ABSTRACT
INTRODUCTION: Microtubule (MT) stability is crucial for proper neuronal function. Understanding MT dysregulation is critical for connecting amyloid beta (Aß) and tau-based degenerative events and early changes in presymptomatic Alzheimer's disease (AD). Herein we present positron emission tomography (PET) imaging properties of our MT-PET radiotracer, [11C]MPC-6827, in multiple established AD mouse models. METHODS: Longitudinal PET, biodistribution, autoradiography, immunohistochemistry, and behavioral studies were conducted at multiple time points in APPswe/PSEN1dE9 (APP/PS1), P301S-PS19 (P301S), 5xFAD, and age-matched control mice. RESULTS: Longitudinal [11C]MPC-6827 brain imaging showed significant increases in APP/PS1, P301S, and 5xFAD mice compared to controls. Longitudinal MT-PET correlated positively with biodistribution, autoradiography, and immunohistochemistry results and negatively with behavior data. DISCUSSION: Our study demonstrated significant longitudinal [11C]MPC-6827 PET increases in multiple AD mouse models for the first time. Strong correlations between PET and biomarker data underscored the interplay of MT destabilization, amyloid, and tau pathology in AD. These results suggest [11C]MPC-6827 PET as a promising tool for monitoring MT dysregulation early in AD progression. HIGHLIGHTS: Longitudinal positron emission tomography (PET) imaging studies using [11C]MPC-6827 in multiple established Alzheimer's disease (AD) mouse models revealed an early onset of microtubule dysregulation, with significant changes in brain radiotracer uptake evident from 2 to 4 months of age. Intra-group analysis showed a progressive increase in microtubule dysregulation with increasing AD burden, supported by significant correlations between PET imaging data and biodistribution, autoradiography, and molecular pathological markers. [11C]MPC-6827 PET imaging demonstrated its efficacy in detecting early microtubule alterations preceding observable behavioral changes in AD mouse models, suggesting its potential for early AD imaging. The inclusion of the 5xFAD mouse model further elucidated the impact of amyloid beta (Aß) toxicity on inducing tau hyperphosphorylation-mediated microtubule dysregulation, highlighting the versatility of [11C]MPC-6827 in delineating various aspects of AD pathology. Our study provides immediate clarity on high uptake of the microtubule-based radiotracer in AD brains in a longitudinal setting, which directly informs clinical utility in Aß/tau-based studies.
ABSTRACT
High-grade (HG) pancreatic neuroendocrine neoplasms (PAN-NENs) are aggressive and have a poor prognosis. Yet, our understanding and treatment approaches for these tumors have rapidly evolved in the past decade, despite a lack of prospective and randomized trials. It is essential to differentiate grade 3 (G3) neuroendocrine tumors (NETs) from neuroendocrine carcinomas (NECs) due to their different prognostic and treatment implications. The molecular landscape of HG PAN-NENs is complex, with mutations in key cancer-related genes, extensive genomic rearrangements, and chromosomal instability. Advanced studies have provided insights into the significant genetic heterogeneity of HG PAN-NENs and potential therapeutic targets. Several therapeutic strategies have emerged from molecular characterization studies. These include agents targeting the mammalian target of rapamycin (mTOR) pathway, DNA repair pathways, and epigenetic modifiers. Moreover, high programmed cell death ligand 1 (PD-L1) expression in some tumors indicates potential for immunotherapy. However, many challenges remain, with a deeper understanding of the genetic and epigenetic alterations in these tumors necessary to develop novel therapeutic strategies and improve patient outcomes. Treatment strategies for HG PAN-NENs vary. Looking to the future, many clinical trials are exploring novel therapies or combinations of known therapies to improve outcomes. It is evident that understanding the molecular landscape of PAN-NECs, alongside personalized therapeutic strategies, is crucial to developing effective treatment options and improving patient outcomes. In this discourse, our emphasis will be on the molecular landscape and available treatment strategies for HG PAN-NECs.
