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.