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Open Access Research article

Saikosaponin-d increases the radiosensitivity of smmc-7721 hepatocellular carcinoma cells by adjusting the g0/g1 and g2/m checkpoints of the cell cycle

Bao-Feng Wang1, Zhi-Jun Dai1, Xi-Jing Wang1*, Ming-Hua Bai1, Shuai Lin1, Hong-Bing Ma1, Ya-Li Wang1, Ling-Qin Song1, Xiu-Long Ma1, Ying Zan1, Wei-Li Min1 and Yan-An Cheng2

Author Affiliations

1 Department of Oncology, Second Affiliated Hospital of Medical School, Xi’an Jiaotong University, Xi’an 710004, P.R. China

2 Department of Infectious Disease, Second Affiliated Hospital of Medical School, Xi’an Jiaotong University, Xi’an 710004, P.R. China

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BMC Complementary and Alternative Medicine 2013, 13:263  doi:10.1186/1472-6882-13-263

Published: 12 October 2013

Abstract

Background

Saikosaponin-d (SSd), a monomer terpenoid purified from the Chinese herbal drug Radix bupleuri, has multiple effects, including anticancer properties. However, the effect of SSd on tumors exposed to radiation is largely unknown. To investigate the radiosensitizing effect of SSd and its possible mechanism, we combined SSd with radiation therapy to treat SMMC-7721 hepatocellular carcinoma cells under oxia and hypoxia.

Methods

Cell growth, apoptosis, and cell cycle distribution were examined after treatment with SSd alone, radiation alone, and their combinations under oxia and hypoxia. The protein and mRNA levels of p53, Bcl2, and BAX were measured using western blot analysis and RT-PCR, respectively.

Results

Treatment with SSd alone and radiation alone inhibited cell growth and increased apoptosis rate at the concentration used. These effects were enhanced when SSd was combined with radiation. Moreover, SSd potentiated the effects of radiation to induce G0/G1 arrest in SMMC-7721 cells, and reduced the G2/M-phase population under hypoxia. However, under oxia, SSd only potentiated the effects of radiation to induce G0/G1 arrest, but not G2/M-phase arrest. These effects of SSd alone, radiation alone, and their combination, were accompanied by upregulated expression of p53 and BAX and downregulation of Bcl2 expression under oxia and hypoxia.

Conclusion

SSd potentiates the effects of radiation on SMMC-7721 cells; thus, it is a promising radiosensitizer. The radiosensitizing effect of SSd may contribute to its effect on the G0/G1 and G2/M checkpoints of the cell cycle.