Exploiting 4-1BB immune checkpoint to enhance the efficacy of oncolytic virotherapy for diffuse intrinsic pontine gliomas.

Diffuse intrinsic pontine gliomas (DIPGs) are aggressive pediatric brain tumors, and patient survival has not changed despite many therapeutic efforts, emphasizing the urgent need for effective treatments. Here, we evaluated the anti-DIPG effect of the oncolytic adenovirus Delta-24-ACT, which was engineered to express the costimulatory ligand 4-1BBL to potentiate the antitumor immune response of the virus. Delta-24-ACT induced the expression of functional 4-1BBL on the membranes of infected DIPG cells, which enhanced the costimulation of CD8+ T lymphocytes. In vivo, Delta-24-ACT treatment of murine DIPG orthotopic tumors significantly improved the survival of treated mice, leading to long-term survivors that developed immunological memory against these tumors. In addition, Delta-24-ACT was safe and caused no local or systemic toxicity. Mechanistic studies showed that Delta-24-ACT modulated the tumor-immune content, not only increasing the number, but also improving the functionality of immune cells. All of these data highlight the safety and potential therapeutic benefit of Delta-24-ACT the treatment of patients with DIPG.

The mechanistic GEMMs of oncogenic histones.

The last decade's progress unraveling the mutational landscape of all age groups of cancer has uncovered mutations in histones as vital contributors of tumorigenesis. Here we review three new aspects of oncogenic histones: first, the identification of additional histone mutations potentially contributing to cancer formation; second, tumors expressing histone mutations to study the crosstalk of post-translational modifications, and; third, development of sophisticated biological model systems to reproduce tumorigenesis. At the outset, we recapitulate the firstly discovered histone mutations in pediatric and adolescent tumors of the brain and bone, which still remain the most pronounced histone alterations in cancer. We branch out to discuss the ramifications of histone mutations, including novel ones, that stem from altered protein-protein interactions of cognate histone modifiers as well as the stability of the nucleosome. We close by discussing animal models of oncogenic histones that reproduce tumor formation molecularly and morphologically and the prospect of utilizing them for drug testing, leading to efficient treatment and cure of deadly cancers with histone mutations.

Somatic genome editing with the RCAS-TVA-CRISPR-Cas9 system for precision tumor modeling.

To accurately recapitulate the heterogeneity of human diseases, animal models require to recreate multiple complex genetic alterations. Here, we combine the RCAS-TVA system with the CRISPR-Cas9 genome editing tools for precise modeling of human tumors. We show that somatic deletion in neural stem cells of a variety of known tumor suppressor genes (Trp53, Cdkn2a, and Pten) leads to high-grade glioma formation. Moreover, by simultaneous delivery of pairs of guide RNAs we generate different gene fusions with oncogenic potential, either by chromosomal deletion (Bcan-Ntrk1) or by chromosomal translocation (Myb-Qk). Lastly, using homology-directed-repair, we also produce tumors carrying the homologous mutation to human BRAF V600E, frequently identified in a variety of tumors, including different types of gliomas. In summary, we have developed an extremely versatile mouse model for in vivo somatic genome editing, that will elicit the generation of more accurate cancer models particularly appropriate for pre-clinical testing.

Cell-Cycle-Targeting MicroRNAs as Therapeutic Tools against Refractory Cancers.

Cyclins and cyclin-dependent kinases (CDKs) are hyperactivated in numerous human tumors. To identify means of interfering with cyclins/CDKs, we performed nine genome-wide screens for human microRNAs (miRNAs) directly regulating cell-cycle proteins. We uncovered a distinct class of miRNAs that target nearly all cyclins/CDKs, which are very effective in inhibiting cancer cell proliferation. By profiling the response of over 120 human cancer cell lines, we derived an expression-based algorithm that can predict the response of tumors to cell-cycle-targeting miRNAs. Using systemic administration of nanoparticle-formulated miRNAs, we inhibited tumor progression in seven mouse xenograft models, including three treatment-refractory patient-derived tumors, without affecting normal tissues. Our results highlight the utility of using cell-cycle-targeting miRNAs for treatment of refractory cancer types.