Comparison of the cellular molecular stress responses after treatments used in bladder cancer

Objective: To investigate the molecular stress responses related to the quality of recovery of normal tissue after various treatments for bladder cancer, i.e. hyperthermia, ionizing radiation, mitomycin-C and 5-aminolaevulinic acid photodynamic therapy (ALA-PDT). Materials and methods: The study focused particularly on intracellular fibroblast levels of heat-shock protein-47 (HSP47) and HSP72, which are associated with collagen metabolism and the development of tolerance to repeated treatment, respectively. Iso-effective treatment doses (50% clonogenic cell survival) of each method were delivered to a 3T6 murine fibroblast model. Intracellular extracts were analysed at 3, 6, 9, 12 and 24 h after treatment, using Western blot analysis to compare the levels of HSP47 and HSP72. Time-matched treatment and control groups were quantified by comparison with actin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression using appropriate software. Results: There were various changes in levels of HSP expression with treatment method: HSP47 levels were significantly higher after hyperthermia and radiation but not with mitomycin-C or ALA-PDT. HSP72 levels were significantly higher with all methods except ALA-PDT. Conclusions: Hyperthermia and ionizing radiation are associated with early increases in levels of HSP47 (a marker of collagen metabolism), in contrast to ALA-PDT and mitomycin-C. These findings are compatible with clinical findings where fibrosis/scarring is common with the first two but not the last two methods. In addition, all methods except ALA-PDT are associated with an increase in HSP 72 (a protein associated with cellular tolerance) and this may help to explain, at a cellular level, why resistance to repeated ALA-PDT treatments does not seem to occur.