Non-nuclear human estrogen receptor-alpha 36 (hERα-36) is expressed in ER, PR, and Her2 positive or negative breast cancer patients as well as cell lines, and physically interacts with Her2
Authors: Jian Huang, Gary C. Chamness, Rachel Schiff, Eric Chang, C. Kent Osborne, M Carolina Gutierrez, Sufeng Mao, Yun Wu, Liying Jiang, Qing Lai, Zhaoyi Wang, Susan Hilsenbeck
Journal: Cancer Research (2008)

5174   Human estrogen receptor-α36 (hERα-36) is a recently found splicing isoform of full length ERα-66. It has been found that hERα-36 is a plasma membrane associated protein and can activate membrane-initiated non-genomic signaling pathways in breast cancer cell lines. However, hERα-36 expression in breast cancers has not been reported, and its relationship with ER, PR, and Her2 status in breast cancer patients is unknown. Thus, we conducted this study.  (1) First, we examined the expression of hERα-36 by immunohistochemistry (IHC) and immunofluorescence(IF) staining using specific anti-hERα-36 antibody in 96 paraffin samples of invasive breast cancer (IBC), as well as breast cancer cell lines. The results showed that the expression rate of hERα-36 was 58%, while the expression rates of ER, PR, and Her2 in the same tumors were 63%, 34%, and 20%, respectively. hERα-36 was positive in MCF-7/Her2 and MDA-MB-231 cell lines but negative in parental MCF-7 cells. (2) We then compared the expression rate of hERα-36 in ERα-66, PR, and Her2 positive and negative IBC samples. We found that the expression rates of hERα-36 in ERα-66 positive vs. negative tumors were 65% and 47%, respectively, in PR positive vs. negative were 69% and 50% respectively, and in Her2 positive vs. negative were 68% and 53% respectively. More interestingly, we found that the expression rates of hERα-36 in IBCs that were ER/PR double negative, ER/PR/Her2 triple negative, and ER/PR negative but Her2 positive, were 47%, 33%, and 75% respectively. (3)Furthmore,we also performed semi-quantitative reverse transcription-PCR to detect the expression of ER36 mRNA in 20 patient IBCs as well in breast cancer cell lines. hER36 mRNA was found in 6 of 20 IBCs (30%), and in MCF-7/Her2 and MDA-MB-231 cell lines but not in parental MCF-7 cells, consistent with the protein expression results. (4) Finally, we explored the relationship between hERα-36 and Her2. Co-IF staining of Her2 and hERα-36 showed that hERα-36 co-localized with Her2 in both cytoplasm and plasma membrane in most Her2 and hERα-36 positive IBC samples as well in the MCF-7/Her2 cell line. Immunoprecepitation (IP) confirmed that hER36-α physically interacts with Her2 in this cell line.  We find that hERα-36 presents in IBCs either positive or negative for ER, PR, and Her2, and suggest that hER36-α might be an important co-factor along with ER, PR and Her2 to drive the development and progression of breast cancer. The data also suggest that hERα-36 might play unique roles in ER/ PR double negative and ER/PR/Her2 triple negative breast cancers. Since ERα-36 physically interacts with Her2, this interaction might indicate a functional relationship between Her2 and ERα-36, such that ERα-36 might serve as a target for breast cancer treatment.