ABSTRACT
Low-dose antiangiogenic therapies have demonstrated the ability to enhance normalization of tumor vessels, consequently improving hypoxia levels, drug delivery, and promoting anticancer immune responses. Mast cells have been identified as contributors to resistance against antiangiogenic therapy and facilitators of abnormal neoangiogenesis. In this study, we demonstrate that by simultaneously targeting intratumoral mast cells with Imatinib and administering low-dose anti-VEGFR2 therapy, antitumor efficacy can be enhanced in preclinical models. Thus, combinatory treatment overcomes therapy resistance, while concurrently promoting tumor vessel normalization. Notably, histomorphometric analysis of tumor sections revealed that vessel perfusion could be improved through mast cell inhibition and, despite a significantly reduced microvessel density, the combination treatment did not result in elevated tumor hypoxia levels compared to anti-VEGFR2 therapy alone. Short-term Imatinib application effectively increased antitumor efficacy, and by prolonging the application of Imatinib tumor vessel normalization was additionally improved. The combination of mast cell depletion and antiangiogenic treatments has not been investigated in detail and promises to help overcoming therapy resistance. Further studies will be required to explore their impact on other treatment approaches, and subsequently to validate these findings in a clinical setting.
ABSTRACT
The TAM (TYRO3, MERTK, and AXL) family of receptor tyrosine kinases are pleiotropic regulators of adult tissue homeostasis maintaining organ integrity and self-renewal. Disruption of their homeostatic balance fosters pathological conditions like autoinflammatory or degenerative diseases including rheumatoid arthritis, lupus erythematodes, or liver fibrosis. Moreover, TAM receptors exhibit prominent cell-transforming properties, promoting tumor progression, metastasis, and therapy resistance in various cancer entities. Emerging evidence shows that TAM receptors are involved in bone homeostasis by regulating osteoblastic bone formation and osteoclastic bone resorption. Therefore, TAM receptors emerge as new key players of the regulatory cytokine network of osteoblasts and osteoclasts and represent accessible targets for pharmacologic therapy for a broad set of different bone diseases, including primary and metastatic bone tumors, rheumatoid arthritis, or osteoporosis.
Subject(s)
Arthritis, Rheumatoid , Bone Diseases , Bone Resorption , Adult , Humans , Osteoblasts , Osteoclasts , OsteogenesisABSTRACT
The fine equilibrium of bone homeostasis is maintained by bone-forming osteoblasts and bone-resorbing osteoclasts. Here, we show that TAM receptors MERTK and TYRO3 exert reciprocal effects in osteoblast biology: Osteoblast-targeted deletion of MERTK promotes increased bone mass in healthy mice and mice with cancer-induced bone loss, whereas knockout of TYRO3 in osteoblasts shows the opposite phenotype. Functionally, the interaction of MERTK with its ligand PROS1 negatively regulates osteoblast differentiation via inducing the VAV2-RHOA-ROCK axis leading to increased cell contractility and motility while TYRO3 antagonizes this effect. Consequently, pharmacologic MERTK blockade by the small molecule inhibitor R992 increases osteoblast numbers and bone formation in mice. Furthermore, R992 counteracts cancer-induced bone loss, reduces bone metastasis and prolongs survival in preclinical models of multiple myeloma, breast- and lung cancer. In summary, MERTK and TYRO3 represent potent regulators of bone homeostasis with cell-type specific functions and MERTK blockade represents an osteoanabolic therapy with implications in cancer and beyond.
Subject(s)
Proto-Oncogene Proteins , Receptor Protein-Tyrosine Kinases , Mice , Animals , c-Mer Tyrosine Kinase/genetics , c-Mer Tyrosine Kinase/metabolism , Receptor Protein-Tyrosine Kinases/metabolism , Proto-Oncogene Proteins/metabolism , Homeostasis , Carrier ProteinsABSTRACT
Despite enormous efforts to improve therapeutic options, pancreatic cancer remains a fatal disease and is expected to become the second leading cause of cancer-related deaths in the next decade. Previous research identified lipid metabolic pathways to be highly enriched in pancreatic ductal adenocarcinoma (PDAC) cells. Thereby, cholesterol uptake and synthesis promotes growth advantage to and chemotherapy resistance for PDAC tumor cells. Here, we demonstrate that high-density lipoprotein (HDL)-mediated efficient cholesterol removal from cancer cells results in PDAC cell growth reduction and induction of apoptosis in vitro. This effect is driven by an HDL particle composition-dependent interaction with SR-B1 and ABCA1 on cancer cells. AAV-mediated overexpression of APOA1 and rHDL injections decreased PDAC tumor development in vivo. Interestingly, plasma samples from pancreatic-cancer patients displayed a significantly reduced APOA1-to-SAA1 ratio and a reduced cholesterol efflux capacity compared with healthy donors. We conclude that efficient, HDL-mediated cholesterol depletion represents an interesting strategy to interfere with the aggressive growth characteristics of PDAC.
Subject(s)
Carcinoma, Pancreatic Ductal , Pancreatic Neoplasms , Carcinoma, Pancreatic Ductal/genetics , Cell Proliferation , Cholesterol/metabolism , Humans , Pancreatic Neoplasms/metabolism , Pancreatic NeoplasmsABSTRACT
BCR-ABL negative myeloproliferative neoplasms (MPNs) consist of essential thrombocythemia, polycythemia vera, and myelofibrosis. The majority of patients harbor the JAK2-activating mutation V617F. JAK2 inhibitors were shown to reduce symptom burden and splenomegaly in MPN patients. However, treatment options are limited after failure of JAK2 inhibitors. AXL, a member of the TAM family of receptor tyrosine kinases, mediates survival and therapy resistance of different myeloid cancers including acute myeloid leukemia and chronic myeloid leukemia. We studied the relevance of AXL as a target in MPN using primary patient cells and preclinical disease models. We found that AXL is abundantly activated in MPN cells and that its ligand growth arrest-specific gene 6 is upregulated in MPN patients. Pharmacologic and genetic blockade of AXL impaired viability, decreased proliferation and increased apoptosis of MPN cells. Interestingly, ruxolitinib treatment induced increased phosphorylation of AXL indicating that activation of AXL might mediate resistance to ruxolitinib. Consistently, the AXL inhibitor bemcentinib exerted additive effects with ruxolitinib via impaired STAT3, STAT5, and AKT signaling. Both agents had activity when employed alone and exerted an additive effect on survival and splenomegaly in vivo. Moreover, bemcentinib treatment normalized red blood cell count and hemoglobin levels in vivo. Thus, our data indicate that AXL inhibition represents a novel treatment option in MPN warranting clinical investigation.
ABSTRACT
Influenza during pregnancy can affect the health of offspring in later life, among which neurocognitive disorders are among the best described. Here, we investigate whether maternal influenza infection has adverse effects on immune responses in offspring. We establish a two-hit mouse model to study the effect of maternal influenza A virus infection (first hit) on vulnerability of offspring to heterologous infections (second hit) in later life. Offspring born to influenza A virus infected mothers are stunted in growth and more vulnerable to heterologous infections (influenza B virus and MRSA) than those born to PBS- or poly(I:C)-treated mothers. Enhanced vulnerability to infection in neonates is associated with reduced haematopoetic development and immune responses. In particular, alveolar macrophages of offspring exposed to maternal influenza have reduced capacity to clear second hit pathogens. This impaired pathogen clearance is partially reversed by adoptive transfer of alveolar macrophages from healthy offspring born to uninfected dams. These findings suggest that maternal influenza infection may impair immune ontogeny and increase susceptibility to early life infections of offspring.
Subject(s)
Bacterial Infections/immunology , Influenza A virus/immunology , Orthomyxoviridae Infections/virology , Parturition , Animals , Animals, Newborn , Disease Models, Animal , Female , Hematopoiesis , Humans , Influenza, Human/immunology , Lung/immunology , Macrophages, Alveolar , Mice , Mice, Inbred C57BL , Mothers , Poly I-C , PregnancyABSTRACT
Pulmonary arterial hypertension (PAH), is a fatal disease characterized by a pseudo-malignant phenotype. We investigated the expression and the role of the receptor tyrosine kinase Axl in experimental (i.e., monocrotaline and Su5416/hypoxia treated rats) and clinical PAH. In vitro Axl inhibition by R428 and Axl knock-down inhibited growth factor-driven proliferation and migration of non-PAH and PAH PASMCs. Conversely, Axl overexpression conferred a growth advantage. Axl declined in PAECs of PAH patients. Axl blockage inhibited BMP9 signaling and increased PAEC apoptosis, while BMP9 induced Axl phosphorylation. Gas6 induced SMAD1/5/8 phosphorylation and ID1/ID2 increase were blunted by BMP signaling obstruction. Axl association with BMPR2 was facilitated by Gas6/BMP9 stimulation and diminished by R428. In vivo R428 aggravated right ventricular hypertrophy and dysfunction, abrogated BMPR2 signaling, elevated pulmonary endothelial cell apoptosis and loss. Together, Axl is a key regulator of endothelial BMPR2 signaling and potential determinant of PAH.
Subject(s)
Bone Morphogenetic Protein Receptors, Type II/genetics , Gene Expression Regulation , Pulmonary Arterial Hypertension/genetics , Receptor Protein-Tyrosine Kinases/deficiency , Angiogenesis Inhibitors/pharmacology , Animals , Bone Morphogenetic Protein Receptors, Type II/metabolism , Indoles/pharmacology , Male , Monocrotaline/pharmacology , Pyrroles/pharmacology , Rats, Inbred WKY , Rats, Sprague-DawleyABSTRACT
It is well-known that sex hormones can directly and indirectly influence immune cell function. Different studies support a suppressive role of androgens on different components of the immune system by decreasing antibody production, T cell proliferation, NK cytotoxicity, and stimulating the production of anti-inflammatory cytokines. Androgen receptors have also been detected in many different cells of hematopoietic origin leading to direct effects of their ligands on the development and function of the immune system. The immunosuppressive properties of androgens could contribute to gender dimorphisms in autoimmune and infectious disease and thereby also hamper immune surveillance of tumors. Consistently, females generally are more prone to autoimmunity, while relatively less susceptible to infections, and have lower incidence and mortality of the majority of cancers compared to males. Some studies show that androgen deprivation therapy (ADT) can induce expansion of naïve T cells and increase T-cell responses. Emerging clinical data also reveal that ADT might enhance the efficacy of various immunotherapies including immune checkpoint blockade. In this review, we will discuss the potential role of androgens and their receptors in the immune responses in the context of different diseases. A particular focus will be on cancer, highlighting the effect of androgens on immune surveillance, tumor biology and on the efficacy of anti-cancer therapies including emerging immune therapies.
Subject(s)
Androgens/immunology , Immunologic Surveillance/immunology , Neoplasms/immunology , Receptors, Androgen/immunology , Animals , Female , Humans , Male , Self Tolerance/immunologyABSTRACT
We analyzed the predictive potential of pretreatment soluble carbonic anhydrase IX levels (sCAIX) for the efficacy of bevacizumab in the phase III neoadjuvant GeparQuinto trial. sCAIX was determined by enzyme-linked immunosorbent assay (ELISA). Correlations between sCAIX and pathological complete response (pCR), disease-free and overall survival (DFS, OS) were assessed with logistic and Cox proportional hazard regression models using bootstrapping for robust estimates and internal validation. 1,160 HER2-negative patient sera were analyzed, of whom 577 received bevacizumab. Patients with low pretreatment sCAIX had decreased pCR rates (12.1 vs. 20.1%, p = 0.012) and poorer DFS (adjusted 5-year DFS 71.4 vs. 80.5 months, p = 0.010) compared to patients with high sCAIX when treated with neoadjuvant chemotherapy (NCT). For patients with low sCAIX, pCR rates significantly improved upon addition of bevacizumab to NCT (12.1 vs. 20.4%; p = 0.017), which was not the case in patients with high sCAIX (20.1% for NCT vs. 17.0% for NCT-B, p = 0.913). When analyzing DFS we found that bevacizumab improved 5-year DFS for patients with low sCAIX numerically but not significantly (71.4 vs. 78.5 months; log rank 0.234). In contrast, addition of bevacizumab worsened 5-year DFS for patients with high sCAIX (81 vs. 73.6 months, log-rank 0.025). By assessing sCAIX levels we identified a patient cohort in breast cancer that is potentially undertreated with NCT alone. Bevacizumab improved pCR rates in this group, suggesting sCAIX is a predictive biomarker for bevacizumab with regards to treatment response. Our data also show that bevacizumab is not beneficial in patients with high sCAIX.
Subject(s)
Antigens, Neoplasm/blood , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Breast Neoplasms/drug therapy , Breast Neoplasms/enzymology , Carbonic Anhydrase IX/blood , Adult , Aged , Bevacizumab/administration & dosage , Biomarkers, Tumor/blood , Chemotherapy, Adjuvant , Cyclophosphamide/administration & dosage , Disease-Free Survival , Docetaxel/administration & dosage , Epirubicin/administration & dosage , Female , Humans , Middle Aged , Neoadjuvant Therapy , Young AdultABSTRACT
Cancer represents a leading cause of death with continuously increasing incidence worldwide. Many solid cancer types in non-reproductive organs are significantly more frequent and deadly in males compared to females. This sex-biased difference is also present in hematologic malignancies. In this review, we present an overview about sex differences in cancer with a focus on leukemia. We discuss mechanisms potentially underlying the observed sex-biased imbalance in cancer incidence and outcome including sex hormones, sex chromosomes, and immune responses. Besides affecting the pathobiology of cancers, sex differences can also influence drug responses, most notably those to immune checkpoint blockers. Therefore, sex should become a relevant factor in clinical trial design in order to avoid over- or under-treatment of one sex.
Subject(s)
Hematologic Neoplasms/immunology , Leukemia/immunology , Sex Characteristics , Chromosomes, Human/genetics , Chromosomes, Human/immunology , Female , Gonadal Steroid Hormones/genetics , Gonadal Steroid Hormones/immunology , Hematologic Neoplasms/epidemiology , Hematologic Neoplasms/genetics , Hematologic Neoplasms/pathology , Humans , Incidence , Leukemia/epidemiology , Leukemia/genetics , Leukemia/pathology , Male , Sex Chromosomes/genetics , Sex Chromosomes/immunologySubject(s)
Anaplastic Lymphoma Kinase/metabolism , Carcinoma, Non-Small-Cell Lung/genetics , Crizotinib/pharmacology , Drug Resistance, Neoplasm/genetics , Gene Amplification , Lung Neoplasms/genetics , Proto-Oncogene Proteins c-met/genetics , Antineoplastic Agents/pharmacology , Carcinoma, Non-Small-Cell Lung/drug therapy , Carcinoma, Non-Small-Cell Lung/pathology , Cell-Free Nucleic Acids/genetics , Female , Humans , Lung Neoplasms/drug therapy , Lung Neoplasms/pathology , Middle Aged , Neoplastic Cells, Circulating/metabolism , Neoplastic Cells, Circulating/pathology , PrognosisABSTRACT
Intrinsic and adaptive resistance hampers the success of antiangiogenic therapies (AAT), especially in breast cancer where this treatment modality has proven largely ineffective. Therefore, novel strategies to improve the efficacy of AAT are warranted. Solid tumors such as breast cancer are characterized by a high infiltration of myeloid-derived suppressor cells (MDSC), which are key drivers of resistance to AAT. Therefore, we hypothesized that all-trans retinoic acid (ATRA), which induces differentiation of MDSC into mature cells, could improve the therapeutic effect of AAT. ATRA increased the efficacy of anti-VEGFR2 antibodies alone and in combination with chemotherapy in preclinical breast cancer models. ATRA reverted the anti-VEGFR2-induced accumulation of intratumoral MDSC, alleviated hypoxia, and counteracted the disorganization of tumor microvessels. Mechanistic studies indicate that ATRA treatment blocked the AAT-induced expansion of MDSC secreting high levels of vessel-destabilizing S100A8. Thus, concomitant treatment with ATRA holds the potential to improve AAT in breast cancer and possibly other tumor types.Significance: Increasing the therapeutic efficiency of antiangiogenic drugs by reducing resistance-conferring myeloid-derived suppressor cells might improve breast cancer treatment.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/12/3220/F1.large.jpg Cancer Res; 78(12); 3220-32. ©2018 AACR.
Subject(s)
Angiogenesis Inhibitors/pharmacology , Antineoplastic Combined Chemotherapy Protocols/pharmacology , Breast Neoplasms/drug therapy , Myeloid-Derived Suppressor Cells/drug effects , Tretinoin/pharmacology , Angiogenesis Inhibitors/therapeutic use , Animals , Antibodies, Monoclonal/pharmacology , Antibodies, Monoclonal/therapeutic use , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Breast Neoplasms/blood supply , Breast Neoplasms/immunology , Breast Neoplasms/pathology , Calgranulin A/metabolism , Cell Culture Techniques , Cell Differentiation/drug effects , Cell Differentiation/immunology , Cell Line, Tumor/transplantation , Coculture Techniques , Disease Models, Animal , Drug Resistance, Neoplasm/drug effects , Drug Screening Assays, Antitumor , Drug Synergism , Female , Human Umbilical Vein Endothelial Cells , Humans , Mice , Mice, Inbred BALB C , Myeloid-Derived Suppressor Cells/physiology , Protein Stability/drug effects , Treatment Outcome , Tretinoin/therapeutic use , Vascular Endothelial Growth Factor Receptor-2/antagonists & inhibitorsABSTRACT
Although inhibitors of bromodomain and extra terminal domain (BET) proteins show promising clinical activity in different hematologic malignancies, a systematic analysis of the consequences of pharmacological BET inhibition on healthy hematopoietic (stem) cells is urgently needed. We found that JQ1 treatment decreases the numbers of pre-, immature and mature B cells while numbers of early pro-B cells remain constant. In addition, JQ1 treatment increases apoptosis in T cells, all together leading to reduced cellularity in thymus, bone marrow and spleen. Furthermore, JQ1 induces proliferation of long-term hematopoietic stem cells, thereby increasing stem cell numbers. Due to increased numbers, JQ1-treated hematopoietic stem cells engrafted better after stem cell transplantation and repopulated the hematopoietic system significantly faster after sublethal myeloablation. As quantity and functionality of hematopoietic stem cells determine the duration of life-threatening myelosuppression, BET inhibition might benefit patients in myelosuppressive conditions.
Subject(s)
Antineoplastic Agents/pharmacology , Azepines/pharmacology , Cell Self Renewal/drug effects , Hematopoietic Stem Cells/cytology , Hematopoietic Stem Cells/drug effects , Proteins/antagonists & inhibitors , Triazoles/pharmacology , Animals , Apoptosis/drug effects , B-Lymphocytes/cytology , B-Lymphocytes/drug effects , B-Lymphocytes/metabolism , Biomarkers , Cell Cycle/drug effects , Cell Proliferation/drug effects , Graft Survival/drug effects , Hematopoiesis , Hematopoietic Stem Cell Transplantation , Hematopoietic Stem Cells/metabolism , Hematopoietic Stem Cells/radiation effects , Immunophenotyping , Mice , Phenotype , T-Lymphocytes/drug effects , T-Lymphocytes/metabolismABSTRACT
Purpose: BCR-ABL kinase inhibitors are employed successfully for chronic myeloid leukemia (CML) treatment. However, resistant disease and persistence of BCR-ABL1-independent leukemia stem and progenitor cells (LSPC) remain clinical challenges. The receptor tyrosine kinase Axl can mediate survival and therapy resistance of different cancer cells. We investigated the therapeutic potential of Axl inhibition in CML.Experimental Design: We used primary cells from patients with CML and TKI-sensitive and -resistant BCR-ABL1+ CML cell lines and a novel ponatinib-resistant cell line KCL-22 PonR. We analyzed the effects of genetic and pharmacologic Axl blockade by the small-molecule Axl inhibitor BGB324 in vitro and in vivo In BCR-ABL1-unmutated cells, we also investigated BGB324 in combination with imatinib.Results: We demonstrate overexpression of Axl receptor tyrosine kinase in primary cells of patients with CML compared with healthy individuals and a further increase of Axl expression in BCR-ABL TKI-resistant patients. We show that Axl blockage decreased growth of BCR-ABL TKI-sensitive CML cells including CD34+ cells and exerts additive effects with imatinib via inhibition of Stat5 activation. BGB324 also inhibits BCR-ABL TKI-resistant cells, including T315I-mutated and ponatinib-resistant primary cells. BGB324 exerted therapeutic effects in BCR-ABL1 T315I-mutated and ponatinib-resistant preclinical mouse models. Notably, BGB324 does not inhibit BCR-ABL1 and consequently inhibits CML independent of BCR-ABL1 mutational status.Conclusions: Our data show that Axl inhibition has therapeutic potential in BCR-ABL TKI-sensitive as well as -resistant CML and support the need for clinical trials. Clin Cancer Res; 23(9); 2289-300. ©2016 AACR.
Subject(s)
Benzocycloheptenes/administration & dosage , Fusion Proteins, bcr-abl/genetics , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/drug therapy , Proto-Oncogene Proteins/genetics , Receptor Protein-Tyrosine Kinases/genetics , Triazoles/administration & dosage , Animals , Apoptosis/drug effects , Drug Resistance, Neoplasm/genetics , Fusion Proteins, bcr-abl/antagonists & inhibitors , Humans , Imatinib Mesylate/administration & dosage , Imidazoles/administration & dosage , K562 Cells , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology , Mice , Mutation , Protein Kinase Inhibitors/administration & dosage , Proto-Oncogene Proteins/antagonists & inhibitors , Pyridazines/administration & dosage , Receptor Protein-Tyrosine Kinases/antagonists & inhibitors , Small Molecule Libraries/administration & dosage , Axl Receptor Tyrosine KinaseABSTRACT
Head and neck squamous cell carcinomas (HNSCC) exhibiting resistance to the EGFR-targeting drug cetuximab poses a challenge to their effective clinical management. Here, we report a specific mechanism of resistance in this setting based upon the presence of a single nucleotide polymorphism encoding EGFR-K521 (K-allele), which is expressed in >40% of HNSCC cases. Patients expressing the K-allele showed significantly shorter progression-free survival upon palliative treatment with cetuximab plus chemotherapy or radiation. In several EGFR-mediated cancer models, cetuximab failed to inhibit downstream signaling or to kill cells harboring a high K-allele frequency. Cetuximab affinity for EGFR-K521 was reduced slightly, but ligand-mediated EGFR activation was intact. We found a lack of glycan sialyation on EGFR-K521 that associated with reduced protein stability, suggesting a structural basis for reduced cetuximab efficacy. CetuGEX, an antibody with optimized Fc glycosylation targeting the same epitope as cetuximab, restored HNSCC sensitivity in a manner associated with antibody-dependent cellular cytotoxicity rather than EGFR pathway inhibition. Overall, our results highlight EGFR-K521 expression as a key mechanism of cetuximab resistance to evaluate prospectively as a predictive biomarker in HNSCC patients. Further, they offer a preclinical rationale for the use of ADCC-optimized antibodies to treat tumors harboring this EGFR isoform. Cancer Res; 77(5); 1188-99. ©2016 AACR.
Subject(s)
Carcinoma, Squamous Cell/drug therapy , Cetuximab/pharmacology , ErbB Receptors/genetics , Head and Neck Neoplasms/drug therapy , Animals , Antineoplastic Agents/pharmacology , Carcinoma, Squamous Cell/enzymology , Carcinoma, Squamous Cell/genetics , Cell Line, Tumor , Drug Resistance, Neoplasm , Female , Head and Neck Neoplasms/enzymology , Head and Neck Neoplasms/genetics , Humans , Mice , Mice, Inbred NOD , Polymorphism, Single Nucleotide , Random Allocation , Signal Transduction , Squamous Cell Carcinoma of Head and Neck , Xenograft Model Antitumor AssaysABSTRACT
Anti-angiogenic therapies were approved for different cancers. However, significant primary and secondary resistance hampers efficacy in several tumor types including breast cancer. Thus, we need to develop clinically applicable strategies to enhance efficacy of anti-angiogenic drugs.We report that anti-angiogenic therapies can induce upregulation of cyclooxygenase-2 (Cox-2) and of its product prostaglandin E2 (PGE2) in breast cancer models. Upon Cox-2 inhibition PGE2 levels were normalized and efficacy of anti-vascular endothelial growth factor receptor 2 (anti-VEGFR-2) antibodies and sunitinib was enhanced. Interestingly, both treatments exerted additive anti-angiogenic effects. Following Cox-2 inhibition, we observed reduced infiltration of tumors with cancer-associated fibroblasts (CAFs) and lower levels of pro-angiogenic factors active besides the VEGF axis including hepatocyte growth factor (HGF) and basic fibroblast growth factor (FGF2). Mechanistic studies indicated that Cox-2 inhibition reduced PGE2-induced migration and proliferation of CAFs via inhibiting phosphorylation of Akt.Hence, Cox-2 inhibition can increase efficacy of anti-angiogenic treatments and our findings might pave the road for clinical investigations of concomitant blockade of Cox-2 and VEGF-signaling.
Subject(s)
Cyclooxygenase 2 Inhibitors/pharmacology , Cyclooxygenase 2/metabolism , Mammary Neoplasms, Experimental/blood supply , Mammary Neoplasms, Experimental/drug therapy , Vascular Endothelial Growth Factor A/metabolism , Animals , Cell Line, Tumor , Female , Mammary Neoplasms, Experimental/metabolism , Mice , Mice, Inbred BALB C , Molecular Targeted Therapy , Neovascularization, Pathologic/drug therapy , Random Allocation , Signal TransductionABSTRACT
Novel treatment options in acute myeloid leukemia (AML) are urgently needed; treatment has not changed significantly over the past decades and survival is still dismal, especially in elderly patients. Axl, a member of the Tyro3, Axl, Mer (TAM) receptor family, mediates proliferation and survival of AML cells and is upregulated upon cytostatic treatment. In addition, AML cells induce expression of the Axl ligand growth arrest-specific gene 6 (Gas6) in bone marrow stroma cells, which further amplifies their growth and therapy resistance. Interruption of Axl signaling by pharmacological approaches, including the small molecule Axl inhibitor BGB324, decreased disease burden and prolonged survival of AML mice. The Gas6-Axl pathway has translational relevance because Axl is expressed by approximately 50% of AML patients and Axl-targeting approaches can block growth of primary human AML cells. Thus, Axl represents a potential novel target in AML and BGB324 is now in clinical development.
Subject(s)
Leukemia, Myeloid, Acute/drug therapy , Proto-Oncogene Proteins/antagonists & inhibitors , Receptor Protein-Tyrosine Kinases/antagonists & inhibitors , Aged , Humans , Signal Transduction , Axl Receptor Tyrosine KinaseABSTRACT
Patients with t(1;19)-positive acute lymphoblastic leukemia (ALL) are prone to central nervous system (CNS) relapses, and expression of the TAM (Tyro3, Axl, and Mer) receptor Mer is upregulated in these leukemias. We examined the functional role of Mer in the CNS in preclinical models and performed correlative studies in 64 t(1;19)-positive and 93 control pediatric ALL patients. ALL cells were analyzed in coculture with human glioma cells and normal rat astrocytes: CNS coculture caused quiescence and protection from methotrexate toxicity in Mer(high) ALL cell lines, which was antagonized by short hairpin RNA-mediated knockdown of Mer. Mer expression was upregulated, prosurvival Akt and mitogen-activated protein kinase signaling were activated, and secretion of the Mer ligand Galectin-3 was stimulated. Mer(high) t(1;19) primary cells caused CNS involvement to a larger extent in murine xenografts than in their Mer(low) counterparts. Leukemic cells from Mer(high) xenografts showed enhanced survival in coculture. Treatment of Mer(high) patient cells with the Mer-specific inhibitor UNC-569 in vivo delayed leukemia onset, reduced CNS infiltration, and prolonged survival of mice. Finally, a correlation between high Mer expression and CNS positivity upon initial diagnosis was observed in t(1;19) patients. Our data provide evidence that Mer is associated with survival in the CNS in t(1;19)-positive ALL, suggesting a role as a diagnostic marker and therapeutic target.
Subject(s)
Central Nervous System/metabolism , Gene Expression Regulation, Leukemic , Precursor Cell Lymphoblastic Leukemia-Lymphoma/genetics , Proto-Oncogene Proteins/genetics , Pyrazoles/therapeutic use , Pyrimidines/therapeutic use , Receptor Protein-Tyrosine Kinases/genetics , Animals , Antimetabolites, Antineoplastic/pharmacology , Astrocytes/cytology , Astrocytes/drug effects , Astrocytes/metabolism , Blood Proteins , Case-Control Studies , Cell Survival , Central Nervous System/drug effects , Central Nervous System/pathology , Child , Chromosomes, Human, Pair 1 , Chromosomes, Human, Pair 19 , Coculture Techniques , Female , Galectin 3/genetics , Galectin 3/metabolism , Galectins , Glioma/genetics , Glioma/metabolism , Glioma/pathology , Humans , Methotrexate/pharmacology , Mice , Precursor Cell Lymphoblastic Leukemia-Lymphoma/drug therapy , Precursor Cell Lymphoblastic Leukemia-Lymphoma/metabolism , Precursor Cell Lymphoblastic Leukemia-Lymphoma/pathology , Primary Cell Culture , Proto-Oncogene Proteins/antagonists & inhibitors , Proto-Oncogene Proteins/metabolism , Proto-Oncogene Proteins c-akt/genetics , Proto-Oncogene Proteins c-akt/metabolism , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , Receptor Protein-Tyrosine Kinases/antagonists & inhibitors , Receptor Protein-Tyrosine Kinases/metabolism , Signal Transduction , Translocation, Genetic , Tumor Cells, Cultured , c-Mer Tyrosine KinaseABSTRACT
The estrogen receptor α (ERα) controls cell proliferation and tumorigenesis by recruiting various cofactors to estrogen response elements (EREs) to control gene transcription. A deeper understanding of these transcriptional mechanisms may uncover therapeutic targets for ERα-dependent cancers. We show that BRD4 regulates ERα-induced gene expression by affecting elongation-associated phosphorylation of RNA polymerase II (RNAPII) and histone H2B monoubiquitination. Consistently, BRD4 activity is required for proliferation of ER(+) breast and endometrial cancer cells and uterine growth in mice. Genome-wide studies revealed an enrichment of BRD4 on transcriptional start sites of active genes and a requirement of BRD4 for H2B monoubiquitination in the transcribed region of estrogen-responsive genes. Importantly, we demonstrate that BRD4 occupancy on distal EREs enriched for H3K27ac is required for recruitment and elongation of RNAPII on EREs and the production of ERα-dependent enhancer RNAs. These results uncover BRD4 as a central regulator of ERα function and potential therapeutic target.