Taraxasterol enhanced bladder cancer cells radiosensitivity via inhibiting the COX-2/PGE2/JAK2/STAT3/MMP pathway

Abstract

Purpose

Radiotherapy with bladder preservation is highly acceptable among patients bearing bladder cancer (BCa), but the occurrence of secondary tolerance (ARR) during treatment is one of the important reasons for the failure of clinical radiotherapy. COX-2 has been frequently reported to be highly expressed and associated with radio-resistance in various cancers. In this study, the feasibility of Taraxasterol (Tara) as a radiosensitizer was investigated, and the target effect of Tara on COX-2 and its underlying mechanism were explored.

Methods and materials

The toxicity of Tara toward BCa cells was detected with the MTT method and cells in response to IR or Tara + IR were compared by clone formation assay. Next, a small RNA interference system (siRNA) was employed to decrease endogenous COX-2 expression in BCa cells, and the stem cell-like features and motion abilities of BCa cells under different treatments were investigated using microsphere formation and transwell chamber assay, respectively. Meanwhile, the expression of a series of inflammation-related molecules and stem cell characteristic molecules was determined by qRT-PCR, western blot and ELISA method. In vivo studies, BCa cells were subcutaneously injected into the right flank of each male mouse. Those mice were then grouped and exposed to different treatment: Tara, IR, IR + Tara and untreated control. The volumes of each tumor were measured every two days and target proteins were detected with immunohistochemical (IHC) staining.

Results

The results show that COX-2 decline, due to COX-2 knocking-down or Tara treatment, could greatly enhance BCa cells’ radiosensitivity and significantly decrease their migration, invasion and microsphere formation abilities, companied with the reduce of JAK2, phos-STAT3, MMP2 and MMP9 expression. However, Tara could not further reduce the expression of an above molecule of cells in COX-2-deficient BCa cells. Correspondingly, Tara treatment could not further enhance those siCOX-2 BCa cells response to IR.

Conclusions

Our data support that Tara can improve the radiosensitivity of BCa cells by targeting COX-2/PGE₂. The mechanism may involve regulating STAT3 phosphorylation, DNA damage response protein activation, and expression of MMP2/MMP9.

Keywords:

• Bladder cancer
• radiosensitization
• taraxasterol
• cox-2

Authors contributions

Zhaolu Kong and Guangmin Mao designed the experiments. Quanxin Wang, Ruiqi Zhang and Yijun He performed the experiments. Quanxin Wang analyzed the data. Quanxin Wang and Zhaolu Kong wrote the manuscript. All authors reviewed the manuscript.

Disclosure statement

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

Data availability statement

The analyzed data sets generated during the study are available from the corresponding author on reasonable request.

Additional information

Funding

This work was supported by National Natural Science Foundation of China (grant no. 31870846), and Yumiao Program of Longhua Hospital (grant no. Y21003).

Notes on contributors

Quanxin Wang

Quanxin Wang, is a postgraduate at the Department of Radiobiology, Institute of Radiation Medicine, Fudan University, Shanghai, PR China.

Ruiqi Zhang

Ruiqi Zhang, is a postgraduate at the Department of Radiobiology, Institute of Radiation Medicine, Fudan University, Shanghai, PR China.

Yijun He

Yijun He, is a postgraduate at the Department of Radiobiology, Institute of Radiation Medicine, Fudan University, Shanghai, PR China.

Guangmin Mao

Guangmin Mao, is a physician at Department of Radiation Oncology, Longhua Hospital Shanghai University of Traditional Chinese Medicine, Shanghai, PR China.

Zhaolu Kong

Zhaolu Kong, PhD, is an associate researcher at the Department of Radiobiology, Institute of Radiation Medicine, Fudan University, Shanghai, PR China.