TOP2A expression predicts responsiveness to carfilzomib in myeloma and informs novel combinatorial strategies for enhanced proteasome inhibitor cell killing

Abstract

Microarray was utilized to determine if a genetic signature associated with resistance to carfilzomib (CFZ) could be identified. Twelve human myeloma (MM) cell lines (HMCLs) were treated with CFZ and a cell-viability profile was assessed categorizing HMCLs as sensitive or resistant to CFZ. The gene expression profiles (GEP) of untreated resistant versus sensitive HMCLs revealed 29 differentially expressed genes. TOP2A, an enzyme involved in cell cycle and proliferation, was overexpressed in carfilzomib-resistant HMCLs. TOP2A protein expression levels, evaluated utilizing trephine biopsy specimens acquired prior to treatment with proteasome inhibitors, were higher in patients failing to achieve a response when compared to responding patients. Logistic-regression analysis confirmed that TOP2A protein expression was a highly significant predictor of response to PIs (AUC 0.738). Further, the combination of CFZ with TOP2A inhibitors, demonstrated synergistic cytotoxic effects in vitro, providing a rationale for combining topoisomerase inhibitors with CFZ to overcome resistance in MM.

Keywords:

• Multiple myeloma
• TOP2A
• carfilzomib
• proteasome inhibition
• gene expression profile

Acknowledgements

The authors acknowledge Lavinia Gordon (Australian Genomics Research Facility, Melbourne) for the microarray analysis. We thank the Monash Histology Platform, Department of Anatomy and Developmental Biology, Monash University, for the scientific and technical assistance.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

AR planned and performed experiments, collected and analyzed the data, wrote the manuscript. TK and AS designed the study, contributed to the planning of experiments and manuscript preparation. AR, TK, AS, IS and SM interpreted the data. JR performed the logistic regression analysis and has critically revised the manuscript. SM and MR contributed to the planning of experiments. MC revised the microarray data and provided the heatmap. IS, KB and JH performed immunostaining observation. IS and JH contributed to the generation of data. FD, RR, FS, AV contributed to the data interpretation. All authors approved the final version of the manuscript for submission.

Additional information

Funding

This work was supported by the University of Bari ‘Aldo Moro’ (Italy) - Medical Oncology Residency Program. Amgen has partially funded this work (grant awarded to Andrew Spencer). The company had no input to the preparation of this manuscript at any stage.