Paclitaxel-induced apoptosis in non-small cell lung cancer cell lines is associated with increased caspase-3 activity.

OBJECTIVE: Our objective was to determine whether paclitaxel-induced apoptosis in human lung cancer cells is Fas dependent.
METHODS: Human lung cancer cell lines were evaluated for morphologic evidence of apoptosis, DNA fragmentation (TUNEL positivity), and caspase-3 activation after paclitaxel treatment. Human lung adenocarcinoma, squamous cell carcinoma, undifferentiated lung carcinoma, and bronchoalveolar carcinoma cell lines were each cultured in 10 micromol/L paclitaxel.
RESULTS: After 24 hours of culture in paclitaxel, a 22% to 69% increase in the number of apoptotic cells was evident by means of methylene blue-azure A-eosin staining with characteristic blebbing and nuclear condensation. TUNEL assay also confirmed an increase of 19.9% to 73.0% of cells with nuclear fragmentation. Caspase-3 activity, assayed by Z-DEVD cleavage, increased from 20% to 215% (P <.05). ZB4, an antagonistic anti-Fas antibody, did not block paclitaxel induction of caspase-3 activity (155.8 vs 165.8 U, not significant). Apoptotic morphologic changes were inhibited in cells cultured in the presence of paclitaxel and Ac-DEVD-CHO, a caspase-3 inhibitor.
CONCLUSIONS: Paclitaxel induces apoptosis in lung cancer cell lines, as assessed by a consistent increase in caspase-3 activity, DNA laddering, and characteristic morphologic changes. Paclitaxel-induced apoptosis in human lung cancer cells is associated with caspase-3 activation but is not Fas dependent.