Purpose

In approximately 30% of triple-negative breast cancer (TNBC) patients a complete pathological response is achieved. However, after neo-adjuvant chemotherapy treatment (NACT) residual tumour cells can be intrinsically resistant to chemotherapy. In this study, associations of the WNT/beta-catenin pathway with chemo-tolerance of NACT treated TNBC patients were compared to that of pre-treatment TNBC patients.

Methods

Expression analyses were performed in both pre-treatment and NACT treated TNBC samples using immunohistochemistry and qRT-PCR, along with DNA copy number variation (CNV) and promoter methylation analyses to elucidate the mechanism(s) underlying chemo-tolerance. In addition, in vitro validation experiments were performed in TNBC cells followed by in vivo clinicopathological correlation analyses.

Results

A reduced expression (41.1%) of nuclear beta-catenin together with a low proliferation index was observed in NACT samples, whereas a high expression (59.0%) was observed in pre-treatment samples. The reduced nuclear expression of beta-catenin in the NACT samples showed concordance with reduced expression levels (47-52.9%) of its associated receptors (FZD7 and LRP6) and increased expression levels (35.2–41.1%) of its antagonists (SFRP1, SFRP2, DKK1) compared to those in the pre-treatment samples. The expression levels of the receptors showed no concordance with its respective gene copy number/mRNA expression statuses, regardless treatment. Interestingly, however, significant increases in promoter hypomethylation of the antagonists were observed in the NACT samples compared to the pre-treatment samples. Similar expression patterns of the antagonists, receptors and beta-catenin were observed in the TNBC-derived cell line MDA-MB-231 using the anthracyclines doxorubicin and nogalamycin, suggesting the importance of promoter hypomethylation in chemotolerance. NACT patients showing reduced receptor and/or beta-catenin expression levels and high antagonist expression levels exhibited a comparatively better prognosis than the pre-treatment patients.

Conclusions

Our data suggest that reduced nuclear expression of beta-catenin in NACT TNBC samples, due to downregulation of its receptors and upregulation of its antagonists through promoter hypomethylation of the WNT pathway, plays an important role in chemo-tolerance.

中文翻译：

---

通过改变WNT途径的受体和拮抗剂谱，下调耐化学性TNBC中的β-catenin：临床和预后意义。

目的

在大约30％的三阴性乳腺癌（TNBC）患者中，实现了完全的病理反应。但是，在新辅助化疗治疗（NACT）之后，残留的肿瘤细胞可能固有地对化疗具有耐药性。在这项研究中，比较了WNT /β-catenin途径与NACT治疗的TNBC患者的化学耐受性之间的关联。

方法

使用免疫组织化学和qRT-PCR在预处理和NACT处理的TNBC样品中进行表达分析，以及DNA拷贝数变异（CNV）和启动子甲基化分析，以阐明化学耐受性的机制。此外，在TNBC细胞中进行了体外验证实验，然后进行了体内临床病理相关分析。

结果

在NACT样品中观察到核β-连环蛋白的表达降低（41.1％）和低增殖指数，而在预处理样品中观察到高表达（59.0％）。NACT样品中β-catenin的核表达降低表明其相关受体（FZD7和LRP6）的表达水平降低（47-52.9％），而其拮抗剂（SFRP1，SFRP2）的表达水平升高（35.2–41.1％） ，DKK1）与预处理样品中的样品进行比较。无论处理如何，受体的表达水平与其各自的基因拷贝数/ mRNA表达状态均不一致。然而，有趣的是，与预处理样品相比，在NACT样品中观察到拮抗剂的启动子低甲基化显着增加。拮抗剂的相似表达方式，使用蒽环类阿霉素和诺加霉素在TNBC衍生的细胞系MDA-MB-231中观察到受体和β-连环蛋白，表明启动子低甲基化在耐化学性中的重要性。与治疗前患者相比，NACT患者的受体和/或β-catenin表达水平降低，拮抗剂表达水平较高，预后相对较好。

结论

我们的数据表明，NACT TNBC样品中β-catenin的核表达降低，归因于其受体的下调和通过WNT途径的启动子低甲基化引起的其拮抗剂的上调，在化学耐受性中起重要作用。