• Pichaya Thanindratarn, Dylan C Dean, Wenlong Feng, Ran Wei, Scott D Nelson, Francis J Hornicek, and Zhenfeng Duan.
• Department of Orthopaedic Surgery, Sarcoma Biology Laboratory, David Geffen School of Medicine, University of California, Los Angeles, 615 Charles E. Young. Dr. South, Los Angeles, CA, 90095, USA.
• Eur Spine J. 2020 Dec 1; 29 (12): 3214-3228.

PurposeTo determine the cyclin-dependent kinase 12 (CDK12) expression in chordoma patient tissues and cell lines, its correlation with oncologic outcomes, and its function in chordoma cell proliferation.MethodsA chordoma tissue microarray was constructed from fifty-six patient specimens and examined by immunohistochemistry to measure CDK12 expression and its correlation to patient clinical characteristics and survival. CDK12 expression in chordoma cell lines and patient tissues was evaluated via western blot. CDK12 specific small interfering RNA (siRNA) was applied to determine whether its inhibition attenuated chordoma cell growth and proliferation.ResultsCDK12 was expressed in the majority of chordoma specimens, with notably higher expression in patients with recurrent or metastatic disease. High CDK12 expression was an independent prognostic predictor for shorter overall and progression-free survival in chordoma by univariate and multivariate analysis. Western blot analysis revealed that CDK12 was also highly expressed in chordoma cell lines, with CDK12 specific small interfering RNA (siRNA) mediated knockdown decreasing proliferation and inducing apoptosis. Mechanistically, inhibition of CDK12 decreased phosphorylation of RNA polymerase II (RNAP II) and the anti-apoptotic proteins Survivin and Mcl-1.ConclusionHigh expression of CDK12 is an independent predictor of poor prognosis in chordoma. Inhibition of CDK12 significantly decreased chordoma cell proliferation and induced apoptosis. Our results support CDK12 as a novel prognostic biomarker and therapeutic target in chordoma.

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