Inhibition of CDK4/6 by Palbociclib Significantly Extends Survival in Medulloblastoma Patient-Derived Xenograft Mouse Models

Purpose:   <p>Bioinformatics analysis followed by in vivo studies in patient-derived xenograft models were used to identify and validate CDK 4/6 inhibition as an effective therapeutic strategy for medulloblastoma, particularly Group 3 MYC-amplified tumors which have the worst clinical prognosis.</p> <br />Experimental Design: <p>A protein interaction network derived from a Sleeping Beauty mutagenesis model of medulloblastoma was used to identify potential novel therapeutic targets.  The top hit from this analysis was validated in vivo using patient-derived xenograft models of medulloblastoma implanted subcutaneously in the flank and orthotopically in the cerebellum of mice.</p> <br />Results: <p>Informatics analysis identified the CDK4/6/CYCLIN D/RB pathway as a novel "druggable" pathway for multiple subgroups of medulloblastoma.  Palbociclib, a highly specific inhibitor of CDK4/6, was found to inhibit RB phosphorylation and cause G1 arrest in patient-derived xenograft (PDX) models of medulloblastoma.  The drug caused rapid regression of Sonic hedgehog (SHH) and MYC-amplified Group 3 medulloblastoma subcutaneous tumors and provided a highly significant survival advantage to mice bearing MYC-amplified intracranial tumors. </p> <br />Conclusions:<br />Inhibition of CDK4/6 is potentially a highly effective strategy for the treatment of SHH and MYC-amplified Group 3 medulloblastoma.

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