Human papillomavirus 16 E6 increases the radiosensitivity of p53-mutated cervical cancer cells, associated with up-regulation of aurora A

Abstract

Purpose: To examine the effect of the human papillomavirus (HPV) type 16-E6 (HPV ‘early’ gene) oncoprotein on in vitro radiosensitivity of HPV-negative/p53 mutant C33a cervical cancer cells.

Methods and materials: The human cervical cancer cell line C33a was stably transfected with either the HPV16 E6 cDNA cloned into the vector pcDNA™3.0 (C33aE6) or the empty-vector control (C33aV). Radiosensitivity, DNA damage, and cell cycle measurements were made using standard clonogenic assays, immunofluorescent assessment of nuclear histone H2AX phosphorylated on serine-139 (γ-H2AX) foci, and flow cytometry. Western immunoblotting and fluorescence confocal microscopy were used to analyse the changes in cellular proteins. Real-time polymerase chain reaction (PCR) was used to compare levels of aurora A mRNA.

Results: Compared to C33aV cells, C33aE6 cells showed enhanced radiation cell killing. This was associated with a large amount of polyploidy which was followed by late cell death in C33aE6 cells. Aurora A was highly expressed in C33aE6 cells at pre- and post-irradiation times compared to C33aV cells. Silencing aurora A resulted in a reduced amount of residual γ-H2AX foci in C33aE6 cells, and diminished the difference in radiosensitivity between the C33aE6 and C33aV cells.

Conclusion: Our in vitro results indicate that genetic instability could be augmented in the HPV-infected cancer cells by up-regulation of aurora A, especially against a background of dysfunctional p53. Further studies are needed to examine whether aurora A could be a viable therapeutic target in HPV-related tumours.

Keywords:

• Human papillomavirus (HPV) 16 E6
• aurora A
• p53
• radiosensitivity
• cervical cancer

Acknowledgements

This work was supported by the National Cancer Center Grant 1010870-1, Goyang, Korea. This work was done as a part of Co-ordinated Research Project E33024 (Optimising treatment of cervix cancer using radiotherapy and analysis of virally-associated cellular resistance), International Atomic Energy Agency, Vienna, Austria.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.