Anti-tumour and radiosensitising effects of PARP inhibitor on cervical cancer xenografts

Abstract

This study evaluated the radiosensitising effect of niraparib; a poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitor on HeLa cervical cancer cells in nude mice and explored its possible mechanism. Twenty-four 3–5-week-old female BALB/c nude mice, inoculated with HeLa cells into the right hind leg, were randomly assigned into eight groups with three mice per group and treated. The tumour volume was significantly reduced under niraparib + radiotherapy combination as compared to monotherapy and untreated mice. The tumour growth was significantly delayed by 23.33–39 days when treated with combination therapy (p<.05). Further, univariate analysis revealed prolonged time for tumour growth when radiotherapy was followed by niraparib (I.G.) rather than niraparib (I.P.) (p=.003). Combination therapy reduced levels of PARP-1 precursor, PARP-1 splicer, PAR and RAD51 protein with high expression of γ-H2AX/CC3 and low expression of Ki-67. Niraparib in combination with radiotherapy can enhance the formation of DNA double strand breaks in HeLa cells and up regulate the expression of γ-H2AX/CC3.

IMPACT STATEMENT

• What is already known on this subject? Asia has the highest incidence of cervical cancer (58.2%). Poly(adenosine diphosphate-ribose) polymerases (PARPs) are family of enzymes involved in single-strand break (SSB) and double-strand break (DSB) repair pathways. Niraparib is an effective inhibitor of both PARP-1 and PARP-2 and has the ability to cross the blood–brain barrier.

• What the results of this study add? Our study demonstrated that the combination of niraparib and radiotherapy can significantly enhance the cytotoxicity induced by radiotherapy. The inhibition effect of radiotherapy combined with niraparib on the tumour growth of mice was prominent, thereby establishing the radio-sensitisation activity of niraparib.

• What are the implications of these findings for clinical practice and/or further research? Niraparib can improve the cytotoxic effect of radiotherapy by increasing the formation of DSBs and up regulating the expression of apoptotic protein in HeLa cells.

Keywords:

• Cervical cancer
• PARP inhibitor
• radiotherapy
• radiotherapy sensitisation
• Niraparib

Acknowledgements

The authors would like to acknowledge Anwesha Mandal and Amit Bhat of Indegene Pvt. Ltd., India for manuscript writing and editorial support.

Author contributions

Conceptualisation: Gao Song and Qin Xue. Methodology: Gao Song, Qin Xue and Ma Qipeng. Investigation: Qin Xue, Wang Enyang, Gong Tingting, Ma Xiaolin and Ma Qipeng. Formal analysis: Qin Xue, Wang Enyang and Gong Tingting. Writing – original draft: Qin Xue and Wang Enyang. Writing – review and editing: Qin Xue, Wang Enyang, Gong Tingting, Ma Xiaolin, Ma Qipeng and Gao Song.

Ethics statement

The experiment was approved by the Ethics committee of China Medical University (2020PS660K).

Disclosure statement

The authors declare no conflict of interest.

Data availability statement

Data are available with the corresponding author on reasonable request.

Additional information

Funding

Gao Song received funding from Science and Technology Plan of Shenyang City in 2021 (Project ID:21-173-9-61).