EGR1 Interacts with TBX2 and Functions as a Tumor Suppressor in Rhabdomyosarcoma

Abstract

BackgroundEGR1, one of the immediate‐early response genes, can function as a tumor suppressor gene or as an oncogene in cancer. The function of EGR1 has not been fully characterized in rhabdomyosarcoma (RMS), a pediatric cancer derived from the muscle linage.MethodsEGR1 expression was characterized by RNA and protein analysis in RMS cells. EGR1 was ectopically expressed in RH30 cells by transfection of an EGR1 expression plasmid and selection of stable cell lines. A combination of techniques such as proliferation assays, scratch assays and soft agar assays were performed with RH30 cells expressing EGR1 to demonstrate the loss of oncogenic growth properties. Differentiation of RMS cells was detected by immunohistochemistry and RNA and protein analysis. Co‐immunoprecipitation studies were used to identify the interaction between EGR1 and TBX2 and gene expression changes were detected by RNA and protein analysis. TUNEL assays and RNA and protein analysis were used to characterize apoptosis in EGR1 expressing RH30 cells.ResultsWe found that EGR1 is downregulated in the alveolar RMS (ARMS) subtype but expressed at levels comparable to normal skeletal muscle in embryonal RMS (ERMS). We found that over expression of EGR1 in ARMS significantly decreased cell proliferation, mobility, and anchorage‐independent growth. EGR1 also promoted differentiation in RMS cells by inducing the expression of several genes involved in muscle differentiation including myosin heavy chain (MHC), MYOD1 and MYOG. We also found that EGR1 interacts with TBX2, which we have shown functions as an oncogene in RMS. The interaction inhibits EGR1 dependent gene expression, which includes the cell cycle regulators CDKN1A and PTEN as well as other important cell growth drivers such as NDRG1 and CST6. We also found that EGR1 induces apoptosis by triggering the intrinsic apoptosis pathway. EGR1 also sensitized RMS cells to chemotherapeutic agents.ConclusionsWe show that EGR1 is a potent tumor suppressor in RMS and that EGR1 and TBX2 antagonize each other's function. Our data suggest that activation of EGR1 may improve the therapeutic targeting of RMS.Support or Funding InformationHigher Committee for Education Development in Iraq (HCED)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.