Identifying and targeting vulnerabilities in cancers that metastasize to the bone and bone marrow

Evolving technologies enable scientist to ask and seek answers to advanced questions, above and beyond. During the past decade single-cell RNA sequencing (scRNA-seq) has revolutionized our understanding of biology, in particular within cancer research. Contributing with its high-resolution has unraveled complicated biological circuits, along with a profound understanding of heterogeneity, cellular and molecular processes, including gene expression profiles and transcriptional states. Especially in the quest of understanding cancer metastasis, aggressive disease phenotype and treatment resistance. In Paper I we utilize scRNA-seq on tissue material from untreated human primary clear cell renal cell carcinoma (ccRCC) patients. We dissect the tumor microenvironment (TME) and discover a metastatic gene signature that is upregulated in bone metastatic ccRCC patients that could serve as a predictive tool. We describe an immunosuppressive microenvironment with tumor associated macrophages (TAMs) with a M2 phenotype overexpressing TREM2, further associated with low survival outcome. Computational interactive receptor-ligand analysis reveals CD70 (on tumor) and CD27 (on cytotoxic T cells and regulatory T cells) as a potential pharmaceutical target. In Paper II, a continuation of Paper I, we aimed to understand genetic alterations involved in metastatic disease from the primary site, namely bone metastatic ccRCC, including comparison of a normal bone marrow to malignant. Scrutinizing the complex TME we detect, as well here, an immunosuppressive microenvironment with transcriptionally different TAMs, exhausted T cell phenotype and a tumor associated mesenchymal stem/stromal cell (TA-MSC) population that upregulates bone remodeling genes. Concluding that the relevance of TA-MSC subset causes excessive bone resorption via RANK/RANKL/OPG signaling pathway. Finally, in Paper III, we evaluate brequinar, a DHODH inhibitor, as a therapeutic agent in high-risk neuroblastoma (NB). We find DHODH as an independent risk factor in high-risk NB demonstrating prolonged survival in preclinical models when inhibited. In combination with temozolomide, already in clinical use for these children, a synergistic effect is achieved in vivo, proposing a promising approach to validate clinically. Taken together, the presented thesis has provided comprehensive insights in the progression of ccRCC in a primary and a metastatic setting, including the identification of potential vulnerable targets. Additionally, a potential combination treatment in vitro and in vivo is presented as a promising treatment option in high-risk NB by inhibiting DHODH together with standard care of treatment agent temozolomide

DHODH is an independent prognostic marker and potent therapeutic target in neuroblastoma

Despite intensive therapy, children with high-risk neuroblastoma are at risk of treatment failure. We applied a multiomic system approach to evaluate metabolic vulnerabilities in human neuroblastoma. We combined metabolomics, CRISPR screening, and transcriptomic data across more than 700 solid tumor cell lines and identified dihydroorotate dehydrogenase (DHODH), a critical enzyme in pyrimidine synthesis, as a potential treatment target. Of note, DHODH inhibition is currently under clinical investigation in patients with hematologic malignancies. In neuroblastoma, DHODH expression was identified as an independent risk factor for aggressive disease, and high DHODH levels correlated to worse overall and event-free survival. A subset of tumors with the highest DHODH expression was associated with a dismal prognosis, with a 5-year survival of less than 10%. In xenograft and transgenic neuroblastoma mouse models treated with the DHODH inhibitor brequinar, tumor growth was dramatically reduced, and survival was extended. Furthermore, brequinar treatment was shown to reduce the expression of MYC targets in 3 neuroblastoma models in vivo. A combination of brequinar and temozolomide was curative in the majority of transgenic TH-MYCN neuroblastoma mice, indicating a highly active clinical combination therapy. Overall, DHODH inhibition combined with temozolomide has therapeutic potential in neuroblastoma, and we propose this combination for clinical testing.Thale Kristin Olsen, Cecilia Dyberg, David B Sykes, and Ninib Baryawno contributed equally to this work.</p