A Wnt-producing niche drives proliferative potential and progression in lung adenocarcinoma

The heterogeneity of cellular states in cancer has been linked to drug resistance, cancer progression and the presence of cancer cells with properties of normal tissue stem cells. Secreted Wnt signals maintain stem cells in various epithelial tissues, including in lung development and regeneration. Here we show that mouse and human lung adenocarcinomas display hierarchical features with two distinct subpopulations, one with high Wnt signalling activity and another forming a niche that provides the Wnt ligand. The Wnt responder cells showed increased tumour propagation ability, suggesting that these cells have features of normal tissue stem cells. Genetic perturbation of Wnt production or signalling suppressed tumour progression. Small-molecule inhibitors targeting essential posttranslational modification of Wnt reduced tumour growth and markedly decreased the proliferative potential of lung cancer cells, leading to improved survival of tumour-bearing mice. These results indicate that strategies for disrupting pathways that maintain stem-like and niche cell phenotypes can translate into effective anti-cancer therapies

The medical student

The Medical Student was published from 1888-1921 by the students of Boston University School of Medicine

The medical student

The Medical Student was published from 1888-1921 by the students of Boston University School of Medicine

Synthetic circular RNA for protein expression

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2019Cataloged from PDF version of thesis.Includes bibliographical references (pages 111-126).Messenger RNA (mRNA) has broad potential for therapeutic and engineering applications. One fundamental limitation of mRNA is its relatively short half-life in biological systems, effected in part by rapid exonuclease-mediated degradation upon delivery. Circular RNA (circRNA), a type of single-stranded RNA with a contiguous structure that lacks the end motifs necessary for exonuclease recognition, may be resistant to this mechanism of degradation and therefore may exhibit superior stability. However, challenges in circularization, purification, and protein expression have impeded a thorough investigation of exogenous circRNA. By rationally designing ubiquitous accessory sequences to facilitate circularization, we engineered a permuted self-splicing intron that efficiently circularized RNAs up to 5kb in length in vitro.With the addition of these accessory sequences, we were able to demonstrate nearly complete circularization of precursor RNAs containing an internal ribosome entry site (IRES) for translation initiation and a coding region such as erythropoietin or eGFP. We found that translation from optimized circRNA was robust, and circRNA protein expression stability far exceeded that of both unmodified and nucleoside modified linear mRNA in some cellular contexts. We monitored cytokine release and antiviral defense induction in sensitive cells transfected with circRNA purified by different methods and found that the immunogenicity and stability of circRNA preparations was dependent on the degree of purity, with small amounts of contaminating linear RNA leading to robust cellular immune responses.In contrast to purified unmodified linear mRNA, purified unmodified circRNA was invisible to several RNA sensors including RIG-i and endosomai toil-like receptors (TLRs) and did not provoke a significant cytokine response upon transfection. Using purified circRNA, we finally provided the first demonstration to our knowledge of exogenous circRNA delivery and translation in vivo, and showed that the duration of circRNA translation was extended in adipose tissue in comparison to unmodified and uridine-modified linear mRNAs. In total, this work suggests that circRNA is a promising alternative to linear mRNA for therapeutic applications.by R. Alexander Wesselhoeft.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Biolog

RNA Circularization Diminishes Immunogenicity and Can Extend Translation Duration In Vivo

© 2019 Elsevier Inc. Wesselhoeft et al. find that exogenous circular RNAs are able to bypass RNA sensors, thereby avoiding antiviral defense induction upon cellular entry. They report that nanoformulated, synthetic protein-coding circRNA can be translated in mouse tissues, providing evidence for the potential of circRNA as a vector for therapeutic gene expression