Christin Ungewiss

Metastasis is regulated via microRNA-200/ZEB1 axis control of tumour cell PD-L1 expression and intratumoral immunosuppression

Immunosuppression of tumor-infiltrating lymphocytes (TIL) is a common feature of advanced cancer, but its biological basis has remained obscure. We demonstrate here a molecular link between epithelial-to-mesenchymal transition (EMT) and CD8+ TIL immunosuppression, two key drivers of cancer progression. We show that microRNA-200 (miR-200), a cell-autonomous suppressor of EMT and metastasis, targets PD-L1. Moreover, ZEB1, an EMT activator and transcriptional repressor of miR-200, relieves miR-200 repression of PD-L1 on tumor cells, leading to CD8+ T cell immunosuppression and metastasis. These findings are supported by robust correlations between the EMT score, miR-200 levels and PD-L1 expression in multiple human lung cancer datasets. In addition to revealing a link between EMT and T cell dysfunction, these findings also show that ZEB1 promotes metastasis through a heretofore unappreciated cell non-autonomous mechanism, and suggest that subgroups of patients in whom malignant progression is driven by EMT activators may respond to treatment with PD-L1 antagonists.

Targets of the tumor suppressor miR-200 in regulation of the epithelial-mesenchymal transition in cancer

The microRNA-200 (miR-200) family restricts epithelial-mesenchymal transition (EMT) and metastasis in tumor cell lines derived from mice that develop metastatic lung adenocarcinoma. To determine the mechanisms responsible for EMT and metastasis regulated by this microRNA, we conducted a global liquid chromatography/tandem mass spectrometry analysis to compare metastatic and nonmetastatic murine lung adenocarcinoma cells which had undergone EMT because of loss of miR-200. An analysis of syngeneic tumors generated by these cells identified multiple novel proteins linked to metastasis. In particular, the analysis of conditioned media, cell surface proteins, and whole-cell lysates from metastatic and nonmetastatic cells revealed large-scale modifications in the tumor microenvironment. Specific increases were documented in extracellular matrix (ECM) proteins, peptidases, and changes in distribution of cell adhesion proteins in the metastatic cell lines. Integrating proteomic data from three subproteomes, we defined constituents of a multilayer protein network that both regulated and mediated the effects of TGFβ. Lastly, we identified ECM proteins and peptidases that were directly regulated by miR-200. Taken together, our results reveal how expression of miR-200 alters the tumor microenvironment to inhibit the processes of EMT and metastasis.

ZEB1 sensitizes lung adenocarcinoma to metastasis suppression by PI3K antagonism

Epithelial tumor cells that have undergone epithelial-to-mesenchymal transition (EMT) are typically prone to metastasis and drug resistance and contribute to a poor clinical outcome. The transcription factor ZEB1 is a known driver of EMT, and mediators of ZEB1 represent potential therapeutic targets for metastasis suppression. Here, we have shown that phosphatidylinositol 3-kinase-targeted (PI3K-targeted) therapy suppresses metastasis in a mouse model of Kras/Tp53-mutant lung adenocarcinoma that develops metastatic disease due to high expression of ZEB1. In lung adenocarcinoma cells from Kras/Tp53-mutant animals and human lung cancer cell lines, ZEB1 activated PI3K by derepressing miR-200 targets, including amphiregulin (AREG), betacellulin (BTC), and the transcription factor GATA6, which stimulated an EGFR/ERBB2 autocrine loop. Additionally, ZEB1-dependent derepression of the miR-200 and miR-183 target friend of GATA 2 (FOG2) enhanced GATA3-induced expression of the p110α catalytic subunit of PI3K. Knockdown of FOG2, p110α, and RHEB ameliorated invasive and metastatic propensities of tumor cells. Surprisingly, FOG2 was not required for mesenchymal differentiation, suggesting that mesenchymal differentiation and invasion are distinct and separable processes. Together, these results indicate that ZEB1 sensitizes lung adenocarcinoma cells to metastasis suppression by PI3K-targeted therapy and suggest that treatments to selectively modify the metastatic behavior of mesenchymal tumor cells are feasible and may be of clinical value.

ZEB1 induces LOXL2-mediated collagen stabilization and deposition in the extracellular matrix to drive lung cancer invasion and metastasis

Lung cancer is the leading cause of cancer-related deaths, primarily due to distant metastatic disease. Metastatic lung cancer cells can undergo an epithelial-to-mesenchymal transition (EMT) regulated by various transcription factors, including a double-negative feedback loop between the microRNA-200 (miR-200) family and ZEB1, but the precise mechanisms by which ZEB1-dependent EMT promotes malignancy remain largely undefined. Although the cell-intrinsic effects of EMT are important for tumor progression, the reciprocal dynamic crosstalk between mesenchymal cancer cells and the extracellular matrix (ECM) is equally critical in regulating invasion and metastasis. Investigating the collaborative effect of EMT and ECM in the metastatic process reveals increased collagen deposition in metastatic tumor tissues as a direct consequence of amplified collagen gene expression in ZEB1-activated mesenchymal lung cancer cells. In addition, collagen fibers in metastatic lung tumors exhibit greater linearity and organization as a result of collagen crosslinking by the lysyl oxidase (LOX) family of enzymes. Expression of the LOX and LOXL2 isoforms is directly regulated by miR-200 and ZEB1, respectively, and their upregulation in metastatic tumors and mesenchymal cell lines is coordinated to that of collagen. Functionally, LOXL2, as opposed to LOX, is the principal isoform that crosslinks and stabilizes insoluble collagen deposition in tumor tissues. In turn, focal adhesion formation and FAK/SRC signaling is activated in mesenchymal tumor cells by crosslinked collagen in the ECM. Our study is the first to validate direct regulation of LOX and LOXL2 by the miR-200/ZEB1 axis, defines a novel mechanism driving tumor metastasis, delineates collagen as a prognostic marker, and identifies LOXL2 as a potential therapeutic target against tumor progression.

The microRNA-200/Zeb1 axis regulates ECM-dependent β1-integrin/FAK signaling, cancer cell invasion and metastasis through CRKL

Tumor cell metastasis is a complex process that has been mechanistically linked to the epithelial-mesenchymal transition (EMT). The double-negative feedback loop between the microRNA-200 family and the Zeb1 transcriptional repressor is a master EMT regulator, but there is incomplete understanding of how miR-200 suppresses invasion. Our recent efforts have focused on the tumor cell-matrix interactions essential to tumor cell activation. Herein we utilized both our Kras/p53 mutant mouse model and human lung cancer cell lines to demonstrate that upon miR-200 loss integrin β1-collagen I interactions drive 3D in vitro migration/invasion and in vivo metastases. Zeb1-dependent EMT enhances tumor cell responsiveness to the ECM composition and activates FAK/Src pathway signaling by de-repression of the direct miR-200 target, CRKL. We demonstrate that CRKL serves as an adaptor molecule to facilitate focal adhesion formation, mediates outside-in signaling through Itgβ1 to drive cell invasion, and inside-out signaling that maintains tumor cell-matrix contacts required for cell invasion. Importantly, CRKL levels in pan-cancer TCGA analyses were predictive of survival and CRKL knockdown suppressed experimental metastases in vivo without affecting primary tumor growth. Our findings highlight the critical ECM-tumor cell interactions regulated by miR-200/Zeb1-dependent EMT that activate intracellular signaling pathways responsible for tumor cell invasion and metastasis.

CD38-mediated immunosuppression as a mechanism of tumor cell escape from PD-1/PD-L1 blockade

Although treatment with immune checkpoint inhibitors provides promising benefit for patients with cancer, optimal use is encumbered by high resistance rates and requires a thorough understanding of resistance mechanisms. We observed that tumors treated with PD-1/PD-L1 blocking antibodies develop resistance through the upregulation of CD38, which is induced by all-trans retinoic acid and IFNβ in the tumor microenvironment. In vitro and in vivo studies demonstrate that CD38 inhibits CD8+ T-cell function via adenosine receptor signaling and that CD38 or adenosine receptor blockade are effective strategies to overcome the resistance. Large data sets of human tumors reveal expression of CD38 in a subset of tumors with high levels of basal or treatment-induced T-cell infiltration, where immune checkpoint therapies are thought to be most effective. These findings provide a novel mechanism of acquired resistance to immune checkpoint therapy and an opportunity to expand their efficacy in cancer treatment.Significance: CD38 is a major mechanism of acquired resistance to PD-1/PD-L1 blockade, causing CD8+ T-cell suppression. Coinhibition of CD38 and PD-L1 improves antitumor immune response. Biomarker assessment in patient cohorts suggests that a combination strategy is applicable to a large percentage of patients in whom PD-1/PD-L1 blockade is currently indicated. Cancer Discov; 8(9); 1156-75. ©2018 AACR.See related commentary by Mittal et al., p. 1066This article is highlighted in the In This Issue feature, p. 1047.

Abstract 567: CD38 blockade overcomes the immune resistance to anti-PD-L1 therapy by boosting CD8 T cell response

Although strategies incorporating immune checkpoint inhibition, e.g. PD-1/PD-L1 blockade, are achieving unprecedented successes and increasingly becoming incorporated into standard of care regimens for cancer patients, high rates of resistance still limit the potential efficacy. Therapeutic improvement requires a thorough understanding of the biological process of resistance. To date there have been few studies reporting mechanisms of resistance to PD-L1 blockade. We have explored the resistance mechanisms to functional PD-L1 loss in preclinical lung cancer models by using pharmacological and genetic approaches (PD-L1 blocking antibody treatment or CRISPR/Cas9-mediated deletion of PD-L1 on tumor cells). The molecular and immune profiles of the tumor microenvironment were evaluated in mutant K-ras/p53 (KP) GEM lung cancer models and multiple immunocompetent syngeneic models (both KP and Lewis lung cancer). Additionally, to determine the applicability of the results to patients with lung cancer, we analyzed 259 patient tumor specimens with IHC staining and evaluated the immune markers in TCGA datasets (adenocarcinoma and squamous) and the MD Anderson PROSPECT dataset. We observed that lung tumors gained resistance to anti-PD-L1 antibody treatment over time, and that the up-regulation of CD38 on tumor cells accounted for the treatment resistance. We also observed the same resistance mechanism caused by CD38 up-regulation in PD-L1 KO mice bearing PD-L1 KO Lewis lung tumors generated with the CRISPR/Cas9 system. Manipulation of CD38 on a panel of lung cancer cell lines, demonstrated that CD38 inhibits CD8+ T cell proliferation, antitumor cytokine secretion, and tumor cell killing capability in vitro and in vivo. Furthermore, to test whether CD38 blockade might be therapeutically efficacious to counter anti-PD-L1 resistance, we applied the combination therapy of anti-CD38 and anti-PD-L1 in lung cancer animal models and demonstrated dramatic therapeutic benefit on primary tumor growth and metastasis. Bioinformatic analyses of the patient tumor databases revealed a strong correlation between CD38 expression and an immune suppressive inflammatory signature. Finally, in 259 lung cancer specimens, 18.5% of cases exhibited positive staining for CD38 on tumor cells. Based upon our studies, we conclude that the up-regulation of CD38 on tumor cells is a major mechanism of resistance to anti-PD-L1 therapy, and that CD38 is a novel immune checkpoint that inhibits CD8+ T cell function. The blockade of CD38 and PD-L1 is a rational combination to prevent immune resistance and increase the response rate for lung cancer patients. Citation Format: Limo Chen, Lixia Diao, Yongbin Yang, Xiaohui Yi, Jaime Rodriguez, Youhong Fan, Leticia Rodriguez, Jared Fradette, Christin Ungewiss, Jonothan Roybal, Jingfen Zhu, Jing Wang, Lauren Byers, Stephen Ullrich, Ignacio Wistuba, John Heymach, Xiao-Feng Qin, Don Gibbons. CD38 blockade overcomes the immune resistance to anti-PD-L1 therapy by boosting CD8 T cell response [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 567. doi:10.1158/1538-7445.AM2017-567

Abstract B67: A big role in tumor immune microenvironment of a small non-coding RNA: microRNA-200

Immunosuppression of tumor-infiltrating lymphocytes (TIL) is a common feature of advanced epithelial tumors, but its biological basis has remained obscure. In addition, anti-PD-1/PD-L1 treatment has produced encouraging clinical responses, but it is still unclear which patients are likely to benefit. Thus, successful therapeutic translation will require a thorough understanding of mechanisms of treatment resistance and predictive biomarkers to select patients. Using multiple lung cancer mouse models (spontaneous and transplant models), we demonstrate a molecular link between epithelial-to-mesenchymal transition (EMT) and intra-tumoral CD8+ T cell immunosuppression, two key drivers of malignant tumor progression. We show that microRNA-200 (miR-200), a cell-autonomous suppressor of EMT and metastasis, targets PD-L1, a checkpoint inhibitor of CD8+ T cell immunity. Moreover, ZEB1, an EMT activator and transcriptional repressor of miR-200, relieves miR-200 repression of PD-L1 on tumor cells, leading to CD8+TIL dysfunction and metastasis. These findings were further supported by robust correlations between the EMT score, miR-200 levels and PD-L1 expression in multiple human lung cancer datasets: The Cancer Genome Atlas (TCGA) lung adenocarcinoma dataset and the Profiling of Resistance patterns and Oncogenic Signaling Pathways in Evaluation of Cancers of the Thorax (PROSPECT) project at MD Anderson Cancer Center. In addition to revealing a link between EMT and T cell dysfunction, these findings also show that ZEB1 promotes metastasis through a heretofore unappreciated cell non-autonomous mechanism, and they suggest that subgroups of patients in whom malignant progression is driven by EMT activators may respond to treatment with PD-L1 antagonists. Our data also suggest that EMT represents an important biomarker to select the patients who may benefit from immune checkpoint blockade agents and other immunotherapies in lung cancer and possibly a broader range of other cancers. Citation Format: Limo Chen, Sangeeta Goswami, Xiaohui Yi, Lauren Byers, Lixia Diao, Jonathon Roybal, Christin Ungewiss, David Peng, Jing Wang, Ignacio Wistuba, Lieping Chen, Stephen Ullrich, John Heymach, Jonathan Kurie, Xiao-Feng Qin, Don Gibbons. A big role in tumor immune microenvironment of a small non-coding RNA: microRNA-200. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B67.

Abstract B44: The microRNA-200/Zeb1 axis regulates ECM-dependent Src signaling, cytoskeletal changes and cancer cell invasion

The microRNA-200 family (miR-200) has been shown to be a master regulator of epithelial-to-mesenchymal transition (EMT), partially through a double-negative feedback loop with the transcription repressor Zeb1, allowing cells to acquire an invasive and metastatic phenotype. Using our mutant Kras and p53 murine model of metastatic lung adenocarcinoma, we are investigating the role of the Zeb1/miR-200 axis in regulating cytoskeletal reorganization, a characteristic requirement of cell motility and invasion. Functional assays demonstrated differential actin reorganization within cell lines with different miR-200 levels based upon the extracellular matrix composition, leading us to hypothesize that miR-200 regulates the activation of signaling pathways that mediate a pro-invasive cytoskeletal reorganization. Based upon the importance of cell-matrix interactions in producing cellular activation we identified the Src pathway as a critical mediator of invasion upon miR-200 repression in murine and human lung cancer cell lines. Pharmacologic inhibition of Src significantly reduces in vitro cell migration and invasion in Boyden chamber assays and in 3D cell cultures, which can be mimicked using Integrin β1 blockade. Biochemical analysis of this Src inhibition reveals a significant reduction in the phosphorylated FAK and cortactin levels, two downstream targets of Src. TGFβ stimulation is a strong EMT inducer, producing miR-200 repression and Src activation in our models, which can be blocked biochemically using Src inhibitors, with associated phenotypic changes in 2D and 3D cultures. This data suggests that miR-200 regulates the cell-matrix contact (e.g. integrins), acting through the Src pathway and modulating central players in actin dynamics to promote actin reorganization and invasion. Citation Format: Christin Ungewiss, Jonathon D. Roybal, David H. Peng, Don L. Gibbons. The microRNA-200/Zeb1 axis regulates ECM-dependent Src signaling, cytoskeletal changes and cancer cell invasion. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B44. doi:10.1158/1538-7445.CHTME14-B44

Abstract C56: microRNA-200 control of tumor cell cytoskeletal changes and invasion

Lung cancer is the leading cause of all cancer-related deaths, accounting for 160,000 deaths per year in the US, primarily caused by metastasis. Understanding the molecular mechanisms leading to metastasis will identify new therapeutic targets for improved treatment strategies. Using our mutant Kras and p53 murine model of metastatic lung adenocarcinoma, we have shown that loss of microRNA-200 family (miR-200) expression is necessary and sufficient to drive an epithelial-to-mesenchymal transition (EMT), allowing cells to acquire an invasive and metastatic phenotype necessary for metastasis. Cell motility is characterized by the reorganization of the actin cytoskeleton, for which we are currently investigating the role of miR-200. Cortactin is a scaffold protein known to play a central role in different signaling pathways involved in the formation of pro-invasive cell structures by recruiting actin-associated proteins and proteases leading to the degradation of the extracellular matrix (ECM). Maturation of cell protrusions requires the phosphorylation of cortactin by upstream tyrosine kinases such as src and arg. Functional assay of cell behavior on 2D agarose demonstrates actin reorganization within our cell lines with different miR-200 levels. Biochemical analysis of cell lines from our model and human lung cancer cells shows that metastatic cells (low-miR-200) have increased levels of phosphorylated cortactin compared to the non-metastatic cells (high miR-200), leading us to hypothesize that miR-200 regulates the biochemical activation of signaling pathways that mediate cortactin phosphorylation and a pro-invasive cytoskeletal reorganization. Inhibition of src using pharmacologic inhibitors and an siRNA approach significantly reduces phosphorylated cortactin levels, inhibits in vitro cell migration and invasion, and decreases the invasiveness of cells grown in 3D, demonstrating the importance of this pathway in invasion. Furthermore, our study demonstrates that the pro-survival PI3K pathway can be inhibited using cortactin siRNA, underlining the multi-faceted role of cortactin in tumor progression. Citation Format: Christin Ungewiss, Jonathon D. Roybal, David H. Peng, Don L. Gibbons. microRNA-200 control of tumor cell cytoskeletal changes and invasion. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr C56.