Effects of Telomerase Expression on Photodynamic Therapy of Barrett's Esophagus

Photodynamic therapy has been applied to Barrett's esophagus and has been shown in prospective randomized studies to eliminate dysplasia as well as decrease the occurrence of cancer. However, the therapy is not always effective and there are issues with residual areas of Barrett's mucosa despite therapy. There has not been a good explanation for these residual areas and they seem to imply that there may exist a biological mechanism by which these cells may be resistant to photodynamic therapy. It was our aim to determine if known abnormalities in Barrett's mucosa could be correlated with the lack of response of some of these tissues. We examined the tissue from multiple patients who had response to therapy as well as those who did not respond. We assessed the tissue for p53 mutations, inactivation of p16, ploidy status, cell proliferation, telomerase activity, and degree of dysplasia. Interestingly, the only genetic marker than was found to be correlated with lack of response was p53 and telomerase activity. This suggests that cells that have lost mechanisms for cell death such as apoptosis or telomere shortening may be more resistant to photodynamic therapy. In this study, we examined patients before and after PDT for telomerase activity.