Targeting of cell survival genes using small interfering RNAs (siRNAs) enhances radiosensitivity of Grade II chondrosarcoma cells

J Orthop Res. 2007 Jun;25(6):820-8. doi: 10.1002/jor.20377.


The main treatment for chondrosarcoma is surgical resection with a wide margin. However, there are certain chondrosarcomas, such as those found in the pelvis and the spine, which cannot be resected adequately with surgery alone. Unfortunately, most chondrosarcomas are resistant to radiation and chemotherapy. Radiation and chemotherapy are thought to kill chondrosarcoma cells by inducing apoptosis, or programmed cell death. In this article, we hypothesize that antiapoptotic gene silencing enhances radiosensitivity in chondrosarcoma cells by facilitating apoptotic pathways. We knocked down antiapoptotic genes in chondrosarcoma cells using small interfering RNAs (siRNAs). Two well-established Grade II human chondrosarcoma cell lines were pretreated with siRNAs that specifically target mRNAs for Bcl-2, Bcl-xL, or XIAP. The cells were then treated with radiation. Cell death was assessed by flow cytometry. Cell survival and proliferation were measured by clonogenic survival assays. Chondrosarcoma cells exhibited radioresistance and increased the expression of Bcl-2, Bcl-xL, and XIAP in response to radiation. When one of the Bcl-2, Bcl-xL, or XIAP genes was silenced with the corresponding siRNA, radiosensitivity increased up to 9.2-fold (p < 0.05). When two out of the three antiapoptotic mRNAs were knocked down simultaneously, there was an 11.3-fold increase in cell death after radiation (p < 0.05). Our findings support a novel therapeutic concept that gene silencing may be used as a molecular adjuvant therapy for radioresistant sarcomas.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / genetics*
  • Apoptosis / radiation effects*
  • Apoptosis Regulatory Proteins / genetics*
  • Bone Neoplasms / genetics
  • Bone Neoplasms / pathology*
  • Bone Neoplasms / radiotherapy
  • Cell Line, Tumor
  • Cell Survival / genetics
  • Cell Survival / radiation effects
  • Chondrocytes / cytology
  • Chondrocytes / radiation effects
  • Chondrosarcoma / genetics
  • Chondrosarcoma / pathology*
  • Chondrosarcoma / radiotherapy
  • Gene Expression Regulation, Neoplastic / genetics
  • Gene Expression Regulation, Neoplastic / radiation effects
  • Humans
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / pharmacology*
  • Radiation Tolerance / genetics
  • X-Linked Inhibitor of Apoptosis Protein / genetics
  • bcl-X Protein / genetics


  • Apoptosis Regulatory Proteins
  • BCL2L1 protein, human
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • RNA, Small Interfering
  • X-Linked Inhibitor of Apoptosis Protein
  • XIAP protein, human
  • bcl-X Protein