Drive Cancer Cell Research Articles

Adaptation to TKI Treatment Reactivates ERK Signaling in Tyrosine Kinase-Driven Leukemias and Other Malignancies.

FMS-like tyrosine kinase-3 (FLT3) tyrosine kinase inhibitors (TKI) have been tested extensively to limited benefit in acute myeloid leukemia (AML). We hypothesized that FLT3/internal tandem duplication (ITD) leukemia cells exhibit mechanisms of intrinsic signaling adaptation to TKI treatment that are associated with an incomplete response. Here, we identified reactivation of ERK signaling within hours following treatment of FLT3/ITD AML cells with selective inhibitors of FLT3. When these cells were treated with inhibitors of both FLT3 and MEK in combination, ERK reactivation was abrogated and anti-leukemia effects were more pronounced compared with either drug alone. ERK reactivation was also observed following inhibition of other tyrosine kinase-driven cancer cells, including EGFR-mutant lung cancer, HER2-amplified breast cancer, and BCR-ABL leukemia. These studies reveal an adaptive feedback mechanism in tyrosine kinase-driven cancers associated with reactivation of ERK signaling in response to targeted inhibition. Cancer Res; 77(20); 5554-63. ©2017 AACR.

Hypoxia activates cadherin-22 synthesis via eIF4E2 to drive cancer cell migration, invasion and adhesion.

Hypoxia is a driver of cell movement in processes such as development and tumor progression. The cellular response to hypoxia involves a transcriptional program mediated by hypoxia-inducible factors, but translational control has emerged as a significant contributor. In this study, we demonstrate that a cell-cell adhesion molecule, cadherin-22, is upregulated in hypoxia via mTORC1-independent translational control by the initiation factor eIF4E2. We identify new functions of cadherin-22 as a hypoxia-specific cell-surface molecule involved in cancer cell migration, invasion and adhesion. Silencing eIF4E2 or cadherin-22 significantly impaired MDA-MB-231 breast carcinoma and U87MG glioblastoma cell migration and invasion only in hypoxia, while reintroduction of the respective exogenous gene restored the normal phenotype. Cadherin-22 was evenly distributed throughout spheroids and required for their formation and support of a hypoxic core. Conversely, E-cadherin translation was repressed by hypoxia and only expressed in the oxygenated cells of U87MG spheroids. Furthermore, immunofluorescence on paraffin-embedded human tissue from 40 glioma and 40 invasive ductal breast carcinoma patient specimens revealed that cadherin-22 expression colocalized with areas of hypoxia and significantly correlated with tumor grade and progression-free survival or stage and tumor size, respectively. This study broadens our understanding of tumor progression and metastasis by highlighting cadherin-22 as a potential new target of cancer therapy to disable hypoxic cancer cell motility and adhesion.

The Genes of Life and Death: A Potential Role for Placental-Specific Genes in Cancer: Active retrotransposons in the placenta encode unique functional genes that may also be used by cancer cells to promote malignancy.

The placenta invades the adjacent uterus and controls the maternal immune system, like a cancer invades surrounding organs and suppresses the local immune response. Intriguingly, placental and cancer cells are globally hypomethylated and share an epigenetic phenomenon that is not well understood - they fail to silence repetitive DNA sequences (retrotransposons) that are silenced (methylated) in healthy somatic cells. In the placenta, hypomethylation of retrotransposons has facilitated the evolution of new genes essential for placental function. In cancer, hypomethylation is thought to contribute to activation of oncogenes, genomic instability, and retrotransposon unsilencing; the latter, we postulate, is possibly the most important consequence. Activation of placental retrotransposon-derived genes in cancer underpins our hypothesis that hypomethylation of these genes drives cancer cell invasion. This alludes to an interesting paradox, that while placental retrotransposon-derived genes are essential for promoting early hominid life, the same genes promote disease-susceptibility and death through cancer.

Beyond ALK and ROS1: RET, NTRK, EGFR and BRAF gene rearrangements in non-small cell lung cancer.

The discovery of gene rearrangements involving the receptor tyrosine kinase genes ALK and ROS1 has revolutionized management of the subset of non-small cell lung cancers characterized by these alterations. The oncogenic fusion proteins expressed in these tumors drive cancer cell growth and survival, and targeted inhibition of this signaling can lead to dramatic and durable responses in patients. While the best characterized gene fusions in non-small cell lung cancer (NSCLC) involve ALK and ROS1, fusions involving other kinases including RET, NTRK, EGFR and BRAF are now established as additional targetable drivers. Here we review data supporting the roles of these fusions as oncogenic drivers, and the potential for targeting these fusions for improved clinical outcomes. These discoveries should encourage multiplexed molecular profiling of lung cancers using next-generation platforms which identify these gene fusions in order to expand treatment options for patients.

EZH2 Palmitoylation Mediated by ZDHHC5 in p53-Mutant Glioma Drives Malignant Development and Progression.

Gliomas with mutant p53 occurring in 30% of glioma patients exhibit therapeutic resistance and poor outcomes. In this study, we identify a novel mechanism through which mutant p53 drives cancer cell survival and malignant growth. We documented overexpression of the zinc finger protein ZDHHC5 in glioma compared with normal brain tissue and that this event tightly correlated with p53 mutations. Mechanistic investigations revealed that mutant p53 transcriptionally upregulated ZDHHC5 along with the nuclear transcription factor NF-Y. These events contributed to the development of glioma by promoting the self-renewal capacity and tumorigenicity of glioma stem-like cells, by altering the palmitoylation and phosphorylation status of the tumor suppressor EZH2. Taken together, our work highlighted ZDHHC5 as a candidate therapeutic target for management of p53-mutated gliomas. Cancer Res; 77(18); 4998-5010. ©2017 AACR.

The protein restriction mimetic Resveratrol is an autophagy inducer stronger than amino acid starvation in ovarian cancer cells.

The potential benefit of nutrient starvation in the prevention and treatment of cancer is presently under consideration. Resveratrol (RV), a dietary polyphenol acting as a protein (caloric) restriction mimetic, could substitute for amino acid starvation. The effects of starvation and of caloric restriction are mediated, among others, by autophagy, a process that contributes to cell homeostasis by promoting the lysosomal degradation of damaged and redundant self-constituents. Up-regulation of autophagy favors cell survival under nutrient shortage situation, and may drive cancer cells into a non-replicative, dormant state. Both RV and amino acid starvation effectively induced the aminoacid response and autophagy. These processes were associated with inhibition of the mTOR pathway and disruption of the BECLIN1-BCL-2 complex. The number of transcripts positively impinging on the autophagy pathway was higher in RV-treated than in starved cancer cells. Consistent with our data, it appears that RV treatment is more effective than and can substitute for starvation for inducing autophagy in cancer cells. The present findings are clinically relevant because of the potential therapeutic implications.

EMT: Mechanisms and therapeutic implications.

Metastasis, the dissemination of cancer cells from primary tumors, represents a major hurdle in the treatment of cancer. The epithelial-mesenchymal transition (EMT) has been studied in normal mammalian development for decades, and it has been proposed as a critical mechanism during cancer progression and metastasis. EMT is tightly regulated by several internal and external cues that orchestrate the shifting from an epithelial-like phenotype into a mesenchymal phenotype, relying on a delicate balance between these two stages to promote metastatic development. EMT is thought to be induced in a subset of metastatic cancer stem cells (MCSCs), bestowing this population with the ability to spread throughout the body and contributing to therapy resistance. The EMT pathway is of increasing interest as a novel therapeutic avenue in the treatment of cancer, and could be targeted to prevent tumor cell dissemination in early stage patients or to eradicate existing metastatic cells in advanced stages. In this review, we describe the sequence of events and defining mechanisms that take place during EMT, and how these interactions drive cancer cell progression into metastasis. We summarize clinical interventions focused on targeting various aspects of EMT and their contribution to preventing cancer dissemination.

IGF2 mRNA binding protein-2 is a tumor promoter that drives cancer proliferation through its client mRNAs IGF2 and HMGA1.

The gene encoding the Insulin-like Growth Factor 2 mRNA binding protein 2/IMP2 is amplified and overexpressed in many human cancers, accompanied by a poorer prognosis. Mice lacking IMP2 exhibit a longer lifespan and a reduced tumor burden at old age. Herein we show in a diverse array of human cancer cells that IMP2 overexpression stimulates and IMP2 elimination diminishes proliferation by 50-80%. In addition to its known ability to promote the abundance of Insulin-like Growth Factor 2/IGF2, we find that IMP2 strongly promotes IGF action, by binding and stabilizing the mRNA encoding the DNA binding protein HMGA1, a known oncogene. HMGA1 suppresses the abundance of IGF binding protein 2/IGFBP2 and Grb14, inhibitors of IGF action. IMP2 stabilization of HMGA1 mRNA plus IMP2 stimulated IGF2 production synergistically drive cancer cell proliferation and account for IMP2's tumor promoting action. IMP2's ability to promote proliferation and IGF action requires IMP2 phosphorylation by mTOR.

Actomyosin drives cancer cell nuclear dysmorphia and threatens genome stability

Altered nuclear shape is a defining feature of cancer cells. The mechanisms underlying nuclear dysmorphia in cancer remain poorly understood. Here we identify PPP1R12A and PPP1CB, two subunits of the myosin phosphatase complex that antagonizes actomyosin contractility, as proteins safeguarding nuclear integrity. Loss of PPP1R12A or PPP1CB causes nuclear fragmentation, nuclear envelope rupture, nuclear compartment breakdown and genome instability. Pharmacological or genetic inhibition of actomyosin contractility restores nuclear architecture and genome integrity in cells lacking PPP1R12A or PPP1CB. We detect actin filaments at nuclear envelope rupture sites and define the Rho-ROCK pathway as the driver of nuclear damage. Lamin A protects nuclei from the impact of actomyosin activity. Blocking contractility increases nuclear circularity in cultured cancer cells and suppresses deformations of xenograft nuclei in vivo. We conclude that actomyosin contractility is a major determinant of nuclear shape and that unrestrained contractility causes nuclear dysmorphia, nuclear envelope rupture and genome instability.

RBM38 is involved in TGF-\u03b2-induced epithelial-to-mesenchymal transition by stabilising zonula occludens-1 mRNA in breast cancer

Background:The transforming growth factor-β (TGF-β) pathway plays a vital role in driving cancer cell epithelial–mesenchymal transition (EMT). Zonula occludens-1 (ZO-1), which is downregulated in response to TGF-β, is able to control endothelial cell–cell tension, cell migration, and barrier formation. However, the molecular mechanism of how TGF-β regulates ZO-1 expression remains unclear.Methods:Breast cancer cells were treated with TGF-β to induce an EMT progress. Chromatin immunoprecipitation and dual-luciferase reporter assay were performed to investigate direct relationship between Snail and RNA binding motif protein 38 (RBM38). The RNA immunoprecipitation combined with RNA electrophoretic mobility shift assay and dual-luciferase reporter assay were conducted to testify direct relationship between RBM38 and ZO-1. The ZO-1 siRNA was transfected to breast cancer cells that overexpress RBM38 and the control, followed by transwell and Matrigel invasion assays to examine cell migratory and invasive ability.Results:Transforming growth factor-β induced a remarkable downregulation of RBM38 in breast cancer that was directly regulated by transcription repressor Snail targeting the E-box elements in promoter region of RBM38 gene. Additionally, RBM38 positively regulated ZO-1 transcript via directly binding to AU/U-rich elements in its mRNA 3′-UTR. Moreover, by magnifying RBM38 expression, cell migration and invasion mediated by knockdown of ZO-1 in breast cancer were reversed.Conclusions:All the results clarified a linear regulation relationship among Snail, RBM38, and ZO-1, implicating RBM38 as a pivotal mediator in TGF-β-induced EMT in breast cancer.

Abstract 1222: Developing kinase inhibitors with polypharmacological profiles for the treatment of resistant cancers

Abstract Small molecule kinase inhibitors targeting a specific oncoprotein driving cancer cells have shown great clinical success in the past (e.g. imatinib against leukemia). However, resistance to targeted therapies quickly arises due to plasticity associated with cancer cell signaling and tumor heterogeneity. One way to overcome this problem is to rationally design drugs with polypharmacology that can target multiple signaling pathways engaging in cancer cell proliferation and survival. To this end, we have developed a strategy based on combining phenotypic screens of small molecule inhibitors and affinity-based mass spectrometry to identify drugs with multi-targeted properties and piloted this approach using the highly resistant KRAS mutant non-small cell lung cancer cell lines. We began this study by screening kinase inhibitors targeting MEK, ERK, PI3K, Akt and mTOR and found that the lung cancer cells were largely resistant to single drugs but showed enhanced sensitivity towards triple inhibition of MEK, ERK and PI3K. These cell lines were then screened with a library of covalent and non-covalent kinase inhibitors in an attempt to identify a small molecule inhibitor that could mimic the activity of the triple drug combination. This led to the discovery of SM1-71 that not only recapitulated the growth inhibitory activity of MEK+ERK+PI3K inhibition, but also blocked phosphorylation of ERK, Akt, mTOR and S6K in cells. Target profiling of the drug was carried out using chemoproteomics, which revealed that SM1-71 inhibited 55 kinases at a 1μM concentration. Dose-dependent evaluation further determined the IC50 of inhibition across the 55 kinases and rank ordered them based on binding affinity. Top hits including MEK1, MEK2, ERK1, ERK2, AURKA, SRC and RPS6KA3 were confirmed using alternate kinase screens and cellular assays. Growth factor receptors such as IGF1R, MET and EGFR were also identified and further validated using cell-based assays. Taken together, these results elucidated the polypharmacology associated with SM1-71 and uncovered key targets responsible for inducing strong cytotoxicity in KRAS mutant lung cancer cells. Through the combination of phenotypic screens and mass spectrometry-based target identification, we have demonstrated the proof of principle for developing kinase inhibitors with polypharmacology targeting resistant cancers. Citation Format: Suman Rao, Tan Li, Robert Everley, Guangyan Du, Peter Sorger, Nathanael Gray. Developing kinase inhibitors with polypharmacological profiles for the treatment of resistant cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1222. doi:10.1158/1538-7445.AM2017-1222

Abstract 5830: A novel Notch-YAP circuit drives stemness and tumorigenesis in embryonal rhabdomyosarcoma

Abstract Introduction: Rhabdomyosarcoma (RMS), a tumor characterized by skeletal muscle features, is the most common soft tissue sarcoma in children and adolescents. The standard of care treatment has not changed in over 40 years, resulting in a stagnant survival rate of less than 30% for high risk groups. Previous studies have identified the developmental pathways Notch and YAP as potent oncogenic signals in the embryonal subtype of RMS (eRMS). Understanding the signaling between Notch and YAP in cancers driven by these pathways, such as eRMS, will be crucial to designing rational combination therapies. Experimental Procedures: For in vitro assays, we utilized 3D sphere cell culture methods that permit the study of stem cell behavior. To analyze signaling, we performed genetic gain and loss-of-function (dox-inducible shRNAs and constitutively active constructs), and pharmacologic inhibition. Target validation was assessed by qPCR and immunoblot, and mechanism was determined by ChIP and limiting dilution assays. For in vivo experiments, we performed subcutaneous xenografts in immunocompromised mice. Immunohistochemistry was used to analyze protein expression in human and murine tumors. Statistical analysis was performed to assess significant differences. Results: We have discovered a novel Notch-YAP circuit that drives cancer cell stemness and tumorigenesis. In eRMS 3D spheres, Notch transcriptionally upregulates YAP and increases its activity, while YAP transcriptionally upregulates the Notch ligands JAG1 and DLL1 and the core Notch transcription factor RBPJ to provide positive feedback. In vivo, YAP suppression decreases Notch signaling, stemness, and proliferation. This circuit boosts expression of the stem cell gene SOX2, which is functionally required for eRMS cell stemness. Inhibiting one node of the circuit, for example through Notch pharmacologic blockade, is not sufficient to shut down the circuit, as stemness and cell growth can be rescued by ectopic YAP. Rather, dual inhibition of Notch and YAP is necessary to silence the circuit’s signaling and sphere growth. Importantly, nuclear Notch and YAP protein expression correlate in eRMS patient tumor samples, suggesting this circuit is intact in human eRMS tumors. Conclusions: While unidirectional signaling between these two pathways has been reported in metazoan development and rarely in human malignancy, this is the first finding of an intact bidirectional circuit between Notch and YAP that supports cancer cell stemness and tumorigenesis. This study provides mechanistic insight into the long-standing question of how eRMS cancer stem cells maintain plasticity. Additionally, while this signaling is identified here in RMS, it could be applicable to many cancer types that are Notch and YAP-dependent. Lastly, this work provides evidence and rationale for research into combination therapies targeting this Notch-YAP signaling circuit. Citation Format: Katherine K. Slemmons, Lisa E.S. Crose, Stefan Riedel, Manuela Sushnitha, Brian Belyea, Corinne M. Linardic. A novel Notch-YAP circuit drives stemness and tumorigenesis in embryonal rhabdomyosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5830. doi:10.1158/1538-7445.AM2017-5830

Abstract 1365: Sensitivity of oncogenic KRAS to adenosine triphosphate suppression

Abstract KRAS proteins regulate many cellular processes including initiation of cell division in response to mitogens. Gain of function KRAS mutations appear in approximately 30% of all human cancers and activate effector signal transduction pathways independent of mitogenic stimuli. KRAS driven cancers also frequently have high metabolic rates and may have increased sensitivity to metabolic inhibitors but the underlying mechanism is not fully understood. In this study, we characterized the cellular mechanism of a small molecule inhibitor identified using a transgenic Drosophila melanogaster model that expresses human KRAS-G12V in the fly wing. The compound partially restored wing development in the KRAS-G12V flies and inhibited growth and signal transduction in multiple KRAS driven cancer cells and KRAS-G12V dependent MEF cells but not in MEF cells expressing BRAF-V600E. The compound also had a profound impact on mitochondrial function by inhibiting electron transport (ETC) complex I. Multiple other ETC or ATP synthase inhibitors similarly impaired oncogenic KRAS signal transduction. ATP production through glucose metabolism was sufficient to rescue KRAS function and cellular growth after ETC inhibition, suggesting that inhibition of MAPK signaling is due to low ATP levels rather than a direct consequence of ETC or complex I inhibition. These data indicate that oncogenic KRAS signal transduction requires high cellular ATP levels and suggests a synthetic lethal interaction between KRAS and multiple metabolic targets that could be exploited to target KRAS driven cancers. Citation Format: Matthew Holderfield, Kanika Sharma. Sensitivity of oncogenic KRAS to adenosine triphosphate suppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1365. doi:10.1158/1538-7445.AM2017-1365

A Transcriptional Program for Detecting TGFβ-Induced EMT in Cancer.

Most cancer deaths are due to metastasis, and epithelial-to-mesenchymal transition (EMT) plays a central role in driving cancer cell metastasis. EMT is induced by different stimuli, leading to different signaling patterns and therapeutic responses. TGFβ is one of the best-studied drivers of EMT, and many drugs are available to target this signaling pathway. A comprehensive bioinformatics approach was employed to derive a signature for TGFβ-induced EMT which can be used to score TGFβ-driven EMT in cells and clinical specimens. Considering this signature in pan-cancer cell and tumor datasets, a number of cell lines (including basal B breast cancer and cancers of the central nervous system) show evidence for TGFβ-driven EMT and carry a low mutational burden across the TGFβ signaling pathway. Furthermore, significant variation is observed in the response of high scoring cell lines to some common cancer drugs. Finally, this signature was applied to pan-cancer data from The Cancer Genome Atlas to identify tumor types with evidence of TGFβ-induced EMT. Tumor types with high scores showed significantly lower survival rates than those with low scores and also carry a lower mutational burden in the TGFβ pathway. The current transcriptomic signature demonstrates reproducible results across independent cell line and cancer datasets and identifies samples with strong mesenchymal phenotypes likely to be driven by TGFβ.Implications: The TGFβ-induced EMT signature may be useful to identify patients with mesenchymal-like tumors who could benefit from targeted therapeutics to inhibit promesenchymal TGFβ signaling and disrupt the metastatic cascade. Mol Cancer Res; 15(5); 619-31. ©2017 AACR.

Investigation of the structural requirements of K-Ras(G12D) selective inhibitory peptide KRpep-2d using alanine scans and cysteine bridging

A structure-activity relationship study of a K-Ras(G12D) selective inhibitory cyclic peptide, KRpep-2d was performed. Alanine scanning of KRpep-2d focusing on the cyclic moiety showed that Leu7, Ile9, and Asp12 are the key elements for K-Ras(G12D) selective inhibition of KRpep-2d. The cysteine bridging was also examined to identify the stable analog of KRpep-2d under reductive conditions. As a result, the KRpep-2d analog (12) including mono-methylene bridging showed potent K-Ras(G12D) selective inhibition in both the presence and the absence of dithiothreitol. This means that mono-methylene bridging is an effective strategy to obtain a reduction-resistance analog of parent disulfide cyclic peptides. Peptide 12 inhibited proliferation of K-Ras(G12D)-driven cancer cells significantly. These results gave valuable information for further optimization of KRpep-2d to provide novel anti-cancer drug candidates targeting the K-Ras(G12D) mutant.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Abstract A25: Sensing stress in cancer: a novel therapy targeting protein synthesis through the unfolded protein response in prostate cancer development

Abstract Distinct oncogenic lesions within components of the Myc or PI3K pathways hijack the translation machinery, to establish an aberrant “cancer proteome”, that drives cancer cell growth and tumor development. Invariably, however, increases in the protein synthesis capacity of cancer cells impose a cellular stress that requires an adaptive or evasive response in order for cancer cells to survive and continue proliferating. One of the key cytoprotective stress response pathways is known as the unfolded protein response (UPR), which is engaged when an excess of unfolded/misfolded proteins accumulate within the lumen of the endoplasmic reticulum. How the specific arms of UPR are coupled to increased protein synthesis in cancer etiology and drug response is still poorly understood. In this study we established a new genetic mouse model to address the role of protein synthesis-dependent activation of the UPR in prostate cancer initiation and maintenance promoted by loss of the PTEN tumor suppressor and overexpression of the Myc oncogene. We show that in this epithelial cancer model, Myc hyperactivation and PTEN loss synergize to dramatically stimulate PERK and IRE-1α activity, two major signaling arms of the UPR pathway. Distinct mechanisms transduce adaptive signals under conditions of ER stress: PERK control of protein synthesis through phosphorylation of the key translation initiation factor eIF2α and IRE1α-mediated splicing of the XBP-1 mRNA to produce an active and stable XBP1 transcription factor (XBP1s). Importantly, we observed that UPR activation is associated with formation of prostatic intraepithelial neoplasia (PIN) and invasive carcinoma. Strikingly, the pharmacologic inhibition of eIF2α phosphorylation leads to tumor inhibition. We have further established patient derived xenograft (PDX) models from primary and metastatic human prostate tumors to extend the role of UPR in specific steps of human tumor development. We have also developed a series of novel mouse and human prostate cancer cell culture systems to define the role of localized translation of ER-associated ribosomes during oncogenic transformation. Together this work provides critical insight into a fundamental mechanism by which the augmented protein synthesis requirement of cancer cells is coupled to an adaptation of ER cellular stress, reflecting a new cancer-specific vulnerability that is targetable. Citation Format: Crystal S. Conn, Hao G. Nguyen, Yae Kye, John T. Cunningham, Charles Truillet, Michael Evans, Tony L. Huynh, Peter Walters, Davide Ruggero. Sensing stress in cancer: a novel therapy targeting protein synthesis through the unfolded protein response in prostate cancer development. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr A25.

Correction: Nur77 deficiency in mice accelerates tumor invasion and metastasis by facilitating TNFα secretion and lowering CSF-1R expression.

[This corrects the article DOI: 10.1371/journal.pone.0171347.].

Nur77 deficiency in mice accelerates tumor invasion and metastasis by facilitating TNFα secretion and lowering CSF-1R expression.

Nur77, an orphan member of the nuclear receptor superfamily, plays critical roles in inflammation and immunity. However, the role of Nur77 in tumor microenvironment remains elusive. Results showed that deletion of Nur77 strikingly enhanced tumor metastasis compared to WT mice. Additionally, compared to the conditioned media derived from Nur77+/+ peritoneal macrophages (CM1), the conditioned media derived from Nur77-/- peritoneal macrophages (CM2) significantly promoted the EMT of cancer cells, and greatly enhanced the migratory and invasive abilities of cancer cells. Moreover, studies using TNF-α blocking antibody demonstrated that pro-inflammatory cytokine TNF-α was indispensable in supporting CM2-induced EMT to drive cancer cells migration and invasion. Furthermore, we found that Nur77 promoted the expression of CSF-1R, a novel downstream target gene of Nur77, and subsequently enhanced the migration of inflammatory cells. Notably, infiltration of inflammatory cells in the tumors of Nur77-/- mice was markedly abrogated compared to Nur77+/+ mice. Collectively, these results revealed that host Nur77 expression was pivotal in antitumor immune response, and in inhibiting tumor metastasis.

Fluid shear stress activates YAP1 to promote cancer cell motility

Mechanical stress is pervasive in egress routes of malignancy, yet the intrinsic effects of force on tumour cells remain poorly understood. Here, we demonstrate that frictional force characteristic of flow in the lymphatics stimulates YAP1 to drive cancer cell migration; whereas intensities of fluid wall shear stress (WSS) typical of venous or arterial flow inhibit taxis. YAP1, but not TAZ, is strictly required for WSS-enhanced cell movement, as blockade of YAP1, TEAD1-4 or the YAP1–TEAD interaction reduces cellular velocity to levels observed without flow. Silencing of TEAD phenocopies loss of YAP1, implicating transcriptional transactivation function in mediating force-enhanced cell migration. WSS dictates expression of a network of YAP1 effectors with executive roles in invasion, chemotaxis and adhesion downstream of the ROCK–LIMK–cofilin signalling axis. Altogether, these data implicate YAP1 as a fluid mechanosensor that functions to regulate genes that promote metastasis.