RESUMO
Androgens stimulate the proliferation of epithelial cells in the prostate by activating topoisomerase 2 (TOP2) and regulating the transcription of target genes. TOP2 resolves the entanglement of genomic DNA by transiently generating double-strand breaks (DSBs), where TOP2 homodimers covalently bind to 5' DSB ends, called TOP2-DNA cleavage complexes (TOP2ccs). When TOP2 fails to rejoin TOP2ccs generating stalled TOP2ccs, tyrosyl DNA phosphodiesterase-2 (TDP2) removes 5' TOP2 adducts from stalled TOP2ccs prior to the ligation of the DSBs by nonhomologous end joining (NHEJ), the dominant DSB repair pathway in G0 /G1 phases. We previously showed that estrogens frequently generate stalled TOP2ccs in G0 /G1 phases. Here, we show that physiological concentrations of androgens induce several DSBs in individual human prostate cancer cells during G1 phase, and loss of TDP2 causes a five times higher number of androgen-induced chromosome breaks in mitotic chromosome spreads. Intraperitoneally injected androgens induce several DSBs in individual epithelial cells of the prostate in TDP2-deficient mice, even at 20 hr postinjection. In conclusion, physiological concentrations of androgens have very strong genotoxicity, most likely by generating stalled TOP2ccs.
Assuntos
Androgênios/toxicidade , Quebras de DNA de Cadeia Dupla , Proteínas de Ligação a DNA/metabolismo , Células Epiteliais/metabolismo , Instabilidade Genômica/genética , Diester Fosfórico Hidrolases/metabolismo , Próstata/metabolismo , Animais , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Quebra Cromossômica , Reparo do DNA por Junção de Extremidades/efeitos dos fármacos , Reparo do DNA por Junção de Extremidades/genética , Proteínas de Ligação a DNA/genética , Células Epiteliais/efeitos dos fármacos , Pontos de Checagem da Fase G1 do Ciclo Celular/efeitos dos fármacos , Pontos de Checagem da Fase G1 do Ciclo Celular/genética , Instabilidade Genômica/efeitos dos fármacos , Histonas/metabolismo , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Diester Fosfórico Hidrolases/genética , Próstata/efeitos dos fármacos , Neoplasias da Próstata/genética , RNA Interferente Pequeno , Receptores Androgênicos/metabolismoRESUMO
The ATM kinase is a master regulator of the DNA damage response to double-strand breaks (DSBs) and a well-established tumour suppressor whose loss is the cause of the neurodegenerative and cancer-prone syndrome Ataxia-Telangiectasia (A-T). A-T patients and Atm-/- mouse models are particularly predisposed to develop lymphoid cancers derived from deficient repair of RAG-induced DSBs during V(D)J recombination. Here, we unexpectedly find that specifically disturbing the repair of DSBs produced by DNA topoisomerase II (TOP2) by genetically removing the highly specialised repair enzyme TDP2 increases the incidence of thymic tumours in Atm-/- mice. Furthermore, we find that TOP2 strongly colocalizes with RAG, both genome-wide and at V(D)J recombination sites, resulting in an increased endogenous chromosomal fragility of these regions. Thus, our findings demonstrate a strong causal relationship between endogenous TOP2-induced DSBs and cancer development, confirming these lesions as major drivers of ATM-deficient lymphoid malignancies, and potentially other conditions and cancer types.