P-271: YM155 exerts anti-myeloma effects via Myc/BBC3 signaling pathway in vitro

Introduction: Our previous studies have demonstrated a strong link between Myc rearrangement (Myc-R) and poor prognosis in newly diagnosed multiple myeloma (NDMM). Survivin inhibitor YM155, a novel small molecule, is currently under clinical investigation in aggressive B cell lymphomas with Myc translocation. However, its effects on myeloma cells remain unclear. This study aims to explore the anti-myeloma mechanisms of YM155 in vitro through cell-based experiments.

Methods: In vitro, six MM cell lines (AMO-1, MM.1S, RPMI-8226, NCI-H929, U266, and KMS-11) were treated with YM155 to determine IC50 using CCK8 method. Cell apoptosis was detected by flow cytometry. RNA sequencing was performed on MM.1S and RPMI-8226 cells treated with YM155 to identify relevant regulatory pathways. Protein-protein interaction and transcription factor target prediction analyses were conducted to predict interactions between proteins and the binding sites of Myc and target genes. The identified regulatory pathways were validated with qPCR and Western blot (WB).

Results: The IC50 of YM155 in various MM cell lines ranged from 2.5 to 15 nM, which was similar to that of bortezomib. YM155 demonstrated a time- and dose-dependent inhibition of cell proliferation and apoptosis, significantly downregulating Myc mRNA expression and protein levels. The combination of YM155 and bortezomib showed superior cell-killing effects compared to single-agent, suggesting a synergistic effect. RNA sequencing indicated that Myc expression was suppressed and P53 signaling pathway was activated after YM155 treatment. This was confirmed by RT-qPCR and WB, which showed activation of pro-apoptotic protein BBC3 and inhibition of anti-apoptotic protein BCL2. JASPAR bioinformatic analysis predicted that Myc might inhibit BBC3 expression by binding to its promoter region, thereby activating the P53 pathway. Additionally, the IC50 of YM155 in bortezomib-resistant cells was similar to that in non-resistant cells.

Conclusions: YM155 exhibits in vitro anti-myeloma activity in a concentration- and time-dependent manner and has a synergistic anti-tumor effect with bortezomib, reversing resistance to some extent. YM155 exerts its anti-myeloma effects by inhibiting Myc and upregulating BBC3 expression, which activates the P53 pathway. This provides a potential evidence for the treatment of high-risk/relapsed refractory MM.