Combination Effects of Sorafenib with Ionizing Radiation on Orthotopic Human Oral-Bearing Mice Model
Hui-Yen Chuang, National Yang-Ming University
Objectives:
Oral squamous cell carcinoma (OSCC) is one of the leading cancers worldwide, especially in Asia. Most patients with OSCC have extremely poor quality of life due to bone invasion. In this study, we aimed to study whether sorafenib, a multikinase inhibitor, could enhance the therapeutic efficacy of radiotherapy (RT) and decrease the bone erosion using an in situ human OSCC-bearing mouse model. The underlying mechanisms involved in augmenting treatment outcomes were studied both in vitro and in vivo. Furthermore, the tumor progression and facial bone integrity were visualized by in vivo bioluminescent imaging (BLI) and micro-CT, respectively.
Materials and Methods:
Human oral carcinoma SAS cell line was transfected with pCMV-luc2, and renamed as SAS/luc2. Expressions of NF-kB and its downstream proteins and NF-kB activity in various groups (i.e. control, RT, sorafenib and combination) were studied by Western blotting and EMSA assay. For in vivo studies, 1.5 x 106 SAS/luc2 cells were inoculated into the right masseter muscle of six-week-old male nude mice. Two weeks later, mice were randomly separated into six groups: (a) normal (i.e. no tumor); (b) control; (c) sorafenib alone; (d) radiation alone; (e) pretreatment (i.e. sorafenib prior to radiation), (f) concurrent treatment. The tumor growth and body weight were tracked by bioluminescent imaging (BLI) for another three weeks. Five weeks after tumor cell inoculation, mice were sacrificed, and subjected to micro-CT scanning to evaluate facial bone destruction of mice. The tumors were harvested for ex-vivo Western blot, ex-vivo EMSA, and IHC staining for mechanistic studies.
Results:
In vivo BLI showed that tumor growth was suppressed most significantly in the combination groups (i.e. pretreatment and concurrent groups), and are strongly related to the down-regulation of NF-kB and its effector proteins as detected by ex vivo EMSA and Western blotting. Notably, the expression level of p65 in tumor tissues of mice was suppressed most significantly in the pretreatment group. No or minor damage in the mandible and zygoma bones was found in the combination groups as demonstrated by reconstructed micro-CT images.
Conclusion:
The better control of human oral carcinoma could be achieved by combination of sorafenib with ionizing radiation, especially with the pretreatment of sorafenib. The underlying mechanism may through the suppression of NF-kB and its downstream effector proteins. In addition, bone destruction could also be reduced by the combination treatment, indicating that this may be a potential treatment strategy for human OSCC in clinic.
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