Preclinical Characterization of Novel Chordoma Cell Systems and Their Targeting by Pharmocological Inhibitors of the CDK4/6 Cell-Cycle Pathway

Abstract

Chordomas are tumors that arise at vertebral bodies and the base of the skull. Although rare in incidence, they are deadly owing to slow growth and a lack of effective therapeutic options. In this study, we addressed the need for chordoma cell systems that can be used to identify therapeutic targets and empower testing of candidate pharmacologic drugs. Eight human chordoma cell lines that we established exhibited cytology, genomics, mRNA, and protein profiles that were characteristic of primary chordomas. Candidate responder profiles were identified through an immunohistochemical analysis of a chordoma tissue bank of 43 patients. Genomic, mRNA, and protein expression analyses confirmed that the new cell systems were highly representative of chordoma tissues. Notably, all cells exhibited a loss of CDKN2A and p16, resulting in universal activation of the CDK4/6 and Rb pathways. Therefore, we investigated the CDK4/6 pathway and responses to the CDK4/6-specific inhibitor palbociclib. In the newly validated system, palbociclib treatment efficiently inhibited tumor cell growth in vitro and a drug responder versus nonresponder molecular signature was defined on the basis of immunohistochemical expression of CDK4/6/pRb (S780). Overall, our work offers a valuable new tool for chordoma studies including the development of novel biomarkers and molecular targeting strategies. Cancer Res; 75(18); 3823-31. Ó2015 AACR.

Effective molecular targeting of CDK4/6 and IGF-1R in a rare FUS-ERG fusion CDKN2A-deletion doxorubicin-resistant Ewing's sarcoma patient-derived orthotopic xenograft (PDOX) nude-mouse model

“…Incidence of CDKN2A loss in tumors of Ewing's sarcoma was reported to be relatively frequent with 11.2%. Palbociclib (PD0332991), a CDK4/6 inhibitor, had shown treatment efficacy for ovarian cancer, glioblastoma, and chordoma cell lines with CDKN2A loss [8–10]. Recently, palbociclib treatment efficacy for a patient with metastatic breast cancer with CDKN2A loss has been described [34].…”

“…Palbociclib, a small-molecule inhibitor of cyclin-dependent kinases 4 and 6 [8–10], was recently approved by the FDA for HER2-negative breast cancer. CDKN2A (p16) is a negative regulator of CDK 4 and 6.…”

HOXA7, HOXA9, and HOXA10 are differentially expressed in clival and sacral chordomas

“…Hence, we analysed whether the clivus chordoma cell lines lack the typical gain of 7p, as explanation of a lower expression of HOXA cluster genes compared to sacral chordoma cell lines. Two of three clivus cell lines showed a gain of 7p fitting to published data on five of six sacral chordoma cell lines 19 . Therefore, the downregulation of the described HOX genes is not caused by a loss of chromosomal material.…”

“…Overexpression of epidermal growth factor receptors (EGFR) has been reported to be a frequent event in chordoma 11–14 and inhibition of the EGF receptor 1 has a significant effect on cellular growth 15, 16 . As the majority of chordomas show a deletion of the tumour suppressor gene CDKN2A (encoding for the protein p16) 17, 18 , we provided evidence that the CDK4/6 inhibitor palbociclib may be a promising therapeutic option for chordoma treatment 19 . Up to now, none of these strategies have made it to clinical usage.…”

“…Another continuous chordoma cell lines, MUG-CC1 (Clivus) was contributed by Beate Rinner 37 . UM-Chor1 (Clivus) and the sacral chordoma cell line MUG-Chor1 51 were provided by the Chordoma Foundation (www.chordomafoundation.org), the other sacral cell lines U-CH1, U-CH2, U-CH3, U-CH6, U-CH7, U-CH10, U-CH11, and U-CH12 were established at the Institute of Pathology, University Hospital Ulm, as previously described 19, 36, 52 . All cell lines were cultured applying the same protocol as mentioned above.…”