Tumor-associated neutrophil precursors impair homologous DNA repair and promote sensitivity to PARP-inhibition [ChIP-seq]

Tumor evolution is one of the major mechanisms responsible for acquiring therapy-resistant and more aggressive cancer clones. Whether the tumor microenvironment through immune-mediated mechanisms might promote the development of more aggressive cancer types is crucial for the identification of additional therapeutical opportunities. Here, we identified a novel subset of tumor-associated neutrophils, defined as tumor-associated neutrophil precursors (PreNeu). These PreNeu are enriched in female highly proliferative hormone-dependent breast cancers and impair DNA repair capacity.  Mechanistically, succinate secreted by tumor-associated PreNeu inhibit homologous recombination, promoting error-prone DNA repair through non-homologous end-joining regulated by PARP-1. Consequently, breast cancer cells acquire genomic instability promoting tumor editing and progression. Selective inhibition of these pathways induces increased tumor cell killing in vitro and in vivo. Tumor-associated PreNeu score correlates with copy number alterations in highly proliferative hormone-dependent tumors from breast cancer patients. Treatment with PARP-1 inhibitors counteract the pro-tumoral effect of these neutrophils. ChIP-Seq of the histone modification H3K9me3 in MCF-7 cells subjected to CS-FBS and Succinate 2mM (Cat. S9512, Sigma-Aldrich) or control.

肿瘤演化是促使癌症克隆株获得治疗耐药性并增强侵袭性的核心机制之一。肿瘤微环境是否可通过免疫介导机制促进更具侵袭性的癌症亚型发展，这对于发掘额外的治疗机遇至关重要。本研究中，我们鉴定出一类新型肿瘤相关中性粒细胞亚群，将其定义为肿瘤相关中性粒细胞前体（tumor-associated neutrophil precursors, PreNeu）。这类PreNeu富集于女性高增殖激素依赖性乳腺癌组织中，并会损害DNA修复能力。从机制层面来看，肿瘤相关PreNeu分泌的琥珀酸会抑制同源重组，并通过聚ADP核糖聚合酶-1（PARP-1）调控的非同源末端连接途径，促进易出错的DNA修复。由此，乳腺癌细胞会获得基因组不稳定性，进而推动肿瘤编辑与疾病进展。对上述通路进行选择性抑制，可在体外与体内实验中增强对肿瘤细胞的杀伤效果。肿瘤相关PreNeu评分与乳腺癌患者的高增殖激素依赖性肿瘤的拷贝数变异呈显著相关。使用PARP-1抑制剂进行治疗，可抵消这类中性粒细胞的促肿瘤效应。本实验针对经碳剥离胎牛血清（CS-FBS）、2mM琥珀酸（货号S9512，Sigma-Aldrich）或对照试剂处理的MCF-7细胞，开展了组蛋白修饰H3K9me3的染色质免疫共沉淀测序（ChIP-Seq）。