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Abstract Background Glioblastoma (GBM) brain tumors lacking IDH1 mutations (IDHwt) have the worst prognosis of all brain neoplasms. Patients receive surgery and chemoradiotherapy but tumors almost always fatally recur. Results Using RNA sequencing data from 107 pairs of pre- and post-standard treatment locally recurrent IDHwt GBM tumors, we identify two responder subtypes based on longitudinal changes in gene expression. In two thirds of patients, a specific subset of genes is upregulated from primary to recurrence (Up responders), and in one third, the same genes are downregulated (Down responders), specifically in neoplastic cells. Characterization of the responder subtypes indicates subtype-specific adaptive treatment resistance mechanisms that are associated with distinct changes in the tumor microenvironment. In Up responders, recurrent tumors are enriched in quiescent proneural GBM stem cells and differentiated neoplastic cells, with increased interaction with the surrounding normal brain and neurotransmitter signaling, whereas Down responders commonly undergo mesenchymal transition. ChIP-sequencing data from longitudinal GBM tumors suggests that the observed transcriptional reprogramming could be driven by Polycomb-based chromatin remodeling rather than DNA methylation. Conclusions We show that the responder subtype is cancer-cell intrinsic, recapitulated in in vitro GBM cell models, and influenced by the presence of the tumor microenvironment. Stratifying GBM tumors by responder subtype may lead to more effective treatment.

Exit of quiescent disseminated cancer cells from dormancy is thought to be responsible for metastatic relapse and a better understanding of dormancy could pave the way for novel therapeutic approaches. We used an in vivo model of triple negative breast cancer brain metastasis to identify differences in transcriptional profiles between dormant and proliferating cancer cells in the brain. BGN gene, encoding a small proteoglycan biglycan, was strongly upregulated in dormant cancer cells in vivo. BGN expression was significantly downregulated in patient brain metastases as compared to the matched primary breast tumors and BGN overexpression in cancer cells inhibited their growth in vitro and in vivo. Dormant cancer cells were further characterized by a reduced expression of glycolysis genes in vivo, and inhibition of glycolysis in vitro resulted in a reversible growth arrest reminiscent of dormancy. Our study identified mechanisms that could be targeted to induce/maintain cancer dormancy and thereby prevent metastatic relapse.

Subclonal deconvolution in cancer sequencing data is a complex task, and the optimal tools to use are unclear. Here, the authors systematically benchmark subclonal deconvolution pipelines with a comprehensive set of simulated tumour genomes and identify the best-performing methods.

Cut-like homeobox 1 (CUX1) is a haploinsufficient tumor suppressor commonly inactivated in acute myeloid leukemia and high-risk myelodysplasia. Here, in a genetically modified murine model, the authors show that CUX1 deficiency impairs apoptosis leading to leukemia when combined with mutant Flt3-ITD.

Louise van der Weyden et al. report a CRISPRa screen in mice to identify membrane protein-encoding genes that, when overexpressed, enhance the metastatic potential of melanoma cells. They find that high expression of LRRN4CL in melanoma cells increases lung metastases in mice and correlates with poorer survival in melanoma patients, suggesting it could be a promising drug target.

Systematic screens for synthetic lethal gene pairs represent a powerful approach to define interactions that may be exploited in the clinic. Here, the authors use a dual-guide CRISPR screening approach to screen a curated selection of gene pairs across three cell lines and validate the Fam50a/Fam50b synthetic lethality was in isogenic cell models as well as in an in vivo setting.

Mutations in pre-mRNA processing factors cause autosomal dominant retinitis pigmentosa. Here the authors provide insights into the pathophysiological mechanisms underlying non-syndromic retinal disease caused by heterozygous mutations in genes encoding ubiquitously expressed splicing factors.