ABSTRACT
Metastasis-initiating cells (MICs) display stem cell-like features, cause metastatic recurrences and defy chemotherapy, which leads to patients' demise. Here we show that prostate and breast cancer patients harbor contingents of tumor cells with high expression of CX3CR1, OCT4a (POU5F1), and NANOG. Impairing CX3CR1 expression or signaling hampered the formation of tumor spheroids by cell lines from which we isolated small subsets co-expressing CX3CR1 and stemness-related markers, similarly to patients' tumors. These rare CX3CR1High cells show transcriptomic profiles enriched in pathways that regulate pluripotency and endowed with metastasis-initiating behavior in murine models. Cancer cells lacking these features (CX3CR1Low) were capable of re-acquiring CX3CR1-associated features over time, implying that MICs can continuously emerge from non-stem cancer cells. CX3CR1 expression also conferred resistance to docetaxel, and prolonged treatment with docetaxel selected CX3CR1High phenotypes with de-enriched transcriptomic profiles for apoptotic pathways. These findings nominate CX3CR1 as a novel marker of stem-like tumor cells and provide conceptual ground for future development of approaches targeting CX3CR1 signaling and (re)expression as therapeutic means to prevent or contain metastasis initiation.
Subject(s)
Octamer Transcription Factor-3ABSTRACT
The retinoblastoma tumor suppressor (RB) is a critical regulator of E2F-dependent transcription, controlling a multitude of protumorigenic networks including but not limited to cell-cycle control. Here, genome-wide assessment of E2F1 function after RB loss in isogenic models of prostate cancer revealed unexpected repositioning and cooperation with oncogenic transcription factors, including the major driver of disease progression, the androgen receptor (AR). Further investigation revealed that observed AR/E2F1 cooperation elicited novel transcriptional networks that promote cancer phenotypes, especially as related to evasion of cell death. These observations were reflected in assessment of human disease, indicating the clinical relevance of the AR/E2F1 cooperome in prostate cancer. Together, these studies reveal new mechanisms by which RB loss induces cancer progression and highlight the importance of understanding the targets of E2F1 function. SIGNIFICANCE: This study identifies that RB loss in prostate cancer drives cooperation between AR and E2F1 as coregulators of transcription, which is linked to the progression of advanced disease.
Subject(s)
Carcinogenesis/genetics , E2F1 Transcription Factor/metabolism , Oncogene Proteins/metabolism , Prostatic Neoplasms/metabolism , Receptors, Androgen/metabolism , Retinoblastoma Binding Proteins/metabolism , Signal Transduction/genetics , Ubiquitin-Protein Ligases/metabolism , Apoptosis/genetics , Binding Sites , Cell Line, Tumor , Cell Survival/genetics , Cohort Studies , E2F1 Transcription Factor/genetics , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Humans , Male , Oncogene Proteins/genetics , Oncogenes , Prostatic Neoplasms/pathology , Protein Binding/genetics , Retinoblastoma Binding Proteins/genetics , Transfection , Ubiquitin-Protein Ligases/geneticsABSTRACT
Mechanisms regulating DNA repair processes remain incompletely defined. Here, the circadian factor CRY1, an evolutionally conserved transcriptional coregulator, is identified as a tumor specific regulator of DNA repair. Key findings demonstrate that CRY1 expression is androgen-responsive and associates with poor outcome in prostate cancer. Functional studies and first-in-field mapping of the CRY1 cistrome and transcriptome reveal that CRY1 regulates DNA repair and the G2/M transition. DNA damage stabilizes CRY1 in cancer (in vitro, in vivo, and human tumors ex vivo), which proves critical for efficient DNA repair. Further mechanistic investigation shows that stabilized CRY1 temporally regulates expression of genes required for homologous recombination. Collectively, these findings reveal that CRY1 is hormone-induced in tumors, is further stabilized by genomic insult, and promotes DNA repair and cell survival through temporal transcriptional regulation. These studies identify the circadian factor CRY1 as pro-tumorigenic and nominate CRY1 as a new therapeutic target.
Subject(s)
Carcinogenesis/genetics , Cryptochromes/metabolism , Gene Expression Regulation, Neoplastic , Prostatic Neoplasms, Castration-Resistant/genetics , Recombinational DNA Repair/genetics , Aged , Androgen Receptor Antagonists/pharmacology , Androgen Receptor Antagonists/therapeutic use , Androgens/metabolism , Carcinogenesis/drug effects , Cell Line, Tumor , Chromatin Immunoprecipitation Sequencing , Cryptochromes/genetics , DNA Breaks, Double-Stranded/drug effects , Datasets as Topic , Disease Progression , Follow-Up Studies , G2 Phase Cell Cycle Checkpoints/genetics , Humans , Male , Middle Aged , Neoplasm Grading , Promoter Regions, Genetic/genetics , Prospective Studies , Prostate/pathology , Prostate/surgery , Prostatectomy , Prostatic Neoplasms, Castration-Resistant/mortality , Prostatic Neoplasms, Castration-Resistant/pathology , Prostatic Neoplasms, Castration-Resistant/therapy , RNA-Seq , Receptors, Androgen/metabolism , Recombinational DNA Repair/drug effects , Retrospective StudiesABSTRACT
RB loss occurs commonly in neoplasia but its contributions to advanced cancer have not been assessed directly. Here we show that RB loss in multiple murine models of cancer produces a prometastatic phenotype. Gene expression analyses showed that regulation of the cell motility receptor RHAMM by the RB/E2F pathway was critical for epithelial-mesenchymal transition, motility, and invasion by cancer cells. Genetic modulation or pharmacologic inhibition of RHAMM activity was sufficient and necessary for metastatic phenotypes induced by RB loss in prostate cancer. Mechanistic studies in this setting established that RHAMM stabilized F-actin polymerization by controlling ROCK signaling. Collectively, our findings show how RB loss drives metastatic capacity and highlight RHAMM as a candidate therapeutic target for treating advanced prostate cancer. Cancer Res; 77(4); 982-95. ©2016 AACR.
