Ephrin type-A receptor 2 (EPHA2) is a receptor tyrosine kinase (RTK), whose over-expression has been observed in a variety of cancers, including breast cancer. EPHA2 expression may be causally related to tumorigenesis; therefore, it is important to understand how EPHA2 gene (EPHA2) expression is regulated. Here, we report that EPHA2 antisense RNA (EPHA2-AS), a natural antisense transcript, is an important modulator of EPHA2 mRNA levels. EPHA2-AS is a ∼1.8 kb long non-coding RNA (lncRNA) with a poly(A) tail that encodes two splice variants, EPHA2-AS1/2. They are constitutively expressed in a concordant manner with EPHA2 mRNA in human breast adenocarcinoma cell lines and in patient samples, with the highest levels detected in the triple-negative breast cancer (TNBC) subtype. The silencing of EPHA2-AS1/2 by a sense oligonucleotide or over-expression of an antisense oligoribonucleotide, which were both designed from the EPHA2 mRNA region (nt 2955–2974) targeted by AS1/2, showed that EPHA2-AS1/2 modulated EPHA2 mRNA levels by interacting with the specific AS1/2-complementary region in the mRNA. The EPHA2-AS1/2 did not prevent microRNAs from acting on the relevant microRNA response elements shared by EPHA2-AS1/2 and EPHA2 mRNA. Our studies demonstrate a crucial role played by EPHA2-AS1/2 in modulating EPHA2 mRNA levels, and hence production of EPHA2 protein, a key oncogenic RTK that contributes to the tumorigenesis of TNBC cells.

Ephrin A型受体2（EPHA2）是一种酪氨酸激酶（RTK）受体，在包括乳腺癌在内的多种癌症中都发现过表达。EPHA2的表达可能与肿瘤发生有关；因此，了解EPHA2基因（EPHA2）表达受到调节。在这里，我们报告说，EPHA2反义RNA（EPHA2-AS），一种天然的反义转录物，是EPHA2 mRNA水平的重要调节剂。EPHA2-AS是一个约1.8 kb长的非编码RNA（lncRNA），带有一条poly（A）尾巴，可编码两个剪接变体EPHA2-AS1 / 2。它们在人乳腺癌细胞系和患者样品中与EPHA2 mRNA一致地组成型表达，在三阴性乳腺癌（TNBC）亚型中检测到的水平最高。通过有义寡核苷酸使EPHA2-AS1 / 2沉默或反义寡核糖核苷酸的过表达（均由AS1 / 2靶向的EPHA2 mRNA区（nt 2955–2974）设计），表明EPHA2-AS1 / 2已被调节通过与mRNA中的特定AS1 / 2互补区域相互作用，EPHA2 mRNA的水平得以提高。EPHA2-AS1 / 2不会阻止microRNA作用于EPHA2-AS1 / 2和EPHA2 mRNA共有的相关microRNA反应元件。我们的研究表明，EPHA2-AS1 / 2在调节EPHA2 mRNA水平和因此产生EPHA2蛋白（一种关键的致癌RTK，有助于TNBC细胞的肿瘤发生）中起着至关重要的作用。