SD-36 promotes growth inhibition and induces apoptosis via suppression of Mcl-1 in glioma

Glioma is one of the most commonly observed tumours, representing approximately 75% of brain tumours in the adult population. Generally, glioma therapy includes surgical resection followed by radiotherapy and chemotherapy. The transcription factor STAT3 (signal transducer and activator of transcription 3) is a promising target for the treatment of cancer and several other diseases. At nanomolar concentrations, SD-36 induces rapid cellular degradation of STAT3 but cannot degrade other STAT proteins. The current study demonstrates the therapeutic efficacies of the STAT3 degraders SD-36 against glioma, as well as understanding the elucidating mechanisms and identifying molecular markers that determine cell sensitivity to STAT3 degraders. Glioma cell lines possessed similar response patterns to SD-36 but different responses to the STAT3 inhibitor Stattic. SD-36 potently induced apoptosis in glioma cells along with a reduction in Mcl-1 levels, which are critical for mediating the induction of apoptosis and enhancing TMZ-induced apoptosis. Accordingly, SD-36 sensitizes the antitumour effect of TMZ in patient-derived xenograft. In addition, the downregulation of Mcl-1 expression-mediated antitumour effect of SD-36 was analysed in cell-derived xenograft. These observations need to be validated clinically to confirm the efficacy of STAT3 degraders in glioma.