The EWS-FLI1/EGR1/IGF1R cascade combined with the previously confirmed pathways can form a speculative circuit, implicating positive feedback for tumourigenesis in ES.
Taken together, these results suggest that IGF1R inhibitors activation is an escape mechanism to CDK4/6 inhibitors in Ewing sarcoma and that dual targeting of CDK4/6 inhibitors and IGF1R inhibitors provides a candidate synergistic combination for clinical application in this disease.
After the formal demonstration of a direct association between IGF2BP3 and <i>IGF1R</i> mRNA using ribo-immunoprecipitation assay, we performed <i>in vitro</i> studies using A673 and TC-71 ES cell lines to demonstrate that IGF2BP3 loss promotes the downregulation of IGF1R and a decreased biological response to IGF1, represented by reduced migration and cell growth.
Our previous study showed that cyclin-dependent kinase 4/6 (CDK4/6) and insulin-like growth factor-1 receptor (IGF-1R) inhibitors were effective on the Ewing's sarcoma PDOX, but not doxorubicin, similar to the patient's resistance to doxorubicin.
Both tumor architecture and shear force have profound effects on Ewing sarcoma (ES) cell behavior and are known to elicit ligand-mediated activation of the insulin-like growth factor-1 receptor (IGF-1R), thereby mediating resistance of ES cells to IGF-1R inhibitors.
The aim of the present study was to determine efficacy of cyclin-dependent kinase 4/6 (CDK4/6) and insulin-like growth factor-1 receptor (IGF-1R) inhibitors on the Ewing's sarcoma PDOX.
Repression of autocrine IGF1 by BET inhibitors led to significant inhibition of the IGF1R/AKT pathway critical to Ewing sarcoma cell proliferation and survival.
Here, we report that IGF1R (15/15) and ROR1 (11/15) were highly expressed in sarcoma cell lines including Ewing sarcoma, osteosarcoma, alveolar or embryonal rhabdomyosarcoma, and fibrosarcoma.
Inhibition of IGF1R either by the specific AVE1642 human antibody or by the dual IGF1R/insulin receptor inhibitor OSI-906 (Linsitinib) greatly potentiate the efficacy of trabectedin in the 13 EWS cell lines here considered as well as in TC-71 and 6647 xenografts.
However, despite encouraging in vitro and in vivo results, apart from intriguing results of Insulin-like Growth Factor-1 Receptor (IGF-1R) antibodies in ES, clinical studies are limited or disappointing.
These results indicate that inhibiting IGF-IR by antisense strategies may be relevant to the clinical treatment of ES patients by reducing the malignant potential of these cells and enhancing the effectiveness of chemotherapy.