Synthetic inhibition of the SUMO pathway by targeting the SAE1 component via TAK-981 compound impairs growth and chemosensitizes embryonal and alveolar rhabdomyosarcoma cell lines

: Rhabdomyosarcoma (RMS) is a highly aggressive pediatric soft tissue sarcoma with limited therapeutic options, particularly for cases resistant to conventional treatments. The SUMOylation pathway, which plays a key role in regulating the cell cycle, apoptosis, and transcription, has emerged as a potential therapeutic target in RMS. Elevated levels of SUMO1 and SUMO2/3 conjugates in RMS cell lines, compared to normal human skeletal muscle cells, underscore the association between upregulated SUMOylation and aggressive cancer phenotypes. Understanding these molecular underpinnings is critical for the development of innovative and effective treatments. The investigation encompassed transcriptomic and protein analyses to profile SUMOylation pathway components across alveolar and embryonal RMS subtypes, aiming to identify heterogeneity that could guide personalized therapy approaches. TAK-981, a small molecule that selectively inhibits the SUMOylation of target proteins, was evaluated in combination with chemotherapeutic agents for additive or synergistic effects. Additionally, its impact on radiosensitivity and key signaling pathways, such as AKT, ERK and CAV1 phosphorylation, was assessed to elucidate its mechanism of action. Transcriptomic and proteomic analyses revealed distinct expression profiles of SUMOylation pathway components across RMS subtypes, highlighting heterogeneity that could guide personalized therapeutic strategies. Notably, SAE1 protein was overexpressed in RMS tissues and cells, positioning it as a potential biomarker for this cancer. Its activity was effectively counteracted by TAK-981, a SUMO inhibitor that demonstrated significant therapeutic potential by suppressing RMS cell proliferation and migration, and enhancing the cytotoxic effects of chemotherapeutic agents actinomycin D and doxorubicin. However, TAK-981 did not increase radiosensitivity, suggesting its selective action through chemical inhibition mechanisms. Mechanistically, TAK-981 reduced phosphorylation of key signaling proteins, including AKT, ERK and CAV1, which are critical for RMS cell survival. The findings of this study establish TAK-981 as a promising therapeutic agent for RMS. The results also provide foundational insights into the role of SUMOylation associated with the new biomarker SAE1 in RMS and its subtypes, paving the way for the development of personalized treatment strategies that leverage SUMO pathway inhibition.