Reduction of nitric oxide level enhances the radiosensitivity of hypoxic non-small cell lung cancer

Cancer Sci. 2011 Dec;102(12):2150-6. doi: 10.1111/j.1349-7006.2011.02095.x. Epub 2011 Oct 12.


The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (E-TKI) resistance has emerged as an important clinical issue. To overcome this resistance, researchers have examined different modalities, either for use as a monotherapy or in combination with E-TKI therapy. In the present study, we investigated whether a decrease in nitric oxide (NO) levels affects the radiosensitization of non-small cell lung cancer (NSCLC) cell lines. A549 and H3255 NSCLC cells were examined. They were subjected to hypoxic conditions and monotherapy, or combined therapy using radiation and N(G) -monomethyl-l-arginine, monoacetate (LNMMA). Reductions in nitric oxide levels enhanced the radiosensitivity of both cell lines and significantly reduced the expression of both hypoxia-inducible factor-1α (HIF-1α) and EGFR in H3255 cells compared to A549 cells. Since NO is significantly associated with cell metabolism, we measured the levels of pyruvate dehydrogenase kinase-1 (PDK-1), reactive oxygen species, and oxygen and observed that the expression of PDK-1 was significantly reduced. This reduction was seen simultaneously after the silencing of HIF-1α; however, not following LNMMA treatment. The oxygen concentration was significantly increased in the treated cells, and their viability decreased in parallel. Reactive oxygen species were decreased after LNMMA and radiation treatment. Adding EGFR-TKI to cells with reduced NO levels further suppressed cell viability when combined with radiation. This study suggests that a reduction in the NO level might substantially overcome the radioresistance of mutant NSCLC cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects
  • Carcinoma, Non-Small-Cell Lung / metabolism*
  • Carcinoma, Non-Small-Cell Lung / radiotherapy
  • Cell Hypoxia / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • ErbB Receptors / antagonists & inhibitors
  • ErbB Receptors / biosynthesis
  • ErbB Receptors / metabolism*
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / genetics
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / radiotherapy
  • Nitric Oxide / metabolism*
  • Oxygen / analysis
  • Protein Serine-Threonine Kinases / biosynthesis
  • Pyruvate Dehydrogenase Acetyl-Transferring Kinase
  • RNA Interference
  • RNA, Small Interfering
  • Radiation Tolerance / drug effects*
  • Reactive Oxygen Species / metabolism
  • omega-N-Methylarginine / administration & dosage
  • omega-N-Methylarginine / pharmacology


  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Pyruvate Dehydrogenase Acetyl-Transferring Kinase
  • RNA, Small Interfering
  • Reactive Oxygen Species
  • omega-N-Methylarginine
  • Nitric Oxide
  • ErbB Receptors
  • Protein Serine-Threonine Kinases
  • Oxygen