For its microtubule-binding properties, the expression level of the neurodegeneration-associated protein Tau is pondered as a potential modifier of cancer resistance to chemotherapy since decades. Indeed, Tau binds microtubules at the same site as taxanes, a class of chemotherapeutic drugs designed to stabilize the microtubule network in order to stall cell division and to induce tumor cell death. Whilst independent studies report the association between low Tau expression and superior taxane response, the data were refused by a meta-analysis, suggesting interference of other parameters. Unpredictably, Tau expression level was identified as a prognostic cancer marker, whereby its positive or negative predictive value for survival depended on the cancer type. With recent experimental evidence linking Tau to P53 signaling, DNA stability and protection and to the implication of Tau in cancer is strengthened. The identification of a role of Tau at the interface between two major aging-related disorder families, neurodegeneration and cancer, offers clues for the epidemiological observation inversely correlating these disorders. Elucidating how Tau is mechanistically implicated in cellular pathways common to these devastating illnesses may extend the Tau-targeting therapeutic opportunities to cancer.

TSPO-PET tracers are sensitive to a single-nucleotide-polymorphism (rs6971-SNP) resulting in low (LAB), medium (MAB) and high (HAB) affinity binders, but the clinical relevance for [18F]GE-180 is still unclear. We evaluate the impact of rs6971-SNP on in vivo [18F]GE-180 binding in healthy brain and in pseudo-reference tissue in neurooncological and neurodegenerative diseases. Standardized uptake values (SUV) of [18F]GE-180-PET were assessed using a manually drawn region of interest in the fronto-parietal and cerebellar hemisphere. SUVs were compared between LAB, MAB and HAB in controls, glioma, 4-repeat tauopathies (4RT) and Alzheimer’s disease (AD) subjects. Second, SUVs were compared between patients and controls within their rs6971-subgroup. After exclusion of patients with prior therapy, n=24 LABs (n=7 controls, n=5 glioma, n=6 4RT, n=6 AD) were analysed. Age- and sex-matched MABs (n=38) and HABs (n=50) were selected. LABs had lower fronto-parietal and cerebellar SUVs when compared to MABs and HABs, but no significant difference was observed between MABs and HABs. Within each rs6971 group no SUV difference between patients and controls was detected in the pseudo-reference tissues. The rs6971-SNP affects [18F]GE-180 quantification, revealing lower binding in LABs when compared to MABs/HABs. Fronto-parietal and cerebellar ROIs were successfully validated as pseudo-reference regions.

Spinocerebellar ataxia type 2 (SCA2) is caused by polyglutamine expansion in Ataxin-2 (ATXN2). This factor binds RNA/proteins to modify metabolism after stress, and to control calcium (Ca2+) homeostasis after stimuli, thus exerting crucial neuroprotection for cerebellar ataxias and corticospinal motor neuron degeneration. Our Atxn2-CAG100-Knock-In mouse faithfully models features observed in patients at pre-onset, early and terminal stages. Here, its cerebellar global RNA profiling revealed downregulation of signaling cascades to precede motor deficits. Validation work at mRNA/protein level defined alterations that were independent of constant physiological ATXN2 functions, but specific for RNA/aggregation toxicity, and progressive across the short lifespan. Earliest changes were detected at 3 months among Ca2+ channels/transporters (Itpr1, Ryr3, Atp2a2, Atp2a3, Trpc3), IP3 metabolism (Plcg1, Inpp5a, Itpka), and Ca2+-Calmodulin dependent kinases (Camk2a, Camk4). CaMKIV–Sam68 control over alternative splicing of Nrxn1, an adhesion component of glutamatergic synapses between granule and Purkinje neurons, was found affected. Systematic screening of pre/post-synapse components, with dendrite morphology assessment, suggested early impairment of CamKIIα abundance together with weakening of parallel fiber connectivity. These data reveal molecular changes due to ATXN2 pathology, impacting communication and excitability of cerebellar neurons. Discovery of such risk versus progression markers improves the assessment of pre-symptomatic treatments in SCA2 and related disorders.