Background

Canine mammary tumours (CMTs) are the most frequent tumours in intact female dogs and show strong similarities with human breast cancer. In contrast to the human disease there are no standardised diagnostic or prognostic biomarkers available to guide treatment. We recently identified a prognostic 18-gene RNA signature that could stratify human breast cancer patients into groups with significantly different risk of distant metastasis formation. Here, we assessed whether expression patterns of these RNAs were also associated with canine tumour progression.

Method

A sequential forward feature selection process was performed on a previously published microarray dataset of 27 CMTs with and without lymph node (LN) metastases to identify RNAs with significantly differential expression to identify prognostic genes within the 18-gene signature. Using an independent set of 33 newly identified archival CMTs, we compared expression of the identified prognostic subset on RNA and protein basis using RT-qPCR and immunohistochemistry on FFPE-tissue sections.

Results

While the 18-gene signature as a whole did not have any prognostic power, a subset of three RNAs: Col13a1, Spock2, and Sfrp1, together completely separated CMTs with and without LN metastasis in the microarray set. However, in the new independent set assessed by RT-qPCR, only the Wnt-antagonist Sfrp1 showed significantly increased mRNA abundance in CMTs without LN metastases on its own (p = 0.013) in logistic regression analysis. This correlated with stronger SFRP1 protein staining intensity of the myoepithelium and/or stroma (p < 0.001). SFRP1 staining, as well as β-catenin membrane staining, was significantly associated with negative LN status (p = 0.010 and 0.014 respectively). However, SFRP1 did not correlate with β-catenin membrane staining (p = 0.14).

Conclusion

The study identified SFRP1 as a potential biomarker for metastasis formation in CMTs, but lack of SFRP1 was not associated with reduced membrane-localisation of β-catenin in CMTs.

中文翻译：

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SFRP1 表达与犬乳腺肿瘤转移形成呈负相关

背景

犬乳腺肿瘤（CMT）是完整雌性犬中最常见的肿瘤，与人类乳腺癌有很强的相似性。与人类疾病相比，没有标准化的诊断或预后生物标志物可用于指导治疗。我们最近发现了一种预后 18 基因 RNA 特征，可以将人类乳腺癌患者分为具有显着不同的远处转移形成风险的组。在这里，我们评估了这些 RNA 的表达模式是否也与犬肿瘤进展相关。

方法

对先前发布的有或没有淋巴结 (LN) 转移的 27 个 CMT 的微阵列数据集进行顺序前向特征选择过程，以识别具有显着差异表达的 RNA，从而识别 18 基因特征中的预后基因。使用一组独立的 33 个新鉴定的档案 CMT，我们使用 RT-qPCR 和免疫组织化学在 FFPE 组织切片上比较了在 RNA 和蛋白质基础上鉴定的预后子集的表达。

结果

虽然 18 基因特征作为一个整体没有任何预后能力，但三个 RNA 的子集：Col13a1、Spock2和Sfrp1一起完全分离了微阵列组中有或没有 LN 转移的 CMT。 然而，在通过 RT-qPCR 评估的新独立组中，在逻辑回归分析中，只有 Wnt 拮抗剂Sfrp1在没有 LN 转移的 CMT 中显示出 mRNA 丰度显着增加 ( p = 0.013)。这与肌上皮和/或间质更强的 SFRP1 蛋白染色强度相关 ( p  < 0.001)。SFRP1 染色以及 β-catenin 膜染色与阴性 LN 状态显着相关（p 分别 = 0.010 和 0.014）。然而，SFRP1 与 β-连环蛋白膜染色无关（p  = 0.14）。

结论

该研究确定 SFRP1 是 CMT 转移形成的潜在生物标志物，但缺乏 SFRP1 与 CMT 中 β-连环蛋白膜定位减少无关。