👤 Olaf Riess

Spinocerebellar Ataxia Type 3 (SCA3) is an autosomal dominant neurodegenerative Polyglutamine (polyQ) disease, caused by a cytosine-adenine-guanine (CAG) repeat expansion in the ATXN3 gene, resulting in an expanded polyQ tract in the Ataxin-3 protein. Although the principal genetic determinant of the age at onset (AAO) in polyQ diseases is the expanded CAG repeat length, variability in AAO has been explained only partly, suggesting the existence of additional genetic modifiers. Apolipoprotein E (APOE) haplotypes are associated with the risk of numerous, especially degenerative, diseases. Investigations of a potential role of APOE haplotypes in AAO variability of SCA3 have resulted in partly conflicting outcomes, with current evidence lacking power and patient diversity. To further clarify a potential modifying effect of APOE haplotypes on the AAO in SCA3, over 800 SCA3 patients from different origins were enrolled in the present study. While we did not find an association of common APOE haplotypes or singular APOE alleles with AAO in SCA3, rare ε4 homozygosity was linked to an earlier AAO in individuals from Brazil, with a mean disease onset six years earlier than carriers of other APOE haplotypes. Our study thus provides initial evidence for a relevant impact of ε4 homozygosity on disease onset in SCA3 and provides evidence supporting an allele-dosage effect of APOE ε4 in polyQ diseases. Show less

One strategy for combating cancer-drug resistance is to deploy rational polytherapy up front that suppresses the survival and emergence of resistant tumor cells. Here we demonstrate in models of lung adenocarcinoma harboring the oncogenic fusion of ALK and EML4 that the GTPase RAS-mitogen-activated protein kinase (MAPK) pathway, but not other known ALK effectors, is required for tumor-cell survival. EML4-ALK activated RAS-MAPK signaling by engaging all three major RAS isoforms through the HELP domain of EML4. Reactivation of the MAPK pathway via either a gain in the number of copies of the gene encoding wild-type K-RAS (KRAS(WT)) or decreased expression of the MAPK phosphatase DUSP6 promoted resistance to ALK inhibitors in vitro, and each was associated with resistance to ALK inhibitors in individuals with EML4-ALK-positive lung adenocarcinoma. Upfront inhibition of both ALK and the kinase MEK enhanced both the magnitude and duration of the initial response in preclinical models of EML4-ALK lung adenocarcinoma. Our findings identify RAS-MAPK dependence as a hallmark of EML4-ALK lung adenocarcinoma and provide a rationale for the upfront inhibition of both ALK and MEK to forestall resistance and improve patient outcomes. Show less