In breast cancer, cancer associated fibroblasts (CAF) express podoplanin but little is known about its mechanism of expression and modulation. This might be crucial for cancer cell movements and for the ability to escape from the tumor site. Podoplanin showed anti-adhesive activity towards tumor and immune cells. A key control of tumor microenvironment is exerted by microRNAs on gene expression. Therefore miRNAs profiling was performed with 3D-Gene microarray technology on a breast CAF model, on cell lysates and on secreted exosomes, in hypoxia versus normoxia culture conditions.

Systems biology enrichment analyses were carried out through bioinformatics using mathematical models that simulate in silico the behaviour of human physiology. Targets linked to the set of differential miRNAs, both up-regulated and down-regulated, have been analyzed with various methods including a hypergeometric distribution method. Processes linked to hypoxia, glycosylation, angiogenesis, extracellular matrix and pathways associated with PI3K-AKT, mTOR, P53 and chemokines signaling were studied.

We showed that podoplanin expression strongly affected miRNAs involved in these processes. Hypoxia increased expression of miR-210, miR-21 and miR-29b in cells over-expressing podoplanin. miR-21 is an oncogenic regulator in most cancer cells through its downstream target proteins among which stands the tumor suppressor PTEN, a candidate to alleviate hypoxia in tumors, regulating tumor angiogenesis and modulating tumor hypoxia. miR-29b is a tumor suppressor, it also correlates with PTEN repression.

We highlighted miRNA regulation of podoplanin expression through downregulation of upstream genes for tumor suppressor PTEN. The combination of miRNome analysis and systems biology bioinformatics uncovered potential miRNAs involved in the regulation of podoplanin activity in CAF. Such data analysis may be applied to protein and mRNA biomarkers and extended to other pathology pathways.

Citation Format: Anna Tejchman, Eric Mennesson, Isabelle Fixe, Alexandra Foucher, Simon Perera, Laura Artigas, Jose Manuel Mas, Catherine Grillon, Maciej Ugorski, Nadia Normand, Claudine Kieda. miRNome analyses reveal that activity of CAF expressed podoplanin in tumor microenvironment is modulated by exosome miRNAs involved in the PTEN-PI3K-AKT-mTOR signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1460. doi:10.1158/1538-7445.AM2017-1460