Effection And The Mechanism Of Sorafenib On Radiosensitivity In Human Hepatocellular Cell Line SMMC-7721

Objectives: To investigate whether sorafenib can enhance radiosensitivity and the possiblemechanisms of sorafenib-mediated radiosensitization in human hepatocellular carcinomacell line SMMC-7721.Methods: MTT assay was used to detect the influence of sorafenib on cell proliferationcapacity in human hepatocellular carcinoma cell line SMMC-7721. The radiosensitizationof sorafenib in SMMC-7721was evaluated by clonogenic assay, and immunofluorescencewas applied for DNA double-strand break detection in SMMC-7721cell nuclear afterdifferent intervention, western blot assay was applied to detect the expression of protein,such as total ERK, total AKT, phosphorylated ERK and phosphorylated AKT. We usedRas/Raf/MEK/ERK signaling pathway specific inhibitor U0126and PI3K/AKT/mTORsignaling pathway specific inhibitor LY294002pretreat cells, then evaluated theradiosensitivity of U0126and LY294002by clonogenic assay.Results: Our results clearly showed that sorafenib inhibited cell proliferation in humanhepatocellular cell line SMMC-7721in a does-dependent manner with the IC50of27.853.018μM after24hours interference. Sorafenib injection1h before the radiationtreatment resulted in radiosensitization with an enhancement ratio of1.57. More DNAdouble-strand breaks could be detected in sorafenib plus radiation group when comparedwith the radiation alone group. Furthermore, sorafenib associated with radiation couldinhibit cell proliferation more significantly than radiation alone. Sorafenib pretreatment led to decreased expression levels of phosphorylated ERK and phosphorylated AKT inSMMC-7721cells after exposed to radiation. Interestingly, pretreatment ofRas/Raf/MEK/ERK signaling inhibitor U0126has a similar effect as that of sorafenibpretreatment in hepatocellular carcinoma cells, whereas pretreatment of PI3K/AKT/mTORsignaling inhibitor LY294002in the same cells has no effect on radiosensitization.Conclusions: Sorafenib significantly increased the sensitivity of SMMC-7721cells toradiation might through inhibiting or delaying the repair of DNA double-strand breaks andinhibiting cell proliferation. According to the result of the experiment, theRas/Raf/MEK/ERK signaling pathway may be the critical pathway responsible forradiosensitivity of sorafenib.