Cardiovascular Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA.
Department of Medicine, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA.
Breast Cancer Res. 2019 Jun 15;21(1):74. doi: 10.1186/s13058-019-1155-7.
SHC1 proteins (also called SHCA) exist in three functionally distinct isoforms (p46SHC, p52SHC, and p66SHC) that serve as intracellular adaptors for several key signaling pathways in breast cancer. Despite the broad evidence implicating SHC1 gene products as a central mediator of breast cancer, testing the isoform-specific roles of SHC1 proteins have been inaccessible due to the lack of isoform-specific inhibitors or gene knockout models.
Here, we addressed this issue by generating the first isoform-specific gene knockout models for p52SHC and p66SHC, using germline gene editing in the salt-sensitive rat strain. Compared with the wild-type (WT) rats, we found that genetic ablation of the p52SHC isoform significantly attenuated mammary tumor formation, whereas the p66SHC knockout had no effect. Rats were dosed with 7,12-dimethylbenz(a)anthracene (DMBA) by oral gavage to induce mammary tumors, and progression of tumor development was followed for 15 weeks. At 15 weeks, tumors were excised and analyzed by RNA-seq to determine differences between tumors lacking p66SHC or p52SHC.
Compared with the wild-type (WT) rats, we found that genetic ablation of the p52SHC isoform significantly attenuated mammary tumor formation, whereas the p66SHC knockout had no effect. These data, combined with p52SHC being the predominant isoform that is upregulated in human and rat tumors, provide the first evidence that p52SHC is the oncogenic isoform of Shc1 gene products in breast cancer. Compared with WT tumors, 893 differentially expressed (DE; FDR < 0.05) genes were detected in p52SHC KO tumors compared with only 18 DE genes in the p66SHC KO tumors, further highlighting that p52SHC is the relevant SHC1 isoform in breast cancer. Finally, gene network analysis revealed that p52SHC KO disrupted multiple key pathways that have been previously implicated in breast cancer initiation and progression, including ESR1 and mTORC2/RICTOR.
Collectively, these data demonstrate the p52SHC isoform is the key driver of DMBA-induced breast cancer while the expression of p66SHC and p46SHC are not enough to compensate.
SHC1 蛋白（也称为 SHCA）存在三种功能不同的同工型（p46SHC、p52SHC 和 p66SHC），它们作为几种关键信号通路的细胞内衔接蛋白在乳腺癌中发挥作用。尽管有广泛的证据表明 SHC1 基因产物是乳腺癌的中央介质，但由于缺乏同工型特异性抑制剂或基因敲除模型，检测 SHC1 蛋白的同工型特异性作用一直难以实现。
在这里，我们通过在盐敏感大鼠品系中进行种系基因编辑，为 p52SHC 和 p66SHC 生成了首个同工型特异性基因敲除模型，从而解决了这个问题。与野生型（WT）大鼠相比，我们发现 p52SHC 同工型的基因缺失显著减弱了乳腺肿瘤的形成，而 p66SHC 敲除则没有影响。大鼠通过口服灌胃 7,12-二甲基苯并[a]蒽（DMBA）诱导乳腺肿瘤，随后进行 15 周的肿瘤发展进展监测。在 15 周时，切除肿瘤并进行 RNA-seq 分析，以确定缺乏 p66SHC 或 p52SHC 的肿瘤之间的差异。
与野生型（WT）大鼠相比，我们发现 p52SHC 同工型的基因缺失显著减弱了乳腺肿瘤的形成，而 p66SHC 敲除则没有影响。这些数据，加上 p52SHC 是在人和大鼠肿瘤中上调的主要同工型，提供了第一个证据，表明 p52SHC 是乳腺癌中 Shc1 基因产物的致癌同工型。与 WT 肿瘤相比，在 p52SHC KO 肿瘤中检测到 893 个差异表达（DE； FDR < 0.05）基因，而在 p66SHC KO 肿瘤中仅检测到 18 个 DE 基因，这进一步表明 p52SHC 是乳腺癌中相关的 SHC1 同工型。最后，基因网络分析表明，p52SHC KO 破坏了先前涉及乳腺癌起始和进展的多个关键途径，包括 ESR1 和 mTORC2/RICTOR。
综上所述，这些数据表明 p52SHC 同工型是 DMBA 诱导的乳腺癌的关键驱动因素，而 p66SHC 和 p46SHC 的表达不足以代偿。
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