title: Enhancement of radiation sensitivity with BH3I-1 in non-small cell lung cancer.
abstract: BACKGROUND
  Anti-apoptotic proteins, such as Bcl-2 and Bcl-xL, are frequently over-expressed in human malignancies, and this is correlated with resistance to chemotherapeutic drugs and gamma- radiation. Recently identified small organic molecules capable of inhibiting Bcl-2 and/or Bcl-xL function, may enhance radiation sensitivity of cancer cells in which they are over expressed. We examined whether specific blockade of the BH3-domain binding to Bcl-xL could sensitize cancer cells to gamma- radiation.
  
  
  METHODS
  Human non-small-cell lung cancer H460 cells with wild-type p53 and H1792 cells with mutant p53 were exposed to various doses of radiation and/or BH3I-1 and for different points of time to BH3I-1 treatment. XTT and clonogenic survival assays were used to evaluate the growth-inhibitory effects of the antagonist BH3I-1, ionizing radiation or both. Western blot analysis was used to examine the cellular effect of the expression of Bcl-xL, Bax, and p53. Apoptosis and cell cycle distribution were analyzed by confocal microscopy with Hoechst 33258 staining and cytochrome c, and flow cytometry, respectively.
  
  
  RESULTS
  BH3I-1 appeared to induce a dose- and time-dependent apoptosis in H460 and H1792 cells, regardless of p53 status. After 2 days of BH3I-1 treatment, the cells that remained attached were exposed to ionizing radiation. Followed by clonogenic assay, BH3I-1 treatment enhanced the radiation sensitivity of H1792 surviving cells with mutant p53, but not in H460 cells with wild-type p53. A transient time-dependent cell cycle blockade at G2-M phase was identified for H1792 cells without subsequent modification of cell cycle distribution.
  
  
  CONCLUSIONS
  These findings suggest a potential role for the small molecule inhibitor as a novel radiation sensitizer in non-small cell lung cancer.
authors.affiliation: Department of Radiation Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada. wilsonro@cancerboard.ab.ca
authors.forename: W
authors.initials: W
authors.lastname: Roa
authors.forename: H
authors.initials: H
authors.lastname: Chen
authors.forename: A
authors.initials: A
authors.lastname: Alexander
authors.forename: S
authors.initials: S
authors.lastname: Gulavita
authors.forename: J
authors.initials: J
authors.lastname: Thng
authors.forename: X J
authors.initials: XJ
authors.lastname: Sun
authors.forename: K
authors.initials: K
authors.lastname: Petruk
authors.forename: R
authors.initials: R
authors.lastname: Moore
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy*; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D053938:DNA Fragmentation / Q000187:drug effects / Q000528:radiation effects; D005434:Flow Cytometry; D006801:Humans; D007457:Iodine Radioisotopes / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000532:radiotherapy*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D013844:Thiazoles / Q000494:pharmacology*; D045162:Thiazolidinediones
chemical_list: C503945:5-(4-bromobenzylidene)-alpha-isopropyl-4-oxo-2-thioxo-3-thazolidineacetic acid; D007457:Iodine Radioisotopes; D011838:Radiation-Sensitizing Agents; D013844:Thiazoles; D045162:Thiazolidinediones