miR-146b-5p mediates p16-dependent repression of IL-6 and suppresses paracrine procarcinogenic effects of breast stromal fibroblasts.
Increasing evidence support the critical roles of active stromal fibroblasts in breast cancer development and spread. However, the mediators and the mechanisms of regulation are still not well defined. We have shown here that the tumor suppressor p16(INK4A) protein inhibits the pro-carcinogenic effects of breast stromal fibroblasts through repressing the expression/secretion of IL-6. Indeed, p16(INK4A) suppresses IL-6 at the mRNA and protein levels. This effect is mediated trough miR-146b-5p, which inhibits IL-6 expression through a specific sequence at the IL-6 3'UTR. In addition, we present clear evidence that miR-146b-5p inhibition is sufficient to transactivate breast stromal fibroblasts, which promote epithelial-to-mesenchymal-transition in breast cancer cells in a paracrine manner. By contrast, ectopic expression of miR-146b-5p in active fibroblasts abrogated their pro-carcinogenic effects. The physiological importance of miR-146b-5p inhibition was revealed by showing that the levels of pre-miR-146b-5p as well as its mature form are reduced in cancer-associated fibroblasts as compared with their normal adjacent counterparts from cancer-free tissues isolated from the same patients. Interestingly, treatment of active breast stromal fibroblasts with curcumin increased the level of the p16(INK4A) coding CDKN2A mRNA and miR-146b-5p and suppressed IL-6, which confirms the repressive effect of these two tumor suppressor molecules on IL-6, and shows the possible "normalization" of cancer-related active fibroblasts. These results show that miR-146b-5p has non-cell-autonomous tumor suppressor function through inhibition of IL-6, suggesting that targeting this microRNA in breast stromal fibroblasts could be of great therapeutic value.
Department of Molecular Oncology, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.|Department of Microbiology, Faculty of Science and Medical Studies, King Saud University, Riyadh, Saudi Arabia.
Mysoon M
MM
Al-Ansari
Department of Molecular Oncology, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
Abdelilah
A
Aboussekhra
D020413:3' Untranslated Regions / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology; D001940:Breast / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003474:Curcumin / Q000494:pharmacology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics* / Q000378:metabolism; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015151:Immunoblotting; D015850:Interleukin-6 / Q000235:genetics* / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics*; D008957:Models, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000378:metabolism*
D020413:3' Untranslated Regions; D000970:Antineoplastic Agents; D019941:Cyclin-Dependent Kinase Inhibitor p16; D015850:Interleukin-6; C542542:MIRN146 microRNA, human; D035683:MicroRNAs; D003474:Curcumin
IL-6; breast cancer; cancer-associated fibroblasts; miR-146b-5p; p16INK4A