CDK4/6 inhibition presents as a therapeutic option for paediatric and adult germ cell tumours and induces cell cycle arrest and apoptosis via canonical and non-canonical mechanisms.

Abstract

BACKGROUND:

Germ cell tumours (GCTs) are the most common solid malignancies in young men. Although high cure rates can be achieved, metastases, resistance to cisplatin-based therapy and late toxicities still represent a lethal threat, arguing for the need of new therapeutic options. In this study, we analysed the potential of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors palbociclib and ribociclib (PaRi) as molecular drugs to treat cisplatin-resistant and -sensitive paediatric and adult GCTs.

METHODS:

Ten GCT cell lines, including cisplatin-resistant subclones and non-malignant controls, were treated with PaRi and screened for changes in viability (triphenyl tetrazolium chloride (XTT) assay), apoptosis rates (flow cytometry, caspase assay), the cell cycle (flow cytometry), the transcriptome (RNA-sequencing, quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and on protein level (western blot). Expression profiling was performed on paediatric and adult GCT tissues (expression microarrays, qRT-PCR, immunohistochemistry, 'The Cancer Genome Atlas' database).

RESULTS:

We demonstrate that adult GCTs highly express CDK4, while paediatric GCTs strongly express CDK6 instead. Thus, both GCT types are potentially treatable by PaRi. GCTs presented as highly sensitive towards PaRi, which caused a decrease in viability, cell cycle arrest and apoptosis. Although GCTs mainly arrested in the G1/G0 phase, some embryonal carcinoma cell lines were able to bypass the G1/S checkpoint and progressed to the G2/M phase. We found that upregulation of CDK3 and downregulation of many mitosis regulation factors, like the HAUS genes, might be responsible for bypassing the G1/S checkpoint and termination of mitosis, respectively. We postulate that GCT cells do not tolerate these alterations in the cell cycle and eventually induce apoptosis.

CONCLUSION:

Our study highlights PaRi as therapeutic options for cisplatin-resistant and -sensitive paediatric and adult GCTs.

• Authors: Margaretha A Skowron, Marieke Vermeulen, Anna Winkelhausen, Teresa K Becker, Felix Bremmer, Patrick Petzsch, Stefan Schönberger, Gabriele Calaminus, Karl Köhrer, Peter Albers, Daniel Nettersheim
• Journal: British journal of cancer (Br J Cancer) Vol. 123 Issue 3 Pg. 378-391 (08 2020) ISSN: 1532-1827 [Electronic] England
• PMID: 32418994 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Aminopyridines
• Piperazines
• Purines
• Pyridines
• CDK4 protein, human
• CDK6 protein, human
• Cyclin-Dependent Kinase 4
• Cyclin-Dependent Kinase 6
• palbociclib
• Cisplatin
• ribociclib

Topics

• Adult
• Aminopyridines (pharmacology)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Cell Survival (drug effects)
• Child
• Cisplatin (pharmacology)
• Cyclin-Dependent Kinase 4 (antagonists & inhibitors, genetics, metabolism)
• Cyclin-Dependent Kinase 6 (antagonists & inhibitors, genetics, metabolism)
• Drug Resistance, Neoplasm (drug effects)
• Female
• Gene Expression Profiling
• Gene Expression Regulation, Neoplastic (drug effects)
• Humans
• Male
• Neoplasms, Germ Cell and Embryonal (drug therapy, genetics, metabolism)
• Piperazines (pharmacology)
• Purines (pharmacology)
• Pyridines (pharmacology)
• Sequence Analysis, RNA
• Up-Regulation (drug effects)