CNDAC-Induced DNA Double-Strand Breaks Cause Aberrant Mitosis Prior to Cell Death

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• The deoxycytidine analogue 2'-C-cyano-2'-deoxy-1-β-D-arabino-pentofuranosyl-cytosine (CNDAC) is a clinically active compound.
• CNDAC incorporation into DNA leads to single-strand breaks, subsequently converted to double-strand breaks (DSBs).

Purpose of the Study:

• To investigate the cellular consequences of CNDAC-induced DNA breaks.
• To link these mechanisms to cell death pathways.
• To assess the role of DNA repair pathways in cellular protection against CNDAC damage.

Main Methods:

• Exposure of cells to CNDAC, followed by drug washout.
• Live cell imaging using GFP-tagged histone H2B to monitor cell cycle progression.
• Analysis of chromosomal aberrations and multinucleate cells.
• Testing CNDAC sensitivity in cells deficient in specific DNA repair pathways (XPF-ERCC1, Rad51D, Polθ).

Main Results:

• CNDAC exposure resulted in chromosomal aberrations, DNA strand breaks, and multinucleate cells, dependent on exposure time and concentration.
• Cells showed delayed progression to a second mitosis and aberrant mitoses.
• Cells lacking XPF-ERCC1 nuclease function exhibited a 16-fold increase in chromosome aberrations.
• Rad51D-mutant cells (homologous recombination deficient) displayed more severe chromosomal damage.
• Polq mutant cells (defective in alternative end joining) did not show enhanced sensitivity.

Conclusions:

• CNDAC induces DSBs, likely in the second S-phase post-exposure.
• These DSBs lead to chromosomal aberrations, aberrant mitoses, and subsequent apoptosis.
• Homologous recombination and potentially other repair pathways are critical for mitigating CNDAC-induced DNA damage and cell death.