Cell cycle kinetics, tissue transglutaminase and programmed cell death (apoptosis)

Area of Science:

• Cell Biology
• Biochemistry
• Cancer Research

Background:

• Apoptosis, or programmed cell death, is crucial for development and disease.
• The cell cycle regulates cell proliferation and differentiation.
• Transglutaminase activity is implicated in various cellular processes, including apoptosis.

Purpose of the Study:

• To investigate the relationship between apoptosis and cell cycle phase in a metastatic fibrosarcoma cell line.
• To determine if apoptosis synchronizes with a specific cell cycle phase.
• To assess the role of transglutaminase activity in this synchronization.

Main Methods:

• Utilized a highly metastatic hamster fibrosarcoma cell line.
• Employed double thymidine block to synchronize cells in early S-phase.
• Applied flow cytometry and [3H]thymidine incorporation for cell cycle analysis.
• Quantified apoptosis via transglutaminase-mediated detergent-insoluble envelopes.

Main Results:

• The apoptotic index was maximal in mid-S-phase.
• Transglutaminase specific activity also peaked during mid-S-phase.
• Enzyme levels remained constant across the cell cycle.

Conclusions:

• Apoptosis in this fibrosarcoma model is synchronized with mid-S-phase.
• Transglutaminase activity, not enzyme synthesis, is the primary regulator of its role in cell cycle-dependent apoptosis.
• Findings highlight a specific cell cycle window for apoptosis induction in cancer cells.