The PRL2 Phosphatase Upregulates miR-21 through Activation of the JAK2/STAT3 Pathway to Downregulate the PTEN Tumor Suppressor.

The Phosphatases of Regenerating Liver (PRLs) are members of the protein tyrosine phosphatase (PTP) superfamily that play pro-oncogenic roles in cell proliferation, migration, and survival. We previously demonstrated that PRLs can post-translationally downregulate PTEN, a tumor suppressor frequently inactivated in human cancers, by dephosphorylating PTEN at Tyr336, which promotes the NEDD4-mediated PTEN ubiquitination and proteasomal degradation. Here we report that PRLs can also reduce PTEN expression by upregulating MicroRNA-21 (miR-21), which is one of the most frequently overexpressed miRNAs in solid tumors. We observe a broad correlation between PRL and miR-21 levels in multiple human cancers. Mechanistically, PRL2, the most abundant and ubiquitously expressed PRL family member, promotes the JAK2/STAT3 pathway-mediated miR-21 expression by directly dephosphorylating JAK2 at Tyr570. Finally, we confirm that the PRL2-mediated miR-21 expression contributes to its oncogenic potential in breast cancer cells. Our study defines a new functional role of PRL2 in PTEN regulation through a miR-21-dependent post-transcriptional mechanism, in addition to our previously reported NEDD4-dependent post-translational PTEN regulation. Together, these studies further establish the PRLs as negative regulators of PTEN.