Targeted Eicosanoid Profiling Reveals MicroRNA-155 Shifts PGE2/PGD2 Balance Towards Oncogenic State

microRNA-155 is a strong oncogenic microRNAs with multiple functions. To reveal its novel function in cancer metabolism, we performed a targeted metabolomic analysis of icosanoids, the key metabolites of inflammation-related carcinogenesis. We found miR-155-depleted cells expressed unbalanced prostaglandins, especially in PGE2 and PGD2. Subsequent analysis of primary cancer cells and 20 TNBC specimen indicated a positive correlation between miR-155 and PGE2/PGD2 ratio. Mechanistically, miR-155 controls the prostaglandin shift by up-regulating PGE2-producing enzymes PTGES/PTGES2 and down-regulating PGD2-producing enzyme PTGDS. Further analysis showed that the up-regulation of PTGES2 is driven by miR-155-cMYC axis whereas PTGES is transactivated by miR-155-KLF4 axis, indicating a dual-regulatory mode for the metabolic enzyme expression drives a shift in PGE2/PGD2 balance. Lastly, we show the miR-155-driven cellular proliferation is significantly restored by the siRNA of PTGES1/2, of which expression also correlates with patients’ survival. Taken altogether, our study reveals an unprecedented oncogenic function of miR-155 on prostaglandin regulation.