title: NVP-BEZ-235 enhances radiosensitization via blockade of the PI3K/mTOR pathway in cisplatin-resistant non-small cell lung carcinoma.
abstract: BACKGROUND
  Most drug resistant cancer cells also develop resistance to radiation therapy. In this study, we hypothesized that the dual inhibitor of phosphatidylinositol-3 kinase/mammalian target of rapamycin, NVP-BEZ-235, could potentially enhance radiosensitization in cisplatin-resistance (CDDP-R) non-small cell lung cancer (NSCLC) cells by disabling autophagy as a mechanism of self-preservation.
  
  
  METHODS
  We used both in vitro and in vivo approaches, including clonogenic assays, Western blotting, molecular analyses of autophagy and apoptosis, a xenograft model of tumor growth, and immunohistochemical analysis.
  
  
  RESULTS
  Basal p-Akt, p-mTOR and p-S6R proteins were enhanced in CDDP-R NSCLC cells. CDDP-R-resistant NSCLC cells are less radiation sensitive in comparison to parental cells (DER=0.82, p=0.02); BEZ-235 enhanced the radiosensitivity (DER=1.2, p=0.01). In addition, combining BEZ-235/RT showed a dramatic tumor growth delay in a mouse xenograft model. Immunohistochemistry showed that combination therapy yielded 50% decrease in caspase-3 activity. Moreover, cell proliferation was reduced by 87.8% and vascular density by 86.1%. These results were associated with a downregulation of PI3K/mTOR signaling pathway and an increase in autophagy.
  
  
  CONCLUSIONS
  These findings may be utilized as a novel strategy to enhance the efficacy of radiation therapy in drug-selected non-small cell lung cancer exhibiting radioresistance.
authors.affiliation: Department of Pediatric Surgery, Vanderbilt University School of Medicine, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Kwang Woon
authors.initials: KW
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Carey J
authors.initials: CJ
authors.lastname: Myers
authors.affiliation: Department of Hematology/Oncology, Vanderbilt University School of Medicine, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Dae Kwang
authors.initials: DK
authors.lastname: Jung
authors.affiliation: Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Bo
authors.initials: B
authors.lastname: Lu
keywords: NSCLC; autophagy; cisplatin resistance; mTOR; radiosensitization