Ex vivo screen identifies CDK12 as a metastatic vulnerability in osteosarcoma
Ian Bayles, … , Rani E. George, Peter C. Scacheri
Ian Bayles, … , Rani E. George, Peter C. Scacheri
Published October 1, 2019; First published September 9, 2019
Citation Information: J Clin Invest. 2019;129(10):4377-4392. https://doi.org/10.1172/JCI127718.
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Research Article Genetics Oncology

Ex vivo screen identifies CDK12 as a metastatic vulnerability in osteosarcoma

Abstract

Despite progress in intensification of therapy, outcomes for patients with metastatic osteosarcoma (OS) have not improved in thirty years. We developed a system that enabled preclinical screening of compounds against metastatic OS cells in the context of the native lung microenvironment. Using this strategy to screen a library of epigenetically targeted compounds, we identified inhibitors of CDK12 to be most effective, reducing OS cell outgrowth in the lung by more than 90% at submicromolar doses. We found that knockout of CDK12 in an in vivo model of lung metastasis significantly decreased the ability of OS to colonize the lung. CDK12 inhibition led to defects in transcription elongation in a gene length– and expression-dependent manner. These effects were accompanied by defects in RNA processing and altered the expression of genes involved in transcription regulation and the DNA damage response. We further identified OS models that differ in their sensitivity to CDK12 inhibition in the lung and provided evidence that upregulated MYC levels may mediate these differences. Our studies provided a framework for rapid preclinical testing of compounds with antimetastatic activity and highlighted CDK12 as a potential therapeutic target in OS.

Authors

Ian Bayles, Malgorzata Krajewska, W. Dean Pontius, Alina Saiakhova, James J. Morrow, Cynthia Bartels, Jim Lu, Zachary J. Faber, Yuriy Fedorov, Ellen S. Hong, Jaret M. Karnuta, Brian Rubin, Drew J. Adams, Rani E. George, Peter C. Scacheri

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Figure 1

An ex vivo screen identifies compounds that inhibit the growth of metastatic OS.

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An ex vivo screen identifies compounds that inhibit the growth of metast...
(A) Outline of the PuMA screen. (B) Left: 96-well plate of lung explants seeded with metastatic OS cells. Center, left: magnified view of 4 individual wells. Fluorescence image of a lung explant seeded with GFP+ OS cells (top center) and corresponding false colored image used for quantification (top right). Bottom center: ×40 magnification of H&E-stained, control-treated lung section after 14 days in PuMA explant culture. Boxed region highlights area of extensive OS cell growth. Bottom right: ×200 magnification of boxed region. (C) Distribution of 112 of the compounds tested, according to class. (D) Fluorescence image of a 96-well plate of lung explants treated for 14 days with 2 doses (high and low) of each compound or vehicle control (DMSO, white boxes). Called hits are boxed in red. Each row (M1–M8) is from a single mouse. (E) Dot plot showing results of all compounds tested at all doses. The dashed line corresponds to 90% reduction of GFP+ area compared with DMSO controls after 14 days of treatment in the PuMA model.