ABSTRACT
BACKGROUND: Although well-acknowledged in vivo, spontaneous death of cancer cells in vitro is less widely appreciated. MATERIALS AND 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. CONCLUSION: 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.
Subject(s)
CDC2 Protein Kinase/metabolism , Carcinoma, Large Cell/pathology , Cyclin-Dependent Kinase 4/metabolism , Lung Neoplasms/pathology , Neoplasm Regression, Spontaneous/pathology , Blotting, Western , Carcinoma, Large Cell/metabolism , Cell Survival , Colony-Forming Units Assay , Fibroblasts/metabolism , Flow Cytometry , Humans , Lung Neoplasms/metabolism , Skin/cytology , Skin/metabolism , Tumor Cells, CulturedABSTRACT
Tumour heterogeneity is becoming increasingly important as an obstacle to genomic and proteomic technologies designed to improve the diagnosis and treatment of human cancer. In a panel of 19 human in-vitro cancer cell lines, we show marked heterogeneity of proteomic expression of key genes responsible for the control of cell division and death. Patterns of expression of these proteins were unique for each cell line. In addition, dynamic heterogeneity of proteomic expression of Cyclin D1, Cdk1, Cdk4 and even actin was detected. The relative levels of each protein fluctuated independently from experiment to experiment separated only by short passages in tissue culture. Cdk1 and Cdk4 proteomic co-expression (Seabra, 2007) was not, however, affected by dynamic heterogeneity, or, in 4 cell lines, by treatment with D0.1 doses of CDDP. Cdk1/Cdk4 may thus provide a complex molecular target for anti-cancer drug development which is unaffected by tumour heterogeneity and is not disrupted by conventional chemotherapy.