TDP2 suppresses genomic instability induced by androgens in the epithelial cells of prostate glands.

Md Rasel Al Mahmud,Hiroyuki Sasanuma,Masakazu Toi,Shunichi Takeda,Irene Delgado‐Sainz,Kenichiro Ishii,Cristina Bernal‐Lozano,Shusuke Akamatsu,Masatoshi Watanabe,Manabu Fukumoto,Felipe Cortés‐Ledesma

doi:10.1111/gtc.12770

Abstract

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.

Highlights

Sex hormones, estrogens and androgens, strongly stimulate the proliferation of epithelial cells in the mammary glands and prostate, respectively (La Vignera, Condorelli, Russo, Morgia, & Calogero, 2016; Liang & Shang, 2013)
We killed three 2-month-old mice of each genotype and counted only luminal cells stained with cytokeratin-8/18 (CK-8/18), a marker of epithelial cells
We subtracted the average number of foci in E2-treated epithelial cells at 6 hr from the average number of foci in E2-untreated epithelial cells

Summary

| INTRODUCTION

Estrogens and androgens, strongly stimulate the proliferation of epithelial cells in the mammary glands and prostate, respectively (La Vignera, Condorelli, Russo, Morgia, & Calogero, 2016; Liang & Shang, 2013). The loss of TDP2 causes attenuated transcriptional responses to androgens in prostate cells, suggesting that exposure to androgens may frequently cause the abortive catalysis of TOP2 It remains elusive how many stalled TOP2ccs are generated by physiological concentrations of androgens. Another unresolved question is the role played by TDP2 in the prevention of prostatic hyperplasia and oncogenesis. Physiological concentrations of androgens induced 4.7 and 16 DSBs in individual wild-type and TDP2−/− cells at G0/G1 phase, respectively This genotoxicity depends on both activated AR and TOP2. We propose that TDP2 suppresses abnormal proliferation of the epithelial cells in the prostate gland by promoting the repair of androgen-induced DSBs and ensuring proper transcriptional responses to androgens

| RESULTS

| DISCUSSION

PROCEDURES

Findings

| Ethics statement