title: An in-vitro tumour microenvironment model using adhesion to type I collagen reveals Akt-dependent radiation resistance in renal cancer cells.
abstract: BACKGROUND
  Renal cell carcinoma (RCC) is considered resistant to ionizing radiation. Recently, the extracellular matrix (ECM) has been shown to play a role in both drug resistance and radiation resistance (RR). While fibronectin has been extensively investigated in the context of RR, the role of type I collagen [col(I)], a principal constituent of the ECM in tumour metastases, in RR of RCC is unknown.
  
  
  METHODS
  RCC cell adhesion to matrix was studied via pre-coating a variety of ECM glycoproteins onto plates. Cancer cell apoptosis and cell cycle were evaluated with flow cytometry using annexin V and propidium iodide stains, respectively. Activation of cellular survival signalling was analysed with western blots, and specific molecular inhibitors were correspondingly employed to block signalling. Hypoxia (<1%) was induced via N(2)/CO(2) gas flow in a specialized chamber.
  
  
  RESULTS
  While adherence to col(I) enhanced RCC cell proliferation in general, col(I) and fibronectin, but not fibrinogen, could confer specific anti-apoptotic RR to RCC cells. The radioprotective effect of col(I) was maintained during both hypoxia/reoxygenation and normoxia conditions. In contrast to intact col(I), micronized col(I), lacking the natural fibrillar structure, was not radioprotective. The effect of col(I) in RCC cells is mediated via attenuation of apoptosis rather than cell cycle redistribution, involving the PI3 kinase/Akt pathway but not the MAP kinase pathway.
  
  
  CONCLUSIONS
  Adherence to col(I) appears to be a relevant environmental cue enhancing RR in RCC cells, Akt dependently. Our results support inhibition of the PI3-kinase/Akt pathway as a radiosensitizing approach.
authors.affiliation: Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Lina
authors.initials: L
authors.lastname: Krasny
authors.forename: Nilly
authors.initials: N
authors.lastname: Shimony
authors.forename: Keren
authors.initials: K
authors.lastname: Tzukert
authors.forename: Raphael
authors.initials: R
authors.lastname: Gorodetsky
authors.forename: Shimon
authors.initials: S
authors.lastname: Lecht
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Nettelbeck
authors.forename: Yosef S
authors.initials: YS
authors.lastname: Haviv
mesh_terms: D002292:Carcinoma, Renal Cell / Q000473:pathology* / Q000532:radiotherapy*; D002448:Cell Adhesion; D024042:Collagen Type I; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D051058:Oncogene Protein v-akt / Q000502:physiology*; D017211:Treatment Failure; D014407:Tumor Cells, Cultured / Q000528:radiation effects
chemical_list: D024042:Collagen Type I; D051058:Oncogene Protein v-akt