Alternative end-joining originates stable chromosome aberrations induced by etoposide during targeted inhibition of DNA-PKcs in ATM-deficient tumor cells

• Published in: Chromosome research 2022-12, Vol.30 (4), p.459-476
• Main Authors: de Campos Nebel, Marcelo, Palmitelli, Micaela, Pérez Maturo, Josefina, González-Cid, Marcela
• Format: Article
• Language: English
• Subjects: Addictions; Animal Genetics and Genomics; Ataxia Telangiectasia Mutated Proteins - genetics; Ataxia Telangiectasia Mutated Proteins - metabolism; Biomedical and Life Sciences; Cell Biology; Cell cycle; Cell Line; Chemotherapy; Chromosome Aberrations; Chromosome rearrangements; Chromosomes; Deoxyribonucleic acid; DNA; DNA - genetics; DNA Breaks, Double-Stranded; DNA damage; DNA End-Joining Repair; DNA Repair; DNA topoisomerase (ATP-hydrolysing); DNA-Activated Protein Kinase - genetics; DNA-Activated Protein Kinase - metabolism; DNA-dependent protein kinase; Double-strand break repair; Etoposide; Etoposide - pharmacology; Human Genetics; Humans; Life Sciences; Lymphocytes T; Non-homologous end joining; Original Article; Plant Genetics and Genomics; Poly(ADP-ribose) polymerase; Tumor cells; Tumors
• ISSN: 0967-3849; 1573-6849
• DOI: 10.1007/s10577-022-09700-w

ATM and DNA-PKcs coordinate the DNA damage response at multiple levels following the exposure to chemotherapy. The Topoisomerase II poison etoposide (ETO) is an effective chemotherapeutic agent that induces DNA double-strand breaks (DSB), but it is responsible from the chromosomal rearrangements frequently found in therapy-related secondary tumors. Targeted inhibition of DNA-PKcs in ATM-defective tumors combined with radio- or chemotherapy has been proposed as relevant therapies. Here, we explored the DNA repair mechanisms and the genetic consequences of targeting the non-oncogenic addiction to DNA-PKcs of ATM-defective tumor cells after exposure to ETO. We demonstrated that chemical inhibition of DNA-PKcs followed by treatment with ETO resulted in the accumulation of chromatid breaks and decreased mitotic index in both A-T cells and ATM-knocked-down (ATM kd ) tumor cells. The HR repair process in DNA-PKcs-inhibited ATM kd cells amplified the RAD51 foci number, with no correlated increase in sister chromatid exchanges. The analysis of post-mitotic DNA lesions presented an augmented number of persistent unresolved DSB, without alterations in the cell cycle progression. Long-term examination of chromosome aberrations revealed a strikingly high number of chromatid and chromosome exchanges. By using genetic and pharmacological abrogation of PARP-1, we demonstrated that alternative end-joining (alt-EJ) repair pathway is responsible for those chromosome abnormalities generated by limiting c-NHEJ activities during directed inhibition of DNA-PKcs in ATM-deficient cells. Targeting the non-oncogenic addiction to DNA-PKcs of ATM-defective tumors stimulates the DSB repair by alt-EJ, which is liable for the origin of cells carrying stable chromosome aberrations that may eventually restrict the therapeutic strategy.