Integrative transcriptome-wide analyses reveal critical HER2-regulated mRNAs and lincRNAs in HER2+ breast cancer

Callie R. Merry, Sarah McMahon, Cheryl L. Thompson, Kristy L. S. Miskimen, Lyndsay N. Harris, Ahmad M. Khalil

Breast cancer is a major health problem affecting millions of women worldwide. Over 200,000 new cases are diagnosed annually in the USA, with approximately 40,000 of these cases resulting in death. HER2-positive (HER2+) breast tumors, representing 20-30 % of early-stage breast cancer diagnoses, are characterized by the amplification of the HER2 gene. However, the critical genes and pathways that become affected by HER2 amplification in humans are yet to be specifically identified. Furthermore, it is yet to be determined if HER2 amplification also affects the expression of long intervening non-coding (linc)RNAs, which are involved in the epigenetic regulation of gene expression. We examined changes in gene expression by next generation RNA sequencing in human tumors pre- and post- HER2 inhibition by trastuzumab in vivo, and changes in gene expression in response to HER2 knock down in cell culture models. We integrated our results with gene expression analysis of HER2+ tumors vs matched normal tissue from The Cancer Genome Atlas. The integrative analyses of these datasets led to the identification of a small set of mRNAs, and the associated biological pathways that become deregulated by HER2 amplification. Furthermore, our analyses identified three lincRNAs that become deregulated in response to HER2 amplification both in vitro and in vivo. Our results should provide the foundation for functional studies of these candidate mRNAs and lincRNAs to further our understanding of how HER2 amplification results in tumorigenesis. Also, the identified lincRNAs could potentially open the door for future RNA-based biomarkers and therapeutics in HER2+ breast cancer.