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 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
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
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
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
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.