Apoptosis associated with esophageal adenocarcinoma: influence of photodynamic therapy

Tumor cell death in vitro by photodynamic therapy (PDT) has been related to the induction of apoptosis. We measured and compared changes in apoptosis and caspase 3 activity, an effector of apoptosis, in normal and neoplastic esophageal tissues during PDT. Apoptosis index, caspase 3 cleavage activity, pro-caspase 3, p53, and bcl-2 levels were measured in normal and neoplastic tissues of patients with esophageal adenocarcinoma before, during, and after PDT with Photofrin. The apoptotic index was greater in carcinoma tissue compared to adjacent normal tissues. In concert, pro-caspase 3 immunoreactivity was absent and caspase 3-like cleavage activity was over 30-fold greater in carcinoma tissue compared to normal esophageal tissues. These parameters were unaffected by PDT. Variable changes in bcl-2 and p53 immunoreactivity were noted in normal and carcinoma tissues during PDT. Greater levels of apoptosis and caspase 3 activity are hallmarks of esophageal adenocarcinoma compared to normal esophageal tissue. These differences were unaffected by PDT. This may be due to the fact that tissues were obtained 72 h post-PDT therapy. Changes in these parameters may have occurred early after PDT therapy. An assessment of apoptosis and caspase 3 activity prior to 72 h post-PDT may provide further insight into the mechanism involved, although no sustained effects on these parameters by PDT were noted.