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Melanoma GEMM Tumors, untreated or vemurafenib treated (scRNASeq)

ABSTRACT: Emerging research suggests that multiple tumor compartments can influence treatment responsiveness and relapse, yet the search for therapeutic resistance mechanisms remains largely focused on acquired genomic alterations in cancer cells. Here, we show how treatment-induced changes occur in multiple tumor compartments during tumor relapse and can reduce benefit of follow-on therapies. By utilizing serial biopsies, next generation sequencing and single cell transcriptomics, we tracked the evolution of multiple cellular compartments within individual lesions during first-line treatment response, relapse and second-line therapeutic interventions in an autochthonous model of melanoma. We discovered that while treatment-relapsed tumors remained genetically stable, they converged on a shared resistance phenotype characterized by dramatic changes in tumor cell differentiation state, immune infiltration and extracellular matrix (ECM) composition. Similar alterations in tumor cell differentiation were also observed in more than half of our treatment-relapsed patient tumors. Tumor cell state changes were coincident with ECM remodeling and increased tumor stiffness, which alone was sufficient to alter tumor cell fate and reduce treatment responses in melanoma cell lines in vitro. Despite the absence of acquired mutations in the targeted pathway, resistant tumors showed significantly decreased responsiveness to second-line therapy intervention within the same pathway. The ability to preclinically model relapse and refractory settings - while capturing dynamics within and crosstalk between all relevant tumor compartments - provides a unique opportunity to better design and sequence appropriate clinical interventions. The "SAMPLE_ID" sample characteristic is a sample identifier internal to Genentech. The ID of this project in Genentech's ExpressionPlot database is NGS2034.

ORGANISM(S): Mus musculus

PROVIDER: GSE126714 | GEO | 2019/03/08

REPOSITORIES: GEO

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Project description:We undertook a comprehensive clinical and biological investigation of serial medulloblastoma biopsies obtained at diagnosis and relapse. Combined MYC gene family amplifications and P53 pathway defects commonly emerged at relapse, and all patients in this molecular group died of rapidly progressive disease post-relapse. To study this genetic interaction, we investigated a transgenic model of MYCN-driven medulloblastoma and found spontaneous development of Trp53 inactivating mutations. Abrogation of Trp53 function in this model produced aggressive tumors that mimicked the characteristics of relapsed human tumors with combined P53–MYC dysfunction. Restoration of p53 activity, genetic and therapeutic suppression of MYCN all reduced tumor growth and prolonged survival. Our findings identify P53–MYC interactions which emerge at medulloblastoma relapse as biomarkers of clinically aggressive disease that may be targeted therapeutically. There are currently no effective therapies for children with relapsed medulloblastoma. While clinical and biological features of the disease at diagnosis are increasingly well understood, biopsy is rarely performed at relapse and few biological data are available to guide more effective treatments. Here, we show that medulloblastomas develop altered biology at relapse which is predictive of disease course and cannot be detected at diagnosis. We have discovered the emergence of P53–MYC interactions at relapse, as biomarkers of clinically aggressive relapsed disease, which can be modelled and targeted therapeutically in genetically-engineered mice. These data provide clear precedent for the incorporation of biopsy at relapse into routine clinical practice, to direct palliative care and the development of improved treatment strategies. mouse model expression profiles from various mouse Medulloblastoma models MYCN/MYC overexpressing with/without p53 Mutations were compared to human MB expression profiles using Non-negative Matrix Factorization projection in order to sub-type the mouse models

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Melanoma GEMM Tumors, untreated or vemurafenib treated (scRNASeq)

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