The effect of growth architecture on the induction and decay of bleomycin and X-ray-induced bystander response and genomic instability in lung adenocarcinoma cells and blood lymphocytes

Abstract

Purpose: Cancer patients treated with radiomimetic drug bleomycin (BLM) have shown incidence of 7% second malignancy. Studies regarding BLM-induced genomic instability in bystander cells are scarce, and experiments with cells grown on three-dimensional (3D) cultures to mimic the in-vivo condition have never been attempted.

Materials and methods: A549 and NCI-H23 (human lung adenocarcinoma) cells were grown as 3D cultures using Cytomatrix^™, exposed to BLM or X-radiation and co-cultured with their respective unexposed cells. The DNA damage in direct and bystander cells were assessed by the induction of micronuclei (MN) or phosphorylated serine-15 residue in protein 53 (p53^ser-15), a reflection of DNA damage, and by up-regulation of protein 21 (p21Waf1). The persistence of DNA damage was measured using MN assay and fluorescence in situ hybridization (FISH) in cancer cells and human peripheral blood lymphocytes (PBL) respectively.

Results: BLM or X-irradiation induced DNA damage in both A549 and NCI-H23 cells and their respective bystander cells grown in 2D or 3D cultures. Further persistence of these damages in bystander PBL at delayed times indicated genomic instability in these cells.

Conclusion: BLM-induced genomic instability in the progeny of bystander cells and their significance in therapy-induced second malignancy may not be eliminated completely.

Keywords::

• Bleomycin
• X-irradiation
• bystander response
• micronucleus
• translocation and genomic instability