Activation of Sonic Hedgehog Signaling Is Associated with Human Osteosarcoma Cells Radioresistance Characterized by Increased Proliferation, Migration, and Invasion

Abstract

BackgroundRadioresistance restricts the application of radiotherapy in human osteosarcoma (OS). This study investigated the molecular mechanism of radioresistance in OS, which may provide clues to finding ideal targets for genetic therapy.Materila/MethodsThe human OS cell line MG63 was employed as parent cells. After repeat low-dose X-ray irradiation of MG63, the radioresistant OS cell line MG63R was produced. Colony formation assay was used to assess the radioresistance. Cell viability was evaluated by CCK-8 assay. Flow cytometry was used to detect cell apoptosis, and wound healing assay was used to evaluate invasive capacity. The nuclear translocation was evaluated by fluorescent immunohistochemistry. Protein expression levels were assessed by Western blotting. Specific siRNA against Shh was used to silence Shh.ResultsMore survival colony formation, elevated cell viability, less cell apoptosis, and increased wound closure were found in MG63R than in MG63 cells exposed to irradiation. The nuclear translocation of Gli, expression levels of Shh, Smo, Ptch1, Bcl2, active MMP2, and active MMP9 were increased in MG63R cells compared with MG63 cells. Transfection of Shh-siRNA suppressed expression levels of Shh, Smo, Ptch1, Bcl2, active MMP2, and active MMP9, as well as the nuclear translocation of Gli in MG63R cells. The cell viability, survival colony formation, and wound closure were impaired, whereas cell apoptosis was increased, in siRNA-transfected MG63R cells than in control MG63R cells exposed to irradiation.ConclusionsActivation of Shh signaling was involved in radioresistance of OS cells. Blocking this signaling can impair the radioresistance capacity of OS cells.

Hedgehog Signaling in Lung Cancer: From Oncogenesis to Cancer Treatment Resistance

“…This may suggest that Shh acts in a paracrine fashion in response to radiotherapy [ 95 , 96 ]. Similar in vitro results were observed in head and neck squamous carcinoma cells [ 138 , 143 ]. These authors also generated orthotopic xenograft tumors in nude mice using the head and neck carcinoma cells.…”

“…Cancer cells treated by radiotherapy present an activation of Shh pathway. A radioresistant osteosarcoma cell line clearly showed upregulation of Hh pathway and inhibition of Shh impaired its proliferation and invasive ability [ 138 ]. In glioma, RNAi against Histone deacetylase (HDAC) or a natural compound curcumin both seem to induce radiosensitivity whose actions depended on Shh pathway [ 139 , 140 ].…”

<p>Role of Hippo/YAP signaling in irradiation-induced glioma cell apoptosis</p>

“…13 It is well documented that pathways induced tumor cell excessive proliferation and defective apoptosis account for the major mechanisms of radioresistance in cancer cells. [14][15][16] Therefore, here, we explored the roles of Hippo/YAP signaling in glioma cell proliferation and apoptosis under irradiation exposure. We report a new effective manner that downregulation of YAP can significantly enhance the radiosensitivity of glioma cells.…”

Craniofacial Osteosarcoma—Pilot Study on the Expression of Osteobiologic Characteristics and Hypothesis on Metastasis

“…However, an increased radioresistance of osteosarcoma cells was reported to be associated with high Hh activation and could be reversed by Hh inhibition (52,53). In this regard, Hh inhibition might also be considered for new studies evaluating multimodal treatment including radiotherapy in COS.…”