Retraction note to: KDM3A confers metastasis and chemoresistance in epithelial ovarian cancer

Aberrant CDK9 expression within chordoma tissues and the therapeutic potential of a selective CDK9 inhibitor LDC000067

Objectives: Chordomas are slow-growing malignancies that commonly affect vital neurological structures. These neoplasms are highly resistant to current chemotherapeutic regimens and often recur after surgical intervention. Therefore, there is an urgent need to identify molecular targets and more robust drugs to improve chordoma patient outcomes. It is well accepted that cyclin-dependent protein kinase 9 (CDK9) has tumorigenic roles in various cancers; however, the expression and significance of CDK9 in chordoma remains unknown. Methods: Expression of CDK9 in chordoma cell lines and tumor tissues was examined by Western blot and immunohistochemistry (IHC). The correlation between CDK9 expression in patient tissues and clinical prognosis was analyzed. The functional roles of CDK9 in chordoma were investigated after the addition of small interfering RNA (siRNA) and CDK9 inhibitor (LDC000067). Cell growth and proliferation were assessed with MTT and clonogenic assays. The effect of CDK9 inhibition on chordoma cells was further evaluated with a three-dimensional (3D) cell culture model which mimics the in vivo environment. Results: CDK9 was expressed in both chordoma cell lines and chordoma tissues. High- expression of CDK9 correlated with recurrence and poor outcomes for chordoma patients. CDK9 silencing with siRNA decreased growth and proliferation of chordoma cells and lowered levels of Mcl-1 and RNA polymerase II (RNAP II) phosphorylation. Pharmacological inhibition of CDK9 with the small molecular inhibitor LDC000067 reduced cell growth, supported apoptosis, suppressed cell colony formation in a clonogenic assay, and decreased spheroid growth in 3D culture. Conclusion: We demonstrate that CDK9 expression in chordoma correlates with patient outcome, and, when inhibited, chordoma cell growth and proliferation significantly decreases. Taken together, these results support CDK9 as an emerging potential target in chordoma therapy.

The histone demethylase KDM3A, and its downstream target MCAM, promote Ewing Sarcoma cell migration and metastasis

Ewing Sarcoma is the second most common solid pediatric malignant neoplasm of bone and soft tissue. Driven by EWS/Ets, or rarely variant, oncogenic fusions, Ewing Sarcoma is a biologically and clinically aggressive disease with a high propensity for metastasis. However, the mechanisms underpinning Ewing Sarcoma metastasis are currently not well understood. In the present study, we identify and characterize a novel metastasis-promotional pathway in Ewing Sarcoma, involving the histone demethylase KDM3A, previously identified by our laboratory as a new cancer-promoting gene in this disease. Using global gene expression profiling, we show that KDM3A positively regulates genes and pathways implicated in cell migration and metastasis, and demonstrate, using functional assays, that KDM3A promotes migration in vitro and experimental, post-intravasation, metastasis in vivo. We further identify the melanoma cell adhesion molecule (MCAM) as a novel KDM3A target gene in Ewing Sarcoma, and an important effector of KDM3A pro-metastatic action. Specifically, we demonstrate that MCAM depletion, like KDM3A depletion, inhibits cell migration in vitro and experimental metastasis in vivo, and that MCAM partially rescues impaired migration due to KDM3A knock-down. Mechanistically, we show that KDM3A regulates MCAM expression both through a direct mechanism, involving modulation of H3K9 methylation at the MCAM promoter, and an indirect mechanism, via the Ets1 transcription factor. Finally, we identify an association between high MCAM levels in patient tumors and poor survival, in two different Ewing Sarcoma clinical cohorts. Taken together, our studies uncover a new metastasis-promoting pathway in Ewing Sarcoma, with therapeutically targetable components.