Université de Lyon, F-69000, Lyon, France.
Inserm U1052, Centre de Recherche en Cancérologie de Lyon, Centre Léon Bérard, Bâtiment D, 28 rue Laennec, 69373 Lyon Cedex 08, F-69000, Lyon, France.
Breast Cancer Res. 2020 May 19;22(1):50. doi: 10.1186/s13058-020-01278-7.
Alterations in estrogen and progesterone signaling, via their respective receptors, estrogen receptor alpha (ERα) and progesterone receptor (PR), respectively, are largely involved in the development of breast cancer (BC). The recent identification of ERα-36, a splice variant of ERα, has uncovered a new facet of this pathology. Although ERα-36 expression is associated with poor prognosis, metastasis development, and resistance to treatment, its predictive value has so far not been associated with a BC subtype and its mechanisms of action remain understudied.
To study ERα-36 expression in BC specimens, we performed immunochemical experiments. Next, the role of ERα-36 in progesterone signaling was investigated by generating KO clones using the CRISPR/CAS9 technology. PR signaling was also assessed by proximity ligation assay, Western blotting, RT-QPCR, and ChIP experiments. Finally, proliferation assays were performed with the IncuCyte technology and migration experiments using scratch assays.
Here, we demonstrate that ERα-36 expression at the plasma membrane is correlated with a reduced disease-free survival in a cohort of 160 BC patients, particularly in PR-positive tumors, suggesting a crosstalk between ERα-36 and PR. Indeed, we show that ERα-36 interacts constitutively with PR in the nucleus of tumor cells. Moreover, it regulates PR expression and phosphorylation on key residues, impacting the biological effects of progesterone.
ERα-36 is thus a regulator of PR signaling, interfering with its transcriptional activity and progesterone-induced anti-proliferative effects as well as migratory capacity. Hence, ERα-36 may constitute a new prognostic marker as well as a potential target in PR-positive BC.
雌激素和孕激素信号的改变，分别通过其各自的受体雌激素受体α（ERα）和孕激素受体（PR），在很大程度上参与了乳腺癌（BC）的发展。最近发现的 ERα-36，是 ERα 的剪接变体，揭示了这种病理学的一个新方面。尽管 ERα-36 的表达与预后不良、转移发展和治疗耐药性有关，但它的预测价值迄今为止尚未与 BC 亚型相关联，其作用机制仍在研究中。
为了研究 BC 标本中 ERα-36 的表达，我们进行了免疫化学实验。接下来，我们使用 CRISPR/CAS9 技术生成 KO 克隆，研究了 ERα-36 在孕激素信号中的作用。通过邻近连接测定、Western blotting、RT-QPCR 和 ChIP 实验评估了 PR 信号。最后，使用 IncuCyte 技术进行了增殖实验，使用划痕实验进行了迁移实验。
在这里，我们证明了在 160 名 BC 患者的队列中，ERα-36 在质膜上的表达与无病生存率降低相关，特别是在 PR 阳性肿瘤中，这表明 ERα-36 与 PR 之间存在串扰。事实上，我们表明 ERα-36 在肿瘤细胞的核内与 PR 组成性相互作用。此外，它调节 PR 的表达和关键残基的磷酸化，影响孕激素的生物学效应。
因此，ERα-36 是 PR 信号的调节剂，干扰其转录活性以及孕激素诱导的增殖抑制作用和迁移能力。因此，ERα-36 可能成为 PR 阳性 BC 的新预后标志物和潜在靶点。
