Unknown,Transcriptomics,Genomics,Proteomics

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Patient-derived tumor grafts authentically reflect tumor pathology, growth, metastasis, and disease outcomes (expression)

ABSTRACT: Development and pre-clinical testing of new cancer therapies is limited by the scarcity of in vivo models that authentically reproduce tumor growth and metastatic progression. We report new models for breast tumor growth and metastasis, in the form of transplantable tumors derived directly from individuals undergoing treatment for breast cancer. These tumor grafts represent the diversity of human breast cancer and maintain essential features of the original tumors, including metastasis to specific sites. Co-engraftment of primary human mesenchymal stem cells maintains phenotypic stability of the grafts and increases tumor growth by promoting angiogenesis. We also report that tumor engraftment is a prognostic indicator of disease outcome for newly diagnosed women; orthotopic breast tumor grafting marks a step toward individualized models for tumor growth, metastasis, and prognosis. This bank of tumor grafts also serves as a publicly available resource for new models in which to study the biology of breast cancer. Single replicates of total RNA from 12 human breast cancer tumors and xenografts of those tumors in immunodeficient mice were hybridized to Agilent Whole Human Genome expression arrays.

ORGANISM(S): Homo sapiens

SUBMITTER: Alana Welm

PROVIDER: E-GEOD-32531 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Tumor-initiating cells with reprogramming plasticity and/or de-differentiation attributes have been thought to initiate primary tumor development as well as to regenerate secondary tumors in metastatic organs; however, the molecular mechanisms are not fully understood. We previously found that breast tumor-initiating cell marker, CD44, directs multicellular aggregation and cluster formation of circulating tumor cells (CTCs), which further enhance stemness and survival of such cells, enabling metastatic colonization to the lungs. To further elucidate the molecular network underlying CTC cluster formation, we performed global proteomic profiling and discovered that the tetraspanin protein CD81, which is normally enriched in exosomes (small extracellular vesicles), is a new driver of cancer initiation and metastasis as a facilitator and target of CD44. Loss of CD81 compromises tumorigenicity and mammosphere formation of triple negative breast cancer (TNBC) cells. Assisted by machine learning-based algorithms and mutagenesis approach, we found that CD81 interacts with CD44 on the cellular membrane through their extracellular regions. Notably, genetic knockout of CD44 or CD81 results in loss of both CD81 and CD44 in secreted exosomes, a state which abolishes exosome-induced self-renewal of recipient cells, such as mammosphere formation. In addition, RNA sequencing analysis showed that CD81 knockdown up-regulates expression of a cell differentiation marker, SEMA7a, whose down-regulation partially rescues mammosphere formation inhibition by CD81 depletion. Clinically, CD81 expression was observed in >80% of CTCs and specifically enriched and co-expressed along with CD44 in clustered CTCs of breast cancer patients. Mimicing the phenotypes of CD44 deficiency, loss of CD81 also inhibited tumor cell aggregation and lung metastasis of TNBC in both human and mouse tumor models, supporting the clinical significance of CD81 in association with patient outcomes. Our study highlights a new driving role of CD81 in cancer exosome-induced stemness, clustered CTCs, and metastasis initiation of TNBC, reported for the first time to our knowledge.

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Patient-derived tumor grafts authentically reflect tumor pathology, growth, metastasis, and disease outcomes (expression)

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