Metastasis-initiating cells dynamically adapt to the distinct microenvironments of different organs, but these early adaptations are poorly understood due to the limited sensitivity of in situ transcriptomics. We developed fluorouracil-labeled RNA sequencing (Flura-seq) for in situ analysis with unprecedented sensitivity. Flura-seq utilizes cytosine deaminase (CD) to convert fluorocytosine to fluorouracil, covalently labeling nascent RNA for purification and sequencing. Flura-seq revealed that breast cancer micrometastases in lung and brain exhibit unique, reversible gene signatures depending on the microenvironment. Specifically, the mitochondrial electron transport Complex I and the NRF2-driven antioxidant programs were induced in oxygen-rich pulmonary micrometastases, compared to mammary tumors or brain micrometastases. Loss of Complex I activity, and antioxidant supplementation potentiated pulmonary metastatic growth. We confirm lung metastasis-specific NRF2 overexpression in clinical samples, thus validating Flura-seq's utility in identifying clinically actionable microenvironmental adaptations in early metastasis. The sensitivity, robustness and economy of Flura-seq are broadly applicable beyond cancer research. Overall design: Examination of 5-FU labeled RNAs in cancer cells present in different organs
Flura-seq identifies organ-specific metabolic adaptations during early metastatic colonization.
Cell line, Subject
View SamplesHow organ-specific metastatic traits accumulate in primary tumors remains unknown. We identified a role of the primary tumor stroma in selecting breast cancer cells that are primed for metastasis in the bone. A fibroblast-rich stroma in breast tumors creates a microenvironment that is similar to that of bone metastases in its abundance of the cytokines CXCL12 and IGF1. Heterogeneous breast cancer cell populations growing in such mesenchymal environment evolve towards a preponderance of clones that thrive on CXCL12 and IGF1. Fibroblast-driven selection of bone metastatic clones in mammary tumors is suppressed by CXCL12 and IGF1 receptor inhibition. Thus, a fibroblast-rich stroma in breast tumors can pre-select bone metastatic seeds, promoting the evolution of metastatic traits and the interplay between a primary tumor and its distant metastases.
Selection of bone metastasis seeds by mesenchymal signals in the primary tumor stroma.
Specimen part
View SamplesMetastatic relapse of breast cancer and other tumor types usually occurs several years after surgical resection of the primary tumor. Early dissemination of tumor cells followed by an extended period of dormancy is thought to explain this prevalent clinical behavior. By using a gain-of-function retroviral cDNA screen in the mouse, we found that Coco, a secreted antagonist of TGF-beta ligands, induces solitary mammary carcinoma cells that have extravasated in the lung stroma to exit from dormancy. Mechanistic studies demonstrate that Coco awakens dormant metastasis-initiating cells by blocking stroma-derived Bone Morphogenetic Proteins. Inhibition of canonical BMP signaling reverses the commitment to differentiation of these cells and enhances their self-renewal and tumor-initiation capacity. Expression of Coco induces a discrete gene expression signature strongly associated with metastatic relapse to the lung but not to the bone or brain in primary patients samples. Accordi ngly, silencing of Coco does not inhibit metastasis to the bone or brain in mouse models. These findings suggest that metastasis-initiating cells require the self-renewal capability typically associated with stem cells in order to exit from dormancy and identify Coco as a master regulator of this process.
The BMP inhibitor Coco reactivates breast cancer cells at lung metastatic sites.
Cell line
View SamplesCXCL12 and IGF1 are key secreting molecules produced by cancer-associated fibroblasts in breast cancer. These factors promote the survival of disseminated cancer cells in the bone marrow. To assess the combined responses elicited by CXCL12 and IGF1, we examined the translating transcriptome of cancer cells in response to these two factors by Translating Ribosome Affinity Purification (TRAP)-RNAseq. Overall design: MDA-MB-231 cells were engineered to express an EGFP-tagged version of ribosomal protein L10a. This allows the retrieval of polysome-associated mRNA by anti-GFP pull down (TRAP) and profiling the translating transcriptome by RNAseq. EGFP-L10a+ cancer cells were serum starved (0.2% serum) for 24 hours, and then treated with CXCL12 (30ng/mL) + IGF1 (10ng/mL) or CXCL12 (300ng/mL) + IGF1 (100ng/mL) for 6hrs. Two biological replicates were profiled for each condition.
Selection of bone metastasis seeds by mesenchymal signals in the primary tumor stroma.
Cell line, Treatment, Subject
View SamplesGenome-wide analyses have identified thousands of long non-coding RNAs (lncRNAs). Malat1 (Metastasis Associated Lung Adenocarcinoma Transcript 1) is among the most abundant lncRNAs whose expression is altered in numerous cancers. Here we report that genomic loss, as well as systemic knockdown of Malat1 using antisense oligonucleotides, in the MMTV-PyMT mouse mammary carcinoma model results in slower tumor growth accompanied by differentiation into highly cystic tumors and a significant reduction in lung metastasis. Further, Malat1 loss results in a reduction of branching morphogenesis in MMTV-PyMT and Her2/neu amplified tumor organoids consistent with the in vivo reduction in lung metastasis. At the molecular level, Malat1 knockdown results in alterations in gene expression and changes in splicing patterns of genes involved in differentiation and pro-tumorigenic signaling pathways. Together, these data indicate that the lncRNA Malat1 regulates critical processes in mammary cancer pathogenesis and represents a promising therapeutic target for inhibiting breast cancer metastasis. Overall design: Transcriptome profiles of tumors and organoids after Malat1 knockdown using antisense olgonucleotides (ASOs).
Differentiation of mammary tumors and reduction in metastasis upon Malat1 lncRNA loss.
No sample metadata fields
View SamplesCancer metabolism has been actively studied to gain insights into tumorigenic survival mechanisms and susceptibilities. In melanoma, we identify HEXIM1, a transcription elongation regulator, as a novel melanoma suppressor that participates in nucleotide stress regulation. HEXIM1 expression is low in melanoma. Its overexpression suppresses melanoma while its inactivation accelerates tumor onset in vivo. HEXIM1 responds to nucleotide stress. Knockdown of HEXIM1 rescues neural crest and melanoma nucleotide stress phenotypes in vivo. Mechanistically, under nucleotide stress, HEXIM1 is induced to form an inhibitory complex with P-TEFb, the kinase that initiates transcription elongation, to pause transcription at tumorigenic genes. The resulting alteration in gene expression also causes anti-tumorigenic transcripts to bind to and be stabilized by HEXIM1. HEXIM1 therefore plays an important role in inhibiting cancer cell-specific gene transcription while also facilitating anti-cancer gene expression. Our study reveals a novel role for HEXIM1 in coupling nucleotide metabolism with transcriptional regulation in melanoma. Overall design: RNA-seq analysis of human A375 melanoma cells treated with either DMSO or 25 µM A771726 for 0-72 hrs.
Stress from Nucleotide Depletion Activates the Transcriptional Regulator HEXIM1 to Suppress Melanoma.
No sample metadata fields
View SamplesCancer metabolism has been actively studied to gain insights into tumorigenic survival mechanisms and susceptibilities. In melanoma, we identify HEXIM1, a transcription elongation regulator, as a novel melanoma suppressor that participates in nucleotide stress regulation. HEXIM1 expression is low in melanoma. Its overexpression suppresses melanoma while its inactivation accelerates tumor onset in vivo. HEXIM1 responds to nucleotide stress. Knockdown of HEXIM1 rescues neural crest and melanoma nucleotide stress phenotypes in vivo. Mechanistically, under nucleotide stress, HEXIM1 is induced to form an inhibitory complex with P-TEFb, the kinase that initiates transcription elongation, to pause transcription at tumorigenic genes. The resulting alteration in gene expression also causes anti-tumorigenic transcripts to bind to and be stabilized by HEXIM1. HEXIM1 therefore plays an important role in inhibiting cancer cell-specific gene transcription while also facilitating anti-cancer gene expression. Our study reveals a novel role for HEXIM1 in coupling nucleotide metabolism with transcriptional regulation in melanoma. Overall design: RNA-seq analysis of human Tet-On HEXIM1-inducible A375 melanoma cells treated with either DMSO or 1 µg/mL doxycycline in triplicate for 48 hrs.
Stress from Nucleotide Depletion Activates the Transcriptional Regulator HEXIM1 to Suppress Melanoma.
No sample metadata fields
View SamplesAnalysis of estrogen receptor (ER)-positive MCF7 cell total RNA expression and polysome-assiciated RNA expression following treatment with estradiol (E2) and vehicle (etoh).
Estrogen coordinates translation and transcription, revealing a role for NRSF in human breast cancer cells.
Cell line
View SamplesPurpose: The ability to rationally manipulate the transcriptional states of cells would be of great use in medicine and bioengineering. We have developed a novel algorithm, NetSurgeon, which utilizes genome-wide gene regulatory networks to identify interventions that force a cell toward a desired expression state. Results: We used NetSurgeon to select transcription factor deletions aimed at improving ethanol production in S. cerevisiae cultures that are catabolizing xylose. We reasoned that interventions that move the transcriptional states of cells utilizing xylose toward the fermentative state typical of cells that are producing ethanol rapidly (while utilizing glucose) might improve xylose fermentation. Some of the interventions selected by NetSurgeon successfully promoted a fermentative transcriptional state in the absence of glucose, resulting in strains with a 2.7-fold increase in xylose import rates, a 4-fold improvement in xylose integration into central carbon metabolism, or a 1.3-fold increase in ethanol production rate. Conclusions: We conclude by presenting an integrated model of transcriptional regulation and metabolic flux that will enable future metabolic engineering efforts aimed at improving xylose fermentation to prioritize functional regulators of central carbon metabolism. Overall design: Mutant and wildtype S. cerevisiae cells were put into 48 hour aerobic batch fermentations of synthetic complete medium supplmented with 2% glucose and 5% xylose and culture samples were taken at 4 hours and 24 hours for transcriptional profiling performed by RNA-Seq analysis. In addition, wildtype S. cerevisiae cells were grown in various single carbon sources for 12 hours and culture samples were taken for transcriptional profiling performed by RNA-Seq analysis.
Model-based transcriptome engineering promotes a fermentative transcriptional state in yeast.
Subject
View SamplesFew studies have investigated heterogeneity of selection response in replicate lines subjected to equivalent selection. We developed 4 replicate lines of mice based on high levels of voluntary wheel running (high runner or HR lines) while also maintaining 4 non-selected control lines. This led to the unexpected discovery of the HR mini-muscle (HRmini) phenotype, recognized by a 50% reduction in hindlimb muscle mass, which became fixed in 1 of the 4 HR selected lines.
Gene expression profiling of gastrocnemius of "minimuscle" mice.
Sex, Specimen part
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