Circadian clock gene BMAL1 inhibits the proliferation and tumor-formation ability of nasopharyngeal carcinoma cells and increases the sensitivity of radiotherapy

ABSTRACT

BMAL1 is a core circadian clock gene that is expressed rhythmically in a variety of tumor cells and is related to cancer cell proliferation and chemoradiotherapy sensitivity. Radiotherapy plays an important role in the treatment of nasopharyngeal carcinoma (NPC). However, the rhythmicity of BMAL1 in NPC, as well as its precise role in radiotherapy, remains unclear. We assessed changes in BMAL1 expression over 48 h in NPC cells and normal nasopharyngeal epithelial cells NP69 using real-time quantitative polymerase chain reaction (RT-PCR) and western blotting (WB). Then, we induced the overexpression and knocked-down the levels of BMAL1 in NPC cells, and subsequently used Cell Counting Kit-8 assays to assess the proliferation of NPC cells. Xenograft tumour growth was used to evaluate the effect of BMAL1 in vivo. Immunohistochemical staining was used to detect the expression of BMAL1 protein in transplanted tumors. Gene Set Enrichment Analysis (GSEA) was performed to explore the biological signaling pathway. Finally, RT-PCR and WB were used to detect the expressions of BMAL1, p53 and p21. The results showed that the mRNA expression levels of circadian clock gene BMAL1 fluctuated rhythmically with time, and the expression levels of BMAL1 also changed depending on the protein levels in NPC and NP69 cells. Overexpression of BMAL1 inhibited the proliferation of NPC cells, while knockdown BMAL1 had the opposite effects. In a xenograft model, we observed that the upregulation of BMAL1 inhibited tumor growth and enhanced the sensitivity of NPC cells to radiotherapy. Ultimately, the downregulation of BMAL1 promoted tumor growth and decreased radiosensitivity. GSEA analysis suggested that BMAL1 significantly affected the p53 pathway. Overexpression of BMAL1 promoted the expression of p53 and p21, while the knockdown of BMAL1 inhibited the expression of p53 and p21. We speculate that BMAL1 has the potential to be a prognostic biomarker and therapeutic target for NPC.

KEYWORDS:

• Nasopharyngeal carcinoma
• circadian clock gene
• BMAL1
• circadian rhythm
• radiosensitivity

Acknowledgements

The authors would like to thank the following sources of funding support. This research was supported in part by grants from The National Natural Science Foundation of China under Grant number 82060556; Department of Science and Technology, Guizhou Province under Grant Number [2018] 2755; Ordinary Colleges and Universities Youth Science and Technology Talent Growth Project, Guizhou Province under Grant number [2021] 187; The Health Commission Science and Technology Fund, Guizhou Provincial under grant number gzwkj2021-050; Guizhou Medical University 2021 National Foundation Cultivation Project [20NSP041], and the hospital-level science and technology project of Guizhou Cancer Hospital under Grant number YJ2019-33.

Disclosure statement

The authors report no conflicts of interest. Only the principal investigators are responsible for the content and writing of the article.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [82060556]; Guizhou Medical University 2021 National Foundation Cultivation Project [[20NSP041]]; Health Commission Science and Technology Fund, Guizhou Provincial [gzwkj2021-050]; Ordinary Colleges and Universities Youth Science and Technology Talent Growth Project, Guizhou Province [[2021] 187]; The National Natural Science Foundation of China [81560437]; Department of Science and Technology, Guizhou Province [[2018] 2755]; The hospital-level science and technology project of Guizhou Cancer Hospital [YJ2019-33].