Therapeutic efficacy of cyclin-dependent kinase inhibition in combination with ionizing radiation for lung cancer

Abstract

Purpose

To evaluate the therapeutic efficacy of cyclin-dependent kinase (CDK) inhibition in combination with ionizing radiation for lung cancer.

Materials and methods

Human lung adenocarcinoma (A549) and squamous cell carcinoma (H520) cells were used to evaluate the therapeutic efficacy of CDK inhibition in combination with ionizing radiation in vitro using colony formation assay, γH2AX immunofluorescence staining, western blotting, and cell cycle phase analysis. We also performed in vivo evaluations of ectopic tumor growth.

Results

In vitro pretreatment with the CDK inhibitor, seliciclib, before irradiation significantly decreased the survival of A549 and H520 cells in a dose-dependent manner. Although CDK inhibition alone did not increase the intensity of γH2AX foci, its combination with ionizing radiation increased DNA double-strand breaks, as shown by γH2AX immunofluorescence staining and western blotting. The combination of CDK inhibition and ionizing radiation-induced G2/M arrest and increased apoptosis, as evidenced by the increased proportion of cells in G2/M arrest, subG1 apoptotic population, and expression of apoptotic markers (cleaved PARP-1 and cleaved caspase-3). Mechanistic studies showed reduced expression of cyclin A with combined treatment, indicating cell cycle shifting effects. An in vivo xenograft model showed that the combination of CDK inhibition and ionizing radiation delayed xenograft tumor growth, and increased the proportion of cleaved PARP-1- and cleaved caspase-3-positive cells, compared to either treatment alone.

Conclusions

We provide preclinical tumoricidal evidence that the combination of CDK inhibition and ionizing radiation is an efficacious treatment for lung cancer.

Keywords:

• Apoptosis
• cell cycle
• cyclin-dependent kinase
• ionizing radiation
• lung cancer

Acknowledgments

We thank the staff of the core laboratory in the Department of Medical Research at the National Taiwan University Hospital for their technical support.

Disclosure statement

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

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article.

Additional information

Funding

This work was supported by the National Taiwan University Hospital, under Grant NTUH 110-N4983, and the Ministry of Science and Technology of Taiwan, under Grant 110-2314-B-002-138-MY3. The funders had no role in study design, data collection, and analysis, decision to publish, or preparation of the manuscript.

Notes on contributors

Jenny Ling-Yu Chen

Jenny Ling-Yu Chen is an attending physician in radiation oncology at the National Taiwan University Hospital and an assistant professor in the Department of Radiology at the National Taiwan University College of Medicine.

Chun-Kai Pan

Chun-Kai Pan is a research assistant in the Department of Medical Research at the National Taiwan University Hospital.

Li-Cheng Lin

Li-Cheng Lin is a research assistant in the Department of Medical Research at the National Taiwan University Hospital.

Ching-Yi Tsai

Ching-Yi Tsai is a Ph.D. student at the Institute of Toxicology, National Taiwan University College of Medicine.

Ching-Ying Kuo

Ching-Ying Kuo is an assistant professor in the Department of Clinical Laboratory Sciences and Medical Biotechnology at the National Taiwan University College of Medicine.

Yu-Sen Huang

Yu-Sen Huang is an attending physician in medical imaging at the National Taiwan University Hospital and an assistant professor in the Department of Radiology at the National Taiwan University College of Medicine.

Yu-Li Lin

Yu-Li Lin is an associate research fellow in the Department of Medical Research at the National Taiwan University Hospital.