ABSTRACT
Differentiation therapy is an attractive treatment for osteosarcoma (OS). CD99 is a cell surface molecule expressed in mesenchymal stem cells and osteoblasts that is maintained during osteoblast differentiation while lost in OS. Herein, we show that whenever OS cells regain CD99, they become prone to reactivate the terminal differentiation program. In differentiating conditions, CD99-transfected OS cells express osteocyte markers, halt proliferation, and largely die by apoptosis, resembling the fate of mature osteoblasts. CD99 induces ERK activation, increasing its membrane-bound/cytoplasmic form rather than affecting its nuclear localization. Through cytoplasmic ERK, CD99 promotes activity of the main osteogenic transcriptional factors AP1 and RUNX2, which in turn enhance osteocalcin and p21(WAF1/CIP1) , leading to G0 /G1 arrest. These data underscore the alternative positions of active ERK into distinct subcellular compartments as key events for determining OS fate.
Subject(s)
Bone Neoplasms/metabolism , MAP Kinase Signaling System , Mitogen-Activated Protein Kinase 1/metabolism , Mitogen-Activated Protein Kinase 3/metabolism , Neoplasm Proteins/biosynthesis , Osteosarcoma/metabolism , 12E7 Antigen , Antigens, CD , Bone Neoplasms/genetics , Bone Neoplasms/pathology , Bone Neoplasms/therapy , Cell Adhesion Molecules , Cell Line, Tumor , Cyclin-Dependent Kinase Inhibitor p21/genetics , Cyclin-Dependent Kinase Inhibitor p21/metabolism , G1 Phase Cell Cycle Checkpoints/genetics , Humans , Mitogen-Activated Protein Kinase 1/genetics , Mitogen-Activated Protein Kinase 3/genetics , Neoplasm Proteins/genetics , Osteoblasts/metabolism , Osteoblasts/pathology , Osteosarcoma/genetics , Osteosarcoma/pathology , Osteosarcoma/therapyABSTRACT
IGF system contributes significantly to many human malignancies. Targeting IGF-I receptor (IGF-IR) has been reported to be active against several tumors, but particular efficacy was observed only against a minority of Ewing's sarcoma patients. Identification of mechanisms of acquired resistance to anti-IGF-IR agents is mandatory to individualize their use in clinics and optimize cure costs. In this study, we compared gene expression profiles of cells made resistant with three different anti-IGF-IR drugs (human antibodies AVE1642, Figitumumab, or tyrosine kinase inhibitor NVP-AEW541) to highlight common and distinctive mechanisms of resistance. Among common mechanisms, we identified two molecular signatures that distinguish sensitive from resistant cells. Annotation analysis indicated some common altered pathways, such as insulin signaling, MAPK pathway, endocytosis, and modulation of some members of the interferon-induced transmembrane protein family. Among distinctive pathways/processes, resistance to human antibodies involves mainly genes regulating neural differentiation and angiogenesis, whereas resistance to NVP-AEW541 is mainly associated with alterations in genes concerning inflammation and antigen presentation. Evaluation of the common altered pathways indicated that resistant cells seem to maintain intact the IGF-IR internalization/degradation route of sensitive cells but constantly down-regulated its expression. In resistant cells, the loss of proliferative stimulus, normally sustained by IGF-I/IGF-IR autocrine loop in Ewing's sarcoma cells, is compensated by transcriptional up-regulation of IGF-II and insulin receptor-A; this signaling seems to favor the MAPK pathway over the v-akt murine thymoma viral oncogene homolog 1 pathway. Overall, complexity of IGF system requires analytical evaluation of its components to select those patients that may really benefit from this targeted therapy and support the idea of cotargeting IGF-IR and insulin receptor-A to increase the efficacy.
Subject(s)
Receptor, IGF Type 1/metabolism , Sarcoma, Ewing/metabolism , Antibodies, Monoclonal , Antibodies, Monoclonal, Humanized/pharmacology , Cell Line, Tumor , Cell Proliferation/drug effects , Drug Resistance, Neoplasm , Humans , Immunoglobulins, Intravenous/pharmacology , Insulin-Like Growth Factor II/metabolism , Pyrimidines/pharmacology , Pyrroles/pharmacology , Receptor, IGF Type 1/antagonists & inhibitors , Receptor, Insulin/metabolism , Signal Transduction/drug effectsABSTRACT
AIMS: The role of IGF system in the pathogenesis of Ewing's sarcoma (EWS) is well-documented. However, still little information is available about the value of IGF system components as indicators of prognosis. Understanding the clinical role for IGF system in EWS patients may be important because different subtypes of patients have distinct outcome and may require different treatment protocol. We evaluated the expression of insulin-like growth factor (IGF)-receptor (IGF-IR), insulin receptor (IR), IGF-I and some major intracellular mediators (IRS1, p-ERK) in specimens from EWS patients with primary localised untreated tumours. PATIENTS AND METHODS: 290 samples were used for immunohistochemistry studies; 57 samples for Real-Time PCR studies; and serum of 67 patients for ELISA. RESULTS: IGF-IR and IR are expressed in virtually all EWS tumours. Usually both the receptors are present in the same tumour but when one receptor is lacking the other one is always present. Evaluation of IGF-IR, IR and IGF-I with quantitative methods may discriminate differential levels of expression with influences on the patients' outcome. High expression of IGF-IR, IR and IGF-I mRNAs is significantly associated with more favourable clinical outcomes. Higher circulating levels of IGF-I also correlated with lower risk to disease progression and death. CONCLUSIONS: Overall, our clinical data are in contrast with the assumption that higher amounts of IGF/IGF-IR are a surrogate for higher aggressiveness and indicate that in some cancers the transition to frank malignancy and poor treatment responsiveness seem to be associated with a reduction of IGF system activity.
