Abstract P6-08-05: Protein tyrosine kinase activity and miRNA expression profiling reveals differences according to progesterone-receptor-status in HER-2 negative breast cancer

Background: Kinases are considered as promising source of biomarkers for diagnostic, prognostic and therapeutic purposes in cancer patients. We assessed tyrosine kinase activity in 39 primary breast cancer samples that were all hormone receptor positive (ER+ and/or PR+) with differential HER-2 status, using microarray technology. Methods: Pamchip® peptide microarrays were used to measure the activity of protein tyrosine kinases in 32 breast cancer samples. The breast cancer cell lines MCF-7, BT474 and ZR75-1, was studied for kinase activity, both untreated and treated with estradiol. Results: Results showed differences in phosphorylation amongst breast cancer samples. A total of 37 peptide kinases were highly phosphorylated in a group of breast cancer samples representing 33 protein tyrosine kinases involved in cancer pathways and immunological responses. In vitro studies with breast cancer cell lines exhibited the same phosphorylation profiles, but increased phosphorylation was only observed in one cell line, ZR75-1. Eliminating HER-2 positive samples, we obtained differences in phosphorylation profiles based on PR-status only. Samples lacking PR-expression exhibited higher kinase activity of downstream kinases compared to PR-positive samples. Similar results were obtained with miRNA expression profiles of 31 breast cancer samples. Five miRNAs were identified to be significantly differentially expressed (p < 0.05) between PR-negative and PR-positive samples. This effect was even stronger when eliminating HER-2 positive samples, with 13 miRNAs exhibiting significant differential expression based on PR-status. Conclusion: Although our data are based on a small dataset, the lack of PR expression seems to have a profound effect on tyrosine kinase activity and miRNA expression in HER-2 negative breast cancers without any effect on gene expression. This indicates that regulatory and functional molecules might exhibit phenotypical features of cancer that cannot be explained by gene expression alone.

Citation Format: Tahiri A, Satheesh SV, de Wijn R, Lders T, Aure MR, Quigley DA, Bukholm IR, Hurtado A, Kristensen VN, Geisler J. Protein tyrosine kinase activity and miRNA expression profiling reveals differences according to progesterone-receptor-status in HER-2 negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-08-05.