title: Spontaneous regression of human cancer cells in vitro: potential role of disruption of Cdk1/Cdk4 co-expression.
abstract: BACKGROUND
  Although well-acknowledged in vivo, spontaneous death of cancer cells in vitro is less widely appreciated.
  
  
  METHODS
  Colony formation was studied in untreated control plates of standard clonogenic assays and measurements of actual and potential doubling times performed in asynchronous cultures of human cancer cells lines. Western blotting of lung large cell carcinoma, COR-L23 cells actively undergoing spontaneous cell death was also carried out.
  
  
  RESULTS
  Catastrophic disintegration of mature colonies could be seen in the untreated plates of lung large cell carcinoma, H460 and colon adenocarcinoma, SW620 human cancer cell lines and a significant cell loss factor was present in the cell lines growing as adherent cells in continuous culture. Western blotting demonstrated alterations of relative cyclin dependent kinase (Cdk)1 to Cdk4 protein expression in dying COR-L23 cells.
  
  
  CONCLUSIONS
  The phenomenon of spontaneous cell death should be considered a hallmark of cancer and may be the result of failure to stabilise unstable, fully developed cancer cells due to the disruption of Cdk1/Cdk4 co-expression in those cells.
authors.affiliation: School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, U.K. H.Warenius@soton.ac.uk
authors.forename: Hilmar
authors.initials: H
authors.lastname: Warenius
authors.forename: Leto
authors.initials: L
authors.lastname: Kyritsi
authors.forename: Ian
authors.initials: I
authors.lastname: Grierson
authors.forename: Amanda
authors.initials: A
authors.lastname: Howarth
authors.forename: Laurence
authors.initials: L
authors.lastname: Seabra
authors.forename: Mark
authors.initials: M
authors.lastname: Jones
authors.forename: Carole
authors.initials: C
authors.lastname: Thomas
authors.forename: Paul
authors.initials: P
authors.lastname: Browning
authors.forename: Rosalind
authors.initials: R
authors.lastname: White
mesh_terms: D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D018287:Carcinoma, Large Cell / Q000378:metabolism / Q000473:pathology*; D002470:Cell Survival; D003114:Colony-Forming Units Assay; D051358:Cyclin-Dependent Kinase 4 / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology*; D009365:Neoplasm Regression, Spontaneous / Q000473:pathology*; D012867:Skin / Q000166:cytology / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D016203:CDC2 Protein Kinase; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4