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PERK signaling through C/EBPδ contributes to ER stress-induced expression of immunomodulatory and tumor promoting chemokines by cancer cells.

ABSTRACT: Expression of the transcription factor CEBPD is induced at early stages of the endoplasmic reticulum (ER) stress response. In order to identify the genes modulated by CEBPD during the ER stress response, we transiently silenced CEBPD expression in MDA-MB-435 melanoma cells and isolated mRNA at 6 h of treatment with Thapsigargin or DMSO control. As control, cells were transfected with two different control siRNA oligonucleotides. Results provide insights into which genes are modulated by CEBPD and/or Thapsigargin in MDA-MB-435 cell

ORGANISM(S): Homo sapiens

PROVIDER: GSE131048 | GEO | 2021/11/01

REPOSITORIES: GEO

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Project description:We previously proposed a clinically meaningful intermediate metastatic state defined by a limited number of new metastases (≤5) after 3 months of follow-up, termed oligometastasis that has the curative potential by local cancer treatments as in contrast to the incurable widespread polymetastatic dissemination. While animal models of polymetastasis exist and this phenotype can be further enhanced upon serial in vivo passage, animal models of oligometastasis are not available. Here, we report the creation of an oligometastasis model of MDA-MB-435 human tumor in nude mice in which the oligometastatic phenotype exhibits stability during successive in vivo testing, and satisfies the criteria of ≤ 5 total body macroscopic metastases definition of the human cancer oligometastatic state. In parallel, we also developed an MDA-MB-435 polymetastatic model in which the polymetastatic dissemination pattern was either poly-foci at lung, or involved multiple anatomic sites including lung, heart, muscle, ovaries, kidney, brain and pleura. We have conducted microRNA expression profiling of cell lines derived from distinct lungs of oligo- and poly-metastatic animals. Animal model-derived microRNA expression features that discriminate oligometastatic cell lines from those of polymetastases accurately identify oligometastatic patients who failed to develop widespread metastases (P=0.005). These results demonstrate the clinical relevance of the oligo- and polymetastatic animal models we have developed and their potential in elucidating the molecular underpinnings of oligometastasis progression. We developed a stable human tumor (MDA-MB-435-GFP) xenograft model of oligometastatic and polymetastatic progression by conducting three consecutive rounds of experimental lung colonization assays. In the first round, we generated oligometastases-like lung derivative MDA-MB-435-L1-GFP (L1) or polymetastases-like MDA-MB-435-L1Mic-GFP (L1Mic) cell lines. We subsequently generated three oligometastatic L1 lung cell lines as well as four polymetastatic L1Mic lung cell lines from seven distinct animals of the second in vivo passage for further biological characterization and for microRNA expression analysis.

Project description:Cancer cells experience endoplasmic reticulum (ER) stress due to activated oncogenes and conditions of nutrient deprivation and hypoxia. The ensuing unfolded protein response (UPR) is executed by ATF6, IRE1 and PERK pathways. Adaptation to mild ER stress promotes tumor cell survival and aggressiveness. Unmitigated ER stress, however, will result in cell death and is a potential avenue for cancer therapies. Because of this yin-yang nature of ER stress, it is imperative that we fully understand the mechanisms and dynamics of the UPR and its contribution to the complexity of tumor biology. The PERK pathway inhibits global protein synthesis while allowing translation of specific mRNAs, such as the ATF4 transcription factor. Using thapsigargin and tunicamycin to induce acute ER stress, we identified the transcription factor C/EBPδ (CEBPD) as a mediator of PERK signaling to secretion of tumor promoting chemokines. In melanoma and breast cancer cell lines, PERK mediated early induction of C/EBPδ through ATF4-independent pathways that involved at least in part Janus kinases and the STAT3 transcription factor. Transcriptional profiling revealed that C/EBPδ contributed to 20% of thapsigargin response genes including chaperones, components of ER-associated degradation, and apoptosis inhibitors. In addition, C/EBPδ supported the expression of the chemokines CXCL8 (IL-8) and CCL20, which are known for their tumor promoting and immunosuppressive properties. With a paradigm of short-term exposure to thapsigargin, which was sufficient to trigger prolonged activation of the UPR in cancer cells, we found that conditioned media from such cells induced cytokine expression in myeloid cells. In addition, activation of the CXCL8 receptor CXCR1 during thapsigargin exposure supported subsequent sphere formation by cancer cells. Taken together, these investigations elucidated a novel mechanism of ER stress-induced transmissible signals in tumor cells that may be particularly relevant in the context of pharmacological interventions.

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PERK signaling through C/EBPδ contributes to ER stress-induced expression of immunomodulatory and tumor promoting chemokines by cancer cells.

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