Induction of apoptosis by gemcitabine

Area of Science:

• Molecular Biology
• Cell Biology
• Cancer Research

Background:

• Gemcitabine is a chemotherapy drug that inhibits cellular DNA synthesis.
• It is converted to triphosphate form (dFdCTP) and incorporated into DNA, causing chain termination.
• Gemcitabine also reduces dNTP pools by inhibiting ribonucleotide reductase, indirectly affecting DNA synthesis.

Purpose of the Study:

• To investigate the mechanisms of gemcitabine-induced apoptosis in human leukemia cells.
• To characterize the types of DNA fragmentation resulting from gemcitabine treatment.
• To determine the roles of DNA incorporation, calcium, and other factors in gemcitabine-induced DNA fragmentation and apoptosis.

Main Methods:

• Incubation of human leukemia (CEM) cells with gemcitabine.
• Analysis of DNA fragmentation patterns (large-sized and nucleosomal).
• Use of inhibitors like aphidicolin and calcium chelator BAPTA-AM, and phorbol ester PMA to study mechanisms.

Main Results:

• Gemcitabine induced two types of DNA fragmentation: large (5 kb-500 kb) and nucleosomal.
• DNA synthesis inhibition (aphidicolin) blocked both fragmentation types and apoptosis.
• Nucleosomal fragmentation was calcium-dependent and inhibited by BAPTA-AM and PMA; large-sized fragmentation was calcium-independent.
• BAPTA-AM and PMA did not prevent apoptosis, suggesting nucleosomal fragmentation is not required.

Conclusions:

• Incorporation of gemcitabine into DNA is essential for inducing DNA fragmentation and apoptosis.
• Large-sized DNA fragmentation is critical for gemcitabine-induced apoptosis.
• Nucleosomal DNA fragmentation is a calcium-dependent event but not a necessary component of gemcitabine-induced cell death.