Melanoma adapts to RAF/MEK inhibitors through FOXD3-mediated upregulation of ERBB3

• Text
• PDF

Abstract

The mechanisms underlying adaptive resistance of melanoma to targeted therapies remain unclear. By combining ChIP sequencing with microarray-based gene profiling, we determined that ERBB3 is upregulated by FOXD3, a transcription factor that promotes resistance to RAF inhibitors in melanoma. Enhanced ERBB3 signaling promoted resistance to RAF pathway inhibitors in cultured melanoma cell lines and in mouse xenograft models. ERBB3 signaling was dependent on ERBB2; targeting ERBB2 with lapatinib in combination with the RAF inhibitor PLX4720 reduced tumor burden and extended latency of tumor regrowth in vivo versus PLX4720 alone. These results suggest that enhanced ERBB3 signaling may serve as a mechanism of adaptive resistance to RAF and MEK inhibitors in melanoma and that cotargeting this pathway may enhance the clinical efficacy and extend the therapeutic duration of RAF inhibitors.

Authors

Ethan V. Abel, Kevin J. Basile, Curtis H. Kugel III, Agnieszka K. Witkiewicz, Kaitlyn Le, Ravi K. Amaravadi, Giorgos C. Karakousis, Xiaowei Xu, Wei Xu, Lynn M. Schuchter, Jason B. Lee, Adam Ertel, Paolo Fortina, Andrew E. Aplin

Cooperativity of imprinted genes inactivated by acquired chromosome 20q deletions

• Text
• PDF

Abstract

Large regions of recurrent genomic loss are common in cancers; however, with a few well-characterized exceptions, how they contribute to tumor pathogenesis remains largely obscure. Here we identified primate-restricted imprinting of a gene cluster on chromosome 20 in the region commonly deleted in chronic myeloid malignancies. We showed that a single heterozygous 20q deletion consistently resulted in the complete loss of expression of the imprinted genes L3MBTL1 and SGK2, indicative of a pathogenetic role for loss of the active paternally inherited locus. Concomitant loss of both L3MBTL1 and SGK2 dysregulated erythropoiesis and megakaryopoiesis, 2 lineages commonly affected in chronic myeloid malignancies, with distinct consequences in each lineage. We demonstrated that L3MBTL1 and SGK2 collaborated in the transcriptional regulation of MYC by influencing different aspects of chromatin structure. L3MBTL1 is known to regulate nucleosomal compaction, and we here showed that SGK2 inactivated BRG1, a key ATP-dependent helicase within the SWI/SNF complex that regulates nucleosomal positioning. These results demonstrate a link between an imprinted gene cluster and malignancy, reveal a new pathogenetic mechanism associated with acquired regions of genomic loss, and underline the complex molecular and cellular consequences of “simple” cancer-associated chromosome deletions.

Authors

Athar Aziz, E. Joanna Baxter, Carol Edwards, Clara Yujing Cheong, Mitsuteru Ito, Anthony Bench, Rebecca Kelley, Yvonne Silber, Philip A. Beer, Keefe Chng, Marilyn B. Renfree, Kirsten McEwen, Dionne Gray, Jyoti Nangalia, Ghulam J. Mufti, Eva Hellstrom-Lindberg, Jean-Jacques Kiladjian, Mary Frances McMullin, Peter J. Campbell, Anne C. Ferguson-Smith, Anthony R. Green

Tumor fibroblast–derived epiregulin promotes growth of colitis-associated neoplasms through ERK

• Text
• PDF

Abstract

Molecular mechanisms specific to colitis-associated cancers have been poorly characterized. Using comparative whole-genome expression profiling, we observed differential expression of epiregulin (EREG) in mouse models of colitis-associated, but not sporadic, colorectal cancer. Similarly, EREG expression was significantly upregulated in cohorts of patients with colitis-associated cancer. Furthermore, tumor-associated fibroblasts were identified as a major source of EREG in colitis-associated neoplasms. Functional studies showed that Ereg-deficient mice, although more prone to colitis, were strongly protected from colitis-associated tumors. Serial endoscopic studies revealed that EREG promoted tumor growth rather than initiation. Additionally, we demonstrated that fibroblast-derived EREG requires ERK activation to induce proliferation of intestinal epithelial cells (IEC) and tumor development in vivo. To demonstrate the functional relevance of EREG-producing tumor-associated fibroblasts, we developed a novel system for adoptive transfer of these cells via mini-endoscopic local injection. It was found that transfer of EREG-producing, but not Ereg-deficient, fibroblasts from tumors significantly augmented growth of colitis-associated neoplasms in vivo. In conclusion, our data indicate that EREG and tumor-associated fibroblasts play a crucial role in controlling tumor growth in colitis-associated neoplasms.

Authors

Clemens Neufert, Christoph Becker, Özlem Türeci, Maximilian J. Waldner, Ingo Backert, Katharina Floh, Imke Atreya, Moritz Leppkes, Andre Jefremow, Michael Vieth, Regine Schneider-Stock, Patricia Klinger, Florian R. Greten, David W. Threadgill, Ugur Sahin, Markus F. Neurath

Autocrine production of IL-11 mediates tumorigenicity in hypoxic cancer cells

• Text
• PDF

Abstract

IL-11 and its receptor, IL-11Ra, are expressed in human cancers; however, the functional role of IL-11 in tumor progression is not known. We found that IL11 is a hypoxia-inducible, VHL-regulated gene in human cancer cells and that expression of IL11 mRNA was dependent, at least in part, on HIF-1. A cooperative interaction between HIF-1 and AP-1 mediated transcriptional activation of the IL11 promoter. Additionally, we found that human cancer cells expressed a functional IL-11Ra subunit, which triggered signal transduction either by exogenous recombinant human IL-11 or by autocrine production of IL-11 in cells cultured under hypoxic conditions. Silencing of IL11 dramatically abrogated the ability of hypoxia to increase anchorage-independent growth and significantly reduced tumor growth in xenograft models. Notably, these results were phenocopied by partial knockdown of STAT1 in a human prostate cancer cell line (PC3), suggesting that this pathway may play an important role in mediating the effects of IL-11 under hypoxic conditions. In conclusion, these results identify IL11 as an oxygen- and VHL-regulated gene and provide evidence of a pathway “hijacked” by hypoxic cancer cells that may contribute to tumor progression.

Authors

Barbara Onnis, Nicole Fer, Annamaria Rapisarda, Victor S. Perez, Giovanni Melillo

Formylpeptide receptor-2 contributes to colonic epithelial homeostasis, inflammation, and tumorigenesis

• Text
• PDF

Abstract

Commensal bacteria and their products provide beneficial effects to the mammalian gut by stimulating epithelial cell turnover and enhancing wound healing, without activating overt inflammation. We hypothesized that N-formylpeptide receptors, which bind bacterial N-formylpeptides and are expressed by intestinal epithelial cells, may contribute to these processes. Here we report that formylpeptide receptor-2 (FPR2), which we show is expressed on the apical and lateral membranes of colonic crypt epithelial cells, mediates N-formylpeptide–dependent epithelial cell proliferation and renewal. Colonic epithelial cells in FPR2-deficient mice displayed defects in commensal bacterium–dependent homeostasis as shown by the absence of responses to N-formylpeptide stimulation, shortened colonic crypts, reduced acute inflammatory responses to dextran sulfate sodium (DSS) challenge, delayed mucosal restoration after injury, and increased azoxymethane-induced tumorigenesis. These results indicate that FPR2 is critical in mediating homeostasis, inflammation, and epithelial repair processes in the colon.

Authors

Keqiang Chen, Mingyong Liu, Ying Liu, Teizo Yoshimura, Wei Shen, Yingying Le, Scott Durum, Wanghua Gong, Chunyan Wang, Ji-Liang Gao, Philip M. Murphy, Ji Ming Wang

IgG4 subclass antibodies impair antitumor immunity in melanoma

• Text
• PDF

Abstract

Host-induced antibodies and their contributions to cancer inflammation are largely unexplored. IgG4 subclass antibodies are present in IL-10–driven Th2 immune responses in some inflammatory conditions. Since Th2-biased inflammation is a hallmark of tumor microenvironments, we investigated the presence and functional implications of IgG4 in malignant melanoma. Consistent with Th2 inflammation, CD22⁺ B cells and IgG4⁺-infiltrating cells accumulated in tumors, and IL-10, IL-4, and tumor-reactive IgG4 were expressed in situ. When compared with B cells from patient lymph nodes and blood, tumor-associated B cells were polarized to produce IgG4. Secreted B cells increased VEGF and IgG4, and tumor cells enhanced IL-10 secretion in cocultures. Unlike IgG1, an engineered tumor antigen-specific IgG4 was ineffective in triggering effector cell–mediated tumor killing in vitro. Antigen-specific and nonspecific IgG4 inhibited IgG1-mediated tumoricidal functions. IgG4 blockade was mediated through reduction of FcγRI activation. Additionally, IgG4 significantly impaired the potency of tumoricidal IgG1 in a human melanoma xenograft mouse model. Furthermore, serum IgG4 was inversely correlated with patient survival. These findings suggest that IgG4 promoted by tumor-induced Th2-biased inflammation may restrict effector cell functions against tumors, providing a previously unexplored aspect of tumor-induced immune escape and a basis for biomarker development and patient-specific therapeutic approaches.

Authors

Panagiotis Karagiannis, Amy E. Gilbert, Debra H. Josephs, Niwa Ali, Tihomir Dodev, Louise Saul, Isabel Correa, Luke Roberts, Emma Beddowes, Alexander Koers, Carl Hobbs, Silvia Ferreira, Jenny L.C. Geh, Ciaran Healy, Mark Harries, Katharine M. Acland, Philip J. Blower, Tracey Mitchell, David J. Fear, James F. Spicer, Katie E. Lacy, Frank O. Nestle, Sophia N. Karagiannis

Tumor VEGF:VEGFR2 autocrine feed-forward loop triggers angiogenesis in lung cancer

• Text
• PDF

Abstract

The molecular mechanisms that control the balance between antiangiogenic and proangiogenic factors and initiate the angiogenic switch in tumors remain poorly defined. By combining chemical genetics with multimodal imaging, we have identified an autocrine feed-forward loop in tumor cells in which tumor-derived VEGF stimulates VEGF production via VEGFR2-dependent activation of mTOR, substantially amplifying the initial proangiogenic signal. Disruption of this feed-forward loop by chemical perturbation or knockdown of VEGFR2 in tumor cells dramatically inhibited production of VEGF in vitro and in vivo. This disruption was sufficient to prevent tumor growth in vivo. In patients with lung cancer, we found that this VEGF:VEGFR2 feed-forward loop was active, as the level of VEGF/VEGFR2 binding in tumor cells was highly correlated to tumor angiogenesis. We further demonstrated that inhibition of tumor cell VEGFR2 induces feedback activation of the IRS/MAPK signaling cascade. Most strikingly, combined pharmacological inhibition of VEGFR2 (ZD6474) and MEK (PD0325901) in tumor cells resulted in dramatic tumor shrinkage, whereas monotherapy only modestly slowed tumor growth. Thus, a tumor cell-autonomous VEGF:VEGFR2 feed-forward loop provides signal amplification required for the establishment of fully angiogenic tumors in lung cancer. Interrupting this feed-forward loop switches tumor cells from an angiogenic to a proliferative phenotype that sensitizes tumor cells to MAPK inhibition.

Authors

Sampurna Chatterjee, Lukas C. Heukamp, Maike Siobal, Jakob Schöttle, Caroline Wieczorek, Martin Peifer, Davide Frasca, Mirjam Koker, Katharina König, Lydia Meder, Daniel Rauh, Reinhard Buettner, Jürgen Wolf, Rolf A. Brekken, Bernd Neumaier, Gerhard Christofori, Roman K. Thomas, Roland T. Ullrich

BM mesenchymal stromal cell–derived exosomes facilitate multiple myeloma progression

• Text
• PDF

Abstract

BM mesenchymal stromal cells (BM-MSCs) support multiple myeloma (MM) cell growth, but little is known about the putative mechanisms by which the BM microenvironment plays an oncogenic role in this disease. Cell-cell communication is mediated by exosomes. In this study, we showed that MM BM-MSCs release exosomes that are transferred to MM cells, thereby resulting in modulation of tumor growth in vivo. Exosomal microRNA (miR) content differed between MM and normal BM-MSCs, with a lower content of the tumor suppressor miR-15a. In addition, MM BM-MSC–derived exosomes had higher levels of oncogenic proteins, cytokines, and adhesion molecules compared with exosomes from the cells of origin. Importantly, whereas MM BM-MSC–derived exosomes promoted MM tumor growth, normal BM-MSC exosomes inhibited the growth of MM cells. In summary, these in vitro and in vivo studies demonstrated that exosome transfer from BM-MSCs to clonal plasma cells represents a previously undescribed and unique mechanism that highlights the contribution of BM-MSCs to MM disease progression.

Authors

Aldo M. Roccaro, Antonio Sacco, Patricia Maiso, Abdel Kareem Azab, Yu-Tzu Tai, Michaela Reagan, Feda Azab, Ludmila M. Flores, Federico Campigotto, Edie Weller, Kenneth C. Anderson, David T. Scadden, Irene M. Ghobrial

STAT3 regulates arginase-I in myeloid-derived suppressor cells from cancer patients

• Text
• PDF

Abstract

Myeloid-derived suppressor cells (MDSC) play a key immunosuppressive role in various types of cancer, including head and neck squamous cell carcinoma (HNSCC). In this study, we characterized CD14⁺HLA-DR^–/lo cells sorted from the tumors, draining lymph nodes, and peripheral blood of HNSCC patients. CD14⁺HLA-DR^–/lo cells were phenotyped as CD11b⁺, CD33⁺, CD34⁺, arginase-I⁺, and ROS⁺. In all 3 compartments, they suppressed autologous, antigen-independent T cell proliferation in a differential manner. The abundance of MDSC correlated with stage, but did not correlate with previous treatment with radiation or subsites of HNSCC. Interestingly, MDSC from all 3 compartments showed high phosphorylated STAT3 levels that correlated with arginase-I expression levels and activity. Stattic, a STAT3-specific inhibitor, and STAT3-targeted siRNA abrogated MDSC’s suppressive function. Inhibition of STAT3 signaling also resulted in decreased arginase-I activity. Analysis of the human arginase-I promoter region showed multiple STAT3-binding elements, and ChIP demonstrated that phosphorylated STAT3 binds to multiple sites in the arginase-I promoter. Finally, rescue of arginase-I activity after STAT3 blockade restored MDSC’s suppressive function. Taken together, these results demonstrate that the suppressive function of arginase-I in both infiltrating and circulating MDSC is a downstream target of activated STAT3.

Authors

David Vasquez-Dunddel, Fan Pan, Qi Zeng, Mikhail Gorbounov, Emilia Albesiano, Juan Fu, Richard L. Blosser, Ada J. Tam, Tullia Bruno, Hao Zhang, Drew Pardoll, Young Kim

Sprouty2, PTEN, and PP2A interact to regulate prostate cancer progression

• Text
• PDF

Abstract

Concurrent activation of RAS/ERK and PI3K/AKT pathways is implicated in prostate cancer progression. The negative regulators of these pathways, including sprouty2 (SPRY2), protein phosphatase 2A (PP2A), and phosphatase and tensin homolog (PTEN), are commonly inactivated in prostate cancer. The molecular basis of cooperation between these genetic alterations is unknown. Here, we show that SPRY2 deficiency alone triggers activation of AKT and ERK, but this is insufficient to drive tumorigenesis. In addition to AKT and ERK activation, SPRY2 loss also activates a PP2A-dependent tumor suppressor checkpoint. Mechanistically, the PP2A-mediated growth arrest depends on GSK3β and is ultimately mediated by nuclear PTEN. In murine prostate cancer models, Pten haploinsufficiency synergized with Spry2 deficiency to drive tumorigenesis, including metastasis. Together, these results show that loss of Pten cooperates with Spry2 deficiency by bypassing a novel tumor suppressor checkpoint. Furthermore, loss of SPRY2 expression correlates strongly with loss of PTEN and/or PP2A subunits in human prostate cancer. This underlines the cooperation between SPRY2 deficiency and PTEN or PP2A inactivation in promoting tumorigenesis. Overall, we propose SPRY2, PTEN, and PP2A status as an important determinant of prostate cancer progression. Characterization of this trio may facilitate patient stratification for targeted therapies and chemopreventive interventions.

Authors

Rachana Patel, Meiling Gao, Imran Ahmad, Janis Fleming, Lukram B. Singh, Taranjit Singh Rai, Arthur B. McKie, Morag Seywright, Robert J. Barnetson, Joanne Edwards, Owen J. Sansom, Hing Y. Leung