USP7 inhibition inhibits proliferation and induces megakaryocytic differentiation in MDS cells by upregulating gelsolin

Myelodysplastic syndrome (MDS), a largely incurable hematological malignancy, is driven by complex genetic and epigenetic alterations from an aberrant clone of hematopoietic stem/progenitor cells (HSPCs). Ubiquitin-specific protease 7 (USP7) has been demonstrated to have an important oncogenic role in the development of several cancer types, but its role in MDS is unknown. Here, we demonstrate that USP7 expression is elevated in MDS cell lines and patient samples. The USP7-selective small-molecule inhibitors P5091 and P22077 inhibited cell proliferation and induced megakaryocytic differentiation in both cell lines and primary cells. Furthermore, pharmacological inhibition of USP7 markedly suppressed the growth of MDS cell lines in xenograft mouse models. To explore the mechanisms underlying the observed phenotypic changes, we employed RNA-seq to compare the differences in genes after USP7 inhibitor treatment and found that gelsolin (GSN) expression was increased significantly after USP7 inhibitor treatment. Furthermore, knockdown of GSN attenuated the proliferation inhibition, apoptosis induction and megakaryocyte differentiation induced by USP7 inhibitors in MDS cells. Collectively, our findings identify previously unknown roles of USP7 and suggest that the USP7/GSN axis may be a potential therapeutic target in MDS.