miR-9-Mediated Inhibition of EFEMP1 Contributes to the Acquisition of Pro-Tumoral Properties in Normal Fibroblasts

Abstract

Tumor growth and invasion occurs through a dynamic interaction between cancer and stromal cells, which support an aggressive niche. MicroRNAs are thought to act as tumor messengers to “corrupt” stromal cells. We previously demonstrated that miR-9, a known metastamiR, is released by triple negative breast cancer (TNBC) cells to enhance the transition of normal fibroblasts (NFs) into cancer-associated fibroblast (CAF)-like cells. EGF containing fibulin extracellular matrix protein 1 (EFEMP1), which encodes for the ECM glycoprotein fibulin-3, emerged as a miR-9 putative target upon miRNA’s exogenous upmodulation in NFs. Here we explored the impact of EFEMP1 downmodulation on fibroblast’s acquisition of CAF-like features, and how this phenotype influences neoplastic cells to gain chemoresistance. Indeed, upon miR-9 overexpression in NFs, EFEMP1 resulted downmodulated, both at RNA and protein levels. The luciferase reporter assay showed that miR-9 directly targets EFEMP1 and its silencing recapitulates miR-9-induced pro-tumoral phenotype in fibroblasts. In particular, EFEMP1 siRNA-transfected (si-EFEMP1) fibroblasts have an increased ability to migrate and invade. Moreover, TNBC cells conditioned with the supernatant of NFs transfected with miR-9 or si-EFEMP1 became more resistant to cisplatin. Overall, our results demonstrate that miR-9/EFEMP1 axis is crucial for the conversion of NFs to CAF-like cells under TNBC signaling.

The miR-4732-5p/XPR1 axis suppresses the invasion, metastasis, and epithelial–mesenchymal transition of lung adenocarcinoma via the PI3K/Akt/GSK3β/Snail pathway

“…In most cases, miRNAs are regarded to be regulators of gene expression. 28 MiR-4732-5p could directly target the 3'UTR of tetraspanin 13 (TSPAN13) and suppress TSPAN13 expression at the mRNA and protein levels. 29 MiR-4732-5p has been demonstrated to function as a tumor suppressor in lung squamous cell carcinoma (LUSC).…”

Cancer-associated fibroblasts: The chief architect in the tumor microenvironment

“…Exosomal or vesicular transfer between tumor cells and CAF secretome frequently results in an active feed-forward loop involving CAFs and tumor cells that increases tumor-promoting CAF activation and aggressive features in cancer cells. Specifically, Cosentino et al (2020) discovered that miR-9-mediated inhibition of EFEMP1 contributed to the upregulation of pro-tumor CAF phenotypes.…”

Secreted Non-Coding RNAs: Functional Impact on the Tumor Microenvironment and Clinical Relevance in Triple-Negative Breast Cancer

“…Further study from the same group also showed that miR-9 directly targets the ECM glycoprotein fibulin-3 (EFEMP1) in CAFs and EFEMP1 down-regulation is responsible for the observed increased CAFs motility upon miR-9 induction. Moreover, the supernatant of EFEMP1-depleted CAFs is able to confer resistance to cisplatin to TNBC cells, highlighting a two-way paracrine communication between these two cell types [ 36 ].…”