a new high affinity agent for nicotinic α4β2 receptors. Nifrolene in rat brain homogenate assays—labeled with 3H-cytisine—exhibited a binding affinity of 0.36 nM. The fluorine-18 analog, 18F-nifrolene, was synthesized in approximately 10–20% yield and specific activity was estimated to be >2000 Ci/mmol. Rat brain slices indicated selective binding to anterior thalamic nuclei, thalamus, subiculum, striata, cortex and other regions consistent with α4β2 receptor distribution. This selective binding was displaced >90% by 300 µM nicotine. Thalamus to cerebellum ratio (>10) was the highest for 18F-nifrolene with several other regions showing selective binding. In vivo rat PET studies exhibited rapid uptake of 18F-nifrolene in the brain with specific retention in the thalamus and other brain regions while clearing out from the cerebellum. Thalamus to cerebellum ratio value in the rat was >4. Administration of nicotine caused a rapid decline in the thalamic 18F-nifrolene suggesting reversible binding to nicotinic receptors. PET imaging studies of 18F-nifrolene in anesthetized rhesus monkey revealed highest binding in the thalamus followed by regions of the lateral cingulated and temporal cortex. Cerebellum showed the least binding. Thalamus to cerebellum ratio in the monkey brain was >3 at 120 min. These ratios of 18F-nifrolene are higher than measured for 18F-nifrolidine and 18F-nifzetidine. 18F-Nifrolene thus shows promise as a new PET imaging agent for α4β2 nAChR.

The multicopper oxidases (MCOs) couple four 1e – oxidations of substrate to the 4e – reduction of O2 to H2O. These divide into two groups: those that oxidize organic substrates with high turnover frequencies (TOFs) up to 560 s–1 and those that oxidize metal ions with low TOFs, ∼1 s–1 or less. The catalytic mechanism of the organic oxidases has been elucidated, and the high TOF is achieved through rapid intramolecular electron transfer (IET) to the native intermediate (NI), which only slowly decays to the resting form. Here, we uncover the factors that govern the low TOF in Fet3p, a prototypical metallooxidase, in the context of the MCO mechanism. We determine that the NI decays rapidly under optimal turnover conditions, and the mechanism thereby becomes rate-limited by slow IET to the resting enzyme. Development of a catalytic model leads to the important conclusions that proton delivery to the NI controls the mechanism and enables the slow turnover in Fet3p that is functionally significant in Fe metabolism enabling efficient ferroxidase activity while avoiding ROS generation.

Whether initiation of statins could increase survival free of dementia and disability in adults aged ≥75 years is unknown. PREVENTABLE, a double‐blind, placebo‐controlled randomized pragmatic clinical trial, will compare high‐intensity statin therapy (atorvastatin 40 mg) with placebo in 20,000 community‐dwelling adults aged ≥75 years without cardiovascular disease, disability, or dementia at baseline. Exclusion criteria include statin use in the prior year or for >5 years and inability to take a statin. Potential participants are identified using computable phenotypes derived from the electronic health record and local referrals from the community. Participants will undergo baseline cognitive testing, with physical testing and a blinded lipid panel if feasible. Cognitive testing and disability screening will be conducted annually. Multiple data sources will be queried for cardiovascular events, dementia, and disability; survival is site‐reported and supplemented by a National Death Index search. The primary outcome is survival free of new dementia or persisting disability. Co‐secondary outcomes are a composite of cardiovascular death, hospitalization for unstable angina or myocardial infarction, heart failure, stroke, or coronary revascularization; and a composite of mild cognitive impairment or dementia. Ancillary studies will offer mechanistic insights into the effects of statins on key outcomes. Biorepository samples are obtained and stored for future study. These results will inform the benefit of statins for increasing survival free of dementia and disability among older adults. This is a pioneering pragmatic study testing important questions with low participant burden to align with the needs of the growing population of older adults.