International Journal of Radiation Biology. 2010;86(9):769-779.
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 pcDNA3.0 (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 (g-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 g-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.