Differential cell death response to photodynamic therapy is dependent on dose and cell type (original) (raw)

2001, British Journal of Cancer

Photodynamic therapy (PDT) may result in either apoptotic or necrotic cell death (Noodt et al, 1999). Many stimuli may trigger apoptosis: DNA damage, tumour necrosis factor, radiation, reactive oxygen species and elevated intracellular calcium levels. These stimuli interact with mitochondria, which are thought to be key regulators of apoptosis (Susin et al, 1998), by activation of the caspase cascade. Photodynamic therapy may interact with many of these pathways but it is unclear which is responsible for triggering apoptosis following PDT. The type of response may vary according to the cell type, the physical properties and intracellular localization of the sensitizer (Noodt et al, 1999) and the PDT dose (Kessel et al, 1995). The effect of PDT dose may reflect the fact that at low doses the cellular machinery for apoptosis is activated whereas at higher doses, the apoptotic machinery is itself damaged. The effect of cell type may depend on the genetics of the cell, as neoplastic cells often have mutations affecting the apoptotic machinery. MATERIALS AND METHODS Cell lines MCF 7, Human Mammary Carcinoma (ECACC, European collection of Animal Cell Cultures, Porton Down, UK). This cell line has a wild-type p53 gene (Sharma and Srikant, 1998), but a mutation in the caspase 3 gene (Janicke et al, 1998). T47D, Human Mammary Carcinoma (ECACC). This cell line contains a mutated p53 gene (Bonsing et al, 1997). HT1197, Human Bladder Carcinoma (ECACC). This cell line contains a mutated p53 gene (Cooper et al, 1994). WRC, Walker Rat Carcinoma. This cell line contains a wildtype p53 gene (Tang et al, 1996). MVECs, Human Microvascular Endothelial Cells, derived from human adipose tissue, by the method of Hewitt and Murray (1993). Cell culture techniques All of the cell types studied were cultured in their optimal media and maintained using standard tissue culture techniques. Cell death assay: dual staining for apoptosis and necrosis