The c-Myc/AKT1/TBX3 Axis Is Important to Target in the Treatment of Embryonal Rhabdomyosarcoma

Abstract

Rhabdomyosarcoma is a highly aggressive malignant cancer that arises from skeletal muscle progenitor cells and is the third most common solid tumour in children. Despite significant advances, rhabdomyosarcoma still presents a therapeutic challenge, and while targeted therapy has shown promise, there are limited options because the molecular drivers of rhabdomyosarcoma are poorly understood. We previously reported that the T-box transcription factor 3 (TBX3), which has been identified as a druggable target in many cancers, is overexpressed in rhabdomyosarcoma patient samples and cell lines. To identify new molecular therapeutic targets to treat rhabdomyosarcoma, this study investigates the potential oncogenic role(s) for TBX3 and the factors responsible for upregulating it in this cancer. To this end, rhabdomyosarcoma cell culture models in which TBX3 was either stably knocked down or overexpressed were established and the impact on key hallmarks of cancer were examined using growth curves, soft agar and scratch motility assays, as well as tumour-forming ability in nude mice. Our data show that TBX3 promotes substrate-dependent and -independent proliferation, migration and tumour formation. We further reveal that TBX3 is upregulated by c-Myc transcriptionally and AKT1 post-translationally. This study identifies c-Myc/AKT1/TBX3 as an important axis that could be targeted for the treatment of rhabdomyosarcoma.

Molecular mechanisms underpinning sarcomas and implications for current and future therapy

“…48 During Sphase, c-Myc transcriptionally activates TBX3 in chondrosarcoma and rhabdomyosarcoma cells and TBX3 represses p21 CIP1 to confer a proliferative advantage to these cells. 49,50 A summary of cell cycle proteins involved in sarcomagenesis is illustrated in Fig. 3.…”

“…Indeed, phosphorylation by AKT1 stabilizes TBX3, and TBX3 promotes rhabdomyosarcoma proliferation, anchorageindependent growth and tumor formation. 50 Furthermore, aberrant stimulation of the WNT, Notch and Hedgehog-GLI signaling pathways promotes proliferation, invasion, and metastasis of a range of sarcoma subtypes. [62][63][64][65][66][67][68] Finally, the Hippo pathway prevents uncontrolled proliferation by phosphorylating and preventing nuclear translocation of the TFs YAP and TAZ, and molecular aberrations within this pathway have been linked to sarcomagenesis.…”

Hyperactive Akt1 Signaling Increases Tumor Progression and DNA Repair in Embryonal Rhabdomyosarcoma RD Line and Confers Susceptibility to Glycolysis and Mevalonate Pathway Inhibitors

“…Since Akt1 is the preferentially expressed isoform in the RD cell line [ 38 ], we transfected a vector encoding a myrAkt1 form to mimic activated Akt signaling. As shown by immunoblotting (IB), the selected clones (referred to as hashtag-numbered myrAkt1) cultured in growth medium (GM) showed an approximately four to five-fold increase in total Akt1 and Ser 473 -phosphorylated form compared to control cells transfected with an empty vector ( Figure 1 A), confirming that myrAkt1 acts as a constitutively activated form.…”

Quantum Dot-Based Screening Identifies F3 Peptide and Reveals Cell Surface Nucleolin as a Therapeutic Target for Rhabdomyosarcoma

“…Correlation between high nucleolin and TBX3 co-expression and poor survival was observed in sarcomas [ 88 ]. Importantly, the signaling axis c-Myc/AKT1/TBX3 has been identified as an important interventional target for embryonal RMS [ 89 ]. Finally, nucleolin was among the 80 most enriched proteins detected by proteomics analysis in extracellular vesicles from five RMS cell lines [ 90 ].…”