WBP2 is an emerging oncoprotein with diverse functions in breast tumorigenesis via regulating Wnt, epidermal growth factor receptor, estrogen receptor, and Hippo. Recently, evidence shows that WBP2 is tightly regulated by the components of the miRNA biogenesis machinery such as DGCR8 and Dicer via producing both WBP2’s 3′UTR and coding DNA sequence-targeting miRNAs. This led us to hypothesize that WBP2 could provide a feedback loop to the biogenesis of its key upstream regulators by regulating the microprocessor complex activity. Indeed, WBP2 suppressed microprocessor activity by blocking the processing of pri-miRNAs to pre-miRNAs. WBP2 negatively regulated the assembly of the microprocessor complex via physical interactions with its components. Meta-analyses suggest that microprocessor complex components, in particular DGCR8, DDX5, and DEAD-Box Helicase17 (DDX17), have tumor-suppressive properties. 2D and 3D in vitro proliferation assays revealed that WBP2 blocked the tumor-suppressive properties of DGCR8, a key component of the microprocessor complex. In conclusion, WBP2 is a novel regulator of miRNA biogenesis that is a known dysregulated pathway in breast tumorigenesis. The reregulation of miRNA biogenesis machinery via targeting WBP2 protein may have implications in breast cancer therapy.

Cancer is a global health problem. The delineation of molecular mechanisms pertinent to cancer initiation and development has spurred cancer therapy in the form of precision medicine. The Hippo signalling pathway is a tumour suppressor pathway implicated in a multitude of cancers. Elucidation of the Hippo pathway has revealed an increasing number of regulators that are implicated, some being potential therapeutic targets for cancer interventions. WW domain-binding protein 2 (WBP2) is an oncogenic transcriptional co-factor that interacts, amongst others, with two other transcriptional co-activators, YAP and TAZ, in the Hippo pathway. WBP2 was recently discovered to modulate the upstream Hippo signalling components by associating with LATS2 and WWC3. Exacerbating the complexity of the WBP2/Hippo network, WBP2 itself is reciprocally regulated by Hippo-mediated microRNA biogenesis, contributing to a positive feedback loop that further drives carcinogenesis. Here, we summarise the biological mechanisms of WBP2/Hippo reciprocal regulation and propose therapeutic strategies to overcome Hippo defects in cancers through targeting WBP2.

Metformin is an antidiabetic drug that has been tested widely as an anti-cancer agent. However, data from clinical trials have been mixed. Evidence for metformin’s efficacy in HER2+ breast cancer exists. Hence, we evaluated whether WBP2, a HER2-coamplified gene, can regulate the response of HER2+ breast cancer to metformin. Identification of biomarkers for predicting metformin response has implications in repurposing metformin for precision oncology. The effect of WBP2 on breast cancer response to metformin was studied using in vitro and mouse models. The mechanism of WBP2 on metformin-induced AMPK activation was elucidated, and its co-expression with p-AMPK was examined in clinical specimens using IHC. RNA-seq analyses were performed to elucidate WBP2’s mechanism in energy metabolism. WBP2 inhibited the metformin response of HER2+ breast cancer in vitro and in vivo. These effects were concomitant with WBP2-mediated repression of metformin-induced AMPK activation and mTOR inhibition in HER2+ breast cancer cells, a lower AMP:ATP ratio state, and enhanced glycolytic capacity and mitochondria respiration. Analysis of HER2-positive breast cancer samples supports the negative correlation between WBP2 expression and activated AMPK observed in vitro. RNA-seq analysis revealed the potential mechanism of WBP2 in regulating ATP production processes and preferential effect of WBP2 on metformin response in HER2+ breast cancer. This study reported a novel role of WBP2 in cancer metabolism and energetics that contributes new insights into the molecular etiology of cancer. WBP2 may be a biomarker for patient stratification, paving the way towards repurposing metformin for precision oncology.